Imagine roasting coffee using sunlight collected days earlier.
That is exactly what researchers at Sandia National Laboratories in the United States are working to achieve with a new thermal energy storage system that stores solar heat in a bed of rocks and releases it whenever it is needed.
The technology is being tested in partnership with Michael Thomas Coffee, a local coffee company, and could eventually help food and beverage businesses reduce their use of natural gas while improving efficiency.
Unlike conventional coffee roasters that burn natural gas, the new system is powered by solar energy.
Electricity generated by rooftop solar panels is used to heat a specially designed bed of rocks.
The rocks act like a thermal battery, storing heat at temperatures as high as 600°C (1,100°F). When it is time to roast coffee, the stored heat is released and directed into the roasting drum.
One of the biggest advantages of the system is that the heat can be stored for long periods. Instead of needing sunshine at the exact moment coffee is roasted, businesses can collect solar energy during the day and use the stored heat that night or even several days later.
The research team hopes the technology can be added to existing coffee roasters rather than requiring businesses to purchase completely new equipment.
This means coffee roasters could continue using the machines they already know while switching to a cleaner energy source.
Coffee roaster Michael Sweeney has been working closely with Sandia engineers to test the new system. During recent trials, he and his daughters roasted batches of coffee ranging from light to dark roasts using solar-powered heat.
The early results have been encouraging. Researchers found that dark roasts were completed a few minutes faster than with traditional gas-powered roasting. The system also allowed the roasting equipment to heat up and cool down more quickly, making it possible to begin the next batch sooner. This could help coffee businesses produce more roasted beans in less time.
The findings are similar to an earlier Sandia project that successfully used solar energy instead of propane to roast New Mexico green chile. In those tests, roasting time was cut in half while producing more evenly roasted peppers.
For the Sweeney family, coffee is about much more than simply heating beans. They believe great coffee begins with carefully sourced beans, understanding where they come from and roasting them with precision. Their company buys small batches of coffee from women farmers in Guatemala and offers more than 30 varieties.
The researchers see coffee roasting as just the beginning. They believe the same thermal energy storage system could be adapted for many other industries that require high-temperature heat. Potential applications include roasting grains for breweries, roasting cocoa beans for chocolate production and processing many other food products.
Sandia is also working to patent the technology and partner with companies that can bring it to market. The goal is to make clean industrial heating more widely available, helping businesses lower energy costs while reducing fossil fuel use.
If successful, this rock-based thermal battery could become a practical way for manufacturers and food producers to capture abundant solar energy during sunny hours and use it whenever they need it, making renewable energy more flexible, reliable and useful for everyday industry.
