This article appears courtesy of Lasse Skjoldan, Copenhagen Climate Council
In two Tokyo train stations, steps are under way to generate electricity from the floors of the ticket gates and staircases. If successful, passengers could help provide the train stations with 1,400 kilowatts per second each day.
Tokyo train station, 8 a.m. One of the 400,000 daily commuters passes through the ticket gate and walks the stairs to the train platform, as he has always done. But, for the moment, this walk is different. For each step the commuter takes, he generates electricity. The floors have been outfitted with power-generating mats that capture the vibrations of the pedestrian and transforms them into electricity.
So far, the power-generating floors are only on trial in two Japanese train stations – the Tokyo station and Shibuya station, which is used by about 2.4 million people on an average week day. When the test period ends in February 2009, the makers – Soundpower Corp. and East Japan Railway Company (JR East) – hope the floors have improved to the point that they can provide all the electricity needed to run the automatic ticket gates and electronic display systems.
Ten steps at a time
The technique behind the power-generating floors is called piezoelectricity, and comes from the ability of some materials to generate an electric potential when stressed or squeezed. When a person steps on one of the mats, the piezoelectric elements beneath it are stretched a little by the weight to produce a small electric current, which is captured by a mini-generator that turns it into electricity. (Read more about piezoelectricity here).
In late 2006, when JR East and Soundpower Corp. first put the piezoelectric floor to a test in the Tokyo train station, one average person with the weight of 60 kg (approx. 130 lbs.) generated 0.1 watt stepping across the tile. When the experiment was repeated in 2007, this power generating capacity had increased tenfold to 1 watt per second, along with an improvement in the resilience of the floor.
After the current trial period ends, in February 2009, construction engineers expect another tenfold increase in the generating capacity per passenger – with an aim of 10 watt per second, as well as a two-month capacity decrease of "only" 90%.
If these figures hold, an average of 1,400 kilowatts per second will be produced by the power-generating tiles covering 25 square meters of floor at Tokyo station's Yaesu ticket exit and seven steps of a staircase inside the gate each day. According to JR East, this will be sufficient to run the automatic ticket gates and the electronic display systems.
Dance floors, shopping malls, roads
While the idea of power-generating floors seems especially well suited for train stations where there are always people walking around, it is also being tested elsewhere. All that is required is some sort of kinetic power – someone or something moving to produce "good vibrations."
In Israel, "energy-harvesting" firm Innowattech is paving the way for power-generating roads, as well as power-generating railways and airport landing and takeoff runways. According to Innowattech, on a busy expressway with 20 cars and trucks passing per minute, one kilometer of road (0.62 miles) could produce up to 1 megwatt per hour.
In the UK, British engineer David Webb of the consultancy Scott Wilson says the "heel strike mechanism" – a technology related to piezoelectricity – is likely soon to be installed in railways, supermarkets, shopping malls, etc., as the technology proves more viable. According to Webb, the probable place to start will be the touristy Spinnaker Tower in Portsmouth.
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