Like most cities in Europe, Glasgow has a rich past. It was a small merchant town before the industrial revolution, and now, with 600,000 people, it’s the largest city in Scotland. We wanted to visit Glasgow for a unique idea that the Scottish government is developing to meet some ambitious energy goals. By 2015, the country wants half its energy to come from renewable sources. Five years after that, the goal is 100 percent.
Part of the answer may be under the streets, down in caverns more than 200 years old that were excavated for coal. As coal mining became too expensive in Glasgow in the 20th century, the mines were abandoned. The pumps that kept water from trickling in were shut off, leaving the tunnels to flood.
Now, below the feet of Glaswegians, there’s are more than a million gallons of water sitting in the caverns, heated by the Earth. No matter how cold it gets in chilly Glasgow during the winter, the water still stays fairly warm by comparison, about 51 degrees F (11 degrees C) near the surface. The deeper you go, the warmer it gets.
To understand why that matters, we talked with Diarmad Campbell, an energetic Scot with a fantastic title. He’s the chief geologist of Scotland, working for the British Geological Survey.
The water is dirty, but the heat it holds is valuable. Geothermal energy is often discounted (or, at the very least, not considered part of the renewable energy equation) because it’s simply not visible the way you’d find solar panels or wind turbines. But the heat in the water can be potent, and Campbell’s team estimates that the energy in the water could meet the heating needs of more than 40 percent of Glasgow’s homes and businesses.
To get there, the first step is to map the caverns to find out just where the water is. Then the city would build pumps at four different locations to extract the water out. At the surface, it would be run through a heat transfer device that would remove the heat. Then the cool water would be put back in the ground, where it would heat up again.
Other countries already do this. Germany and Sweden have invested in this technology. According to one estimate, there are 10,000 heat pumps installed in the UK, and many more around the world.
But Glasgow’s seems a bit more enchanting because of the haphazard way the idea came together. “It’s by accident that we’ve created this opportunity,” Campbell told me. No one could have known 100 years ago that coal mining would help power the city centuries into the future. Let alone on renewable, clean energy.