On rare occasion I run across a system that, although smaller in size, supports a mission critical facility and supporting spaces with geothermal. In one instance, open loop geothermal-sourced cooling was serving a smaller network operations center that had a large screen wall with a small data center behind it. The building had two central water-cooled chillers that used geothermal wells ever since it was constructed in the 1970s. They supported more than a few air handlers of different sizes and capacities that had been strung along much longer than their anticipated life. As the densities of people, screens and equipment ramped up recently, those air handlers struggled to meet the maximum loads – and I didn’t want to even ask about ventilation.
The geothermal exchange was done with wells, which include supply wells and injection wells (to return the water) and they were in good condition as confirmed by a hydrogeologist. It occurred to me how much was saved through the years using this system that was still functional; the savings of cooling tower maintenance and (at least two) replacements over the years, not to mention extending the life of the chillers. Overall what was needed is the update to the chillers and the rest of the mechanical systems, not to replace this efficient cooling method with cooling towers or air-cooled chillers.
We concluded that the old chillers and pumps would be retired, replaced with a more modern system with added capacity. The existing pipes were determined to be sufficient for the additional water flow that the new demand load would require, and pumps were selected to match. Although the previous chillers had the geothermal well water running through them a plate-and-frame heat exchanger was added to isolate the condenser water loop and add a layer of dependability and versatility.
By keeping the geothermal cooling source, we saved the client a lot of capital and operational expenses in the decades to come. Considering how the previous system performed with a good maintenance program its likely that it will operate another four decades before needing an update. This is because there won’t be any cooling towers or outdoor condensers that will be punished by the weather or constant supply of chemicals. And because the water is about 70 degrees F year-round, this allows the compressors to operate more efficiently all year as well.
Open loop geothermal cooling systems have been operating for far longer and continue to be designed, installed and operated throughout the U.S. and beyond. Although they may not be a match for massive campus needs, they can certainly support a megawatt for the edge data center, small mixed-use data centers, and network operations buildings with multiple needs.