Backup power is not a clearly defined term. In general, it indicates that certain power plants need to be maintained on standby in case other generators fail to produce power.
In the case of wind and solar, dispatchable backup power is required for when the sun does not shine and the wind does not blow. This can increasingly be covered by excess renewable power.
However, renewables are not the only power source that needs a backup. Conventional power plants occasionally malfunction themselves and have therefore always required some kind of backup capacity; countries that do not rely heavily on imports all have a part of their generating capacity on standby almost all the time. In addition, many countries, including Germany, have “reserve capacity” – power plants that only rarely run in case of emergencies.
The German Capacity Reserve
In 2015, Germany established what is called the “capacity reserve” or strategic reserve. The idea is that the reserve would switch on if the German grid ran out of power. The reserve is made up of Germany’s worst polluting lignite coal power plants, which were put on hold in the end of 2015.
In fact, “reserve” was a political, not a technical solution. The 2.7GW of power from lignite plants taken off the market receive special compensation for their “standby readiness.” But critics point out, however, that these plants are not “ready” at all. The plants are to be given ten days notice of the need to ramp up. Experts argue that there will never be a situation in which a grid bottleneck or power generation shortfall can be foreseen ten days ahead. In effect, this policy solely pays the polluters.
As of 2019, the capacity reserve has not been used. Nevertheless, plant owners received 1.6 billion euros to keep the plants idle. If the plants are never used, Germany will have avoided around 11-12.5 million tons of CO2 emissions. But ultimately, the costs of keeping these plants around is passed on to taxpayers, and the coal industry profits. This is largely due to the influence of the coal lobby.