How does a geothermal heating system work?

Geothermal heating systems are becoming increasingly popular as people look for more efficient and environmentally friendly ways to warm their homes. Also called ground source heat pumps, these solutions harness renewable energy to help you keep your home at a comfortable temperature year-round. 

But how exactly do these systems work, and could they be a good solution for you and your home? Keep reading to find out.  

Taking their name from the Greek word ‘geo’, meaning earth, geothermal systems use the ground as their main source of energy. They can transfer heat to radiators and other climate control systems in your home, and provide hot water. Many of these systems can also be used in reverse in hot weather to provide geothermal cooling.

They take advantage of the fact that the ground just under the surface remains at a fairly constant temperature throughout the year. This means that by engineering systems that convey energy from the ground to the home, and vice versa, it’s possible to maintain a comfortable temperature in properties throughout the seasons. 

In winter, the relative warmth of the ground is used to heat homes, while geothermal cooling functions allow the systems to transfer heat from buildings into the ground during periods of hot weather.

Ground source heat systems work by pumping water containing antifreeze (called glycol) around a ground loop pipe that is buried in your garden. The length of the loop you require will depend on the size of your property and the level of heat you need to achieve a comfortable temperature. 

Longer loops will draw more warmth from the ground, but they need more space. If you have enough room in your garden, the loop can be buried underground in a horizontal trench. However, if you don’t have a big enough area in which to do this, another option is to lay the pipe in a series of vertical boreholes instead. These reach much deeper into the ground.

The space you need in order to install a horizontal loop of pipe or the depth you have to dig down for a borehole will depend on a variety of factors. Your heat pump installer will ensure that the design of your system meets the heat requirements of your home and is suitable for the local conditions.

As the antifreeze mixture travels through this loop, it picks up heat from the ground. This energy is then passed through a heat exchanger into a heat pump. These pumps work like a refrigerator, but in reverse. They take the energy that has come from the ground and transfer it into your home. Particularly environmentally responsible systems are now available that run these heat pumps using power generated on site by renewable sources such as photovoltaic solar panels, meaning they don’t have to rely on mains energy.

Geothermal solutions that also provide a cooling function simply work in reverse during spells of hot weather, transferring heat energy from the home into the cooler ground and making your living environment more comfortable as a result.

The temperature outside your home will vary a lot depending on the season, but the temperature of the ground doesn’t fluctuate anywhere near as much. This is because of the earth’s insulating properties. 

It absorbs nearly half of the solar energy (radiation) that our planet receives, meaning that even just four to six feet below the surface, temperatures tend to remain fairly constant throughout the year. This provides us with a source of ‘free’ heat energy that we can tap into with the right equipment.

If you’re considering buying a ground source heating system, you’re likely to come across the phrase annual coefficient of performance (COP). This is a way of assessing the efficiency of a system and it’s calculated by comparing the amount of heat provided by the system with the total electricity demand of the heat pump. 

The higher the coefficient, the more efficiently your heat pump system is working.

Geothermal heating systems don’t get as hot as conventional boilers. Whereas regular boiler systems tend to operate at around 70-80°C, ground source heat pump solutions usually operate at approximately 35-50°C. However, this doesn’t mean that you will feel the chill in winter if you have a geothermal system. These solutions are designed to be highly efficient and to provide continual heat during cold weather.

That said, it’s important to be aware that because they work at lower temperatures, these systems are typically best suited to well insulated and draught-proofed homes, and they can perform better with larger radiators or underfloor heating than with standard radiators.

There are many benefits associated with geothermal heating. One of the most important is the fact that it reduces the consumption of fossil fuels and is therefore kinder to the planet than conventional heating solutions. A related advantage is that it helps you to reduce your fuel bills, particularly if you are replacing a conventional electric heating system. It can also give you added peace of mind that you aren’t at the mercy of future potential fuel price hikes.

In addition, a ground source heat pump could mean you qualify for the government’s Renewable Heat Incentive. This scheme, which was launched in 2014, provides financial support to owners of renewable heating systems. If you qualify, you could receive quarterly payments over a period of seven years. An average four-bedroom detached home with a heat pump system could receive over £2,000 a year under this scheme.

Another benefit is the reliability of these solutions. Once installed, all they require is an annual check to ensure that they’re running correctly. The loops can last for generations, and the fans, compressors and pumps are designed for long term use with very little maintenance.

These systems are flexible too. They can be operated as standalone units or used in conjunction with your existing heating system to provide an extra source of heat.