How big would the batteries need to be, to ride through the biggest dunkelflautes that occur each year, in renewable-heavy grids? This 8-page report has gathered data for Spain, the UK and California. 30 GWH of storage per GW of renewables would help ride through wind-driven dunkelflautes. But shutting thermal generation still seems unfeasible. Thus, grids grow ever larger.
A dunkelflaute is a period of exceptionally low wind and solar generation, depriving a renewable-heavy power grid of wind and solar electricity.
Hence, how big would the batteries need to be in order to ride through the largest dunkelflautes of the year, in typical renewable-heavy grids, restoring combined wind and solar output back to their monthly average level.
The reason for quantifying the size of dunkelflautes this way, is that it gives a comparable number, in “hours”, “GWH:GW of batteries” or “GW:GW of batteries” which is representative of real world wind and solar distributions, and should remain relatively representative even as renewables gain share in the global electricity mix.
The UK would need 30 GWH:GW of batteries to ride through the largest wind dunkelflaute of 2024, as shown on pages 3-4.
California would need 16 GWH:GW of batteries to ride through summer dunkelflautes, but the heavy slant towards solar would require several thousand GWH:GW to ride through winter, per pages 5-6.
Spain would need 30 GWH:GW of batteries to ride through the largest dunkelflaute, restoring renewables output back to its monthly average level, but again, there are issues with riding through winter, per pages 7-8.
Ramping renewables to 50% of global electricity grids inflates costs by 50-100%, while based on the data in this report, ramping them to 100% of grids inflates costs by 150-300%, and even then, we worry about the resiliency of these systems.