4 ms·

"Renewable" doesn't mean "free energy". Constructing renewable energy sources (wind, solar, etc) takes more energy than constructing an equivalent non-renewable

by ppf 8y ago

"Renewable" doesn't mean "free energy". Constructing renewable energy sources (wind, solar, etc) takes more energy than constructing an equivalent non-renewable energy source - this is the EROEI (energy returned on energy invested). There's also space limits - see https://www.youtube.com/watch?v=E0W1ZZYIV8o https://www.youtube.com/watch?v=E0W1ZZYIV8o What's apparent to me is that we live in a unique era where energy is abundant and cheap, which may never be repeated (unless fusion power is developed).

nostrademons 8y ago
His conclusions seemed suspect to me - I remember doing out the calculations myself and came out with the conclusion that a 50x50 mile solar array in the Arizona desert could power the U.S. A 150x200 mile array in the Sahara could power the world. These are large arrays - they would be visible from space - but they are far from "country-sized", and quite doable if production costs come down (which they are - solar and wind are now cheaper than coal). (You can check my math yourself: total world energy consumption = 109,136 TWh [1] / 8760 hours/year = 12.45 TW / 15 W/foot solar panel output [2] = 830B square feet / 27878400 ft^2/mi^2 = 29772 mi^2 = 150x200 mi array.) Working through his math, I think the problem is that the UK is unique in a.) having a high population density b.) with a large per capita energy consumption and c.) a lot of cloud cover. On his chart, only Japan, South Korea, the Netherlands, and Bahrain had it worse. The U.S. and China both had an order-of-magnitude better energy consumption per unit area; most of the world had two orders of magnitude. That's an argument for why Britain is fucked in the new globally-warmed, fossil-fuel-limited world, but not why the world is fucked. A lot of developing areas could see their energy consumption rise to rival the U.S. and still not bat an eye with solar power. The EROEI of solar panels is between 8.7 - 34.2; wind is 20-50. [3] As long as this number is > 1 (which it is for nearly every energy source except biofuels) you can keep building production capacity indefinitely; you just invest the energy from previous capacity into building new capacity. Higher numbers of course let you do more other stuff while this is going on and build out faster, but it's just like capitalism. As long as you turn a profit on each panel, you'll have more as time goes on. [1] https://en.wikipedia.org/wiki/World_energy_consumption https://en.wikipedia.org/wiki/World_energy_consumption [2] https://www.solarpowerrocks.com/solar-basics/how-much-electricity-does-a-solar-panel-produce/ https://www.solarpowerrocks.com/solar-basics/how-much-electr... [3] https://en.wikipedia.org/wiki/Energy_returned_on_energy_invested#Photovoltaic https://en.wikipedia.org/wiki/Energy_returned_on_energy_inve...
- ppf 8y ago
  Your figure of 15W/sq foot assumes no gaps between panels - hard to imagine on a 50mile+ array. The bigger problem is that it assumes overhead, direct sunlight. You'd have to cut that at least in half ;) Yes, the UK does have issues by these metrics, and the US is in the unique position of a huge per capita energy consumption and huge land reserves. Therefore, it is somewhat feasible in the US to just keep building wind and solar farms. However, I wonder how the economics of the non-renewable minerals needed would affect the price. It also doesn't (as far as I know) take into account all the extra infrastructure required to support the fluctuating nature of renewable energy sources.
  - ppf 8y ago
    Also, with a higher cost to manufacture these energy sources, it's inevitable that the cost to consumers will rise.
    - nostrademons 8y ago
      The gaps easily get canceled out by using newer solar panels; I took the low end of commercial solar power outputs I found on the web, many of the more recent ones do 20W/sq foot or more. 25% gaps seems generous. I thought about the rare-earth issue, but there's a simple solution that bypasses both it and the energy-storage issue: use solar-thermal plants instead of photovoltaics. These require only mirrors and steam turbines, both made out of abundant materials. Efficiency is actually higher than photovoltaics (30% or so), and energy can be stored as heat for up to 5 hours before it's used. (Ironically, they have the same issues relative to photovoltaics that photovoltaics have over fossil fuels; in theory they're simpler and more environmentally friendly, but implementing the theory correctly requires solving a number of engineering problems that together make them cost more and generate more hiccups than photovoltaics have.) The higher cost isn't actually true anymore, for photovoltaics and wind at least. Solar hit grid parity with fossil fuels in late 2015, and is now actually cheaper than coal power plants. This (rather than subsidies) is why the coal industry is in deep shit: it just doesn't make economic sense anymore, and the electric industry is rapidly switching over to renewables & natural gas.

by ppf 8y ago

nostrademons 8y ago

His conclusions seemed suspect to me - I remember doing out the calculations myself and came out with the conclusion that a 50x50 mile solar array in the Arizona desert could power the U.S. A 150x200 mile array in the Sahara could power the world. These are large arrays - they would be visible from space - but they are far from "country-sized", and quite doable if production costs come down (which they are - solar and wind are now cheaper than coal). (You can check my math yourself: total world energy consumption = 109,136 TWh [1] / 8760 hours/year = 12.45 TW / 15 W/foot solar panel output [2] = 830B square feet / 27878400 ft^2/mi^2 = 29772 mi^2 = 150x200 mi array.) Working through his math, I think the problem is that the UK is unique in a.) having a high population density b.) with a large per capita energy consumption and c.) a lot of cloud cover. On his chart, only Japan, South Korea, the Netherlands, and Bahrain had it worse. The U.S. and China both had an order-of-magnitude better energy consumption per unit area; most of the world had two orders of magnitude. That's an argument for why Britain is fucked in the new globally-warmed, fossil-fuel-limited world, but not why the world is fucked. A lot of developing areas could see their energy consumption rise to rival the U.S. and still not bat an eye with solar power. The EROEI of solar panels is between 8.7 - 34.2; wind is 20-50. [3] As long as this number is > 1 (which it is for nearly every energy source except biofuels) you can keep building production capacity indefinitely; you just invest the energy from previous capacity into building new capacity. Higher numbers of course let you do more other stuff while this is going on and build out faster, but it's just like capitalism. As long as you turn a profit on each panel, you'll have more as time goes on. [1] https://en.wikipedia.org/wiki/World_energy_consumption https://en.wikipedia.org/wiki/World_energy_consumption [2] https://www.solarpowerrocks.com/solar-basics/how-much-electricity-does-a-solar-panel-produce/ https://www.solarpowerrocks.com/solar-basics/how-much-electr... [3] https://en.wikipedia.org/wiki/Energy_returned_on_energy_invested#Photovoltaic https://en.wikipedia.org/wiki/Energy_returned_on_energy_inve...

ppf 8y ago
Your figure of 15W/sq foot assumes no gaps between panels - hard to imagine on a 50mile+ array. The bigger problem is that it assumes overhead, direct sunlight. You'd have to cut that at least in half ;) Yes, the UK does have issues by these metrics, and the US is in the unique position of a huge per capita energy consumption and huge land reserves. Therefore, it is somewhat feasible in the US to just keep building wind and solar farms. However, I wonder how the economics of the non-renewable minerals needed would affect the price. It also doesn't (as far as I know) take into account all the extra infrastructure required to support the fluctuating nature of renewable energy sources.
- ppf 8y ago
  Also, with a higher cost to manufacture these energy sources, it's inevitable that the cost to consumers will rise.
  - nostrademons 8y ago
    The gaps easily get canceled out by using newer solar panels; I took the low end of commercial solar power outputs I found on the web, many of the more recent ones do 20W/sq foot or more. 25% gaps seems generous. I thought about the rare-earth issue, but there's a simple solution that bypasses both it and the energy-storage issue: use solar-thermal plants instead of photovoltaics. These require only mirrors and steam turbines, both made out of abundant materials. Efficiency is actually higher than photovoltaics (30% or so), and energy can be stored as heat for up to 5 hours before it's used. (Ironically, they have the same issues relative to photovoltaics that photovoltaics have over fossil fuels; in theory they're simpler and more environmentally friendly, but implementing the theory correctly requires solving a number of engineering problems that together make them cost more and generate more hiccups than photovoltaics have.) The higher cost isn't actually true anymore, for photovoltaics and wind at least. Solar hit grid parity with fossil fuels in late 2015, and is now actually cheaper than coal power plants. This (rather than subsidies) is why the coal industry is in deep shit: it just doesn't make economic sense anymore, and the electric industry is rapidly switching over to renewables & natural gas.