‘Energy from the ground has always been around’
There are a number of advantages to using geothermal energy in its primary form — heat — in the agri-food sector.
In Ireland, the use of geothermal energy resources is limited, mainly confined to small-scale individual heating projects, such as in individual dwellings or industrial heating applications.
However, according to experts, there are a number of advantages to using geothermal energy in its primary form — heat — in the agri-food sector.
According to the International Renewable Energy Agency, using this for greenhouses or for food drying and processing has the potential to increase food availability, reduce dependency on fossil fuels, protect against price volatility, diminish harmful emissions from the sector, and reduce food waste.
The Geothermal Association of Ireland has said geothermal energy and the use of heat pumps is “very efficient”.
The system can be more expensive to install than traditional gas or oil-fired systems, but has “very low running costs” from thereon, meaning that while it may require grants or loans to get started, it could pay dividends in the long run.
Costs for geothermal systems can vary greatly.
However, a ground-source heat pump is likely to cost upwards of €12,000, depending on size, hot water storage, and ground loop system. The largest industrial set-ups, more suited for the processing sector, can cost up to €1m.
Niall McCormack, chairman of the association explained: “It is used around the world in environments not dissimilar to Ireland for lots of different things, including in the agri-food sector.
“There are three things you’re solving for: Sustainability, energy security, and energy affordability.
“One of the reasons geothermal is attractive is because it’s sustainable and secure, and what’s happening over the last few years is that it has become economically competitive.
“You see enormous amounts of deployments in places like Sweden where the ratio of electricity price to natural gas price is low.
If you’re somebody who’s looking out there for 20 to 30 years time, this is a strong economic system, he says.
Mr McCormack said that in Ireland, there has been “very little driver to move away from the status quo” and move towards the use of geothermal energy over the last number of years.
However, there are now “multiple drivers”: Gas price volatility, gas security of supply, and sustainability — the “three pressures coming onto industry and agriculture”.
“Heating and cooling in the agri-food sector is an area where it’s easy to decarbonise,” Mr McCormack said.
“There are other elements that are quite hard to decarbonise and to reduce greenhouse gas emissions, but this is one where there’s actually no impediment to doing that.
“The technology works at pretty much every scale, so it’s not scale-dependent.
“You can go from your house which is around 10kW, to megawatts which is a large processing plant.”
As far back as the Roman times
Vice-chairman of the association, Ric Pasquali, added that all the technology to install a geothermal system is “off the shelf”.
“We’re not talking about stuff that is under research or that’s under development,” he said.
“Geothermal has been used as far back as the Roman times.
“Energy from the ground has always been around and it has been used more in some places than in others.”
Mr McCormack explains it simply: When you go down into the earth, it gets hotter.
“There’s two places the heat comes from — one is from the centre of the earth, it’s cooling down very slowly over billions of years. The other is that the rocks themselves generate some heat.
“As you go down, on average, it’s between 25C and 35C per kilometre. Across the world, however, there are some places where it’s a lot hotter and some places where it’s a lot colder.
“Ireland is about average across the island, give or take.”
Geothermal energy involves accessing this heat and using it.
There are two ways in which it can be accessed.
In an open-loop system, heat is collected from water underground. Closed systems take heat directly from the soil and rocks in the subsurface.
“We drill holes. If you want to go shallow, dig a ditch, put some pipes down, and bury it. That’s normally deployed for smaller-scale deployments. It’s basically like solar panels but you’re using the ground instead of panels on a roof,” said Mr Pasquali.
“When you want more energy, you normally drill a bit deeper. You’re drilling a well down and you’re putting a pipe in the well and you’re circling water through that pipe and you’re collecting the heat from the system.
“At the surface, you have a cool piece of kit, called a heat pump. Heat pumps are the magic that then takes the 15C and allows you to convert that into 60C to 80C.
“The deeper you go, the hotter it gets.”
Accessing energy at a later stage
Mr Pasquali explained that harnessing energy into heat can also deliver on cooling needs simultaneously.
“This is one of the massive advantages of geothermal - it’s not either this or that,” he said.
“You could be taking 12C water into a heat pump to produce heat, but at the same time take the same water at the back end of that heat pump to cool something else.
“The other aspect that we can’t forget is that you can also do energy storage.
“You can take energy from the surface in the form of heat and store it in the ground for a period of time and then access that energy at a later stage for something else.
“A really simple example would be if you were cooling a building in the summer months, you take the heat from that building and you put it in the ground, and then you reverse the cycle in the winter, with or without a heat pump there’s a number of ways of doing it — but you can take that energy back into the building when the cycle changes or you can do it simultaneously.”
In some places around the world — not many in Ireland — Mr McCormack said that it “can get hot enough quickly enough that you can produce electricity from it”.
However, “realistically, you’d normally need the temperature to be over 150C for the economics”.
Mr McCormack added that going forward, how licensing of geothermal resources is done is “incredibly important for the end-user so that people can develop the heat resources they have around their farms and facilities”.
