21 May 2024
8 min

The production of industrial heat with renewable energy, on global level, is one of the greatest ways of combat climate change on a large scale. And a unique opportunity to further accelerate decarbonisation.

Announced during the 3rd EDP Business Summit on 7 March, this partnership between EDP and Rondo Energy aims to establish a new market: the supply of clean, affordable industrial heat on a large scale from wind and solar energy. EDP plans to develop up to 400 MW of wind and solar projects to feed up to 2 GWh of Rondo’s thermal batteries.

EDP’s decentralised solar projects will be installed next to Rondo’s Thermal Batteries, in a combustion-free and safe solution to decarbonise companies that use heat, from food and chemical industries to large industrial complexes.


This partnership unlocks a new market by progressively replacing fossil fuels burned to produce industrial heat, which currently releases 15% of the world’s CO2. Just to get an idea, the implementation of thermal batteries could reduce global CO2 emissions by 20 per cent and eliminate fossil gas combustion by up to 40 per cent, according to SystemIQ’s latest study on industrial heat.

How batteries work

Rondo’s thermal batteries capture intermittent electrical energy and convert it into continuous hightemperature heat, with the option of also providing continuous energy through a cogeneration configuration. A revolutionary technology explained by Rondo’s founder, John O’Donnell, CEO of Rondo Energy (read the interview).

The first projects in this partnership are due to come on stream in 2025, marking a significant step towards a more sustainable and carbon-free future.

How does the Rondo heat battery work?


1Electricity conversion

2Heat storage efficient, 24/7

3Heat delivery on demand as heated air or steam


John O’Donnell - CEO of Rondo

In this interview, Rondo’s CEO explains the basis of this innovative heat storage technology and what we can expect in the near future in this area.
What does it mean Rondo?

A Rondo is a 17th-century musical form where the same melody comes back again and again. My wife is a musician, and when we were putting the company together, a group of us had previously been working on clean, renewable energy for a long time. With another technology, we previously delivered more than half of all the solar industrial heat in the world, and we were getting the band back together to do it this new way.

Can you present Rondo Energy, the company and technology?

Rondo Energy is building infrastructure for industry in the 21st century. The industry needs huge amounts of energy, and in lots of industries, the cost of energy is a huge portion of the cost of producing commodities, whether that’s making fabric plastic baby food or steel. In the 21st century, the industry urgently needs zero-carbon energy, and it needs to be affordable. For decades, we’ve looked for ways to get zero-carbon energy, and for industry, and people have said, it’s the hard-to-decarbonise sector. It’s never going to happen. It’s decades away.

The wind and solar industries crashed the cost of intermittent electricity. Solar electricity is now the cheapest form of energy humans have ever had since we were a species, and if we had an energy storage technology that was cheap enough, we could repower industry, and meet that cost requirement. Well, three-quarters of the energy used by industry is heat, not electricity. We’ve been doing a lot of stuff for electricity storage, but industrial heat alone is a quarter of all the coal, oil, and natural gas we burn in the world, and so we need storage for heat, not electricity, to replace that. That’s what we’re doing at Rondo, building energy storage that is delivering heat from electricity. 

It turns out that’s a lot cheaper and simpler than storing electricity for electricity. All the technologies we have for storing electricity use chemistry, and they use critical materials. Storing heat, you know, put a brick in your oven. When it’s hot, put it in your oven. Put it in your bed.

You can store heat and keep your feet warm all night. We’re in this new era where intermittent electricity is cheap, and there are now dozens of companies working on building heat batteries. Tesla wrote a report recently that said that the world is going to have twice as much heat battery capacity as grid batteries of all kinds because they are the cheapest solution for decarbonising energy.

At Rondo, we’re the folks who have been working on industrial heat the longest, and we were looking for the thing that could go the fastest. And Rondo found a way to use a 200-year-old technology with one new insight to build this infrastructure for the 21st century. We store electricity, as heat, using brick. And we build industrial energy equipment. We build industrial boilers that sit in large factories, giant refineries, and little dairies that are powered by intermittent electricity. We’re excited to be working with EDP as one of the world leaders in building renewable electricity and taking this tool that we’ve built and putting it to work for customers.

Why is so revolutionary?

Yeah, the world needs decarbonised heat, and this is a revolution. All these other pathways that the world’s been working on for years all would mean that decarbonised heat would be more expensive than heat today. Capturing carbon, which is one of the ideas that’s always been out there, is always 30 to 50 per cent more expensive than just burning fuel and not capturing the carbon. Processes like making hydrogen from electric power are 50 per cent efficient. It’s two units of electricity for one unit of heat. So there are a lot of ways to do it to provide decarbonised heat that are more expensive than today. And, you know, one of the things people talk about is what the decarbonised world looks like? Is it more expensive for the least wealthy in our communities to buy food and diapers and everything?

Or is it less expensive? Is the energy transition going to make the world more unjust or more just? And we have intermittent wind and solar that are cheaper than fuel today. If we can harness them, we can build a world that’s clean but also more just and safer. And that’s one of the things that we’re most excited about because the missing link for doing that is an energy storage technology that we can manufacture at a large scale, that we know works so that it can be financed by customers and by companies who plan to put it to work for decades.

And that’s what we’ve done. And also, that you can just use it without having to change infrastructure. People change their factories every 30 years. We need to do things right now. We need drop-in solutions that we can connect to the factories that we have right now.

And that’s what’s important about what we’re doing. Other pathways require completely changing how we manufacture something. Many of those will be decades in the future. This is something that seems kind of boring, just using this brick material to store heat. But it turns out to unlock very rapid action at scale.

What makes Rondo in the EDP partnership?

EDP, if I understand correctly, is the world’s largest builder of commercial and industrial solar energy. EDP is a trusted partner for industries around the world building decarbonising facilities for them. And EDP takes solar technologies, other kinds of storage technologies, and puts them to work so customers can buy clean energy as a service. If you’re in the business of making baby food, you don’t need to know about how solar panels work. And you can put your capital to work in your own business.

Rondo has built this fundamentally new kind of energy storage. And our focus is delivering these heat batteries. But it’s a tool. And again, the customer who’s making baby food doesn’t want to own heat batteries any more than they want to own solar panels. They want someone to deliver them a reliable, guaranteed source of energy as a service.

And so from our standpoint, we see EDP as a super technical group that we can focus on working with, we can learn to work together, and we can go big and go fast putting this tool in the hands of customers and having them use it. I mean, I could not be more excited.

What are the main functions of the Rondo heat battery, and how it achieves each of these functions?

The Rondo heat battery does what any heat battery has to do. It has to do three things. It has to capture electricity from the grid when the wind is blowing when the sun is shining. So we have to capture electricity intermittently. And the faster we can get it and capture that energy, the cheaper that energy can be, the more valuable the battery can be. So step one, capture energy.

Step two, store energy long enough for many hours so that the energy that we captured briefly during the day is enough so that we can do step three, deliver energy continuously

We designed the Rondo heat battery to be the best once a year for inspection. So that means we’re taking intermittent energy and we must deliver energy continuously. So those three things, the Rondo heat battery takes electricity and uses the same heating element material that is on your kitchen counter in your toaster. Those heating element wires; electricity heats those wires with resistance. Those wires give off energy and they give off light. They give off infrared and visible light and the way your toaster heats bread, that light warms the bread uniformly. A small amount of heating element wire warms the whole surface of the bread uniformly

Inside the Rondo heat battery, that’s exactly the way we store energy. A small amount of heating element wire inside a 3D checkerboard of thousands of tons of brick stores huge amounts of electricity as heat and heats that brick to over a thousand C. So it’s glowing, it’s not even glowing red hot, it’s glowing yellow hot inside. So that’s surrounded by insulation so we can store energy for days. We build our heat batteries with enough energy storage so that they can do energy continuously.

The way they do that, is we circulate inside the heat battery, we circulate air through that super-hot brick. Superheated air comes out that now flows across a boiler. The boilers at industrial facilities, many of them, most of them, run on superheated air. Some pipes carry water that makes superheated steam from the heat in the air. So a Rondo heat battery has electrical heaters inside brick and next to it a boiler where circulating air pulls heat out as superheated air makes steam and is returned so that it’s a single box with a connection to the electricity substation on the other.

Over 30 years of innovative solutions

John has over 30 years of experience taking novel solutions from conception to reality across the energy, semiconductor and supercomputer industries. Prior to founding Rondo, John served as co-founder and vice president of development for GlassPoint Solar, which delivered solar industrial heat worldwide. He previously cofounded and led Ausra, a pioneer in solar thermal electric systems. John served as a lead engineer for Princeton Plasma Physics Laboratory, where he designed award-winning technology to support fusion experiments. He is a published author of numerous technical papers and holds more than 20 patents in the U.S. and internationally. John earned a B.Sc. with Special Distinction in Computer Science from Yale University.

John O'Donnell, CEO of Rondo

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