In a windowless solar energy lab in the Mechanical Engineering Building at the University of Minnesota, researchers are tapping the power of a new piece of high-tech equipment that can replicate the amount of sunlight equivalent to more than 3,000 suns.
The new concentrating solar simulator, the first of its kind in the nation, will be used by researchers in the university’s College of Science and Engineering in a variety of experiments, including converting concentrated sunlight, carbon dioxide and water into synthetic hydrocarbon fuels. The indoor lab will provide consistent experimental conditions independent of weather and time of day.
Based on concepts of similar simulators in Europe, University of Minnesota researchers designed the $450,000 piece of equipment to provide concentrated light equivalent to that possible from modern solar optical systems. The investment is already paying off. The lead researchers at the university have secured nearly $1 million in research money from a new National Science Foundation Emerging Frontiers in Research and Innovation grant in collaboration with CalTech and UCLA. The University of Minnesota’s Solar Energy Laboratory researchers also have received nearly $1.4 million in grants from the Initiative for Renewable Energy and the Environment within the university’s Institute on the Environment.
“This is an exciting time for solar research at the University of Minnesota,” said mechanical engineering professor Jane Davidson, one of the lead solar researchers. “This is the culmination of years of work and is the next step in our goal to develop thermochemical processes for producing fuels from sunlight. Combining solar thermal power and sustainable feedstocks like brackish water, CO2 and cellulosic biomass promises a transformational path for carbon-neutral production of hydrocarbon fuels plus long-term storage of solar energy, our most abundant energy resource.”
The new solar simulator includes seven mirrored lamps with 6,500-watt bulbs in each lamp. The bulbs are used by large movie theaters to illuminate an entire screen. Using special reflectors, the light from the seven lamps is concentrated into a single three-inch-diameter spot where specialized solar chemical reactors are tested. Temperatures in the reactor from the concentrated light can reach more than 3,600 degrees Fahrenheit (2,000 Celsius).
These high temperatures give researchers a unique opportunity to develop highly efficient ways to convert carbon dioxide and water to solar fuels. The transformational process reverses combustion by efficiently “reenergizing” carbon dioxide and water molecules back into hydrocarbon form using solar energy, much like natural photosynthesis except faster and more efficiently. Researchers say the fuel production process is sustainable because it uses recycled carbon dioxide and water. The only byproduct is oxygen, which is released to the environment during the splitting reactions and used again when the hydrocarbon fuels are burned.
Another process the researchers study uses high temperatures from sunlight to gasify biomass from plants to produce synthetic fuels.
If successful at a small scale in the lab, the processes could be scaled up and used in large-scale, outdoor solar concentrators across the globe.
“Some people ask us why we would be doing solar research in a cold, northern state like Minnesota,” said mechanical engineering assistant professor Wojciech Lipinski, the other lead researcher in the project. “I usually respond that you don’t need to design a car on the road, you design it in a lab. So why not develop solar technologies in cold climates where you have lots of experts and great equipment?”
The University of Minnesota has a long history of thermal science and solar energy expertise that dates back several decades. “Many of the world’s leading solar researchers have ties to the University of Minnesota,” Lipinski said.
Today, the solar fuels research team includes University of Minnesota faculty and students from mechanical engineering, chemistry and bioproducts and biosystems engineering.