基于生态能量视角的我国小水电可持续性分析

The sustainability analysis of small hydropower plants in China based on ecological energetic accounting

我国的小水电开发经历了以解决农村地区用电短缺到当前以促进节能减排、清洁能源建设为目的的转变。运用生态能量分析的方法之一——能值分析方法,选取贵州省安龙县红岩二级水电站为案例,对其建设与运行的可持续性进行了系统分析,并与国内外大水电的相关指标进行了平行对比。结果表明:该水电站2010年电力产出的能值转换率为1.03×105sej/J,其可再生性比例为52.01%,在能值产出率、环境负载率和可持续能力等方面的表现均好于大水电。但其能值交换率为0.58,表明2010年水电上网价格偏低。小水电的不稳定运行也使其系统能值指标呈现波动变化,当实际发电量为设计发电量的50%时,水电的能值转换率接近于湄公河上大坝生产水电的能值转换率,可持续性指标的值从6.12急剧降到3.01。系统评估水电资源,作好流域小水电总体开发规划,保证小水电系统稳定运行是提高其可持续性的关键之一。

With the rapid development of small hydropower in China, its sustainability has drawn more and more attention. Using emergy analysis, one of the ecological energetic accounting methods, the overall sustainability of small hydropower system was analyzed in this paper, when choosing Hongyan second-cascade hydropower plant, Anlong County, Guizhou Province, China as the case. With the ability of accounting all forms of energy and materials from both environment and economic society on a common energy basis, emergy analysis has been used to analyze various kinds of systems such as agro-systems, wetlands systems, and urban systems. It has been proved as a powerful tool of the sustainability assessment of ecological economic systems. The related indices and ratios based on emergy flows can characterize the resource use, environmental impacts and overall sustainability of the studied systems, such as emergy yield ratio （EYR）, environmental loading ratio （ELR）, and emergy sustainability index （ESI）. The results showed that the studied small hydropower production system produced 8.79x 1013j of electricity in 2010 by support of a total emergy of 9.04x 10TM sej, in which river geopotential energy was the largest input, accounting for 48.35% of the total input. As a whole, 77.29% of the total input was from environment, which indicates that the construction and operation of the studied production system depended heavily on the local free environmental resources. And the transformity of electricity in 2010 was 1.03 x 105 sej/J, with a fraction of 52.01% renewable resources. By contrast, the transformities of electricity produced by large hydraulic projects at domestic and abroad were larger than 1.50× 105 sej/J. Indicated by the comparison of EYR, ELR and ESI among the studiedsystem and the large hydraulic projects, the studied system possessed a higher competitiveness, a smaller environmental stress and a better sustainability. However, the value of emergy exchange ratio （EER） was 0.58, implying that the actual price of electricity integrated into the grid in 2010 was unfair for the studied plant. The process of integrating the electricity into the grid lost certain emergy for the plant. Additionally, a significant feature of small hydropower is unstable operation caused by lacking of dam or reservoir, which is different from large hydraulic projects. The operation of small hydropower plant is largely influenced by precipitation and other water diversion activities. Consequently, the generation of the electricity differs from year to year, which results in the fluctuation of related emergy indices. Moreover, it was found out that when the generation is 50% of the designed generation, the transformity of the studied production system is close to that of large dams on Mekong River and the value of ESI declines remarkably from 6.12 to 3.01. It is concluded that the sustainability of small hydropower production system is very sensitive to its generation. And the generation is determined by the amount of exploitable water resources. In order to improve the sustainability of small hydropower in China, it is important to make a good plan of exploiting hydropower resources and ensure stable operation.