New Mexico Test Shows Solar-Stored Heat Can Power Drum Coffee Roasters

# What happened Sandia National Laboratories ran a state-funded test in New Mexico that used photovoltaic electricity to generate and store heat, then put that stored heat into a commercial drum roaster. The retrofit-style system was tested with Michael Thomas Coffee in Albuquerque and produced light, medium and dark roasts while reaching temperatures up to 600°C.

# How the system works The approach is called indirect solar heating. Photovoltaic panels generate electricity that is converted into heat and stored in a radial packed-bed filled with rocks. When the roaster needs heat, the system releases the stored thermal energy into the roasting drum rather than burning natural gas.

Sandia's setup draws on prior work. The lab tested concentrated-solar roasting on green chiles in 2022 and used the same thermal-storage technology covered in U.S. Patent No. 11,549,761 for the coffee experiment.

The trial produced usable roast levels across the spectrum. Sandia reported several operational benefits: the system hit high temperatures (up to 600°C), it reduced dark-roast cycle time by a few minutes, and it allowed the roaster to preheat and cool more quickly between batches. Faster thermal transitions could increase daily throughput for commercial operations.

# Storage and intermittency The rock-bed thermal-storage element can hold heat for extended periods, potentially days. That means a roasting operation could continue when the sun isn't shining, using stored heat generated during sunny periods. Albuquerque's climate — roughly 300 sunny days per year — made it a logical testing site.

# Funding and commercialization path The work is funded by New Mexico's Technology Readiness Gross Receipts Initiative (TRGR), which helps move lab technologies toward commercial use. The Michael Thomas Coffee project falls under a Cooperative Research and Development Agreement between Sandia and private industry. Sandia's licensing and business development staff highlighted the goal of getting the industrial heat and energy storage system into the hands of commercial entities that can scale and sell a retrofit product.

# What this means for roasters now For roasters that want to reduce natural gas use without buying new machines, the retrofit concept is the closest near-term option demonstrated so far. The test shows the core physics and controls can work on a commercial drum roaster, and that thermal storage can smooth solar intermittency.

Remaining questions for operators include retrofit cost, controls integration with existing combustion and airflow systems, long-term durability of packed-bed components under repeated thermal cycling, and the business case compared with electrification via resistive or induction heat or continued natural gas use.

# Bottom line Sandia's test demonstrates a feasible pathway to run conventional drum roasters on solar-derived thermal storage. The project emphasizes retrofitting existing equipment and storing heat in a rock bed to bridge gaps in solar availability, and the next steps are commercialization and real-world cost and integration studies.