Water Well Journal Q&A

Published On: June 20, 2022By Categories: Features, Geothermal Technology


The Twin Cities, Minnesota-based company is pioneering geothermal heating and cooling in a more cost-effective, practical, energy-efficient, and environmentally friendly way.  

By Mike Price

Bergerson-Caswell Inc. sets 8-inch casing for the first Darcy heat exchange well to 195 feet in September 2020 with the Pipefitters & Steamfitters Union Hall in St. Paul, Minnesota. The casing was sealed in place using the braden-head grouting method. The Darcy heat exchanger produced 150 gallons per minute. Photo courtesy David Henrich, CWD/PI, CVCLD, president of Bergerson-Caswell in Maple Plain, Minnesota.

Darcy Solutions Inc. is developing a new way to complete geothermal heating and cooling projects that could create even more demand for today’s water well contractors.

Based in Excelsior, Minnesota, Darcy Solutions alleviates two common hurdles that often sidetrack geothermal heating and cooling from being pursued: the upfront expense and amount of space the system requires.

The company’s technology magnifies what each borehole can do, with capacities of up to 40 to 80-plus tons per borehole, whereas the industry average is about one to two tons of heating and cooling capacity per borehole. Its closed-loop system uses a heat exchanger to transfer heat with groundwater rather than sediment and rock but without using any of that groundwater or risking its contamination in the process.

Therefore, the system requires fewer holes drilled to meet heating or cooling demand, reducing the surface-level space required by as much as 95%. A smaller footprint allows existing buildings—not just new construction—to take advantage of the benefits of geothermal systems without extensive remodeling or disruption.

“That’s the biggest benefit that our approach provides: we get a much higher level of energy exchange per hole in the ground,” says Brian Larson, co-founder and CEO of Darcy Solutions. “We end up seeing savings up front, and when it operates, we see additional savings in operating costs. As a result, our paybacks are under 10 years.

“In addition to colleges and universities as the nonresidential applications, it opens up all kinds of opportunities. That’s what we’re really excited about, and what we’re seeing is just the conversation of geothermal—whether it’s using this technology or technology agnostic—is getting that much more visibility and so it’s lifting all boats with that tide. We really expect the whole [geothermal] pie to be getting bigger.”

Though every building is different, Larson estimates that using the system to replace conventional heating and cooling cuts annual costs by 30% to 80%, with a greater portion of the savings currently coming from cooling than heating because of the relatively low price of natural gas. In addition, it offers an all-electric option that can help building owners meet carbon reduction goals and provide a viable and financially attractive heating solution when natural gas is no longer an available option.

The startup company, founded in 2018 with support from the University of Minnesota Technology Commercialization, has been presenting its technology to various geothermal and energy organizations since 2019. It has also been working with Minnesota’s legislature to have the closed-loop heat system definition added to the state’s well code.

Brian Larson, co-founder and CEO of Darcy Solutions Inc.

While Darcy Solutions is working with a third-party energy modeling firm to measure and validate the performance of its first systems, the company reports that its initial system is performing better than anticipated.

“We’re really excited about what we thought was going to take three wells we’ve been able to do it with a single well,” Larson shares.

National Ground Water Association Past President David Henrich, CWD/PI, CVCLD, president of Bergerson-Caswell Inc. in Maple Plain, Minnesota, began working with Darcy Solutions in 2018. His company drilled the initial Darcy well in early 2020, taking it from concept to the field. In September 2020, his company drilled the wells for Darcy’s first commercial project with the Pipefitters & Steamfitters Union Hall in St. Paul, Minnesota.

“It’s worth highlighting that these wells are all installed inside of code wells,” says Henrich, whose company and others in the water well industry have partnered with Darcy Solutions. “Properly constructed. Properly grouted. It’s a continuous casing into one [aquifer] formation.

“We’re talking about some of the more robust well construction practices that we employ in the industry. Other added layers of protection are we’re only using potable water as a circulating solution, so when you talk about loop leak potential, we’re even down to the level of mitigating by having literally an inert solution in the systems.

“The Darcy group’s approach is to use the resource responsibly and protect groundwater so we can keep on rolling this technology out in other areas.”

Honoring the pioneering groundwater modeling work of French hydrologist Henry D’Arcy, the company chose its name that inspired its mission to solve the challenges of sustainable heating and cooling. The company is currently in various stages of projects in multiple states.

Since July’s issue of Water Well Journal focuses on green technology, we caught up with Larson to learn more about Darcy Solutions.

Darcy Solutions’ system scope and controls overview. Image courtesy Darcy Solutions.

Water Well Journal: How is Darcy’s technology different from traditional geothermal/ground-source heat pumps?
Brian Larson: Traditional geothermal/ground-source heat pump systems rely on conduction-based heat exchange. They do this by pumping a heat exchange fluid [typically water mixed with anti-freeze such as glycol] through a closed-loop system consisting of several U-shaped plastic pipes. These pipes are placed in boreholes at typically 200 to 250 feet deep that enable heat exchange with the surrounding earth. Because plastic piping and the cement grout surrounding it doesn’t exchange heat quickly, a large amount of piping is needed to provide the heating and cooling capacity necessary for a building. Over the course of a heating or cooling season, the earth surrounding the piping will gradually cool down or heat up, decreasing system efficiency.

A Darcy system connects to aquifers located 150 to 400 feet deep and takes advantage of convection-based heat exchange, providing a much faster and higher capacity approach. Darcy also uses a closed-loop system and a heat exchange fluid. Our system pumps water through plastic piping and does not use anti-freeze. A heat exchanger replaces the U-shaped bend in a traditional system. This heat exchanger is positioned in an aquifer to take advantage of the superior heat exchange benefits of flowing groundwater to heat or cool the closed-loop fluid of water.

As a result, a single Darcy borehole can deliver 20 to 50 times the heat exchange capacity of a traditional geothermal borehole, depending on the site’s groundwater flow. Darcy’s system sustains a relatively constant temperature throughout the year and maintains its efficiency throughout a heating or cooling season. This is because the massive quantity of flowing groundwater has high heat capacity to dissipate the heat.

WWJ: How is groundwater impacted by a Darcy system?
Larson: Darcy’s closed-loop system’s only interaction with groundwater is the transfer of heat. The massive volume of water and surrounding earth readily and quickly dissipates/restores the impact of the exchanged energy. The water that circulates through the closed loop does not come into direct contact with the groundwater. These designs do not consume groundwater, remove it from the subsurface, move it between aquifers, or introduce contaminants.

Roughly two-thirds of the U.S. population live in an area with suitable groundwater availability and surface proximity for Darcy’s technology. The glaciated regions of the country running from the Upper Midwest to New England are particularly well-suited for this technology.

Additionally, there are many other areas in the United States, including the Pacific Northwest and southeast United States with suitable groundwater resources.

WWJ: With new technology that hasn’t been around long to be tested over time, how can someone be confident this technology will perform well over the life of the system?
Larson: Darcy’s technology was developed at the University of Minnesota by a team of expert hydrogeologists. One of these hydrogeologists is our co-founder, Jimmy Randolph, Ph.D. Darcy supplements its hydrogeologic expertise with the help of our industry partners.

Darcy complements this expertise with a monitoring system that helps ensure each borehole is performing as intended. Monitoring information is also available to the building operators and the HVAC contractor to provide early identification of maintenance needs. In addition, because the heat exchanger installed in each wellbore is readily accessible and removable, we can quickly remedy underperforming boreholes or heat exchangers.

WWJ: How much space is needed to install a Darcy Solutions system?
Larson: While traditional geothermal systems typically deliver one to two tons per borehole on average, each Darcy borehole can deliver up to 40 to 80 tons per borehole.

As an example, a building that needs 200 tons of heating/cooling capacity may require 150 to 200 boreholes spaced every 15 to 20 feet on a grid. Using a Darcy system would likely require four to six boreholes spaced every 50 feet in a line. This line of boreholes could run along one length of the building or parking lot. This reduction in footprint requirements enables the Darcy system to readily fit in constrained outside spaces, making it appropriate for new builds and retrofits alike, even in the densest urban environments.

WWJ: What will the installed system look like on the outside of the building?
Larson: Each Darcy borehole will have a wellhead that extends approximately 18 inches out of the ground. These headers can easily be incorporated into the landscaping. They offer the benefit of ready access to the well for maintenance.

Another aspect is what you don’t see—the outside appearance of a building and rooftop. By using a Darcy system, unsightly cooling towers and other rooftop units can be eliminated. The elimination of these components provides the additional benefit of making rooftop space readily available for solar installations while also eliminating the maintenance requirements caused by equipment exposure to the elements.

WWJ: How has the technology been received thus far when presented to organizations or the Minnesota legislature?
Larson: As we’re going through this, it’s a different application. It’s a different approach than what current regulatory codes contemplated so the framework needs to be updated. That means that some people are excited about it and others are cautious. We understand people want to be assured it’s safe and that we’re protecting the resource. We’re working to identify how to bring along the industry and relevant regulatory bodies so they understand the application too.

WWJ: You attended Groundwater Week 2021 for the first time and spoke with several exhibitors about your technology. What type of feedback did you receive?
Larson: We told them we’re trying to do this and the community of suppliers in this space are like, ‘Hey, we could do this; well, what if we tried this.’ It’s a group of problem solvers who embrace the challenges of innovation and every day they’re trying to figure out how can we use this seal differently or how can we use that tool.

To get a group to engage at that level of creativity is just so powerful, and what we’re hoping to do is now pull the regulatory community into that same creative thought process because when we collaborate and think collectively, we can come up with some really good answers.

I think the [water well] industry is so predisposed to doing that kind of problem solving. They embrace the idea and say, ‘Hey let’s figure this out,’ and so we’d like to do that with the regulatory community as well because they see the market need for it. It’s just a matter of how we get them comfortable with something different.

WWJ: What is Darcy’s minimum project size?
Larson: We’re currently focused on systems requiring 100 tons of heating/cooling capacity or more. A single Darcy borehole can typically deliver up to 40 to 80 tons. To be cost effective requires that a project utilizes this capacity. This means commercial and multi-unit residential buildings are well-suited to take full advantage of the economic benefits of a Darcy system. Single-family homes can also benefit when connected to a community/district system.

WWJ: How do you envision geothermal heating and cooling being a part of the United States’ efforts in reducing carbon?
Larson: The Department of Energy and EPA have both highlighted the leading role geothermal heating and cooling should play in reducing carbon emissions as one of the most energy-efficient and environmentally friendly technologies currently available. It’s a matter of finding ways to make this technology operationally practical and financially viable for as broad of a user base as possible. We’re excited to help enable this by making geothermal viable to market segments [commercial and multi-family residential] that have been historically underserved by geo.

WWJ: How has working with Henrich’s company been with it drilling and installing the first Darcy systems?
Larson: In a word, exciting! We have worked very closely with David and his team to take the system from our initial concept and prototypes to our current commercial offering. We’ve solved a number of challenges along the way, and we continue to find opportunities to improve and enhance system design and performance. It’s been a great partnership, and we’re very appreciative of the ongoing collaboration and support Bergerson is providing.

WWJ: Lastly, what can water well contractors expect to see from Darcy Solutions in the coming years?
Larson: Water well contractors bring deep expertise and experience from their markets. Our goal is to work with these contractors to install Darcy-designed systems [so] as to deploy the technology throughout the country. As we expand into new regions, we’re reaching out to local drillers to install our systems.

Mike Price is the senior editor of Water Well Journal. In addition to his WWJ responsibilities, Price contributes to the Association’s scientific publications. He can be reached at mprice@ngwa.org, or at (800) 551-7379, ext. 1541.

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