🌐 Hot Rocks: The Battery That is Changing Industrial Energy

I Remember When Amazon Just Sold Books... 

It was 2003. I logged on to Amazon to buy a book—simple. But suddenly, I was sorting through laptops, blenders, and basketballs. Where was A Farewell to Arms? It felt like the earth was off-kilter.

My first reaction? What the hell, Amazon? You’re supposed to be a bookstore!

Technology disruption has a way of sneaking up on us and shifting our reality when we least expect it. We go about our routines, thinking the world works one way, and then—bam! Everything changes.

The same is happening now with batteries, including the very definition of a battery.

Batteries Are Reshaping the World

For most people, batteries are still an afterthought—something you replace occasionally in a flashlight or remote control. But that’s changing fast.

We see it most vividly with electric vehicles. While only 10% of Americans drive one today, adoption is nearing a tipping point.

Why? Because battery technology is on the cusp of breakthroughs to address cost and range anxiety concerns.

EV range has tripled in the last 13 years, hitting 283 miles per charge in 2024.

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We’re about to reach the sweet spot in EV driving range that prospective buyers have been waiting on for over five years.

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In addition, battery prices are plummeting—Goldman Sachs projects that EVs will reach price parity with gas-powered cars next year.

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And it’s not just transportation. The residential battery storage market is booming as more homeowners pair solar with batteries from Tesla, sonnen, Generac, Solaredge, Enphase, and others—a low-carbon trend we explored in Episode 2 with ES Solar’s battery storage power play in Utah.

But the real battery revolution isn’t happening in cars or homes.

It’s unfolding where almost no one is looking: the power grid and industrial manufacturing.

The Grid Battery Boom

A decade ago, grid-scale battery storage was a non-starter. Today, it’s table stakes for utilities worldwide.

That’s because no one imagined solar and wind—intermittent power sources that benefit greatly from batteries to store their energy—would become not just the cheapest but the fastest-growing energy sources in human history.

Daily announcements of new grid storage projects are now commonplace. Last month, Britta von Oesen, Partner and Managing Director at renewables investment bank CRC-IB, joined me on the podcast to talk about cleantech financial innovations that are accelerating this trend.

This momentum is unprecedented. Yet, it still leaves out what might be battery technology’s biggest opportunity to decarbonize the global economy:

Heat.

Heat Is Everything

There’s no modern world without industrial heat.

Toothbrushes, laptops, cars, coffee mugs, books, bikes, backpacks—even an REI tent you’ll use once and store indefinitely—all require heat at some stage of production.

Industrial heat is one of the biggest and most stubborn sources of carbon emissions, consuming nearly 25% of global energy.

Manufacturers and energy-intensive industries are locked into fossil fuels because of:

• High switching costs

• Complex retrofits

• Tight operating margins

• Limited CapEx budgets

But a new class of thermal energy storage (TES) batteries is rewriting the rules—storing heat and replacing legacy fossil-fuel equipment like natural gas boilers, furnaces, and kilns with a cleaner, cheaper, and more efficient alternative.

Brenmiller’s Hot Rocks

There are many ways to store heat—water, salt, sand, and bricks all work. Israeli-based Brenmiller does it with crushed rocks.

Avi Brenmiller saw this future clearly back in 2012. A titan in the solar thermal energy industry who served as CEO of Siemens’ solar thermal business unit and Solel Solar Systems (which Siemens acquired in 2009), Brenmiller decided his next move would amount to a pile of rocks.

He assembled a world-class team, self-funded research and development, received numerous patents, and took Brenmiller public on both the Israeli stock exchange and the Nasdaq as capital requirements grew.

Today, Brenmiller operates the world’s first gigafactory for heat batteries.

While it’s a climate tech startup success story, Brenmiller is also a family business. Avi’s son, Nir, is the COO, and Doron is the Chief Business Officer.

For Doron Brenmiller, the key to adoption is a simple principle: Make it easy for customers to say yes.

Brenmiller’s Biz Dev Playbook

For manufacturers to embrace thermal batteries, the solution must check three boxes:

✅ Seamless integration – Heat batteries must function as drop-in replacements for legacy equipment like natural gas boilers.

Brenmiller’s batteries generate heat from grid electricity and direct renewable sources. They then deploy it as hot water, steam, or pure heat at precise temperatures and pressures to match customer needs.

✅ Performance certainty – Manufacturers don’t gamble on unproven tech.

Brenmiller co-locates its heat batteries alongside fossil fuel-powered systems, allowing customers to scale up gradually and ensure the batteries are reliable before transitioning fully to clean heat.

✅ Minimal upfront costs – Capital expenditures must be low or nonexistent.

Brenmiller’s Heat-as-a-Service model removes financial risk. Customers don’t buy its heat batteries outright. Instead, they pay only for the heat they use, and Brenmiller manages installation, operation, and maintenance.

Who’s Using It?

The demand is real.

🐶 In Hungary, a pet food company is using Brenmiller’s heat battery.
🍺 In Israel, Heineken and Pepsi beverage plants are making the switch.

Hospitals and universities (including SUNY Purchase University in New York) have signed on. Different industries, same challenge, same solution.

From the outside, Brenmiller’s system looks like a shipping container. Inside, it’s a thermal powerhouse—it circulates warm liquid in pipes through crushed rocks, heats them to temperatures up to 1,000°F, and stores the energy for hours or even days.

The Future of Heat Is Here

Every manufacturer knows they need to decarbonize. But slim margins and risk aversion make change difficult.

That’s why Brenmiller’s approach—phasing in its technology alongside existing systems—makes the transition easier.

Batteries are revolutionizing electricity. Now, they’re coming for heat, and the transition is just a drop-in replacement away.

We may never see $2 eggs by the dozen again, but the key to driving down inflation on countless consumer products might very well be driving up the efficiency of producing, storing, and deploying heat.

Listen to this podcast episode on Apple, Spotify, YouTube, and all other platforms.

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Number of the week: 50%

That’s how much of the world’s energy is used exclusively for heat. It’s more than for transportation (30%) and electricity (20%). 

Quote of the week: 

“Where we’ve got to get to is where people three or four years from now are using these things and they go, wasn’t this the way it always was?’’

—Steve Jobs, speaking at the 1983 Aspen International Design Conference

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Related

Rondo Stores Heat in Bricks

Many thermal storage startups are racing to catch up to Brenmiller.

The closest is Rondo, whose technology channels heat into bricks that can reach 1500°C, much like a supercharged toaster. In Kentucky, the company is introducing heat batteries to make Bulleit Bourbon with Diageo. In Europe, Rondo recently raised €75M to scale with chemical, food and beverage, and clean energy customers. Breakthrough Energy and the European Investment Bank backed it.

Antora uses graphite blocks (the same material found in lead pencils) as its heat-storing medium. Last year, the company added $150 million in venture capital funding, bringing its total capital raised to $230 million to reach commercial-scale manufacturing at its facility in San Jose, CA. The company currently works with Con Edison on clean heat projects in New York.

Other promising startups include Kratfblock (recycled pellets from steel slag and furnace waste),  Fourth Power (graphite), and Calectra (firebricks).

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