Ben Franske / Wikimedia Commons
A startup company is beginning to market geothermal systems that circulate heat from shallow aquifers.
A heat exchange technology developed at the University of Minnesota could help shrink the cost and footprint of geothermal heating and cooling systems.
Unlike conventional geothermal, which circulates ground heat found far below the surface, the approach taps into aquifers using fewer, shallower wells.
A startup company, Darcy Solutions, has begun pitching the product to commercial and industrial businesses in the Twin Cities.
Geothermal only heats and cools a small fraction of buildings in Minnesota and across the country. Customers tend to be schools, governments, senior communities, or other long-term property owners capable of making a substantial investment with a payback period that could take a decade or more. Yet the systems’ low carbon output and efficiency compared to other heating and cooling options remain for some organizations a compelling reason to install systems.
Typically, ground-source geothermal systems require sometimes dozens of boreholes as deep as 250 feet or more to tap the temperature of the ground. Darcy’s approach uses a handful of simple wells connected to aquifers located 30 to 150 feet deep.
Jimmy Randolph, the company’s chief technology officer, co-invented the Darcy approach after working in the geothermal industry for years. The former University of Minnesota research associate served as CTO of another startup, TerraCOH, Inc., which developed a system that stored carbon underground for later use for power production.
“One of our goals was to be cheaper than traditional geothermal, and we’re expecting to be cheaper,” Randolph said. “A traditional geothermal tends to have a payback of 10 to 15 years compared to natural gas and air conditioner systems. Because we have lower upfront capital costs, higher operating efficiencies, our calculations are putting that payback in the 5-year range.”
The geothermal principles Darcy employs are roughly the same as other geothermal installations, but the technology differs, said Brian Larson, CEO and co-founder. Larson looks for surficial aquifers less than 150 feet deep to save on drilling and to avoid interfering with deeper aquifers that supply drinking water for many cities.
Minnesota and much of the Midwest and sections of the East Coast have areas with high water tables, a legacy of glaciers that make them good prospects. “But we think this can work in two-thirds of the country,” Larson said.
Darcy differs in other ways. The contractor installs a closed-loop U-line filled with water that circulates through heat exchangers submerged in groundwater. The line then runs to heat pumps that feed into building heating and cooling distribution systems.
Larson assumes early adopters will be the same kind of buyers as those of geothermal systems in general. But he sees opportunity for retrofits in urban neighborhoods without the amount of land required for ground-based geothermal systems.
“What we’re trying to do is drive the adoption of environmentally friendly technology for the built environment,” he said. “It’s lowering your utility bill while reducing your carbon footprint.”
Geothermal could play an intrinsic role in beneficial electrification. Even in a frigid climate like Minnesota, a geothermal system keeps most buildings warm through the coldest days of the year. Standard electric heating still struggles in such conditions and most businesses and homes have a natural gas backup system available to deal with subzero weather.
Gary Connett, chair of the Beneficial Electrification League and former Great River Energy executive, said geothermal removes the need for separate natural gas and electric systems in homes and businesses and eliminates some costs associated with geothermal. He sees Darcy’s approach as a potential “breakthrough” technology because of reductions in operational and lifecycle costs.
“If America and the world are going to meet climate change goals, we must electrify space conditioning and water heating using heat pump technology,” Connett said.
Using aquifers offers an advantage over natural gas and traditional ground-source geothermal systems that use the temperature of the earth for heating and cooling. Darcy’s technology runs on electricity, a cleaner energy source in Minnesota than natural gas. Darcy’s system cuts energy consumption and carbon emissions by 60% to 80% when compared to natural gas on both the heating and cooling side.
“On the cooling side, it might even be more than that,” Randolph said. “We’ve had an independent analysis on the cooling side and it comes in as 77% more efficient than a traditional rooftop air conditioning unit.”
A handful of clients have signed up for the system, among them a St. Paul union hall, a north Minneapolis jobs training center, and a North Dakota business. The technology has also earned recognition with awards and funding from the Minnesota Cup startup competition, the Clean Energy Trust, and the National Science Foundation.
Among the company’s believers is Jamez Staples, who plans to install a Darcy system as part of a retrofit for a clean energy job training center in North Minneapolis. A geothermal system will introduce people to a heating and cooling system offering an environmentally friendly alternative to natural gas.
“This is one of the demonstration projects we’ll have as part of the training center and we’re excited about working with Darcy,” Staples said.
One of Darcy’s partners is David Henrich, owner of the geothermal and water systems company Bergerson Caswell and a veteran of the geothermal industry. He uses a Darcy system on a warehouse near an office served by a geothermal system.
Bergerson Caswell once installed $2 million to $3 million worth of geothermal systems annually, mostly in homes. When federal tax credits and research investment went away, so did clients. Today, the company does around $500,000 worth of projects a year.
The Darcy system comes at a time when geothermal energy has lost a bit of its luster after having seen a splurge during the Obama administration. The American Recovery and Investment Act invested $362 million in geothermal research and offered tax breaks for residential and commercial installations. The industry ground to a halt under the Trump administration as geothermal companies, especially on the residential side, have struggled to find customers as tax breaks expired in 2017 before being restored.
Henrich blames the industry’s woes on a lack of cohesive federal energy policy, utilities who do not see the potential of geothermal, and regulators who do not understand it. The federal government offers commercial geothermal systems a 10% tax credit, which does not represent much of an incentive.
“Without the Darcy technology I would have completely divested out of geothermal,” he said. “It’s sad. We used to run ten rigs doing geothermal work, from universities to homes. We have one rig dedicated now and it’s parked next to a fence. It’s heartbreaking because we know it is a viable technology.”