Exergy based performance analysis of high efficiency poly-generation systems for sustainable building applications

In this study, first and second laws of thermodynamics, accompanying with Rational Exergy Management Method (REMM) were employed in developing a MATLAB based algorithm for natural gas fired, internal combustion engine (ICE) driven poly-generation systems. Two systems were studied based on a tri-generation plant built within the framework of the EU-FP6 HEGEL Project, tested at METU MATPUM (RICBED) building. This study introduces a better set of metrics for rating, evaluating, and optimizing poly-generation systems in order to minimize emissions, maximize fuel savings, and thus to accomplish an optimum sustainability metric among the factors of environment, energy, human needs and economics. Results show that with ICE poly-generation systems, exergy efficiency may increase beyond 60%. Even at part loads, minimum values of Primary energy savings (PES) are 12.4% for Case-1 and 17.7% for Case-2 (compared to minimum allowed 10%). REMM efficiency and Exergy Embedded PES (PESR) evaluated by REMM are proven to be better indicators of the performance. When exergy destruction is lower, (waste heat is recovered) PESR increases significantly. PESR values are minimum 18.2% for Case-1 and 42.4% for Case-2, which reveals that both systems provide high performance energy generation and considerably lower emissions.

► Poly-generation in high-performance buildings is economical, efficient and has low emissions.
► For such systems, optimization should be done from economic and environmental point of view.
► Energy and exergy rating methods (including REMM) and performance analysis is very effective.
► ICE poly-generation systems studied provide high primary energy savings and low emissions.
► This study can be used as a guide for analyzing performance of different poly-generation systems.