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  • 1.
    Aichmayer, Lukas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Spelling, James
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Preliminary design and analysis of a novel solar receiver for a micro gas-turbine based solar dish system2015In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 114, no 4, p. 378-396Article in journal (Refereed)
    Abstract [en]

    The solar receiver is one of the key components of hybrid solar micro gas-turbine systems, which would seem to present a number of advantages when compared with Stirling engine based systems and photovoltaic panels. In this study a solar receiver meeting the specific requirements for integration into a small-scale (10 kWel) dish-mounted hybrid solar micro gas-turbine system has been designed with a special focus on the trade-offs between efficiency, pressure drop, material utilization and economic design. A situation analysis, performed using a multi-objective optimizer, has shown that a pressurized configuration, where the solar receiver is placed before the turbine, is superior to an atmospheric configuration with the solar receiver placed after the turbine. Based on these initial design results, coupled CFD/FEM simulations have been performed, allowing detailed analysis of the designs under the expected operating conditions. The results show that the use of volumetric solar receivers to provide heat input to micro gas-turbine based solar dish systems appears to be a promising solution; with material temperatures and material stresses well below permissible limits.

  • 2. An, J.
    et al.
    Yang, X.
    Wang, W.
    Li, J.
    Wang, H.
    Yu, Z.
    Gong, C.
    Wang, X.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Stable and efficient PbS colloidal quantum dot solar cells incorporating low-temperature processed carbon paste counter electrodes2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 158, p. 28-33Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dot (CQD) solar cells with a ZnO/PbS-TBAI/PbS-EDT/carbon structure were prepared using a solution processing technique. A commercially available carbon paste that was processed at low-temperatures was used as a counter electrode in place of expensive noble metals, such as Au or Ag, which are used in traditional PbS CQD solar cells. These CQD solar cells exhibited remarkable photovoltaic performance with a short circuit density (Jsc) of 25.6 mA/cm2, an open circuit voltage (Voc) of 0.45 V, a fill factor (FF) of 51.8% and a power conversion efficiency (PCE) as high as 5.9%. A reference device with an Au counter electrode had a PCE of 6.0%. The PCE of the carbon-containing CQD solar cell remained stable for 180 days when tested in ambient atmosphere, while the PCE of the Au-containing CQD solar cell lost 48.3% of its original value. Electrochemical impedance spectroscopy (EIS) demonstrated that holes within the PbS CQD were effectively transported to the carbon counter electrode.

  • 3. Brinkworth, B. J.
    et al.
    Sandberg, Mats
    KTH Research School University of Gävle, Department of Indoor Environment.
    Design procedure for cooling ducts to minimise efficiency loss due to temperature rise in PV arrays2006In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 80, no 1, p. 89-103Article in journal (Refereed)
    Abstract [en]

    The principal variable to be fixed in the design of a PV cooling duct is its depth, and hence the hydraulic diameter of its cross-section D. Analysis of the flow and heat transfer in the duct under still-air (buoyant flow) conditions, when the temperature rise is greatest, is validated by measurements on a full-scale test rig. It is shown that there is an optimum value of this design variable, such that for an array of length L the minimum temperature occurs when the ratio L/D is about 20. The optimum value is not affected much by other quantities, including the slope of the array. In practical situations, the flow is obstructed by devices across the duct inlet and outlet to exclude insects, birds and rain, and by structural support members crossing the duct interior. It is shown that the latter are no cause for concern, since the effect of the reduction in the flow-rate due to their presence is more than offset by an increase in heat transfer through additional turbulent mixing. It is also shown that array temperatures are strongly reduced by wind effects, which increase both the heat lost from the front surface of the array and by enhancement of the flow in the duct. Though the trends are clear, limitations are encountered in the present state of knowledge in both areas.

  • 4.
    Campana, Pietro Elia
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
    Wästhage, Louise
    Mälardalen Univ, Sch Business Soc & Engn, Future Energy Ctr, S-72123 Vasteras, Sweden..
    Nookuea, Worrada
    Mälardalen Univ, Sch Business Soc & Engn, Future Energy Ctr, S-72123 Vasteras, Sweden..
    Tan, Yuting
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
    Yan, Jinyue
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Energy Processes.
    Optimization and assessment of floating and floating-tracking PV systems integrated in on- and off-grid hybrid energy systems2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 177, p. 782-795Article in journal (Refereed)
    Abstract [en]

    Considering the targets of Thailand in terms of renewable energy exploitation and decarbonization of the shrimp farming sector, this work evaluates several scenarios for optimal integration of hybrid renewable energy systems into a representative shrimp farm. In particular, floating and floating-tracking PV systems are considered as alternatives for the exploitation of solar energy to meet the shrimp farm electricity demand. By developing a dynamic techno-economic simulation and optimization model, the following renewable energy systems have been evaluated: PV and wind based hybrid energy systems, off-grid and on-grid PV based hybrid energy systems, ground mounted and floating PV based hybrid energy systems, and floating and floating-tracking PV based hybrid energy systems. From a water-energy nexus viewpoint, floating PV systems have shown significant impacts on the reduction of evaporation losses, even if the energy savings for water pumping are moderate due to the low hydraulic head. Nevertheless, the study on the synergies between water for food and power production has highlighted that the integration of floating PV represents a key solution for reducing the environmental impacts of shrimp farming. For the selected location, the results have shown that PV systems represent the best renewable solution to be integrated into a hybrid energy system due to the abundance of solar energy resources as compared to the moderate wind resources. The integration of PV systems in off-grid configurations allows to reach high renewable reliabilities up to 40% by reducing the levelized cost of electricity. Higher renewable reliabilities can only be achieved by integrating energy storage solutions but leading to higher levelized cost of electricity. Although the floating-tracking PV systems show higher investment costs as compared to the reference floating PV systems, both solutions show similar competiveness for reliabilities up to 45% due to the higher electricity production of the floating-tracking PV systems. The higher electricity production from the floating-tracking PV systems leads to a better competitiveness for reliabilities higher than 90% due to lower capacity requirements for the storage systems.

  • 5.
    Chen, Yang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Pridasawas, Wimolsiri
    Lundqvist, Per
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Dynamic simulation of a solar-driven carbon dioxide transcritical power system for small scale combined heat and power production2010In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 7, p. 1103-1110Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide is an environmental benign natural working fluid and has been proposed as a working media for a solar-driven power system In the current work, the dynamic performance of a small scale solar-driven carbon dioxide power system is analyzed by dynamic simulation tool TRNSYS 16 (Klein et al., 2004) and Engineering Equation Solver (EES) (Klein, 2004) using co-solving technique Both daily performance and yearly performance of the proposed system have been simulated Different system operating parameters, which will influence the system performance, have been discussed. Under the Swedish climatic condition, the maximum daily power production is about 12 kW h and the maximum monthly power production is about 215 kW h with the proposed system working conditions Besides the power being produced, the system can also produce about 10 times much thermal energy. which can be used for space heating, domestic hot water supply or driving absorption chillers The simulation results show that the proposed system is a promising and environmental benign alternative for conventional low-grade heat source utilization system (C) 2010 Elsevier Ltd All rights reserved.

  • 6.
    Duarte, Willian M.
    et al.
    Federal University of Minas Gerais (UFMG).
    Paulinoc, Tiago F.
    Pabond, Juan J.G.
    Sawalha, Samer
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Machado, Luiz
    Refrigerants selection for a direct expansion solar assisted heat pump for domestic hot water2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 184, no May, p. 527-538Article in journal (Refereed)
    Abstract [en]

    An important step during a project of a heat pump system is choosing a more suitable refrigerant. This paper presents a comparative study among refrigerants for a small direct expansion solar assisted heat pump (DX-SAHP). The mathematical model used in this study is presented in detail and validated from an experimental setup. The R134a is the reference and the refrigerants with low GWP are R290, R600a, R744 and R1234yf. The results show that R290 has better COP than others refrigerants for solar radiation between 300 W/m2 and 700 W/m2, as well as for environment temperature between 10 C and 35 C. On the other hand, for solar radiation less than 50 W/m2, the R134a has better COP than R290. TEWI (Total Equivalent Warming Impact) analysis indicates that the indirect emission is the most important effect, and then, the TEWI results almost followed the COP outcome. A parametric analysis was conducted to evaluate the influence of the CO2 emission factor for producing electricity. In countries with higher emission factor, the refrigerant with the best COP has the best TEWI. The influence of wind speed and ambient temperature in COP of a DX-SAHP using R290 were more relevant in low solar radiation

    The full text will be freely available from 2021-04-01 15:14
  • 7. Ferruzza, D.
    et al.
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Haglind, F.
    Impact of steam generator start-up limitations on the performance of a parabolic trough solar power plant2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 169, p. 255-263Article in journal (Refereed)
    Abstract [en]

    Concentrating solar power plants are an attractive option in the renewable energy generation market. The possibility of integrating relatively cheap forms of energy storage makes them a desirable solution when power generation must be readily available at any time of the day. Solar power plants typically start-up and shut down every day, so in order to maximize their profitability, it is necessary to increase their flexibility in transient operation and to initiate power generation as rapidly as possible. Two of the key components are the steam generator and steam turbine and the rates at which they can reach operational speed are limited by thermo-mechanical constraints. This paper presents an analysis of the effects of the thermal stress limitations of the steam generator and steam turbine on the power plant start-up, and quantifies their impact on the economy of the system. A dynamic model of a parabolic trough power plant was developed and integrated with a logic controller to identify start-up limitations, and subsequently the dynamic model was integrated in a techno-economic tool previously developed by the authors. The plant was analysed under two different operating strategies, namely solar-driven and peak-load. The results indicate that for steam generator hot start-ups, a 1.5% increase in peak-load electricity production would be achieved by doubling the maximum allowable heating rate of the evaporator. No useful increase would be achieved by increasing the rates beyond a limit of 7–8 K/min, as the turbine would then be the main limiting component during start-up. Similar conclusions can be drawn for the solar-driven case, for which the solar field and the energy source availability would pose the major constraint when starting up the steam generator system.

  • 8.
    Ferruzza, Davide
    et al.
    Tech Univ Denmark, Dept Mech Engn, Nils Koppels Alle,Bldg 403, DK-2800 Lyngby, Denmark..
    Topel, Monika
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Haglind, Fredrik
    Tech Univ Denmark, Dept Mech Engn, Nils Koppels Alle,Bldg 403, DK-2800 Lyngby, Denmark..
    Optimal start-up operating strategies for gas-boosted parabolic trough solar power plants2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 176, p. 589-603Article in journal (Refereed)
    Abstract [en]

    Concentrating solar power plants are taking an increasing share in the renewable energy generation market. Parabolic trough is one of such technologies and the most commercially mature. However, this technology still suffers from technical challenges that need to be addressed. As these power plants experience daily start-up procedures, the optimal performance in transient operation needs to be considered. This paper presents a performance based modelling tool for a gas-boosted parabolic trough power plant. The objective of the paper is to define an optimal operational strategy of the power plant start-up procedure with the aim of minimizing its fuel consumption while at the same time maximizing its electric energy output, taking into account all the thermo-mechanical constraints involved in the procedure. Heating rate constraints of the steam generator and the booster heater, and the steam turbine start-up schedule were considered. The simulation model was developed based on a power plant located near Abu Dhabi, and was validated against real operational data with a maximum integral relative deviation of 4.3% for gross electric energy production. A multi-objective optimization was performed for a typical operating week during winter and spring weather conditions. The results suggest that in order to minimize the fuel consumption and at the same time maximize the electric energy production, an evaporator heating rate of 6 K/min is an optimal value both for winter and spring conditions.

  • 9.
    Garrido, Jorge
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Abou-Taouk, Abdallah
    Cleanergy, Regnbagsgatan 6, S-41755 Gothenburg, Sweden..
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Experimental and numerical performance analyses of a Dish-Stirling cavity receiver: Geometry and operating temperature studies2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, p. 913-923Article in journal (Refereed)
    Abstract [en]

    Higher performance cavity receivers are needed to increase the competitiveness of solar power plants. However, the design process needs to be improved with more relevant experimental and numerical analyses. Thereby, the performance of four different Dish-Stirling cavities is investigated experimentally analyzing the influence of the cavity aperture diameter and shape at various operating temperatures. Temperatures inside the cavity receiver were collected together with the electrical power produced by the engine-generator. Then, a thermal system simulation was modelled and a comprehensive multi-parameter and multi-operation validation was performed. To improve this validation, the temperature distribution across the receiver tubes was analyzed in order to relate temperatures on the irradiated region with the non-irradiated one, where thermocouples can measure. The simulations were later used to obtain cavity receiver efficiencies, temperatures and loss breakdowns. The results show that the cavity receiver must be studied in optimization processes in conjunction with the other system components. Moreover, the reverse-conical cavity was found to be more efficient than a nearly cylindrical shape. Regarding the cavity receiver thermal losses, radiation and natural convection present similar contributions in the system under study. Finally, it was found that thermocouples installed on a non-irradiated region can be used to obtain peak receiver temperatures if the measurements are rectified by a correction value proportional to the DNI.

  • 10.
    Hesaraki, Arefeh
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Halilovic, Armin
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Basic science.
    Holmberg, Sture
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
    Low-temperature Heat Emission Combined with Seasonal Thermal Storage and Heat Pump2015In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 119, p. 122-133Article in journal (Refereed)
    Abstract [en]

    We studied the application of a stratified seasonal hot water storage tank with a heat pump connected to medium-, low- and very-low-temperature space heat emissions for a single-family house in Stockholm, Sweden. Our aim was to investigate the influence of heat emission design temperature on the efficiency and design parameters of seasonal storage in terms of collector area, the ratio of storage volume to collector area (RVA), and the ratio of height to diameter of storage tank. For this purpose, we developed a mathematical model in MATLAB to predict hourly heat demand in the building, heat loss from the storage tank, solar collector heat production, and heat support by heat pump as a backup system when needed. In total, 108 cases were simulated with RVAs that ranged from 2 to 5 (m3 m−2), collector areas of 30, 40, and 50 (m2), height-to-diameter-of-storage-tank ratios of 1.0, 1.5, and 2.0 (m m1), and various heat emissions with design supply/return temperatures of 35/30 as very-low-, 45/35 as low-, and 55/45 (°C) as medium-temperature heat emission. In order to find the best combination based on heat emission, we considered the efficiency of the system in terms of the heat pump work considering coefficient of performance (COP) of the heat pump and solar fraction. Our results showed that, for all types of heat emission a storage-volume-to-collector area ratio of 5 m3 m2, with a collector area of 50 m2, and a height-to-diameter ratio of 1.0 m m1 were needed in order to provide the maximum efficiency. Results indicated that for very-low-temperature heat emission the heat pump work was less than half of that of the medium-temperature heat emission. This was due to 7% higher solar fraction and 14% higher COP of heat pump connected to very-low-temperature heat emission compared to medium-temperature heat emission.

  • 11. Kuang, Daibin
    et al.
    Comte, Pascal
    Zakeeruddin, Shaik M.
    Hagberg, Daniel P.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Karlsson, Karl Martin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Nazeeruddin, Md K.
    Grätzel, Michael
    Stable dye-sensitized solar cells based on organic chromophores and ionic liquid electrolyte2011In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 85, no 6, p. 1189-1194Article in journal (Refereed)
    Abstract [en]

    A series of polyene-diphenylaniline based organic dyes (coded as D5, D7, D9 and D11) have been reported for the application in ionic liquid electrolyte based dye-sensitized solar cells. The effects of substitution of organic dyes on the photovoltaic performance have been investigated, which show addition of methoxy groups on the triphenylamine donor group increases short-circuit current, open-circuit voltage and photovoltaic performance. A power conversion efficiency of 6.5% under AM 1.5 sunlight at 100 mW/cm(2) has been obtained with D11 dye in combination with a binary ionic liquid electrolyte, which when subjected to accelerated testing under one sun light soaking at 60 degrees C, the efficiency remained 90% of initial efficiency.

  • 12. Liu, X.
    et al.
    Xu, Miao
    Guo, J.
    Zhu, R.
    Numerical study on the energy performance of building zones with transparent water storage envelopes2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, p. 690-706Article in journal (Refereed)
    Abstract [en]

    Researches on water wall passive solar technologies, especially the numerical study on the energy performance of building zones with Transparent Water Storage Envelopes (TWSEs), are reported in this paper. TWSE is a climatic adaptive building envelope consisting of visually transparent modular water containers, exterior shading devices, water supply and return pipes. It is an upgraded water wall that can serve both as an energy efficient facade and an auxiliary water cistern in a building. Currently the energy simulation involving transparent water walls cannot be explicitly done in all energy simulation programs because transparent envelopes are always predefined as the surfaces without thermal mass due to the embedded algorithms complied with ISO15099 standard. A numerical approach based on the integrated energy and computational fluid dynamics (IE&CFD) simulation was developed for solving the energy simulation problem related with TWSEs. A simplified optical model of TWSE was proposed and validated through light transmission testing. Meanwhile, cooling and heating loads of a zone with TWSEs and conventional glazing in summer and winter months were studied. The thermal performance of a TWSE relative to the conventional glazing was also investigated via the comparative thermal box testing. Based on the simulation and testing results, it reveals that TWSEs can exceed most high performance coated glazing with regard to solar radiation control, and they are also exceptional energy efficient transparent envelopes that can outperform the ASHRAE standard window and conventional glazing in terms of cooling and heating load reduction as long as being configured and operated properly according to their physical characteristics and outdoor climatic condition. Furthermore, the innovative technical paradigm of TWSEs, along with the numerical approach developed for their energy simulation, demonstrates a wide range of versatility to be implemented in research and practice for ultra low energy buildings.

  • 13.
    Munkhammar, Joakim
    et al.
    Uppsala Universitet.
    Grahn, Pia
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Widén, Joakim
    Uppsala Universitet.
    Quantifying self-consumption of on-site photovoltaic power generation in households with electric vehicle home charging2013In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 97, p. 208-216Article in journal (Refereed)
    Abstract [en]

    Photovoltaic (PV) power production and residential power demand are negatively correlated at high latitudes on both annual and diurnal basis. If PV penetration levels increase, methods to deal with power overproduction in the local distribution grids are needed to avoid costly grid reinforcements. Increased local consumption is one such option. The introduction of a home-charged plug-in electric vehicle (PEV) has a significant impact on the household load and potentially changes the coincidence between household load and photovoltaic power production. This paper uses a stochastic model to investigate the effect on the coincidence between household load and photovoltaic power production when including a PEV load. The investigation is based on two system levels: (I) individual household level and (II) aggregate household level. The stochastic model produces theoretical high-resolution load profiles for household load and home charged PEV load over time. The photovoltaic power production model is based on high-resolution irradiance data for Uppsala, Sweden. It is shown that the introduction of a PEV improves the self-consumption of the photovoltaic power both on an individual and an aggregate level, but the increase is limited due to the low coincidence between the photovoltaic power production pattern and the charging patterns of the PEV.

  • 14.
    Pridasawas, Wimolsiri
    et al.
    KTH, Superseded Departments, Energy Technology.
    Lundqvist, Per G.
    KTH, Superseded Departments, Energy Technology.
    An exergy analysis of a solar-driven ejector refrigeration system2004In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 76, no 4, p. 369-379Article in journal (Refereed)
    Abstract [en]

    Energy analysis is used as a tool to analyse the performance of an ejector refrigeration cycle driven by solar energy. The analysis is based on the following conditions: a solar radiation of 700 W/m(2), an evaporator temperature of 10 degreesC, a cooling capacity of 5 kW, butane as the refrigerant in the refrigeration cycle and ambient temperature of 30 degreesC as the reference temperature. Irreversibilities occur among components and depend on the operating temperatures. The most significant losses in the system are in the solar collector and the ejector. The latter decreases inversely proportional to the evaporation temperature and dominates the total losses within the system. The optimum generating temperature for a specific evaporation temperature is obtained when the total losses in the system are minimized. For the above operating conditions, the optimum generating temperature is about 80 degreesC.

  • 15.
    Song, Xinkai
    et al.
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Yang, Xichuan
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Wang, Haoxin
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    An, Jincheng
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Yu, Ze
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Wang, Xiuna
    DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China..
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, CH-1015 Lausanne, Switzerland..
    Sun, Licheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry. DUT, DUT KTH Joint Educ & Res Ctr Mol Devices, State Key Lab Fine Chem, Inst Artificial Photosynth, 2 Linggong Rd, Dalian 116024, Peoples R China.
    Improving energy transfer efficiency of dye-sensitized solar cell by fine tuning of dye planarity2019In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 187, p. 274-280Article in journal (Refereed)
    Abstract [en]

    Two push-pull metal-free sensitizers with 5,11-dihydroindolo[3,2-b]carbazole derivatives as electron-donating groups and 4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)benzoic acid (BTZ) as electron-withdrawing unit, denoted by SK201 and SK202, were synthesized and used for fabrication of dye-sensitized solar cells (DSSCs). SK202 contains a thienyl group between the donor and acceptor, whereas in SK201 the donor and acceptor are connected directly by a single bond. Introduction of a thienyl group improved the planarity of the dye molecule, broadened the absorption spectrum, enhanced the molar extinction coefficient, increased the dye loading on TiO2, and accelerated interface electron transfer on TiO2. This fine tuning of dye structure improved the performances of DSSCs based on SK202 sensitizers and gave a power conversion efficiency (PCE) of 11.0% (J(SC) 16.5 mA cm(-2), V-OC 932 mV, and fill factor 71.7%), compared with that of 7.2% for SK201, under standard AM1.5G solar irradiation (100 mW cm(-2)) with a Co(II/III) complex based redox couple.

  • 16.
    Spelling, James
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Jöcker, Markus
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Martin, Andrew
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Annual performance improvement for solar steam turbines through the use of temperature-maintaining modifications2012In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 86, no 1, p. 496-504Article in journal (Refereed)
    Abstract [en]

    Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. By maintaining higher internal temperature during idle periods, faster start-up times can be achieved, increasing the flexibility of the plant as well as increasing net electrical production. Prior work by the authors identified a number of methods for achieving this, with strong increases in daily production predicted; only two specific start-up cases were studied however. In order to obtain a more representative evaluation of the performance increase that can be achieved through increased dispatchability of the turbine, the annual improvement needs to be studied. Building on the existing results, a dynamic system model of a parabolic trough power plant has been established and used to determine the distribution of different cool-down times experienced throughout the year, with a view to evaluating the potential annual production increase. A modification of the start-up curves allows an increase in annual electrical production between 6.4% and 2.4% depending upon the operating mode (free operation versus day-time operation). Through application of a combination of heat blankets and an increase in gland steam temperature, further annual production increases between 2.2% and 3.1% are predicted.

  • 17.
    Stojanovic, Bojan
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Hallberg, Daniel
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Akander, Jan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    A Steady State Thermal Duct Model Derived by Fin-Theory Approach and Applied on an Unglazed Solar Collector.2009In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 10, p. 1838-1851Article in journal (Refereed)
    Abstract [en]

    This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (ID) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler ID analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no 'or negligible' temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the ID isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of events adopts a 1D heat flow that reassembles the conditions of the 1D simple model (for the assessed USC duct geometry); ID heat flow through the top and bottom fins/sheets as the duct wall reassembles a state of adiabatic condition.

  • 18. Suehrcke, H.
    et al.
    Däldehög, David
    KTH.
    Harris, J. A.
    Lowe, R. W.
    Heat transfer across corrugated sheets and honeycomb transparent insulation2004In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 76, no 1-3, p. 351-358Article in journal (Refereed)
    Abstract [en]

    This paper describes the design of a simple guarded hot-plate apparatus for the measurement of heat transfer across transparent insulation. The apparatus is used to measure the heat transfer coefficient across a transparent corrugated (zigzag) sheet and honeycomb transparent insulation. The sheet and honeycomb are made from cellulose acetate film, which has high absorptance for long-wave thermal radiation and high transmittance for short-wave solar radiation. The corrugated sheet performs well, however, honeycomb transparent insulation of the same height and material appears to be superior due to greater thermal radiation blockage and better solar transmission characteristics. A numerical model for a honeycomb is developed which shows good agreement with the experimentally measured results.

  • 19.
    Topel, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Improving concentrating solar power plant performance by increasing steam turbine flexibility at start-up2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 165, p. 10-18Article in journal (Refereed)
    Abstract [en]

    Among concentrating solar power technologies, solar tower power plants currently represent one of the most promising ones. Direct steam generation systems, in particular, eliminate the usage of heat transfer fluids allowing for the power block to be run at greater operating temperatures and therefore further increasing the thermal efficiency of the power cycle. On the other hand, the current state of the art of these systems does not comprise thermal energy storage. The lack of storage adds to the already existing variability of operating conditions that all concentrating power plants endure due to the fluctuating nature of the solar supply. One way of improving this situation is increasing the operating flexibility of power block components to better adapt to the varying levels of solar irradiance. In particular, it is desirable for the plant to achieve fast start-up times in order to be available to harness as much solar energy as possible. However, the start-up speed of the whole plant is limited by the thermal inertia of certain key components, one of which is the steam turbine. This paper studies the potential for power plant performance improvement through the increase of steam turbine flexibility at the time of start-up. This has been quantified by carrying out power plant techno-economic studies in connection with steam turbine thermo-mechanic behavior analysis. Different turbine flexibility investigations involving the use of retrofitting measures to keep the turbine warmer during offline periods or changing the operating map of the turbine have been tested through multi-objective optimization considering annual power performance and operating costs. Results show that reductions of up to 11% on the levelized cost of electricity are possible through the implementation of these measures.

  • 20.
    Topel, Monika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Improving Concentrating Solar Power Plant Performance by Increasing Steam Turbine Flexibility at Start-up2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257Article in journal (Refereed)
    Abstract [en]

    Among concentrating solar power technologies, solar tower power plants currentlyrepresent one of the most promising ones. Direct steam generationsystems, in particular, eliminate the usage of heat transfer uids allowing forthe power block to be run at greater operating temperatures and thereforefurther increasing the thermal eciency of the power cycle. On the otherhand, the current state of the art of these systems does not comprise thermalenergy storage. The lack of storage adds to the already existing variability ofoperating conditions that all concentrating power plants endure due to theuctuating nature of the solar supply. One way of improving this situationis increasing the operating exibility of power block components to betteradapt to the varying levels of solar irradiance.In particular, it is desirable for the plant to achieve fast start-up times inorder to be available to harness as much solar energy as possible. However,the start-up speed of the whole plant is limited by the thermal inertia ofcertain key components, one of which is the steam turbine. This paperstudies the potential for power plant performance improvement through theincrease of steam turbine exibility at the time of start-up. This has beenquantied by carrying out power plant techno-economic studies in connectionwith steam turbine thermo-mechanic behavior analysis. Dierent turbineexibility investigations involving the use of retrotting measures to keep theturbine warmer during oine periods or changing the operating map of the turbine have been tested through multi-objective optimization consideringannual power performance and operating costs. Results show that reductionsof up to 11% on the levelized cost of electricity are possible through theimplementation of these measures, which in turn has a favorable impact onpower plant protability.

  • 21. Vadiee, Amir
    et al.
    Yaghoubi, Mahmoud
    Martin, Viktoria
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Bazargan-Lari, Yousef
    Energy analysis of solar blind system concept using energy system modelling2016In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 139, p. 297-308Article in journal (Refereed)
    Abstract [en]

    Energy conservation in the horticultural industry is one of the main challenging points regarding to the sustainable development. Commercial greenhouse is known as the most energy consuming and simultaneously the most effective cultivation method which promises 10 times more production yield than open field horticultural methods. Supplementary heating demand, electrical energy demand for artificial lighting system as well as active cooling systems are the main parameters which have to be reduced in order to have more energy efficient system. Usually, in the conventional greenhouse the solar radiation will blocked using a thermal screen to avoid the overheating problem and reduce the cooling demand. In this method, a large portion of solar irradiation will reflected and absorbed by curtain without any useful utilization. By introducing the solar blind system, the excess solar radiation will absorb and convert into useful thermal energy as well as electrical energy. As a matter of fact, the solar blind system consists of a series of thermal photovoltaic modules. The solar blind system will operate based on the defined set point temperature. By exceeding the greenhouse indoor temperature than set point temperature the solar blind thermal photovoltaic modules rotate over their axis to cover the greenhouse roof and block the solar radiation and it keeps blocking the solar irradiation until the indoor temperature drops below the set point. Therefore, the cooling demand will reduce considerably while the absorbed heat and electricity gain though the thermal photovoltaic cells can be utilized later to cover a part of the greenhouse thermal and electrical demand. The main aim of this paper is to assess the solar blind system performance for various set point temperatures. Therefore an energy model has to be developed and TRNSYS is used for this purpose. The results show that by considering 18 degrees C as the set point temperature, the highest thermal and electrical energy performance can be reached. The maximum thermal energy performance of the system is about 86% while the minimum that is corresponded to the highest set point temperature is 38%. By considering the solar blind system operated at 18 degrees C as the set point temperature, the cooling demand in the greenhouse can be almost covered totally, which is the main aim of this concept. However, the electrical demand is reduced almost by 73%. Additionally, by applying the solar blind system concept, the irradiation level inside the greenhouse kept in the optimal level that leads to more uniform cultivation during the whole year.

  • 22.
    Wang, Wujun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Aichmayer, Lukas
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Garrido, Jorge
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Development of a Fresnel lens based high-flux solar simulator2017In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 144, p. 436-444Article in journal (Refereed)
    Abstract [en]

    In this paper, a Fresnel lens based high flux solar simulator (HFSS) is developed for concentrating solar power research and high temperature material testing. In this design, each commercially available 7 kW(e) xenon-arc lamp is coupled with a silicone-on-glass Fresnel lenses as the optical concentrator, and 12 lamp-lens units are distributed in a circular array. In total, the power of the solar simulator can reach 84 kWe. A ray tracing model has been developed based on the real arc-emitter shape and the Fresnel lens optics for predicting the optical performance of the HFSS design. The testing result shows that the ray tracing model can predict the flux distribution on the focal plane accurately but a bit conservative in the center region. The flux distribution on the focal plane appears axisymmetric with a peak flux of 7.22 MW/m(2), and 19.7 kW of radiative power in total is delivered on a 280 mm diameter target. (C) 2017 Elsevier Ltd. All rights reserved.

  • 23.
    Wang, Wujun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Xu, Haoxin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Strand, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Conjugate heat transfer analysis of an impinging receiver design for a dish-Brayton system2015In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 119, p. 298-309Article in journal (Refereed)
    Abstract [en]

    An impinging receiver design has been developed for a small scale solar dish-Brayton system. A numerical conjugate heat transfer model combined with a ray-tracing model, based on the boundary conditions of the micro gas turbine and the EuroDish system, has been used for studying the thermal performance of an impinging receiver. According to the results of the preliminary estimation by an inverse design method, four possible impinging nozzle arrangements have been studied by the numerical model based on a 240 mm diameter and 3 mm wall thickness cavity. The inverse design method has been verified to be an efficient way in reducing the calculation costs during the design procedure. Furthermore, the impacts of the cavity diameter and the wall thickness have also been studied.

  • 24.
    Wang, Wujun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Wang, Bo
    Li, Lifeng
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Strand, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    The effect of the cooling nozzle arrangement to the thermal performance of a solar impinging receiver2016In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 131, p. 222-234Article in journal (Refereed)
    Abstract [en]

    The effect of the multi-row nozzle arrangement to the thermal performance of an impinging solar receiver is studied, and new governingequations are introduced for modifying the earlier introduced inverse design method. With the help of the modified inverse designmethod and a numerical conjugate heat transfer model, an impinging receiver based on stainless steel 253 MA material has been designedfor the combination of a micro gas turbine and the EuroDish collector system. At a DNI level of 800 W/m2, the average air temperatureat the outlet and the thermal efficiency can reach 1071.5 K and 82.7%. Furthermore, the temperature differences on the absorber can bereduced to 130 K and 149 K for two different DNI levels respectively. This represents a greatly improvement compared with other publishedcavity receiver designs.

  • 25.
    Wang, Wujun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Xu, Haoxin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Laumert, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Strand, Torsten
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    An inverse design method for a cavity receiver used in solar dish Brayton system2014In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 110, p. 745-755Article in journal (Refereed)
    Abstract [en]

    An inverse design method is developed in order to quickly find possible cavity receiver designs with relative uniform cavity wall surface temperature for a solar dish cavity receiver. In this design method, a heat transfer model of the absorber wall is used for analyzing the main heat transfer process between the cavity wall outer surface, the inner surface and the working fluid. Furthermore, a ray-tracing model based on the parameters of a real dish is utilized for obtaining the solar radiative boundary conditions for the heat transfer model. Impinging jet cooling technology is introduced due to its high heat transfer coefficient in the stagnation area, which can be used for cooling the peak flux on the cavity wall. After applying a well-designed impinging system, the temperature peak on the peak flux region in traditional receiver designs can be mitigated without introducing any over pressure drop problem.

  • 26.
    Yang, Xichuan
    et al.
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Wang, Weihan
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Zhang, Yanyun
    Dalian Univ Technol, State Key Lab Fine Chem, Linggong Rd 2, Dalian 116024, Liaoning, Peoples R China..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Improving the power conversion efficiency of solid state dye sensitized solar cells with a N-oxoammonium salt: 2,2,6,6-Tetramethyl-1-oxopiperidinebromide2018In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 170, p. 1001-1008Article in journal (Refereed)
    Abstract [en]

    P-type doping is a rational strategy for the enhancement of hole transporting properties of the organic semiconductors as well as the device performance of organic photo-electric devices. We originally introduce a stable and solution processed p-type dopant based on N-oxoammonium salts termed 2,2,6,6-tetramethyl-1-oxopiperidinebromide salt (TEMPO-Br) for 2,2',7,7'-tetrakis(N, N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (Spiro-OMeTAD) based solid state dye sensitized solar cells (ssDSC). By introducing TEMPO-Br doped Spiro-OMeTAD and a commercialized D-pi-A sensitizer into ssDSCs, a promising device performance of 6.83% is achieved under simulated AM 1.5G solar irradiation (100 mW cm(-2)), which is significantly better than the control devices ( similar to 1.7 times). The doping effect of TEMPO-Br on the photophysical and electrochemical properties of Spiro-OMeTAD, solid state device performance, cationic dye regeneration kinetics and preliminary long-term stability have been systematically investigated. This work indicates a potential application of N-oxoammonium salts as chemical P-type dopants for triphenylamine based hole transporting materials in solid state photo-electric devices.

  • 27. Zhang, Liang
    et al.
    Wang, Wujun
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Yu, Zitao
    Fan, Liwu
    Hu, Yacai
    Ni, Yu
    Fan, Jianren
    Cen, Kefa
    An experimental investigation of a natural circulation heat pipe system applied to a parabolic trough solar collector steam generation system2012In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 86, no 3, p. 911-919Article in journal (Refereed)
    Abstract [en]

    A U-type natural circulation heat pipe system is designed and applied to a parabolic trough solar collector for generating mid-temperature steam. Thermal performance of the heat pipe system is investigated experimentally. A detailed heat transfer analysis is performed on thermal behaviors of the system, especially the solar collector. The results show that the system can generate mid-temperature steam of a pressure up to 0.75 MPa. The thermal efficiency is found to be 38.52% at discharging pressure of 0.5 MPa during summer time.

1 - 27 of 27
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