Rondo Energy Announces World’s Highest Temperature Thermal Energy Storage

Rondo Energy, a leading provider of zero-carbon industrial heat, and Calgren Renewable Fuels, a producer of the world’s lowest carbon intensity (CI) biofuels, today announced the start of commercial operation of a 2MWh Rondo Heat Battery (RHB) at Calgren’s facility in Pixley, California.

The Rondo Heat Battery captures intermittent renewable electricity, stores it at very high temperatures in brick materials, and delivers continuous industrial heat on demand. Calgren Renewable Fuels produces the world’s lowest CI ethanol, biodiesel, and renewable natural gas at their Pixley facility. Rondo is proud to be working with Calgren on this first step in further reducing both the cost of production and the carbon intensity of today’s biofuels. About half of the total carbon emissions of liquid biofuels comes from fossil fuel used in the refining processes. Rondo Heat Batteries eliminate these emissions by replacing fuel combustion with renewable electricity, dropping into existing facilities without process changes.

Without any process or feedstock changes, biofuels produced using clean Rondo heat and power double the CO2 savings per gallon.

The RHB is delivering heat to Calgren on a Heat-as-a-Service (HaaS) basis, supplying energy at a cost per MMBtu lower than gas-fired heat. Rondo’s HaaS enables industrial producers to enjoy low and predictable energy costs without upfront capital.

Rondo’s 2MWh deployment for Calgren Renewable Fuels is a milestone both for energy storage and for the future of ethanol production, for several reasons:

  • First-of-its-Kind Energy Storage: This is the first electric thermal energy storage (ETES) system in commercial operation in the U.S. ETES technologies are an important new tool for decarbonization because they deliver industrial heat using half as much electricity as green hydrogen.
  • Highest Temperature Heat: This installation is the highest temperature ETES system in commercial operation worldwide, storing and transferring energy above 1,000°C. Rondo Heat Batteries provide both industrial steam and the high temperature heat needed for producing steel, chemicals, and cement, using half as much electricity as hydrogen systems.
  • Lower Cost Energy: This project delivers cost savings to Calgren by reducing energy costs. Because energy is a major portion of total operating costs for fuel producers and other industries, lower cost energy improves industrial competitiveness, preserves jobs, and encourages investment.
  • Highest Efficiency Storage: This Rondo Heat Battery is among the highest efficiency energy storage of any kind in the world, with documented efficiency over 90%. Larger Rondo Heat Batteries store energy at over 98% efficiency.
  • Fast to Scale: Rondo Heat Batteries use only widely available materials and can be rapidly produced at the large scale urgently needed to decarbonize industries worldwide.
  • Made in California: The battery modules in this system were manufactured by Rondo in Alameda, California, and other major elements were manufactured in Bakersfield, California.
  • Local Air Quality and Jobs: By replacing combustion with renewable electricity, Rondo Heat Batteries eliminate the NOx, SOx, and fine particulates that are harmful to California communities, and reduce the cost of energy for some of California’s most important industries. Repowering industries with renewable electricity can keep California industries competitive in a low-carbon world, preserving jobs and improving air quality in their communities.
  • Zero-Carbon Ethanol: Rondo Heat Batteries can reduce the CI of ethanol production by 50%. When combined with carbon capture technology, they produce high-value fuels with zero CI; these fuels are very high value when used both for ground transport and for sustainable aviation fuel (SAF).

RHBs are designed to integrate seamlessly into both existing and new facilities. This RHB was installed and commissioned without causing a single hour of facility downtime.

“This partnership is one small step for Rondo and Calgren, and one giant leap forward for industrial decarbonization worldwide. We’re excited to be working with Calgren on this journey. Repowering today’s industrial facilities to drive deep decarbonization—this is what the energy transition looks like,” said John O’Donnell, CEO of Rondo Energy.

“From construction through commissioning, my team and I were impressed that the Rondo Heat Battery caused no disruption or slow-down to Calgren’s operations,” said Lyle Schlyer, President of Calgren Renewable Fuels. “We’re looking forward to this unit proving itself, because we see the Rondo Heat Battery as a potential “perfect fit” solution for us—a low-cost source of zero-carbon heat for our facilities that can extend our reach toward the lowest-carbon, highest-value biofuels produced anywhere.”

About Rondo Energy

Rondo Energy, the leading provider of zero-carbon industrial heat, makes industrial decarbonization possible—and profitable—today. The Rondo Heat Battery captures low-cost renewable electricity and delivers continuous high-temperature heat, enabling customers to power their operations with zero-carbon energy. Learn more at

About Calgren Renewable Fuels

Calgren and its affiliates have been producing renewable fuels in California's Central Valley for over a decade. Today Calgren’s Pixley facility produces some of the lowest carbon fuel ethanol available, as well as renewable natural gas made from dairy waste and low-carbon renewable biodiesel made from degraded waste grease without chemical catalysts. Calgren Pixley also supplies carbon dioxide for commercial/industrial use, exports excess cogeneration to the electrical grid, fuels its production facilities in part by the use of biogas from biodiesel wash water and other substrates, and is working with DOE on a hub storage project for captured carbon gases.