A hydroelectric dam converts mechanical energy (gravity acting against water) into electrical energy.

What form would this energy take if the dam did not exist? Would it be thermal energy (from friction as the water flows)? Would it be purely mechanical (the dam reducing the water's momentum)?

A solar panel, for example, converts radiant energy (from the sun) into electrical energy — diverting it from the ground that it occludes (likely becoming thermal energy). But I'm having difficulty figuring out the equivalent for a hydroelectric dam.


You are correct. Most of the water's gravitational potential energy would have be converted into thermal energy in the absence of a dam. I would think it would depend on the original topography. Water going over a waterfall would result in a higher fraction of thermal energy right a way. Water flowing down a more gradual incline would result in kinetic energy of the water which sooner or later would get converted to thermal energy.

There is a famous story of James Prescott Joule investigating this very idea on his honeymoon when he and his bride travelled t Switzerland and visited the falls near Chamonix.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.