Comparison of life cycle performance of distributed energy system and conventional energy system for district heating and cooling in China

The distributed energy system has achieved significant attention in respect of its application for single-building cooling and heating. Researching on the life cycle environmental impact of distributed energy systems (DES) is of great significance to encourage and guide the development of DES in China. However, the environmental performance of distributed energy systems in a building cooling and heating has not yet been carefully analyzed. In this study, based on the standards of ISO14040-2006 and ISO14044-2006, a life-cycle assessment (LCA) of a DES was conducted to quantify its environmental impact and a conventional energy system (CES) was used as the benchmark. GaBi 8 software was used for the LCA. And the Centre of Environmental Science (CML) method and Eco-indicator 99 (EI 99) method were used for environmental impact assessment of midpoint and endpoint levels respectively. The results indicated that the DES showed a better life-cycle performance in the usage phase compared to the CES. The life-cycle performance of the DES was better than that of the CES both at the midpoint and endpoint levels in view of the whole lifespan. It is because the CES to DES indicator ratios for acidification potential, eutrophication potential, and global warming potential are 1.5, 1.5, and 1.6, respectively at the midpoint level. And about the two types of impact indicators of ecosystem quality and human health at the endpoint level, the CES and DES ratios of the other indicators are greater than 1 excepting the carcinogenicity and ozone depletion indicators. The human health threat for the DES was mainly caused by energy consumption during the usage phase. A sensitivity analysis showed that the climate change and inhalable inorganic matter varied by 1.3% and 6.1% as the electricity increased by 10%. When the natural gas increased by 10%, the climate change and inhalable inorganic matter increased by 6.3% and 3.4%, respectively. The human health threat and environmental damage caused by the DES could be significantly reduced by the optimization of natural gas and electricity consumption.