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.