What is geo-exchange and how does it work?
What is geo-exchange and how does it work?
In an era where energy efficiency and environmental sustainability are more critical than ever, innovative technologies like geo-exchange are paving the way for greener, more cost-effective solutions for heating and cooling buildings.
Geo-exchange, a form of ground source energy system, is an advanced technology that utilises the Earth’s natural energy for heating and cooling buildings. Unlike traditional systems that release excess heat into the air, geo-exchange stores this energy in the ground, allowing it to be reused when needed. This process takes advantage of the Earth’s stable, insulative properties and underground temperatures, which remain relatively constant throughout the year.
Figure 1: Erda|deep system showing how it can provide heating or cooling depending on the time of year
Benefits of Geo-exchange vs Traditional Systems
The key distinction between geo-exchange and standard ground source loop heat pump systems lies in energy storage. Geo-exchange systems store excess heat collected from the building or air conditioning/refrigeration byproducts during warmer months in the ground, making it available for use during colder periods. In contrast, traditional systems only draw energy from the ground/air without storing it, which can result in higher electricity consumption when those energy levels are low.
Geo-exchange systems offer significant efficiency benefits. By tapping into stored heat, they reduce the need for additional energy as the temperature of the ground is closer to the desired building temperature, making them a cost-effective and environmentally friendly option for heating and cooling buildings. This technology is already widely used in many countries, with proven reliability and effectiveness.
Think of geo-exchange as the next evolution in systems contributing energy to heat pumps:
Air source – Extracts energy from the air for heating but becomes less efficient at lower temperatures
Ground source – Extracts energy from the ground more efficiently than air source due to the consistent temperature compared with the air temperature
Geo-exchange – Stores and extracts energy via boreholes, ensuring that excess heat during hotter periods is not wasted
Geo-exchange Systems in Cold Climates
Concerns that these systems cannot be used in colder climates are unfounded. While higher temperatures can improve efficiency, geo-exchange systems remain economically viable even in colder regions.
Since the ground retains heat accumulated during warmer seasons, geo-exchange systems can draw energy from these warmer underground areas, maintaining efficiency that air source heat pumps may lose. This technology is also successfully utilised in colder climates like Norway and Canada, where seasonal temperatures are generally below that of the UK, yet it remains economically practical.
Finally, because geo-exchange is essentially the transfer of energy, it can achieve efficiency ratings or CoP (Coefficient of Performance) exceeding the most efficient boiler, typically within the region of 4-5 CoP for Erda systems, this means that for every unit of energy consumed, four to five units of heating or cooling energy can be generated. Alternatively, a gas boiler we observed can only achieve 82% efficiency as a comparison.