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Most plants photosynthesise on a very narrow band of light. It's actually more efficient to generate electricity using solar panels and reemit using specific w

Most plants photosynthesise on a very narrow band of light. It's actually more efficient to generate electricity using solar panels and reemit using specific wavelength leds. Plants are around 2% efficient while solar panels are around 20%. Also as has been said below it allows you to stack plants in a way that would be impossible if you were using sunlight. Additional thoughts are that greenhouses are terrible at retaining heat (interestingly the origin of greenhouses used to have a thick southern facing brick wall to act as a heat soak to maintain an even heat throughout the night) and so if you're trying to keep a certain heat level having glass might end up costing you way more in energy because of the need to heat than you gain from the sun.

dwc 11y ago
People still do good things with greenhouses. I recently watched a video from a guy growing veggies through the winter in his greenhouse. He did have a non-glass southern wall but it wasn't the type for storing heat. Instead, he was using drums of water inside the greenhouse as thermal mass, which kept the temperature up during the night.
- lhopki01 11y ago
  And people still grow plants by hand. The future is still going to be automated farms just as the present day is mechanised farms. The advantages that automated warehouse farms give will be too great to not do. Faster grow cycles, no need for fertiliser, pesticides, or herbicides, closer to consumers, space efficiencies and so on.
Retric 11y ago
First, sugar cane converts 8% of the light absorbed by the plant is preserved as chemical energy. Second, photosynthesis is actually fairly efficient, the issue is plants are living organisms and we only care about energy stored not energy used. Net result, plants still need about 45% of sunlight even if you stick with the 'perfect' bands.
- lhopki01 11y ago
  Sugar cane is very much the exception. Most crop plants (which have over the years been selected for efficiency indirectly) manage 1-2%. No one is suggesting growing sugar cane indoors yet, just purely on the basis of it's height you won't gain much by stacking it. Also you haven't addressed stacking, heat retention or for that matter nighttime light.
  - Retric 11y ago
    The important point was Sugar cane is not better at photosynthesis than other plants. It simply 'wastes' less energy on growth and 'life'. Break even would take 50% efficient solar collectors and 90% efficient lights including transmission and conversion losses. Clearly, we are nowhere near that point. PS: The only reasonable option would be solar collectors that focus on different parts of the spectrum and let light through to the plants under them.
    - lhopki01 11y ago
      You don't need 50% efficient solar collectors. That'd be the case if 1 meter squared of plants had 1 meter squared of leaves. Even at full growth there are large gaps and for most of the growing time there are even larger gaps. 1 meter squared of solar panels is always going to be 1 meter squared. Also plants can't use light above 10,000 lux while solar panels will just generate more power. And again how do you stack plants? How do you keep them warm enough? How do you grow them during the night?
      - Retric 11y ago
        Your solar collectors are not operating at night either. Break even means having 10 square miles of solar farm and 1 square mile of dense indoor farming needs to be more efficient than 11 square miles of farming and that extra needs to cover infrastructure costs. You can play with the arrangements of plants in a greenhouse just as easily as a factory. EX: Stacking plants using clear trays and nutrient bath allows for using more light in the same space. Anyway, the reason why this 'works' is crazy subsidies in Japan which actually has quite a bit of farm land, plus a market for ultra premium lettuce for decorative reasons.

dwc 11y ago

People still do good things with greenhouses. I recently watched a video from a guy growing veggies through the winter in his greenhouse. He did have a non-glass southern wall but it wasn't the type for storing heat. Instead, he was using drums of water inside the greenhouse as thermal mass, which kept the temperature up during the night.

lhopki01 11y ago
And people still grow plants by hand. The future is still going to be automated farms just as the present day is mechanised farms. The advantages that automated warehouse farms give will be too great to not do. Faster grow cycles, no need for fertiliser, pesticides, or herbicides, closer to consumers, space efficiencies and so on.

Retric 11y ago

First, sugar cane converts 8% of the light absorbed by the plant is preserved as chemical energy. Second, photosynthesis is actually fairly efficient, the issue is plants are living organisms and we only care about energy stored not energy used. Net result, plants still need about 45% of sunlight even if you stick with the 'perfect' bands.

lhopki01 11y ago
Sugar cane is very much the exception. Most crop plants (which have over the years been selected for efficiency indirectly) manage 1-2%. No one is suggesting growing sugar cane indoors yet, just purely on the basis of it's height you won't gain much by stacking it. Also you haven't addressed stacking, heat retention or for that matter nighttime light.
- Retric 11y ago
  The important point was Sugar cane is not better at photosynthesis than other plants. It simply 'wastes' less energy on growth and 'life'. Break even would take 50% efficient solar collectors and 90% efficient lights including transmission and conversion losses. Clearly, we are nowhere near that point. PS: The only reasonable option would be solar collectors that focus on different parts of the spectrum and let light through to the plants under them.
  - lhopki01 11y ago
    You don't need 50% efficient solar collectors. That'd be the case if 1 meter squared of plants had 1 meter squared of leaves. Even at full growth there are large gaps and for most of the growing time there are even larger gaps. 1 meter squared of solar panels is always going to be 1 meter squared. Also plants can't use light above 10,000 lux while solar panels will just generate more power. And again how do you stack plants? How do you keep them warm enough? How do you grow them during the night?
    - Retric 11y ago
      Your solar collectors are not operating at night either. Break even means having 10 square miles of solar farm and 1 square mile of dense indoor farming needs to be more efficient than 11 square miles of farming and that extra needs to cover infrastructure costs. You can play with the arrangements of plants in a greenhouse just as easily as a factory. EX: Stacking plants using clear trays and nutrient bath allows for using more light in the same space. Anyway, the reason why this 'works' is crazy subsidies in Japan which actually has quite a bit of farm land, plus a market for ultra premium lettuce for decorative reasons.