Geo-exchange: green potential muddied by misconceptions
Kevin Stickney, Managing Director, Erda Energy, discusses how the merits of ground-source heating and cooling are obscured by common misunderstandings
We’ve made major strides towards decarbonising power and transport, but heating, which makes up 32% of our total emissions, is the missing piece of the decarbonisation puzzle with much of demand still met by fossil fuels.
This needs to change – not just in homes but in commercial premises too. And it will. The questions are how and when.
One option that already exists is geo-exchange, also known as both ground source heat and as geothermal. It’s a proven technology in the field with a strong track record. But it’s underutilised, at least in part due to some stubborn misconceptions.
Geo-exchange – a good grounding for decarbonisation
Geo-exchange works on the basis that, below the earth, temperatures are consistently between 10°C and 15°C all year round. For most places, this means that the ground is warmer than the surface in winter, and cooler in summer.
Geo-exchange runs with this principle. A heat-conductive liquid is circulated through boreholes into the earth, either picking up or getting rid of heat. Using electricity, the heat pump concentrates this heat and circulates it throughout the building, but it can also operate in reverse, collecting heat from the building’s air and expelling it into the ground.
We know how to decarbonise electricity on a mass scale so the logic follows that if we can run other energy processes using electricity rather than by burning something (e.g. natural gas) we have a route to decarbonisation.
Widespread benefits
Well-designed geo-exchange typically lowers cost on an annual basis, as you are no longer paying for fuel and the related infrastructure. This is a powerful commercial proposition for businesses who have a responsibility to provide a temperate environment.
Locations with high energy needs such as supermarkets and hotels are especially well-suited to geo-exchange. Here systems can also harness heat produced as a by-product from equipment such as freezers and refrigerators; boosting efficiency and adding to the financial benefit.
And National Grid, tasked with balancing the grid, can also benefit. Increasing electric vehicles and electric heat, along with intermittent renewables, are causing more peaks and troughs in demand. Like a battery, geo-exchange can time-shift electricity supporting grid operators to smooth out the load.
Ground source heat: thinking deeply
Despite these benefits, geo-exchange and GSHPs have had limited uptake. The opportunity is far larger. Partly, this can be attributed to the marginally higher upfront costs and longer wait on ROI compared to fuel technologies that enjoy economies of scale and rich subsidies. But another problem is that geo-exchange has struggled to shake some stubborn misconceptions.
In no small part, these stem from loose terminology; the terms geo-exchange, ground source heat pump (GSHP) and geothermal are often used interchangeably.
Geothermal typically refers to a technology that uses ultra-deep boreholes to access heat from the Earth’s core or in areas of volcanic activity; think Iceland. In contrast, GSHPs typically drill down around 10-60ft where the heat has been contributed by the sun.
Geo-exchange is a more efficient and advanced version of the GSHP concept, typically drilling much deeper (around 650ft) and capable of using the ground as a thermal battery in order to produce both heating and cooling.
If this sounds like a pedantic distinction, it’s not. It can lead to real confusion. For example, potential geo-exchange users may mistakenly think they need to sit atop an area of volcanic activity and discard the option without consideration. Or they might see frozen ground and dismiss the idea of subterranean heat. Equally, the mix-up can obscure the great ability of geo-exchange to provide cooling as well as heating.
In an age of fast-paced energy transition, terminology matters. Geo-exchange can be a key contributor to decarbonisation efforts offering real benefits to British businesses, households and grid operators; we can’t have confusion hamper its uptake.
[1] Clean Growth Strategy p.9 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/700496/clean-growth-strategy-correction-april-2018.pdf