Pavegen: Harvesting kinetic energy from every footstep.

Is this energy / cost efficient? I.E. Is the mechanism itself (foot traffic generated energy) required and relevant to have the lighting, advertising, and way-finding? I love the idea of these kinds of unique installations (reminds me a bit of Sistine Solar in the sense of transforming our ideas of energy generation). But I always wonder whether the full on economics make sense, especially considering that tearing up concrete is expensive, messy and time consuming. So if an average person has a mass of 60-70KG, walking they're generating a force of F = mg - mv^2 / r, where the radius is around 1 meter. How much of that force can be converted into stored energy and then used? I only ask because the idea of a 'human powered gym' has occurred to me (and a few others) at some points and I recall it not being feasible. But maybe the tech has changed.

Turns every step into renewable energy, all of which can be used to power applications such as pedestrian lighting, way-finding solutions and advertising signage. The tiles are wifi enabled which means the energy collected can all be tracked. Cities can also track where the highest level of footfall is, i.e. where people are walking most.