A guide to geothermal energy

Clean and sustainable energy sources are a huge topic of discussion whilst we battle with climate change and look for less damaging and more sustainable energy solutions. With new innovations coming into play regularly, we’re going to take a look at how the earth beneath your feet is an energy resource – one that most people never take into consideration.

What is geothermal energy?

Generally speaking, geothermal energy is the heat from the ground beneath you, whether it’s shallow ground through to hot rocks and water found deep below the surface. In most locations – around 30 feet below the surface – we will find that it stays at a constant temperature ranging between 10°C and 60°C. This is due to what’s called the “mean earth temperature” and is regulated due to the wells of water typically found at these depths underground.

How does geothermal energy work?

In using geothermal energy, you would use heat pumps to tap into these resources in order to heat and cool entire buildings, regulated depending on outdoor and indoor temperature. One of the earliest examples of using geothermal methods as a heat source can date back as far as the Roman times, where they heated entire homes, baths and public buildings using hot springs partnered with tiling and piping within walls. In modern times, geothermal energy is harnessed by installing pumps using loop systems underground and bringing the heat to the surface.

These systems are either closed-loop ones (vertical and horizontal as well as water installed) or open-loop ones. Closed-loop ones run continuously with an anti-freeze style liquid whereas open loop runs domestic water through the system and discharges it after.

A geothermal heat pump consists of a heat pump, an air delivery system and a heat exchanger – a system which is buried within the shallow ground. Depending on seasonal weather, the system can be reversed. Heat is removed from the ground by using the heat pump and the heat exchanger to pump warm air into the indoor air delivery system during the winter months. This process would be reversed in the summer, when the heat pump would instead move heat from the indoor air system into the heat exchanger, exchanging it for cooler air or a source of hot water.

The geothermal potential of the ground beneath you can be harnessed using either of these loop systems:

• HVAC (Heating, Ventilation and Air Conditioning) – Typically found in boilers and chillers transferring energy through air or water systems, providing your household with various methods of cooling and heating your home or water.
• GSHP (Ground Source Heat Pump) – This method can also be used for either heating or cooling and sometimes cutting your heating costs depending on the installation. This time the pipes are buried under ground to extract energy.

What’s the cost of geothermal energy?

The initial cost of installing a loop system can vary depending on whether you will be harnessing this energy for your home or an entire building. Unfortunately, the costs are high to start with. However, the return in form of reduced monthly energy bills across several years is definitely worth it. Roughly speaking, you could be looking at costs between £9,000 through to £15,000 depending on the type of installation you require. The time until you break a return on this investment also depends on the scale of the building.

Geothermal Energy – Pros and cons

At first sight, installing geothermal energy into every home and building in the world would seem like a no-brainer given the huge economic benefits and cost savings. However, not all stories have a happy ending, and below we have put together a list of pros and cons surrounding geothermal energy.

Advantages of geothermal energy:

• No significant evidence of pollution and environmentally friendly in comparison to gas or oil sources.
• A larger percentage in savings on both heating and cooling as well as being all round more efficient.
• Constant costs, unlike with gas and oil prices.
• Incredibly long lifespan due to its minimal build and mixture of indoor and underground components.
• Out of all the heating and cooling sources it leaves the smallest carbon footprint as well as leaving a minimal footprint in the landscape due to it mostly being built underground.
• There is a large amount of room for improvement, i.e. the efficiency of this energy source can always grow with new technological advances.
• Is more energy efficient by simply moving heat from A to B.

Disadvantages of geothermal energy:

• Electricity is still a requirement for the systems to work. Not only this but if the source is water, there will be a high amount of usage.
• The cost of repair and maintenance is very high in addition to the high installation cost. Repair and maintenance will most likely be required due to tree roots, decay from surrounding soils as well as pests.
• Can be dangerous to the Earth’s surface due to discharge into the ground, which can include sulphur dioxide.
• Fitting geothermal systems into existing homes and buildings can be complicated, therefore making it more suitable for new builds.
• Installers can be harder to find for GSHP installation than HVAC due to its complex nature and the amount of work required from the offset.