에머지 개념을 이용한 풍력발전시설의 편익·비용 평가

Abstract

Global environmental changes caused by greenhouse gases such as carbon dioxide is now threatening the future of human civilization. With dwindling fossil fuel resources, the world community has been seeking new and renewable energy sources to meet the energy demand and address unstable fossil fuel supply. Wind power is one of the most promising alternative clean energies to replace fossil fuels in producing electricity. Many countries have been expanding the share of wind power-generated electricity in their electricity portfolios. The emergy methodology was applied to the evaluation of the Gangwon wind farm located in Pyeongchang, Korea, to assess its feasibility and sustainability in the emergy perspective. The wind farm has a capacity of producing 98MW of electricity with 49 2MW-class wind turbines, with a subsidy from the Korean government in the form of feed-in tariffs. Only direct emergy benefits and costs of the wind farm were considered in this study because there were not enough information on its indirect benefits and costs. Emergy benefits included electricity production and sales of certified emission reduction (CER) credits, and investments for construction, operation and maintenance of the wind farm were included as emergy costs. Total emergy input required to produce 8.01⨯1014 J/yr of electricity in 2008 was 4.58⨯1019 sej/yr, and the solar transformity of electricity was calculated as 5.71⨯104 sej/yr. Emergy yield ratio of the electricity production was calculated as 2.15, indicating that the wind farm contributed to the Korean economy more than twice the emergy investments for the facility. The Gangwon wind farm system caused little stress to the surrounding environment with the environmental loading ratio of 0.87. The wind farm system was evaluated as a moderately sustainable system with the emergy sustainability index of 2.47. Direct emergy benefits were calculated as 2.04⨯1010 Em￦/yr and direct emergy costs as 8.33⨯109 Em￦/yr. The net emergy benefit of the wind farm was 1.56⨯1010 Em￦/yr, and the emergy benefit/cost ratio was 2.88. This indicates that the wind farm was a feasible project in the emergy perspective with the emergy benefits greater than the costs. Even though the sales of CER credits that will end in 2016 was excluded in the emergy benefit-cost evaluation, the wind farm still provided a net emergy benefit of 8.33⨯109 Em￦/yr with the emergy benefit/cost ratio of 2.15. When the income from the direct sales of the electricity was only considered in the evaluation, the emergy benefit/cost ratio of the wind farm system dropped to 0.72, which means that the real wealth contribution of the electricity was not fully reflected in the market price. In this sense, the government subsidy seems to be an appropriate policy to recognize the true contribution of the wind farm to society. The emergy evaluation of the Gangwon wind farm showed that wind power could be a feasible and sustainable energy alternative for the Korean economy in the emergy perspective.