When we say solar cells are 39% efficient, that’s as a fraction of all incoming sunlight, so the 3-6% is the correct comparison point, not the 11%, right?
No if you look at the Table 1 in that source, the 3-6% is useful biomass conversion from crops, which is many steps removed.
The maximum efficiency is:
28%: (for the conversion into the natural fuel for the plant cells—ATP and NADPH).
9.2%: conversion to sugar after 32% efficient conversion of ATP and NADPH to glucose
3-6%: harvestable energy, as plants are not pure sugar storage systems and have various metabolic needs
So it depends what one is comparing … but it looks individual photosynthetic cells can convert solar energy to ATP (a form of chemical energy) at up to 28% efficiency (53% of spectrum * 70% leaf efficiency (reflection/absorption etc) * 76% chlorophyll efficiency). That alone seems to defeat the > 1 OOM claim, and some algae may achieve solar cell level efficiency.
Overall, this debate would benefit from clarity on the specific metrics of comparison, along with an explanation for why we should care about that specific metric.
Photosynthesis converts light into a form of chemical energy that is easy for plants to use for growth, but impractical for humans to use to power their machines.
Solar cell output is an efficient conversion of light energy into grid-friendly electrical energy, but we can’t exploit that to power plant growth without then re-converting that electrical energy back into light energy.
I don’t understand why we are comparing the efficiency of plants in generating ATP with the efficiency of solar cells generating grid power. It just doesn’t seem that meaningful to me.
I’m simply evaluating and responding to the claim:
I believe that plants are ≳ 1 OOM below the best human solution for turning solar energy into chemical energy, as measured in power conversion efficiency
It’s part of a larger debate on pareto-optimality of evolution in general, probably based on my earlier statement:
But we now know that evolution reliably finds pareto optimal designs:
(then I gave 3 examples: cellular computation, the eye/retina, and the brain)
So the efficiency of photovoltaic cells vs photosynthesis is relevant as a particular counterexample (and based on 30 minutes of googling it looks like biology did find solutions roughly on par—at least for conversion to ATP).
No if you look at the Table 1 in that source, the 3-6% is useful biomass conversion from crops, which is many steps removed.
The maximum efficiency is:
28%: (for the conversion into the natural fuel for the plant cells—ATP and NADPH).
9.2%: conversion to sugar after 32% efficient conversion of ATP and NADPH to glucose
3-6%: harvestable energy, as plants are not pure sugar storage systems and have various metabolic needs
So it depends what one is comparing … but it looks individual photosynthetic cells can convert solar energy to ATP (a form of chemical energy) at up to 28% efficiency (53% of spectrum * 70% leaf efficiency (reflection/absorption etc) * 76% chlorophyll efficiency). That alone seems to defeat the > 1 OOM claim, and some algae may achieve solar cell level efficiency.
Overall, this debate would benefit from clarity on the specific metrics of comparison, along with an explanation for why we should care about that specific metric.
Photosynthesis converts light into a form of chemical energy that is easy for plants to use for growth, but impractical for humans to use to power their machines.
Solar cell output is an efficient conversion of light energy into grid-friendly electrical energy, but we can’t exploit that to power plant growth without then re-converting that electrical energy back into light energy.
I don’t understand why we are comparing the efficiency of plants in generating ATP with the efficiency of solar cells generating grid power. It just doesn’t seem that meaningful to me.
I’m simply evaluating and responding to the claim:
It’s part of a larger debate on pareto-optimality of evolution in general, probably based on my earlier statement:
(then I gave 3 examples: cellular computation, the eye/retina, and the brain)
So the efficiency of photovoltaic cells vs photosynthesis is relevant as a particular counterexample (and based on 30 minutes of googling it looks like biology did find solutions roughly on par—at least for conversion to ATP).