Thanks, Gene for the terrific analysis. Let's say that RO requires 5 kWh/m^3. 'A typical "150 watt" solar module is about a square meter in size. Such a module may be expected to produce 0.75 kWh every day, on average, after taking into account the weather and the latitude, for an insolation of 5 sun hours/day.' http://en.wikipedia.org/wiki/Photovoltaic_system 1 cubic meter = 264.172052 US gallons Each person requires ~ 50 gallons = ~1/5 m^3 of water per day, or about 1kWh per day for energy for desalinization. So each person requires about 2 m^2 = ~21 sqft (~ size of a large 3'x7' bed) of solar cells just to power his/her desalinization needs. Clearly, there is more than enough roof area on most (California) homes to provide enough power to desalinize the water for its occupants. So even if we're off by a factor of 2-4x, this is still reasonable. So perhaps the answer is piping seawater to people's homes and doing distributed desalinization? At 06:40 PM 4/22/2015, Eugene Salamin via math-fun wrote:
According to [ http://en.wikipedia.org/wiki/Desalination ], reverse osmosis requires 3-5.5 kWh/m^3, just for the reverse osmoses, and excluding the energy needed to operate the facility.