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1. The roofs of houses and solar cells over roads would cover the need for everything but (maybe) really high population cities. The area to collect sun isn't r

by berntb 10y ago

1. The roofs of houses and solar cells over roads would cover the need for everything but (maybe) really high population cities. The area to collect sun isn't really a problem, especially not when they get more efficient over time. 2. "and 1/5 of [solar cells?] needs replacing. Every. Single. Year." Huh? The technical life length of solar cells are much higher, as you note yourself. And certainly, solar cells are not that useful in a Scandinavian winter, because there is just not enough sun. But as it seems now, unless General Fusion or a similar fusion project works out, solar will in twenty++ years supply electricity to most people's normal energy use on the planet. (Few live up in the north.)

maxerickson 10y ago
Residential power is probably easy with solar. A mill near here uses more power than the 40,000 person county (and I think also uses the waste heat from the power plant, so the nominal electric output of the plant doesn't capture the energy required to run the mill)). Still, I think the US standard of living is unnecessarily energy intensive (cheap buildings heated/cooled more than necessary, lots of beef, vanity carburetors, it goes on and on and on so all the little things actually add up). It's pretty likely that the US can substantially reduce consumer energy use without really having any impact on standard of living.
dredmorbius 10y ago
Sorry. Five percent, not 20%. Five percent of a large number remains a fairly large number, especially if yo've got to keep it up forever. The only comparable infrastructure by size now are highways, though technically they're far less complex. Full replacement of a concrete roadbed happens every 20-50 years or so. Estimates of rooftop coverage only largely account for electrical use only, and don't account for storage or fuel synthesis, e.g., Jacobson & Delucci (Stanford / UC Davis researchers). I suspect they're optimistic. David Macay's Without the Hot Air, looking at the UK, is somewhat more subdued. Electricity is generally about 33% of energy end-use. Transport is another third, and various uses, mostly industrial and heating, the remainder. Generation would have to increase significantly to cover this. Storage would have further efficiency losses. And then there are the capital requirements.
- berntb 10y ago
  Sure, I talk about that the personal energy use will soon be a solved problem (again, except for Scandinavia et al; we are few anyway). A very high population density is 20K/km^2. That makes 50 m^2 per person in this worst case. Assume 20% of that 50 m^2 is covered with solar cells, giving 100 Watt/m^2 (1 kWatt) for 10 hours/day. Roughly what an average US individual use today (911 kwh/month for a household in US, 2.5 person in the household / Google), certainly much lower in such a highly built up area. (The previous was a back of an envelope calculation of a worst case, it would probably be more energy/capita, which would also allow for running electrical cars on solar.) The household energy storage seems to be solved, inside a decade or two (see Musk.) Especially when electrical car batteries start to be used for energy storage. I'm not claiming this will be a simple problem, but note that solar will soon reach cost parity with the existing infrastructure, as long as (free) roof area is used. Then it will be lots of people updating the solar cells on their own roofs. For heating -- build better houses. There is no need to use so much energy. High density areas with less solar m^2/person will have less heating problems (larger houses). (You'll probably never see this comment anyway, I'm hell banned. :-) )

by berntb 10y ago

maxerickson 10y ago

Residential power is probably easy with solar. A mill near here uses more power than the 40,000 person county (and I think also uses the waste heat from the power plant, so the nominal electric output of the plant doesn't capture the energy required to run the mill)). Still, I think the US standard of living is unnecessarily energy intensive (cheap buildings heated/cooled more than necessary, lots of beef, vanity carburetors, it goes on and on and on so all the little things actually add up). It's pretty likely that the US can substantially reduce consumer energy use without really having any impact on standard of living.

dredmorbius 10y ago

Sorry. Five percent, not 20%. Five percent of a large number remains a fairly large number, especially if yo've got to keep it up forever. The only comparable infrastructure by size now are highways, though technically they're far less complex. Full replacement of a concrete roadbed happens every 20-50 years or so. Estimates of rooftop coverage only largely account for electrical use only, and don't account for storage or fuel synthesis, e.g., Jacobson & Delucci (Stanford / UC Davis researchers). I suspect they're optimistic. David Macay's Without the Hot Air, looking at the UK, is somewhat more subdued. Electricity is generally about 33% of energy end-use. Transport is another third, and various uses, mostly industrial and heating, the remainder. Generation would have to increase significantly to cover this. Storage would have further efficiency losses. And then there are the capital requirements.

berntb 10y ago
Sure, I talk about that the personal energy use will soon be a solved problem (again, except for Scandinavia et al; we are few anyway). A very high population density is 20K/km^2. That makes 50 m^2 per person in this worst case. Assume 20% of that 50 m^2 is covered with solar cells, giving 100 Watt/m^2 (1 kWatt) for 10 hours/day. Roughly what an average US individual use today (911 kwh/month for a household in US, 2.5 person in the household / Google), certainly much lower in such a highly built up area. (The previous was a back of an envelope calculation of a worst case, it would probably be more energy/capita, which would also allow for running electrical cars on solar.) The household energy storage seems to be solved, inside a decade or two (see Musk.) Especially when electrical car batteries start to be used for energy storage. I'm not claiming this will be a simple problem, but note that solar will soon reach cost parity with the existing infrastructure, as long as (free) roof area is used. Then it will be lots of people updating the solar cells on their own roofs. For heating -- build better houses. There is no need to use so much energy. High density areas with less solar m^2/person will have less heating problems (larger houses). (You'll probably never see this comment anyway, I'm hell banned. :-) )