共查询到20条相似文献,搜索用时 15 毫秒
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《Heat Recovery Systems and CHP》1995,15(7):675-689
The research and development of LMMHD energy conversion (EC) systems which started in the 1960s has already come a long way and is heading towards commercialization. Design and development of such systems has to deal with a number of questions relating to single- and two-phase flows of molten metals, including different patterns of two-phase flow, interphase, phenomena, heat transfer, performance of LMMHD components and compatibility of liquid metals with other fluids and with confinement materials. Liquid metal MHD (LMMHD) power conversion systems proposed many years ago are gaining increasing attention in their various proposed modes, consisting of single-phase or two-phase fluid flow for a wide range of heat sources, e.g. solar energy, waste heat, nuclear energy, etc.Liquid metal MHD (LMMHD) power systems have been recently proposed for direct electrical energy conversion of low grade thermal sources of energy, like solar energy. Solar-powered LMMHD power generation systems are very attractive regarding efficiency and cost per unit of installed power. Theoretical and experimental investigations carried out in the various aspects of these systems are presented. A state of the art review of activities in the solar-powered LMMHD power systems field which have taken place so far is described here. 相似文献
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《Heat Recovery Systems and CHP》1992,12(6):451-456
In Mexico there are many potential geothermal energy sources with a wide range of temperatures. At present high temperature geothermal energy is used to generate electricity. Considerable experience has been accumulated in the exploitation of geothermal energy. Lower grade geothermal heat could be used to generate electricity with organic Rankine cycle plants. There is little industrial exploitation of lower temperature geothermal resources at present even though in the centre of Mexico areas of geothermal activity coincide with industrial zones. However, this situation could change with the use of suitable heat exchangers and heat pumps, particularly absorption systems to supply process heat with very little pollution. 相似文献
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This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO2-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON®Professional. A topping sCO2 cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO2 and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO2 cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s. 相似文献
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Organic Rankine Cycle (ORC) is an effective way to recycle waste heat sources of a marine diesel engine. The aim of the present paper is to analyze and optimize the thermoeconomic performance of a Series Heat Exchangers ORC (SHEORC) for recovering energy from jacket water, scavenge air, and exhaust gas. The three sources are combined into three groups of jacket water (JW)→exhaust gas (EG), scavenge air (SA)→exhaust gas, and jacket water→scavenge air→exhaust gas. The influence of fluid mass flow rate, evaporation pressure, and heat source recovery proportion on the thermal performance and economic performance of SHEORC was studied. A single-objective optimization with power output as the objective and multi-objective optimization with exergy efficiency and levelized cost of energy (LCOE) as the objectives are carried out. The analysis results show that in jacket water→exhaust gas and jacket water→scavenge air→exhaust gas source combination, there is an optimal heat recovery proportion through which the SHEORC could obtain the best performance. The optimization results showed that R245ca has the best performance in thermoeconomic performance in all three source combinations. With scavenge air→exhaust, the power output, exergy efficiency, and LCOE are 354.19 kW, 59.02%, and 0.1150 $/kWh, respectively. Integrating the jacket water into the SA→EG group would not increase the power output, but would decrease the LCOE. 相似文献
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《Heat Recovery Systems and CHP》1992,12(2):143-158
Power generation with low temperature geothermal resources is not economically viable due to the poor thermal efficiency of organic Rankine cycles (ORC). A novel idea is proposed where a vapour absorption chiller (VAC) can be employed to lower the ORC condensing temperature, thus increasing its power output. This paper presents detailed analysis of a VAC that operates with water-lithium bromide to extract heat from the geothermal brine leaving the ORC vaporizer. The evaporator of the VAC serves as the ORC condenser. A computer program is coded to simulate the combined ORC-VAC performance and compare it with that of the conventional ORC. The results indicate that the ORC-VAC option would render power generation more economical. The organic fluid flow rate in the ORC per unit power output is cut by at least 50% in this case, thus reducing the ORC size and turbine cost. Moreover, even though the ORC-VAC includes more components, the total heat exchange area requirement per unit power output remains practically unchanged. 相似文献
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To recover energy from the waste heat of aluminum reduction cells, a waste heat power generation system (WHPGS) with low boiling point working fluid based on Organic Rankine Cycle was proposed. A simplified model for the heat transfer around the walls of aluminum reduction cells and thermodynamic cycle was established. By using the model developed and coded in Matlab, thermal performance analysis of the system was conducted. Results show that the electrolyte temperature and the freeze ledge thickness in the cell can significantly affect the heat absorption of the working fluid in the heat exchange system on the walls. Besides, both the output power and the thermal efficiency of the power generation system increase with the system pressure. The output power and thermal efficiency of the system can also be affected by the type of working fluid used in the system. Working fluids for the best system performance under different output pressures were determined, based on the performance analysis. This WHPGS would be a good solution of energy-saving in aluminum electrolysis enterprises. 相似文献
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《Heat Recovery Systems and CHP》1989,9(5):451-455
This paper treats the solution to the problem of the connection of heat exchanger and heat pumps in geothermal district heating systems. A numerical solution for the theoretical Rankine heat pump cycle is presented to determine the thermodynamic process efficiency as a criterion of quality of energy flow in the process of its transformation. This allows a reduction in the losses caused by irreversibility of real processes and saves energy. The results in graphical form are used in practice for technical and economic optimization of various geothermal heating systems employing heat pumps. 相似文献
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《Heat Recovery Systems and CHP》1995,15(1):13-17
An endoreversible Carnot cycle is presented in this paper for a heat engine using higt-temperature waste heat. The endoreversible Carnot cycle is a modified Carnot cycle, where the heat-transferred between the heat engine and its surroundings is the only irreversible process. Since the energy input (waste heat) to the heat engine is free, the cost of the output power of the heat engine depends mainly on the size of the heat exchangers. A specific power, power per unit area of heat exchanger surface area, is adopted as the objective function for the performance analysis of the heat engine. The relation between the maximum obtainable specific power and the temperature range in which the high-temperature waste heat engine operates is found. 相似文献
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《Heat Recovery Systems and CHP》1990,10(2):79-86
Mexico possesses large amounts of geothermal energy. Samples from over 800 geothermal surface phenomena indicate that only 1.1% have an estimated reservoir temperature greater than 200°C. Current practice in Mexico is to produce power from such reservoirs using an open flash steam cycle. It is estimated that 4.8% of geothermal resources are in the temperature rangefrom 140 to 200°C which is a suitable range in which to operate Organic Rankine cycle power plants. Organic Rankine cycle power plants have been built in a range of sizes from 10kWe to 45 MWe. They have considerable potential for increasing the production of electricity from Mexico's geothermal resources. Organic Rankine cycle plants are discussed together with the conditions for their economic operation. 相似文献
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《Heat Recovery Systems and CHP》1991,11(5):335-339
This paper presents a discussion on energy and development with reference to India and brings into focus the importance of small power units (30–300 kW) fuelled by agroresidues and industrial waste heat. It examines the present status of these units and points out that the steam based systems excel over others in such features as conversion efficiency, robust operation and maintenance. The design and performance characteristics of steam based units developed at the Australian National University are outlined; the technology has been operational for about 10 years using steam generated by solar collectors. The nett present cost (NPC) calculations show that the commercial unit is likely to be significantly less expensive for periods over 6 years. 相似文献
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Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are free of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the compact formula for the efficiency is obtained. And the heat, work and efficiency are worked out. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work, and such black hole heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole. 相似文献
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LNG接收站利用低品位热源低温发电 总被引:1,自引:0,他引:1
LNG接收站需要大量的热能来加热气化LNG,降低燃气消耗可以减少操作费用。LNG接收站也要消耗大量的电能(2.83×107m3/天的气化量需要20~30MW)。利用LNG冷能低温发电能够显著减少操作成本,降低污染排放。采用中间流体Rankine循环的LNG低温发电流程,既可以生产电能,又可以输出指定温度下的产品天然气。该方案可以利用任何形式的低品位热源来气化LNG。模拟结果显示,气化容量为3.68×107m3/天的LNG接收站的低温发电系统,发电量为18MW,能带来每年0.7~1亿元的收益。 相似文献
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《Heat Recovery Systems and CHP》1988,8(2):125-139
Different versions of heat pipe ground heating and cooling devices are considered. Solar energy, biomass, ground stored energy, recovered heat of industrial enterprises and ambient cold air are used as energy and cold sources. Heat pipe utilization of air in winter makes it possible to design accumulators of cold and ensures deep freezing of ground in order to increase its mechanical strength when building roadways through the swamps and ponds in Siberia. Long-term underground heat storage systems are considered, in which the solar and biomass energy is accumulated and then transferred to heat dwellings and greenhouse, as well as to remove snow from roadways with the help of heat pipes and solar collectors. 相似文献
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In today's society there is a vast and in many cases not fully appreciated dependence on electrical power for everyday life. Furthermore, with growing energy and environmental concerns arising due to fossil fuel depletion and climate change/global warming, ever increasing attention is being given to alternative and/or renewable sources of energy such as biomass, hydropower, geothermal, wind and solar energy. Devices such as photovoltaic cells are therefore of enormous importance. The more widely used and commercially available silicon (semiconductor) based cells currently have the greatest reported efficiencies and have received considerable attention. However the manufacturing of these cells is complex and expensive due to the cost and difficulty of producing and processing pure silicon. One alternative technology being explored is the development of dye-sensitised solar cells (DSSCs) or Grätzel cells. In this paper we report on our current work to develop simple test equipment and optoelectronic models describing the performance and behaviours of DSSCs. We describe some of the background to our work and also some of our initial experimental results. Based on these results we aim to characterise the opto-electrical properties and bulk characteristics of simple dye-sensitised solar cells and then to proceed to test new cell compositions. 相似文献
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《Heat Recovery Systems and CHP》1994,14(1):67-77
This communication presents a thermodynamic analysis and assessment of a Freon fluid Rankine cycle cooling system. The system consists of two subsystems—Rankine engine (RE) power cycle and a vapour compression (V-C) refrigeration cycle. The heat engine subsystem consists of a boiler, turbine, condenser and a feed pump while the cooling subsystem consists of a mechanical compressor, condenser, evaporator and an expansion valve. A number of working fluid combinations for the RE cycle and V-C cycle subsystems have been chosen on the basis of their thermodynamic properties and their suitability judged in terms of the performance parameters, namely, the thermal efficiency of the power cycle and the coefficient of performance (COP) of the refrigeration cycle. A regenerative heat exchanger (RHE) is incorporated in the RE cycle to improve the cycle efficiency and achieve energy conservation.The effects of various operation parameters, namely, component temperatures, adiabatic expansion/compression efficiencies and effectiveness of the RHE on the overall COP have been assessed. It is found that R114 + R22 give the best overall system performance and the presence of the RHE improves the system COP significantly. The effect of V-C cycle condenser temperature is more pronounced as compared to that of the RE cycle condenser and similarly the effect of evaporator temperature in the V-C cycle is more pronounced as compared to that of the boiler in the Rankine cycle subsystem. 相似文献
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Solar energy conversion with fluorescent collectors 总被引:1,自引:0,他引:1
A new principle for solar energy conversion is proposed and evaluated theoretically. Collection and concentration of direct
and diffuse radiation is possible by the use of a stack of transparent sheets of material doped with fluorescent dyes. High
efficiency of light collection can be achieved by light guiding and special design of collectors. The optical path length
in a triangular collector is computed.
In combination with solar cells this type of collector offers the advantage of separating the various fractions of light and
converting them with solar cells with different bandgaps. Theoretical conversion efficiency under optimum conditions is 32%
for a system with four semiconductors.
Thermal energy conversion offers several advantages over conventional collectors: High temperature and efficiency even under
weak illumination, separation of heat transport and radiation collection, low thermal mass. Thermal efficiency is computed
to be between 42% and 60%. Very attractive appear hybrid systems for generation of thermal and electric energy. An estimate
of the economics of electricity generation shows that due to the concentration costs can be much lower than possible today.
With the use of only silicon cells the breakeven point of $0.5/W is almost reached.
Practical difficulties to be solved are: Synthesis of dyes with stringent requirements, identification of plastic materials
with high transparency and development of solar cells with higher bandgaps. 相似文献