Exergo-economic analyses of two building integrated energy systems using an exergy diagram

This paper tackles the exergo-economic assessment of two integrated energy systems that allow the building heating demand to be achieved; a solar assisted heat pump using ice storage and an ambient air heat pump with photovoltaic panels. These systems are firstly described and their performance is discussed for various surfaces of solar collectors and photovoltaic panels. To this purpose, the total electrical energy consumption and the total cost are estimated while the total exergy destruction is divided according to renewable and non-renewable energy flows. This latter, which is really paid by the user, then serves as the exergy performance indicator. The ambient air heat pump with photovoltaic panels is found as the optimal solution from energy and economic perspectives while the solar assisted heat pump using ice storage provides the best exergy performance. To help analyze results, the system performance is illustrated by using an exergy diagram, where energy terms are shown on the abscise axis and energy quality factors are on the ordinate axis. This 2-D graphical representation, which can consider the results from dynamic analyses, helps understand the system operation and performance, and reveals the sources (components), the reasons (energy loss and/or energy potential factor degradation) and the nature (renewable, non-renewable flows) of irreversibility.