What Long Duration Energy Storage Is & Why It Kills Coal

December 2nd, 2018 by  on Clean Technica, “What Long Duration Energy Storage Is & Why It Kills Coal


US coal power plants were closing at a rapid clip before Trump came into office, and coal power has kept on bleeding out under his watch. The new R&D program practically guarantees that the hurt will continue for coal miners, their families and their communities long after Trump leaves office.

More And Longer (And Cheaper) Energy Storage

CleanTechnica has been following along with the Energy Department’s work on long duration battery systems since last May, when the agency announced it would provide $30 million in funding for R&D.

The agency envisions utility scale storage systems that can deliver power to 50,000 homes over a long period of time — and not just for a few hours. They want to see systems in the range of 10 to 100 hours, preferably 100.

As if that’s not enough, low cost is also a priority. In other words, the Energy Department wants you to have your energy storage cake and eat it, too.

That pretty much cuts out today’s go-to technologies for energy storage. Lithium-ion batteries would be too expensive to scale up. Pumped hydro fits the bill for duration and capacity, but suitable sites are few and far between.

So, what’s left?

The Long Duration Energy Storage Cake

For the record, the $30 million pot comes through a program called DAYS for Duration Addition to electricitY Storage (they kind of stretched the acronym but whatever). DAYS is under the umbrella of ARPA- E, the Energy Department’s office for high risk, high reward projects.

In the latest DAYS development, last week ARPA-E sealed the deal on an award to the National Renewable Energy Laboratory of almost $2.8 million to lead an R&D team focusing on thermal energy storage.

The project is called ENDURING for Economic Long-Duration Electricity Storage by Using Low-Cost Thermal Energy Storage.

If you’re thinking concentrating solar power and molten salt thermal energy storage, well, kind of. ENDURING is aimed at overcoming some of the cost and efficiency obstacles posed by molten salt technology.

The idea is to squeeze more efficiency out of the system by using low cost particles that can be heated to higher temperatures.

What particles? If you have an idea about that, drop a note in the comment thread. One hint: Sandia National Laboratory is working on a “falling particle” battery system based on a low cost ceramic material.

Another hint: one of the NREL team partners is a company called Allied Mineral Products, Inc. Another partner, Purdue University, is working on new composite materials for heat exchangers that can withstand high heat.

Rounding out the team are GE Global Research, Greenway Energy, Colorado School of Mines, and the company Power Engineers.

Here’s the explainer from the NREL team leader, Zhiwen Ma (break added):

When electric power is cheapest, electric heaters will ‘charge’ the storage modules by heating stable, inexpensive solid particles to more than 1,100 degrees Celsius.

And when it’s time to discharge this energy, the hot particles will move through a heat exchanger to heat a working fluid that drives a high-efficiency closed-Brayton combined cycle attached to an electric generator.

Got all that?

Aside from ditching molten salt, the new system can also eschew the need to hook up with an on site concentrating solar array. Electricity for heating the particles could come from just about anywhere, which would include wind farms as well as solar.

No Country For Coal Power

If you spotted that thing about “when electric power is cheapest,” you’re not the only one.

For a while there, it looked like coal stakeholders had one last shred of hope to hang on to: bigger and better batteries would help keep coal power plants in operation, by enabling them to sell more electricity during off-peak periods.

That kind of sort of makes sense, but the issue of fossil-friendly energy storage relates more to natural gas power plants than coal (as natural gas stakeholders will be happy to tell you).

For that matter, the DAYS program is quite clear that the aim of pushing the envelope on low cost battery systems is to enable more wind and solar grid integration.