4 ms·

Every time I read of these, my thought was always "how do they get light?". I just assumed that this was somehow solved, otherwise why would everyone be so exc

Every time I read of these, my thought was always "how do they get light?". I just assumed that this was somehow solved, otherwise why would everyone be so excited about it? I figured some day I would have some time to properly investigate it and find some cool tech. It saddens me greatly, and in numerous ways, to find out that "How do they get light?" is a killer question.

quantumhobbit 16y ago
I always assumed that the light would be artificial. And that they were relying on hypothetical cheap energy of the kind that reliable fusion would provide. This may be possible a hundred years from now but surely not in today's energy economy.
- mhd 16y ago
  But once you've got reasonably cheap and plentiful energy, what's the big incentive for growing locally. If trucking it from Kansas to NYC doesn't pollute as much, reasons for building those towers diminish somewhat. Of course, it's slightly different if you've got plentiful energy, but no good way to transmit/store it. Lots of solar panels all over the city to power its greenhouses. Or windmills in Chicago.
1053r 16y ago
Production prices for solar energy are now below $0.80 / watt (http://www.123jump.com/market-update/First-Solar,-Inc-Q4-Earnings-Call-Transcript/36717/ http://www.123jump.com/market-update/First-Solar,-Inc-Q4-Ear...), although skyrocketing demand has caused wholesale prices to remain much higher. It seems likely that we may in the next 10 years be in a place where we can turn sunlight into electricity, and then electricity into the exact wavelengths of light used in photosynthesis more efficiently than allowing the plants to sit in the sun. If this is the case, than we may be able to grow crops more efficiently indoors than out. But we will be replacing acres of crops with acres of solar panels. And it's unclear to me why we would want these buildings to be skyscrapers, which are much more expensive per square foot than large warehouses in the middle of nowhere.
- ars 16y ago
  How in the world did you get +8 mod on this? That's utter nonsense! You can only get as much light as you have surface area - so now instead of fields of crops, you have fields of solar collectors! Did you think there was some magical light multiplier device that could give you more output light than you started with? Plants already use the best parts of the visible spectrum to collect light. The small amounts of infra-red you might barely be able to collect and frequency up-convert are not worthwhile - especially since you'd need to throw away all the energy from the higher frequencies in order to get it. Solar cells are terrible as far as efficiency is concerned - and not because of engineering, because that's simply how they work. (Unless you want a multijunction solar cell but those are very very expensive.) And for engineering challenges there simply doesn't exist in the world enough rare earth elements to make enough solar cells for everyone - and that's just for regular electrical usage, forget about growing plants. We do have enough silicon, but silicon based solar cells have poor efficiency.
  - DougWebb 16y ago
    I think the idea here is that plants need a narrow set of frequencies and throw the rest away. If solar cells could capture the frequencies plants don't use, convert them to energy, then convert the energy to frequencies plants like, you've increased the efficency of your light-collection area. You'll also have a garden full of black plants, which is both creepy and cool.
    - ars 16y ago
      Solar cells work the same way: they capture a narrow frequency, and throw the rest away. More accurately, below the frequency cutoff they ignore the light, above the cutoff any, extra energy is wasted as heat. And plants don't need a narrow frequency anyway.
      - DougWebb 16y ago
        They don't seem to be using the green light, at least.

quantumhobbit 16y ago

I always assumed that the light would be artificial. And that they were relying on hypothetical cheap energy of the kind that reliable fusion would provide. This may be possible a hundred years from now but surely not in today's energy economy.

mhd 16y ago
But once you've got reasonably cheap and plentiful energy, what's the big incentive for growing locally. If trucking it from Kansas to NYC doesn't pollute as much, reasons for building those towers diminish somewhat. Of course, it's slightly different if you've got plentiful energy, but no good way to transmit/store it. Lots of solar panels all over the city to power its greenhouses. Or windmills in Chicago.

1053r 16y ago

Production prices for solar energy are now below $0.80 / watt (http://www.123jump.com/market-update/First-Solar,-Inc-Q4-Earnings-Call-Transcript/36717/ http://www.123jump.com/market-update/First-Solar,-Inc-Q4-Ear...), although skyrocketing demand has caused wholesale prices to remain much higher. It seems likely that we may in the next 10 years be in a place where we can turn sunlight into electricity, and then electricity into the exact wavelengths of light used in photosynthesis more efficiently than allowing the plants to sit in the sun. If this is the case, than we may be able to grow crops more efficiently indoors than out. But we will be replacing acres of crops with acres of solar panels. And it's unclear to me why we would want these buildings to be skyscrapers, which are much more expensive per square foot than large warehouses in the middle of nowhere.

ars 16y ago
How in the world did you get +8 mod on this? That's utter nonsense! You can only get as much light as you have surface area - so now instead of fields of crops, you have fields of solar collectors! Did you think there was some magical light multiplier device that could give you more output light than you started with? Plants already use the best parts of the visible spectrum to collect light. The small amounts of infra-red you might barely be able to collect and frequency up-convert are not worthwhile - especially since you'd need to throw away all the energy from the higher frequencies in order to get it. Solar cells are terrible as far as efficiency is concerned - and not because of engineering, because that's simply how they work. (Unless you want a multijunction solar cell but those are very very expensive.) And for engineering challenges there simply doesn't exist in the world enough rare earth elements to make enough solar cells for everyone - and that's just for regular electrical usage, forget about growing plants. We do have enough silicon, but silicon based solar cells have poor efficiency.
- DougWebb 16y ago
  I think the idea here is that plants need a narrow set of frequencies and throw the rest away. If solar cells could capture the frequencies plants don't use, convert them to energy, then convert the energy to frequencies plants like, you've increased the efficency of your light-collection area. You'll also have a garden full of black plants, which is both creepy and cool.
  - ars 16y ago
    Solar cells work the same way: they capture a narrow frequency, and throw the rest away. More accurately, below the frequency cutoff they ignore the light, above the cutoff any, extra energy is wasted as heat. And plants don't need a narrow frequency anyway.
    - DougWebb 16y ago
      They don't seem to be using the green light, at least.