Plain old gravel could hold the key to greener power stations
 

Renewable energy is getting better all the time, but no-one's yet worked out a good way to store the juice for those cloudy, windless days. Batteries do work, but given the high cost of swapping out the cells for your EV, we doubt that Duracell will..

http://www.engadget.com/2014/06/06/p...=rss_truncated