Exergetic Optimization of Generated Electric Power Split in a Heat Pump Coupled Poly-Generation System

This study analyzes environmental, energy, and economical benefits of a ground source heat pump coupled poly-generation system by incorporating exergy into the energy efficiency analysis. Two additional terms, namely the rational exergy efficiency and the coefficient of performance were introduced to the primary energy savings equation in the European Union Directive 2004/8/EC. Based on the new equation, an optimization algorithm was developed, which can quantify the environmental, energy and economy benefits of any poly-generation system in a broader extent and scope. This algorithm was used to investigate the factors affecting the optimum split of the power generated by a poly-generation system between the heat pump and the customer. A base system was analyzed, which consists of a ground-source heat pump (GSHP) and a combined heat and power (CHP) system. Results show that any increase in the split in favor of the heat pump boosts the primary energy savings potential and thus CO₂ emissions reducing potential while the pay-back period of the system is reduced. When all the constraints, including electricity and fuel costs in the energy market are taken into account, a one-to-three split seems to be optimal for many practical applications. It is concluded that benefits of CHP may be enhanced by GSHP coupling pending a careful exergy balance analysis between the resource supply and the application demand. This paper provides the fundamentals of the algorithm and discusses that a win-win-win situation among the environment, energy, and economy is feasible, most importantly, from the global warming perspective.