What’s up with networked geothermal?  

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At Fresh Energy, we’re fond of saying that heat pumps are having a “moment.” And it’s true! Our heat pump explainer blog post is one of the most visited on our website and media stories about heat pumps are being published almost weekly. Electric heat pumps are super-efficient heating and cooling appliances that stand to replace gas-burning furnaces and air conditioners in homes and businesses. On their own, heat pumps can offer improvements over existing heating/cooling appliances in the right conditions. But what if I told you that there is a way to utilize heat pumps that can achieve up to 600 percent efficiencies?

Enter: Networked geothermal

The term “networked geothermal” describes both the technology—geothermal—and the mode of delivery—a network. For our purposes, geothermal means delivering heat (“thermal”) from the ground (“geo”) to heat a building using a heat pump. This type of heat pump is called a ground-source heat pump.

As a quick refresher, at the most basic level, heat pumps simply transfer heat between two places via liquid in a looped pipe system. For the type of heat pump we’re talking about today, heat is transferred between a building and the ground via the loop. In heating mode, a ground-source heat pump pulls heat from the ground and transfers it indoors. In cooling mode, a ground-source heat pump pulls heat from inside and transfers it outside and into the ground. Ground-source heat pumps are really efficient because the ground remains a relatively constant temperature throughout the year, about 55 degrees, at the depth most systems are installed. This temperature just happens to be optimal for maximizing the efficiency of heat pumps.

Try this at home: the wall facing the back of my refrigerator was about 10 degrees warmer than the wall near the front of my refrigerator.

If this concept still seems incomprehensible, have no fear—just take a break from this blog post and walk to your refrigerator and grab a refreshing beverage or a snack. But before you walk back, take a moment to really think about your fridge. Ever notice the warm air coming out of the back of the fridge when it’s running? Your fridge is approximating a heat pump operating in cooling mode: it’s pulling heat energy from inside and transferring it outside, thereby cooling your tasty beverage and blowing warm air out the back. Think of a building as a giant refrigerator. A heat pump operating in cooling mode pulls out heat from indoors and transfers it outside. Boom—you understand heat pumps!

Ok, so we now understand the geothermal aspect of networked geothermal, but what about the network aspect? Networked geothermal, also called geogrids, describes the connection of a number of ground-source heat pumps to one another to form a shared loop network. In English, this means connecting nearby homes and businesses together to form a system or network of heat pumps. A networked geothermal system can achieve upwards of 500 to 600 percent efficiencies, which means that for every unit of energy that goes in, five or six units come out! Is this magic? No! Recall that heat pumps simply move heat from one place to another. Ground-source heat pumps move heat from the ground to a building, and vice versa (in cooling mode). A network of ground-source heat pumps can move heat from the ground to a building and between a building and another building. Sharing (heat) is caring!

In a geothermal network—as in life—having diversity in your network is a good thing. Studies have shown that having a diverse group of buildings with different heating and cooling needs can help balance out the system. For example, if you’ve ever looked at the roof of a hospital or grocery store, you will probably see large fans that work to remove the heat generated by cooling (think back to our refrigerator example). This type of heat is called “waste heat” and it has, as its name suggests, been seen as an undesirable byproduct. But for networked geothermal systems, one person’s trash is another person’s treasure: that waste heat can be captured and put back into the system and delivered to buildings that need it.

At this point in the blog, if I’ve done my job, you should be on the path to becoming an expert about a few things. First, you should have a better understanding of what a ground-source heat pump is and how it can transfer heat in the ground to buildings and vice versa (get up and make another visit to your fridge to really lock down your heat pump knowledge!). You should also have this loose concept that a diverse network of ground-source heat pumps can unlock even greater potential out of an already impressive technology. If networked geothermal systems are so good, you might well ask, then why aren’t we using them everywhere?

Fossil gas pipes connect to 2/3 of homes in Minnesota.

The answer to this question is multifaceted and complex, but to start, if you have ever walked down the street in a neighborhood that is currently served by fossil gas (about 2/3 of homes in Minnesota), you would be standing directly over the problem. Beneath your feet lies a vast network of pipes that deliver fossil gas directly to each house and to each building. For decades and decades, delivery of this gas has been a relatively uncontroversial proposition and the legal monopoly power that gas utilities enjoy in Minnesota means that they are often the only provider of these services to heat your homes, your water, and your food. But as we begin to learn more about the climate impacts of the fossil gas system, the health impacts of burning gas indoors, and the causes of increasing energy bills, important discussions about alternatives such as electrification and networked geothermal have begun to take place.

1. Efficiency

First, this was mentioned above, but it bears repeating: networked geothermal systems are super efficient. Almost magically so (Editor: it’s not magic, it’s just engineering and science at work). Using less energy to heat and cool our buildings is a no regrets approach.

2. Cost

Second, networked geothermal systems can be cost-effective. Today, your gas bill has two components: the distribution rate and the cost of the gas. Over time, as a result of utility rate cases driven by investments in the existing gas system, distribution rates has increased year-over-year. More recently, the cost of gas has increased and the gas market has shown volatility. Both of these factors hit consumers’ pocketbooks all the same. Networked geothermal systems take the cost of gas out of the equation as they rely only on electricity to operate the heat pumps, but pull energy out of the ground.

3. Air Quality

Third, removing appliances that combust fossil gas inside of homes will increase health outcomes. Let’s face it, indoor air quality has long been a neglected topic of consideration, but studies have shown the detrimental health impacts of burning gas inside our homes. Transitioning away from burning gas in our buildings will help improve health outcomes everywhere, but especially in traditionally under-resourced communities that bear the brunt of air pollution impacts from a variety of sources (MDH/MPCA report on air pollution impacts).

4. Jobs

Fourth, networked geothermal systems can provide jobs for skilled labor, possibly the same folks who installed that vast network of gas pipes that crisscross our neighborhoods. At its core, networked geothermal systems and gas distribution systems are not so different. Both require infrastructure to be installed in the ground and that requires a legion of skilled, local workers who know the ins and outs of installing pipes and operating networks.

5. The energy transition

Fifth, networked geothermal can serve as way for traditional gas utilities to begin the transition away from gas delivery companies and toward thermal/heat companies. This one is important. If we can find a solution that supports labor, allows utilities to transition their business model, and combat climate change, we should focus on finding ways to implement this solution equitably and rapidly. Gas utilities across the country have begun to install networked geothermal systems.

Gas utilities have long been the only game in town when it comes to heating for many. But there are growing calls for change from the status quo. Networked geothermal systems are an intriguing alternative that address efficiency, cost, health, labor, and utility needs.

At this point, feel free to head back to the refrigerator and grab your favorite cold beverage because congratulations: you are now an expert on networked geothermal! You can now thrill friends and family with your expertise on this exciting, innovative resource. Thinking about solutions to address climate change can be daunting, but we’re here to tell you that they do exist. Be sure to follow Fresh Energy as we continue to highlight these solutions and begin to advocate for adoption of policies to promote these promising solutions at the Minnesota Public Utilities Commission.

Want to learn more about how we got here? Get the scoop on the Natural Gas Innovation Act (NGIA) which passed the Minnesota Legislature in 2021 and opened new paths for understanding the future of gas in our state. Fresh Energy’s work on gas decarbonization is crucial to reducing carbon emissions and increasing health outcomes in Minnesota, learn more about our Gas Decarbonization program here.