Sandia collaboration uses solar energy to roast coffee beans
COFFEE ROASTING — Shots of the experiment to use thermal energy stored from the sun to roast coffee beans at the National Solar Thermal Test Facility. The project is a collaboration with Albuquerque-based Michael Thomas Coffee. (Video by Ruth Frank)
On a crisp fall day in New Mexico, coffee roaster Michael Sweeney joined Sandia engineers to see if sunlight could bring new energy to an old tradition.
Sweeney, who owns and operates Michael Thomas Coffee in Albuquerque, has been collaborating with Sandia as part of a state-funded program to use solar energy to heat traditional coffee roasters. The partnership is exploring how energy technologies can spark innovation in one of the world’s most energy-intensive food crafts.
At Sandia’s National Solar Thermal Test Facility, Sweeney and the engineers roasted beans using a Labs-developed technology that stores energy generated from photovoltaic panels in a bed of rocks, which then releases the heat to power the roaster, reaching temperatures up to 600 degrees Celsius.
“We’re on the right track. This is how coffee roasting behaves,” Sweeney said as the beans tumbled inside the drum. “We’re doing great and we’re right at temperature.”
Nearby, Sandia mechanical engineer Luke McLaughlin adjusted how much heat the system released from the bed of rocks.
“This is indirect solar heating,” said Sandia systems engineer Ken Armijo, who is helping lead the project. “The solar energy charges heat electrothermally into a radial packed-bed energy storage system, which then discharges it into a drum to dry and roast coffee.”
Many benefits
The work is funded by New Mexico’s Technology Readiness Gross Receipts Initiative, or TRGR. The team aims to develop a bolt-on solution for existing natural gas-fueled roasters that allows them to use stored solar-thermal energy, with storage durations that can last for days.
“It’s not learning a new roasting machine,” Sweeney said. “It’s working with your current roaster that you know extremely well and just adapting to a different energy source.” With Albuquerque’s 300 days of sunshine annually, he added, “This is going to let me look at roasting literally in a different light and look at my craft from a different viewpoint.”
Beyond saving the cost of buying a new electric roaster, the project could improve efficiency, quality and productivity of traditional coffee roasting processes.
“Our work will allow Michael Thomas Coffee to install a near closed-loop system in their parking lot and use solar panels on top of their building to pump in hot air from the thermal energy storage system to facilitate industrial roasting,” Ken said.
Test time
During the experiment at the National Solar Thermal Test Facility, Sweeney and his daughters roasted coffee beans for light, medium and dark roast batches.
“It cut roasting time down by a few minutes for the dark roast,” Ken said. “That’s similar to what we saw with green chile roasting, where solar cut the time in half and the roasts were more uniform than traditional gas-fired roasting.”
He was referring to a 2022 experiment that used solar energy to roast green chile.
Sweeney added that during the coffee test, the roaster could be preheated and cooled more quickly, which means higher throughput by starting the next roast sooner, leading to more batches in less time.
Coffee craft
When asked what makes a great cup of coffee, Sweeney and his daughters, who help run the business, which is expanding to wholesale, agreed it’s both an art and a science.
“The story of coffee is complex. It’s so easy to mess it up, and so beautiful when we do it right,” Kate Sweeney said. “What makes us good is that we’re willing to learn, we’re willing to be wrong and we’re willing to grow.”
The family said that for individuals, it’s their personal ritual that makes coffee great. From the craft perspective, good coffee starts with sourcing quality beans and understanding their origin. Michael Thomas sources small-batch beans from women farmers in Guatemala and offers more than 30 varieties.
“It’s also making sure we’re roasting it to the best of our ability,” Kate said.
The collaboration with Sandia through a Cooperative Research and Development Agreement felt like a natural fit for Michael Thomas Coffee, whose values emphasize consistency, community and quality.
“The solar project is really helping us connect in a broader sense with the larger coffee industry,” Michael said.
More than coffee roasting
For Sandia, the end goal is to expand the technology to other applications and patent it so new solutions can enter the market for near-term commercial use across a range of industries.
That’s where Bob Sleeper comes in.
“My goal is to get this industrial heat and energy storage system into the hands of someone who can commercialize it,” said Bob, a Sandia licensing and business development specialist. To make that happen, Sandia is partnering with local food processing companies and startup studios like the DOE’s Boost Program to find an entrepreneurial team that can help bring the system to market.
“The storage system allows you to charge it one day and still use the heat at night or even days later,” Bob said.
The adaptable system could benefit other applications beyond coffee, from food processing to industrial manufacturing that uses thermally stored energy.
“This project is going to push the bounds of what we can do and save businesses money, particularly in the food and beverage industry,” said Ken, who comes from a deep heritage of family farming in New Mexico. “We can roast grains for beer, and we can also roast chocolate.”
For Sweeney and the Sandia researchers, the collaboration shows how the same science used to solve complex national challenges can also heat up practical innovations for American industry.