From Sam Edge, Ringwood, Hampshire, UK
You report on a backpack that, as it moves, converts some of the bag’s kinetic energy into 118 microjoules of electrical energy 13 February, p 20.
In terms of electrical power (a better indicator of its usefulness), it probably amounts to very little, as is the case with any biomechanical energy-harvesting device that doesn’t impose unacceptable extra effort on the wearer. This is just a rehash of the “power your lights/phone/body heater/whatever from your footsteps” nonsense.
