Why renewables alone cannot meet our energy needs 

When Germany met all but 0.3 gigawatts (GWs) of its peak energy demand for a few hours using renewables this May, the excitement generated a lot of headlines. The headlines missed key details, though – during that time, Germany’s fossil fuel plants were still producing 7.7 GWs. The excess had to be sold to neighboring countries on the cheap.

Since then, Germany has been forced to dial back its renewable subsidies and pay billions to maintain coal generators because, despite the ability to generate lots of power from renewables, meeting power demand when renewables weren’t generating quickly became a problem.

Coal, natural gas, nuclear, biomass, geothermal and hydroelectric power are all capable of providing energy 24/7, what energy experts refer to as “base load” energy. Of those, geothermal and hydroelectric are restrained to specific geographical areas, many of which have already been tapped. Biomass is inefficient and only environmentally friendly to a point. Only coal, natural gas, and nuclear provide constant and reliable energy to any significant portion of the United States. Notably missing from this list are solar and wind. As base-load energy sources are phased out in favor of intermittent renewables, grid reliability suffers.

It’s clear that solar and wind provide clean and renewable energy when the sun is shining or the wind is blowing. But when the sun is down or the air is still, they sit, not producing much of anything. In those moments, other sources must fill the gap. Without base-load producers, there simply is not enough energy to sufficiently supply the grid at all times of day, no matter how many solar or wind facilities get tacked on.

Traditional base-load providers (coal and nuclear) take a long time to turn on and off. Natural gas, while capable of being built to ramp up quickly, is often built in slower, combined-cycle systems to reduce costs. For this reason, even at peak production for solar and wind, base-load plants are kept running so they are ready to provide energy when the renewables no longer can.

The delicate balance between base load and intermittent generation can be seen in California, where closure of the Diablo Canyon nuclear facility threatens 9 percent of California’s energy production. While the stated plan is to replace that capacity with “energy efficiency, renewables and energy storage,” that may not be feasible. California is already reliant on huge amounts of solar, enough that they actually had to shut down some solar producers for fear of overloading the grid this March. Practicality indicates that it is more likely that the lost capacity will be made up with natural gas generators.

Despite the need for consistent base-load power, coal plants across the country continue to be shuttered due to the mounting regulatory burden they face. Seventy-two GWs of base load coal generation are set to go offline in coming years. (For context, 72 GWs is enough to power “every home in every state west of the Mississippi River, excluding Texas,” as the Institute for Energy Research notes.) The North American Electric Reliability Corporation (NERC) predicted in 2013 that “insufficient reserves during peak hours could lead to increased risk of entering emergency operating conditions, including the possibility of […] rotating outages.” To make matters worse, even more coal plants have announced shutdowns than NERC assumed when making that prediction.

Keeping a well-functioning grid that provides every American with power on demand requires substantial base-load power capacity. While intermittent renewables like wind and solar can make good supplements, they cannot provide for the energy needs of modern society alone.

Yonk is an assistant research professor at Utah State University. Wardle is a research associate at Strata, a public policy research center in Logan, Utah.