Generating electricity

A Japanese rail company is planning to experiment with using passengers’ movement through ticket gates to generate electricity. Not enough electricity to run the station by any means, but they seem confident that the number of passengers entering and leaving a busy station will generate a useful quantity of electricity.

This sounds like a brilliantly simple idea; I wonder why nobody has tried this before. Was it that the piezo-electrical technology was considered insufficiently robust for large-scale, long-term deployment. Was it that the energy storage technology available was too inefficient? Or was it just that nobody deemed it worth doing until now?

[Via Japundit]