4 ms·
He's completely neglected the energy costs of pumping all that water uphill, which I think may be significant. If we take that 876 million cubic metres of wate
by m_dupont 4y ago
He's completely neglected the energy costs of pumping all that water uphill, which I think may be significant.
If we take that 876 million cubic metres of water from his example and pump it to, say, lake mead (also in his example), the total change in gravtiatonal energy is
m = 876 10^6 m3 water = 876 10^9 kg
g = 9.81
h = 375m lake mead
mgh = 3.22 10^ 15 J = 895 GWh
If my calculations are correct, the energy cost of pumping the water exceeds the cost of desalination by far. Now obviously IRL all that water wouldn't go to lake mead but a back of the envelope calculation shows that the water pumping costs shouldn’t be ignored.
It would probably be better to use desal for providing coastal cities with 100% of their water and simply reducing the amount that we pull out of the rivers in the first place
- thehappypm 4y agoThe article includes pumping costs
- m_dupont 4y agoI reread the article just then and while he does indeed mention that pumping can be done "easily" he never calculates the energy cost associated with it. In the 5th paragraph of the section titled "what?" He says that "even including pumping and 25% solar utilization, just 20,000 acres of solar panels ... would be adequate to power 100% of arizonas imported water", but he doesn't actually derive that figure. He doesnt calculate the pumping costs. So yes, I think its fair to say that he neglected pumping costs
- stevep98 4y agoYou’d recover some of the energy as it passes through the Hoover dam. In fact this proposal has the side benefit of storing energy from solar.