Solar-driven Heat Engine Research Articles

Thermodynamic Analysis and Multi-Objective Optimization of Solar Heat Engines

Detailed performance analysis for a thermal system using a generalized irreversible solar-driven heat engine model is performed. The heat engine (HE) model is formed by the first and the second laws of thermodynamics and economical considerations. Also, the HE is optimized under the thermo-economic objective function (TEOF), power output, and overall efficiency criteria. The TEOF is used to evaluate the investment, including lost exergy, and operating and maintenance costs together. It is defined as the power output per unit total cost. In the HE model, investment and operating and maintenance costs are regarded as proportional to the power output of the heat engine, while lost exergy cost is regarded as proportional to the entropy generation rate. In thermal system designs, various scenarios are considered regarding size and configuration limits. To fulfill the requirements, performance output parameters can be evaluated with weighing factors. In the HE model, the hot surface heat transfer mechanisms are considered as both radiation and convection, but the cold surface heat transfer mechanism is considered as convection, only. Also, the thermo-economic performance is evaluated considering heat losses. Besides overall efficiency and operational temperatures of the hot working fluid have been discoursed in detail. HE model performance data and optimized results are computed numerically. And finally, an artificial neural network model is presented for an alternative solution to compute HE performance data with less effort and less input data.

A comparative thermo-ecological performance analysis of generalized irreversible solar-driven heat engines

In this study, an analysis based upon thermo-ecology criteria has been performed for an irreversible solar-driven heat engine. In the conceived heat engine, heat is transferred by using simultaneous radiation and convection mode from the source at high temperature to the heat engine side and by using convection mode from the heat engine to the source at low temperature. The influences of the optimization variables on the thermo-ecologic performance have been observed by using the ecologic objective function and the ecological coefficient of performance (ECOP). Also various performance factors of the heat engine, such as thermal efficiency, power output, loss rate of availability and temperatures of the working fluid have been discussed in detail by considering the maximum ecological coefficient of performance, maximum ecological function and maximum power output conditions. The entropy generation rate at maximum ECOP is less than at maximum ecologic objective function conditions, while the power output at maximum ECOP is less than at maximum ecologic objective function conditions.

COMPARISON OF EFFICIENCY OF A SOLAR DRIVEN CARNOT ENGINE UNDER MAXIMUM POWER AND POWER DENSITY CONDITIONS

A comparative analysis on thermodynamic efficiency based on maximum power & power density conditions have been performed for a solar-driven Carnot heat engine with internal irreversibility. In this analysis, the heat transfer from the hot reservoir is to be in the radiation mode and the heat transfer to the cold reservoir is to be in the convection mode. The thermodynamic efficiency function, power & power density functions have been derived and maximization of the power functions have been performed for various design parameters. From the optimum conditions, the thermal efficiencies at maximum power and power densities have been obtained. The effects of internal irreversibility, extreme temperature ratios & specific engine size in area ratio between the hot & cold reservoirs as various design parameters on thermodynamic efficiencies have been investigated for both the conditions. The efficiencies have been compared with Curzon- Ahlborn & Carnot efficiencies respectively. The analysis showed that the efficiency at maximum power output is greater than the efficiency at maximum power density. And the efficiencies can be greater than the Curzon- Ahlborn`s efficiency only for low values of design parameters.

Thermo-economic modeling and optimization of an irreversible solar-driven heat engine

The present paper illustrates a new thermo-economic performance analysis of an irreversible solar-driven heat engine. Moreover, aforementioned irreversible solar-driven heat engine is optimized by employing thermo-economic functions. With the help of the first and second laws of thermodynamics, an equivalent system is initially specified. To assess this goal, three objective functions that the normalized objective function associated to the power output (FP) and Normalized ecological function (FE) and thermal efficiency (ηth) are involved in optimization process simultaneously. Three objective functions are maximized at the same time. A multi objective evolutionary approaches (MOEAs) on the basis of NSGA-II method is employed in this work.

Optimal Design of a Solar-Driven Heat Engine Based on Thermal and Ecological Criteria

AbstractOptimal thermal and ecological performance tests of a solar-driven heat engine system were conducted in various optimization scenarios. For this, thermal and ecological models were develope...

Optimal design of a solar driven heat engine based on thermal and thermo-economic criteria

To study the optimum design factors and the optimal thermo-economical performances an optimal performance analysis of a solar driven heat engine system at maximum thermo-economical objective function conditions is done numerically. In the present investigation, thermodynamic analysis and NSGAII algorithm are employed to optimize objective function associated to the power output, thermal efficiency for a Solar driven engine system. Three decision-making procedures are applied to optimized answers from the results. The error through investigation is shown using error analysis.

Exergetic, environmental and economic analyses of small-capacity concentrated solar-driven heat engines for power and heat cogeneration

In this paper, the exergy interactions, environmental impact in terms of CO2 mitigation, and the economics of small-capacity concentrated solar power-driven heat engines for power and heat generation are analysed for residential applications. Starting from a base case study that assumes mass production in Ontario, it is shown that the investment in such a system, making use of a heat engine and having 9 m2 of aperture area, could be about CN$10 000 for a peak electrical efficiency of 18% and thermal efficiency of 75%. The average CO2 mitigation due to combined savings in electricity and heat is ∼0.3 kgCO2 kWh−1, a figure 3–4 times larger than for photovoltaic panels. If 25% government subsidy to the investment is provided, the payback period becomes 21.6 years. Additionally, if the financing benefits from a feed-in-tariff program (at 25% electrical sell-back to the grid) and deductions from CO2 tax are realized, then the payback time drops to 11.3 years. These results are obtained for a conservative scenario of 5.5% annual incremental increase in energy price. For the moderate consideration of all factors, it is shown that within the financial savings over the entire lifecycle, 7% are due to carbon tax, 30% are due to electrical production and the largest amount, 63%, is the result of reducing the natural gas heating capacity with solar heating from the proposed system. Copyright © 2011 John Wiley & Sons, Ltd.

Finite-Time Thermoeconomic Optimization of a Solar-Driven Heat Engine Model

In the present paper, the thermoeconomic optimization of an irreversible solar-driven heat engine model has been carried out by using finite-time/finite-size thermodynamic theory. In our study we take into account losses due to heat transfer across finite time temperature differences, heat leakage between thermal reservoirs and internal irreversibilities in terms of a parameter which comes from the Clausius inequality. In the considered heat engine model, the heat transfer from the hot reservoir to the working fluid is assumed to be Dulong-Petit type and the heat transfer to the cold reservoir is assumed of the Newtonian type. In this work, the optimum performance and two design parameters have been investigated under two objective functions: the power output per unit total cost and the ecological function per unit total cost. The effects of the technical and economical parameters on the thermoeconomic performance have been also discussed under the aforementioned two criteria of performance.

Investigation on the optimal performance and design parameters of an irreversible solar-driven Braysson heat engine

An irreversible solar-driven Braysson thermal engine has been investigated, in which finite rate heat transfer with the radiation–convection mode from the high-temperature reservoir to the heat engine and the convection mode from the heat engine to the heat sink, and irreversible adiabatic processes are taken into account. Based on the thermodynamic analysis method, the analytic expressions of the power output and efficiency of the Braysson heat engine are derived. By using numerical value calculation, the effects of the isobaric temperature ratio, internal irreversibility parameter, temperature ratio of the thermal reservoirs as well as the allocation parameters involving the heat-transfer coefficients, and areas on the performance characteristics of the Braysson heat engine are analysed and discussed in detail. The results obtained in this paper are more general than the related conclusions published in the literature and may provide some parameter design reference for solar-driven heat engines.

Thermoeconomic Optimum Operation Conditions of a Solar-driven Heat Engine Model

In the present paper, the thermoeconomic optimization of an endoreversible solardriven heat engine has been carried out by using finite-time/finite-size thermodynamic theory. In the considered heat engine model, the heat transfer from the hot reservoir to the working fluid is assumed to be the radiation type and the heat transfer to the cold reservoir is assumed the conduction type. In this work, the optimum performance and two design parameters have been investigated under three objective functions: the power output per unit total cost, the efficient power per unit total cost and the ecological function per unit total cost. The effects of the technical and economical parameters on the thermoeconomic performance have been also discussed under the aforementioned three criteria of performance.

Parametric optimization of a solar-driven Braysson heat engine with variable heat capacity of the working fluid and radiation–convection heat losses

An irreversible solar-driven Braysson heat engine system is presented, in which the temperature-dependent heat capacity of the working fluid, the radiation–convection heat losses of the solar collector and the irreversibilities resulting from heat transfer and non-isentropic compression and expansion processes are taken into account. Based on the thermodynamic analysis method and the optimal control theory, the mathematical expression of the overall efficiency of the system is derived and the maximum overall efficiency is calculated, and the operating temperatures of the solar collector and the cyclic working fluid and the ratio of heat-transfer areas of the heat engine are optimized. By using numerical optimization technology, the influences of the variable heat capacity of the working fluid, the radiation–convection heat losses of the solar collector and the multi-irreversibilities on the performance characteristics of the solar-driven heat engine system are investigated and evaluated in detail. Moreover, it is expounded that the optimal performance and important parametric bounds of the irreversible solar-driven Braysson heat engine with the constant heat capacity of the working fluid and the irreversible solar-driven Carnot heat engine can be deduced from the conclusions in the present paper.

The effect of heat loss on the performance of a solar-driven heat engine

An optimal performance analysis of a parabolic-trough direct-steam-generation solar-driven Rankine cycle power plant at maximum power (MP) and under maximum power density (MPD) conditions is performed numerically to investigate the effects of heat loss from the heat source and working fluid. In this study, the ideal Rankine cycle of the solar-driven power plant is modified into an equivalent Carnot-like cycle with a finite-rate heat transfer. The main assumptions of this study include that: (a) the parabolic collector is the thermal reservoir at a high temperature, (b) the heat transfer process between the collector and the working fluid is through either radiation and convection simultaneously or radiation only, and (c) the heat transfer process from the working fluid to the low-temperature thermal reservoir is convection dominated. Comprehensive discussions on the effect of heat loss during the heat transfer process from the hot thermal reservoir to the working fluid in the parabolic-trough solar collector are provided. The major results of this study can be summarized as follows: (a) the working fluid temperature at the hot-side heat exchanger decreases remarkably whereas the working fluid temperature at the cold-side heat exchanger does not show any significant change with increasing heat loss, (b) the MP, MPD, and thermal efficiencies decrease with increasing heat loss, and (c) the effect of heat loss on the decrease of thermal efficiency increases when convection is the dominant heat transfer mode at the hot-side heat exchanger.

A unified model of combined energy systems with different cycle modes and its optimum performance characteristics

A unified model is presented for a class of combined energy systems, in which the systems mainly consist of a heat engine, a combustor and a counter-flow heat exchanger and the heat engine in the systems may have different thermodynamic cycle modes such as the Brayton cycle, Carnot cycle, Stirling cycle, Ericsson cycle, and so on. Not only the irreversibilities of the heat leak and finite-rate heat transfer but also the different cycle modes of the heat engine are considered in the model. On the basis of Newton’s law, expressions for the overall efficiency and power output of the combined energy system with an irreversible Brayton cycle are derived. The maximum overall efficiency and power output and other relevant parameters are calculated. The general characteristic curves of the system are presented for some given parameters. Several interesting cases are discussed in detail. The results obtained here are very general and significant and can be used to discuss the optimal performance characteristics of a class of combined energy systems with different cycle modes. Moreover, it is significant to point out that not only the important conclusions obtained in Bejan’s first combustor model and Peterson’s general combustion driven model but also the optimal performance of a class of solar-driven heat engine systems can be directly derived from the present paper under some limit conditions.

Effects of combined heat transfer on the thermo-economic performance of irreversible solar-driven heat engines

A thermo-economic performance analysis and optimization has been carried out for an irrversible solar-driven heat engine with losses due to heat transfer across finite temperature differences, heat leak and internal irreversibilities. In the considered heat engine model, heat transfer from the hot reservoir is assumed to be simultaneous radiation and convection mode and the heat transfer to the cold reservoir is assumed to be convection mode. The effects of the technical and economical parameters on the thermo-economic performance have been investigated in order to see the collective effects of the radiation and convection modes of heat transfer. Also the optimal performance parameters of the heat engine, such as the thermal efficiency, temperatures of the working fluid and the ratio of heat transfer areas have been discussed in detail.

Ecological performance optimisation of a solar driven heat engine

An optimal performance analysis of a parabolic trough direct steam generation solar driven Rankine cycle power plant at maximum ecological objective function conditions is performed numerically to investigate the optimum design parameters and the optimal ecological performances. Comparisons for thermal efficiencies of the heat engines at maximum power and maximum power density conditions are provided. The effect of different heat transfer mechanisms between thermal reservoirs and working fluid is also investigated and the results are discussed in detail. The main finding of the present paper is that the thermal efficiency of the solar driven power plant at maximum ecological function conditions considered in the present study is always higher than those of the heat engines at maximum power and maximum power density conditions for all values of the allocation parameters concerned and the realistic range of thermal reservoir temperature ratio.

Optimum performance characteristics of an irreversible solar-driven Brayton heat engine at the maximum overall efficiency

An irreversible cycle model of a solar-driven Brayton heat engine is established, in which the heat losses of the solar collector and the external and internal irreversibilities of the heat engine are taken into account, and used to investigate the optimal performance of the cycle system. The maximum overall efficiency of the system is determined. The operating temperature of the solar collector and the temperature ratio in the isobaric process are optimized. The influence of the heat losses of the solar collector and the external and internal irreversibilities of the heat engine on the cyclic performance is discussed in detail. Some important curves which can reveal the optimum performance characteristics of the system are given. The results obtained here are general, and consequently, may be directly used to discuss the optimal performance of other solar-driven heat engines.

06/00289 Performance optimization of a solar driven heat engine with finite-rate heat transfer: Sogut, O. S. and Durmayaz, A. Renewable Energy, 2005, 30, (9), 1329–1344

06/00289 Performance optimization of a solar driven heat engine with finite-rate heat transfer: Sogut, O. S. and Durmayaz, A. Renewable Energy, 2005, 30, (9), 1329–1344

Optimum operating conditions of irreversible solar driven heat engines

An optimal performance analysis of an internally and externally irreversible solar driven heat engine has been carried out. A Carnot-type heat engine model for radiative and convective boundary conditions was used to consider the effects of the finite-rate heat transfer and internal irreversibilities. The power and power density functions have been derived and maximization of these functions has been carried out for various design parameters. The optimum design parameters have been derived and the obtained results for maximum power (MP) and maximum power density (MPD) conditions have been compared. The effects of the technical parameters on the performance have been investigated.

Thermoeconomic analysis of a solar driven heat engine

Thermoeconomic optimization has been carried out for an endoreversible solar driven heat engine using finite-time/finite-size thermodynamic theory. In the considered heat engine model, heat transfer from the hot reservoir is assumed to be radiation mode and the heat transfer to the cold reservoir is assumed to be convection mode. The power output per unit total cost is taken as objective function and the optimum performance and design parameters have been investigated. The effects of the technical and economical parameters on the thermoeconomic performances have been also discussed.

05/01197 Performance characteristics of an irreversible solar-driven Braysson heat engine at maximum efficiency

05/01197 Performance characteristics of an irreversible solar-driven Braysson heat engine at maximum efficiency