ENERGY, EXERGY AND ECONOMIC ANALYSIS OF A MICRO-CCHP SYSTEM

Abstract

Combined cooling, heating and power generation (CCHP) systems can be utilized for commercial or multi-family residential buildings as efficient and reliable means to satisfy building power requirements and thermal loads. In the present study, a CCHP system consist of a Bryton cycle, an Organic Rankine cycle (ORC) and an absorption Ammonia-water cycle is considered. A detailed model is developed via MATLAB to assess the performance of the considered cycle from energy, exergy and economic perspectives. Appropriate ranges for inputs are considered and the first law efficiency, second law efficiency and ECOP of the cycle are determined as 77.17%, 33.18% and 0.31 respectively for the given inputs. Exergy destruction rates are found to be greatest primarily in the generator and the absorber of refrigeration cycle followed by the combustion chamber. The total exergy destruction rate in the system is found as 5311.51 kW. The exergoeconomic analysis is performed using SPECO approach to evaluate cost flow rate equations of the complete system and its individual components. Summation of capital investment cost rates and cost rates associated with the exergy destruction for the whole system is found as $18.245 per hour. Energy based cost of useful products is $2.14 per kW-h. A parametric study is also performed to provide an understanding on the effect of total pressure ratio and turbine inlet temperature of ORC on the performance of the system. A multi-objective optimization using Genetic Algorithm is performed to maximize plant energy efficiency and minimize the total cost flow rate of the whole system. A pareto front of all possible optimized operating points is obtained. A suitable operating point can be chosen making a trade-off between the two objective functions.