Optimization Of Cooling Heat And Power Cogeneration System

CCHP is a cogeneration system that can accomplish the production of cooling, heating and power at the same time by making use of both the electrical and "waste" heat discharged from gas turbine unit. In contrast to the conventional systems, it can use energy- resources more efficiently, creating opportunities for reduction both in purchased energy costs and in environmental impact.CCHP has developed quite well in the developed countries, such as in Japan and the United States. But because of the situation in our country, CCHP is still a new field in the country and its application is not as good as expected. So it's very important for us to pay much attention to the investigation into CCHP. Just under this background. A comprehensive building in Beijing is selected for carrying out the study of the CCHP's operational process in this paper. Much attention will also be placed on the CCHP system's optimal economical performance when the load varies.First the constitution of the CCHP system is discussed in this paper, which includes a gas turbine or gas engine, a heat recovery boiler, water heaters, and double-effect Liar absorption refrigerator driven by the waste heat of the exhausted from the gas turbine. Furthermore the running conditions of the CCHP are analyzed in detail in this paper and come to the conclusion that the performance of the CCHP is not good because the actual load is much lower than the designed figure (lower than 40 percent of the designed figure).Under varied conditions the operation parameters are described by the fitting functions that are obtained using MA1XAB. On this basis, mathematical model under varied conditions is established, which includes GT model, HRSG model, Liar chiller model and water heater model. Then a series of program is made by VB, which offers a platform for establishing the objective function and get its solution.The analysis of the optimal operational strategy under varied conditions is carried out in Chapter 5, which includes non-constraint optimization and constraint optimization. The optimization models are established based on the objective functions of energy efficiency and gross profit separately and the variants of the functions are electric load rate, the rate of the steam used in cooling and the inlet temperature of GT. So some useful conclusions can be attained by the calculation of the objective function using the MATLAB optimal toolbox. According to the optimization results, the energy efficiency of the CCHP is the highest when the cooling load is temperate and the inlet temperature of GT is low (below 10 degrees centigrade).When the electrical load rate is not less than 0.8, the operation of the system will attain a benefit. Meanwhile, when the electrical load rate reduces, the extreme points of the energetic efficiency and gross profit will raise up with the inlet temperature of GT rising. The efficiency of GT has the most important influence on the energy efficiency of the system. In various kinds of working conditions, fuel cost is between 70 percent and 80 percent of the total cost. So the benefit of CCHP is low mainly because of the high price of fuel.