To find the best places for geothermal energy plants in Dublin, engineers tracked how noise vibrates through the rock formations under the city with underground microphones.
“There are natural vibrations by seismic activity as well as man-made sounds, like trains and cars and buses,” says Cian Desmond, head of innovation at Gavin & Doherty Geosolutions in Rathmines.
“If you make a noise in one place, it vibrates throughout the bedrock and by listening to how sounds vary, you can build up a picture of the structure of the bedrock.”
Geothermal energy could offer the city a source of heating with little or no carbon footprint. The energy source is “green, clean and viable”, says Desmond.
“It is a mindset change that we need to get around to,” he says. “You have these costs up front but then you have very limited heating costs for the lifetime of your building.”
The mapping project, called GEO-URBAN, is funded by the Department of the Environment and the European Commission and a sister project is underway in Catalonia.
They plan to publish a full report with the suitable locations in March or April this year, says Desmond.
Geothermal energy has long been used in parts of the world with access to volcanic rock. With improvements in technology, it is now possible in Ireland too.
A spokesperson for the Department of the Environment said it wants to hear from the public, from local groups, businesses, and other interested parties, on how they want to see the technology developed here.
Beyond Volcanic Rock
“The use of geothermal resources is more common and advanced in places where geological conditions give rise to high heat flow from the Earth’s interior.” says a spokesperson for the Department of the Environment.
Geothermal sources account, for example, for 66 percent of Iceland’s primary energy use, according to its National Energy Authority.
But recent advances in technology mean it is possible in other places too, including Ireland, said the Department of the Environment spokesperson.
Says Desmond: “The cost has come down and so less obvious sites are being investigated.”
The technology is already in use here too. The new ESB headquarters on Fitzwilliam Street Lower, between Merrion Square and Fitzwilliam Square, is set to be completed this year and has ground-source heat pumps among a suite of renewable solutions, says a spokesperson for the ESB.
Capturing the Energy
Geothermal energy is captured by drilling wells into the ground.
Engineers dig two wells of the same depth around one kilometre apart, says Desmond. “You put water into one well and then it drifts through the natural cracks in the bedrock and leaks into the well that you have got a kilometre away.”
Passing through the underground rock heats the water, which runs into the second well, and can be used to heat or cool buildings, he says.
Geothermal energy is almost carbon neutral. It takes a pump, but if that is run off renewable electricity then the entire system is sustainable.
It is not commercially viable in all areas, so by mapping the geological characteristics they reduce the risks for people considering installing it, he says.
Weighing It Up
Imagine never rationing heat again. “You would have so much heat you wouldn’t know what to do with it,” says Desmond.
Geothermal energy can be used to create electricity but it is more efficient to use it for heating, says Desmond.
Heating accounts for 39 percent of our energy use in Ireland compared with electricity which is 19 percent, says Desmond.
The other renewable energy source for heating is air source pumps, he says. To work out which is better, you need to weigh up factors such as a building’s heat needs and the geological make-up of an area.
Geothermal is often more suitable for larger developments and those with big heating bills, he says. Like hotels, universities, and leisure centres.
A developer building a complex could decide to incorporate geothermal heating. “Instead of everyone having their own heat pumps you can have one single well, that they are all sharing,” says Desmond.
If the owner plans to pass on the home to children and grandchildren, the heat supply is an ongoing advantage for the family, he says.
“There is no silver bullet for climate change. It will take all types of renewable energy solutions working together,” says Desmond.
The cost of oil and gas are likely to increase in the future, says Desmond, so that should also be considered.