5 ms·
This is not quite right. Solar panels create an electric current, not fuel. This is a much easier task. When you read that photosynthesis has 1-2% efficiency,
by shoyer 10y ago
This is not quite right.
Solar panels create an electric current, not fuel. This is a much easier task.
When you read that photosynthesis has 1-2% efficiency, that's because they're measuring the efficiency of converting light into sugar.
- winter_blue 10y agoExactly. I suppose the energy density of sugar is pretty high. The non-nuclear fuel with the highest volumetric energy density is jet fuel[1] at 37.4 MJ/L. I wonder how the most efficient natural compound (adenosine triphosphate / sugar / etc) compares... [1] https://en.wikipedia.org/wiki/Energy_density#Energy_densities_of_common_energy_storage_materials https://en.wikipedia.org/wiki/Energy_density#Energy_densitie...
- dredmorbius 10y agoIt's not the energy density of a fuel that matters so much as its net energy content and conversion efficiency. You'll find lipids compare favourably to jet fuel (kerosene), which is distantly related to plant-generated lipids in the first place.
- adrianN 10y agoATP + H20 -> ADP + P produces only 30kJ/mol. A mole of ATP weighs ~500g. You likely get a lot more energy from burning it (the Wikipedia doesn't say), as you do with jet fuel, but that reaction is too hard to reverse to be useful for organisms. A mole of glucose produces 2800kJ/mol when you burn it. A mole weighs ~180g.
- spaceheeder 10y agoUsing http://lmgtfy.com/?q=jet+fuel+density http://lmgtfy.com/?q=jet+fuel+density to get a range of 775.0-840.0 g/L for jet fuel, that gives us 37.4MJ/807.5g (taking the average of the jet fuel's mass) against 2.8MJ/180g for glucose. Scaling the denominator of each to 1kg, that's ~46.3MJ/kg for jet fuel and ~15.6MJ/kg for glucose. Given how biochemically cheap glucose is to produce compared to jet fuel, I'm surprised it's only off the state-of-the-art by a factor of three.