The Experts below are selected from a list of 1002 Experts worldwide ranked by ideXlab platform
José M. Martínez-val - One of the best experts on this subject based on the ideXlab platform.
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Dual Loop line-focusing solar power plants with supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on proposing the combination of a Dual Loop solar field, with Dowtherm A and the Solar Salt as heat transfer fluids in parabolic or linear Fresnel solar Collectors, coupled to supercritical Carbon Dioxide (s-CO2) Brayton power cycle. The Dual-Loop justification relies on gaining the synergies provided by the different heat transfer fluids properties. The oils advantages are related with the operating experience accumulated in numerous solar power plants deployed around the World, assuring the commercial equipment availability. Also the pipes metal corrosion with oil is much lower than with molten salt. The pipes material cost saving is significant with the oil alternative. The thermal oil main constraint is imposed by the maximum operating temperature (around 400 °C) for avoiding chemical decomposition and degradation, stablishing the plant threshold efficiency 37% due to Carnot principle. On the other hand the Solar Salt mixture (60%NaNO3 40%KNO3) maximum operating temperature goes up to 550 °C, but the freezing point is stablished around 220 °C requiring pipes and equipment electrical heating for avoiding salts solidification at low temperature. Regarding the balance of plant, the s-CO2 power cycle is the most promising alternative to the actual Rankine power cycle for increasing the plant energy efficiency, reducing the solar Collector Aperture area and minimizing the equipment dimensions and civil work. Three Brayton cycles configurations with reheating were assessed integrated with the line-focusing Dual-Loop solar field: the simple Brayton cycle (SB), the Recompression cycle (RC), the Partial Cooling with Recompression cycle (PCRC), and the Recompression with Main Compression Intercooling (RCMCI). The power cycle operating thermodynamic parameters (split flow, reheating pressure, mass flow and pressure ratio) were optimized with unconstrained multivariable algorithms: SUBPLEX, UOBYQA and NEWUOA. The main conclusion deducted is the significant efficiency improvement when adopting the s-CO2 Brayton cycle in comparison with the Rankine legacy solution. The Dual-Loop solar field integrated with a Rankine cycle provides a gross efficiency around 41.8%, but when coupling to s-CO2 Brayton RC or RCMCI the plant efficiency goes up to ≈50%. It was also demonstrated the beneficial effect of increasing the total heat exchangers (recuperators) conductance (UA) for optimizing the Brayton cycles efficiency and minimizing the solar field Aperture area for a fixed power output, only limited by the minimum pinch point temperature in heat exchangers.
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New text comparison between CO2 and other supercritical working fluids (ethane, Xe, CH4 and N2) in line- focusing solar power plants coupled to supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on comparing four supercritical fluids: Ethane, Xenon, Methane and Nitrogen, as possible alternative to supercritical Carbon Dioxide (s-CO2) in Brayton power cycles coupled to line- focusing solar power plants with Solar Salt (60% NaNO3; 40% KNO3) as heat transfer fluid. The Simple Brayton cycle with heat recuperation and reheating is the configuration selected in this paper, providing a balance of plant design with reduced number of equipment and cost. The gross plant efficiency is calculated fixing the recuperator conductance (UA) for different Turbine Inlet Temperatures (TIT), confirming the maximum plant gross efficiency is related with the minimum allowable recuperator pinch point temperature. The reheating pressure and compressor inlet temperature are optimized with the mathematical algorithms SUBPLEX, UOBYQA and NEWOUA. According to the REFPROP database ranges of applicability, the maximum TIT limits are established for the supercritical fluids (N2 TIT = 550 °C, CO2 TIT = 550 °C, C2H6 TIT = 400 °C, Xe TIT = 450 °C and CH4 TIT = 350 °C). The reference scenario considered for calculating the thermosolar plant energy balances and simulations is the wet-cooling system with a Compressor Inlet Temperature (CIT = 32 °C). The gross efficiency results with the wet-cooling system are: N2 (45.8%), CO2 (44.37%), C2H6 (40.74%), Xe (39.88%), CH4 (32.15%). The plant efficiency is also translated into solar field effective Aperture area and estimated cost, for a fixed power output. For optimizing the solar Collector Aperture area and cost, the Primary Heat Exchanger (PHX) and the ReHeating Heat Exchanger (RHX) capacity ratio (CR) are fixed (CR = 1). The dry-cooling system scenario (CIT = 47 °C) is alto estimated: N2 (43.34%), CO2 (42.42%), C2H6 (37.34%), Xe (37.26%), CH4 (29.53%). For predicting the recuperator heat exchanger dimensions for a fixed conductance (UA), the heat transfer coefficient (HTC) is calculated with the Dittus–Boelter correlation and compared with the CO2 as reference. The C2H6, and CH4 have relative higher HTC in relation with CO2. Also is calculated the recuperator pressure drop. The C2H6, CH4 and N2 pressure drop is lower in comparison with the CO2 for the same operating conditions. The energy efficiency in solar power station coupled to Brayton cycle is very constrained by the ambient temperature variation, impacting directly in the dry-cooling system performance. For this reason a Compressor Inlet Temperature (CIT) sensing analysis is carried out ranging from 32 °C to 57 °C, and also varying TIT from 400 °C to 550 °C. A sensing analysis is also developed varying the Turbine Inlet Pressure (TIP) from 200 bar to 375 bar. The CO2 improves the plant efficiency when increasing the TIP from 250 bar to 350 bar, however the rest of fluids (Ethane, Methane, Nitrogen and Xenon) nearly not suffered any impact in the plant efficiency when increasing the TIP.
L. Coco-enríquez - One of the best experts on this subject based on the ideXlab platform.
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Dual Loop line-focusing solar power plants with supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on proposing the combination of a Dual Loop solar field, with Dowtherm A and the Solar Salt as heat transfer fluids in parabolic or linear Fresnel solar Collectors, coupled to supercritical Carbon Dioxide (s-CO2) Brayton power cycle. The Dual-Loop justification relies on gaining the synergies provided by the different heat transfer fluids properties. The oils advantages are related with the operating experience accumulated in numerous solar power plants deployed around the World, assuring the commercial equipment availability. Also the pipes metal corrosion with oil is much lower than with molten salt. The pipes material cost saving is significant with the oil alternative. The thermal oil main constraint is imposed by the maximum operating temperature (around 400 °C) for avoiding chemical decomposition and degradation, stablishing the plant threshold efficiency 37% due to Carnot principle. On the other hand the Solar Salt mixture (60%NaNO3 40%KNO3) maximum operating temperature goes up to 550 °C, but the freezing point is stablished around 220 °C requiring pipes and equipment electrical heating for avoiding salts solidification at low temperature. Regarding the balance of plant, the s-CO2 power cycle is the most promising alternative to the actual Rankine power cycle for increasing the plant energy efficiency, reducing the solar Collector Aperture area and minimizing the equipment dimensions and civil work. Three Brayton cycles configurations with reheating were assessed integrated with the line-focusing Dual-Loop solar field: the simple Brayton cycle (SB), the Recompression cycle (RC), the Partial Cooling with Recompression cycle (PCRC), and the Recompression with Main Compression Intercooling (RCMCI). The power cycle operating thermodynamic parameters (split flow, reheating pressure, mass flow and pressure ratio) were optimized with unconstrained multivariable algorithms: SUBPLEX, UOBYQA and NEWUOA. The main conclusion deducted is the significant efficiency improvement when adopting the s-CO2 Brayton cycle in comparison with the Rankine legacy solution. The Dual-Loop solar field integrated with a Rankine cycle provides a gross efficiency around 41.8%, but when coupling to s-CO2 Brayton RC or RCMCI the plant efficiency goes up to ≈50%. It was also demonstrated the beneficial effect of increasing the total heat exchangers (recuperators) conductance (UA) for optimizing the Brayton cycles efficiency and minimizing the solar field Aperture area for a fixed power output, only limited by the minimum pinch point temperature in heat exchangers.
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New text comparison between CO2 and other supercritical working fluids (ethane, Xe, CH4 and N2) in line- focusing solar power plants coupled to supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on comparing four supercritical fluids: Ethane, Xenon, Methane and Nitrogen, as possible alternative to supercritical Carbon Dioxide (s-CO2) in Brayton power cycles coupled to line- focusing solar power plants with Solar Salt (60% NaNO3; 40% KNO3) as heat transfer fluid. The Simple Brayton cycle with heat recuperation and reheating is the configuration selected in this paper, providing a balance of plant design with reduced number of equipment and cost. The gross plant efficiency is calculated fixing the recuperator conductance (UA) for different Turbine Inlet Temperatures (TIT), confirming the maximum plant gross efficiency is related with the minimum allowable recuperator pinch point temperature. The reheating pressure and compressor inlet temperature are optimized with the mathematical algorithms SUBPLEX, UOBYQA and NEWOUA. According to the REFPROP database ranges of applicability, the maximum TIT limits are established for the supercritical fluids (N2 TIT = 550 °C, CO2 TIT = 550 °C, C2H6 TIT = 400 °C, Xe TIT = 450 °C and CH4 TIT = 350 °C). The reference scenario considered for calculating the thermosolar plant energy balances and simulations is the wet-cooling system with a Compressor Inlet Temperature (CIT = 32 °C). The gross efficiency results with the wet-cooling system are: N2 (45.8%), CO2 (44.37%), C2H6 (40.74%), Xe (39.88%), CH4 (32.15%). The plant efficiency is also translated into solar field effective Aperture area and estimated cost, for a fixed power output. For optimizing the solar Collector Aperture area and cost, the Primary Heat Exchanger (PHX) and the ReHeating Heat Exchanger (RHX) capacity ratio (CR) are fixed (CR = 1). The dry-cooling system scenario (CIT = 47 °C) is alto estimated: N2 (43.34%), CO2 (42.42%), C2H6 (37.34%), Xe (37.26%), CH4 (29.53%). For predicting the recuperator heat exchanger dimensions for a fixed conductance (UA), the heat transfer coefficient (HTC) is calculated with the Dittus–Boelter correlation and compared with the CO2 as reference. The C2H6, and CH4 have relative higher HTC in relation with CO2. Also is calculated the recuperator pressure drop. The C2H6, CH4 and N2 pressure drop is lower in comparison with the CO2 for the same operating conditions. The energy efficiency in solar power station coupled to Brayton cycle is very constrained by the ambient temperature variation, impacting directly in the dry-cooling system performance. For this reason a Compressor Inlet Temperature (CIT) sensing analysis is carried out ranging from 32 °C to 57 °C, and also varying TIT from 400 °C to 550 °C. A sensing analysis is also developed varying the Turbine Inlet Pressure (TIP) from 200 bar to 375 bar. The CO2 improves the plant efficiency when increasing the TIP from 250 bar to 350 bar, however the rest of fluids (Ethane, Methane, Nitrogen and Xenon) nearly not suffered any impact in the plant efficiency when increasing the TIP.
Spyros Voutetakis - One of the best experts on this subject based on the ideXlab platform.
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Novel and conventional working fluid mixtures for solar Rankine cycles: Performance assessment and multi-criteria selection
Applied Thermal Engineering, 2015Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:Abstract This work investigates the performance of working fluid mixtures for use in solar ORC (Organic Rankine Cycle systems) with heat storage employing FPC (Flat Plate Collectors). Several mixtures are considered including conventional choices often utilized in ORC as well as novel mixtures previously designed using advanced computer aided molecular design methods (Papadopoulos et al., 2013). The impact of heat source variability on the ORC performance is assessed for different working fluid mixtures. Solar radiation is represented in detail through actual, hourly averaged data for an entire year. A multi-criteria mixture selection methodology unveils important trade-offs among several important system operating parameters and efficiently highlights optimum operating ranges. Such parameters include the ORC thermal efficiency, the net generated power, the volume ratio across the turbine, the mass flow rate of the ORC working fluid, the evaporator temperature glide, the temperature drop in the storage tank, the ORC total yearly operating duration, the required Collector Aperture area to generate 1 kW of power and the irreversibility. A mixture of neopentane – 2-fluoromethoxy-2-methylpropane at 70% neopentane is found to be the most efficient in all the considered criteria simultaneously.
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Assessment of Working Fluid Mixtures for Solar Organic Rankine Cycles
Chemical engineering transactions, 2014Co-Authors: Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:This work investigates the performance of binary working fluid mixtures in a low temperature solar Organic Rankine Cycle (ORC) system including heat storage. Conventional mixtures widely considered in published literature are compared with optimum mixtures previously obtained using a computer-aided molecular design method in Papadopoulos et al. (2013). The system performance is investigated for a real solar radiation profile for an entire year of operation. Inclusive, steady-state mathematical models are used for the simulation of both the solar Collectors and the ORC. The effects of different mixtures on several important system operating parameters are investigated. Results indicate that mixtures at different compositions and concentrations may have a significantly different performance in terms of parameters such as generated work, required Collector Aperture area and so forth. Neopentanebased mixtures appear as promising candidates of high overall performance for solar ORCs.
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Assessment of Working Fluid Mixtures for Solar Organic
2014Co-Authors: Cal E, Paschalia Mavrou, Athanasios I. Papadopoulos, Mirko Stijepovic, Panos Seferlis, Patrick Linke, Spyros VoutetakisAbstract:This work investigates the performance of binary working fluid mixtures in a low temperature solar Organic Rankine Cycle (ORC) system including heat storage. Conventional mixtures widely considered in published literature are compared with optimum mixtures previously obtained using a computer-aided molecular design method in Papadopoulos et al. (2013). The system performance is investigated for a real solar radiation profile for an entire year of operation. Inclusive, steady-state mathematical models are used for the simulation of both the solar Collectors and the ORC. The effects of different mixtures on several important system operating parameters are investigated. Results indicate that mixtures at different compositions and concentrations may have a significantly different performance in terms of parameters such as generated work, required Collector Aperture area and so forth. Neopentane- based mixtures appear as promising candidates of high overall performance for solar ORCs.
Javier Muñoz-antón - One of the best experts on this subject based on the ideXlab platform.
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Dual Loop line-focusing solar power plants with supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on proposing the combination of a Dual Loop solar field, with Dowtherm A and the Solar Salt as heat transfer fluids in parabolic or linear Fresnel solar Collectors, coupled to supercritical Carbon Dioxide (s-CO2) Brayton power cycle. The Dual-Loop justification relies on gaining the synergies provided by the different heat transfer fluids properties. The oils advantages are related with the operating experience accumulated in numerous solar power plants deployed around the World, assuring the commercial equipment availability. Also the pipes metal corrosion with oil is much lower than with molten salt. The pipes material cost saving is significant with the oil alternative. The thermal oil main constraint is imposed by the maximum operating temperature (around 400 °C) for avoiding chemical decomposition and degradation, stablishing the plant threshold efficiency 37% due to Carnot principle. On the other hand the Solar Salt mixture (60%NaNO3 40%KNO3) maximum operating temperature goes up to 550 °C, but the freezing point is stablished around 220 °C requiring pipes and equipment electrical heating for avoiding salts solidification at low temperature. Regarding the balance of plant, the s-CO2 power cycle is the most promising alternative to the actual Rankine power cycle for increasing the plant energy efficiency, reducing the solar Collector Aperture area and minimizing the equipment dimensions and civil work. Three Brayton cycles configurations with reheating were assessed integrated with the line-focusing Dual-Loop solar field: the simple Brayton cycle (SB), the Recompression cycle (RC), the Partial Cooling with Recompression cycle (PCRC), and the Recompression with Main Compression Intercooling (RCMCI). The power cycle operating thermodynamic parameters (split flow, reheating pressure, mass flow and pressure ratio) were optimized with unconstrained multivariable algorithms: SUBPLEX, UOBYQA and NEWUOA. The main conclusion deducted is the significant efficiency improvement when adopting the s-CO2 Brayton cycle in comparison with the Rankine legacy solution. The Dual-Loop solar field integrated with a Rankine cycle provides a gross efficiency around 41.8%, but when coupling to s-CO2 Brayton RC or RCMCI the plant efficiency goes up to ≈50%. It was also demonstrated the beneficial effect of increasing the total heat exchangers (recuperators) conductance (UA) for optimizing the Brayton cycles efficiency and minimizing the solar field Aperture area for a fixed power output, only limited by the minimum pinch point temperature in heat exchangers.
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New text comparison between CO2 and other supercritical working fluids (ethane, Xe, CH4 and N2) in line- focusing solar power plants coupled to supercritical Brayton power cycles
International Journal of Hydrogen Energy, 2017Co-Authors: L. Coco-enríquez, Javier Muñoz-antón, José M. Martínez-valAbstract:Abstract This study is focused on comparing four supercritical fluids: Ethane, Xenon, Methane and Nitrogen, as possible alternative to supercritical Carbon Dioxide (s-CO2) in Brayton power cycles coupled to line- focusing solar power plants with Solar Salt (60% NaNO3; 40% KNO3) as heat transfer fluid. The Simple Brayton cycle with heat recuperation and reheating is the configuration selected in this paper, providing a balance of plant design with reduced number of equipment and cost. The gross plant efficiency is calculated fixing the recuperator conductance (UA) for different Turbine Inlet Temperatures (TIT), confirming the maximum plant gross efficiency is related with the minimum allowable recuperator pinch point temperature. The reheating pressure and compressor inlet temperature are optimized with the mathematical algorithms SUBPLEX, UOBYQA and NEWOUA. According to the REFPROP database ranges of applicability, the maximum TIT limits are established for the supercritical fluids (N2 TIT = 550 °C, CO2 TIT = 550 °C, C2H6 TIT = 400 °C, Xe TIT = 450 °C and CH4 TIT = 350 °C). The reference scenario considered for calculating the thermosolar plant energy balances and simulations is the wet-cooling system with a Compressor Inlet Temperature (CIT = 32 °C). The gross efficiency results with the wet-cooling system are: N2 (45.8%), CO2 (44.37%), C2H6 (40.74%), Xe (39.88%), CH4 (32.15%). The plant efficiency is also translated into solar field effective Aperture area and estimated cost, for a fixed power output. For optimizing the solar Collector Aperture area and cost, the Primary Heat Exchanger (PHX) and the ReHeating Heat Exchanger (RHX) capacity ratio (CR) are fixed (CR = 1). The dry-cooling system scenario (CIT = 47 °C) is alto estimated: N2 (43.34%), CO2 (42.42%), C2H6 (37.34%), Xe (37.26%), CH4 (29.53%). For predicting the recuperator heat exchanger dimensions for a fixed conductance (UA), the heat transfer coefficient (HTC) is calculated with the Dittus–Boelter correlation and compared with the CO2 as reference. The C2H6, and CH4 have relative higher HTC in relation with CO2. Also is calculated the recuperator pressure drop. The C2H6, CH4 and N2 pressure drop is lower in comparison with the CO2 for the same operating conditions. The energy efficiency in solar power station coupled to Brayton cycle is very constrained by the ambient temperature variation, impacting directly in the dry-cooling system performance. For this reason a Compressor Inlet Temperature (CIT) sensing analysis is carried out ranging from 32 °C to 57 °C, and also varying TIT from 400 °C to 550 °C. A sensing analysis is also developed varying the Turbine Inlet Pressure (TIP) from 200 bar to 375 bar. The CO2 improves the plant efficiency when increasing the TIP from 250 bar to 350 bar, however the rest of fluids (Ethane, Methane, Nitrogen and Xenon) nearly not suffered any impact in the plant efficiency when increasing the TIP.
Vicente Romero-ternero - One of the best experts on this subject based on the ideXlab platform.
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Preliminary design of a solar thermal-powered seawater reverse osmosis system
Desalination, 2007Co-Authors: Agustín M. Delgado-torres, Lourdes García-rodríguez, Vicente Romero-terneroAbstract:Abstract This paper presents a preliminary design for a solar thermal-powered reverse osmosis desalination system. The high pressure pump in the seawater reverse osmosis unit requires a 95-kW input, while the reject energy is recovered by way of pressure exchangers. The unit's specific energy consumption is 6.48 MJ/m3 (1.8 kWh/m3) for a recovery rate close to 50% and a feed pressure of 5.53 MPa. The unit was coupled to a solar power cycle based on a Rankine cycle with toluene, hexamethyldisiloxane (MM) and octamethylcyclotetrasiloxane (D4) as working fluids and two different models of parabolic trough Collectors. In addition, configurations using both direct vapor generation as well as a heat transfer fluid are proposed. The coupling was done assuming all the mechanical energy produced by the cycle was consumed by the high pressure pump in the reverse osmosis unit. A subsequent assumption was that all the cycle's rejected thermal energy went to preheat the seawater feed flow. This latter aspect does not result in a significant increase in the desalinated water output. The results obtained indicate that with the system proposed it is possible to produce, for a solar direct irradiance of 850 W/m2, 0.11 m3/h with toluene as the working fluid in the cycle and 0.088–0.094 m3/h with D4 or MM of desalinated water per square meter of LS3s parabolic trough Collector Aperture area. Likewise, for the IND300 Collector, it is possible to obtain 0.078–0.085 m3/h with toluene and 0.07–0.077 m3/h with D4 or MM.