We've known about Ireland's thermal springs for more than a century. Now's the time to exploit their potential, writes Bart Connolly.
The phrase "thermal spring" conjures images of continental spas, hot pools and geysers. Yet warm water from the ground is nothing new to Ireland. It also offers a way to save money on our heating bills and even cool our homes and offices in summer.
In 1757 a Dr John Rutty, of Bristol Spa in England, published a book about mineral water. In it he wrote: "Mallow water was first discovered and introduced into practice by Dr Rogers of Cork about the year 1724." It makes Mallow the oldest Irish spring on record. It is also the warmest, recording year-round temperatures of 20 degrees.
Louisa Bridge spring, in the Co Kildare town of Leixlip, was discovered during the construction of the Royal Canal, in 1794; Kilbrook spring, near Enfield in Co Meath, was unearthed during railway quarrying in the 1890s. A third Leinster spring, St Gorman's, was also known about in the mid-19th century, but it was subsequently forgotten. We now know that the Republic has 29 warm springs.
Ecoserve, a Dublin-based ecological consultancy that has studied eight of them, found that they varied in many characteristics, such as temperature, acidity or alkalinity and the amount of dissolved oxygen they contained. This meant flora and fauna also varied.
Ireland has a tradition of holy wells, and pilgrims influence plant life. Covering wells makes them safer but deprives plants of light. Litter and dumping are also persistent problems. Ecoserve's study identified "a marked trend in faunal community characteristics in association with the impact of human disturbance". More than 90 animal species were recorded. Springs may favour crustaceans rather than insects, perhaps because the habitats are not suitable for insects' life cycles.
What is the value of such springs? Contrast this water and heat with the current fascination for life on Mars - a cold, dry planet. Life needs an energy source. Water not only imprisons hydrogen, which would otherwise leak into space, and oxygen, which facilitates rapid bursts of energy, but also provides a medium through which life can quickly spread over the surface of a planet.
Where does the heat come from? Earth's average density is over five times that of water. The planet probably has an iron and nickel core. As Earth formed heavier elements sank deeper into it. Radioactive elements tend to be dense because they have large nuclei. Energy from their radioactive decay builds up over time, in spite of the odd eruption. The crust is about 30 kilometres thick, its lower levels reaching temperatures of between 750 and 1,000 degrees. The core is thought to reach 7,000 degrees - hotter than the surface of the sun.
There are economic possibilities for our springs. Heritage tourism could be developed. As Ireland is not a geothermally active area, it does not have very hot springs. But the springs it does have are still clean sources of abundant energy.
We can pump geothermal energy, making a spring work like a freezer in reverse. Trinity College in Dublin has a geothermal pump that heats six buildings. Boreholes give the system access to water with a temperature of 14 degrees, 10 metres below ground. The pump provides the buildings with heating and cooling without chemically changing the water. That water currently returns to the ground at 25 degrees; Trinity intends to use it to heat a swimming pool in its new sports complex, so in future the water will return to the ground at the temperature it emerged from it at.
This technology is not reserved for research institutes. In Iceland at least 30 community-owned systems heat more than 80 per cent of houses; Reykjavik's municipal heating system serves more than half of the population.
Geothermal heat pumps reduce home energy costs by between 25 and 50 per cent - and work in reverse in the summer, cooling houses when the ground temperature is lower than the air temperature.