“What is this wild looking thing?” Larry King asked his guest, futurologist Jaque Fresco in a 1974 interview. Fresco produced a drawing of a shining metallic circle of pipes and valves, lava spurting up in the background, and replied, “this is clean sources of power. By utilising the natural heat of the Earth, that is volcanic energy… we can get enough power to electrify the world. It’s easy to tap, it’s clean and available.”
There is no lava spurting from Grenoble’s snow-capped inclines, so how can the city achieve this remarkable aim? Well, Izoard explains, you don’t need a volcano – in fact, it’s the relatively moderate underground temperatures that make this system work so well, and that allow it to provide not only heating during the winter, but also cooling during the summer months. The temperature of the groundwater shifts around much less than the air temperature, so in the winter, the groundwater will be warmer than the air – perfect for heating homes – while in the summer, the groundwater will be cooler than the air – perfect for creating a refreshing indoor environment.
The sheer scale of this project, almost one million square metres of buildings, may seem like a challenge, but according to Izoard, it is actually one of the conditions of success. “We have been convinced that it is not just playing with the buildings that you can reduce consumption. When you change the scale you can do more than just changing the percentages.” Because the city can include so many buildings in the one project, it can take advantage of enormous economies of scale.
The basic idea here is not new, but there is one major innovation which is responsible for a huge increase in the efficacy of the system. “Basically it’s a very simple project. We use a heating pump for each building, and instead of having the pump pumping the groundwater, doing its job and reinjecting into the groundwater, which is what we have been doing for half a century and is not working very well, we will reinject elsewhere.” Formerly, one enormous intake would have pumped the water into the system and then each of the buildings would have drawn water from and returned it to the same supply.
The problem is obvious: after the water had been used for heating the first building, it would have less heat energy left for the second one, and so on: “When the first is doing its job, the second one just behind has less quality, the fourth one is worse, and the fifth can’t do anything. In French we call it ‘cannibalisation’ – too many things trying to do the same thing at the same time with the same resources.”
Equal for everyone
“You get exactly what you need”
Izoard’s advice for other cities? “If you want to reduce your impact, never use a big pump, use lots of little ones. Then you get exactly what you need in the place that you need it.” Now Grenoble is working to share the message of geothermal power with other cities, using projects like the EU-funded ‘City-zen’ to let other cities know that you don’t need a volcano to heat your home – a river will do just fine.