Report: Electrothermal energy storage can yield consistent renewable electricity for industry

Move over, heat pumps and boilers — another player is rapidly rising through the ranks of industrial heat electrification and it’s brought energy storage with it. 

Electrothermal energy storage, which integrates heat electrification with heat storage, could allow industry to decarbonize heat while enabling more variable renewable power generation to come online, a new report from Systemiq and Breakthrough Energy found.

• The top line: By swapping electricity for fossil fuels in industrial heat generation, ETES provides energy storage that effectively translates intermittent renewable energy into steady supply. The report found that this could solve one of the biggest challenges of decarbonization: how to meet continuous industrial heat demands without overbuilding the grid. 
• The market grounding: ETES has anywhere from a 90% to 95% round-trip efficiency from grid electricity to heat. Coupled with a capex that’s half as much per kilowatt as grid-scale battery systems, ETES is more cost-effective than adding battery storage to electric boilers or even heat pumps in certain contexts. And, unlike batteries, ETES relies on widely available materials like bricks that don’t require costly and difficult to source critical minerals. However, the technology faces barriers to deployment at scale. 
• The current take: “Today’s electricity policy, regulatory and market mechanisms were designed with a very different electricity generation and demand system in mind,” the report said, noting that policymakers, grid operators, and tech providers can all help close the affordability and accessibility gap. “Changing electricity grid fees and market mechanisms are the most critical levers” to give ETES equal footing, the authors added.

An ETES system works by drawing electricity from the grid when power costs are low, and converting it into heat energy. Most of those currently on the market use sensible heat technology, where the energy is stored directly in a storage medium like bricks, lava rocks, concrete, or molten salt. They then deliver heat on demand to industrial sites as hot water or steam at temperatures up to 400 degrees Celsius. Temperatures up to 1,500 degrees are expected to be commercially available in the near future. 

Only six to 12 hours of charging per day are required for ETES to provide a continuous 24-hour heat supply, the report found, because the systems shift load to take advantage of periods of excess renewable electricity.

According to the report’s estimates, an ETES system can bring online about 2.6 times its own generation capacity from variable renewable power generation sources, which amounts to an extra 1.6 megawatts on average. The storage element enables flexible demand, eliminates the need for reductions in renewable power, and alleviates grid congestion during peak times. Neither heat pumps nor electric boilers can bring on generation capacity in this way, and ETES systems are cheaper than batteries.

ETES charging can also be shifted to off-peak times. The report indicates that deploying ETES instead of electric boilers could cause demand peaks to fall by up to 30%. Again, load shifting is key — this time, for keeping capex costs low and the growth in peak electricity demand lower. This could keep required investment in grid updates to a minimum.

Still, the road to widespread ETES deployment is still an arduous one, the report clarifies. Getting an ETES system connected to the grid can take up to 10 years in certain regions, as the technology hasn’t been prioritized by policymakers, it found.

And gaps still remain in terms of the affordability and accessibility of ETES systems compared to fossil fuel-based technologies. The report found that reforming grid fees, empowering flexible demand technologies to be fast-tracked for grid connection, and ensuring access to federal subsidies will accelerate market uptake of ETES. 

The latter isn’t unprecedented — Spain’s electricity price difference and grid fee structure allows ETES systems to charge cheaply, and has therefore been nurturing to the technology’s deployment. In Spain, ETES is expected to be cost-competitive with gas boilers by 2030.

According to the analysis, ETES is currently most widely applicable in the food and beverage, textiles, alumina refining, and paper, pulp, and print industries, with higher-temperature applications like steel direct reduced iron preheating not far behind. As the technology develops, ETES has the potential to play a role in meeting emerging demand for the manufacturing of sustainable aviation fuel and green chemicals.