Ground Source Heat Pumps

What other form of heating provides a coefficient of performance, around 5 – 7? That’s the promise of ground source heat pump technology.

Last week I spoke to Senior Hydrogeologist at Geoscience Consulting, Huw Williams about this amazing technology. We discussed if it’s suitable for houses in New Zealand and why Huw is so interested in ground source heat pumps.

Huw Williams, Senior Hydrogeologist

Huw Williams, Senior Hydrogeologist

Huw Williams

Huw is passional about ground source heat pumps, but he’s also passionate about sustainability. That’s one of his key drivers for doing what he does, and it’s one of the reasons I was keen to interview him on the show. I enjoyed the chance to speak to someone who understands some pretty darn impressive, applied science.

Huw is a fellow of the Geological Society of London and has a Masters in Hydrogeology. He has over 10 years of experience in a whole range of groundwater topics.

What’s a Ground Source Heat Pump?

As Huw explains in this episode, a Ground Source Heat Pump is like a regular heat pump in that in transfers heat from one place to another. The key difference being that a regular heat pump uses a fan to blow air over coils and extract (or dump, in the case of air conditioning) heat from the ambient air. A ground source heat pump however has coils under the ground which extract (or dump) heat to the ground.

Ground source heat pump coils

Ground source heat pump coils, photo courtesy Geothermal Heat Pump Association of New Zealand

For more images and New Zealand case studies, head over to the Geothermal Heat Pump Association of New Zealand (GHANZ) website.

The potential high efficiencies of a ground source heat pump are due to the relative constant temperature of the ground, fairly close to the surface. That means that even in the middle of winter, the ground stays relatively warm and in summer, relatively cool. As Huw explained, the ground temperature close the surface only varies a couple of degrees either side of the average ambient air temperature for that region.

Should I get a Ground Source Heat Pump for my House?

Probably not. There are definitely opportunities in New Zealand for sharing a ground source heat pump with multiple homes. This could be economic at the early stages of a development. For most homes however, I suspect that the upfront cost of digging a large enough hole, may dissuade most people.

But we shouldn’t write if off entirely. The technology (even though it’s been around in some form since the days of Lord Kelvin) and the industry, is still evolving.

Would you consider one for your project?

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  • Elrond Burrell

    Another very interesting podcast Matthew. A great source for thorough and reliable information on heat pumps is http://www.heatpumps.co.uk/ John Cantor who runs the site is an authority on heat pumps in the UK and a lot of his guidance will equally apply in NZ.