11.2% of power Generation capacity in 2020 will be intermittent wind and solar power. These power sources are known to have a low capacity factor and an even lower capacity credit. This means that wind and solar are not yet effective at replacing base load fossil fuel or nuclear capacity on a one for one basis in terms of megawatts. For renewable sources such as wind and solar to start to form a sizable percentage of our base load plants, the installed capacity has to outnumber the fossil fuel plants they are replacing. A the same time, fossil fuel, or other high-capacity-factor power plants must be maintained, or built to act as back-up sources of energy to mitigate capacity problems.
In the 2011 IEA report on the cost of generating electricity by different technologies, a base load factor of 84% was used for gas, coal and nuclear plants. Country-specific load factors were applied for renewables because they are largely site-specific but the medians were 24% for wind and 14% for solar. Capacity credits are complex to calculate and are wholly country-specific and can only be calculated by utilities with access to operational data.
However, as wind and solar increase in scale, the effect that individual plants intermittencies have on the grid are mitigated by other plants in the system. Denmark, for example, has one of the worlds largest penetrations of wind energy, and it is able to utilise much of it for base load power production because the farms are spread out geographically and inclement weather in one location does not necessarily mean that another power plant isn’t generating electricity. As such, Denmark has become one of the worlds largest wind-energy exporters.
A 100% reliance on renewable energy will be extremely difficult to achieve, but as more and more countries are developing their renewable energy portfolios to critical mass, the shares of fossil fuel power will continue to decline.