magnet_prophet - 22-6-2019 at 13:09
I'd like to map the efficiency of all possible routes to producing glucose. Here's what I've got so far.
Most glucose is produced by photosynthesis, but photosynthesis is terribly inefficient. Disregarding the inefficiency of the plant, photosynthesis is
~32% efficient at converting the optimal wavelength of light into chemical energy in glucose.
thus:
Using sunlight as an energy source for photosynthesis brings the overall theoretical maximum efficiency from ~32% down to ~13% due to some of the
light not being used and most of the light only using some of its energy.
Using electricity as an energy source for photosynthesis brings the overall theoretical maximum efficiency to ~8-19% efficiency depending on LED
efficiency. (assuming 25-60%)
Using high grade thermal energy to produce electricity further reduces overall efficiency to ~3-7%. (assuming 35% thermal to electric)
Natural leaves lose another 30% by just absorbing it in structural materials and use 35-40% of the energy they produce. This reduces the efficiency to
~44% the theoretical maximum.
It would be reasonable to expect <2% efficiency converting thermal to electric to light to glucose in practice. 2000 calories/day is 114 kwh/day at
2% efficiency.
(https://en.wikipedia.org/wiki/Photosynthetic_efficiency)
Alternatively chemosynthetic bacteria convert hydrogen sulfide and carbon dioxide into sugar, water and sulfur (12H2S + 6CO2 -> C6H12O6 + 6H2O +
12S). The sulfur can be regenerated into hydrogen sulfide by adding hydrogen giving the effective reaction (12H2 + 6CO2 -> C6H12O6 + 6H2O).
Disregarding the efficiency of the bacteria, this reaction is ~82% efficient.
thus:
Using electricity to split water the overall theoretical maximum efficiency is ~57-74%. (assuming electrolysis to be 70-90% efficient)
Using high grade thermal energy to produce electricity further reduces overall efficiency to ~20-26%. (assuming 35% thermal to electric)
Using high grade thermal energy to split water with a catalyst brings the theoretical maximum efficiency to ~16-33%. (assuming 20-40% thermochemical
efficiency)
I have no idea how much energy the bacteria use, but assuming its less than 50% it would be reasonable to expect >10% efficiency converting thermal
energy to glucose. 2000 calories/day is 22.8 kwh/day at 10% efficiency.
I'm sure there are many other routes to glucose, but I can't find them on wikipedia.
Tsjerk - 22-6-2019 at 13:52
Go for photosynthesis, although maybe not the most efficient, sunlight is free and photosynthesis is quick. Hydrogen sulfide eating bacteria are slow
as hell and not fun to grow.