Harnessing Geo Thermal Energy: An In-Depth Guide to Ground Source Heat Pumps

Ground source heat pumps, also known as geo thermal heat pumps, operate on a principle akin to an air source heat pump. The core function of these systems is to transfer heat between the inside and outside of your home, making them an efficient and sustainable solution for home heating and cooling.

How Ground Source Heat Pumps Work

In the winter, ground source heat pumps absorb heat from the ground to warm your home. This process is similar to how a heat pump works but is more efficient due to the constant temperature of the ground, which remains consistently cooler in summer and warmer in winter than air. In the summer, these same systems reverse the process, taking warm air from your home and returning it to the ground where it is absorbed by the cooler underground temperatures.

Alternatives to Traditional Boilers

One of the benefits of a ground sourced heat pump is its ability to replace a boiler, especially for radiant floor heating. While a forced air heating system is more efficient due to the higher air temperature required (about 75-80°F), a radiant floor heating system requires a higher temperature (about 110°F). This difference in temperature reduces the coefficient of performance (COP) from about 4x to 3x or even 2x, making the system less efficient.

Using a single-stage heat pump to heat a radiator system can be even less efficient, as the baseboard radiators usually require 150°F, which is almost prohibitive and often results in a very low COP. Despite these challenges, a forced air heating system may not always be the most comfortable option. In my experience, a room with a temperature of 68°F and a radiant floor is more comfortable than a room at 72°F using forced air. The heat loss from a cooler room may offset some of the lost efficiency.

Building a Sustainable Heating System

I am currently building a system for our radiant floors and will know for sure next winter if it saves energy. It will certainly reduce our use of fuel oil, which is substantial. Our home is powered by substantial photovoltaic (PV) arrays, and our local grid sources all its energy from 100% renewable sources. We do not need air conditioning, and it is unlikely that we would require it.

During the summer season, I sometimes cool the floor by running the circulator pumps to "warm" the cellar with the boiler turned off. The heat pump has a setting that allows it to keep the buffer tank at a summer temperature of about 50°F. Cooling the floors too much can cause humidity to condense, so I do not cool them below the dew-point.

Ground source heat pumps offer a sustainable and efficient solution for home heating and cooling. They can help reduce reliance on traditional energy sources and contribute to a more environmentally friendly lifestyle. By harnessing the constant temperature of the ground, these systems minimize energy loss and provide a comfortable and sustainable alternative to traditional heating methods.

Conclusion

Ground source heat pumps are a valuable tool for sustainable home heating and cooling. By understanding the principles behind their operation and their potential benefits, you can make an informed decision to improve the efficiency and comfort of your home. Whether you are building a new home or considering upgrades, integrating a ground source heat pump can significantly reduce your energy consumption and environmental impact.