Forgive me if the idea appears somewhat naive. Please correct me if I'm wrong about this but, given that the "frozen" water exhibits thermal properties of ice, in theory couldn't a closed system be built to generate electricity given the constant displacement of water running through the system. By taking advantage of the constant cycle of temperature variations within the system?
EDIT: Just looked it up, it appears difference in weight between 4 deg C and 21 deg C (1 ft^3 of water) is a little more than 1/10th of 1 lb.
EDIT: Just looked it up, it appears difference in weight between 4 deg C and 21 deg C (1 ft^3 of water) is a little more than 1/10th of 1 lb.
http://water.usgs.gov/edu/density.html