Storage is the key

In addition to wind and solar-based power generation, energy storage is the third building block for a fossil-free energy supply. It ensures that wind and sun energy is available when it is needed.

However, that’s not all. Certain storage types such as batteries play another very important role: They stabilize the energy system. Combined with intelligent software they enable the flexible and demand-driven use of conventional generators and even make it possible to turn off nuclear, coal, gas or Diesel power plants completely.

We have been working intensively with energy storage since 2005 and are often faced with certain questions and misunderstandings:

  • In the wake of the transition to renewable energy in Germany, there is much talk about the need to put further research into energy storage. Of course, many years still need to be invested in energy storage research. But this should not stop us from using already available, commercially and technically viable storage technologies.
  • Moreover, the heated debate about the transition to renewables sometimes also obscures the requirements storage have to meet in order to raise the share of renewables above the approximately 30 percent limit currently determined by fossil energy systems.

First stop: Short-term storage

Principally, post-fossil energy supply needs all types of storage: hourly, daily and in the long run also seasonal storage; it needs larger units as much as smaller storage systems very close to the consumer.

However, during the initial phase of the transition to renewables, we need to be able to store comparatively large amounts of energy for small time periods such as minutes or hours. This ensures that – at a given point in time – we have just as much power as needed, thus keeping the grids in balance.

Only once we reach an annual share of approximately 60 percent of renewable energy, will we need significant daily storage capacities – in order to shift solar energy to the nights and storms into periods of calm winds. In order to increase the annual share of renewables above approximately 75 percent, we will ultimately also need seasonal storage systems that preserve energy for weeks and months.

Reliable storage already exists

A large variety of storage technology already exists and is used in many different applications. Batteries for phones and computers have already been developed, but stationary storage systems still have a very high cost-reduction and development potential. Still, some stationary storage systems are already proven to be durable, safe and commercially viable.

This includes pumped hydro power plants, but also electrochemical storage systems – i.e. batteries. Unfortunately, water is not abundant everywhere.
In many areas – including Germany – the potential for pumped hydro storage has been exhausted.

That’s why we identified three battery technologies that are particularly well-suited for the large-scale storage of renewable energy: Lithium-Ion, Sodium-Sulphur and Vanadium-Redoxflow.

When will storage be cheaper?

Even though batteries are already commercially viable today, they are still comparatively more expensive than wind and sun power generation units. However, they have a high cost-reduction potential. Here too, we come across a fundamental misunderstanding: more research or even just waiting will not lower the price of commercial storage. Only mass production triggered by widespread application will make batteries cheaper.

What’s more: Even though it’s still comparatively expensive, storage can
already partially compete with the marginal costs of fully depreciated fossil power plants.