An exergy-ecology assessment method and its application for basic building heating schemes

Abstract

ABSTRACT Building heating is the main type of heating consumption in China. At present, there is a lack of attention given to the assessment of ecological cost or impact considering energy depreciation for various heating schemes. In this work, a method of exergy-ecology assessment is proposed to evaluate the energy and ecological characteristics of four basic building heating schemes. The solar-equivalent joule was adopted as the unified quantitative value of ecological impact by converting exergy, material, and cost flows. The exergy-ecology balance was established for each scheme, and a series of indexes were proposed and calculated through two strategies. The results show that the objective exergy efficiency of Scheme 3 heat pump is the highest (53.87%) and that of Scheme 2 electric heater is the lowest (17.58%). Larger difference of energy grade between energy providing side (0.83 for gas fuel and 1 for electricity) and receiving side (0.18 for output water) connects with lower exergy efficiency. Scheme 3 heat pump has the highest eco-exergy efficiency under both assessment strategies (71.89% and 53.86%), followed by Schemes 4 solar collector (61.52% and 36.34%). This method proves that the thermodynamics perfectness of system is positively correlated with ecological sustainability and can be used to assess other energy systems.