4 ms·

While I'm generally pro-solar, more workers is not an inherent good with an energy source... quite the opposite. The idea of energy is to require as few workers

by api 12y ago

While I'm generally pro-solar, more workers is not an inherent good with an energy source... quite the opposite. The idea of energy is to require as few workers as possible so that human attention and labor can be spent on other things. This is likely directly related to the fact that coal has a higher EROEI than solar (neglecting long-term externalities of course).

dredmorbius 12y ago
Higher EROEI and much more concentrated capital. For every square meter of PV deployed, you start with 1 kW of incident sunlight, reduced by the panel efficiency (~15%), capacity factor (~25%), the shading/spacing factor (~55%), and inverter efficiency (~90%). Your panels have a nominal life of 20 years after which they must be replaced. On a square-meter basis, the raw output of a coal-fired plant is vastly higher. That footprint is extended by mining operations, fuel transport (mostly railroad), and tailings and ash disposal. It's still pretty high. That said, I'd prefer to see approaches to increasing solar worker efficiency rather than prolonging use of coal.
- gizmo686 12y ago
  Solar panals also use their land area much less invasivly. You can stick them on the roofs of building which would otherwise be unused space. Coal power plants do not share space nearly as well. Of course, coal mining may actually make more usable space but I would prefer to keep such space in its natural state until we actually want to use it.
  - dredmorbius 12y ago
    Right. That's a concern for land use which I address in another follow-up on this thread. What I'm focusing on though are the costs of plant capital involved in energy production, and the relative productivity of that capital. Coal plants approach 500x the energy intensity of solar power.
- reportingsjr 12y ago
  I don't see why a power output per square meter metric would be worth comparing. The amount of space solar takes up shouldn't really matter that much. I do believe that solar farms are a pretty bad idea and panels should be put on roof tops more than anywhere else. Roof top solar solves more problems than farms. It helps keep roofs cooler during summer which can help reduce the heat island effect. It also doesn't take up space that is becoming more precious all of the time.
  - dredmorbius 12y ago
    Because that square meter represents capital infrastructure which must be built, maintained, integrated into the grid (inverters, transmission lines), and eventually replaced and updated. Again, don't get me wrong: I think there's absolutely no question that our future will rely primarily on renewable and sustainable energy sources. The question to me isn't whether this will be the case, but if it will be a high-tech renewable energy infrastructure (with electricity, grids, etc.) or low-tech: farms, grains, and draught animals. The costs of renewable energy strike me as vastly higher than most of the general public seems to think. You'll get fossil-fuel fans arguing this as a reason that renewables aren't viable. I think that's a misplaced argument of a legitimate concern: it's whether or not a technological civilization is viable. I don't know one way or the other. I think we're skating really, really close to the edge. Erik Lindberg's recent Resiliance / Transition Milwaukee piece, "Six Myths About Climate Change that Liberals Rarely Question", lays out most of these factors: http://www.resilience.org/stories/2014-11-26/six-myths-about-climate-change-that-liberals-rarely-question http://www.resilience.org/stories/2014-11-26/six-myths-about... Back to that output area. If I'm reading EIA's capacity data correctly, there are about 313 GW of installed coal generating capacity in the US. Let's double that on a basis of capacity factor, plant maintenance, and other factors. http://www.eia.gov/electricity/capacity/ http://www.eia.gov/electricity/capacity/ (Stealth edit: and another source confirms 557 coal plants as of 2012. http://www.eia.gov/electricity/annual/html/epa_04_01.html http://www.eia.gov/electricity/annual/html/epa_04_01.html ) GRIST, an environmental site, allows for one square mile (640 acres) for a nominal 1 GW power plant. So we're talking about a maximum of around 600 square miles dedicated to coal plant capital itself. That's a region 24.5 miles on a side. http://grist.org/article/2010-11-17-which-has-bigger-footprint-coal-plant-or-solar-farm/ http://grist.org/article/2010-11-17-which-has-bigger-footpri... And note that I'm not talking about total land-use footprint: coal storage, transport, mining, and disposal all have footprints, and they're substantial. But most of them are also pretty non-technical -- a mine, after all, is for the most part a hole in the ground, not a machine. But of that square mile, the bulk of it isn't actually technical infrastructure. An Indian engineering report puts the main plant at 4.6% of total land area for a 5 x 800 MW plant, 92 acres. That's 43.4 MW/acre. Which means that of the 600 square miles devoted to coal power plant siting, only 11.25 mi^2 of that is actually coal plant itself -- the rest is (mostly) much less technical land use. http://www.cea.nic.in/reports/land_review_report.pdf http://www.cea.nic.in/reports/land_review_report.pdf By comparison, with a nominal 1 kW/m^2 of incident sunlight, you're starting with 4 MW/acre available energy. By the time you apply PV efficiency (15%), spacing factor (55%), capacity factor (30%), and inverter efficiency, you're down to 0.09 MW/acre delivered energy. You'll need 477 acres of solar infrastructure to provide the same output as a single acre of coal plant. GNU units is handy for calculating various factors, and we can compute how much area needs to be dedicated to an equivalent amount of solar generating capacity: You have: 313 GW / (1 kW/m^2 * 0.15 * 0.55 * 0.3 * 0.9) You want: mile^2 * 5425.3637 / 0.00018431944 That is: we'd need 5,425 square miles, or a region 73 miles on a side. (Note I've omitted considerations such as storage or other factors -- this analysis is favorable to solar power.) There are a lot of other factors you can consider. Coal plants generally don't do well sited immediately adjacent to other land uses: agriculture, residential, commercial, or even industrial. You can park solar panels on top of pretty much anything -- they're nonrivalrous for much human activity (though they compete with ag for access to sunlight). That's not what I'm considering. But even with that, you've got to provide: ⚫ Mounting / foundation structures. ⚫ Panels themselves. ⚫ Rectifiers. ⚫ Grid interconnects. All of those represent installation costs. Once installed, there is some maintenance required as well. I don't have good cost data on this, or labor requirements. But if nothing else, someone's got to move through the installation, and area means distance means time. If you want to go further with solar power and allow for excess capacity to provide for storage, fuel synthesis (I suspect that's going to be part of the equation), and substitution for other energy uses (e.g., not just present electrical consumption), then you're talking land-use that's hundreds of miles on a side for the US alone. This would be a substantial portion of a large state (say: Nevada, Arizona, New Mexico, Utah, etc.). Yes, the land use can be broken up and distributed across other states, but you simply cannot get away from the fact that it's a lot of area, and that you're parking a highly technical infrastructure on it. And if you think this is a pessimistic analysis, try calculating land-use requirements for biofuels given per-acre productions of 30-300 gallons/acre-year for typical oil crops (corn, canola, hemp), and 6.75 billion barrels of present US annual oil consumption. There are about 409 million acres of arable land in the U.S., and 2,379 million acres total. Try it yourself with GNU units or Wolfram+Alpha.
- Omniusaspirer 12y ago
  Isn't 20 years considered the bare minimum for solar panels (with a good warranty lasting that long)? They sure as hell aren't useless automatically around that point- the peak output has certainly degraded but not to the point where you couldn't easily continue using them for 5, 10, or even 20+ more years.
  - dredmorbius 12y ago
    No, that's a nominal mean lifetime. Panels degrade at ~0.5 - 0.8% per year (for various reasons), and are considered candidates for replacement when they've deteriorate to 80% of rated capacity. See the NREL study referenced elsewhere in this thread. I do suspect that extending the life of solar plant may well help reduce total costs.
    - sokoloff 12y ago
      Omni's point is that they are "considered candidates for replacement" by companies with a vested interest in selling you replacements. I'm sure that car makers consider a 3 year old car a "candidate for replacement" as well. Doesn't make it worthless or not worthy of continuing to run rather than investing in replacing...
- vacri 12y ago
  I can't stick a coal mine on my roof, though. Panel replacement also seems to be a constant concern in these discussions, implying that mining equipment is free and indestructible, and that coal plants never need retirement or refurb.
  - dredmorbius 12y ago
    Solar infrastructure is exposed to the elements and is subject to various forms of damage: wind, hail, storms, debris, vandalism, theft. These need to be considered or mitigated.
    - Someone 12y ago
      Yes, and coal mining equipment is kept in air-conditioned rooms and carefully kept in pristine condition by people wearing silk handkerchiefs?
      - dredmorbius 12y ago
        Coal mines are typically controlled-access sites. Also frequently not located in residential / commercial areas. Which cuts down on theft. Most of the equipment used in mining is, of necessity, pretty heavy-duty. PV panels are constructed of silicon, glass, and electronics. None of which are particularly known for being as rugged as, say, 3/8" steel plate. There's also a lot of it, it is and has to be exposed to open air. Find yourself in a high-wind situation -- storm gusts of 40 - 80 MPH aren't uncommon, tornado or hurricane conditions can see wind speeds of 100 - 500 MPH. Yes, as a matter of fact, things get damaged from time to time. Add to that the fact that you've got from thousands to tens of thousands of square miles of deployed infrastructure, and security also becomes a significant issue. There are copper thieves as things stand now. A rooftop full of PV can be several tens of thousands of dollars of capital.
crdoconnor 12y ago
>While I'm generally pro-solar, more workers is not an inherent good with an energy source... quite the opposite. The idea of energy is to require as few workers as possible so that human attention and labor can be spent on other things. Because the country has a massive overemployment problem right now?

by api 12y ago

dredmorbius 12y ago

Higher EROEI and much more concentrated capital. For every square meter of PV deployed, you start with 1 kW of incident sunlight, reduced by the panel efficiency (~15%), capacity factor (~25%), the shading/spacing factor (~55%), and inverter efficiency (~90%). Your panels have a nominal life of 20 years after which they must be replaced. On a square-meter basis, the raw output of a coal-fired plant is vastly higher. That footprint is extended by mining operations, fuel transport (mostly railroad), and tailings and ash disposal. It's still pretty high. That said, I'd prefer to see approaches to increasing solar worker efficiency rather than prolonging use of coal.

gizmo686 12y ago
Solar panals also use their land area much less invasivly. You can stick them on the roofs of building which would otherwise be unused space. Coal power plants do not share space nearly as well. Of course, coal mining may actually make more usable space but I would prefer to keep such space in its natural state until we actually want to use it.
- dredmorbius 12y ago
  Right. That's a concern for land use which I address in another follow-up on this thread. What I'm focusing on though are the costs of plant capital involved in energy production, and the relative productivity of that capital. Coal plants approach 500x the energy intensity of solar power.
reportingsjr 12y ago
I don't see why a power output per square meter metric would be worth comparing. The amount of space solar takes up shouldn't really matter that much. I do believe that solar farms are a pretty bad idea and panels should be put on roof tops more than anywhere else. Roof top solar solves more problems than farms. It helps keep roofs cooler during summer which can help reduce the heat island effect. It also doesn't take up space that is becoming more precious all of the time.
- dredmorbius 12y ago
  Because that square meter represents capital infrastructure which must be built, maintained, integrated into the grid (inverters, transmission lines), and eventually replaced and updated. Again, don't get me wrong: I think there's absolutely no question that our future will rely primarily on renewable and sustainable energy sources. The question to me isn't whether this will be the case, but if it will be a high-tech renewable energy infrastructure (with electricity, grids, etc.) or low-tech: farms, grains, and draught animals. The costs of renewable energy strike me as vastly higher than most of the general public seems to think. You'll get fossil-fuel fans arguing this as a reason that renewables aren't viable. I think that's a misplaced argument of a legitimate concern: it's whether or not a technological civilization is viable. I don't know one way or the other. I think we're skating really, really close to the edge. Erik Lindberg's recent Resiliance / Transition Milwaukee piece, "Six Myths About Climate Change that Liberals Rarely Question", lays out most of these factors: http://www.resilience.org/stories/2014-11-26/six-myths-about-climate-change-that-liberals-rarely-question http://www.resilience.org/stories/2014-11-26/six-myths-about... Back to that output area. If I'm reading EIA's capacity data correctly, there are about 313 GW of installed coal generating capacity in the US. Let's double that on a basis of capacity factor, plant maintenance, and other factors. http://www.eia.gov/electricity/capacity/ http://www.eia.gov/electricity/capacity/ (Stealth edit: and another source confirms 557 coal plants as of 2012. http://www.eia.gov/electricity/annual/html/epa_04_01.html http://www.eia.gov/electricity/annual/html/epa_04_01.html ) GRIST, an environmental site, allows for one square mile (640 acres) for a nominal 1 GW power plant. So we're talking about a maximum of around 600 square miles dedicated to coal plant capital itself. That's a region 24.5 miles on a side. http://grist.org/article/2010-11-17-which-has-bigger-footprint-coal-plant-or-solar-farm/ http://grist.org/article/2010-11-17-which-has-bigger-footpri... And note that I'm not talking about total land-use footprint: coal storage, transport, mining, and disposal all have footprints, and they're substantial. But most of them are also pretty non-technical -- a mine, after all, is for the most part a hole in the ground, not a machine. But of that square mile, the bulk of it isn't actually technical infrastructure. An Indian engineering report puts the main plant at 4.6% of total land area for a 5 x 800 MW plant, 92 acres. That's 43.4 MW/acre. Which means that of the 600 square miles devoted to coal power plant siting, only 11.25 mi^2 of that is actually coal plant itself -- the rest is (mostly) much less technical land use. http://www.cea.nic.in/reports/land_review_report.pdf http://www.cea.nic.in/reports/land_review_report.pdf By comparison, with a nominal 1 kW/m^2 of incident sunlight, you're starting with 4 MW/acre available energy. By the time you apply PV efficiency (15%), spacing factor (55%), capacity factor (30%), and inverter efficiency, you're down to 0.09 MW/acre delivered energy. You'll need 477 acres of solar infrastructure to provide the same output as a single acre of coal plant. GNU units is handy for calculating various factors, and we can compute how much area needs to be dedicated to an equivalent amount of solar generating capacity: You have: 313 GW / (1 kW/m^2 * 0.15 * 0.55 * 0.3 * 0.9) You want: mile^2 * 5425.3637 / 0.00018431944 That is: we'd need 5,425 square miles, or a region 73 miles on a side. (Note I've omitted considerations such as storage or other factors -- this analysis is favorable to solar power.) There are a lot of other factors you can consider. Coal plants generally don't do well sited immediately adjacent to other land uses: agriculture, residential, commercial, or even industrial. You can park solar panels on top of pretty much anything -- they're nonrivalrous for much human activity (though they compete with ag for access to sunlight). That's not what I'm considering. But even with that, you've got to provide: ⚫ Mounting / foundation structures. ⚫ Panels themselves. ⚫ Rectifiers. ⚫ Grid interconnects. All of those represent installation costs. Once installed, there is some maintenance required as well. I don't have good cost data on this, or labor requirements. But if nothing else, someone's got to move through the installation, and area means distance means time. If you want to go further with solar power and allow for excess capacity to provide for storage, fuel synthesis (I suspect that's going to be part of the equation), and substitution for other energy uses (e.g., not just present electrical consumption), then you're talking land-use that's hundreds of miles on a side for the US alone. This would be a substantial portion of a large state (say: Nevada, Arizona, New Mexico, Utah, etc.). Yes, the land use can be broken up and distributed across other states, but you simply cannot get away from the fact that it's a lot of area, and that you're parking a highly technical infrastructure on it. And if you think this is a pessimistic analysis, try calculating land-use requirements for biofuels given per-acre productions of 30-300 gallons/acre-year for typical oil crops (corn, canola, hemp), and 6.75 billion barrels of present US annual oil consumption. There are about 409 million acres of arable land in the U.S., and 2,379 million acres total. Try it yourself with GNU units or Wolfram+Alpha.
Omniusaspirer 12y ago
Isn't 20 years considered the bare minimum for solar panels (with a good warranty lasting that long)? They sure as hell aren't useless automatically around that point- the peak output has certainly degraded but not to the point where you couldn't easily continue using them for 5, 10, or even 20+ more years.
- dredmorbius 12y ago
  No, that's a nominal mean lifetime. Panels degrade at ~0.5 - 0.8% per year (for various reasons), and are considered candidates for replacement when they've deteriorate to 80% of rated capacity. See the NREL study referenced elsewhere in this thread. I do suspect that extending the life of solar plant may well help reduce total costs.
  - sokoloff 12y ago
    Omni's point is that they are "considered candidates for replacement" by companies with a vested interest in selling you replacements. I'm sure that car makers consider a 3 year old car a "candidate for replacement" as well. Doesn't make it worthless or not worthy of continuing to run rather than investing in replacing...
vacri 12y ago
I can't stick a coal mine on my roof, though. Panel replacement also seems to be a constant concern in these discussions, implying that mining equipment is free and indestructible, and that coal plants never need retirement or refurb.
- dredmorbius 12y ago
  Solar infrastructure is exposed to the elements and is subject to various forms of damage: wind, hail, storms, debris, vandalism, theft. These need to be considered or mitigated.
  - Someone 12y ago
    Yes, and coal mining equipment is kept in air-conditioned rooms and carefully kept in pristine condition by people wearing silk handkerchiefs?
    - dredmorbius 12y ago
      Coal mines are typically controlled-access sites. Also frequently not located in residential / commercial areas. Which cuts down on theft. Most of the equipment used in mining is, of necessity, pretty heavy-duty. PV panels are constructed of silicon, glass, and electronics. None of which are particularly known for being as rugged as, say, 3/8" steel plate. There's also a lot of it, it is and has to be exposed to open air. Find yourself in a high-wind situation -- storm gusts of 40 - 80 MPH aren't uncommon, tornado or hurricane conditions can see wind speeds of 100 - 500 MPH. Yes, as a matter of fact, things get damaged from time to time. Add to that the fact that you've got from thousands to tens of thousands of square miles of deployed infrastructure, and security also becomes a significant issue. There are copper thieves as things stand now. A rooftop full of PV can be several tens of thousands of dollars of capital.

crdoconnor 12y ago

>While I'm generally pro-solar, more workers is not an inherent good with an energy source... quite the opposite. The idea of energy is to require as few workers as possible so that human attention and labor can be spent on other things. Because the country has a massive overemployment problem right now?