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  • 1.
    A Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Design and Construction of a Small Ammonia Heat Pump2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In view of the fact that most of the synthetic refrigerants, in case of leakage or release, are harmful to the environment by contributing in global warming or depleting stratospheric ozone layer, many research works have been done recently to find alternative refrigerants posing no or negligible threat to the environment. Among alternative refrigerants, ammonia, a natural refrigerant with zero Global Warming Potential (GWP) and Ozone Depletion Potential (ODP), can be a sensible choice.Although ammonia has been used for many years in large industrial systems, its application in small units is rare. In this project a small heat pump with about 7 kW heating capacity at -5 °C and +40 °C evaporation and condensation temperatures is designed and built to work with ammonia as refrigerant. The heat pump is expected to produce enough heat to keep a single-family house warm in Sweden and to provide tap hot water for the house. After successful completion of this project, it is planned to install the heat pump in a house to test it throughout a heating season to study its performance in real working conditions.Since ammonia is flammable and toxic in high concentrations, the refrigerant charge is tried to be kept low in the heat pump to reduce the risk of fire or poisoning in case of unwanted release of refrigerant to the surroundings. The compact design of the heat pump helps reducing the refrigerant charge. Besides, considering the limited space normally reserved for installation of a heat pump in a house, the compact design of the heat pump is necessary.

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    B A Monfared 2010_Design and Construction of a Small Ammonia Heat Pump_MSc Thesis
  • 2.
    A Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Magnetic Refrigeration for Near Room-Temperature Applications2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Refrigeration plays a crucial role in many different sectors and consumes about 17% of the electricity produced globally. This significant energy consumption implies large share of refrigeration in primary energy consumption and other environmental impacts. In addition to the environmental impacts associated with energy consumption, the vapor-compression systems contribute in global warming due to the release of their gaseous refrigerants into the atmosphere. As an alternative technology for near room-temperature applications, magnetic refrigeration is proposed by some researchers to eliminate the release of gaseous refrigerants into the atmosphere and to reduce the energy consumption. This thesis is a compilation of a number of studies done on magnetic refrigeration for room-temperature applications.

    In the first study, the environmental impacts associated to magnetic refrigeration are looked at closely through a life cycle assessment. The life cycle assessment indicates that because of the environmental burdens related to the rare-earth materials used in magnetic refrigeration, the reduction in the environmental impacts is not guaranteed by switching to magnetic refrigeration technology. Accordingly to avoid the extra environmental impacts the magnetic refrigeration systems should use magnetic materials frugally, which requires an optimized design. In addition, operation with higher efficiency compared to vapor-compression systems is necessary to have environmental advantages, at least in some impact categories.

    A practical method to optimize the design of magnetic refrigeration systems, e.g. to have a compact design or high efficiency, is utilizing a flexible software model, with which the effect of varying different parameters on the performance of the system can be simulated. Such a software model of the magnetic refrigeration system is developed and validated in this project. In developing the model one goal is to add to the precision of the simulated results by taking more details into consideration. This goal is achieved by an innovative way of modeling the parasitic heat transfer and including the effect of the presence of magnetocaloric materials on the strength of the field created by the magnet assembly. In addition, some efforts are made to modify or correct the existing correlations to include the effect of binding agents used in some active magnetic regenerators. Validation of the developed software model is done using the experimental results obtained from the prototype existing at the Department of Energy Technology, KTH Royal Institute of Technology.

    One of the parameters that can be modified by the developed software model is the choice of the magnetocaloric materials for each layer in a layered active magnetic regenerator. Utilizing the software model for optimizing the choice of the materials for the layers reveals that materials with critical temperatures equal to the cyclic average temperature of the layers in which they are used do not necessarily result in the desired optimum performance. In addition, for maximizing different outputs of the models, such as energy efficiency or temperature lift sustained at the two ends of the regenerators, different choice of materials for the layers are needed. Therefore, in other studies seeking to improve one of the outputs of a system, the choice of the transition or critical temperatures of the materials for each layer is an additional parameter to be optimized.

    The prototype existing at the Department of Energy Technology, KTH Royal Institute of Technology, was initially designed for replacing the vapor-compression system of a professional refrigerator. However, it could not fulfil the requirements for which it was initially designed. The aforementioned developed simulation model is used to see how much the choice of the materials, size of the particles, and number of layers can enhance the performance while the operation frequency and flow rate of the heat transfer fluid are at their optimum values. In other words, in that study the room for improvement in the performance without applying major changes in the system such as the geometry of the regenerator, which implies redesigning the whole magnet assembly, is investigated. In the redesign process the effect of binding agent and the limitations associated to different properties of it is also investigated theoretically. Nevertheless, the study did not show that with keeping the geometry of the regenerators and the currently existing magnetocaloric materials the initial goals of the prototype can be achieved.

    In the next study more flexible choice of geometries and magnetocaloric materials are considered. In fact, in this study it is investigated how much the magnetocaloric materials need to be improved so that magnetic refrigeration systems can compete with vapor-compression ones in terms of performance. For the two investigated cases, the magnetic-field dependent properties of the currently existing materials are enough provided that some other issues such as low mechanical stability and inhomogeneity of the properties are solved. Nevertheless, for more demanding design criteria, such as delivering large cooling capacity over a considerable temperature span while the magnetic materials are used sparingly, the magnetic-field dependent properties need to be enhanced, as well.

    A less explored area in room-temperature magnetic refrigeration is the subject of another study included in the thesis. In this study, solid-state magnetic refrigeration systems with Peltier elements as heat switches are modeled. Since the Peltier elements consume electricity to pump heat, the modeled systems can be considered hybrid magnetocaloric-Peltier cooling systems. For such systems the detailed transient behavior of the Peltier elements together with layers of magnetocaloric materials are modeled. The mathematical model is suitable for implementation in programing languages without the need for commercial modeling platforms. The parameters affecting the performance of the modeled system are numerous, and optimization of them requires a separate study. However, the preliminary attempts on optimizing the modeled system does not give promising results. Accordingly, focusing on passive heat switches can be more beneficial.

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  • 3.
    Abacar, Armando
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Optimization of Maputo Power Plant2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The Electricidade de Moçambique, E.P. (EDM) is the power utility in Mozambique, responsible to generate, transport and distribute electricity all over the country. The company has three gas turbines installed at Maputo Power Plant. All units burn diesel oil and are used only for back up. Currently only the unit #2 is available for operation.

    The main constraint that EDM faces is the high operation costs due to diesel price. Hence the company is considering converting units #2 and #3 to burn natural gas, resource available locally. The country is currently exporting natural gas to the neighbouring Republic of South Africa.

    This MSc thesis project calculates the power output of all gas turbines when burning natural gas and optimizes the power plant capacity by proposing modifications of the current power turbine cycles to allow sustainable operation

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  • 4.
    Abadie, Brendan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Power investment outlook for Chile to 20402020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study aims to build a medium-term (2019-2040) model for the Chilean electricity generation system in the OSeMOSYS software, a linear cost optimisation model, in light of the most recent developments in government policy and targets. In 2019, the Chilean government committed to decommissioning all coal plants by 2040 at the latest, and set out a non-binding target to be carbon neutral by 2050. The carbon neutrality target could be enshrined in the climate change law, which has yet to be ratified. In this thesis, a focus was put on the upfront capital cost of the system, and the emissions attributable to Chile’s GHG Inventory (called the SNI GHG in Chile) from operating the system. Three scenarios are developed within the thesis, in line with three paths the power system may follow: a BAU scenario including current power purchase agreements, a scenario in which power purchase agreements for fossil fuels are bought out and the free market then takes over, and a non-conventional renewable energy (NCRE) scenario in which certain renewable technologies account for 68% of production in 2040. The model is validated against the results from 2019 and a broadly similar model developed in the private sector. Sensitivity analysis scenarios were conducted for the input parameters: price of natural gas, price of coal, capital cost of solar PV, capital cost of wind, capital cost of wind & solar, and the capacity factor of hydropower. The sensitivity analyses show the most sensitive input parameters are the price of natural gas and capital cost of wind with respect to the outputs of capital cost, NCRE production ratio such as the share of all solar, wind, and certain hydro technologies as a percentage of total electricity production and GHG emissions.

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  • 5. Abbas, Ghazanfar
    et al.
    Chaudhry, M. Ashraf
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Singh, Manish
    Liu, Qinghua
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Qin, Haiying
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Study of CuNiZnGdCe-Nanocomposite Anode for Low Temperature SOFC2012In: Nanoscience and Nanotechnology Letters, ISSN 1941-4900, Vol. 4, no 4, p. 389-393Article in journal (Refereed)
    Abstract [en]

    Composite electrodes of Cu0.16Ni0.27Zn0.37Ce0.16Gd0.04 (CNZGC) oxides have been successfully synthesized by solid state reaction method as anode material for low temperature solid oxide fuel cell (LTSOFC). These electrodes are characterized by XRD followed by sintering at various time periods and temperatures. Particle size of optimized composition was calculated 40-85 nm and sintered at 800 degrees C for 4 hours. Electrical conductivity of 4.14 S/cm was obtained at a temperature of 550 degrees C by the 4-prob DC method. The activation energy was calculated 4 x 10(-2) eV at 550 degrees C. Hydrogen was used as fuel and air as oxidant at anode and cathode sides respectively. I-V/I-P curves were obtained in the temperature range of 400-550 degrees C. The maximum power density was achieved for 570 mW/cm(2) at 550 degrees C.

  • 6.
    Abbas, Ghazanfar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. COMSATS Institute of Information Technology, Pakistan.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. COMSATS Institute of Information Technology, Pakistan.
    Ahmad, M. Ashfaq
    Khan, M. Ajmal
    Hussain, M. Jafar
    Ahmad, Mukhtar
    Aziz, Hammad
    Ahmad, Imran
    Batool, Rida
    Altaf, Faizah
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Electrochemical investigation of mixed metal oxide nanocomposite electrode for low temperature solid oxide fuel cell2017In: International Journal of Modern Physics B, ISSN 0217-9792, Vol. 31, no 27, article id 1750193Article in journal (Refereed)
    Abstract [en]

    Zinc-based nanostructured nickel (Ni) free metal oxide electrode material Zn-0.60/CU0.20Mn0.20 oxide (CMZO) was synthesized by solid state reaction and investigated for low temperature solid oxide fuel cell (LTSOFC) applications. The crystal structure and surface morphology of the synthesized electrode material were examined by XRD and SEM techniques respectively. The particle size of ZnO phase estimated by Scherer's equation was 31.50 nm. The maximum electrical conductivity was found to be 12.567 S/cm and 5.846 S/cm in hydrogen and air atmosphere, respectively at 600 degrees C. The activation energy of the CMZO material was also calculated from the DC conductivity data using Arrhenius plots and it was found to be 0.060 and 0.075 eV in hydrogen and air atmosphere, respectively. The CMZO electrode-based fuel cell was tested using carbonated samarium doped ceria composite (NSDC) electrolyte. The three layers 13 mm in diameter and 1 mm thickness of the symmetric fuel cell were fabricated by dry pressing. The maximum power density of 728.86 mW/cm(2) was measured at 550 degrees C.

  • 7.
    Abbas, Ghazanfar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ashfaq, M.
    Chaudhry, M. Ashraf
    Khan, Ajmal
    Ahmad, Imran
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Electrochemical study of nanostructured electrode for low-temperature solid oxide fuel cell (LTSOFC)2014In: International Journal of Energy Research, ISSN 0363-907X, E-ISSN 1099-114X, Vol. 38, no 4, p. 518-523Article in journal (Refereed)
    Abstract [en]

    Zn-based nanostructured Ba0.05Cu0.25Fe0.10Zn0.60O (BCFZ) oxide electrode material was synthesized by solid-state reaction for low-temperature solid oxide fuel cell. The cell was fabricated by sandwiching NK-CDC electrolyte between BCFZ electrodes by dry press technique, and its performance was assessed. The maximum power density of 741.87 mW-cm(-2) was achieved at 550 degrees C. The crystal structure and morphology were characterized by X-ray diffractometer (XRD) and SEM. The particle size was calculated to be 25 nm applying Scherer's formula from XRD data. Electronic conductivities were measured with the four-probe DC method under hydrogen and air atmosphere. AC Electrochemical Impedance Spectroscopy of the BCFZ oxide electrode was also measured in hydrogen atmosphere at 450 degrees C.

  • 8. Abbas, Ghazanfar
    et al.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. COMSATS Institute of Information Technology, Pakistan .
    Chaudhry, M. A.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Preparation and characterization of nanocomposite calcium doped ceria electrolyte with alkali carbonates (NK-CDC) for SOFC2010In: ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology, FUELCELL 2010, ASME Press, 2010, p. 427-432Conference paper (Refereed)
    Abstract [en]

    The entire world's challenge is to find out the renewable energy sources due to rapid depletion of fossil fuels because of their high consumption. Solid Oxide Fuel Cells (SOFCs) are believed to be the best alternative source which converts chemical energy into electricity without combustion. Nanostructured study is required to develop highly ionic conductive electrolyte for SOFCs. In this work, the calcium doped ceria (Ce0.8Ca0.2O 1.9) coated with 20% molar ratio of two alkali carbonates (CDC-M: MCO3, where M= Na and K) electrolyte was prepared by co-precipitation method in this study. Ni based electrode was used to fabricate the cell by dry pressing technique. The crystal structure and surface morphology was characterized by X-Ray Diffractometer (XRD), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM). The particle size was calculated in the range of 10-20nm by Scherrer's formula and compared with SEM and TEM results. The ionic conductivity was measured by using AC Electrochemical Impedance Spectroscopy (EIS) method. The activation energy was also evaluated. The performance of the cell was measured 0.567W/cm2 at temperature 550°C with hydrogen as a fuel.

  • 9.
    Abbas, Ghazanfar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Chaudhry, M. Ashraf
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Preparation and Characterization of Nanocomposite Calcium Doped Ceria Electrolyte With Alkali Carbonates (NK-CDC) for SOFC2011In: Journal of Fuel Cell Science and Technology, ISSN 1550-624X, Vol. 8, no 4, p. 041013-Article in journal (Refereed)
    Abstract [en]

    The entire world's challenge is to find out the renewable energy sources due to rapid depletion of fossil fuels because of their high consumption. Solid oxide fuel cells (SOFCs) are believed to be the best alternative source, which converts chemical energy into electricity without combustion. Nanostructure study is required to develop highly ionic conductive electrolytes for SOFCs. In this work, the calcium doped ceria (Ce0.8Ca0.2O1.9) coated with 20% molar ratio of two alkali carbonates (CDC-M: MCO3, where M = Na and K) electrolyte was prepared by coprecipitation method. Ni based electrode was used to fabricate the cell by dry pressing technique. The crystal structure and surface morphology were characterized by an X-ray diffractometer, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (TEM). The particle size was calculated in the range 10-20 nm by Scherer's formula and compared with SEM and TEM results. The ionic conductivity was measured by using ac electrochemical impedance spectroscopy method. The activation energy was also evaluated. The performance of the cell was measured 0.567 W/cm(2) at temperature 550 degrees C with hydrogen as a fuel.

  • 10.
    Abbas, Ghazanfar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. COMSATS Institute of Information Technology, Pakistan.
    Raza, Rizwan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. COMSATS Institute of Information Technology, Pakistan.
    Khan, M. Ajmal
    Ahmad, Imran
    Chaudhry, M. Ashraf
    Sherazi, Tauqir A.
    Mohsin, Munazza
    Ahmad, Mukhtar
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Synthesize and characterization of nanocomposite anodes for low temperature solid oxide fuel cell2015In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 40, no 1, p. 891-897Article in journal (Refereed)
    Abstract [en]

    Solid oxide fuel cells have much capability to become an economical alternative energy conversion technology having appropriate materials that can be operated at comparatively low temperature in the range of 400-600 degrees C. The nano-scale engineering has been incorporated to improve the catalytic activity of anode materials for solid oxide fuel cells. Nanostructured Al0.10NixZn0.90-xO oxides were prepared by solid state reaction, which were then mixed with the prepared Gadolinium doped Ceria GDC electrolyte. The crystal structure and surface morphology were characterized by XRD and SEM. The particle size was evaluated by XRD data and found in the range of 20-50 nm, which was then ensured by SEM pictures. The pellets of 13 mm diameter were pressed by dry press technique and electrical conductivities (DC and AC) were determined by four probe techniques and the values have been found to be 10.84 and 4.88 S/cm, respectively at hydrogen atmosphere in the temperature range of 300-600 degrees C. The Electrochemical Impedance Spectroscopy (EIS) analysis exhibits the pure electronic behavior at hydrogen atmosphere. The maximum power density of ANZ-GDC composite anode based solid oxide fuel cell has been achieved 705 mW/cm(2) at 550 degrees C.

  • 11.
    Abbas Sohani, Amir
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Waste heat recovery from SSAB’s Steel plant in Oxelösund using a Heat Pump2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This project was focused on waste heat potentials in the iron and steel industry. High temperature industrial heat pumps (HTIHP) for medium temperature, waste heat recovery were modelled. The SSAB iron and steel plant in Oxelösund was used as an example. The iron and steel industry in Sweden is a large energy consumer, together with the pulp and paper industry. There is also a large potential for waste heat recovery in the steel industry. This is already done in for instance Luleå [1].

    Iron and steel production methods and waste heat recovery in the world, especially in the US and Sweden, have been reviewed in a literature study. Current methods and potentials of waste heat recovery in the iron and steel industry of Sweden were especially reviewed. The SSAB iron and steel plant in Oxelösund has been planning for decades, not only to heat the city of Oxelösund as today, but also to expand to the nearby city of Nyköping 12 km away [2].

    Typically the maximum temperature entering the district heating network of Nyköping would be 110 °C on the coldest day. The heat pump output from a waste heat recovery plant generally does not have to reach such a high temperature. However, 80 °C maximum forward temperature would surely be enough to use recovered heat all the time. Even a lower temperature like 75 °C would probably be sufficient – as only a few heat exchangers in individual houses then would have to be changed, to accept that lower temperature. The extra degrees between 80 °C (75 °C) and 110 °C can be taken with heat from e.g. existing biofuel furnaces locally in Nyköping.

    Using heat pumps in this context is not self-evident. Generally the heat flows from a steel plant are available at such high temperatures that no heat pump ideally is needed. However collecting the heat at those high temperatures, in an old plant, can get very expensive and interfere with the processes. Therefore the study is focusing on medium temperature (30 – 40 °C) waste heat potentials implementing High Temperature Industrial Heat Pumps (HTIHP). The heat is now being rejected by a cooling tower. That way, easily available waste heat, can cover 50% of the total need from Nyköping. Assuming a COP of around 5 and adding the electricity needed to run the heat pump, the total will result in totally 62% of the energy need for Nyköping.

    The Oxelösund Plant is just an example and the study is really focusing on HITIHP for this and similar purposes. Appropriate components and refrigerants have been evaluated and the general layouts of proper HITIHP types are suggested. A literature study on the best choice of refrigerant in the high temperature heat pump has been done.

    A two stage high temperature heat pump has been modeled and simulated using the available heat sink capacity and temperature, together with the demanded temperatures in the district heating network. The simulation has mainly been performed using the EES software. R245fa is e.g. a good candidate as refrigerant in a second stage (high temperature stage) of a two stage cascade heat pump. With R245fa even higher temperatures than 90°C to the district heating can be achieved. Earlier, R134a would be used in this application but R245fa has e.g. a lower GWP (around 1000 instead of around 1300) [3]. Many different refrigerants have been simulated in the first of two stages of a smaller screw compressor driven cascade heat pump. Also a two stage turbo compressor throttling heat pump, using a flash tank, has been simulated, showing a good performance. In the latter case both, refrigerants R1234ze(z) and R245fa have good characteristics but R1234ze(z) has a much lower GWP.

    All COPs, compressor energy consumptions, condenser pressures, pressure ratios were compared. R245fa-R245fa and R600-R245fa were studied in the two stage cascade systems. They came out with the best results. R717-R245fa also showed a very good performance, but had other limitations. In two stage flash tank systems, R1234ze(z) had the best performance (COP) and no temperature loss between the two stages (like in the cascade systems). If SSAB Oxelösund’s blast furnace and cooling tower water would not be available, the turbo heat pump can produce the demanded heat, using sea water as heat source instead.

    The CO2 emission reduction is very hard to calculate. That will be more of a political conviction problem. A very rough cost estimation of the projects investment cost is also done. It will cost between 420 and 450 MSEK. This cost estimation includes a heat pump and 12 km pipe to Nyköping. The cost of heat delivered in Nyköping will vary between 0,2 and 0,65 SEK/kWh when the cost of electricity is varied between 0,5 and 2 SEK/kWh (include taxes). In that price the capital costs for the heat pump and pipe is included. The high cost level 0, 65 SEK/kWh assumes that sea water is used as heat source.

    A cooling towers waste heat can be recovered, using a high temperature heat pump. This heat can thus be delivered from Oxelösund to Nyköping. The economic viability of this idea is only superficially covered. Factors like if the old furnace in Nyköping needs upgrading, which could be postponed, could possibly tip the project into go. Maitenance cost, of the existing cooling tower, is another such factor, initiating the project. A waste heat pipe between Oxelösund and Nyköping has been studied at least since the middle of the 1970:s by e.g. Lars Åke Cronholm [4]. Could it be the right time now?

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  • 12.
    Abbassi, Behrang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Hultling, Johannes
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Smarta Elnät – Modell och Marknad2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Smart Grid technology has during the last decade been established as a way to create a greater flexibility on the electricity grid that will be needed as the development moves towards an increased share of renewable primary energy sources in the electricity production. One part of the Smart Grid technology is the ability to shift loads in time, to adapt to either price or emissions, known as Demand Response. This project, which was conducted at KTH in collaboration with the consulting corporation Capgemini, examines the economic, environmental and social aspects of the Demand Response technology.

     

    In the project, three household products are used in a model that derives the potential savings in costs and emissions of CO2e. The results show that the actual savings measured in SEK are small, but that the savings measured in percent can be as high as 20 percent. Reduction of CO2e emissions is slightly lower. Furthermore, the study shows that the savings increase as more flexibility is given to the model and as the fluctuations of price increases. A scenario that includes more intermittent electricity production, and end users ready to commit to the technology,  is therefore vital for the success of the Demand Response technology. The results also show that an optimization cannot be done in such way that both minimize costs and CO2e emissions simultaneously.

     

    A discussion on the strategic opportunities for Capgemini shows that focus should be on collecting, interpreting and compiling the large amounts of data that the technology will result in. There are also possibilities in peripheral services tied together with the Smart Grid technology, such as the development of a charging infrastructure for electric cars.

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  • 13.
    Abbes, Yacine
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Educational studies in heat and power technology: how students learn with multimedia tools and problem-based learning2005Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    Higher education is undergoing continuous changes and new learning tools and methods are implemented. Researchers in education do not always agree upon the effectiveness of some of the methods introduced into engineering education. The present thesis consists of two case studies on educational methods introduced at the Department of Energy Technology, at Royal Institute of Technology (KTH), Sweden. The qualitative research methodology has been used in case one and a combination of qualitative and quantitative methodology has been used in the second case. The sources of evidences consisted of: unstructured interviews, analysis of video recording, questionnaires, and analysis of a variety of documents. In the first case, an educational program in heat and power technology was analysed. The second case consists in an in-depth study of group dynamics in a Problem –Based Learning course. These studies showed that the learning approach adopted by students depends strongly on the way they view the particular learning tool or method. The first case study revealed the existence of two types of learners. Surfacelearners follow the structure suggested by the designers of the multimedia program. This category of learners focuses only on the material available in the program. Deep-learners go beyond the information and the structure suggested in the program and combine different learning tools in their learning. These students do not follow the structure of the tutorials’ of the multimedia program. This study showed that students who had a strong view how to learn with a multimedia program or a learning method benefited less from the learning tools available. Students with weak views on how to learn from educational program or leaning tool benefit less from the presentation and engage in more surface learning. Self-motivated learners use the multimedia presentation in novel ways and crosscheck the information given with other material. The second study showed that students have unclear and weak views on how to learn with student-directed Problem- Based Learning model. Four types of learners were identified in Problem-Based Learning project: Leaders, Key Actors, Common Students and Social Loafers. Leaders and Key Actors are self-motivated individuals and participate most in the projects. Students who viewed themselves or were viewed as leaders were held responsible to take most of the decisions and students expected them to work more than the average student. Students who viewed themselves as common team members expected a lower workload than leaders’. Key Actors are self-motivated students who do not view themselves as separate from other group members but who participate more than others. Leaders learned more group and social processes, that they did not fully take part in, while common students learned more from the project management aspects that they did not take part in. The study also found that Problem-Based Learning groups can become very cohesive, and can develop distorted views on how to learn with Problem-Based Learning, and un-common group dynamics phenomena such as groupthink can occur in Problem-Based Learning setting.

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  • 14.
    Abbott, Michele
    et al.
    RAND Corp, Pardee RAND Grad Sch, Santa Monica, CA 90406 USA..
    Bazilian, Morgan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Columbia Univ, Swedish Royal Inst Technol, Ctr Global Energy Policy, New York, NY 10027 USA..
    Egel, Daniel
    RAND Corp, Santa Monica, CA 90406 USA..
    Willis, Henry H.
    RAND Corp, Santa Monica, CA 90406 USA..
    Examining the food-energy-water and conflict nexus2017In: Current Opinion in Chemical Engineering, E-ISSN 2211-3398, Vol. 18, p. 55-60Article, review/survey (Refereed)
    Abstract [en]

    There is growing evidence of a strong linkage or 'nexus' between conflict - both domestic and international - and food, energy, and water (FEW) resources and services. This article demonstrates a positive, significant correlation between two measures, FEW security and political stability, and reviews the evidence for how each of these three types of resource insecurities affects political and social stability. We describe what is known about the FEW-conflict nexus itself, note that remaining knowledge gaps include evidence on developing governance structures and preparing for climate change, and examine the types of policies that countries and international donors might take to help mitigate the role that FEW can play in affecting stability.

  • 15.
    Abdi, Amir
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Analysis of heat recovery in supermarket refrigeration system using carbon dioxide as refrigerant2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this study is to investigate the heat recovery potential in supermarket refrigeration systems using CO2 as refrigerants. The theoretical control strategy to recover heating demand from refrigeration system is explained thoroughly and the heat recovery process from two existing supermarket using CO2 booster units is analyzed and evaluated. The measured data of refrigeration systems is obtained through Iwmac interface, processed using Excel and Refprop. The aim is to see what control strategy is used in these systems and weather it matches the theoretical one and at what level heat is recovered from the system.

    Besides, a simulation model is made by EES to investigate the potential of higher rate of heat recovery in the supermarkets. The simulation results are compared with field measurement and validated by measured values. Then, the ability of refrigeration system to do heat recovery at quite high rates for covering the total heating demand without using parallel heating system is evaluated and efficiency of the system is calculated. At the next step the heat recovery potential at other refrigeration solutions such as R404A conventional and CO2-ammonia cascade systems are studied and the results are compared to booster units. Finally, the potential for selling heat from the refrigeration system in supermarket to district heating network is investigated. Two different scenarios are made for such purpose and the results are evaluated.

    The heat recovery control strategy of existing supermarkets does not match the theoretical strategy and regarding the capacity of the system, heat is recovered to low extent. Simulation shows that heat can be recovered to higher extent at quite high heating COP of 3-5. Additionally the other heat recovery solutions for R404A conventional and CO2-ammonia cascade systems are found to be competitive to CO2 booster system.  The analysis of selling heat to district heating network shows that CO2 booster system is capable of covering the demand at reasonable heating COP as the first priority and selling the rest to district heating network at heating COP of 2 as second priority.  

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  • 16.
    Abdi, Amir
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Heat Transfer Enhancement of Latent Thermal Energy Storage in Rectangular Components2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Latent Thermal Energy Storage (LTES) is an interesting choice to storethermal energy in a sustainable energy system. The primary benefit of LTESis the relatively high latent heat of fusion of the materials, known as PhaseChange Materials (PCM), used in such a system as the storage medium.However, as the thermal conductivity of PCMs is often very low, there is aneed to enhance the rate of heat transfer within the charging/dischargingprocess and to improve the thermal performance of the LTES systems.This thesis addresses the enhancing effect of extending heat transfer area inrectangular LTES enclosures. A key contribution of this thesis is acomprehensive visualization of the phase change processes for an organicPCM, including solidification and melting, constrained as well asunconstrained, known as Close-Contact Melting (CCM), in a cavity with andwithout fins. Observations have been carried out for fins of different lengthsand numbers with a varying angle of inclination, and a comprehensive analysisin terms of phase change time and thermal power is conducted.The observations show fins are more influential in solidification than inmelting, reducing the solidification time by 80% and increasing the meanpower by 395%, at a cost of 10% loss in the extracted energy. In contrast, inmelting, fins have a modest effect in enhancing the process. The relativeenhancement effect of fin is higher in constrained melting than inunconstrained melting. In a case with maximum enhancement, a reduction by52% in the constrained melting time and a relative enhancement in the meanpower by 90% is achieved at a cost of 9% loss in the stored energy. As thevolume fraction of fin increases, the discrepancies in melting time betweenthe constrained and unconstrained melting diminishes.A numerical model for solidification and constrained melting is validatedbased on the experiments, and a more inclusive sensitivity analysis of finparameters is performed. The enhancing effect of different parameters on thephase change time and the thermal power is analyzed and the relatively moreeffective measures are identified. Analyzing the simulation data withdimensionless parameters for a cavity oriented horizontally and enhancedwith vertical fins, overall dimensionless groups for solidification and constrained melting have been obtained. The dimensionless groupscontribute in general to achieving a better understanding of fins parametersand to facilitating the LTES designs.In addition, this thesis investigates a novel idea of extending the surface areavia incorporating mini-channels into LTES enclosures, used as passages forair as a low thermal conductive Heat Transfer Fluid (HTF). The mini-scaleinternal hydraulic diameter of the mini-channels and their high external areato-volume ratios make a potential for dual enhancement on both the PCMside and the HTF side. An existing design and a conceptual one with thepossibility of adding fins on the PCM side, capable of being manufactured viaproduction methods of extrusion and Additive Manufacturing (AM),respectively, have been simulated and studied.The two mini-channel types provide considerable enhancements in the rateof heat transfer for a PCM heat exchanger working with air. The degree ofenhancement increases as the air flow rate increases, at the cost of anincreasingly higher pressure drop. Regarding this, increasing the number ofchannels is identified as a more effective enhancing measure than adding finsto the PCM side. In addition, the conceptual design with a higher internalhydraulic diameter and considerably a higher aspect ratio has a lower pressuredrop than the existing design, charging/discharging the thermal energy at asimilar rate but with a lower fan power. More optimized designs withminimization of pressure drop, contribute to paving the way in facilitation ofthe utilization of the enhanced air-PCM heat exchanger in variousapplications.

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  • 17.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Numerical Investigation of Latent Thermal Storage in a Compact Heat Exchanger Using Mini-Channels2021In: Applied Sciences, E-ISSN 2076-3417, Vol. 11, no 13, p. 5985-, article id 5985Article in journal (Refereed)
    Abstract [en]

    This paper aims to numerically investigate the thermal enhancement of a latent thermal energy storage component with mini-channels as air passages. The investigated channels in two sizes of internal air passages (channel-1 with d(h) = 1.6 mm and channel-2 with d(h) = 2.3 mm) are oriented vertically in a cuboid of 0.15 x 0.15 x 0.1 m(3) with RT22 as the PCM located in the shell. The phase change is simulated with a fixed inlet temperature of air, using ANSYS Fluent 19.5, with a varying number of channels and a ranging air flow rate entering the component. The results show that the phase change power of the LTES improves with by increasing the number of channels at the cost of a decrease in the storage capacity. Given a constant air flow rate, the increase in the heat transfer surface area of the increased number of channels dominates the heat transfer coefficient, thus increasing the mean heat transfer rate (UA). A comparison of the channels shows that the thermal performance depends largely on the area to volume ratio of the channels. The channel type two (channel-2) with a slightly higher area to volume ratio has a slightly higher charging/discharging power, as compared to channel type one (channel-1), at a similar PCM packing factor. Adding fins to channel-2, doubling the surface area, improves the mean UA values by 15-31% for the studied cases. The variation in the total air flow rate from 7 to 24 L/s is found to have a considerable influence, reducing the melting time by 41-53% and increasing the mean UA values within melting by 19-52% for a packing factor range of 77.4-86.8%. With the increase in the air flow rate, channel type two is found to have considerably lower pressure drops than channel type one, which can be attributed to its higher internal hydraulic diameter, making it superior in terms of achieving a relatively similar charging/discharging power in exchange for significantly lower fan power. Such designs can further be optimized in terms of pressure drop in future work, which should also include an experimental evaluation.

  • 18.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    State of the art in hydrogen liquefaction2020In: Proceedings of the ISES Solar World Congress 2019 and IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2019, International Solar Energy Society , 2020, p. 1311-1320Conference paper (Refereed)
    Abstract [en]

    Hydrogen is a potential option to replace fossil fuels considering the increasing demand of energy applications. It is naturally abundant and is regarded as a suitable energy carrier. There has been extensive research to improve the efficiency of storing hydrogen with different methods, including gas compression, liquefaction and sorption in metal hydrides or carbon nanotubes. A comparison of the storage methods shows that liquefaction of hydrogen is more beneficial than compression of hydrogen in terms of higher volumetric capacity, and it is more technologically mature than sorption technologies. This makes it more plausible for long distance distribution. On the other hand, the obstacles in full exploitation of the method are low energy efficiency of the liquefaction process and associated high cost. The recent research has been focusing on increasing the energy efficiency of the storage process. This paper provides, with regard to the conventional methods, a state of the art review of the novel and modified liquefaction process and the latest developments in increasing the efficiency of the energy intensive process. Furthermore, the developments in combining the hydrogen liquefaction plants with renewable energy sources are covered and reviewed. Finally, the ongoing development of hydrogen liquefaction is highlighted.

  • 19.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Ignatowicz, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Gunasekara, Saman Nimali
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of thermo-physical properties of n-octadecane and n-eicosane2020In: International Journal of Heat and Mass Transfer, ISSN 0017-9310, E-ISSN 1879-2189, Vol. 161, article id 120285Article in journal (Refereed)
    Abstract [en]

    Reliable knowledge of phase change materials (PCM) thermo-physical properties is essential to model and design latent thermal energy storage (LTES) systems. This study aims to conduct a methodological measurement of thermo-physical properties, including latent enthalpy, isobaric specific heat, thermal conductivity and dynamic viscosity, of two n-alkanes, n-octadecane and n-eicosane. The enthalpy and isobaric specific heat of the materials are measured via differential scanning calorimetry (DSC) technique, using a pDSC evo7 from Setaram Instrumentation with a sample mass of 628.4 mg. The influence of the scanning rates, varying from 0.5 K/min to 0.025 K/min, in dynamic continuous mode within temperature range of 10-65 degrees C is investigated. The thermal conductivity and the dynamic viscosity are measured via Hot Disk TPS-2500S instrument and Brookfield rotational viscometer, respectively, up to 70 degrees C. The thermal analysis results via the pDSC show that the isothermal condition can be approached at a very low scanning rate, however at the cost of a higher noise level. A trade-off is observed for n-octadecane, achieving the lowest deviation of 0.7% in latent heat measurement at 0.05 K/min, as compared to the American Petroleum Table values. For n-eicosane, the lowest deviation of 1.2% is seen at the lowest scanning rate of 0.025 K/min. The thermal conductivity measured values show good agreements with a number of documented literature studies in the solid phase, within deviations of 2%. Larger deviations of 5-16% are found for the measurement in the liquid phase. The viscosity values also show a good agreement with the literature values with maximum deviations of 2.9% and 6.3%, with respect to the values of American Petroleum Tables, for n-octadecane and n-eicosane, respectively. The good agreements achieved in measurements establish the reliable thermo-physical properties contributing to the future simulations and designs. 

  • 20.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Numerical investigation of melting in a cavity with vertically oriented fins2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 235, p. 1027-1040Article in journal (Refereed)
    Abstract [en]

    This paper investigates the effect of vertical fins, as an enhancement technique, on the heat transfer rate and energy density of a latent heat thermal energy storage system. This contributes with knowledge on the interaction of heat transfer surface with the storage material for optimizing storage capacity (energy) and power (heat transfer rate). For the assessment, numerical modeling is employed to study the melting process in a two-dimensional rectangular cavity. The cavity is considered heated isothermally from the bottom with surface temperatures of 55 degrees C, 60 degrees C or 70 degrees C, while the other surfaces are insulated from the surrounding. Aluminum and lauric acid are considered as fin/enclosure material and phase change material, respectively. Vertical fins attached to the bottom surface are employed to enhance the charging rate, and a parametric study is carried out by varying the fin length and number of fins. Thus, a broad range of data is provided to analyze the influence of fin configurations on contributing natural convection patterns, as well as the effects on melting time, enhanced heat transfer rate and accumulated energy. The results show that in addition to increasing the heat transfer surface area, the installation of vertically oriented fins does not suppress the natural convection mechanism. This is as opposed to horizontal fins which in previous studies have shown tendencies to reduce the impact of natural convection. This paper also highlights how using longer fins offers a higher rate of heat transfer and a better overall heat transfer coefficient rather than increasing the number of fins. Also, fins do not only enhance the heat transfer performance in the corresponding melting time, but also maintain similar total amount of stored energy as compared to the no-fin case. This paper discusses how this is the result of the enhanced heat transfer allowing a larger portion of sensible heat to be recovered. For example, in the case with long fins, the relative mean power enhancement is about 200% with merely 6% capacity reduction, even though the amount of PCM in the cavity has been reduced by 12% as compared to the no-fin case. Although the basis for these results stems from the principles of thermodynamics, this paper is bringing it forward with design consideration. This is because despite its importance for making appropriate comparisons among heat transfer enhancement techniques in latent heat thermal energy storage, it has not been previously discussed in the literature. In the end, the aim is to accomplish robust storage systems in terms of power and energy density.

  • 21.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Rastan, Hamidreza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Experimental comparative analysis of close-contact and constrained melting of n-eicosane in a finned rectangular cavity2023In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 219, article id 119677Article in journal (Refereed)
    Abstract [en]

    The present study demonstrates and visualizes the two modes of constrained melting and close-contact melting in a rectangular cavity enhanced with fins. Three configurations of fin with different lengths and numbers are tested in different horizontal, inclined, and vertical orientations. N-eicosane is used as the phase change material, and the experiments are performed with water as the heat transfer fluid at the inlet conditions of 50 degrees C, 55 degrees C, and 60 degrees C. In general, the close-contact melting time is shorter by 42-50%, compared to the convection dominated constrained melting in the unenhanced cavity without fins. By using fins to enhance the process, the melting time is reduced by 49% and 35% in the constrained and the close-contact modes, respectively, compared to the unfinned cavity in each mode. The thermal performance is observed to be superior in the horizontal and the inclined orientations. In these orientations, the buoyancy-driven structures are not blocked by fins in the con-strained mode. In the close-contact mode, the solid specimens attain more consistent contact with the base of the cavity and with the extended heat transfer area at the inclined and horizontal conditions. In the vertical orientation, the asymmetrical melting by the fins results in a rotational movement of the solid PCM and close -contact perturbations. The variations in the number of fins are found to have minor effects on the overall close-contact-induced melting. On the other hand, increasing the length of the fins is a more promising measure, providing consistent and prolonged contact.

  • 22.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Karampour, Mazyar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Heat recovery investigation of a supermarket refrigeration system using carbon dioxide as refrigerant2014In: 11th IIR Gustav Lorentzen Conference on Natural Refrigerants: Natural Refrigerants and Environmental Protection, GL 2014, International Institute of Refrigeration, 2014, p. 277-285Conference paper (Refereed)
    Abstract [en]

    This study investigates the heat reclaim of trans-critical CO2-booster refrigeration unit in a supermarket in Sweden. The aim is to compare the control strategy for heat recovery in real supermarket installation to the optimum control strategy.

    The optimum control strategy based on theoretical analysis is explained. By analyzing field measurement of a supermarket, heat recovery in the refrigeration system is studied and compared to the optimum case. To investigate the potential of higher heat recovery rate, a computer model is developed based on the optimum control strategy.  The model is also used to calculate the boundary conditions at which the system should run for highest COP.

    The results show that heat can be recovered at heating COP of 3-4.5. The theoretical analysis shows that the amount of heat that can be recovered from the refrigeration system is about 1.3 times (130 %) the cooling demand in the system. However the analysis of the field measurements shows that only between 30-60 % of the available heat to be recovered is utilized, the rest is released to outdoors. The analysis in this study shows that there is a potential to recover much more heat from the refrigeration system at relatively high heating COP compared to heat pump.

  • 23.
    Abdi, Amir
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Shahrooz, Mina
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Chiu, Justin NingWei
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental investigation of solidification and melting in a vertically finned cavity2021In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 198, article id 117459Article in journal (Refereed)
    Abstract [en]

    Extending the heat transfer area is a simple technique to improve the thermal performance of phase change materials with low thermal conductivity. However, as the governing mechanisms differ in solidification and melting, fins can affect the processes in different ways. This demands assessment of fin enhancement in a combined analysis on both solidification and melting, often neglected in literature. This paper presents visual-izations of solidification and melting of n-eicosane in a rectangular cavity and experimentally investigates the enhancing effect of vertical fins with varying number and length. Experiments were conducted at water inlet temperature ranges of 15-25 degrees C and 50-60 degrees C for the solidification and melting processes, respectively. The results show that the vertical fins can be more influential in solidification rather than in melting with similar losses in the storage capacity. In the solidification process, as natural convection is absent, the mean power is enhanced by a maximum of 395% with a 10% loss in the storage capacity, as compared to the benchmark. In the melting case, the mean power is increased by a maximum of 90% with a 9% loss in the storage capacity. Although increasing the surface area with vertical fins contributes to development of convective structures, it makes a modest enhancement. In overall, increasing the fin volume fraction, in exchange for the loss in the storage capacity, enhances the solidification significantly while it has relatively low enhancement effect in melting. At the end, the performed experiments could be helpful for validation of future simulation tools with complex features, particularly solidification models lacking in literature.

  • 24.
    Abdlla, Hamodi
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Eshete, Helen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Distributed generation for waste heat utilisation and industrial symbiosis at Zigrid AB.: A case study on the Alby hydrogen project in Ånge, Sweden2023Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis investigates the potential utilisation of Zigrid’s distributed power modules for waste heat utilisation and electricity production within an industrial cluster. The study examines generated waste heat from a hydrogen production plant with a PEM electrolyser and Zigrid’s innovative energy generation capabilities. Furthermore, the study investigates changes in the value chain within the industrial cluster when integrating Zigrid’s power modules as a cooling technique and thereby replacing cooling towers. This integration offers various potential avenues for the excess waste heat, such as electricity production and district heating.

    An in-depth economic evaluation was performed, weighing the cost-effectiveness of Zigrid's power modules against traditional cooling towers. The economic assessment includes the Levelized Cost of Electricity (LCOE) for locally produced electricity and showcase the potential savings by reducing dependence on the grid. Furthermore, the study also highlights the potential benefits of harnessing Sweden's waste heat, forecasting Zigrid's prospective contribution to local electricity generation and substantial economic efficiencies. 

    The study's findings underscore the viability of Zigrid's power units in increasing local electricity generation, curbing emissions, enhancing grid stability, and fostering sustainable practices within industrial clusters.

  • 25.
    ABDOUSSI, Sarah
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Project Finance in the Energy FieldCase Study: A wind Power Project in a Moroccan-like environment2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Companies, governments and NGOs are involved in designing and planning the future energy landscape of countries. Engineers and scientists contribute highly to this planning through bringing innovative, efficient and reliable technical solutions. Their know-how is used during the project development, the EPC (Engineering, Procurement and Construction) phase as well as during the Operation and Maintenance stage.

    However, a successful energy plan depends on many other parameters such as the legal side, the political background of the country, the financing methods, the funding, the environmental aspects and the social acceptance.

    This Master Thesis Project focuses on the financing side of energy projects, which is a key point to properly manage competitive and viable projects. The strong link between the financing and the political background will be shortly commented throughout the report.

    In the first part of the report, the focus is put on the Project Finance. All along the report, the theoretical concepts will be illustrated with examples taken from the EDF EN projects, mainly in the Middle East and North African area. The second part deals with the risks associated to power projects. Commercial and political risks are listed and the main mitigation tools are explained. The third part of the report is dedicated to basic business models for energy projects. A simplified economical and financial model is described in detail and run for a wind farm project in a Moroccan-like environment. A sensitivity analysis (fourth part) concludes the report through analyzing: - the impact of technological choices on the internal return on investment will be studied - the impact of the financial parameters on the project structure.

  • 26.
    Abeywardana, Asela M.A.J.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Solar-Biomass hybrid system for process heat supply in medium scale hotels in Sri Lanka2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study aimed at evaluating and demonstrating the feasibility of using Concentrated Solar Thermal technology combined with biomass energy technology as a hybrid renewable energy system to supply the process heat requirements in small scale industries in Sri Lanka. Particularly, the focus was to apply the concept to the expanding hotel industry, for covering the thermal energy demand of a medium scale hotel.

    Solar modules utilize the rooftop area of the building to a valuable application. Linear Fresnel type of solar concentrator is selected considering the requirement of the application and the simplicity of fabrication and installation compared to other technologies. Subsequently, a wood-fired boiler is deployed as the steam generator as well as the balancing power source to recover the effects due to the seasonal variations in solar energy. Bioenergy, so far being the largest primary energy supply in the country, has a good potential for further growth in industrial applications like small hotels. 

    When a hotel with about 200-guests capacity and annual average occupancy of 65% is considered, the total annual CO2 saving is accounted as 207 tons compared with an entirely fossil fuel (diesel) fired boiler system. The annual operational cost saving is around $ 40,000 and the simple payback period is within 3-4 years. The proposed hybrid system can generate additional 26 employment opportunities in the proximity of the site location area.  

    This solar-biomass hybrid concept mitigates the weaknesses associated with these renewable technologies when employed separately. The system has been designed in such a way that the total heat demand of hot water and process steam supply is managed by renewable energy alone. It is thus a self-sustainable, non-conventional, renewable energy system. This concept can be stretched to other critical medium temperature applications like for example absorption refrigeration. The system is applicable to many other industries in the country where space requirement is available, solar irradiance is rich and a solid biomass supply is assured.

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  • 27.
    Abeywecra, Ruchira
    et al.
    OUSL, Dept Mech Engn, Nugegoda, Sri Lanka..
    Scnanavakc, Nihal S.
    OUSL, Dept Mech Engn, Nugegoda, Sri Lanka..
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Fransson, Torsten H.
    EIT InnoEnergy, Eindhoven, Netherlands..
    A Remote Mode High Quality International Master Degree Program in Environomical Pathways for Sustainable Energy Systems (SELECT) -Pilot Program Experiences During First Year of Studies2018In: PROCEEDINGS OF 2018 IEEE GLOBAL ENGINEERING EDUCATION CONFERENCE (EDUCON) - EMERGING TRENDS AND CHALLENGES OF ENGINEERING EDUCATION, IEEE , 2018, p. 276-284Conference paper (Refereed)
    Abstract [en]

    Remote mode study programs at master degree level are becoming more popular than undergraduate level programs. Students after graduation with Bachelors degree very often are employed and the most appropriate mode for them to pursue higher studies is the remote mode. Postgraduate programs with one or two year duration mostly focus on specific areas of research based industrial application. Traditional remote education is thought to be more centered on web based on-line programs with a little opportunity for teacher student interaction and interaction with peers. In such programs motivation for studies has been a problem and as a result many students drop off and also those remain in the program for prolonged periods do not show good performance. One of the reasons for failures of students in remote studies is the isolation leading to discouragement for the completion studies. A remote mode Master Degree Program in Environomical Pathways for Sustainable Energy Systems (MSc-SELECT), consisting of a number of innovative features aimed at improved student engagement, motivation, exposure to experiences in multi-national setting and team work, was developed and implemented by the Master School of the EIT-InnoEnergy, as a pilot project. The program was offered, collaboratively and simultaneously to students in three locations, Royal Institute of Technology in Sweden, Universitat Politecnica de Catalunya in Spain and the Open University of Sri Lanka. The students in Sweden and Spain each followed 50% of the courses on-campus and 50% in remote mode depending upon the university they registered with. The students in Sri Lanka followed the entire 1st year fully remotely. All the students (from KTH, OUSL and UPC) will spend the 2nd year on-campus at another university in the consortium. This paper discusses, from the perspective of the fully remote site, the remote program with its innovative aspects, student performance and experience together with future tasks for making the program viable and beneficial to all partner countries.

  • 28. Abeyweera, Ruchira
    et al.
    Senanayake, Nihal S.
    Senaratne, Chamindie
    Jayasuriya, Jeevan
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. EIT InnoEnergy, Sweden.
    Fransson, Torsten H.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology. EIT InnoEnergy, Sweden.
    Capacity Building Through a Web Based Master Degree Programme in Sustainable Energy Engineering2017In: PROCEEDINGS OF 2017 IEEE GLOBAL ENGINEERING EDUCATION CONFERENCE (EDUCON2017), IEEE, 2017, p. 800-805Conference paper (Refereed)
    Abstract [en]

    Open Distance Learning is gaining popularity as a successful alternative for on-campus higher education especially with the emergence of web based platforms which enable the online delivery of courses worldwide. This emerging educational pedagogy can successfully be employed as means of capacity building of the people living in the less fortunate parts of the world where higher education especially at master level are scarce. This paper presents a two-year collaborative master study programme in sustainable energy engineering offered in synchronous with an on-campus study programme conducted by the KTH Royal Institute of Technology of Sweden, to students of Sri Lanka, which was facilitated by the Open University of Sri Lanka. The paper describes the need of such a programme, the format of course delivery and assessment thereof, plus the benefits gained. This programme has produced 72 post graduates in Sri Lanka alone and more than 200 distant postgraduates worldwide in the field of sustainable energy engineering during last 10 years period. In terms of capacity building in the energy sector in Sri Lanka this is considered a great achievement. The experience gained by the local staff in the role of local facilitators who engaged in some of the academic related activities such as evaluation of students' presentation and co-supervision of thesis projects have been greatly appreciated as being additional benefits to the staff in terms of their own academic development and capacity building. Finally, conclusions are made on how remote programmes of study could successfully be delivered to places where such know-how is scarce by adapting appropriate technologies in training personnel at postgraduate level to meet the needs of the industry.

  • 29.
    Abid, Hamza
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Techno-economic analysis of energy storage integration for solar PV in Burkina Faso2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Electrification in rural areas of West African countries remain to be a challenge for the growth of the region. The Economic Community of West African States (ECOWAS) has set a target of 2030 to achieve 100% electrification in all member countries. Burkina Faso is one of the least electrified countries in the world, where only 9 % of the rural population has access to electricity. This study presents a conceptualization of techno-economic feasibility of pumped hydro storage (PHS) and electric batteries with solar photovoltaics (PV) in the context of Burkina Faso. The results are explored for an off grid standalone PV plus storage system for a rural setting and a grid connected PV system for an urban setup. The least cost configurations for both the cases are determined using HOMER (Hybrid Optimization Model for Electric Renewables). The results indicate the need of extended solar penetration in Burkina Faso in response to the challenges of low electrification rates in the country. Adding more PV to the present electricity mix of Burkina Faso could drive down the cost of energy by 50 % compared to the present grid electricity prices by making cheap electricity available to the local population. Adding PHS to grid connected PV leads to a cost reduction of 8% over a lifetime of 25 years which does not provide enough motivation for the high investments in storage at present. Policy interventions that allow stacking up of revenues and benefits of storage are needed to make it more competitive. PV plus pumped hydro storage remains the optimal system architecture as compared to PV plus electric batteries for off grid standalone systems provided the geographic availability of lower and upper reservoirs. The capital cost of PV remains to be the most dominating factor in the cost of optimal system for both the urban and the rural cases, and driving down the costs of PV would have the most positive effect for increased electricity access in the country.

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  • 30.
    Abid, Hamza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Thakur, Jagruti
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems.
    Khatiwada, Dilip
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Bauner, David
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability, Industrial Dynamics & Entrepreneurship. Renetech AB, Sweden.
    Energy storage integration with solar PV for increased electricity access: A case study of Burkina Faso2021In: Energy, E-ISSN 0360-5442, Vol. 230, no 120656, p. 120656-Article in journal (Refereed)
    Abstract [en]

    Electricity access remains a challenge for the majority of the West African countries, wherein 5 out of 16 have an electrification rate of less than 25%, with Burkina Faso having only 9% of the rural population with electricity access in 2017. This study presents a techno-economic feasibility analysis of solar PV system integration with conceptualized Pumped Hydro Storage (PHS) and electric batteries for Burkina Faso. The study explores two cases (a) an off-grid PV with a storage system for rural areas and (b) a grid-connected PV system for an urban location. The least-cost configuration of PV with feasible storage is investigated using HOMER. The results show that Solar PV with PHS remains the optimal system configuration for both rural and urban cases even when the construction costs of lower and upper reservoirs are considered. Battery energy storage systems remain an economically expensive solution even when the added costs of pumped hydro storage are included, owing to the low lifetime and high capital costs of battery storage. The capital cost of PV remains to be the most dominating factor for both cases, signifying the importance of policy interventions for cost reduction of PV for increased green electrification in West African countries.

  • 31.
    Abou Jaoudeh, Elie
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Developement of Optimization Method/A Tool for RE applications in Intermittent Grids with focus on Lebanon2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Renewable energy applications require sound design and optimization of life cycle costs because they need upfront investments and as long as possible operating lifetimes are expected. Using modern tools for optimizing designs of grid-tied and autonomous plants allows investors to deploy these technologies while keeping risks within acceptable limits.

    Nevertheless in Lebanon, the grid is intermittent and the most adapted solutions are dual-mode plants that can operate autonomously and with grid-tie. There are no existent simulation models particularly adapted to optimize these applications for such a situation. The objective of this research is to suggest and test a model adapted from commercially available software that can simulate the particular conditions of Lebanon. The studied solution has a PV generator associated with a PV charge controller, lead acid battery, a dual mode inverter, and transfer switchgear and protections. The research successfully met the objective of finding a setup in HOMER 2.68beta for simulating and optimizing a PV-Battery AC plant for an intermittent grid with scheduled blackouts.

    The setup and adaptation in HOMER is made to replicate an existing reference PV-Battery plant at a public school. The measured data from this public school is used to validate the results obtained from the adapted HOMER simulation. The grid is supplied for an average of 12 hours per day at the reference site with a tariff of USD 0.1/kWh.

    After the validation process, a sensitivity analysis is performed to simulate this plant under

    1. Different grid supply hours, 12 and 18 hours of supply daily
    2. Different grid electricity prices, USD 0.1 and 0.1375 /kWh
    3. Simulation of PV plants to meet other load profiles typical of community and municipality building centers

    All the simulations cross matched 20 different PV generator sizes to 7 different battery sizes for 5 different total setups.

    The levelized cost of electricity, COE, is the main parameter used to find the optimum setups, whereas options that shortened the battery life to less than 12 years or couldn’t meet at least 90% of the required yearly load were filtered out. The COE is calculated manually since several corrections related to grid and net-metering limitations are not obtained directly from HOMER.

    The simulated results can serve as a good indicator on how the systems would perform for typical public institutions in Lebanon, given the current conditions, and knowing that the range of this study is limited to small scale institutions with consumption levels less than 30 kWh/day. Storage capacity should also be limited to 100 kWh/day of useful storage, since batteries are not the best option to use for storage capacities higher than the mentioned limit.

    The setup has a great potential for advancement and acts as a first step for Lebanon to have a specialized tool for simulating the performance of PV-battery AC plants optimized for the conditions existing in the country. Future steps could be made to improve and diversify the software to include:

    • irradiation data that come from actual data logging data from other PV sites which are installed around the whole country, almost a 100
    • financial analysis for offsetting private generation with fossil fueled gensets, which is the main backup for electricity blackouts
    • wind turbine simulations, several installations are provisioned to be completed by the end of 2012, and it would be possible to carry out a similar validation process for small wind turbines
    • pollution and other environmental costs
    • value of lost load, “VOLL”, to compare different options in parallel with COE.

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    Abou Jaoudeh Elie EGI-2012-81MSC-EKV-910
  • 32.
    Abrahamsson, Cajsa
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Miljöpåverkan, hälsopåverkan och LCC för direktdrivna kontra växellådsdrivna vindkraftverk med avseende på deras innehåll av jordartsmetaller2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    Vindkraftverk med olika magnetiseringsmetoder (elektromagneter eller permanentmagneter) och maskindriftstyper (direktdrift eller växellådsdrift) undersöks i denna rapport, gällande användningen av jordartsmetaller i dessa. I första delen av rapporten studeras miljö- och hälsopåverkan från jordartsmetallindustrin i den kinesiska provinsen Baotou. Detta då Baotou står för en stor del av försörjningen av jordartsmetaller till vindkraftverksindustrin. I den andra delen av rapporten undersöks skillnaderna i livscykelkostnader mellan vindkraftverk med olika generator- och maskindriftsystem. Rapporten innehåller informationssökningar om olika aspekter som berör dessa teman såsom exempelvis olika typer av vindkraftverksgeneratorer på marknaden, miljöpåverkan från olika ämnen i jordartsmineraler, återvinning av jordartsmetaller och processen från jordartsmineral till permanent-magnet. Informationen är främst inhämtad från vindkraftverkstillverkare, tekniska rapporter och artiklar.

    I miljö- och hälsoanalysen blev slutsatsen att den negativa påverkan från jordartsmetallindustrin i Kina var för omfattande för att användningen av jordartsmetaller skulle rättfärdigas ur ett etiskt och miljömässigt perspektiv. Gruvdriften och bearbetningen av jordartsmetaller har lett till stora utsläpp av skadliga ämnen, såsom exempelvis tungmetaller och radioaktivt avfall, i provinsen Baotou. Dessa har gett allvarliga negativa konsekvenser för djur, människor och växtlighet.

    Livscykelkostnaderna för vindkraftverk med olika generatorsystem beräknades med hjälp av LCC-metoden. Slutsatsen blev att det i dagsläget inte skiljde så mycket kostnadsmässigt i valet av maskindrifttyp eller magnetiseringsmetod. Enligt beräkningar ledde användningen av permanent-magneter inte till några ekonomiska fördelar. Istället var det kostnadsförhandlingar och osäkerhet i indata som gav de största kostnadsskillnaderna. Drift och underhållskostnaderna stod för de definitivt största utgifterna och investeringskostnaderna till generatorsystemen för de näststörsta utgifterna.

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  • 33.
    Abrahamsson, Cajsa
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Carlberg, Marcus
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Studie i att ersätta kärnkraftsreaktor med biobränslealternativ2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report contains a study of replacing nuclear power with biofuel. The nuclear plant, OKG north of Oskarshamn in Sweden has been chosen and an extensive literature study about the nuclear plant has been implemented. The main aspect of this report is the availability of biofuels and whether it would be economically sustainable. Sweden’s most common biofuels are examined with regard to scope of use and potential. In the economic analysis the investments and variable costs are investigated. To conclude the work the carbon emissions due to transports of biofuel are examined.The literature study on biofuels were discussed and resulted in that the project was defined towards woodchips. Due to several aspects the project focused on replacing OKG's oldest reactor O1. Furthermore the project focused on just electricity production and combustion with CFB-boilers. Due to the Economic analysis the plant will not be profitable in the current situation. The plant profitability was examined by the net present value method. With 2011s prices, a discount rate of 6 % and an initial investment of 5.78 billion SEK the economic analysis yielded a net present value of -3.53 billion SEK. A higher price of electricity or an alternate income, for example by district heating, would be required to make the plant profitable. It would require a price of electricity of 0.55 SEK/kWh to make the plant profitable. The carbon emission due to transports of biofuel for the new plant was estimated to 6 gram/kWh and this emission was higher than that for the reactor O1.

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    Studie i att ersätta kärnkraftsreaktor med biobränslealternativ
  • 34.
    Abu Zeid, Houda
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Syed, Tanya
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Suitable textile recycling methods for implementation inSweden: A study in mechanical and chemical recycling methods2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report strives to examine the economical, technical and environmental aspects of textileproduction, but mainly textile recycling. Comparisons between natural fibers and syntheticones will be made, comparing both positive and negative aspects. The textile fibers that willbe discussed are cotton, viscose, polyester and lyocell. Furthermore, an analysis of varioustextile recycling technologies currently available and how suited they are for today’s societywill be made. By doing so one can explore the future possibilities and limitations for thedevelopment of textile recycling. A SWOT-analysis will be conducted in order to examinethe possibility to implement one of the recycling techniques in Sweden. The conclusion thatformed from the SWOT-analysis was that the chemical recycling technique is better fitted fora country of Sweden’s nature. Furthermore, in order for Sweden to be able to implement alarge scale recycling system there is a need for development of certain areas, such as sortingtechnologies, collection and general managing of recycled textile fibers. Some furtherconclusions from this study are that:● Greater focus is needed in order to increase the collection of textiles, since thechemical recycling method is the most efficient when it comes to the recycling oflarger volumes of textiles.● The majority of the sorting of textiles should be done automatically to facilitate thehandling of the collection of textiles.● In the beginning one should focus on recycling textiles that only consist of one type offiber, this since the recycling of textiles consisting of more than one type of fiber ismore complex and the technique for it is not yet fully developed.There are two parts to the report. The first part contains an introduction and a description ofthe project’s research questions and mission. The second part is a literature study whichcontains information about different types of textile fibers currently available and how theproduction and recycling of these fibers affect the environment and society as a whole. Theliterature study is followed by a description of the model used in this report and also ananalysis of the final results. An interview conducted with the sportswear company HoudiniSportswear AB can also be found in the literature study.

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  • 35.
    Abuasbeh, Mohammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn (Editor)
    KTH, Superseded Departments (pre-2005), Energy Technology. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Aquifer Thermal Energy Storage Insight into the future2018Report (Refereed)
    Abstract [en]

    Underground Thermal Energy Storage (UTES) systems, such as Aquifer thermal energy storage(ATES) are used in several countries. The regulation and research on the potential impacts of ATESon groundwater resources and the subsurface environment often lag behind the technologicaldevelopment of an ever-growing demand for this renewable energy source. The lack of a clear andscientifically supported risk management strategy implies that potentially unwanted risks might betaken at vulnerable locations such as near well fields used for drinking water production. At othersites, on the other side, the application of ATES systems is avoided without proper reasons. Thisresults in limiting the utilization of the ATES technology in many occasions, affecting the possibilityto increase the share of renewable energy use. Therefore, further studies to characterizegroundwater resources, performance monitoring and identification of environmental impacts areneeded to understand the advantages and limitations of ATES systems.

    The environmental impact and technical performance of a Low Temperature ATES (LT-ATES)system in operation since 2016 is presented. The system is called Rosenborg and is owned byVasakronan. It is located in the northern part of Stockholm, on a glaciofluvial deposit called theStockholm esker. The ATES system is used to heat and cool two commercial buildings with a totalarea of around 30,000 m2. The ATES consists of 3 warm and 2 cold pumping wells that are able topump up to 50 liters per second.

    Analysis of groundwater sampling included a period of 9 months prior to ATES operation as well asthe first full season of heating and cooling operation. The sampling was conducted in a group ofwells in the vicinity of the installation and within the system. Means of evaluation constituted astatistical approach that included Kruskal-Wallis test by ranks, to compare the wells before and afterthe ATES was used. Then principal component analysis (PCA) and clustering analysis were used tostudy the ground water conditions change before and after the ATES. Aquifer Variation Ratio(AVR) was suggested as mean to evaluate the overall conditions of the aquifer pre- and post- ATES.

    The results showed some variations in redox potential, particularly at the cold wells which likely wasdue to the mixing of groundwater considering the different depths of groundwater beingabstracted/injected from different redox zones. Arsenic, which has shown to be sensitive to hightemperatures in other research showed a decrease in concentration. A lower specific conductivityand total hardness at the ATES well compared to their vicinity was found. That indicates that theyare less subject to salinization and that no accumulation has occurred to date. It is evident that theenvironmental impact from ATES is governed by the pre-conditions in soil- and groundwater. ThePCA and clustering analysis showed very little change in the overall conditions in the aquifer whencomparing the ATES before and after operation. Temperature change showed negligible impact.This can be mainly attributed to the relatively small temperature change (+6 and – 5 degrees) fromthe undisturbed Aquifer temperature which is 10.5°C.

    Performance of Aquifer Thermal Energy Storage (ATES) systems for seasonal thermal storagedepends on the temperature of the extracted/injected groundwater, water pumping rates and thehydrogeological conditions of the aquifer. ATES systems are therefore often designed to work witha temperature difference between the warm side and cold side of the aquifer without riskinghydraulic and thermal intrusion between them, and avoiding thermal leakage to surrounding area, i.e. optimize hydraulic and thermal recovery. The hydraulic and thermal recovery values of the first yearof operation in Rosenorg weres 1.37 and 0.33, respectively, indicating that more storage volume(50500m3) was recovered during the cooling season than injected (36900m3) in the previous heatingseason.

    Monitoring the operation of pumping and observation wells is crucial for the validation of ATESgroundwater models utilized for their design, and measured data provides valuable information forresearchers and practitioners working in the field. After months of planning and installation work,selected measurements recorded in an ATES monitoring project in Sweden during the first threeseasons of operation are reported in this report.

    The monitoring system consists of temperature sensors and flow meters placed at the pumpingwells, a distributed temperature-sensing rig employing fiber optic cables as linear sensor andmeasuring temperature every 0.25 m along the depth of all pumping and several observation wells,yielding temporal and spatial variation data of the temperature in the aquifer. The heat injection andextraction to and from the ground is measured using power meters at the main line connecting thepumping wells to the system. The total heat and cold extracted from the aquifer during the firstheating and cooling season is 190MWh and 237MWh, respectively. A total of 143 MWh of heatwere extracted during the second heating season. The hydraulic and thermal recovery values of thefirst year of operation was 1.37 and 0.33, respectively, indicating that more storage volume(50500m3) was recovered during the cooling season than injected (36900m3) in the previous heatingseason. The DTS data showed traces of the thermal front from the warm storage reaching the coldone. Only 33% of the thermal energy was recovered. These losses are likely due to ambientgroundwater flow as well as conduction losses at the boundaries of the storage volume. Additionally,the net energy balance over the first year corresponds to 0.12 which indicates a total net heating ofthe ATES over the first year. It is recommended to increase the storage volume and achieve morehydraulic and thermal balance in the ATES system. This can enhance the thermal recovery andoverall performance. Continuous monitoring of the ATES is and will be ongoing for at least 3 moreyears. The work presented in this report is an initial evaluation of the system aiming to optimize theATES performance.

    Furthermore, data management and processing tool has been established for the ATES system in Rosenborg. Additionally, a conceptual model of the ATES area has been established. Current andfuture work is focussed on completing a full scale numerical model in FEFLOW and validated themodel (both hydraulically and thermally) with the available monitoring data. Furthermore,establishing recommendations for optimum design and operation of ATES system.

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  • 36.
    Abuasbeh, Mohammad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Fault Detection and Diagnosis for Brine to Water Heat Pump Systems2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The overall objective of this thesis is to develop methods for fault detection and diagnosis for ground source heat pumps that can be used by servicemen to assist them to accurately detect and diagnose faults during the operation of the heat pump. The aim of this thesis is focused to develop two fault detection and diagnosis methods, sensitivity ratio and data-driven using principle component analysis.

    For the sensitivity ratio method model, two semi-empirical models for heat pump unit were built to simulate fault free and faulty conditions in the heat pump. Both models have been cross-validated by fault free experimental data. The fault free model is used as a reference. Then, fault trend analysis is performed in order to select a pair of uniquely sensitive and insensitive parameters to calculate the sensitivity ratio for each fault. When a sensitivity ratio value for a certain fault drops below a predefined value, that fault is diagnosed and an alarm message with that fault appears. The simulated faults data is used to test the model and the model successfully detected and diagnosed the faults types that were tested for different operation conditions.

    In the second method, principle component analysis is used to drive linear correlations of the original variables and calculate the principle components to reduce the dimensionality of the system. Then simple clustering technique is used for operation conditions classification and fault detection and diagnosis process. Each fault is represented by four clusters connected with three lines where each cluster represents different fault intensity level. The fault detection is performed by measuring the shortest orthogonal distance between the test point and the lines connecting the faults’ clusters. Simulated fault free and faulty data are used to train the model. Then, a new set of simulated faults data is used to test the model and the model successfully detected and diagnosed all faults type and intensity level of the tested faults for different operation conditions.

    Both models used simple seven temperature measurements, two pressure measurements (from which the condensation and evaporation temperatures are calculated) and the electrical power, as an input to the fault detection and diagnosis model. This is to reduce the cost and make it more convenient to implement. Finally, for each models, a user friendly graphical user interface is built to facilitate the model operation by the serviceman.

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  • 37.
    Abuasbeh, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    ATES SYSTEM MONITORING PROJECT, FIRST MEASUREMENT AND PERFORMANCE EVALUATION: CASE STUDY IN SWEDEN2018In: Proceedings of the IGSHPA Research Track 2018, 2018Conference paper (Refereed)
    Abstract [en]

    Performance of Aquifer Thermal Energy Storage (ATES) systems for seasonal thermal storage depends on the temperature of the extracted/injected groundwater, water pumping rates and the hydrogeological conditions of the aquifer. ATES systems are therefore often designed to maintain a temperature difference possible between the warm side and cold side of the aquifer, without risking hydraulic and thermal intrusion between them or thermal leakage to surrounding area, i.e. maximize hydraulic and thermal recovery. Monitoring the operation of pumping and observation wells is crucial for the validation of ATES groundwater models utilized for their design, and measured data provides valuable information for researchers and practitioners working in the field. After months of planning and installation work, selected measurements recorded in an ATES monitoring project in Sweden during the first three seasons of operation are reported in this paper. The ATES system is located in Solna, in Stockholm esker, and it is used to heat and cool two commercial buildings with a total area of around 30,000 m 2 . The ATES consists of 3 warm and 2 cold pumping wells that are able to pump up to 50 liters per second. The monitoring system consists of temperature sensors and flow meters placed at the pumping wells, a distributed temperature-sensing rig employing fiber optic cables as linear sensor and measuring temperature every 0.25 m along the depth of all pumping and several observation wells, yielding temporal and spatial variation data of the temperature in the aquifer. The heat injection and extraction to and from the ground is measured using power meters at the main line connecting the pumping wells to the system. The total heat and cold extracted from the aquifer during the first heating and cooling season is 190MWh and 237MWh, respectively. A total of 143 MWh of heat were extracted during the second heating season. The hydraulic and thermal recovery values of the first year of operation was 1.37 and 0.33, respectively, indicating that more storage volume (50500m3 ) was recovered during the cooling season than injected (36900m3 ) in the previous heating season. The DTS data showed traces of the thermal front from the warm storage reaching the cold one. Only 33% of the thermal energy was recovered. These losses are likely due to ambient groundwater flow as well as conduction losses at the boundaries of the storage volume. Additionally, the net energy balance over the first year corresponds to 0.12 which indicates a total net heating of the ATES over the first year. It is recommended to increase the storage volume and achieve more hydraulic and thermal balance in the ATES system. This can enhance the thermal recovery and overall performance. Continuous monitoring of the ATES is and will be ongoing for at least 3 more years. The work presented in this paper is an initial evaluation of the system aiming to optimize the ATES performance.

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  • 38.
    Abuasbeh, Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lazzarotto, Alberto
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Long term performance monitoring and KPIs' evaluation of Aquifer Thermal Energy Storage system in Esker formation: Case study in Stockholm2021In: Geothermics, ISSN 0375-6505, E-ISSN 1879-3576, Vol. 96, article id 102166Article in journal (Refereed)
    Abstract [en]

    The majority of Aquifer Thermal Energy Storage (ATES) systems studies have been conducted in aquifer systems located in large sand aquifers. Esker formation present a more challenging geometrical complexity compared to typical sand aquifers. This study aims to conduct comprehensive and long term performance evaluation of doublet type ATES system in esker geological formation in Stockholm, Sweden. The total heating and cooling used from the ATES are 673 MWh and 743 MWh respectively during the first 3 annual storage cycles of operation. The licensed total amount of water extraction and injection is 50 liters per second with undisturbed groundwater temperature of 9.5 degrees C. Over the first three storage cycles, the average injection and extraction temperatures for the warm side are 13.3 degrees C and 12.1 degrees C, and for the cold side 7.6 degrees C and 10.5 degrees C. The average temperature differences across the main heat exchanger from the ATES side are 4.5 K during winter and 2.8 K during summer which is 4-5 degrees lower than the optimum value. The average thermal recovery efficiency over the first 3 storage cycles were 47 % and 60 % for warm and cold storages respectively. The data analysis indicated annual energy and hydraulic imbalances which results into undesirable thermal breakthrough between the warm and cold side of the aquifer. This was mainly due to suboptimal operation of the building energy system which led to insufficient heat recovery from the warm side, and subsequently insufficient cold injection in the cold wells, despite the building heating demand and the available suitable temperatures in the ATES. The cause of the suboptimal operation is the oversizing of the heat pumps which were designed to be coupled to larger thermal loads as compared to the ones in the final system implementation. As a result, the heat pumps could not be operated during small-medium loads. Additionally, the paper discusses the limitations of currently used energy and thermal key performance indicators (KPI) for ATES and propose an additional thermal KPI named heat exchanger efficiency balance (beta HEX) that connects and evaluate the optimum operational point of temperature differences from both the building and ATES prospective. In addition to ATES energy and hydraulic KPIs, beta HEX can contribute in providing more complete picture on the ATES-building interaction performance as well as highlights if the losses in energy recovery from ATES are due to the subsurface processes or building energy system operation which has been proven to be critical for the optimum ATES performance.

  • 39.
    Abudaff, Anthony
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Möjligheter med betong vid miljöcertifiering: En studie om hur en betongleverantör till byggindustrin kan bidra till en miljöcertifiering2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To steer towards a more sustainable building environment, more and more buildings are certified. The systems requiring input material in the building are Environment Building, BREEAM and LEED. An environmental certification brings together a lot of facts about the building and its sub-materials, and then evaluated according to the criteria of the current environmental certification system. This work aims at examining and assessing what grade or number of points prefabricated concrete elements from Benders byggsystem AB achieve in their respective certification systems.The work has taken advantage of the Concrete Association's reports on how the concrete's characteristics contribute to meeting the requirements of the certification systems. The result is based on material specification and information from Benders together with the Concrete Association's "Sustainable Concrete Construction - Environmental Certification Guide BREEAM / LEED / Environment Building"The result shows which criteria Benders prefabricated concrete elements are able to contribute to the different certification systems. The results of the study show that it is difficult to specifically assess how much an individual building component contributes or what impact it may have on a certification's final grade. All certification methods consider and assess buildings as a whole and in some cases together with its surroundings. The preconditions for environmental certification grades depend on factors beyond the building and its technical solutions. Geographical location, building orientation and surroundings are factors that influence the assessment.Concrete material properties have an indirect impact on many of the aspects of certification systems. In some aspects, such as the amount of waste and local production, there are good conditions for points.Prerequisites in an environmental certification are based on the constructor's / contractor's actions and decisions are partly decisive for the outcome of the certification. In Bender's case it is particularly important to provide full and easily accessible product information of their building elements to facilitate the certification of a building.

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  • 40.
    Accili, Alessia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Natural ventilation strategies for nearly – Zero Energy Sports Halls2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In line with the article 9 of the EPDB, member states shall ensure that all new public properties are nearly zero energy buildings (n-ZEB) by December 31, 2018. Sports buildings account for a significant share of the European building stock consumption. More than half of their current energy needs are related to lighting, and a relevant energy use is due to domestic hot water. This work aims to test different energy measures to design nearly zero energy sports halls in Mediterranean climates. Under a holistic approach, the design of the base case sports hall includes the implementation of passive strategies in combination with renewable energy and energy efficient systems in order to meet the n-ZEB conditions. However, a special focus is put on the study of the sports hall ventilation requirements. A natural ventilation system is proposed as an alternative to a traditional mechanical one. The effectiveness of the analyzed ventilation strategies is validated using TRNSYS, a dynamic simulation tool. Therefore, natural ventilation impact on thermal comfort, air quality and energy needs is estimated. A cost effective evaluation is done following the methodology proposed by the European Directive. Additionally, the study is complemented with a short period of measurements in a selected existing facility according to which poor indoor air quality is the main cause of users discomfort during period of maximum occupancy. The obtained results show that the combination of reduction of thermal transmittance of the envelope, optimization of the windows surfaces, façades orientation, introduction of shading devices, installation of energy efficiency systems as LED lamps and use of natural and night ventilation, are advantageous for the reduction of heating, cooling and artificial lighting demand. Overall, consisted primary energy savings are achieved. Moreover, the described strategies ensure indoor thermal comfort, minimizing the period of overcooling and overheating, and provide good air quality conditions for most of the occupied time along one year simulation. Finally, it is verified that the PV system integration positively affects the sports hall performance toward n-ZEB standards.

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  • 41.
    Acuna, José
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Fossa, Marco
    University of Genova.
    Monzó, Patricia
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Numerically generated g-functions for ground coupled heat pump applications2012In: Proceedings of the COMSOL Conference in Milan, 2012Conference paper (Refereed)
    Abstract [en]

    In most ground-coupled heat pump systems, Borehole Heat Exchangers (BHE) represent the typical engineering solution for utilizing renewable energy from the ground. The design of a complex BHE field is a challenging task, due the inherent transient nature of the thermal interaction between the heat exchangers and the surrounding soil. A computation effective method for solving the 3D transient conduction equation describing the ground response to a variable heat load profile is the temporal superposition of pre-calculated temperature response factors or g-functions. In this study Comsol heat conduction models have been developed to calculate g-function values for a borehole field with 64 boreholes. The aim of the investigation is to get an insight on the numerical generation of temperature transfer functions and to some extent provide new information on the Finite Line Source method for analytically generated g-functions as well as on those existing behind existing design software such as EED. The results generally showed a good agreement in lower time ranges. Further in time, the Comsol model revealed to be influenced either by the domain dimensions or the simulation end time.

  • 42.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Bergvärmepumpar Kan Göras Ännu Mer Effektiva2008In: Enegi&Miljö, ISSN 1101-0568, no 3Article in journal (Other (popular science, discussion, etc.))
  • 43.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Characterization and Temperature Measurement Techniques of Energy Wells for Heat Pumps2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ground source heat pumps are a widely used approach to efficiently heat single family houses. In addition to using the ground as a heat source during the winter, it can be used as heat sink and as a free cooling source during the summer. The most common way to carry out the heat exchange with the ground is with the help of energy collectors (borehole heat exchangers) in vertical wells. The quality of the heat exchange depends on the type of collector and on the flow conditions of the circulating fluid. For a complete understanding of the heat transfer performance, it is necessary to carry out careful temperature measurements at research installations and to do a preliminary characterization of the boreholes. These activities might represent a significant cost saving since the system can be optimized based on their outcome. The characterization consists of determining the type of rock and its thermal properties, the groundwater flow at different depths, and the borehole deviation according to the expected position. A comprehensive study about these characterization actions as well as temperature measurement techniques in boreholes using thermocouples and fiber optic technology are described in this report. Study cases from real installations are also presented to exemplify the characterization and measurement methods.

  • 44.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Distributed thermal response tests: New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.

    Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.

    A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.

    The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.

    Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.

    Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.

    At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.

    Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.

    Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.

    Download full text (pdf)
    José Acuña - Doctoral Thesis
  • 45.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Effektivare Utnyttjande av Energibrunnar för Värmepumpar Undersöks på KTH2010In: KYLA Värmepumpar, ISSN 1100-343X, Vol. 6Article in journal (Other (popular science, discussion, etc.))
  • 46.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Forskningsprojekt Ska Ge Effektivare Bergvärme2009In: VVS Forum, ISSN 0346-4644, no 1Article in journal (Other (popular science, discussion, etc.))
  • 47.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Framtidens värmesystem med borrhålsvärmeväxlare2011In: Energi&Miljö, ISSN 1101-0568, no 2Article in journal (Other (popular science, discussion, etc.))
  • 48.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Improvements of U-pipe Borehole Heat Exchangers2010Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The sales of Ground Source Heat Pumps in Sweden and many other countries are having a rapid growth in the last decade. Today, there are approximately 360 000 systems installed in Sweden, with a growing rate of about 30 000 installations per year. The most common way to exchange heat with the bedrock in ground source heat pump applications is circulating a secondary fluid through a Borehole Heat Exchanger (BHE), a closed loop in a vertical borehole. The fluid transports the heat from the ground to a certain heating and/or cooling application. A fluid with one degree higher or lower temperature coming out from the borehole may represent a 2-3% change in the COP of a heat pump system. It is therefore of great relevance to design cost effective and easy to install borehole heat exchangers. U-pipe BHEs consisting of two equal cylindrical pipes connected together at the borehole bottom have dominated the market for several years in spite of their relatively poor thermal performance and, still, there exist many uncertainties about how to optimize them. Although more efficient BHEs have been discussed for many years, the introduction of new designs has been practically lacking. However, the interest for innovation within this field is increasing nowadays and more effective methods for injecting or extracting heat into/from the ground (better BHEs) with smaller temperature differences between the heat secondary fluid and the surrounding bedrock must be suggested for introduction into the market.

    This report presents the analysis of several groundwater filled borehole heat exchangers, including standard and alternative U-pipe configurations (e.g. with spacers, grooves), as well as two coaxial designs. The study embraces measurements of borehole deviation, ground water flow, undisturbed ground temperature profile, secondary fluid and groundwater temperature variations in time, theoretical analyses with a FEM software, Distributed Thermal Response Test (DTRT), and pressure drop. Significant attention is devoted to distributed temperature measurements using optic fiber cables along the BHEs during heat extraction and heat injection from and to the ground.

    Download full text (pdf)
    FULLTEXT01
  • 49.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Optimera med Rätt Kollektorval2010In: Borrsvängen, ISSN 1103-7938, no 2Article in journal (Other (popular science, discussion, etc.))
  • 50.
    Acuña, José
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Slang intill bergväggen ger effektivare värmeväxling2009In: HUSBYGGAREN, ISSN 0018-7968, no 6Article in journal (Other (popular science, discussion, etc.))
1234567 1 - 50 of 3876
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