IN² Spotlight: Flowing Geothermal Tech Toward Residential Buildings


March 14, 2023—When multifamily structures and commercial building owners are considering energy efficiency measures, geothermal heating and cooling is often discarded because it requires too large of a footprint outside the building for the ground loop. Darcy Solutions looks to change that.

“We make geothermal heating and cooling practical for commercial and multi-family residential buildings—markets largely unserved today because of footprint constraints,” Darcy Solutions Co-founder and CEO Brian Larson said.

Darcy Solutions does this by using the superior heat-exchange capacity of water instead of the conduction-based exchange of rock and dirt. This dramatically reduces the number of holes necessary to put in the ground, potentially lowering the footprint requirement by more than 95%.

Typically, a traditional geothermal system uses fluid that circulates through loops in the ground where it either rejects or absorbs heat, then it returns to the building’s HVAC system, moderating the temperature in which the equipment operates and increasing its efficiency. Darcy Solutions puts a heat exchanger into a well, submerging the heat exchanger in groundwater. The closed loop fluid still circulates to and from the building, but because the system uses groundwater as a heat source or sink, instead of the surrounding soil, it can exchange up to 50 times the amount of energy as a traditional ground loop system. This lets Darcy Solutions provide geothermal heating and cooling to their customers with a significantly reduced footprint and a 20% cost savings. Just one well may provide enough heating and cooling capacity for ten homes.

“Even if it wasn’t cost driven, many of these buildings just don’t have the space to drill what’s required for traditional geothermal,” Larson said. “Geothermal is the most environmentally friendly technology because there’s no fossil fuels used on site, and economically, it’s the most efficient technology by 50 to 80% in some cases.”

This is because instead of burning coal, fuel oil, propane, or natural gas to heat a building, Darcy Solutions simply moves the heat from the earth to the building. Geothermal technology, which essentially involves moving heat around through pumping water, is much less energy intensive than the alternatives. Participation in the IN2 program only improved Darcy Solutions’ potential.

“The researchers at NREL corroborated our model for our heat exchanger,” Darcy Solutions VP of Technology Ryan Martin-Wagar said, “And they helped us optimize how our heat exchangers work with a building. How do you connect our system with building systems? Those are the elements that they’ve really helped us with.”

Darcy Solutions has three installations up and running in Minneapolis and St. Paul, Minnesota, and two of the three are retrofits rather than starting with a new building. They include an office building, a multifamily residential building serving low and middle income (LMI) tenants, and a training facility with some office space and warehouse space. For retrofits, some clients prefer to keep the boiler as a backup, in which case Darcy Solutions uses a hybrid design, while others remove the boiler all together and rely solely on the geothermal unit because they want to reach net zero energy goals.

“We’ve learned the importance of energy modeling and the challenges the industry has,” Larson said. “Our work with NREL highlighted what’s possible and set the bar from an energy modeling standpoint. It also provided us with another level of credibility and showcased the market opportunity.”

A key part of what Darcy Solutions is trying to do is wrapped up in social equity and affordable housing. An equitable transition for electrification is necessary so it’s not just the more affluent communities that move away from natural gas.

“We think geothermal is a key part of enabling the transition for low- and moderate-income housing,” Larson said. “At the end of it all, they should be seeing lower cost utility bills and a healthier environment. If you’re not burning fossil fuels on site, you’ve just made the ambient environment that much healthier.”

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