Mythbusting: Ground Source Heat Pumps

This week we are taking a look at Ground Source Heat Pumps and aiming to blow away some of the lingering and popular misconceptions about the technology. Let’s get mythbusting…

Ground Source Heat Pumps Common Myths

Myth 1: Collector pipes have to be buried deep in the ground

Heat pump horizontal collector pipes are normally buried between 1.2 and 1.8m below ground level. They are not as some people suggest absorbing heat from the Earth’s core, but are in fact absorbing low grade energy from the earth produced by the sun heating the ground.

The pipes need to go deep enough to be protected from ground frost and benefit from stable annual ground temperatures but not so deep that it is overly expensive to install them.

Myth 2: The collector pipes freeze the ground

Whilst it is true that the fluid in the collector pipes does get very close to zero and in the depths of winter may fall slightly further modern design practices ensure that this ground freezing does not occur and affect the ground detrimentally.

In older installations there have been occurrences of ground freezing but these have been categorically related to poor design and negligent installation.

Correct best practice design and installation of pipes at an appropriate depth mean grass, crops and shrubs are not affected in any way by the presence of collector pipes.

Myth 3: You need lots of ground available

Horizontal heat pump collector pipes do indeed need much land depending on the site and ground conditions but for those with smaller gardens all is not lost. Borehole technology allows vertical 100m holes to be drilled making huge space savings.

A standard borehole is about 150mm in diameter and needs a 3m radius of clear ground surrounding it and can typically harvest 5kW of energy from the ground. Each borehole nominally needs less than 1/10th of the ground area than its horizontal collector cousins.

See our guest blog from Nicholls Boreholes for more details.

Myth 4: They can’t do hot water

Most standard ground source heat pumps will achieve 50C without immersion backup providing ample hot water for the home. Whilst heat pumps indeed become more inefficient at higher temperatures they are suited to almost all hot water applications.

Myth 5: Ground source heat pumps don’t work with radiators

Heat pumps in general work far more efficiently at lower temperatures in the range of 35-45C compared to 60-70C for traditional fossil fuel boilers. As a result for the same output into the room to keep it warm if the flow temperature is lower the radiator area needs to be increased.

Even if you don’t have any more wall space for bigger radiators there are even available low flow temperature radiators that allow you to keep the same radiator “wall print” but with the same thermal output as a standard radiator giving you the best of both worlds. Read our blog on low flow temperature radiators for more info.

If you have any further questions or have heard something about ground source heat pumps that you would like verifying, leave a comment below.

photo credit: @Doug88888 via photopin cc

Doug Johnson

Doug is a chartered mechanical engineer and has had the pleasure of being involved in the UK renewable sector since 2008. With wide-ranging operational and design experience in both the domestic and commercial sectors across a wide range of recognised technologies he hopes to be able to share his experience to help enlighten and save you hassle along the way.