Iceland is a small country in the North Atlantic, where the Mid-Atlantic Ridge peeks out from above the waves. It’s a constructive plate boundary, which means it’s where two tectonic plates (the North American plate and the Eurasian plate) are pulling apart from each other. This leaves a big hole in the Earth’s crust and so magma, molten rock, rises up from the mantle to fill that hole.
This is important.
Magma is very slow to cool. I’ve sat in the red dust at the peak of Eldfell, the volcano that tried to destroy Heimaey in 1973 and quite literally just beneath the surface the ground is still steaming. Three feet down and it’s hot enough to bake bread. Last time I was up there was 2016, so that’s 43 years after the eruption.
Imagine how hot it is a bit closer to the mantle, the layer of molten rock below the crust. You can’t imagine how hot it is. Water leaks into the crust, seawater mostly, falls down through cracks. A few hundred metres down, it’s hot enough to boil it. But in a fun but of physics, the pressure down there is so high that the water remains in a liquid state a very long way above temperatures that would have it turning to steam at surface pressure. That means water hotter than you can imagine possible.
Icelanders – by which I mean workers at geothermal power stations, although there are a few people in the countryside who drill their own – drill boreholes in the ground to bring that hot water up. On the way up, the pressure drops and the really hot wster turns to steam and then just like in a conventional coal-fired power station, the steam turns the turbines that generate electricity. They let the steam cool and turn back into water and then they can either pump it back into the ground to reheat or send it next door to fill the local geothermal spa. I’ve said it before and I’ll say it again: the Blue Lagoon’s famous mineral-rich milky-blue spa water is waste run-off from the power station next door. Feel luxurious now?
So that’s geothermal energy. As a very tough rule, geothermal electricity is supplied to homes and businesses. You can also send hot water, usually from a dedicated spring rather than a borehole, as their hot water supply or you can use it to heat clean sulphur-free spring water to make free hot water that doesn’t smell literally like Hell itself, or you can use it as free underfloor heating to keep your main shopping street or international runway clear of snow all year round. Yes, Iceland does this.
Then there’s hydro power. That mostly supplies industry and although Iceland generates far more hydro electricity than geothermal electricity, you won’t hear it talked about so much. It works out at pretty much 70/30 in favour of hydro. I think that’s partly because it’s less exotic, partly because it’s hidden away in the Highlands and partly because of the environmental aspects.
Hydro power involved damming a river and then controlling its exit, using pure water force to turn turbines. Iceland had no shortage of powerful glacier-fed rivers up in the Highlands. But of course what happens when you build a dam? You flood an area. There’s no issue of drowning villages. This is happening in remote, inhospitable, uninhabitable parts of Iceland. But Iceland, more than most nations, is pretty environmentally-minded. You’re wiping out waterfalls and mountains and deserts. You’re causing permanent irreversible damage to the landscape.
The most famous dam and most famous protests were Kárahnjúkar, the largest hydro power station in Europe and the largest power station of any type in Iceland – not surprising, geothermal ones are fairly small. Kárahnjúkar covers 1000 square kilometres and formed a reservoir the size of Manhattan. It can produce 4,600 GWh per year, which is nearly a quarter of Iceland’s total energy use.
The one big non-renewable form of energy that Iceland uses, and has to import, is petrol & diesel for cars. No oil hiding in the magma that underpins the country. Oil is the well-squeezed juice of pre-historic plants and animals, captured in the rock. Iceland didn’t exist in pre-historic times so it can’t capture any remains and it doesn’t really have many plants and animals so it’s not like it’s a late starter that will have oil in half a billion years. I’m not sure its rock would be capable of juicing anything anyway.
But Iceland is big on cars, especially big ones on oversized suspension. Its public transport network is pretty much exclusively the private car. A dozen buses once a day, more in the region between Selfoss, Reykjavík and Borgarnes. No trains. Cars need fuel so fuel must be imported. Can’t run a car on geothermal electricity – although once we’ve perfected the batteries in electric cars, surely Iceland is the ideal home for that.
(Electric cars run off geothermal power stations are going to be green as green. At the moment your electric car is still producing loads of emissions, it’s just at the coal-fired power station where they generate the electricity rather than your exhaust pipe.)
Iceland is one of the greenest countries in the world (not plant-wise; it’s pretty barren, 11% glaciers and about 0.05% trees) but once it clears up the issue with all the petrol, it could be the single greenest country in the whole world.