By Will Clevett
A few years ago, Heathrow airport ground to a halt due to the cold weather; flurries of snow grounded some 4000 flights leaving somewhere in the region of 400,000 people delayed. On the 18th of December 2010, nearly 10,000 of those people were stranded, sleeping in the airport. A few months later they had started plans for a way to stop this from happening again; a heating system for the runway.
At first glance, this seems like a terrible idea since the energy requirements of such a system would be huge, however, to circumvent this huge power bill, thermal energy will be collected during the summer months from the hot tarmac as the sun beats down on it. This will then be stored underground in a very similar way to ground sourced heat pumps. After this the advantages become much more apparent; currently, unsavoury chemicals such as urea and glycol are used as de-icers on runways since salt and grit can interfere with the planes. When these chemicals are washed away, they’re really not good for the environment and on top of that, they don’t seem to be working that well.
Whereas; ground source heat pumps are a fantastically green form of heating, they work on the basic principle that below a certain depth in soil, the ground temperature remains fairly constant at around 10 degrees Celsius in the UK. Thus, instead of heating units which use electrical energy and transfer it directly into thermal energy, ground sourced heat pumps pump heat up from the ground, moving heat rather than creating it, and these can reach several hundred percent in efficiency. There are several ways this heat is stored. Some systems use large amounts of coiled piping buried a few metres under the ground. In systems where space is a factor, drilling equipment can be brought in to drill boreholes straight down instead.
In the case of the airport, a huge amount of energy is required, so a large amount of heat needs to be stored over the summer months to create a buffer for when the heating is required, the plan is to have pipes under the runway. Then, during the summer months, the tarmac can reach very high temperatures, radiating away most of this energy as fast as the sun’s rays hit it. Instead of wasting this energy, letting it radiate away, this system would collect this energy and pump it underground, storing it for later use by raising the temperature of the soil.
Implementation of heating on the runways at Heathrow would be a monumental task, since Heathrow can work at up to 98 percent capacity. Closing one of its two runways while installation took place could cause huge delays. One of the big problems at the end of 2010 was the buildup of ice and snow at the parking stands; the snow becoming far trickier to clear away with a plane in the way. One thought is to start implementing heating in the parking stands as a start, which would help free up a lot of snow clearing equipment for the main runways.
After two years we might finally be coming to the point where implementation may be going forward, so let’s hope Heathrow moves over to this fantastic clean technology and stops covering it’s runways in harmful de-icers. I’ll certainly be keeping an eye out to see what goes ahead.
Will Clevett is a student studying for a degree in natural sciences while working with Dando Drilling International, who make a large number of drilling rigs for applications around the world.