Typical Capacity Factor of a Hydroelectric Power Plant

Capacity factor is the average output of the plant in a year expressed as the percentage of the plant capacity. Capacity factor is greatly influenced by the availability and quality of fuel, the reliability of plant equipments, especially the turbine and generating units, and transmission system, demand for electricity, and length of preventive maintenance schedules. 

Thermal plants, like coal, geothermal and combined cycle plants, are usually run as base load due to the continuous availability of fuel and some operational constraints, which make it more economical if run at full load all the time. Its capacity factor is usually high.

Capacity factor of hydroelectric plants, on the other hand, varies depending on the availability of its fuel, water. Some existing hydro plants that are run as base load due to continuous and abundant supply of water have a high capacity factor that is comparable to thermal plants. Itipu hydroelectric power plant, for example, has a capacity factor of 77% in 2008 and 74% in 2007.

For some plants, which are dam-type and not much have plenty of water supply could only have a capacity factor of around 40% and could go to less than 20% during extreme dry season like during El Nino. Pantabangan hydroelectric plant in the Philippines, for example, has a capacity factor of only around 30% in 2004 and 2005, and a lowest of 5.5% in 1984. Hydro plants with low capacity factor are usually run as peaking plant - operates only during peak demand to take advantage of the high price of electricity.

Of course, if the availability of water is low, you could still design a hydro plant with high capacity factor by reducing the rated capacity.

According to the US Energy Information Administration (EIA), on the other hand, the typical capacity factor of a hydroelectric power plant is 44%. With this number, it seems that it was based on a peaking hydro plant. A low capacity factor such as this is also common to run-off river hydro plants because of the intermittent availability of water supply.

Filed in: Hydro, Power Plant Technology and Construction
Local date: March, 2010

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