Viktor MusilExploring the realm of geothermal technology and its applications within urban infrastructure, this text provides insights into the utilization of groundwater-based geothermal heat pump systems. Highlighting Rochester, Minnesota’s endeavor to enhance energy efficiency in its municipal buildings, it emphasizes the advantages of such systems over traditional air-source counterparts. From discussing the effectiveness of groundwater systems in maintaining year-round temperature to examining the economic considerations and scalability, the text presents a comprehensive analysis. Additionally, it sheds light on the technological advancements driving innovation in geothermal solutions, showcasing a potential shift towards district heating and cooling networks. This informative piece not only underscores the benefits of adopting sustainable energy solutions but also underscores the importance of understanding site-specific factors for optimal implementation.
Groundbreaking Geothermal Solutions: Maximizing Efficiency in Rochester’s City Infrastructure
A few steps from the front door of Rochester, Minnesota’s city hall, two previously drilled wells plunge hundreds of feet down into a great, great aquifer. More than supplementing Rochester’s municipal water supplies, these wells will use the groundwater to heat and cool the 85, 000- rectangular- foot government building.
According to Rochester Facilities and Property Manager Scot Ramsey, groundwater-based geothermal heat pump systems use electricity more effectively than air-source systems. Rochester’s groundwater, which maintains a year- round temperature in the small 50 degrees Fahrenheit, reduces the system’s heat exchange workload and achieves regular coefficients of performance, or COPs, between 4 and 5, Ramsey said. A heat pump’s COP is usually a ratio of energy needed for important heating or cooling, with higher COPs reflecting higher levels of efficiency.
In moderate weather, air-source heat pumps have comparable COPs, but they are less effective and, as a result, have higher operating costs. Newer, cold- dried air- source models, but, work even when temperatures are below zero degrees Fahrenheit, as they often are in Minnesota, Ramsey said.
” Air- source heat pump technology is getting stronger, but your COP is still going to be 2 or under when it’s really cold”, Ramsey noted.
Ground-Source vs. Groundwater-Based Geothermal Systems
Ground-source thermal systems, which tap hidden heat from dry bedrock rather than groundwater, are almost as energy-efficient as groundwater-based systems and run smoothly all year long. But, due to the lower efficiency of individual ground- source wells, ground- source systems require a larger number of boreholes, each spaced about 20 feet apart.
However, groundwater systems are more space efficient and have the ability to “unlock an overall market that wants to take advantage of geothermal” , David Henrich, president of Minnesota- based drilling firm Bergerson Caswell, told Facilities Dive. Bergerson Caswell works as a drilling contractor for Darcy Solutions, a volcanic company whose closed-loop technology supports the Rochester City Hall system. When Darcy representatives approached Henrich about working up a few years back,” I soon said,’ I’m in,’ because I knew the limitations of]ground- source ] geothermal”, Henrich said.
Using Darcy’s technology, the Steamfitters and Pipefitters Local 455 union today cools its 100,000 rectangular- foot training facility in St. Paul, Minnesota with only four groundwater wells, according to the St. Paul Union Advocate. The Union Advocate reported that 70 wells on the premises and the temporary closure of its on-site parking lot would have been required for a conventional ground-source volcanic system.
According to Robert Ed, director of marketing and strategy for Darcy Solutions, Minnesota has an exceptionally positive geology for groundwater-based geothermal heat pumps. But the technology can be cost- successful in approximately 75% of the U. S. landmass,” he noted.
Tailoring Geothermal Solutions: Site-Specific Considerations and Economic Evaluations
Conditions can vary from site to site, depending on factors like water table depth and bedrock composition, even in areas where underwater hydrology generally favors groundwater-based geothermal heat pump systems.
“The aquifer could be 80 feet underground or 400 feet beneath, depending on the local geology, “Ed said. The staff at Darcy’s assesses site conditions to determine the ideal well depth, which is crucial because the system’s heat exchanger and groundwater pump must be submerged in the aquifer, he continued.
The true task of drilling the wells and installing the underwater equipment calls for more sophisticated equipment and specialist skills than the majority of water-well drilling companies do not, according to Ed. He advises businesses looking into thermal systems to reevaluate their drilling contractors.
In order to determine the best system for them, customers also need to understand the economics of ground-source and groundwater-based volcanic heat pumps, according to Henrich.
Henrich said that traditional ground-source geothermal heat pumps are appropriate for both home and small business users who require less than 50 tons of thermo capacity and for larger users who have plenty of room for borefields, such as suburban high school and college campuses. Henrich noted that it may be the only “ground-coupled” option available to users of any size in areas where groundwater conditions can’t support water-based geothermal systems.
The decision frequently comes down to choosing between closed-loop and open-loop “pum-and-inject” “groundwater systems” on groundwater-rich sites that are too small for conventional ground-source volcanic systems. In finished- loop systems, such as Rochester’s, the water in the building’s climate control system is independent from the groundwater. Henrich claimed that open-loop systems circulate groundwater for strong heating and cooling, pumping it through the buildings before returning it to the aquifer.
Open- loop systems may be more cost- successful, Henrich said, depending on the local geology and the system’s expected heating and cooling loads. A well-known casino in Minnesota recently consulted with Bergeron Caswell to optimize its planned 5, 000-ton geothermal system. He ultimately settled on an open-loop option that cost 20 % to 30 % less upfront.
Groundwater-Based Geothermal: Leveraging Incentives for Enhanced Energy Efficiency
Thermal supporters from the groundwater community believe that as more municipalities and owners of corporate properties give energy efficiency and emissions reduction measures more weight.
” We’ve been telling people for a long time that if you’re going to electrify heating and cooling, you’re going to have to ground- couple,” Henrich said, adding”, There’s a danger that you can’t manage peak demand” with air- source heat pumps alone.
The Inflation Reduction Act, or IRA, grants tax-exempt entities like personal nonprofits and government agencies similar pay that is available through the IRS ‘ clear pay framework. IRA tax credits, combined with lower operating costs, can make up the difference in only a year or two, according to Ed, even though installing groundwater-based systems also cost more than the fossil-fuel heating and cooling systems they generally replace.
For St. Paul’s Ever-Green Energy, which intends to install a closed-loop groundwater volcanic system at a new mixed-use development in Minneapolis, IRA credits increase an now compelling opportunity to reduce building emissions and space conditioning costs.
Incentives through the Inflation Reduction Act ]made groundwater- based thermal ] yet more beautiful,” Michael Ahern, senior vice president for system development at Ever- Green Energy, told Facilities Dive. Since Possibly- Green’s system will be owned by a nonprofit”, we will be pursuing the immediate pay alternative, “he added.
Scaling Up with Groundwater-Based Geothermal: Towards Sustainable District Heating and Cooling
Perhaps more powerful is groundwater- based geothermal’s scalability. Both Ever-Green and the city of Rochester created their systems with the intention of later utilizing the facilities that would surround them.
Possibly- Green’s system, which will primarily serve five buildings, could be scaled to heat and great” other developments as they are constructed in the area,” Actually- Green said in a 2023 news release about the project. A second thermal phase, which will replace an aging district steam system, will connect Rochester’s library, political center, and open arts complex to a thermal energy network that provides around 1 million square feet of interior space.
By connecting multiple buildings with unique heating and cooling profiles, using an external water loop that ranges between 40 and 70 degrees Fahrenheit throughout the year, and recycling waste heat wherever possible, Ramsey explained. Rochester’s next phase could achieve COPs of 6 to 8.
Rochester’s thermal energy network could eventually morph into a district heating and cooling system that provides access to the Mayo Clinic and Destination Medical Center for the city’s core. The network may eventually move gas utilities toward a “heat as a service” model as buildings on the network switch from combustion appliances to heat pumps, Ramsey said.
