The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
Christos N Markides - One of the best experts on this subject based on the ideXlab platform.
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Working fluid selection and Electrical performance optimisation of a domestic solar orc combined heat and power system for year round operation in the uk
Applied Energy, 2017Co-Authors: James Freeman, Klaus Hellgardt, Christos N MarkidesAbstract:In this paper, we examine the Electrical power-generation potential of a domestic-scale solar combined heating and power (S-CHP) system featuring an organic Rankine cycle (ORC) engine and a 15-m2 non-concentrated solar-thermal collector array. The system is simulated with a range of organic Working fluids and its performance is optimised for operation in the UK climate. The findings are applicable to similar geographical locations with significant cloud coverage, a low solar resource and limited installation areas. A key feature of the system’s design is the implementation of fixed fluid flow-rates during operation in order to avoid penalties in the performance of components suffered at part-load. Steady operation under varying solar irradiance conditions is provided by way of a Working-fluid buffer vessel at the evaporator outlet, which is maintained at the evaporation temperature and pressure of the ORC. By incorporating a two-stage solar collector/evaporator configuration, a maximum net annual Electrical Work output of 1070kWhyr−1 (continuous average power of 122W) and a solar-to-Electrical efficiency of 6.3% is reported with HFC-245ca as the Working fluid at an optimal evaporation saturation temperature of 126°C (corresponding to an evaporation pressure of 16.2bar). This is equivalent to ∼32% of the electricity demand of a typical/average UK home, and represents an improvement of more than 50% over a recent effort by the same authors based on an earlier S-CHP system configuration and HFC-245fa as the Working fluid [1], thus highlighting the gains possible when using optimal system configurations and fluids and suggesting that significant further improvements may be possible. A performance and simple cost comparison with stand-alone, side-by-side PV and solar-thermal heating systems is presented.
John H Lienhard - One of the best experts on this subject based on the ideXlab platform.
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primary energy and exergy of desalination technologies in a power water cogeneration scheme
Applied Energy, 2019Co-Authors: Thomas Altmann, Justin Robert, Andrew Thomas Bouma, Jaichander Swaminathan, John H LienhardAbstract:Abstract The primary energy consumption of a spectrum of desalination systems is assessed using operating information and technical bids for real plants configured with coproduction of electricity. The energy efficiency of desalination plants is often rated on a stand-alone basis using metrics such as specific energy consumption, gained output ratio, and second law efficiency, which can lead to inconsistent conclusions because the heat and Electrical Work inputs to the plant have very different exergies and costs, which must be taken into account. When both the heat and Work inputs are drawn from a common primary energy source, such as the fuel provided to electricity-water coproduction systems, these inputs can be compared and combined if they are traced back to primary energy use. In the present study, we compare 48 different configurations of electricity production and desalination on the basis of primary energy use, including cases with pretreatment and hybridized systems, using performance figures from real and quoted desalination systems operating in the GCC region. The results show that, while reverse osmosis is still the most energy efficient desalination technology, the gap between Work and thermally driven desalination technologies is reduced when considered on the basis of primary energy. The results also show that pretreatment with nanofiltration or hybridization of multiple desalination systems can help to reduce energy requirements. Additionally, the specific type of power plant in the coproduction scheme and its operating parameters can have a significant impact on the performance of desalination technologies relative to one other.
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thermodynamic analysis of a reverse osmosis desalination system using forward osmosis for energy recovery
ASME 2012 International Mechanical Engineering Congress and Exposition, 2012Co-Authors: Leonardo David Anchik, John H LienhardAbstract:Thermodynamic analysis is applied to assess the energy efficiency of hybrid desalination cycles that are driven by simultaneous mixed inputs, including heat, Electrical Work, and chemical energy. A seawater desalination cycle using Work and a chemical input stream is analyzed using seawater properties. Two system models, a reversible separator and an irreversible component based model, are developed to find the least Work required to operate the system with and without osmotic recovery. The component based model represents a proposed desalination system which uses a reverse osmosis membrane for solute separation, a pressure exchanger for recovering a fraction of the flow Work associated with the pressurized discharge brine, and a forward osmosis (FO) module for recovering some of the chemical energy contained within the concentrated discharge brine. The energy attained by the addition of the chemical input stream serves to lower the amount of Electrical Work required for operation. For this analysis, a wastewater stream of varying solute concentration, ranging from feed to brackish water salinity, is considered as the chemical stream. Unlike other models available in the literature, the FO exchanger is numerically simulated as a mass exchanger of given size which accounts for changing stream concentration, and consequently, stream-wise variations of osmotic pressure throughout the length of the unit. A parametric study is performed on the models by varying input conditions. For the reversible case it is found that significant Work reductions can be made through the use of an energy recovery device when the inlet wastewater salinity used is less than the feed salinity of 35 g/kg. For the irreversible case with a typical recovery ratio and feed salinity, significant Work reductions were only noted for a wastewater inlet of less than half of the feed salinity due to pump Work losses. In the irreversible case, the use of a numerical model to simulate the FO exchanger resulted in a maximum Work reduction when the pressure difference between streams was around one half of the osmotic pressure difference as opposed to the precise value of one half found in zero-dimensional exchanger models.Copyright © 2012 by ASME
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thermodynamic analysis of a reverse osmosis desalination system using forward osmosis for energy recovery
Prof. Lienhard via Angie Locknar, 2012Co-Authors: Leonardo David Anchik, John H LienhardAbstract:Thermodynamic analysis is applied to assess the energy efficiency of hybrid desalination cycles that are driven by simultaneous mixed inputs, including heat, Electrical Work, and chemical energy. A seawater desalination cycle using Work and a chemical input stream is analyzed using seawater properties. Two system models, a reversible separator and an irreversible component based model, are developed to find the least Work required to operate the system with and without osmotic recovery. The component based model represents a proposed desalination system which uses a reverse osmosis membrane for solute separation, a pressure exchanger for recovering a fraction of the flow Work associated with the pressurized discharge brine, and a forward osmosis (FO) module for recovering some of the chemical energy contained within the concentrated discharge brine. The energy attained by the addition of the chemical input stream serves to lower the amount of Electrical Work required for operation. For this analysis, a wastewater stream of varying solute concentration, ranging from feed to brackish water salinity, is considered as the chemical stream. Unlike other models available in the literature, the FO exchanger is numerically simulated as a mass exchanger of given size which accounts for changing stream concentration, and consequently, stream-wise variations of osmotic pressure throughout the length of the unit. A parametric study is performed on the models by varying input conditions. For the reversible case it is found that significant Work reductions can be made through the use of an energy recovery device when ∗Address all correspondence to this author. the inlet wastewater salinity used is less than the feed salinity of 35 g/kg. For the irreversible case with a typical recovery ratio and feed salinity, significant Work reductions were only noted for a wastewater inlet of less than half of the feed salinity due to pump Work losses. In the irreversible case, the use of a numerical model to simulate the FO exchanger resulted in a maximum Work reduction when the pressure difference between streams was around one half of the osmotic pressure difference as opposed to the precise value of one half found in zero-dimensional exchanger models. NOMENCLATURE Roman symbols Units g specific Gibbs free energy kJ/kg h specific enthalpy kJ/kg ṁ mass flow rate kg solution/s m∗ dimensionless mass flow rate ratio P pressure bar P∗ dimensionless pressure ratio pr permeation ratio Q heat transfer rate kW r recovery ratio s specific entropy kJ/kg-K T temperature oC w salinity mass fraction g solute/kg solution Ẇ Work rate kW
James Freeman - One of the best experts on this subject based on the ideXlab platform.
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Working fluid selection and Electrical performance optimisation of a domestic solar orc combined heat and power system for year round operation in the uk
Applied Energy, 2017Co-Authors: James Freeman, Klaus Hellgardt, Christos N MarkidesAbstract:In this paper, we examine the Electrical power-generation potential of a domestic-scale solar combined heating and power (S-CHP) system featuring an organic Rankine cycle (ORC) engine and a 15-m2 non-concentrated solar-thermal collector array. The system is simulated with a range of organic Working fluids and its performance is optimised for operation in the UK climate. The findings are applicable to similar geographical locations with significant cloud coverage, a low solar resource and limited installation areas. A key feature of the system’s design is the implementation of fixed fluid flow-rates during operation in order to avoid penalties in the performance of components suffered at part-load. Steady operation under varying solar irradiance conditions is provided by way of a Working-fluid buffer vessel at the evaporator outlet, which is maintained at the evaporation temperature and pressure of the ORC. By incorporating a two-stage solar collector/evaporator configuration, a maximum net annual Electrical Work output of 1070kWhyr−1 (continuous average power of 122W) and a solar-to-Electrical efficiency of 6.3% is reported with HFC-245ca as the Working fluid at an optimal evaporation saturation temperature of 126°C (corresponding to an evaporation pressure of 16.2bar). This is equivalent to ∼32% of the electricity demand of a typical/average UK home, and represents an improvement of more than 50% over a recent effort by the same authors based on an earlier S-CHP system configuration and HFC-245fa as the Working fluid [1], thus highlighting the gains possible when using optimal system configurations and fluids and suggesting that significant further improvements may be possible. A performance and simple cost comparison with stand-alone, side-by-side PV and solar-thermal heating systems is presented.
Ibrahim Dincer - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic modeling of a nuclear energy based integrated system for hydrogen production and liquefaction
Computers & Chemical Engineering, 2016Co-Authors: Hasan Ozcan, Ibrahim DincerAbstract:Abstract A nuclear based integrated system for hydrogen production and liquefaction with a newly developed four-step magnesium–chlorine cycle is proposed. The system uses nuclear energy to supply heat for the Rankine cycle and Mg–Cl cycle, where the power produced by the Rankine cycle is used to run the electrolysis steps of the Mg–Cl cycle and liquefaction cycle compressors. The four-step Mg–Cl cycle is specifically designed to decrease the Electrical Work consumption of the cycle by capturing HCl in dry form with an additional step to conventional three-step cycle. A performance assessment study is undertaken based on energy and exergy analysis of the subsystems, and total energy and exergy efficiencies of the plant are found to be 18.6%, and 31.35%. The comparisons of the subsystem efficiencies and total exergy destructions show that highest irreversibility ratio belongs to the Mg–Cl cycle by 41%, respectively.
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thermodynamic analysis of the use a chemical heat pump to link a supercritical water cooled nuclear reactor and a thermochemical water splitting cycle for hydrogen production
Journal of Power and Energy Systems, 2008Co-Authors: Mikhail Granovskii, Ibrahim Dincer, Marc A Rosen, Igor PioroAbstract:Increases in the power generation efficiency of nuclear power plants (NPPs) are mainly limited by the permissible temperatures in nuclear reactors and the corresponding temperatures and pressures of the coolants in reactors. Coolant parameters are limited by the corrosion rates of materials and nuclear-reactor safety constraints. The advanced construction materials for the next generation of CANDU reactors, which employ supercritical water (SCW) as a coolant and heat carrier, permit improved “steam” parameters (outlet temperatures up to 625°C and pressures of about 25 MPa). An increase in the temperature of steam allows it to be utilized in thermochemical water splitting cycles to produce hydrogen. These methods are considered by many to be among the most efficient ways to produce hydrogen from water and to have advantages over traditional low-temperature water electrolysis. However, even lower temperature water splitting cycles (Cu-Cl, UT-3, etc.) require an intensive heat supply at temperatures higher than 550-600°C. A sufficient increase in the heat transfer from the nuclear reactor to a thermochemical water splitting cycle, without jeopardizing nuclear reactor safety, might be effectively achieved by application of a heat pump, which increases the temperature of the heat supplied by virtue of a cyclic process driven by mechanical or Electrical Work. Here, a high-temperature chemical heat pump, which employs the reversible catalytic methane conversion reaction, is proposed. The reaction shift from exothermic to endothermic and back is achieved by a change of the steam concentration in the reaction mixture. This heat pump, coupled with the second steam cycle of a SCW nuclear power generation plant on one side and a thermochemical water splitting cycle on the other, increases the temperature of the “nuclear” heat and, consequently, the intensity of heat transfer into the water splitting cycle. A comparative preliminary thermodynamic analysis is conducted of the combined system comprising a SCW nuclear power generation plant and a chemical heat pump, which provides high-temperature heat to a thermochemical water splitting cycle for hydrogen production. It is concluded that the proposed chemical heat pump permits the utilization efficiency of nuclear energy to be improved by at least 2% without jeopardizing nuclear reactor safety. Based on this analysis, further research appears to be merited on the proposed advanced design of a nuclear power generation plant combined with a chemical heat pump, and implementation in appropriate applications seems worthwhile.
Klaus Hellgardt - One of the best experts on this subject based on the ideXlab platform.
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Working fluid selection and Electrical performance optimisation of a domestic solar orc combined heat and power system for year round operation in the uk
Applied Energy, 2017Co-Authors: James Freeman, Klaus Hellgardt, Christos N MarkidesAbstract:In this paper, we examine the Electrical power-generation potential of a domestic-scale solar combined heating and power (S-CHP) system featuring an organic Rankine cycle (ORC) engine and a 15-m2 non-concentrated solar-thermal collector array. The system is simulated with a range of organic Working fluids and its performance is optimised for operation in the UK climate. The findings are applicable to similar geographical locations with significant cloud coverage, a low solar resource and limited installation areas. A key feature of the system’s design is the implementation of fixed fluid flow-rates during operation in order to avoid penalties in the performance of components suffered at part-load. Steady operation under varying solar irradiance conditions is provided by way of a Working-fluid buffer vessel at the evaporator outlet, which is maintained at the evaporation temperature and pressure of the ORC. By incorporating a two-stage solar collector/evaporator configuration, a maximum net annual Electrical Work output of 1070kWhyr−1 (continuous average power of 122W) and a solar-to-Electrical efficiency of 6.3% is reported with HFC-245ca as the Working fluid at an optimal evaporation saturation temperature of 126°C (corresponding to an evaporation pressure of 16.2bar). This is equivalent to ∼32% of the electricity demand of a typical/average UK home, and represents an improvement of more than 50% over a recent effort by the same authors based on an earlier S-CHP system configuration and HFC-245fa as the Working fluid [1], thus highlighting the gains possible when using optimal system configurations and fluids and suggesting that significant further improvements may be possible. A performance and simple cost comparison with stand-alone, side-by-side PV and solar-thermal heating systems is presented.