Clearly, an energy system based on wind and solar will occasionally experience weather-related supply gaps (caused, for example, by the change from day to night or a lull in wind resources). Critics call this the renewable energies’ »lack of capacity factor«.
But this is spurring us on to build a system which achieves 99.9999% availability – on an upward trajectory! Our studies show that around 20% of the annual energy turnover will have to come from a stored source at times when there is a lull in the real-time supply of inputs from renewable sources.
This balancing power supply will need sufficient capacity to meet all the consumer demand in rare but nonetheless real cases. The financing of this infrastructure is, in effect, the insurance that must be in place to achieve a 100% reliance on renewables, and is factored into our cost calculations. We are currently researching how this balancing power supply should be distributed across the country. Should there be a small number of centralised power plants, or a large number of smaller facilities?