Decarbonization for non-engineers: geothermal system installation

Geothermal systems are often described as “using the earth as a battery,” but for anyone who has watched a geothermal installation happen at an existing building, the process can look more like a major archaeological dig. Large drilling rigs arrive on site, crews spend weeks boring deep holes into the ground, and sections of landscaping or pavement may temporarily disappear. If you’re not an engineer, it’s reasonable to wonder: what exactly is going on down there?

A geothermal, or “ground-source,” heat pump is a type of heat pump that transfers heat between a building and the ground. Like all heat pumps, it doesn’t create heat: it moves it from one place to another. In the winter, the system extracts heat from the earth and moves it into the building. In the summer, it does the reverse, removing heat from the building and transferring it into the ground.

The key advantage is that the temperature below the earth’s surface remains relatively constant throughout the year. While outdoor air temperatures can swing dramatically between seasons, the ground provides a more stable source of heat in winter and a more stable place to reject heat in summer. This allows ground-source heat pumps to operate very efficiently, making them an increasingly popular option for building decarbonization projects.

If you’re curious about how other types of heat pumps work, and the technology we often use to complement them, read a former “decarbonization for non-engineers” article on the topic here.

The installation process is quite different from other heat pumps, and is often the most visible and disruptive part of a geothermal project.

Using Wellesley Village Church as an example, the below video breaks down what happens during a geothermal installation, particularly during the drilling phase, without any engineering jargon.

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