How does Geothermal (Ground Source) Heating Work?

Geothermal heating and cooling systems, also known as ground source heat pumps, operate very differently than traditional furnaces or boilers. Instead of burning fossil fuels like oil, propane, or natural gas, geothermal taps into the consistent temperature under your lawn to heat your home. In the summertime, it uses that same underground temperature to provide super efficient central air conditioning, without the noisy condenser sitting outside. Because it works using renewable energy found underground, it doesn’t produce any on-site carbon emissions and operates at anywhere from 300-600% efficiency, prompting both the Department of Energy and the EPA to declare geothermal to be “among the most energy efficient and environmentally friendly heating, cooling, and water heating systems available.” 

That said, if you ever took a class trip to a cave system, or if you’ve ever been in an unfinished basement, or perhaps a wine cellar, you know that the temperature underground is pretty cool, around 55 degrees in fact. So how, exactly, does a geothermal heating system use that consistent 55 degree temperature to keep your family warm with unmatched efficiency? In this post, we’ll drill down into the science behind geothermal heating systems, or ground source heat pumps to get to the bottom of that question.

Components of a Geothermal Heating System

There are three components to just about every heating system: the fuel, the furnace or boiler, and the delivery system. For instance, if your home relies on oil to keep warm, you’ll recognize the fuel as oil that usually lives in some rusty tanks in your basement, that fuel goes into the furnace where it’s burned to generate heat through combustion, that heat will then be distributed throughout your house through either radiators or an HVAC system. 
Geothermal also has three roughly analogous components, but the first two are what make geothermal so different from traditional heating systems: ground loops, an underground system that taps into the thermal energy under your lawn; and a heat pump powered by electricity, that moves liquid through those pipes to harness that energy and efficiently convert it to a higher temperature. Finally, an HVAC system distributes that heat to keep your family warm. Geothermal heating systems can also be referred to as ground source heat pumps or GSHPs precisely because it sources underground heat using ground loops in order to power a heat pump.

Ground Loops

Thermal, or heat, energy is measured in BTUs. Any heat pump system works by gathering BTUs from one place and transferring them to another. Ground loops are what put the “ground source” in “ground source heat pump.” There are a few different types of ground loop systems, but they all serve the same basic function: harness renewable BTUs, or thermal energy from the earth by circulating a thermally conductive liquid underground to go into a heat pump.

A Dandelion geothermal system uses vertical ground loops, where pipes are installed anywhere from 200-500 straight down into the earth. Vertical ground loops are installed using well-boring equipment and trenched back into the house to connect to a heat pump. Those pipes are made of a highly conductive, and super durable high-density polyethylene material and circulate a mixture of water and propylene glycol, a food-grade antifreeze, that absorb the ground’s temperature.

It’s important to note that ground loops don’t generate heat underground. The function of a ground loop system is to absorb heat energy (BTUs) from the earth so that it can be transferred to a heat pump and efficiently converted into warmth for your home. While that means you can’t use ground loops to heat your driveway, it also means that once buried, your geothermal system won’t mess with your lawn and garden. In fact, Dandelion’s ground loops systems are built to last for over fifty years and should require no maintenance.

The number of BTUs necessary to heat your home will vary based on a few diffener factors: house size, insulation, and the conditions of the soil on your property. Accordingly, it’s important that the size and number of ground loops installed are up to your home’s needs. Many homes require more than one ground loop, with vertical loops that means boring more wells at least twenty feet apart to absorb enough BTUs to power your heat pump. Dandelion uses proprietary software technology to accurately design a ground loop system that will fit your home and keep your family warm.

Heat Pumps

Now that we know how geothermal heating pulls heat energy from the earth, we’re still left with the question how we can heat our homes with it. After all, 55 degrees might sound better than the temperature outside on a January evening, it’s few people’s idea of cozy conditions. That’s where the heat pump comes in.

Simply put, heat pumps are devices powered by electricity that gather heat energy from one place and transfer it to another. Even if you’ve even never heard of a heat pump before, you probably utilize the technology everyday: refrigerators work by transferring heat from inside of your fridge to the outside. In terms of heating your home, there are air source heat pumps (ASHPs) and ground source heat pumps (GSHPs).

A ground source heat pump mechanically circulates that thermally conductive liquid solution through the ground loops. After absorbing the ground’s thermal energy, that solution then goes back into the heat pump and exchanges its heat energy with liquid refrigerant inside the heat pump. That refrigerant is then turned into a vapor and compressed. The act of compressing that vapor increases its temperature. Once that vapor is hot enough, it enters a heat exchanger which transfers that heat to the air. That warm air is then circulated using your home’s standard HVAC ductwork.

True to its name, an air source heat pump, or ASHP, gathers BTUs from the air outside and transfers them into your home through either HVAC ductwork or mini-splits. Just like ground source heat pumps, ASHPs are an efficient, carbon neutral way to heat your home while providing air conditioning at no extra cost. 

The difference between ASHPs and geothermal, or ground source heat pumps, lies in the consistency of the source of that thermal energy. The colder the temperature outside, the harder source heat pumps have to work hardest to harness BTUs to heat your home. That means that as the temperature goes down outside, so too does the efficiency of your ASHP, and after a certain point there aren’t enough BTUs in the air to transfer into your home and you’ll have to resort to heating with a back-up system. Unlike the air outside, the ground is a consistent temperature no matter how hot or cold the weather outside, ground source heat pumps always operate at 300-600% efficiency on even the most frigid winter nights. 

A geothermal heating system is the most efficient and environmentally friendly way to heat your home. Additionally, geothermal systems also provide hyper-efficient central air conditioning, so in addition to saving money and reducing your carbon footprint, ground source heat pumps let your family live more comfortably year-round. What are you waiting for? Find out if your home qualifies for Dandelion geothermal today.

Make the switch to Geothermal for as little as $0 down and $150/month.

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