Super-hot salt could be coming to a battery near you

There’s a lot going on in the climate world. Election workers are still counting and recounting votes in the US to determine control of Congress, and at the UN climate conference, delegates are heads-down in negotiations, battling over climate targets and finance agreements. 

We’re still waiting for more information about what these critical moments will mean for the future of climate policy and technology. While I keep my ears out for more definitive insights into what it all means, let’s take a break from the speculation and dive deep on something I think we should all be talking about more: batteries. 

I’m obsessed with batteries, and I’m always watching the wave of alternative chemistries that’s slowly percolating into the growing energy storage market. Some of these new players could eventually be cheaper (and in various ways, better) than the industry-standard lithium-ion batteries, but they often face real barriers to adoption. So let’s take a look at one startup’s journey to store energy using super-hot salt. 

Why we need new batteries

The world is building more capacity for renewables, especially solar and wind power that come and go with the weather. So, long story short, we need to be able to store energy. (I went more into this a couple weeks ago in the newsletter, check that out here if you missed it.)

Pumped hydropower accounted for over 90% of worldwide energy storage as of 2020. While hydro is a cheap, effective way to store power, it comes with environmental concerns and major constraints on where it can be installed, since it requires large bodies of water.  

Batteries make up most of the rest of today’s energy storage capacity, and will likely account for the bulk of energy storage market growth as well in the coming decades. Today, lithium-ion batteries are most common, similar to the ones in your phone or electric vehicle. 

Over decades of development and scaling, lithium-ion batteries have gotten cheaper, and production capacity has exploded, with new battery Gigafactories popping up all around the world seemingly every other week. 

But there are a few mismatches between lithium-ion’s strengths and what’s needed in batteries used for stationary energy storage.

  • Price: Grid-scale storage needs to be dirt-cheap to help renewables be affordable. Last year, the US Department of Energy set a goal of reducing costs by 90% by 2030. Lithium-ion batteries have gotten cheaper over the years, but gains may be plateauing, especially with possible material shortages expected. 
  • Size: Lithium-ion batteries pack a lot of power into a small space. But while battery size is important for things like phones and cars, it’s not so crucial for grid-scale energy storage. Compromising on energy density for stationary applications could mean lower cost. 
  • Lifetime: Industrial plants often put in equipment that, when maintained, lasts for decades. Lithium-ion batteries typically need to be replaced every 5-10 years, which can be pricey.

How hot salt can help

With the mismatch between lithium-ion batteries and our future energy storage needs, it seems like everybody is working on an alternative way to store energy. In just the last year, I’ve covered iron air and iron flow batteries, plastic ones, and even one startup using compressed carbon dioxide to store energy

Now, another technology is making the jump from the lab to the commercial world: molten salt. 

Ambri is a Boston-area startup that’s building molten-salt batteries from calcium and antimony. The company recently announced a demonstration project deploying energy storage for Microsoft data centers, and last year it raised over $140 million to build its manufacturing capacity. 

The company says its technology could be 30-50% cheaper over its lifetime than an equivalent lithium-ion system. Molten salt batteries can also exceed 80% efficiency, meaning that a relatively low amount of energy that’s used to charge the battery is lost to heat.  

Ambri was founded in 2010 based on research from Donald Sadoway’s lab at MIT. The goal was to develop a low-cost product for the stationary storage market, says David Bradwell, the company’s founder and CTO. 

The inspiration came from an unlikely place: aluminum production. Using similar chemical reactions to what’s used for aluminum smelting, the team built a lab-scale, low-cost energy storage system. But turning this concept into a real product hasn’t been so straightforward.

The magnesium and antimony-based chemistry the company started out with proved difficult to manufacture. In 2015, after continuing issues with the batteries’ seals, Ambri laid off a quarter of its staff and went back to the drawing board. 

In 2017, the company pivoted to a new approach for its batteries, using calcium and antimony. The new chemistry relies on cheaper materials, and should prove simpler to manufacture, Bradwell says. Since the pivot, the company has worked out technical glitches and made progress on commercialization, going through third-party safety testing and signing its first commercial deals, including the Microsoft one. 

The Microsoft energy storage system. Image courtesy of Ambri.

There are still major challenges ahead for the startup. The batteries operate at high temperatures, over 500°C (about 900°F), which limits what materials can be used to make them. And moving from single battery cells, which are about the size of a lunchbox, to huge container-sized systems can present challenges in system controls and logistics. 

That’s not to mention deploying a product to the real world means “dealing with real world things that happen,” as Bradwell puts it. Everything from lightning strikes to rodents can throw a wrench in a new battery system. 

At least one thing has changed over the last decade though: the market. Investors and even casual observers used to push back on whether anybody would want energy storage, Bradwell says. Now, the only question seems to be how quickly the industry can grow.

It will take time for Ambri and other new battery outfits to scale manufacturing and prove that they’ll be a viable, affordable alternative to existing batteries. As Bradwell says, “the journey continues.” 

Keeping up with Climate 

Disagreements about climate goals are hanging over COP27, the UN climate conference. Some leaders want to reaffirm the need to keep warming to 1.5°C, even as the target seems to be slipping out of reach. (New York Times)

Delegates at COP27 are still deep in talks over loss and damage funding for climate change impacts. (Bloomberg)

→ If you missed it, check out last week’s newsletter for more on why this funding is at the center of the talks.

The US is working to cut the influence of China in climate tech manufacturing. But the move could make some technologies more expensive and slow progress on climate goals (Grid News)

→ Meanwhile, the US and China are restarting climate talks. (Washington Post)

Republican gains in the US midterms were limited, quelling some renewable energy advocates’ concerns that Congress would dismantle recent climate action. (Inside Climate News)

The electric revolution has two wheels. About 40% of motorcycles and other smaller vehicles sold last year were electric, a much higher fraction than larger passenger vehicles. (Protocol)

We’re getting a better idea of AI’s climate impacts. Researchers developed a new approach to understand emissions from large language models, which require a huge amount of energy to train and run. (MIT Technology Review)

Organic solar cells are getting better. The technology could open up new applications for solar, since organic cells are light and flexible, but they’ll need to also be durable and easily-manufactured to break into the market. (Science

Electric trucks are coming, bringing with them wild requirements for the grid. By 2035, a truckstop could require as much power as a small town. (Bloomberg)

Grids may be able to handle fleets of short-haul delivery trucks, but long-range trucking poses a greater challenge. (MIT Technology Review)

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