Will there ever be enough storage to go 100% renewable?

Calm, cloudy weather could spell the end of hopes for a Europe running off 100% intermittent renewable energy. Pic: Animam.photography.

Calm, cloudy weather could spell the end of hopes for a Europe running off 100% intermittent renewable energy. Pic: Animam.photography.

By Jason Deign

Using storage to even out intermittent generation in Europe may be a pipe dream at high renewable energy penetration levels, according to one researcher.

Dr Björn Peters, a former power systems financier who will be speaking at the upcoming Energy Storage World Forum in Berlin, said it would be uneconomical to build the level of storage needed to overcome calm periods.

His studies of European weather patterns over the years show the continent is hit by doldrums, or spells of cloudy, calm weather, up to twice a year, on average.

These weather patterns can last for up to two weeks at a time and extend over many thousands of kilometres, he said.

“To balance out this you would need 2,000 times the entire pumped-hydro capacity in Germany,” he told Energy Storage Report. “We have 45GWh and we would need about 80TWh at least. 

Additional reserves for extreme weather

On top of that, he noted: “We would need additional reserves for really extreme weather events.”

Apart from the scale of energy storage needed to deal with doldrums, the fact they may last for days on end means it is practically impossible to deal with them with any technology other than pumped hydro.

“Practically all the storage plants today are being built with a storage time of up to four to eight hours,” Peters said.

“But wind systems build up over 18 hours, may last several days and can go back to zero within 18 hours, followed by doldrums of several days.”

And deployment of the kind of long-term storage needed to handle doldrums faces another challenge, he said. 

The impact of renewable energy

Even if Europe had the capacity and the money to build thousands of extra pumped hydro plants, right now it does not make financial sense in markets such as Germany… ironically because of the impact of renewable energy.

Most of Germany’s pumped hydro was built to store base-load thermal generation at night, when electricity demand is low, and deliver it back to the system when energy prices increase during the day.

Nowadays, however, daytime energy prices have dropped in Germany because of the amount of solar energy coming onto the grid. This has effectively wiped out the business case for pumped hydro.

Peters’ research echoes warnings voiced by other energy experts, such as renowned Energy Matters author Euan Mearns, who noted the impact of seasonal calms on European wind power output back in 2015.

It also helps explain the apparent failure of renewable energy and pumped hydro systems such as that installed in El Hierro, Canary Islands. 

Gorona del Viento on El Hierro

The Gorona del Viento plant on El Hierro was intended to supply 20% of annual electricity consumption through pumped hydro. The latest publicly available data seems to indicate the actual level is less than 4%.

Peters’ findings also appear to counter findings by German energy expert Gregor Czisch, whose research proved that it is possible to a achieve a fully renewable and at the same time affordable electricity supply for Europe and its neighbourhood if the output from production plants is allowed to be transported far enough.

However, Peters said there was no conflict in the two lines of research. Czisch “did a very proper analysis,” said Peters, “and he showed you need to have a much bigger area than the [European] subcontinent.”

Peters said that to achieve a fully renewable energy system Europe would have to depend on generation from beyond its borders, for example from wind farms stretching from West Africa to Siberia.

It is doubtful whether European leaders would find this palatable. 

Gas from Russia and North Africa

While it is true that Europe currently relies on gas from Russia and North Africa, a key strand of the European Union’s present energy strategy involves trying to increase stored reserves so the continent can survive supply bottlenecks.

Europe is looking to store enough natural gas to become self-sufficient for periods of up to 90 days. A move to 100% renewable energy might limit that buffer period to mere hours, even with significant levels of storage.

Realistically, European energy systems may be able to cope with up to 25% renewable energy without losing stability, Peters suggested. Yet European policy is currently on track to increase that level.

“That is worrying me,” said Peters, who will be presenting a session called Harnessing Weather Analysis for Evaluating Grid and Residential Storage Business Cases at the Energy Storage World Forum.

“I don’t see any solution for phasing out fossil fuels in power generation without nuclear energy. However, it is a scandal that nuclear reactors have been built that are inherently unsafe.”

Does all this mean the energy storage industry is on a hiding to nothing? Peters does not believe so. To find out, watch out for our follow-up story next Friday.

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