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  • 1.
    Fischer, Andreas C.
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Toral, T. R.
    Lindberg, K. B.
    Wille-Haussmann, B.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Investigation of Thermal Storage Operation Strategies with Heat Pumps in German Multi Family Houses2014In: Energy Procedia, Elsevier, 2014, p. 137-144Conference paper (Refereed)
    Abstract [en]

    The use of air source heat pumps is an efficient method to provide heat for space heating and domestic hot water in residential buildings, which cover roughly one third of the German domestic energy use. Capacity controlled heat pumps are gaining increased market share and provide high flexibility in operation. The possibility to use thermal storage to decouple thermal production and electric load from the heat pump can be used for operation strategies, hereby increasing the possibility to integrate electricity production from renewable energy sources. In the work presented, a range of operational strategies for capacity controlled heat pumps connected to a thermal storage in German multifamily houses are introduced and evaluated. The use cases include maximization of energy performance, cost minimization and utilization of on-site photovoltaic production. For optimal storage operation a model predictive control (MPC) approach using quadratic programming is presented together with simplified models of the multi-family house, a thermal storage and a capacity controlled air-to-water heat pump, the MPC creates a control signal to the heat pump. The resulting control signal is then applied to a detailed heat pump model to investigate the impact on the efficiency of the heat pump unit and thereby its electric energy consumption with different storage options.Results show that the MPC strategy is able to adapt to different objectives. One of the most important findings is that changing the objective towards a variable day-ahead-price-based operation leads to decreased heat pump efficiency but increases revenue. The sensitivity analysis towards storage size shows little influence in the range of sizes investigated.

  • 2. Fischer, David
    et al.
    Lindberg, Karen Byskov
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Wittwer, Christof
    Impact of PV and variable prices on optimal system sizing for heat pumps and thermal storage2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 128, p. 723-733Article in journal (Refereed)
    Abstract [en]

    Heat pump (HP) units coupled to thermal storage offer flexibility in operation and hence the possibility to shift electric load. This can be used to increase PV self-consumption or optimise operation under variable electricity prices. A key question is if new sizing procedures for heat pumps, electric boilers and thermal storages are needed when heat pumps operate in a more dynamic environment, or if sizing is still determined by the thermal demand and thus sizing procedures are already well known. This is answered using structural optimisation based on mixed integer linear programming. The optimal system size of a HP, an electric back-up heater and thermal storage are calculated for 37 scenarios to investigate the impact of on-site PV, variable electricity price, space heat demand and domestic hot water demand. The results are compared to today's established sizing procedures for Germany. Results show that the thermal load profile has the strongest influence on system sizing. In most of the scenarios investigated, the established sizing procedures are sufficient. Only large PV sizes, or highly fluctuating electricity prices, create a need for lager storage. However, allowing the storage to be overheated by 10 K, the need for a larger storage only occurs in the extreme scenarios. (C) 2016 Elsevier B.V. All rights reserved.

  • 3.
    Fischer, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology. Fraunhofer Institute for Solar Energy Systems, Germany.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    On heat pumps in smart grids: A review2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 70, p. 342-357Article, review/survey (Refereed)
    Abstract [en]

    This paper investigates heat pump systems in smart grids, focussing on fields of application and control approaches that have emerged in academic literature. Based on a review of published literature technical aspects of heat pump flexibility, fields of application and control approaches are structured and discussed. Three main categories of applications using heat pumps in a smart grid context have been identified: First stable and economic operation of power grids, second the integration of renewable energy sources and third operation under variable electricity prices. In all fields heat pumps - when controlled in an appropriate manner - can help easing the transition to a decentralized energy system accompanied by a higher share of prosumers and renewable energy sources. Predictive controls are successfully used in the majority of studies, often assuming idealized conditions. Topics for future research have been identified including: a transfer of control approaches from simulation to the field, a detailed techno-economic analysis of heat pump systems under smart grid operation, and the design of heat pump systems in order to increase flexibility are among the future research topics suggested.

  • 4.
    Fischer, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Wolf, T.
    Wapler, J.
    Hollinger, R.
    Madani Larijani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Model-based flexibility assessment of a residential heat pump pool2017In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 118, p. 853-864Article in journal (Refereed)
    Abstract [en]

    This paper presents and demonstrates a methodology to explore the flexibility of a heat pump pool. Three points are in the focus of this work: First the procedure to model a pool of residential heat pump systems. Second the study of the response of a large number of heat pumps when the Smart-Grid-Ready interface is used for direct load control. Third a general assessment of flexibility of a pool of heat pump systems. The presented pool model accounts for the diversity in space heating and domestic hot water demands, the types of heat source and heat distribution systems used and system sizing procedures. The model is validated using field test data. Flexibility is identified by sending trigger signals to a pool of 284 SG-Ready heat pumps and evaluating the response. Flexibility is characterized by maximum power, shiftable energy and regeneration time. Results show that flexibility is highly dependent on the ambient temperature and the use of an electric back-up heater. It is found that using SG-Ready-like signals offers significantly higher flexibility than just switching off heat pumps, as it is mostly done today.

  • 5.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity-controlled Ground Source Heat Pump Systems for Swedish single-family dwellings2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The overall objective of this thesis is to develop a structured method to approach the challenge of better understanding the techniques and potential for capacity control in Ground Source Heat Pump (GSHP) systems used in Swedish single-family dwellings. This thesis aims at development of a generic model of the system that can be used for comparative, descriptive, and predictive analysis of capacity controlled GSHP systems in single-family dwellings.

    In order to develop the generic model, first, a conceptual model of the reality of interest is developed based on the objective of the model. Second, a quantitative model of the system is developed based on the conceptual model. Third, experimental studies are carried out in order to obtain better understanding of the behavior of the system and its components and also to validate the capabilities of the model. Furthermore, some examples are presented to show how the generic model developed and evaluated at the previous stages can be used to address the questions in the context of capacity control in GSHP systems.

    As the first example of applications of the generic model, a comparative analysis is made between the annual performance of on/off-controlled and variable-capacity GSHP systems. The results show that dimensioning of the on/off-controlled GSHP unit based on the peak heat demand of the building plays a significant role when the annual performance of the on/off controlled GSHP system is compared with that of the variable speed GSHP system. As the second example, another comparative analysis is performed, this time to compare three common methods whose purpose is to control on/off-controlled GSHP system. Based on the results from the detailed analysis of these three control methods, it is recommended not to use the constant hysteresis method to avoid large supply temperature oscillation or large deviation from the required temperatures.

    Finding a proper brine mass flow rate, either variable or constant, is a challenge when a variable capacity heat pump system (a heat pump system equipped with a variable speed compressor) is designed. Therefore, as the third example of applications of the generic model, analysis is performed on a variable-capacity GSHP system equipped with a variable speed compressor and variable speed pump in U-pipe borehole heat exchanger. The results show that a single speed liquid pump but with a very carefully-selected brine mass flow rate would be still an appropriate option for variable speed heat pump systems, if COP maximization is the main concern.

    Finally, as the fourth example, the performance of a run-around coil heat recovery system equipped with a variable capacity heat pump unit is evaluated over a year. The results show that by retrofitting a well-sized variable capacity heat pump unit to the system, there is a potential to increase the amount of heat provided by the recovery system by more than 70%.

    In addition to the examples shown, the systematic approach and the generic model used in the present study can be applied to improve other control techniques and strategies and find new opportunities which can lead to saving energy and money, reducing the greenhouse gas emissions, and gaining higher credibility for GSHPs in the market.

  • 6.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    The common and costly faults in heat pump systems2014In: Energy Procedia, 2014, p. 1803-1806Conference paper (Refereed)
    Abstract [en]

    The heat pump market has become mature in many countries. There are millions of heat pumps installed worldwide. So any improvement in the installation, operation, and maintenance of heat pump system can save a considerable amount of energy and cost, and reduce Green House Emissions to a large extent. In order to minimize the number of faults in installation and operation phases and improve the maintenance process, it is essential to obtain knowledge about the common and expensive faults which usually occur in the heat pump systems. Insurance companies and heat pump manufacturers (OEMs) are the best sources to find out the most common and costliest faults recently occurred in the heat pump systems. The present paper describes the results from a comprehensive study done on the most recent faults which were reported to both OEMs and insurance companies in Sweden. According to the results, it is essential to pay a special attention to the control and electronics in heat pump system in order to reduce the number and cost of the faults in the heat pump systems. Furthermore, the results show the importance of system thinking in any effort to minimize, detect or diagnose the faults in heat pump system.

  • 7.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Variable capacity heat pump system in a single family house: dynamic modeling and simulation2009In: Journal of federation of European HVAC association (REHVA), no 13Article in journal (Other academic)
  • 8.
    Madani, Hatef
    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.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    The Ground Source Heat Pump: A System Analysis With a Particular Focus on The U-Pipe Borehole Heat Exchanger2010In: 2010 14th International Heat Transfer Conference, Volume 4, 2010, p. 395-402Conference paper (Refereed)
    Abstract [en]

    The mass flow rate of the secondary refrigerant flowing in the borehole heat exchanger of a ground source heat pump is an influential system parameter whose variation can influence the pumping power, efficiency of the pump, heat distribution in the borehole, heat pump heat capacity, and above all, the system Overall Coefficient Of Performance (COP). The present paper uses both in-situ field measurements and modeling to evaluate these effects. From the field measurements, it can be concluded that the thermal contact between U-pipe channels increases as the brine mass flow rate decreases. Furthermore, the modeling results show that there is a certain optimum brine mass flow rate which gives a maximum overall system COP. Different optimum mass flow rates are obtained for different compressor speed and it is shown that their relation is almost linear. However, concerning system COP maximization, it can be concluded that a constant but carefully-selected brine mass flow rate can still be an appropriate option for the variable capacity heat pump unit studied in the present paper where the compressor frequency changes between 30Hz and 75Hz. Concerning the heat capacity maximization in the system, a variable speed brine pump can be used to help the insufficiently-sized compressor to cover the peak heat demand of the building.

  • 9.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ahmadi, Navid
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Experimental Analysis of a Variable Capacity Heat Pump System Focusing on the Compressor and Inverter Loss Behavior2010In: Proceeding International Refrigeration and Air Conditioning Conference, Academic Conferences Publishing, 2010Conference paper (Refereed)
    Abstract [en]

    Capacity control with variable speed compressors in heat pump systems is one of the techniques having a potentialfor efficiency improvement in heat pump systems. It is anticipated that the compressor and inverter efficiency areinfluenced by changes of the compressor speed. The present experimental study evaluates these losses in a variablespeed heat pump system.The experimental results show that increasing the compressor speed reduces the heat pump COP up to 30%. Theinverter loss increases as the compressor speed is increased, although the inverter loss as the percentage of the totalcompressor power decreases. Increasing the compressor speed increases the pressure ratio from 2.7 to 5.8,increasing the loss due to the pressure ratio mismatch drastically. Finally, the highest total isentropic efficiency ofthe compressor is obtained when the compressor frequency is close to 50Hz.

  • 10.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundquist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in ground source heat pump systems part II: Comparative analysis between on/off controlled and variable capacity systems2011In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 34, no 8, p. 1934-1942Article in journal (Refereed)
    Abstract [en]

    In the present paper, as the second part of two, modeling and simulation was carried out for a Ground Source Heat Pump (GSHP) system in the presence of all the most important interacting sub-systems such as building, ground heat source, electrical auxiliary heater, and the heat pump unit in order to make a fair and comprehensive comparison between the annual performance of on/off controlled and variable capacity systems. The annual modeling showed that dimensioning of the on/off controlled GSHP based on the peak heat demand of the building plays a significant role when the two control strategies are compared: if the on/off controlled GSHP is dimensioned to cover only 55% of the peak heat demand of the building, the electrical auxiliary, which then covers about 10% of the annual heating demand of the building, makes the SPF of the on/off controlled GSHP to be lower than the one of the variable speed system. On the contrary, when the on/off controlled system is dimensioned to cover more than 65% of the building's peak heat demand, i.e. more than 95% of the annual heat demand of the building, there is no considerable difference between the SPFs of the on/off controlled and variable capacity systems.

  • 11.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A descriptive and comparative analysis of three common control techniques for an on/off controlled Ground Source Heat Pump (GSHP) system2013In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 65, p. 1-9Article in journal (Refereed)
    Abstract [en]

    In the present paper, three common methods in order to control an on/off controlled Ground Source Heat Pump (GSHP) system called "Constant hysteresis", "Floating hysteresis", and "Degree-Minute" methods are comprehensively described. Then, the generic model already developed by the authors is used in order to do the dynamic simulation of the systems with three different control methods over a year and making the comparison between them. The results from annual modeling of the systems show that the mean temperature of the heating water supplied to the building for the system controlled with degree-minute method is always close to the required temperature, regardless of the climatic boundary conditions over a typical year, whereas, the average supply temperature for the system with constant hysteresis method is mostly higher or lower than the required temperature, depending on the boundary condition. Regarding the annual energy use, the degree-minute and constant hysteresis methods have the lowest and highest annual energy use respectively. Switching from constant hysteresis to floating hysteresis method, the annual energy use will become lower and the mean temperature of the heating water supplied to the building will be closer to the required one.

  • 12.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Retrofitting a variable capacity heat pump to a ventilation heat recovery system: modeling and performance analysis2010Conference paper (Other academic)
  • 13.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Variable capacity heat pump systems, modeling and simulation2008In: 9th International Energy Agency Heat pump conference, 2008Conference paper (Refereed)
    Abstract [en]

    Variable speed compressor is one of the most promising ways to modulate thecapacity of heat pump units. The paper describes some common obstacles in the evaluationof variable speed heat pump systems. The inconsistencies between the compared systemcomponents, the complexity in the measurement of some detailed parameters, too muchfocus on unit efficiency solely, but also not considering the effect of system dynamics aresome of the mentioned problems. Dynamic modelling and simulation of a heat pump systemtaking all system components into consideration and validation of the model based onexperiments are suggested as the solution. This paper describes a parameter estimationapproach to variable speed heat pump unit modelling that requires a relatively low demand ofmeasured input data. The outputs of the model are a number of parameters such as totalisentropic efficiency of compressor as a function of frequency, superheat temperature andsub-cooling temperature, etc. Making use of the model provides the opportunity to evaluatethe dynamics of the whole system including building and heat source in TRNSYS.

  • 14.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Evaluation of the annual performance of Ground Source Heat Pump systems: A comparison between single speed and variable speed systems2011In: 23rd IIR International Congress of Refrigeration, International Institute of Refrigeration, 2011, p. 3741-3748Conference paper (Refereed)
    Abstract [en]

    In the present paper, modelling and simulation was carried out for a Ground Source Heat Pump (GSHP) system in the presence of all the most important interacting sub-systems such as building, ground heat source, electrical auxiliary heater, and the heat pump unit in order to make a fair and comprehensive comparison between the annual performance of on/off controlled and variable capacity systems. The annual modelling showed that dimensioning of the on/off controlled GSHP based on the peak heat demand of the building plays a significant role when two control strategies are compared: if the on/off controlled GSHP is dimensioned to cover only 57% of the peak heat demand of the building, the electrical auxiliary, which covers about 10% of the annual heating demand of the building, makes the SPF of the on/off controlled GSHP be lower than the one of the variable speed system. On the contrary, when the on/off controlled system is dimensioned to cover about 70% of the building’s peak heat demand, i.e. about 98% of the annual heat demand of the building, the SPF of the on/off controlled system can higher than the variable capacity systems.

  • 15.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration. KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Sustainable Building Systems.
    P5 – Dynamic heat pump system with capacity control2010Report (Other academic)
  • 16.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Variable capacity heat pumps, modelling and simulation2008In: IEA Heat Pump conference Proceeding (2008) 9th International Energy Agency Heat Pump Conference, Academic Conferences Publishing, 2008Conference paper (Refereed)
  • 17.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Roccatello, Erica
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A comprehensive study on the important faults in heat pump system during the warranty period2014In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 48, p. 19-25Article in journal (Refereed)
    Abstract [en]

    The heat pump market has become mature in many countries. There are millions of heat pumps installed worldwide. So any improvement in the installation, operation, and maintenance of heat pump systems can save a considerable amount of energy and cost, and reduce Green House Emissions to a large extent. The present study suggests a Smart Fault Detection and Diagnosis (SFDD) mechanism as the essential part of the next generation of heat pumps. A SFDD mechanism can minimize the installation and control errors, decrease the performance degradation during operation, avoid unnecessary visual inspections and components replacement, and reduce the maintenance cost and down-time of the system. To develop a SFDD mechanism, the first essential step is to obtain knowledge about the most common and expensive faults experienced by heat pumps. The heat pump manufacturers are one of the best sources to find out the most common and costliest faults occurring in heat pump systems during the first few years of their life. The present paper, as the first part of two, describes the results from a comprehensive study done on the most recent faults which were reported to some of the heat pump manufacturers in Sweden during the warranty period. The most common and the costliest faults in the Air/Air, Air/Water, Brine/Water, and exhaust air heat pumps are presented. Some of the faults such as faulty pressure switches or fans are only related to the heat pump unit, i.e. the thermodynamic cycle which facilitates the heat pumping cycle. Some of the common and expensive faults such as faulty shuttle or shuntvalve are related to the faulty components in the heating systems. Generally, the results show that faults in Control and Electronics are almost the most common and costliest faults in all types of heat pumps. Faults in Control and Electronics include any fault related to control unit, electrical faults (such as short circuit, etc.), Printed Circuit Board (PCB), display, soft starter, overcurrent and motor protection relay, etc.

  • 18.
    Madani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Wallin, Jörgen
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ventilation heat recovery with run around coil: System analysis and a study on efficiency improvement – Part II2009Conference paper (Other academic)
    Abstract [en]

    In order to improve the system efficiency, a heat pump is retrofitted to a conventional run around coil ventilation heat recovery system.  The present paper aims at evaluating the annual performance of both existing run around coil system and the system to which a heat pump is retrofitted. The paper also makes a comparison between the efficiency of these two systems in two different climatic conditions. Dynamic modeling of the system was carried out over a year, using TRNSYS as the simulation tool and the results were presented for different climatic conditions. Results from the annual modeling shows that by retrofitting a well-designed heat pump unit to the system, there is a potential to increase the amount of the recovered heat up to more than 50%. By considering the energy used by the compressor of the heat pump, it can be concluded that the new system looks promising from the economic point of view and it can lead to save a large amount of energy use and money annually.

  • 19.
    Madani Larijani, Hatef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Lundquist, Per Gunnar
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in ground source heat pump systems Part I: modeling and simulation2011In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 34, no 6, p. 1338-1347Article in journal (Refereed)
    Abstract [en]

    The present paper, as the first part of two, suggests a method to approach the challenge of capacity control in Ground Source Heat Pumps (GSHP). The paper describes the development of a model of the system which includes several sub-models such as the heat pump unit, building, ground source, thermal storage tank, auxiliary heater, and climate. The developed computer model can be used for comparative analysis of different control methods and strategies aiming at the improvement of the system seasonal performance. With this model, on/off controlled and variable capacity GSHPs, with a single speed or variable speed pumps in the systems, can be evaluated in a wide range of operating conditions and more energy efficient methods of the system control can be found. The computer model is developed in the two environments EES and TRNSYS utilizing so-called co-solving technique.

  • 20. Mader, Gunda
    et al.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Capacity control in air-water heat pumps: Total cost of ownership analysis2014In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 81, p. 296-304Article in journal (Refereed)
    Abstract [en]

    Adjusting capacity to changing demand by variable speed control is known to offer efficiency improvement over classical on/off control. With a total cost of ownership analysis the economic viability of both control schemes is assessed for residential air-water heat pumps operating in different climate zones. Component sizes are optimized for both control methods individually. Results show optimal compressor displacement volumes to be smaller for variable speed than for on/off control. The optimal ratio of evaporator to condenser size is smaller for the variable speed system. Variable speed control is shown to be uneconomic for space heating in warmer climate while for average climate cost-effectiveness depends on the economic framework. For colder climate variable speed control is the more profitable choice in all considered cases; savings of up to 5000 EUR compared to on/off control can be achieved within 15 years of operation.

  • 21.
    Mader, Gunda
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Bakhtiari, Hossein
    Economic optimization of component sizes in a ground source heat pump systemManuscript (preprint) (Other academic)
  • 22.
    Pressani, Michele
    et al.
    Politecn Milan, Milan, Italy..
    Sommerfeldt, Nelson
    KTH.
    Madani Larijani, Hatef
    KTH.
    Investigation Of Pv/Thermal Collector Models For Use With Ground Source Heat Pumps In Transient Simulations2017In: PROCEEDINGS OF THE 11TH ISES EUROSUN 2016 CONFERENCE / [ed] Martinez, V Gonzalez, J, International Solar Energy Society , 2017, p. 1360-1371Conference paper (Refereed)
    Abstract [en]

    Photovoltaic-thermal (PVT) collectors are commonly designed for use in domestic hot water systems, however it can be interesting to incorporate them into ground source heat pump (GSTIP) systems. Because of the historically narrow use case, many PVT models are created with a collection of assumptions which may not apply to novel collectors designed for use in PVT+GSHP systems. The aims of this study are to review existing PVT collector models for use in TRNSYS, identify any potential error sources, and test for possible improvements. Type 560 is found to be the most promising theoretical model, however two potentially limiting features are identified; the radiation absorption model and the confinement to sheet-and-tube configurations. The absorption is tested using a recreation of Type 560 in Matlab where two alternative models developed specifically for PV modules are compared. The results show a marked increase in power during low angle, low light hours, and a 14.36% increase in electrical energy and a 10.91% for the thermal energy over the course of a day with one of the models. Collector geometry is tested by creating a ID model in EES and comparing it to several geometries in Type 560. A method of packing as many tubes as possible together is shown to give comparable results as the ID model. The results of these simulations will be compared with empirical data from currently ongoing testing.

  • 23.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Improved methodology for determining the value of energy from distributed renewables using statistical analysis combined with normative scenarios2014In: Energy Procedia / [ed] J. Yan, DJ. Lee, SK. Chou, U. Desideri, H. Li, Elsevier, 2014, Vol. 61, p. 1089-1092Conference paper (Refereed)
    Abstract [en]

    The financial benefits of a distributed electric generation facility cannot be calculated without an expectation of the electricity's market value. Prediction of long-term future prices is a difficult but mandatory task, which is often reduced to constant annual prices with steady annual growth rates. This study provides a methodology for predicting electricity prices at an hourly resolution for long-term analysis, using the Swedish case as an example. It includes a statistical examination of historical data inspired by the meteorology sector to create a “typical year” of hourly price values. Future prices are calculated by applying annual rate changes to the typical year curve, using a monthly resolution to allow for seasonal variations. Rate changes are predicted using historical trends and current market conditions for near-term prices, and a normative scenario for mid- to long-term prices. The resulting methodology can be used in part or whole for any market in which historical data is available and a normative scenario created.

  • 24.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    On the use of hourly pricing in techno-economic analyses for solar photovoltaic systems2015In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 102, no SI, p. 180-189Article in journal (Refereed)
    Abstract [en]

    The use of hourly prices in distributed photovoltaic (PV) techno-economic analysis is rare, but may become necessary as time-of-day retail pricing becomes more common. A methodology is presented for selecting an hourly price curve suitable for long-term analysis, called the typical price year (TPY), which is based on the methodology for TMY weather data. Using a techno-economic analysis with annual revenues and net present value as indicators, a TPY curve for the Swedish market is validated and then compared to 18 price simplification methods to determine the error introduced by the use of non-hourly prices. Results show that the TPY method produces a curve which accurately represents long term pricing trends, but using a static annual mean introduces minor revenue errors of 1.3%. This suggests the TPY may not be necessary in the Swedish market, but further analysis of the method is suggested for other markets.

  • 25.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    REVIEW OF SOLAR PV/THERMAL PLUS GROUND SOURCE HEAT PUMP SYSTEMS FOR EUROPEAN MULTI-FAMILY HOUSES2016In: Eurosun 2016, 2016Conference paper (Other academic)
    Abstract [en]

    The combination of photovoltaic-thermal (PVT) hybrid modules with ground source heat pumps (GSHP) has the potential to increase renewable fractions of heating, cooling and power generation in buildings. The concept benefits each component in the system; the solar collector can be more efficient; collected heat can be stored in the boreholes and recovered in both short and long term; and the elevated temperatures of the boreholes improves the efficiency of the heat pump. System optimization is challenging due to the number of possible configurations, options in component designs and system control, and the close interrelation of performance between components. This study presents several system configurations which are designed to be a balance of performance, practicality, and cost. The designs are based on a state-of-the-art literature review from multiple fields (solar collectors, heat pump controls, seasonal thermal storage, and solar assisted heat pumps) and consultations with heat pump and PVT collector manufacturers.

  • 26.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani Larijani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    A Techno-Economic Comparison between PV and PVT Integrated Ground Source at Pumps for Multi-Family Houses2018In: PROCEEDINGS OF THE ISES EUROSUN 2018 CONFERENCE - 12TH INTERNATIONAL / [ed] Haberle, A, International Solar Energy Society, 2018, p. 901-910Conference paper (Refereed)
    Abstract [en]

    As the demand for sustainable energy technologies grows, solar photovoltaics (PV) and heat pumps are increasingly being used in buildings. Hybrid PV-thermal (PVT) collectors have been researched for decades, but have not yet had success in the market. This study combines PVT and ground source heat pumps (GSHP) in a series connection for a multi-family house, and compares the technical and economic performance to GSHP and PV+GSHP systems. A complete systems model in TRNSYS is used for the solar heat pump system, and climate and economic boundary conditions come from the Swedish market. The results show that reducing the borehole length and/or spacing with no or a limited loss of efficiency is the greatest benefit of adding PVT, however a fully sized borehole field with PV is found to be the lowest cost design option. In systems with poor efficiency and high auxiliary boiler use, the addition of PVT can be the lowest cost option but is not preferable to the PV+GSHP when space is not a limitation. The reduction in borehole field area for a given heat pump efficiency is notable since many multi-family homes cannot install GSHP due to a lack of drilling space. PVT+GSHP systems could offer a new, low-carbon heating alternative for buildings previously outside of the heat pump market.

  • 27.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Revisiting the techno-economic analysis process for building-mounted, grid-connected solar photovoltaic systems: Part one - Review2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 74, p. 1379-1393Article, review/survey (Refereed)
    Abstract [en]

    The market for solar photovoltaic systems is growing rapidly into a mature industry, while at the same time policies which have spurred the growth (e.g. feed-in tariffs or net metering) are beginning to fade away. These policies made techno-economic studies relatively simple for engineers, analysts, and owners, however investing in a deregulated market requires more advanced tools than the traditional engineering economics which dominate the literature. The objective of part one in this paper is to catalogue and critique the range of methods and models relevant to techno-economic analysis for PV systems in the context of distributed, grid-connected buildings. This is accomplished by; developing a system modeling framework for prosumer PV investment analysis, reviewing relevant energy, economics, and finance literature to identify mathematical models which can be applied, and cataloging the use of the reviewed techniques in the relevant literature. Also included is a qualitative discussion of the benefits and practicality of the review techniques, where Monte Carlo analysis is highlighted as an exemplary method. This review is useful as a reference for analysts, researchers, and engineers developing PV integration solutions for building energy systems in a post early adopter PV market.

  • 28.
    Sommerfeldt, Nelson
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Revisiting the techno-economic analysis process for building-mounted, grid-connected solar photovoltaic systems: Part two - Application2017In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 74, p. 1394-1404Article, review/survey (Refereed)
    Abstract [en]

    Part One in this two part paper identified Monte Carlo analysis as an improved approach over traditional deterministic techno-economic methods for solar PV prosumers in deregulated markets. In this paper a novel Monte Carlo methodology is described and demonstrated through a case study for the Swedish residential sector, which includes a review of relevant market, climate, and policy conditions, their use in determining inputs, and the probabilistic results. The probability of profitability (PoP) is introduced as an indicator in conjunction with result distributions. The results show that under current policy conditions, Swedish PV investors with well positioned buildings have a 71% chance of making a 3% real return on investment, and virtually no chance of losing their original investment. Without subsidies the PoP drops to 8%. In none of the simulated cases was any of the original investment lost. The PoP is most sensitive to the capital subsidy and the uncertainty of market based, long-term support is less critical to the chances of a successful investment. Given the current market conditions, Swedish PV prosumers can expect a return on investment. The decision to install will also depend on the probability of achieving their desired profitability, which Monte Carlo analysis quantifies well.

  • 29.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    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.
    Building heating solutions in China: A spatial techno-economic and environmental analysis2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 179, p. 201-218Article in journal (Refereed)
    Abstract [en]

    Fast urbanization process and promotion of life standard in China requires a great amount of energy input in building heating sector. North China now faces challenges of upgrading existing fossil fuel based high emission district heating systems into more environmental friendly heating systems. South China is discussing to choose proper building heating solutions for new and existing buildings which lack proper heating facilities. Renewable heating technologies such as ground source heat pump and air source heat pump are candidates to upgrade traditional heating solutions such as fossil fuel boilers and electric heaters. In order to find the most feasible building heating solution for different geolocations of China, this paper proposes a spatial data based techno-economic and environmental analysis methodology to fulfill such research gap. Case studies are carried out in two selected cities by using proposed methodology. Evaluation model shows that, heat pumps is quite competitive in south China compared with electric heaters, whereas in north China heat pumps have to reach several preconditions to be competitive with coal boiler district heating system under current techno-economic and environmental situations. In north China, a heat pump should reach a minimum seasonal coefficient of performance of 2.5-3.7 (for ground source heat pump) or 2.7-3.0 (for air source heat pump) to become CO2 and PM2.5 emission neutral as well as economically competitive compared with coal boiler district heating system. The advantage of proposed methodology is its simplicity in execution and could be repeated to other areas as the data required are available.

  • 30.
    Su, Chang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Madani Larijani, Hatef
    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.
    Spatial Data Assisted Ground Source Heat Pump Potential Analysis in China, a Case of Qingdao City2019In: INNOVATIVE SOLUTIONS FOR ENERGY TRANSITIONS / [ed] Yan, J Yang, HX Li, H Chen, X, ELSEVIER SCIENCE BV , 2019, p. 6099-6104Conference paper (Refereed)
    Abstract [en]

    Nowadays, China faces challenges of further implementing heat pump technology for meeting building heating and cooling demand. The utilization of heat pumps, especially ground source heat pump (GSHP) is associated with a number of geological, hydrological as well as meteorological criteria. Thus it is essential to systematically address the feasibility of ground source heat pumps application using quantitative evaluation. Spatial data analysis is a method widely used in energy field to investigate renewable energy potential. Therefore, this study strives to provide an estimation of electricity driven GSHP's potential in north China using spatial data assisted tools. Followed by a case study using the methodology recommended, a spatial data assisted GSHP potential evaluation model is built for Qingdao city in north China. The evaluation model is constructed and analyzed through spatial data processing software visualized by ground source heat pump potential maps. The result maps show that, places with most potential of GSHP application locate in south Qingdao close to the sea. Such places have a higher ground extractable heat and relatively low drilling cost.

  • 31.
    Wallin, Jörgen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Run-around coil ventilation heat recovery system: A comparative study between different system configurations2010In: ICAE 2010 – International conference on Applied energy – Singapore 21‐23 April 2010, 2010Conference paper (Refereed)
    Abstract [en]

    The energy performance of buildings with considerable annual heat load is dependent on the ventilation air change rates (ACH). Buildings utilized for commercial use often have high ACH and therefore high annual heat load. In order for these buildings to have a reasonable energy performance a heat recovery system is often used to recover heat from the extraction air to the makeup air. There are different variations of these systems; one that is frequently used in Sweden is a run around coil heat recovery system.

    The present paper summarizes the findings from the previous studies, and presents a comparative study, for three different cases; the traditional run-around coil heat recovery system; with a three stage on/off controlled heat pump retrofitted into the system; and with a variable capacity heat pump retrofitted into the system.

    Annual modeling shows that by retrofitting a well-designed 3 stage heat pump to the system the annual heat recovery rate for the Stockholm Case can be increased from 47 % to 65 %. For the retrofitted variable capacity heat pump the numbers for the Stockholm Case is an improvement of annual heat recovery from 47 % to 66 %.

    The modeling also shows that a well designed variable heat pump can cover 81 % of the ventilation heating demand and a well designed multi stage heat pump 77 % of the demand.

  • 32.
    Wallin, Jörgen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Run-around coil ventilation heat recovery system: A comparative study between different system configurations2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 90, no 1, p. 258-265Article in journal (Refereed)
    Abstract [en]

    The energy performance of buildings in cold climates, with a considerable annual heating demand, is dependent on the ventilation air change rates (ACH). Buildings utilized for commercial use often have high annual ventilation heating demand due to high ACH required from indoor air quality aspect. In order for these buildings to have a reasonable energy performance a heat recovery system is often used to recover heat from the exhaust air to the makeup air. There are different variations of these systems; one that is sometimes used in Sweden is a run around coil heat recovery system. The present paper summarizes the findings from previous studies [5-7], and presents a comparative study, for three different cases; the traditional run-around coil heat recovery system; with a three stage on/off controlled heat pump retrofitted into the system; and with a variable capacity heat pump retrofitted into the system. Annual modeling (using TRNSYS) shows that by retrofitting a well-designed 3 stage heat pump to the system the annual heat recovery rate for the Stockholm case can be increased from 47% to 65%. For a retrofitted variable speed capacity heat pump for the Stockholm case the annual heat recovery improves from 47% to 66%. The modeling also shows that a well designed variable speed heat pump can cover 81% of the total ventilation heating demand and a well designed multi stage heat pump 77% of the total ventilation heating demand.

  • 33.
    Wallin, Jörgen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ventilation heat recovery with run around coil - System analysis and a study on efficency improvment - Part I2009In: Ashrae - Symposium on “Sustainability and Green Buildings”, October 5, 2009, KUWAIT, 2009Conference paper (Refereed)
    Abstract [en]

    A run around coil ventilation heat recovery system is analyzed in order to identify important performance factors. The aim of this investigation was to find the factors that influence the system performance, with focus on the brine side of the system. A test rig was built to provide measurements for the evaluation of the system behavior during different operating conditions. Results from measurements and calculations are presented.  Three significant factors that affect system efficiency have been identified, the brine flow rate, the concentration of glycol and the charge (pressure) of the system. In addition suggestions on possible further analysis are presented to the reader. It is also concluded that for many existing systems, the heat transfer resistance may be considered to be approximately constant throughout the year even considering the fact that the outdoor temperature changes significantly.

  • 34.
    Wallin, Jörgen
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Madani, Hatef
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Claesson, Joachim
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Ventilation heat recovery with run around coil: System analysis and a study on efficiency improvement – Part I2009Conference paper (Refereed)
    Abstract [en]

    In order to improve the system efficiency, a heat pump is retrofitted to a conventional run around coil ventilation heat recovery system.  The present paper aims at evaluating the annual performance of both existing run around coil system and the system to which a heat pump is retrofitted. The paper also makes a comparison between the efficiency of these two systems in two different climatic conditions. Dynamic modeling of the system was carried out over a year, using TRNSYS as the simulation tool and the results were presented for different climatic conditions. Results from the annual modeling shows that by retrofitting a well-designed heat pump unit to the system, there is a potential to increase the amount of the recovered heat up to more than 50%. By considering the energy used by the compressor of the heat pump, it can be concluded that the new system looks promising from the economic point of view and it can lead to save a large amount of energy use and money annually.

1 - 34 of 34
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