5 Facts About Networked Geothermal
Networked geothermal technology is poised to become the most-efficient way to deliver and remove heat in homes and businesses.
At Fresh Energy, we’re fond of saying that heat pumps are having a “moment.” 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 under 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 efficiency?
Networked geothermal can produce up to six times more energy than it needs to function with, especially when it includes a diverse group of buildings, from residential to commercial.
Enter: Networked geothermal
The term “networked geothermal” describes the technology—geothermal—and the mode of delivery, a network. For our purposes, “geothermal” means using a heat pump to deliver heat (“thermal”) from the ground (“geo”) to warm a building. This type of device is called a ground-source heat pump.
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 highly efficient because the ground remains a relatively constant temperature throughout the year, about 55 degrees, at the depth most systems are installed. This temperature also just happens to be optimal for maximizing the efficiency of heat pumps.
If this concept still seems incomprehensible, have no fear—just take a break from this blog post and walk to your refrigerator to 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. Now, 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!
The traditional underground natural gas line, the longtime energy source for millions of homes nationwide, is giving way to environmentally friendly options such as electrification and networked geothermal. courtesy of Fresh Energy
Geothermal Network Know-How
Okay, 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 to form a system or network of heat pumps. A networked geothermal system can achieve upwards of 500 to 600 percent efficiency, which means that for every unit of energy that goes in, five or six units come out! Is this magic? No!
Ground-source heat pumps offer a mirror image-type operating principle when it comes to operation during winter vs. summer. courtesy of Fresh Energy
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 look 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 is, as its name suggests, considered an undesirable byproduct. But for networked geothermal systems, one person's trash is another person's treasure: All that waste heat can be captured and put back into the system, and delivered to the buildings that need it.
To illustrate how heat pumps “move” heat, consider how the wall behind your refrigerator is about 9-10 degrees warmer than the front of the unit. courtesy of Fresh Energy
Here, There, But Not Everywhere—Yet
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?
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, 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, delivery of this gas has been a relatively uncontroversial proposition. 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 given to learn more about the climate impacts of the fossil gas system, the health impacts of burning as indoors, and the causes of increasing energy bills, important discussions about alternatives such as electrification and networked geothermal have begun to take place.
An existing natural gas system can move heat from the ground to a building, but a network of ground-source heat pumps can move heat from the ground to a building, and between a building and another building. courtesy of Fresh Energy<
- Efficiency. This was mentioned earlier, but it bears repeating: networked geothermal systems are super efficient—almost magically so. (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.
- Cost. 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 have 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 and pull energy out of the ground.
- Air quality. 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.
- Jobs. 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.
- The energy transition. Networked geothermal can serve as a 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 models, and combats 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.
For many, gas utilities have long been the only game in town. 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
This article was reprinted with permission from Fresh Energy.