Sustainability and ecological efficiency of low-carbon power system: A concentrating solar power plant in China.

Low-carbon power generation has been proposed as the key to address climate change. However, the sustainability and ecological efficiency of the generating plants have not been fully understood. This study applies emergy analysis and systems accounting to a pilot solar power tower plant in China for the first time to elaborate its sustainable and ecological performances. Emergy analysis covers virtually all aspects of sustainability and ecological efficiency by considering different forms of materials inputs, environmental support and human labor on the same unit of "solar joule". The input-output analysis based systems accounting is applied to trace the complete emergy embodied in the supply chain for all product materials of the given plant against the back ground of complex economic network, which improved the accuracy of accounting. This analysis illustrated unexpectedly low sustainability and ecological efficiency of this particular plant compared with the emergy analysis based on the primary materials (steel, iron, cement, etc.). Purchased emergy responses more than 95% of the total and emergy input in the construction phase is more than twice as much as that in the operation phase. Comparisons with other kinds of clean energy technologies indicate previous studies may have overestimated the sustainability and ecological benefits of low-carbon power plants. Thus, it is necessary to establish this kind of unified accounting framework. In addition, sensitivity analysis suggests that strictly controlling monetary costs of purchased inputs, extending service lifetime and improving power generation efficiency can promote higher sustainability and ecological efficiency for solar power tower plants. This study provides a more comprehensive framework for quantitative emergy-based evaluation of the sustainability and ecological efficiency for low-carbon power systems.