This startup wants to use cheap surplus clean energy to make high-temperature industrial heat

A Bay Area startup says it has a new solution for one of the most stubborn problems in the transition to clean energy: replacing the fossil fuels burned for high-temperature cement production with a climate-friendly alternative.

Rondo Energy has constructed and carried out a pilot project and is now building a plant at a customer’s site. The idea is to demonstrate that excess renewable electricity can be converted into round-the-clock heat at temperatures in the thousands of degrees Fahrenheit.

A success in this sector could have ripple effects that spread throughout the building industry. Architects and engineers are grappling with the greenhouse gas emissions stemming from the production of cement, which is a key ingredient in concrete, the most commonly used building material on earth.

Cement is responsible for about 7 to 8 percent of all global carbon dioxide emissions. Between about a third and a half of those emissions come from the coal and natural gas burned in the kilns that make cement.

Rondo wants to replace that fossil heat — typically in the range of 1,800 to 2,700 degrees F, up to 24 hours per day — with electric resistance heating produced with excess renewable power.

“This is a fundamentally new tool in the decarbonization toolbox,” said Rondo Energy CEO John O’Donnell. ​“The high temperature is a problem there has not been a solution for.” 

In fact, this new approach wouldn’t have been possible even just a few years ago. 

The rise of abundant renewable electricity in some parts of the world has led to overproduction during certain periods of the day, as with solar power in California. That overabundance drives down power prices at certain hours, and at some points even forces solar and wind power production to be halted because there isn’t enough demand for it.

Rondo takes excess renewable energy and converts it to high-temperature heat via electrical resistance, the same technology used by a traditional electric stove or a toaster. The high heat is then stored in a rock or mineral material that is insulated so the heat stays in.

Bob Epstein, co-founder of cleantech entrepreneur group E2 and a member of Project 2030, a group focused on decarbonization in California, has been watching O’Donnell’s progress with Rondo. ​“He takes eight hours of electricity and turns it into 24 hours of heat. And the eight hours of electricity don’t have to [occur] all at one time,” Epstein said.

Can the technology work?

Rondo claims it can create high heat and store it with near 98 percent efficiency using common insulation material. O’Donnell said the heat can be delivered continuously to cement kilns, though he declined to offer more specifics on the technology.

The basic idea of converting electricity to high heat ​“sounds believable as far as getting to those types of [temperatures] with resistance heating,” said Ian Riley, CEO of the World Cement Association.

And it’s possible to perform that conversion efficiently, said Peter Saundry, a physicist who teaches environmental technology at Johns Hopkins University. But he questioned the 98 percent efficiency claim, calling it ​“way too optimistic.”

Rondo’s idea seems to rely on a material that can conduct heat quickly to capture the windows of time when lots of cheap renewable power is available, Saundry said. Minerals don’t usually conduct heat that well.

“But if they can get to 85 or 90 percent [efficiency], they’ve got some really good technology,” he said.

Converting an intermittent source of zero-carbon electricity into continuous high heat is an example of what’s called ​“indirect electrification.” 

At a recent workshop held by the California Energy Commission, Rondo representative Jon Costantino asked the agency to include indirect electrification in the state’s research budget. 

The company is also pushing the California Air Resources Board to require that a certain percentage of industrial heat be renewable — a renewable thermal standard, similar to the clean electricity standards that many states have. The company said an RTS should be part of California’s forthcoming plan to reach carbon-neutrality by 2045, known as the 2022 Scoping Plan Update.

Rondo is also part of a group of businesses called the Renewable Thermal Collaborative that is looking for zero-carbon industrial heat and HVAC solutions.

One competitor for Rondo’s technology is green hydrogen, which is also generated from renewable energy and can also be stored. But the infrastructure for green hydrogen does not exist yet, and the electrolyzers needed to produce the hydrogen are expensive. Some industry observers believe wide-scale deployment of clean hydrogen is still years away.

Some technologies in overlapping markets could also be seen as potential Rondo competitors. Energy Nest and Siemens Gamesa Renewable Energy both have thermal storage options, though not necessarily reaching the same high temperatures as Rondo claims its process can and not necessarily derived from 100 percent clean energy. The Department of Energy says it is in late-stage testing of a prototype that can store high heat that it calls Enduring, but the intention is to turn that heat back into electricity, not use it as heat.

It’s unclear how Rondo’s technology might scale up to serve a global cement industry, given that the conditions that result in a consistent supply of excess renewable energy exist in limited markets today. But O’Donnell’s view is that the markets are not so limited: They exist in the U.S. Midwest and Southeast as well as California, and also across Europe, in parts of the Middle East and in Australia. He argues they will exist everywhere in the future.

Locking down funding for unproven technologies like Rondo’s is notoriously difficult, as the experience of O’Donnell’s prior company indicates. He founded GlassPoint, a solar thermal company that planned to use concentrated solar collectors to generate steam. These would replace gas-burning steam generators in heavy oil fields. GlassPoint was venture-backed but wasn’t able to raise enough capital to carry out its plans to lower the emissions from extracting crude oil in California or Oman.

Now solar PV has gotten so cheap that making electricity first and then converting it to heat is cheaper than making the heat directly. And there is more attention focused on the need to clean up high heat than there was when GlassPoint launched.

The cement industry needs clean energy

Rondo takes its name from a musical form in which the same melody recurs again and again. ​“Some of us have been working together for 15 years on solving this problem,” O’Donnell said. He credited his wife, a musician, with suggesting the name.

Meeting cement production’s heating needs with clean energy still won’t eliminate all of its carbon dioxide emissions. Fifty to 65 percent of the emissions come from the chemical reactions of the raw materials that go into the kilns, namely, the decomposition of calcium carbonate into lime.

But the remaining 35 to 50 percent of emissions, which result from burning coal or natural gas to heat kilns, are what Rondo aims to address. It’s been a tough challenge, but with the changed economics of renewable electricity, O’Donnell now considers it doable.

Professionals working in the field of construction and building are eager for a win on industrial heat. It would change the carbon calculations for all their concrete, affecting the emissions of nearly every project. One of those people is Jennifer Mitchell, senior manager for workplace at LinkedIn and a philanthropist trying to clean up the concrete industry.

Just knowing that there are investments going into finding the right solution for the industry and passionate people putting their time and energy into the challenge inspires her. It is ​“a completely different conversation than we were having 10, even five years ago,” Mitchell said.