Geothermal Heat Pumps

Geothermal Heat Pump technology has gained a lot of publicity over the last few years, due to its revolutionary energy management potential and its ability to be used for both heating and cooling applications throughout the year.

However, this technology relies on the fact that the Earth (below the surface) remains at a relatively constant temperature throughout the year.

In summer the ground is often cooler than the ambient and thus has the ability to absorb the extra heat that is often produced from an air conditioner system.  Likewise in winter, the ground will be warmer than the ambient temperature and thus can provide the extra heat required to heat a house. Geothermal systems have also been used in swimming pool heating, house temperature control (as mentioned) and many other heating and chilling applications across domestic, commercial and industrial processes.

The suitability of a Geothermal in any given area has a few key areas for consideration.

• Step 1. Know your Heat Load Requirements.

Regardless if it is for a Greenhouse, Swimming Pool or for Air-Conditioning loops, the very first thing you need to do is the size your project.

Engage an expert and find out how big a system you require. The Geothermal needs for a 10 kW system are immensely different to a 100 kW system. So what you know about your heat or energy loads you can then look at the other steps to determine the suitability for a Geothermal system over other options.

• Step 2. Compare Ambient Temperature averages versus Ground Temperature averages throughout the year.

Locations, where you have an ambient temperature for more than 60% of the year above 20 Celsius, may suit geothermal for cooling needs, but are not so good for geothermal heating applications. In Australia areas such as Queensland and Northern Territory fall in this band. Areas that have more than 60% colder than 20 Celsius ambient temperatures would be great for geothermal heating use, but usually not so good for chilling applications. Where areas more balanced to the 50:50 throughout the year may be suitable for both applications.

• Step 3. Do a Ground Substrate Survey

Underground water and moister soils make for better heat conduction conditions for Geothermal use. Where sandy and very dry soils are poor conductors and not very suitable at all. You should always do a ground survey to gain a better understanding of your suitability. Also, a substrate survey will show how deep you may need to dig for geo-pipe installation.

• Step 4. Horizontal or Vertical geothermal System

Once you know what capacity you require, the soil type and geothermal suitability, you will then know how big a system you will require.

You now have to see if you have the room for a horizontal geo-pipe system or have to dig down for a vertical geo-pipe system. A horizontal system takes far more room but is a lot more cost-effective to do.

• Step 5 – Perform an Energy Audit

By this point, you should know the size of the system requirement(s), where and how you may intend to install the geothermal system. However, a critical thing to consider is balancing your needs and the energy needs of the geothermal system.

If you draw heat from the ground only, over time the energy in the surrounding ground may deplete causing decreased efficiencies, freeze-ups and other complications.

Balancing heating and cooling loads, knowing how quickly or how long it will take the ground to recover the energy levels is very important. For example, an underground aquafer is an ideal location as it will constantly recharge your geothermal area.

Most of Australia has more temperate ambient conditions, and thus does not have the same cold winters as Europe (where geothermal is highly popular) and thus often do not have all the benefits of a geo-system available to them. Areas such as country towns, Canberra, the Mountains where winters go below 5 Celsius and over 30 during summer often come to enjoy all the benefits of a geothermal system.

Geothermal systems are often fairly expensive to set up the ground loops, ready for the Geothermal Heat Pump installation. However, as the pricing of electricity and gas go up, we are all looking at ways to be more efficient and reduce our running costs. There are also people and companies, less concerned about installation costs, that want to reduce their impact on the environment, without losing creature comforts or project outcomes.