Thanks to space-age technology, commuters in Paris have a cool ride.
Metro Line One is the train that crosses the length of the capital city, and, according to the European Space Agency (ESA), Metro Line One is Paris' busiest underground line. More than 213 million trips are taken per year, serving 25 stations.
For the last year and a half, riders have been enjoying a perk - a nice cooling system that uses technology developed for space.
Usually, mechanical fans are used on metro trains to keep electric power sources from overheating, according to ESA, but in order to make more room for passengers, a French transportation company called Alstom took a tip from space.
Since there is no air in space, fans won't do to keep spacecraft instruments cool. So, scientists went the other way - to heat pipes.
The heat pipes contain liquid that circulates in the closed loop and carries heat away from a hot spot, according to ESA.
These rely on liquid. Circulating through a pipe formed in a closed loop, the liquid carries heat away from a hot spot. Part of the loop is next to the equipment giving off heat and another part is by a cold zone, like the outer wall of the satellite. Mechanical pumps aren't used, since they are likely to break down.
"In space, technology has to last for years or decades, without maintenance or repair," said Michel Ganseman, CEO at Euro Heat Pipes (EHP), according to ESA. EHP provides heat-pipe cooling for about 75 percent of all European scientific and Earth observation satellites.
"Picture dipping the tip of a sugar cube in coffee," said Ganseman. "The coffee is quickly drawn up into the sugar, through the pores, because of what s known as 'capillary' action." A porous material placed in one part of the heating pipe creates the same action as the coffee in a sugar cube.
Through the copper, stainless steel or plastic pipes, the cool liquid is sucked up and taken to the heat source where it turns to vapor. As it travels, the vapor eventually hits the cold source. The vapor then returns to its liquid form. The cycle repeats.
"It's a way to quickly transport liquid from one place to another without pumps or applying extra energy," explained Ganseman. "No mobile part is used, eliminating any risk of wearing parts and potential breakdowns of the system."
"If the technology was priced competitively for the metro, than it would be priced competitively for any type of train," said Maxime Vuckovic, marketing and sales manager at Calyos, a spin-off of EHP.
This could mean the technology is cost-effective for other parts of the world. "If you've ever been in the New York City subway in the summer, you know it can get up to 40 degrees (Celsius) in the station," said Ganseman, according to ESA. "The reason is, the amount of heat is so big, that the fans must keep dissipating it in stations."
"A more efficient cooling system could make a big difference," he continued. "Heat can be dissipated between stations, to bring down temperatures. And it will be less noisy for passengers."
