The difficulties making both wind and solar power practical sources of electrical power on the grid.
According to the U.S. Department of Energy, when intermittent sources such as solar or wind reach about 20 percent of a region’s total energy production, balancing supply and demand becomes extremely challenging: rolling blackouts can sometimes become inevitable. The same problem exists elsewhere, notably in Germany, where a vast photovoltaic capacity has sprung up thanks to generous subsidies.
The article proposes several reasonable solutions for storing power for use when there are lulls in wind or sunlight. All, however, appear costly, and all appear to end up making fossil fuels themselves more cost effective. For example,
A pumped-hydro facility consists of two reservoirs with a substantial drop in height between them. When there is excess electricity to go around, electric pumps move water from the lower reservoir into the upper one, thereby storing energy in the form of gravitational potential energy. When wind and solar wane or simply cannot keep up with demand, operators let water flow down and through turbines, generating electricity. In compressed-air facilities, excess electricity pumps air into underground caverns, and it is later released at high pressure to turn turbines.
Pumped hydro has been used for decades to balance the load on large U.S. grids. About 2.5 percent of the electricity used by U.S. consumers has cycled through one of these plants. In Europe the amount is 4 percent and in Japan 10 percent.
Reading this, I immediately asked, why not use this technology now to help reduce the amount of fossil fuels you need to burn? Japan seems to have figured this out. Why not us?