What is 'Capacity factor'? What is 'availability factor'?

 What is 'Capacity factor'?

Capacity factor is a way to measure the productivity of a wind turbine or any other power production facility. It compares the plant's actual production over a period of time with the amount of power the plant would have produced if it had run at the full capacity for the same amount of time.

Capacity Factor = Actual amount of power produced over time Power that would have been produced if turbine Operated at maximum output 100% of the time

A conventional utility power plant uses fuel, so it will normally run much of the time unless it is idled by equipment problems for maintenance. A capacity factor of 40% to 80% is typical for conventional plants (thermal, nuclear, large hydro etc.).

A wind turbine is 'fueled' by the wind, which blows steadily at times and not all the times. Most modern utility-scale wind turbines operate with a capacity factor of 25% to 40% although they may achieve higher capacity factor during windy season. It is possible to achieve much higher capacity factors by combining wind with a storage technology such as pumped hydro or compressed-air energy storage (CAES).

It is important to note that while capacity factor is almost entirely a matter of reliability for a fueled power plant, it is not for a wind plant. For a wind plant, it is a matter of economical turbine design. With a very large rotor and a very small generator, a wind turbine will run at full capacity whenever the wind blew and would have a 60-80% capacity factor, but it would produce very little electricity. The most electricity per rupee invested is gained by using a larger generator and accepting the fact that the capacity factor will be lower as a result. Wind turbines are fundamentally different from fueled power plants in this respect.

 What is 'availability factor'?

Availability is a measure of the reliability of a wind turbine or other plant. It refers to the percentage of time that a plant is ready to generate (that is, not out of service for maintenance or repairs). Modern turbines have an availability of more than 98%-higher than most other types of power plant. After two decades of constant engineering refinement, today's wind turbines are highly reliable.