This capacity, experts agreed, was needed urgently to cover for solar PV and onshore wind production during periods of uncooperative weather, to obviate reliance on coal-fired plants to back up renewables, and to stabilize the growing supply of renewable energy in Germany’s system. After all, solar PV and onshore wind are the backbone of the Energiewende in the power sector, and will be in the future as Germany drives forward to switch to a renewables-based power supply.

Different means of storage — pumped water, batteries, small-scale distributed, hydrogen, compressed air, Nord Link (a Norway-Germany cable) — are among the costly options that Germany is pursuing for electricity, heating, and transportation. Just recently, Germany’s minister for energy and economy, Sigmar Gabriel, proudly unveiled Europe’s to-date largest (and most expensive: $7.5 million) commercial battery plant, which is powered by 25,600 lithium-ion batteries and has a storage capacity of 5 MWh.

But this autumn, one of Germany’s leading energy think tanks, Agora Energiewende (financed by the Stiftung Mercator and the European Climate Foundation), dropped a small bombshell on the Energiewende community. In a study carried out by Agora and other high-profile, independent research institutes, it concluded that significant storage capacity for renewably generated electricity would not be needed for another 20 years — until Germany has at least a 60 percent share of renewables in its power sector. The study is a hot potato that has, so far, incurred considerable critique from peer institutes and lobby groups.

«The key insight here,» explains one of the authors, Daniel Fürstenwerth of Agora Energiewende, «is that the Energiewende can continue investing massively in renewable power right now. We will need to invest in power-to-power storage capacity in the long term, but not today. We have to keep the Energiewende cost-efficient or the German people, industry, and the political establishment won’t go for it.»

The essence of Agora’s argument is that Germany’s energy system can maintain the flexibility it needs even as renewables expand by other, less costly means than new power-based storage technology. These alternative options include demand-side management, flexible conventional power plants, and grid expansion both in Germany and across its borders.

Demand management is an idea central to the work of Agora Energiewende, a young think tank that burst onto the scene in Germany two years ago. «It’s about making the electricity demand flexible so that it meshes better with a fluctuating power supply,» explains its website, as well as «making the power system as a whole more flexible in order to ensure security of supply.» Agora’s analysts argue that energy demand management can be spurred by market incentives, regulatory guidelines and new technology that will reduce investment costs in the Energiewende and help ensure supply security.

Load control, load shifting, energy efficiency and conservation, for example, are all ways to manage demand. One Agora study shows that Germany’s industrial producers can shift more than a gigawatt of their power demand for short periods, a phenomenon that on a larger scale could go a long way to ensure security of the regional power supply. Pilot projects in Bavaria and Baden Wurttemberg have already brought encouraging results.

Moreover, inflexible conventional power plants like Combined Heat and Power (CHP) plants can be made more flexible by adding hot water towers. In Germany today there are already CHP plants in places like the German cities of Flensburg and Nuremburg that turn surplus power into hot water, opening the way for renewables to provide supply when the weather dictates. «It’s a relatively cheap solution,» says Fürstenwerth.

The other cornerstone of Agora’s argument is that Germany’s current grid and the expansions underway — an additional 2,650 kilometers of new high-voltage grid is currently being laid — will provide the flexibility necessary to accommodate more renewables. Agora assumes that grid construction will proceed as planned — in Germany as well as in neighbor countries — which will better enable grid operators to match supply and demand. And the better Germany is linked to its neighbors, the more it can balance by trading on the European market.

The Agora’s skepticism about power-to-power storage in the near future, notes Fürstenwerth, does not extend to storage technologies in other sectors, such as batteries in electric vehicles and power-to-chemicals in industry, which Agora believes are likely to develop strongly in the coming decades.

Industry Reacts

The study elicited a strong response, first by the heavy-hitting German Energy Agency (DENA), a well-respected partly government-funded body dealing with renewable energy and energy efficiency. Its executive director Stephan Kohler shot back at Agora: “Electricity storage facilities are essential for the Energiewende. Anyone who alleges otherwise is damaging the Energiewende and, in the end, is risking the supply security in Germany.”

DENA’s argument for rapidly expanding storage capacity by means of pumped-storage plants and other technologies is based on the same rationale that has dominated in Germany for years. Storage can compensate for short-term fluctuations in electricity generation by absorbing excess electricity from wind and solar power plants and feed it into the system later.

By 2025, says Kohler, photovoltaics and wind power plants will account for a total capacity of 130,000 MW in Germany. “When the sun shines and the wind blows,” he says, this full volume of power should be fed into the grid. Without additional storage facilities,” says Kohler, “we must sell the electricity produced from renewable sources, which is subsidized by German electricity consumers, to other European countries at minimal prices. We should not make the same mistake as we did with grid expansion. We waited too long there, and are now struggling to catch up.”

One problem is that pumped-storage potential is limited in Germany, and even where it is technically feasible, there are NIMBY protests against it. So other avenues must be aggressively explored, says DENA’s Kohler.

Not surprisingly, the Eurosolar, the European Association of Solar Energy, and the German Energy Storage Association (BVES) also criticized the Agora report. DENA too has a vested interest, financed in part by private sector actors involved in pumped-storage development.

A neutral observer, Wolf-Peter Schill of the German Institute for Economic Research (DIW Berlin), argues there’s a middle ground between the two positions. “Model-based evidence shows we’re not going to need a lot of storage capacity soon,” he says.

“But to err on the cautious side, a moderate expansion of storage capacity, like pumped storage, wouldn’t be too expensive and might be insurance for the Energiewende,” argues Schill. There are a number of aspects of the Agora scenario that might not pan out — like the benefit of European interconnection or the increased flexibility of conventional and renewable energy producers and the demand side — which would change the whole equation, he says.

This lively debate isn’t going to change German policy tomorrow. But it has already added complexity to the kind of discourse that must transpire in a society pushing into the unknown the way Germany is with the Energiewende.

Lead image: Impala horns via Shutterstock