The capacity factor of a wind turbine or solar panel installation indicates how efficiently an installation produces electricity over a certain period of time compared to its maximum theoretical capacity. It is a measure of the actual performance of the installation, expressed as a percentage.
Formula
Capacity Factor = (Actual electricity produced (kWh) / Maximum possible electricity (kWh)) * 100
Explanation
1. Actual electricity produced: This is the amount of electricity that an installation actually produces over a certain period (e.g. a year). This depends on variables such as wind strength or sunshine.
2. Maximum possible electricity: This is the amount of electricity that would be produced if the installation were to operate constantly at full capacity (e.g. at 100% wind or solar radiation).
Example
A wind turbine has a maximum capacity of 3 MW and could theoretically produce 26,280 MWh in a year (8,760 hours). However, due to variable wind conditions, it only produces 7,884 MWh.
Capacity Factor = (7,884 / 26,280) * 100 = 30%
This means that the turbine operates at an average of 30% of its maximum capacity.
Typical values
Onshore wind turbines: 20-40%
Offshore wind turbines: 40-60% (due to stronger and more constant winds)
Solar panels: 10-25% (depending on location and hours of sunshine)
Conclusion
The capacity factor is important for understanding how effective an installation is and for comparing installations. A low factor does not necessarily mean inefficiency, but may indicate natural limitations, such as less wind or sunshine.