Energy could be taken from the roads

We've always seen roads as a necessary evil, but what if they turn out to be a cheap source of energy?

At this time, any idea to alleviate our dependence on oil is welcome. Obtaining thermal energy is one of the objectives, but if it comes from something as black and available as a road, it’s all the better.

The idea is simple. It is about installing a series of heat accumulators under the asphalt that later, through a system of exchangers, is reused to heat water or heat buildings.

“Worldwide there are more than 18,000,000 km2 of roads, the potential is huge. And we are not talking about solutions for the future, but about proposals that are already a reality”, explains Nuria Uguet, the technical director of Eurovía Management Spain. The exchangers used by the system are actually coils with glycol water inside that heat up due under solar radiation. This circuit, similar to that of the heaters in many homes, is the one that is sent to nearby facilities to be used as a source of energy.

"Imagine the parking lot of a shopping centre. The exchanger, that is, the coil, can be installed under the car park driveway. This circuit is made like an "S" in a way that, as happens in the intestine of mammals, it allows a lot of travel in a very small surface. A heat pump is responsible for collecting the liquid previously heated by the sun under the asphalt so that it can be diverted to the commercial facilities and heated," adds Uguet.

The optimal moment

In Spain the road network is practically complete, except for some areas of expansion. In these new areas, the creation of these circuits does not pose problems because it can be executed at the same time as the construction of the track. But what about the rest of the network? The idea is to install this during road maintenance operations because at that moment the worn surface is removed and a new one is placed. The system is placed at a depth of 4 cm from the surface, in an intermediate layer under the asphalt, so that successive maintenance operations can be carried out without affecting the installation and without reducing the ability to absorb heat from the sun.

Is it useful in my house?

A pilot project of this idea already exists in France. In a building of 61 residential dwellings with a 1,400 m2 car park, 75 percent of the hot water needs are covered with this system. The saving has been 260€ per year per home but, what is more important, it has prevented 60 tons of CO2 from being expelled into the atmosphere. Tests have also been carried out in the Alps, where it has been possible to thaw the ice and snow in some sections, with the driving safety that this entails.

Cooler roads in summer

This "thermal circuit" also has its advantages in summer because it allows roads to be "heated" in winter and cooled by between 2 and 3 degrees in summer. It does this by absorbing all that extra heat and accumulating it to be used at the most opportune moment. Of course, it does not convert to an air conditioning system, but it is a valid solution for those areas of heat that are created during the summer period and which determine that the centre of the cities is hotter than the outskirts.

The system of exchangers and accumulators allows snow to be melted on mountain passes.