The Experts below are selected from a list of 2478 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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on the value of liquid air and pumped thermal electricity storage systems in low carbon electricity systems
Energy, 2020Co-Authors: Solomos Georgiou, Marko Aunedi, Goran Strbac, Christos N MarkidesAbstract:Abstract We consider two medium-to-large scale thermomechanical electricity storage technologies currently under development, namely ‘Liquid-Air Energy Storage’ (LAES) and ‘Pumped-Thermal Electricity Storage’ (PTES). Consistent thermodynamic models and costing methods based on a unified methodology for the two systems from previous work are presented and used with the objective of integrating the characteristics of the technologies into a whole-electricity system assessment model and assessing their system-level value in various scenarios for system decarbonization. It is found that the value of storage depends on the cumulative installed capacity of storage in the system, with storage technologies providing greater marginal benefits at low penetrations. Two carbon target scenarios showed similar results, with a positive effect of more ambitious carbon targets on the system value of storage. The location and installed capacity of storage plants is found to have a significant impact on the system value and acceptable costs of both technologies. The system value of PTES was found to be slightly higher than that of LAES, driven by a higher storage duration and efficiency, although these results must be seen in light of the uncertainty in the (as yet, not demonstrated) performance of key PTES components, namely the Reciprocating-Piston compressors and expanders. At the same time, PTES was also found to have a higher power capital cost, which makes its deployment less economically attractive for implementation at lower volumes. The results indicate that the complexity of the decarbonization challenge makes it difficult to identify clearly a ‘best’ technology and suggest that the uptake of either technology can provide significant system-level benefits.
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A two-phase single-Reciprocating-Piston heat conversion engine: Non-linear dynamic modelling
Applied Energy, 2017Co-Authors: Christoph J.w. Kirmse, Aly I. Taleb, Oyeniyi A. Oyewunmi, Andrew J. Haslam, Christos N MarkidesAbstract:A non-linear dynamic framework is presented for the modelling of a novel two-phase heat engine termed ‘Up-THERM’, which features a single solid moving-part (Piston). When applied across the device, a constant temperature difference between an external (low- to medium-grade) heat source and an external heat sink is converted into sustained and persistent oscillations of pressure and volumetric fluid displacement. These oscillations are transformed in a load arrangement into a unidirectional flow from which power is extracted by a hydraulic motor. The Up-THERM engine is modelled using a system of first-order differential equations that describe the dominant thermal/fluid processes in each component of the device. For certain components where the deviations from a linear approximation are non-negligible (gas spring in the displacer cylinder, check valves and Piston valve, and heat exchangers), a non-linear description is employed. A comparison between the linear and non-linear descriptions of the gas spring at the top of the displacer cylinder reveals that the non-linear description results in more realistic predictions of the oscillation frequency compared to experimental data from a similar device. Furthermore, the shape of the temperature profile over the heat-exchanger surfaces is modelled as following a hyperbolic tangent function, based on findings from an experimental investigation. Following the validation of these important device components, a parametric study is performed on the Up-THERM engine model with the aforementioned non-linear component descriptions, aimed at investigating the effects of important geometric parameters and of the heat-source temperature on key performance indicators, namely the oscillation frequency, power output and exergy efficiency of the engine. The results indicate that the geometric design of the displacer cylinder, including the height of the gas spring at the top of the cylinder, and the heat-source temperature have the most significant influence on the performance of the engine. A maximum exergy efficiency of 2.8% and a maximum power output of 175W are observed at the proposed operating temperature of 450°C for a nominal Up-THERM design (based on the physical dimensions of a device prototype and water as the working fluid; the role of the working fluid is explored in follow-up paper Ref. [1]) but with shorter displacer cylinder gas-spring lengths relative to a nominal design. The results and insight can assist the further development of this technology, in particular as a prime mover in combined heat and power applications.
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working fluid selection and performance investigation of a two phase single Reciprocating Piston heat conversion engine
Applied Energy, 2017Co-Authors: Oyeniyi A. Oyewunmi, Christoph J.w. Kirmse, Andrew J. Haslam, Erich A Muller, Christos N MarkidesAbstract:Abstract We employ a validated first-order lumped dynamic model of the Up-THERM heat converter, a two-phase unsteady heat-engine that belongs to a class of innovative devices known as thermofluidic oscillators, which contain fewer moving parts than conventional engines and represent an attractive alternative for remote or off-grid power generation as well as waste-heat conversion applications. We investigate the performance of the Up-THERM with respect to working-fluid selection for its prospective applications. An examination of relevant working-fluid thermodynamic properties reveals that the saturation pressure and vapour-phase density of the fluid play important roles in determining the performance of the Up-THERM – the device delivers a higher power output at high saturation pressures and has higher exergy efficiencies at low vapour-phase densities. Furthermore, working fluids with low critical temperatures, high critical pressures and exhibiting high values of reduced pressures and temperatures result in designs with high power outputs. For a pre-specified Up-THERM design corresponding to a target (CHP prime-mover) application with a heat-source temperature of 360 °C, water is compared with 45 other pure working fluids. When maximizing the power output, R113 is identified as the optimal fluid, followed by i-hexane. Fluids such as siloxanes and heavier hydrocarbons are found to maximize the exergy and thermal efficiencies. The ability of the Up-THERM to convert heat over a range of heat-source temperatures is also investigated, and it is found that the device can deliver in excess of 10 kW when utilizing thermal energy at temperatures above 200 °C. Of all the working fluids considered here, ammonia, R245ca, R32, propene and butane feature prominently as optimal and versatile fluids delivering high power over a wide range of heat-source temperatures.
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a single Reciprocating Piston two phase thermofluidic prime mover
Energy, 2016Co-Authors: Aly I. Taleb, Michael A G Timmer, Mohammed Elshazly, Aleksandr Samoilov, Valeriy Kirillov, Christos N MarkidesAbstract:We explore theoretically a thermodynamic heat-engine concept that has the potential of attaining a high efficiency and power density relative to competing solutions, while having a simple construction with few moving parts and dynamic seals, allowing low capital and operating costs, and long lifetimes. Specifically, an unsteady heat-engine device within which a working fluid undergoes a power cycle featuring phase-change, termed the ‘Evaporative Reciprocating-Piston Engine’ (EPRE) is considered as a potential prime mover for use in combined heat and power (CHP) applications. Based on thermal/fluid-electrical analogies, a theoretical ERPE device is conceptualized initially in the electrical-analogy domain as a linearized, closed-loop active electronic circuit model. The circuit-model representation is designed to potentially exhibit high efficiencies compared to similar, existing two-phase unsteady heat engines. From the simplified circuit model in the electrical domain, and using the thermal/fluid-electrical analogies, one possible configuration of a corresponding physical ERPE device is derived, based on an early prototype of a device currently under development that exhibits some similarities with the ERPE, and used as a physical manifestation of the proposed concept. The corresponding physical ERPE device relies on the alternating phase change of a suitable working-fluid (here, water) to drive a Reciprocating displacement of a single vertical Piston and to produce sustained oscillations of thermodynamic properties within an enclosed space. Four performance indicators are considered: the operational frequency, the power output, the exergy efficiency, and the heat input/temperature difference imposed externally on the device's heat exchangers that is necessary to sustain oscillations. The effects of liquid inertia, viscous drag, hydrostatic pressure, vapour compressibility and two-phase heat transfer in the various engine components/compartments are examined, via changes to thermodynamic/thermophysical/transport properties and also geometrical features of the ERPE. It is found that for high efficiency and power output: (1) the vapour dead-spaces must be minimized; (2) the length of the tube that connects the displacer and working cylinders must be of significant length; and, (3) the heat-exchanger blocks must have a low thermal resistance and high heat capacity. The methodological approach implemented in this study can be used to guide the proposal, early-stage design and verification of these complex unsteady thermodynamic systems, while offering important suggestions for improved performance and system optimization.
Christoph J.w. Kirmse - One of the best experts on this subject based on the ideXlab platform.
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A two-phase single-Reciprocating-Piston heat conversion engine: Non-linear dynamic modelling
Applied Energy, 2017Co-Authors: Christoph J.w. Kirmse, Aly I. Taleb, Oyeniyi A. Oyewunmi, Andrew J. Haslam, Christos N MarkidesAbstract:A non-linear dynamic framework is presented for the modelling of a novel two-phase heat engine termed ‘Up-THERM’, which features a single solid moving-part (Piston). When applied across the device, a constant temperature difference between an external (low- to medium-grade) heat source and an external heat sink is converted into sustained and persistent oscillations of pressure and volumetric fluid displacement. These oscillations are transformed in a load arrangement into a unidirectional flow from which power is extracted by a hydraulic motor. The Up-THERM engine is modelled using a system of first-order differential equations that describe the dominant thermal/fluid processes in each component of the device. For certain components where the deviations from a linear approximation are non-negligible (gas spring in the displacer cylinder, check valves and Piston valve, and heat exchangers), a non-linear description is employed. A comparison between the linear and non-linear descriptions of the gas spring at the top of the displacer cylinder reveals that the non-linear description results in more realistic predictions of the oscillation frequency compared to experimental data from a similar device. Furthermore, the shape of the temperature profile over the heat-exchanger surfaces is modelled as following a hyperbolic tangent function, based on findings from an experimental investigation. Following the validation of these important device components, a parametric study is performed on the Up-THERM engine model with the aforementioned non-linear component descriptions, aimed at investigating the effects of important geometric parameters and of the heat-source temperature on key performance indicators, namely the oscillation frequency, power output and exergy efficiency of the engine. The results indicate that the geometric design of the displacer cylinder, including the height of the gas spring at the top of the cylinder, and the heat-source temperature have the most significant influence on the performance of the engine. A maximum exergy efficiency of 2.8% and a maximum power output of 175W are observed at the proposed operating temperature of 450°C for a nominal Up-THERM design (based on the physical dimensions of a device prototype and water as the working fluid; the role of the working fluid is explored in follow-up paper Ref. [1]) but with shorter displacer cylinder gas-spring lengths relative to a nominal design. The results and insight can assist the further development of this technology, in particular as a prime mover in combined heat and power applications.
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working fluid selection and performance investigation of a two phase single Reciprocating Piston heat conversion engine
Applied Energy, 2017Co-Authors: Oyeniyi A. Oyewunmi, Christoph J.w. Kirmse, Andrew J. Haslam, Erich A Muller, Christos N MarkidesAbstract:Abstract We employ a validated first-order lumped dynamic model of the Up-THERM heat converter, a two-phase unsteady heat-engine that belongs to a class of innovative devices known as thermofluidic oscillators, which contain fewer moving parts than conventional engines and represent an attractive alternative for remote or off-grid power generation as well as waste-heat conversion applications. We investigate the performance of the Up-THERM with respect to working-fluid selection for its prospective applications. An examination of relevant working-fluid thermodynamic properties reveals that the saturation pressure and vapour-phase density of the fluid play important roles in determining the performance of the Up-THERM – the device delivers a higher power output at high saturation pressures and has higher exergy efficiencies at low vapour-phase densities. Furthermore, working fluids with low critical temperatures, high critical pressures and exhibiting high values of reduced pressures and temperatures result in designs with high power outputs. For a pre-specified Up-THERM design corresponding to a target (CHP prime-mover) application with a heat-source temperature of 360 °C, water is compared with 45 other pure working fluids. When maximizing the power output, R113 is identified as the optimal fluid, followed by i-hexane. Fluids such as siloxanes and heavier hydrocarbons are found to maximize the exergy and thermal efficiencies. The ability of the Up-THERM to convert heat over a range of heat-source temperatures is also investigated, and it is found that the device can deliver in excess of 10 kW when utilizing thermal energy at temperatures above 200 °C. Of all the working fluids considered here, ammonia, R245ca, R32, propene and butane feature prominently as optimal and versatile fluids delivering high power over a wide range of heat-source temperatures.
Oyeniyi A. Oyewunmi - One of the best experts on this subject based on the ideXlab platform.
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A two-phase single-Reciprocating-Piston heat conversion engine: Non-linear dynamic modelling
Applied Energy, 2017Co-Authors: Christoph J.w. Kirmse, Aly I. Taleb, Oyeniyi A. Oyewunmi, Andrew J. Haslam, Christos N MarkidesAbstract:A non-linear dynamic framework is presented for the modelling of a novel two-phase heat engine termed ‘Up-THERM’, which features a single solid moving-part (Piston). When applied across the device, a constant temperature difference between an external (low- to medium-grade) heat source and an external heat sink is converted into sustained and persistent oscillations of pressure and volumetric fluid displacement. These oscillations are transformed in a load arrangement into a unidirectional flow from which power is extracted by a hydraulic motor. The Up-THERM engine is modelled using a system of first-order differential equations that describe the dominant thermal/fluid processes in each component of the device. For certain components where the deviations from a linear approximation are non-negligible (gas spring in the displacer cylinder, check valves and Piston valve, and heat exchangers), a non-linear description is employed. A comparison between the linear and non-linear descriptions of the gas spring at the top of the displacer cylinder reveals that the non-linear description results in more realistic predictions of the oscillation frequency compared to experimental data from a similar device. Furthermore, the shape of the temperature profile over the heat-exchanger surfaces is modelled as following a hyperbolic tangent function, based on findings from an experimental investigation. Following the validation of these important device components, a parametric study is performed on the Up-THERM engine model with the aforementioned non-linear component descriptions, aimed at investigating the effects of important geometric parameters and of the heat-source temperature on key performance indicators, namely the oscillation frequency, power output and exergy efficiency of the engine. The results indicate that the geometric design of the displacer cylinder, including the height of the gas spring at the top of the cylinder, and the heat-source temperature have the most significant influence on the performance of the engine. A maximum exergy efficiency of 2.8% and a maximum power output of 175W are observed at the proposed operating temperature of 450°C for a nominal Up-THERM design (based on the physical dimensions of a device prototype and water as the working fluid; the role of the working fluid is explored in follow-up paper Ref. [1]) but with shorter displacer cylinder gas-spring lengths relative to a nominal design. The results and insight can assist the further development of this technology, in particular as a prime mover in combined heat and power applications.
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working fluid selection and performance investigation of a two phase single Reciprocating Piston heat conversion engine
Applied Energy, 2017Co-Authors: Oyeniyi A. Oyewunmi, Christoph J.w. Kirmse, Andrew J. Haslam, Erich A Muller, Christos N MarkidesAbstract:Abstract We employ a validated first-order lumped dynamic model of the Up-THERM heat converter, a two-phase unsteady heat-engine that belongs to a class of innovative devices known as thermofluidic oscillators, which contain fewer moving parts than conventional engines and represent an attractive alternative for remote or off-grid power generation as well as waste-heat conversion applications. We investigate the performance of the Up-THERM with respect to working-fluid selection for its prospective applications. An examination of relevant working-fluid thermodynamic properties reveals that the saturation pressure and vapour-phase density of the fluid play important roles in determining the performance of the Up-THERM – the device delivers a higher power output at high saturation pressures and has higher exergy efficiencies at low vapour-phase densities. Furthermore, working fluids with low critical temperatures, high critical pressures and exhibiting high values of reduced pressures and temperatures result in designs with high power outputs. For a pre-specified Up-THERM design corresponding to a target (CHP prime-mover) application with a heat-source temperature of 360 °C, water is compared with 45 other pure working fluids. When maximizing the power output, R113 is identified as the optimal fluid, followed by i-hexane. Fluids such as siloxanes and heavier hydrocarbons are found to maximize the exergy and thermal efficiencies. The ability of the Up-THERM to convert heat over a range of heat-source temperatures is also investigated, and it is found that the device can deliver in excess of 10 kW when utilizing thermal energy at temperatures above 200 °C. Of all the working fluids considered here, ammonia, R245ca, R32, propene and butane feature prominently as optimal and versatile fluids delivering high power over a wide range of heat-source temperatures.
Andrew J. Haslam - One of the best experts on this subject based on the ideXlab platform.
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A two-phase single-Reciprocating-Piston heat conversion engine: Non-linear dynamic modelling
Applied Energy, 2017Co-Authors: Christoph J.w. Kirmse, Aly I. Taleb, Oyeniyi A. Oyewunmi, Andrew J. Haslam, Christos N MarkidesAbstract:A non-linear dynamic framework is presented for the modelling of a novel two-phase heat engine termed ‘Up-THERM’, which features a single solid moving-part (Piston). When applied across the device, a constant temperature difference between an external (low- to medium-grade) heat source and an external heat sink is converted into sustained and persistent oscillations of pressure and volumetric fluid displacement. These oscillations are transformed in a load arrangement into a unidirectional flow from which power is extracted by a hydraulic motor. The Up-THERM engine is modelled using a system of first-order differential equations that describe the dominant thermal/fluid processes in each component of the device. For certain components where the deviations from a linear approximation are non-negligible (gas spring in the displacer cylinder, check valves and Piston valve, and heat exchangers), a non-linear description is employed. A comparison between the linear and non-linear descriptions of the gas spring at the top of the displacer cylinder reveals that the non-linear description results in more realistic predictions of the oscillation frequency compared to experimental data from a similar device. Furthermore, the shape of the temperature profile over the heat-exchanger surfaces is modelled as following a hyperbolic tangent function, based on findings from an experimental investigation. Following the validation of these important device components, a parametric study is performed on the Up-THERM engine model with the aforementioned non-linear component descriptions, aimed at investigating the effects of important geometric parameters and of the heat-source temperature on key performance indicators, namely the oscillation frequency, power output and exergy efficiency of the engine. The results indicate that the geometric design of the displacer cylinder, including the height of the gas spring at the top of the cylinder, and the heat-source temperature have the most significant influence on the performance of the engine. A maximum exergy efficiency of 2.8% and a maximum power output of 175W are observed at the proposed operating temperature of 450°C for a nominal Up-THERM design (based on the physical dimensions of a device prototype and water as the working fluid; the role of the working fluid is explored in follow-up paper Ref. [1]) but with shorter displacer cylinder gas-spring lengths relative to a nominal design. The results and insight can assist the further development of this technology, in particular as a prime mover in combined heat and power applications.
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working fluid selection and performance investigation of a two phase single Reciprocating Piston heat conversion engine
Applied Energy, 2017Co-Authors: Oyeniyi A. Oyewunmi, Christoph J.w. Kirmse, Andrew J. Haslam, Erich A Muller, Christos N MarkidesAbstract:Abstract We employ a validated first-order lumped dynamic model of the Up-THERM heat converter, a two-phase unsteady heat-engine that belongs to a class of innovative devices known as thermofluidic oscillators, which contain fewer moving parts than conventional engines and represent an attractive alternative for remote or off-grid power generation as well as waste-heat conversion applications. We investigate the performance of the Up-THERM with respect to working-fluid selection for its prospective applications. An examination of relevant working-fluid thermodynamic properties reveals that the saturation pressure and vapour-phase density of the fluid play important roles in determining the performance of the Up-THERM – the device delivers a higher power output at high saturation pressures and has higher exergy efficiencies at low vapour-phase densities. Furthermore, working fluids with low critical temperatures, high critical pressures and exhibiting high values of reduced pressures and temperatures result in designs with high power outputs. For a pre-specified Up-THERM design corresponding to a target (CHP prime-mover) application with a heat-source temperature of 360 °C, water is compared with 45 other pure working fluids. When maximizing the power output, R113 is identified as the optimal fluid, followed by i-hexane. Fluids such as siloxanes and heavier hydrocarbons are found to maximize the exergy and thermal efficiencies. The ability of the Up-THERM to convert heat over a range of heat-source temperatures is also investigated, and it is found that the device can deliver in excess of 10 kW when utilizing thermal energy at temperatures above 200 °C. Of all the working fluids considered here, ammonia, R245ca, R32, propene and butane feature prominently as optimal and versatile fluids delivering high power over a wide range of heat-source temperatures.
Fredrik Haglind - One of the best experts on this subject based on the ideXlab platform.
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Experimental and numerical analysis of a Reciprocating Piston expander with variable valve timing for small-scale organic Rankine cycle power systems
Applied Energy, 2019Co-Authors: Jorrit Wronski, Muhammad Imran, Morten Juel Skovrup, Fredrik HaglindAbstract:Abstract This paper presents a Reciprocating expander concept for organic Rankine cycle applications using a novel rotating variable timing admission valve system, enabling the adjustment of the expansion ratio in real time while the expander is running. An organic Rankine cycle experimental test rig with n-pentane as the working fluid and a single-cylinder Reciprocating Piston expander was developed. Experiments were conducted for evaporation temperatures ranging from 125 °C to 150 °C and condensation temperatures ranging from 20 °C to 40 °C. The performance of the Reciprocating Piston expander was investigated in terms of the torque of the expander, pressure inside the cylinder, isentropic efficiency of the expander, and net power produced by the expander. Based on the experimental data, a dynamic model of the system was formulated in the object-oriented language, Modelica. The model was validated using the experimental results and then used to predict the performance of the expander. Special attention was paid to the robust modelling of the valve actuation to avoid computational inefficiencies caused by singularities of state variables or their derivatives. The results indicate that the expander produces up to 2.5 kW of electricity from a low-temperature heat source while operating at pressure ratios ranging from 10 to 16.5 with an isentropic efficiency of approximately 70%. The relative differences between the model and the measurements of the isentropic efficiency and power output of the expander per revolution were ±10% and ±30%, respectively.