風力發電效能評估參數之探討

Abstract

一般而言，火力、水力與核能發電廠若有完善的管理與充足燃料的補給，其負載因子可用來評估發電效能與穩定度。但在風力發電的風速是推動發電機的主要動能燃料，但因風並不能被儲存，風能與風速又是呈三次方正比關係，且隨時空的變動大，因此些微的風速變化都將會影響到發電效能。所以在評估風機效能時，若只探討負載因子是無法充分提供風機效能的資訊。為此，Chang等(2003)提出以三種風機效能參數，即負載因子、效率因子與可操作因子，探討環境風場中風機效能的表現。 本研究即接續上述的研究，評估負載因子與效率因子，並把可操作因子改良為非全速運轉與全速運轉操作因子，探討環境風場與風力發電機之間的關連性。研究中使用八台不同規格型號的風機與臺灣四處強風地帶，即梧棲、東吉島、蘭嶼與恆春，並依風機特性的不同，分組探討此三參數與風場及風機特性之關係。本研究發現，風機性能曲線中切入至率定風速之間的斜率變化，是決定負載因子大小的重要因素。負載因子可以清楚地辨識風場的強弱，但是對於在同一風場中架設機型不同的風機，其所產生的發電效率，並無法敏銳的表現出來。另外，效率因子可以辨識不同風機的效率大小，但對於風場強弱的區別能力不佳。最後，研究中將可操作因子分成為非全速運轉與全速運轉操作因子，可以更清楚風機在風場中非全速運轉與全速運轉的分布情形。

The efficiency of thermal, hydraulic, and nuclear power plants can be evaluated by using capacity factor, due to the fact that fuels are continually supplied and properly managed. On the other hand, wind velocity is the fuel of wind turbine. It is never steady and has the cubic relationship with wind energy. Small perturbation in wind speed can result in substantial difference in wind energy. It is thus not adequate to only use capacity factor in the evaluation of wind power plants. Chang et al. (2003) suggests that three wind turbine parameters (capacity factor, wind turbine efficiency and availability factor) have to be considered in analyzing wind energy production. Based on the result of Chang et al. (2003), the main objective of this study is to further investigate the above three wind turbine parameters and their relationship with wind turbine characteristics (such as cut-in velocity, rated velocity, and wind characteristics). Eight different wind turbines at four strong-wind meteorological stations (Wuchi, Tungchitao, Lanyu and Hengchun) in Taiwan are tested. The simulated results show that the slope of the power curve (from cut-in to rated velocity) greatly affects capacity factor of wind turbine. It is concluded that capacity factor can distinguish wind energy production in strong and weak wind periods. However, it cannot be used to determine the suitability of wind turbine installation due to its low recognition of wind turbine characteristics. In contrast, wind turbine efficiency can be applied to demonstrate the optimal wind turbine under different turbine characteristics. Finally, availability factor is classified into un-rated availability factor and rated availability factor, which can clearly express the detailed information of wind turbine operation.