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MacKay assumed that PV modules used in large solar farms would be only 10% efficient, on the grounds that "solar panels would be mass-produced on such a scale o

MacKay assumed that PV modules used in large solar farms would be only 10% efficient, on the grounds that "solar panels would be mass-produced on such a scale only if they were very cheap, and it’s the lower-efficiency panels that will get cheap first": https://www.withouthotair.com/c6/page_41.shtml https://www.withouthotair.com/c6/page_41.shtml A lot of solar startups foundered on this same mistaken assumption that low efficiency thin film panels would be cheaper than crystalline silicon. Considering costs for cover glass, backsheets, frames, cabling, and racking, that wasn't actually true. Crystalline silicon wins both the "premium" rooftop module market and the low cost ground mounted market. Several manufacturers now offer panels for the utility market with efficiencies reaching 20%, like this one from LONGi Solar: https://en.longi-solar.com/uploads/attach/20200423/5ea0f8bb2764c.pdf https://en.longi-solar.com/uploads/attach/20200423/5ea0f8bb2... He palmed an even more significant card at the beginning of the book. Instead of starting with actual per-capita energy consumption in the UK, he estimated consumption for "a typical moderately affluent person" living in the UK: http://www.withouthotair.com/c2/page_22.shtml http://www.withouthotair.com/c2/page_22.shtml Making the whole population "moderately affluent" yields per-capita energy demand 56 percent greater than the actual value at the time the book was written (195 vs 125): https://www.withouthotair.com/c18/page_104.shtml https://www.withouthotair.com/c18/page_104.shtml I thought that MacKay was a clever but not very quiet proponent for nuclear power. His assumptions effectively nudge the reader toward the nuclear solution. Even though some of his assumptions were dubious from the first, and others have been invalidated by subsequent developments, I still love the book for its transparent analysis.

dredmorbius 6y ago
Underestimating supply and overestimating demand is good engineering esstimation practice. Surprises tend to occur in the other direction. With the shift from fossil fuels, additional electrical demand from heating, cooking, and transport demands can be expected. I'd have to re-read the book to see if MacKay accounts for these otherwise. Starting with a value for a "moderately affluent" household also builds in the prospect for a general wealth increase, and forestalls opposition based on assertions he is locking in an austere lifestyle, a commmon tactic of opponents to renewable / decarbonised energy. I haven't tracked PV efficiency trends lately, but recall generally that high teens is fairly typical. A vendor page supports this: The highest efficiency solar panels on the market today can reach almost 23 percent efficiency. The average efficiency of solar panels falls between the 17 to 19 percent efficiency range. https://www.solar.com/learn/solar-panel-efficiency/ https://www.solar.com/learn/solar-panel-efficiency/ For single-layer panels, the maximum theoretical efficiency (never practically obtained) is 37%. Far more expensive multi-layer panels peak at ~85%, and in practice, results are well below 50%. Dual-mode (PV-thermal) systems offer greater net capabilities, though the thermal output is limited to low-grade heat, e.g. hot-water pre-heat or seasonal thermal storage as with Passivhaus. Not inconsequential, but not makjickal pykxsie duste either. An effective 10% efficiency net of shading, spacing factors, degradation, dirt, inverter losses, and other factors is quite reasonable. MacKay's nuclear advocacy is remarkably sober and low-key in a world where proponents freqquently tend to be strident and shrill. I am not a fan of the technology (and take it you aren't either), but his portrayal is a realistic and respectful one. Apologies for misspelling MacKay's name repeatedly above. HN's limited edit window is annoying.
- philipkglass 6y ago
  I don't think that he was just lumping parameters together to get an "effective" 10% for ground mount PV. He allows a full 20% for rooftop PV. He just didn't realize that both would converge toward similar technology and efficiency. Nuclear is fine as far as the physics goes. It's the inability to hold to projected budgets and schedules that has sidelined it. Betting big on nuclear was much more reasonable in 2007 when the book came out. At the time I certainly thought that the UK would add more TWh from nuclear than from renewables by 2020.

dredmorbius 6y ago

Underestimating supply and overestimating demand is good engineering esstimation practice. Surprises tend to occur in the other direction. With the shift from fossil fuels, additional electrical demand from heating, cooking, and transport demands can be expected. I'd have to re-read the book to see if MacKay accounts for these otherwise. Starting with a value for a "moderately affluent" household also builds in the prospect for a general wealth increase, and forestalls opposition based on assertions he is locking in an austere lifestyle, a commmon tactic of opponents to renewable / decarbonised energy. I haven't tracked PV efficiency trends lately, but recall generally that high teens is fairly typical. A vendor page supports this: The highest efficiency solar panels on the market today can reach almost 23 percent efficiency. The average efficiency of solar panels falls between the 17 to 19 percent efficiency range. https://www.solar.com/learn/solar-panel-efficiency/ https://www.solar.com/learn/solar-panel-efficiency/ For single-layer panels, the maximum theoretical efficiency (never practically obtained) is 37%. Far more expensive multi-layer panels peak at ~85%, and in practice, results are well below 50%. Dual-mode (PV-thermal) systems offer greater net capabilities, though the thermal output is limited to low-grade heat, e.g. hot-water pre-heat or seasonal thermal storage as with Passivhaus. Not inconsequential, but not makjickal pykxsie duste either. An effective 10% efficiency net of shading, spacing factors, degradation, dirt, inverter losses, and other factors is quite reasonable. MacKay's nuclear advocacy is remarkably sober and low-key in a world where proponents freqquently tend to be strident and shrill. I am not a fan of the technology (and take it you aren't either), but his portrayal is a realistic and respectful one. Apologies for misspelling MacKay's name repeatedly above. HN's limited edit window is annoying.

philipkglass 6y ago
I don't think that he was just lumping parameters together to get an "effective" 10% for ground mount PV. He allows a full 20% for rooftop PV. He just didn't realize that both would converge toward similar technology and efficiency. Nuclear is fine as far as the physics goes. It's the inability to hold to projected budgets and schedules that has sidelined it. Betting big on nuclear was much more reasonable in 2007 when the book came out. At the time I certainly thought that the UK would add more TWh from nuclear than from renewables by 2020.