Pixley Heat Battery

Executive Overview

The Pixley Heat Battery is a 2 MWh Rondo Heat Battery (RHB) deployed at Calgren Renewable Fuels' ethanol biorefinery in Pixley, Tulare County, California. Commissioned in 2023, it was at the time the first electric thermal energy storage (ETES) system in commercial operation in the United States and the highest-temperature ETES system in commercial operation worldwide. The system is operated under a Heat-as-a-Service (HaaS) financing model — Calgren pays per unit of heat delivered, with no upfront capital required. The RHB stores renewable electricity as heat at temperatures exceeding 1,000°C, then supplies that heat on demand to the ethanol production process. Battery modules were manufactured in Alameda, California; other major elements in Bakersfield, California. The system was installed and commissioned without a single hour of facility downtime.

How It Works & Differentiation

The Rondo Heat Battery stores electricity by resistively heating ceramic refractory bricks to temperatures exceeding 1,000°C. Heat is discharged on demand as steam for Calgren's industrial processes, replacing the natural gas-fired heat that previously supplied the refinery. Documented system efficiency exceeds 90%; larger RHBs store energy at over 98% efficiency. The key differentiation in an ethanol biorefinery context is carbon intensity (CI) impact: approximately half of liquid biofuels' total carbon emissions come from fossil fuel combustion during refining. By replacing that fossil heat with renewable electricity, RHBs can reduce the CI of ethanol production by up to 50%, doubling CO₂ savings per gallon under California's Low Carbon Fuel Standard (LCFS). The system also eliminates NOx, SOx, and fine particulates from combustion. Heat delivered per MMBtu costs less than equivalent gas-fired heat.

Commercialization & Traction

The Pixley deployment was Rondo's first commercial installation in the United States, preceding the Holmes Western (100 MWh, Kern County CA), SCG Thailand (33 MWh, cement), Covestro Germany (100 MWh, chemical), and Heineken Portugal (100 MWh, brewing) deployments. The HaaS structure removes the primary adoption barrier for industrial customers — upfront capital — while aligning Rondo's revenue with delivered thermal energy. The LCFS credit value generated by CI reduction provides Calgren with a direct monetisable return from the system, creating an energy cost benefit that makes the economics self-reinforcing within California's carbon market framework.

Scalability & Strategic Context

The Pixley project is the foundational proof point for Rondo's industrial heat decarbonisation thesis in the U.S. biofuels sector. Ethanol refineries are ideal RHB customers because they operate continuous, predictable thermal loads matching the RHB's constant-output profile, and have direct financial exposure to carbon intensity through LCFS compliance. There are approximately 200 ethanol refineries in the United States, representing a significant addressable market for 2–20 MWh heat battery deployments. The Pixley case study also establishes the template for combining RHBs with carbon capture in biofuel production, which Rondo has identified as a pathway to zero or negative CI fuel.