This study concerns with the thermodynamic and dynamic analysis of an alpha type Stirling engine with Scotch-yoke piston driving mechanism. The thermodynamic aspect of the analysis is treated with a ...polytrophic nodal approximation. The pressure of nodal volumes is calculated with modified Schmidt formula which takes into account the pressure differences between nodal volumes caused by flow friction. The flow friction is calculated with adapted Darcy formula. The variation of the gas temperature in nodal volumes are calculated via the first law of thermodynamics given for unsteady open systems. The dynamic behavior of the engine is modeled via the motion equations of pistons and crankshaft. For a 2 kW nominal shaft power and 1400 rpm nominal speed, dimensions and working conditions of the engine were investigated by using realistic inputs. It was estimated that an engine having about 1.44 L swept volume, 1000 K hot source temperature, 400 K cold source temperature, 9050 cm2 total inner heat transfer area, 6 bar charge pressure, 2000 W/m2K inner heat transfer coefficient may produce more than 2 kW shaft power. For 142 rad/s average crankshaft speed the optimum thermal efficiency and torque of the engine were determined as 31% and 15.63 Nm respectively.
•Dynamic and thermodynamic analysis of a Scotch yoke Stirling engine.•Nodal analysis.•Mathematical model including flow and mechanical frictions.•Performance examination at constant speed and charge pressure.•Speed fluctuation characteristics.
Summary
According to new findings, the use of clean energy sources such as solar energy to supply energy (both electricity and heat) to human societies is essential. On the other hand, choosing the ...appropriate technology to convert solar energy into useful energy in the form of individual or combined systems is a fundamental issue. Individual solar energy systems have inherently low performance. However, their use in hybrid energy systems with other energy generation devices is key solution and shows high performance. The present work provides the performance of a new combined energy system composed of the parabolic dish solar collector (PDC), Stirling engine (SE) and thermoelectric device (TD) under various parameters. Sun is the main source of energy in this system, where, sunlight is focused on the PDC focal point by the parabolic shaped mirrors. Thus, the useful thermal power is produced by PDC and then feeds to the SE. The operating fluid of the engine is heated by this heat and converted into mechanical energy. Then, the mechanical energy is converted into electricity by a generator connected to the SE and the excess heat is lost from the engine. The exhaust of the SE transferred to the TEG hot end and produces further electricity. In addition, the TEC module absorbs the cooled environment heat and produces cooling energy (by consuming electricity from the TEG). Therefore, the proposed combined process provides the electricity, heat and cooling. The paper is based on the following three scenarios: (1) the system performance is evaluated under constant climatic conditions, (2) climate data from five various cities in Europe and Asia are used for system operation and (3) this scenario presents the general comparison between the two different hybrid energy systems driven by PDC and linear Fresnel reflector (LFR). In addition, multi‐objective optimization is provided to obtain the optimal performance of the developed hybrid system. The optimization results showed that, the optimum total output electricity and overall efficiency were 26.21 kW and 39.17%, respectively. It was also found that, average daily useful power generated by PDC in Moscow on 14‐June is 373.97 W/m2, which is about 11.1%, 1.55%, 33.3% and 14.23% more than Tehran, Beijing, Geneva and Kiev, respectively. Furthermore, increasing the temperature of PDC absorber improves the performance of SE and TD and subsequently improves the overall operation. Also, in terms of the PDC numbers, the system in the cities of Tehran, Beijing and Moscow has a better justification compared to the other two cities (Geneva and Kiev).
Thepresent work provides the performance of a new combined energy system composedof the parabolic dish solar collector (PDC), Stirling engine (SE) andthermoelectric device (TD) under various parameters.
It has been proven that the future of energy demands for human society is related to clean energy sources such as solar energy. On the other hand, fuel cell technology converts the chemical energy of ...a fuel into electrical energy. Meanwhile, the polygeneration system based on (semi) renewable energy can be a viable alternative to conventional fuel-based systems. However, examining their performance for widespread implementation requires further and powerful studies. The aim of the present work is to evaluate the performance of the polygeneration energy system to produce electricity, heat, hydrogen and cool. The novel hybrid power system consists of the 10 kWel phosphoric acid fuel cell, linear Fresnel solar reflector (LFR), Organic Rankine Cycle (ORC) and Stirling engine (SE). In the novel energy conversion process proposed, the fuel cell generates electricity and heat, and its waste heat is used to generate additional electricity in the SE. The fuel and oxidant required by the fuel cell are supplied by an electrolyzer that is powered by an ORC system. A solar thermal collector provides the duty required by the evaporator of ORC system. The effect of key parameters such as current density, solar radiation and flow rate of hydrogen on the system energy and exergy performance is also investigated. To evaluate the performance of the LFR system the climatic conditions of Tehran (in Iran) and Beijing (in China) are considered. Results revealed that, the SE and ORC system separately generates 1.48 and 26.54 kW of electricity, respectively. Furthermore, the electrolyzer consumes 23.36 kW of electric power and 3.64 kW of cooling is produced by the chiller. In addition, the energy efficiency and total exergy destruction of the proposed system are 71.32 % and 57.94 kW, respectively.
In this study, with a comprehensive approach, energy, economic, and environmental evaluations of a combined cooling, heating and power (CCHP) generation system driven by Stirling engine with working ...gases of hydrogen and helium were performed. This system can be used for residential applications. The engine was analyzed using the non-ideal adiabatic model, and two beta type Stirling engines were suggested in the CCHP system. Also, the energy analysis of the absorption chiller was presented with utilizing the waste heat of the engine. Then, the impacts of important specifications of the Stirling engine including: temperature of heater, length of regenerator, engine rotational speed, and type of working gases on the COP of absorption chiller, CCHP efficiency, Trigeneration Primary Energy Saving (TPES), Operational Cost Reduction (CR), and Trigeneration CO2 Emission Reduction (TCO2ER) relative to conventional energy supply systems were studied. Finally, at the appropriate conditions, the values for parameters of electrical power: 15.24 kW, 22.52 kW, heating capacity: 19.65 kW, 21.65 kW, cooling capacity: 12.65 kW, 14.43 kW, COP: 0.644, 0.667, CCHP efficiency: 70%, 72.29%, TPES: 24.05%, 31.3%, TCO2ER: 31.06%, 38% and CR: 75.53%, 78.8% were obtained for helium and hydrogen, respectively.
•Helium and hydrogen were used in a CCHP system with Stirling engine.•For engine analysis, the non-ideal adiabatic model with proper accuracy was used.•Frictional and thermal losses at different crank angles of engine rotation were analyzed.•The optimal conditions based on hydrogen and helium were evaluated from different viewpoints.
•A novel hybrid energy harvesting components are evaluated.•Beam splitter is used to divide wavelength spectrums.•STEG is used in the cavity for protecting the Stirling engine.•Feasibility of combine ...CPV/Stirling/STEG system is studied.•Cost performance of the hybrid system is investigated.
Concentrated photovoltaic (CPV) modules experience a reduction in the conversion efficiency with increasing in the cell temperature as a result of long wavelength solar irradiation which is not absorbed by the cell’s band gap. Separation of long wavelength solar spectrum from the solar irradiation helps to fully utilize the solar irradiation as a part of the otherwise wasted long wavelength thermal energy can be converted into useful electricity by the other types of energy harvesting mechanisms. In order to enhance overall energy harvesting from the solar irradiation, a novel hybrid energy harvesting system based on separation of the solar irradiation and comprising a solar concentrator, CPV, beam splitter, cavity, Stirling engine and solar thermoelectric generators (STEGs) is considered in this study. The STEGs are, furthermore, used in the cavity to protect the Stirling engine from overheating. Coupled governing equations are created and developed to predict and investigate daily performance of the hybrid system including the conversion efficiency and electrical power. Engineering Equation Solver (EES) software is used to solve the governing equations and to evaluate of the model. Moreover, cost performance of the hybrid system and its energy harvester components is estimated. Aalborg, Denmark, was selected as the location for investigation of the model. The results of the analytical model are in a good agreement with experimental results and previous studies for the considered energy harvesting mechanisms. The results show an overall system conversion efficiency of 21.8% and a total electric power output of 45.4 kW at 455 suns during the peak solar irradiance hours. In this period, the STEG is able to produce 1.2 kW electrical power. The CPV and STEG have higher cost performance amongst the studied energy harvesters in the hybrid power generator system. The results, moreover, indicate that the considered hybrid system has high potential to play a significant role among future renewable technologies as a high-efficient hybrid energy harvester.
•Thermo-economic multi-objective optimization of solar dish-Stirling engine is studied.•Application of the evolutionary algorithm is investigated.•Error analysis is done to find out the error through ...investigation.
In the recent years, remarkable attention is drawn to Stirling engine due to noticeable advantages, for instance a lot of resources such as biomass, fossil fuels and solar energy can be applied as heat source. Great number of studies are conducted on Stirling engine and finite time thermo-economic is one of them. In the present study, the dimensionless thermo-economic objective function, thermal efficiency and dimensionless power output are optimized for a dish-Stirling system using finite time thermo-economic analysis and NSGA-II algorithm. Optimized answers are chosen from the results using three decision-making methods. Error analysis is done to find out the error through investigation.
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•An installation combining renewable sources and cogeneration is studied.•Tests under real conditions for the three energy sources were conducted.•The electrical and thermal energy ...demand of a household can be evaluated.•Operation without radiation is possible thanks to energy storage and cogeneration.•A reduction of up to 36.2% in CO2 emissions has been obtained in the system.
This paper presents a novel installation where a set of photovoltaic modules and solar thermal collectors work in conjunction with a micro-CHP Stirling Engine to provide a reliable and self-sufficient energy system. A literature review showed that, while there are implementations of micro-CHP systems in household environments, there are no installations where the micro-CHP unit worked in conjunction with solar systems, photovoltaic and thermal. With the usage of Li-ion battery storage and a hot water tank for heat storage, as well as the micro-CHP unit, the system increases its reliability and independence from climatic conditions. The results obtained show that this system can supply 75.6% of the total energetic demand of a typical household, while achieving a reduction of 36.2% in the CO2 emitted to produce all the consumed energy in the system. The complete thermal demand has been met, while the usage from the electric grid has been required to meet 33.5% of the electric demand. However, with an increase in battery capacity to 20 kWh (doubling the actual capacity), the system is expected to become fully autonomous, as 31.8% of the electricity generated in the modules was exported to the grid due to saturation in storage capacity. In the thermal energy balance, sufficient heat was generated to provide enough energy for space heating or cooling, as well as domestic hot water.
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