Tim Mies posing next to the 15kW solar array panels at the Energy Farm. Mies, along with his diligent team, maintains the many research operations at the Energy Farm. Credit: Anjali Yedavalli
Among the University of Illinois’ most impressive living laboratories is the Energy Farm, a 320-acre farm plot on the South Farms supporting sustainability research. The farm is a testbed for a broad range of renewable energy sources; researchers across many disciplines are studying how to scale up and improve the effectiveness of these renewables, hoping to revolutionize sustainable energy production. Two recent research installations – an underground geothermal “battery” and an agrivoltaic solar array – are providing energy for the farm.
The Energy Farm was founded in 2007 as part of the Energy Biosciences Institute. Tim Mies, Director of Energy Farm Operations, explained that the original focus of the farm was analyzing second-generation biofuel crops and perennial grasses as a fuel source, which eventually expanded to renewable energy research as a whole. This bioenergy research has continued under the CABBI grant, funded by the Department of Energy.
By layering complementary energy technologies on top of each other, the farm generates much of its own energy. It features underground geothermal installations, bioenergy crops growing on the surface, and solar arrays sitting above the ground.
The Energy Farm’s UTB was installed in April 2023. Credit: Julie Wurth
In late 2022, the Illinois Green Fund supported a geothermal research collaboration between the University of Illinois and the Oak Ridge National Lab, which led to the installation of an underground geothermal battery (UTB) at the Energy Farm. This novel geothermal system features a water reservoir buried 20 feet underground that is tied in a geothermal loop. The UTB has a large thermal capacity and uses the ground’s stable temperature to provide a heat source or heat sink that is hotter or colder than the ambient air. Using a heat pump, this geothermal system can heat or cool a building. The key innovation of the UTB is that it can store thermal energy for later use, allowing it to accommodate the fluctuating thermal demands of a building.
The exchange of energy within this system is controlled and automated, which makes the installation very efficient. Andrew Stumpf, geologist and principal investigator at the Prairie Research Institute, described what makes this system unique.
“With this advanced installation, we can store thermal energy during times of lower demand and recover it as demand increases again. Through this mechanism you optimize the system’s efficiency,” said Stumpf.
The geothermal system at the Energy Farm, which began operation in May 2024, had immediate effects. Mies said he felt cooling almost instantly.
The primary purpose of the UTB is to provide heating and cooling, but the researchers also use this installation to study whether this new type of geothermal system can become mainstream. Although the farm’s office space is regulated by the geothermal installation, the adjacent laboratory space is heated by a propane furnace and cooled by electric-powered . An auxiliary part of this research project is to compare the efficiency of both systems. The hope is that geothermal technology can contribute to long-term sustainability goals on the farm. While the upfront cost of installing a geothermal system is higher than other renewable energy systems, the reduction in energy use is significant, so the cost recovery is expected to be quick.
Meanwhile, the Energy Farm’s main greenhouse is heated by a biomass boiler, which uses dried miscanthus as the fuel source. Instead of burning propane, this boiler turns the prairie grasses grown and harvested at the farm for research into heating.
In addition to these green installations, the Energy Farm is also home to a new 15kW solar array. The energy it generates is used by the farm, and excess energy is sold to the grid.
This array, with panels recycled from a campus building, is part of the SCAPES Agrivoltaics project, supported by a grant from the USDA National Institute of Food and Agriculture. SCAPES (Sustainably Co-locating Agricultural and Photovoltaic Electricity Systems) examines the capability of agrivoltaics, a practice that integrates and co-locates typical agricultural practices with solar electricity generation. Carl Bernacchi, Professor of Crop Sciences and Plant Biology at the University of Illinois and a principal investigator on the SCAPES project, provided insight into the environmental and ecological impacts of agrivoltaics research.
Because of its inherent constraints, agrivoltaics is an ideal framework for understanding crop responses to the environment, Bernacchi said. For example, the panels affect how much light reaches the crops. They also compete for space and slightly alter the temperature and humidity in the surrounding environments, making this a unique integration of the agriculture and energy sectors.
Full view of 15kW solar array at the Energy Farm. Bernacchi lightheartedly refers to the project as “Hortivoltaics” due to the presence of smaller, high-value crops located below the panels. Credit: Anjali Yedavalli
The array at the Energy Farm is layered on top of a plot of high-value crops. “I call it ‘hortivoltaics’ because it’s focused on horticultural crops like tomatoes and kale,” Bernacchi said. “It adds a whole dynamic level of diversity to the type of systems that we can study.”
In addition to this existing solar installation, SCAPES is building an 88kW array at the Energy Farm for the 2025 field research . This new, larger array will help researchers study agrivoltaics at a more realistic scale, paving the way for the commercial adoption of this practice.
All of the projects and initiatives at the Energy Farm represent the modern-day cross-disciplinary nature of sustainability research. Engineers are working with economists, educators, and biologists to make the technology of tomorrow happen today.
The Energy Farm employs two full-time staff who support the research being undertaken by undergraduate and graduate students, as well as their collaborative researchers. Students have played a key role in the success of these projects.
Regarding the geothermal research at the Energy Farm, Stumpf said, “Having a DOE National Laboratory and students involved creates a learning environment capable of providing numerous opportunities for collaboration and learning. We want this to be a living laboratory for students and faculty to use and benefit from.”
To Mies, running the Energy Farm is a team effort. “Our job is to work with researchers to bring concepts to reality,” he said. “When they say, can we do this? What do we need to do this? What’s it going to take? That’s where we come in.”
Energy use and generation on the farm can be monitored in real time from the Energy Farm Solar Dashboard >>>
— Article by iSEE Communications Intern Anjali Yedavalli