Scientists roast green chili peppers "in the sun": a recipe against climate change

The family of Kenneth Miguel Armijo, senior research scientist and engineer at Sandia National Laboratories, has been growing chiles in New Mexico, USA, for nearly a century. "We've been doing it even since the state was part of the Mexican territory," he says. "Chili is part of our blood." 

Roasting green chile on top of Sandia National Laboratories' National Solar Thermal Test Facility. Roasting green chile with concentrated sunlight instead of propane produces tasty chile and reduces carbon dioxide emissions (CREDIT: Randy Montoya/Sandia National Laboratories).

Both in this state and in its family, chili is not only used in various recipes, but is also roasted to bring out its flavor. But this is a process that, unfortunately, is not so environmentally friendly, as the roaster used for the process is powered by propane, a fuel that emits greenhouse gases and thus contributes to climate change. 

In fact, according to estimates by Sandia National Laboratories, during chili season in New Mexico, about 7,800 metric tons of carbon dioxide are emitted when roasting, which is equivalent to driving 1,700 cars for a year.

So, taking advantage of his position as a clean energy researcher and his cultural history, Armijo found a much more sustainable way to roast the chiles: using solar energy. 

It is not, however, the solar energy that we usually imagine, solar panels. Instead, it used another type of energy, known as concentrating solar thermal, or CSO, which uses the full range of sunlight to generate heat and power. "This technology uses heliostats, a kind of pedestal with mirrors that can be rotated in different directions to concentrate sunlight on a single receiver, which in this case were towers 200 feet high (about 60 meters)" in the laboratory, says Armijo. 

In addition, as the Solar Feeds portal explains, because CSP systems are able to store energy by using a technology called "thermal energy storage," they can be used when there is no light or sun, which helps overcome the problems of irregularity that many other renewables have. 

What Armijo did, then, was to put a chili roaster his dad lent him on top of the tower and point the light from more than 30 heliostats at it. The result was not only 22 pounds of perfectly roasted green chile at a temperature above 900 degrees Fahrenheit, but with a flavor the team liked best. "We polled a number of volunteers to taste the chile roasted with sun and with propane, and most preferred the former," he adds. 

When asked how long chili lovers will have to wait to be able to have a device that allows them to roast this food with solar energy in their homes, Armijo is quite positive. "It would be possible in the next year or two," he says. He even says that next year he plans to take one of these systems to the New Mexico Chili Festival so that more people can learn how to roast chili "in the sun". 

In addition, the scientist and his team are also exploring how to create smaller systems and devices that people can use to roast coffee beans, for beer or soybeans. "With fuel prices going up and down, solar energy will be cheaper and that will help more people adopt these types of technologies," he says. This is how Armijo plans to make traditional New Mexico cooking part of the fight against climate change as well.

Note: This story was developed in collaboration with Yale Climate Connections and is based on the original capsule: Engineers use the sun to roast New Mexico's famous green chiles.