Electricity Storage as a Matching Tool Between Variable Renewable Energy and Load

Abstract

The transition to low carbon emitting solutions imposes new challenges to the power sector to accommodate a large penetration of intermittent renewables. It goes beyond the cheapest symmetrical reduction of fossil thermal generation that is being avoided. Storage is seen as the solution and also the option for batteries, but using a Discrete Fourier Transform and real hourly data it is shown that storage acts as an integral function, attenuating the “daily” and “weekly” harmonics of the charging / discharging function and leaving the “yearly” cycle as the main component to set the storage capacity needed. Export / import with neighbour systems shall be seen as a competitor with storage, but it poses mutual dependency and shared security issues. The renewable generation cost reduction in the “learning curve”, achieving a levelized cost below the variable cost of a CCGT is a milestone and it allows accepting a certain level of curtailment as an alternative to reduce the investment in storage. Batteries do not solve the long-term storage problem but today its use begins to be competitive in the “daily” cycle, replacing peaking gas plants and reinforcing the concept that the cost of storage can be seen as an equivalent thermal power plant. Better than assuming a fraction of renewable energy curtailment, it might be the development of Power-To-X solutions (hydrogen, synthetic gas, etc.) or even investing in nuclear power plants and limiting intermittent renewables penetration accordingly. Both solutions represent indirect electricity storage – fuel has a low storage cost - and it can solve the renewable surplus seasonal transfer problem, recovering synchronous generators for providing dispatchable flexibility, inertia to the system and serving as backup for periods with low renewable generation.