BY JASON DEIGN:

The renewable energy technology developer Siemens Gamesa is hoping to turn existing thermal power plants into energy storage assets with a technology now under development.



The technology, which Siemens Gamesa has dubbed Electric Thermal Energy Storage (ETES), would be able to use thermal plant components to store gigawatt-levels of energy for days or weeks, a company spokesman said.

As renewable energy penetration increases on grids worldwide, “there will be a major need for large-scale storage,” said Siemens Gamesa project manager Till Barmeier at Electrify Europe in Vienna, Austria, last week.

For the levels of storage that will be required to ride over doldrums in Europe, he said, humanity will have to build out an energy storage infrastructure that is almost comparable in size to the thermal infrastructure already in place.

And that is on top of the renewable energy infrastructure that is being created to decarbonise the grid.

Building three infrastructures

Building three separate infrastructures and then getting rid of the first one “doesn’t sound like the smartest way of doing things,” Barmeier said, “especially since building one of those infrastructures is a lifetime’s effort.”

ETES is intended to avoid this with a very low-cost storage technology that could be retrofitted to existing power stations.

In a nutshell, it involves using excess energy and simple resistive heating to heat up rocks in an insulated container. Heat from the rocks can then be used to run a steam turbine and produce electricity.

The concept “allows for large-scale integration of renewable energy,” said Barmeier, as well making it possible to recycle heat from existing industrial processes.

Work on the technology has been underway since 2015, when Siemens began to develop a test plant called the Future Energy Solution (FES), funded by the German government.

The FES project

The FES project, built in collaboration with Hamburg Energie and the Technical University Hamburg-Harburg, showed that ETES could achieve a 5MWh charging capacity with a 700kW power input and 95% heat storage efficiency.

Today Siemens Gamesa reckons it can get a 50% AC-to-AC round-trip efficiency from the process. This, it said, makes ETES “the most efficient low-cost energy storage solution for large amounts of energy.”

Although ETES is made from off-the-shelf components, Siemens Gamesa has filed more than 60 patents related to the technology, covering features such as the charging cycle, thermal energy storage and integration into power plants.

At Electrify Europe, Barmeier cited a “full system cost” of €80 (USD$94) per installed kWh of capacity for a built-from-scratch system. For a plant reusing existing components, the cost could be half that level, he said.

This compares to a cost of at least $200 per kWh for lithium-ion batteries, as calculated by the International Renewable Energy Agency. ETES would “be able to supply dispatchable energy without emissions,” Barmeier said.

A 120MWh ETES plant

Siemens Gamesa is now building a 120MWh ETES plant on the harbour in Hamburg, Germany, which will enter operation next year.

After that, the company intends to build a gigawatt-hour-scale project that will be able to deliver energy continuously for up to a week. This should enter operation sometime in the next decade.

“What we are looking for now is a strategic partner,” Barmeier said.

The Siemens Gamesa work comes amid growing interest in very large-scale, long-duration storage.

Increasingly, experts are becoming aware of the fact that lithium-ion batteries can only cover a small portion of the energy storage requirements that will be present in 100% or near-100% renewable grids.

Use of excess renewable energy

This realisation is spurring technology developers to investigate the use of excess renewable energy to create hydrogen, methane or ammonia, as well as alternatives to pumped hydro storage.

ETES would fall into the latter category, along with technologies such as compressed air energy storage.

Also, Greentech Media this month reported on a US effort to create a new seasonal energy storage technology that has already attracted $9m in Series A funding.

The founders of Form Energy, which include former executives from Aquion and Tesla as well as storage experts from the Massachusetts Institute of Technology, do not expect to commercialise a product before the next decade.

Tellingly, the ‘product’ in this case is expected to be a storage infrastructure rather than a battery or the like, Greentech Media reported.

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