Good idea, because it allows for a very low-tech solution(!). The very good news: once you have a 900' reservoir, your work(!) is done: just turn on the tap. Problems: seawater is usually at sea level, so this requires pumping seawater to a high reservoir. Next problem: reservoirs at 900' altitude are typically fresh water reservoirs, so this seawater reservoir would have to be lined to keep the seawater from leaching into the soil & causing other environmental damage. Final problem: you then have to pump the fresh water back up to where it is consumed (this is already a problem in San Diego, where the pumping cost from their desal plant is not insignificant). At 05:49 PM 4/23/2015, rcs@xmission.com wrote:
During the 197x Energy Crisis, there was an article in Science pointing out the osmotic pressure difference between fresh water & sea water was equivalent to a 900 foot dam. The authors had a proposal to extract some of that as usable energy, building some dam-like gadget at the mouth of a river. Points in favor: sizable new energy source, tolerable cost, known physical chemistry. Against: serious eco-damage, possible membrane issues.