3 ms·

I would like to see the numbers; how much overbuilding would be necessary. Even if you need to install say 50%-100% extra capacity to meet demand in winter, sol

by tda 6y ago

I would like to see the numbers; how much overbuilding would be necessary. Even if you need to install say 50%-100% extra capacity to meet demand in winter, solar power would still be perfectly economically viable. And I'm sure a valid use for excess power in summer can be found, e.g. desalination. Fresh water demand is surely higher in summer in the Sahara, and otherwise fresh water is easily stored

stdbrouw 6y ago
I looked up the numbers for Aswan in the south of Egypt. Roughly 360 hours of sunshine or a bit more in the summer, 290 hours in winter months [1], so about 80% of max. If we look at direct normal irradiance instead, a more appropriate metric, it varies between 7.93 kWh/m^2/day in June vs. 5.51 kWh/m^2/day in December [2], so about 70% of max. Hour-to-hour and day-to-day fluctuations are another thing altogether, and higher demand in winter (e.g. for heating) yet another consideration, but if we're purely interested in some sort of "seasonal correction" I guess you'd want to overbuild by 40% or a bit less if you set the angle of the panels in such a way as to optimize winter production at the expense of summer production, a common strategy. The closer you get to the equator, the less it matters whether you're in the northern hemisphere or the southern hemisphere. Aswan is at 24°N, a latitude at which you can still find a lot of smaller cities, but as you go to the south of that, infrastructure disappears and it might not be economical to build PV or solar thermal installations in the absolute middle of nowhere. Seems to be about the latitude to which DESERTEC proposes to lay HDVC connections. Not an expert though, just someone who can look up some numbers. [1] https://en.wikipedia.org/wiki/Aswan https://en.wikipedia.org/wiki/Aswan [2] https://www.researchgate.net/figure/Average-Direct-normal-irradiance-of-Aswan-Egypt_fig3_324538284 https://www.researchgate.net/figure/Average-Direct-normal-ir...

by tda 6y ago

stdbrouw 6y ago

I looked up the numbers for Aswan in the south of Egypt. Roughly 360 hours of sunshine or a bit more in the summer, 290 hours in winter months [1], so about 80% of max. If we look at direct normal irradiance instead, a more appropriate metric, it varies between 7.93 kWh/m^2/day in June vs. 5.51 kWh/m^2/day in December [2], so about 70% of max. Hour-to-hour and day-to-day fluctuations are another thing altogether, and higher demand in winter (e.g. for heating) yet another consideration, but if we're purely interested in some sort of "seasonal correction" I guess you'd want to overbuild by 40% or a bit less if you set the angle of the panels in such a way as to optimize winter production at the expense of summer production, a common strategy. The closer you get to the equator, the less it matters whether you're in the northern hemisphere or the southern hemisphere. Aswan is at 24°N, a latitude at which you can still find a lot of smaller cities, but as you go to the south of that, infrastructure disappears and it might not be economical to build PV or solar thermal installations in the absolute middle of nowhere. Seems to be about the latitude to which DESERTEC proposes to lay HDVC connections. Not an expert though, just someone who can look up some numbers. [1] https://en.wikipedia.org/wiki/Aswan https://en.wikipedia.org/wiki/Aswan [2] https://www.researchgate.net/figure/Average-Direct-normal-irradiance-of-Aswan-Egypt_fig3_324538284 https://www.researchgate.net/figure/Average-Direct-normal-ir...