Construction And Optimization Study Of Combined Cooling, Heating, And Power Systems With The Three-Stage Thermostatic Biogas System

Energy is the basic of human activity. With the rapid development of global economy, the demand of energy becomes more and more growing. Whereas, the mineral resources included coal and oil, are exhausted day by day. Environment deterioration and destruction of ecological balance that caused by the burning of fossil fuels are gravely day by day. To enhance the common sustainable development of energy,evrionment and human economy, development and utilization of renewable energy sources and cascade efficient utilization of traditional fossil energy became the hot spot of energy research.As a second generation of the world's important direction of development of energy technologies, combined cooling, heating, and power(CCHP) technology is a cascade of energy efficient use of technology by the world wide attention. CCHP is proposed based on the concept of energy cascade utilization, combined the cooling, heating (heating and hot water) and power generation as one of the multi-generation system that can effectively improve the energy efficiency and reduce carbon compounds and other harmful gases. CCHP have two kinds: one is based on conventional fossil-based energy,the other is based on renewable energy.Based on the characteristics of anaerobic fermentation under constant temperature, combined cooling, heating, and power systems with the three-stage thermostatic biogas system was proposed and investigated in this paper. Based on the first law of thermodynamics, second law of thermodynamics and thermal analysis of structural theory of economics, thermodynamics and thermal economic performance is investigated. Based on the determine the electrical load and minimum annual operating cost as the objective function, optimal operation of combined cooling, heating, and power systems with the three-stage thermostatic biogas system was investigated.The main research topics and results are as follows:1. Based on the"temperature counterparts, cascade use"principles of heat utilization and the characteristics that there are two peaks of biogas production with the temperature, physical model and mathematical model of combined cooling, heating, and power systems with the three-stage thermostatic biogas system have built. It consists of internal combustion engine generator sets, single-effect lithium bromide absorption heat pump, jacket water heat exchanger, exhaust-water heat exchanger, lubricating oil heat exchanger, water-water heat exchanger and three-stage thermostatic biogas system. Based on the first law of thermodynamics and second law of thermodynamics, thermodynamic model was constructed and thermodynamics performerce was analysised. Based on the first law of thermodynamics and results of energy analysis,we can find that the primary energy rate(PRE) is 77.36% in summer and 83.34% in winter, the rate of primary energy saving is 32.96% and 34.28% respectively. Compared to the conventional separate system, the primary energy rate increase 49.17%. Dynamic simulation analysis can find that the impact of power to heating ratio to PER is much than the impact of power generation efficiency. Based on the the second law of thermodynamics and results of exergy analysis,we can find that exergy efficiency is 28.9%. Based on the exergy loss coefficient analysis,we can find that exergy loss mainly occurred in the three-stage thermostatic biogas system and gas engine power generation subsystem. Heat and mass recovery can reduce the exergy loss of the three-stage thermostatic biogas system and improving technological processes can reduce the exergy loss of the internal combustion engine.2. Based on the energy analysis and exergy analysis of combined cooling, heating, and power systems with the three-stage thermostatic biogas system and structural theory of thermoeconomics which combines the thermodynamics and economics, exergy cost model and thermoeconomics cost model was constructed, thermoeconomics performance was analysised. Solving the equation of exergy cost model and thermoeconomics cost model can receive the exergy cost and thermoeconomics cost, which provide a reference of product pricing, system optimal and fault diagnosis. Through the unit cost exergy consumption and unit thermal-economic cost, we can find that the unit cost exergy consumption and unit thermal-economic cost have a consistent changes and increase by the same direction along the thermodynamic cycle.3.Based on the determine the electrical load and minimum annual operating cost as the objective function, considering the performance characteristics of system equipment and system operation strategies, optimal operation of combined cooling, heating, and power systems with the three-stage thermostatic biogas system is investigated. Depend on the optimization results,we can find that when the system part load is 93.6%, the system's annual operating costs is minimum, the system payback period is 2.6 years, net present value is 1.424 million yuan and the primary energy rate is 84.35%.The innovation of this project and the significance:1.Combined cooling, heating, and power systems with the three-stage thermostatic biogas system was proposed and investigated. 2. Based on the determine the electrical load, operating cost strategy of combined cooling, heating, and power(CCHP) systems with the three-stage thermostatic biogas system that annual operating costs of is minimum was revealed.Accompany with the increasing human demand for energy, the dwindling of mineral resources such as coal, oil, and the serious damage of the environmental degradation and destruction of ecological balance that caused by the burning of fossil fuels day by day, combined cooling, heating, and power that as a second generation of the world's important direction of development of energy technologies was paid extemsive attention by countries in the world. In view of this, combined cooling, heating, and power systems with the three-stage thermostatic biogas system was proposed and investigated in this paper. The cogeneration substitute the non-renewable fossil fuels such as coal, oil, to biogas. The cogeneration improve the energy efficiency effectively, reduced carbon compounds and other harmful gases and has a good energy saving capacity and great social economic benefit. Such has an important academically valuable of further study of CCHP systems, an important reference value of improveing the integration of CCHP which driven by renewable energy and an important significant for promoting sustainable development of energy, enviroment and social humanity.