On Friday and Saturday, Germany set a new record for on-grid solar electric generation by a country. For a few hours on Saturday, solar panels were providing 50 percent of the electricity on the grid. The same electricity was generated on Friday, but it was only about 32 percent of that day’s electricity. Friday was a business day and more industrial and commercial facilities were operating, so the demand for electricity was higher.
It is not always sunny, so Germany averages just over 20 percent of electricity from all renewable sources combined. On the other hand, building owners continue to add solar capacity on a daily basis, a trend that may not stop during our lifetimes, so if peak solar output is 50 percent one day this month, it could be 55 percent next month, 70 percent in two years, and 100 percent in five years.
On a summer day when solar is providing 100 percent of the electric supply, the fuel-burning power plants could be idled for five hours in the middle of the day. It will cut into their profits but will also make maintenance easier to do.
And there is no reason for solar capacity to stop at 100 percent. In 10 years or so, solar panels at the peak of a sunny day could provide 250 percent of the grid power demand. At first, the excess power can simply be sold on. Arizona’s solar capacity, for example, is not merely compared to the demand in Arizona, but also to the much larger demand of California.
The accounting conventions of electricity virtually guarantee an excess supply, eventually. As long as you pay to have electricity delivered, on top of the cost of generating it, locally generated power (that is, from your own rooftop) will always be less expensive.
Eventually, then, we will have to have a plan for excess electricity. When electric generation exceeds demand, it will be a time to use electricity faster so it doesn’t go to waste. What could you do during a brief period of free electricity? Recharge your car, of course, but it also might be the right moment to run the clothes dryer and air-condition the attic. By consuming electricity for every use we can think of during the period of peak generation, we can reduce the demand for electricity later in the day, perhaps by as much as half.
Energy planners have talked about the need to shift electric uses into the periods of low demand, but it may be more important to shift into the periods of maximum supply. This is especially a consideration for recharging electric commuter cars. The ideal time to recharge is perhaps not at night, when no solar power is available, but in the late morning, in the employee parking lot.