Sustainability Assessment of Power Generation Systems by Applying Exergy Analysis and LCA Methods

Abstract

The selection of power generation systems is important when striving for a more sustainable society. However, the results of environmental, economic and social sustainability assessments are subject to new insights into the calculation methods and to changing needs, economic conditions and societal preferences. Researchers active in the field of exergy and sustainability claim that exergy losses and sustainability are related. The Total Cumulative Exergy Loss method and the exergy replacement costs of minerals are used to assess and compare power generation systems that make use of fossil and renewable energy carriers. These power generation systems are the following: an ultrasupercritical coal power plant, a power plant that co-fires coal and biomass, a wind farm, and a combined cycle power plant that uses bioethanol originating from the fermentation of verge grass. Furthermore, environmental, economic and social sustainability assessment methods are applied to assess the four power generation systems as well. On the basis of the results of the assessments, it is concluded that the wind farm system is preferred from the environmental, social and exergetic sustainability points of view, but not from the economic sustainability viewpoint. The advantage of the exergetic sustainability assessment method is that its results are not influenced by choices like whether verge grass should be considered a waste product or not. The influence of the exergy replacement costs on the results of the exergetic assessment is small, because less than 5 per cent of the exergy input of the systems during construction, operation and commission is of mineral origin. When looking at the infrastructural part of the systems only, the influence of the exergy replacement costs is larger because about 25 to 40 per cent of the exergy input is of mineral origin.