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Target880 t1_jachu1t wrote

The max theoretical efficiency for photosynthesis is 4.6% for C3 and 6% C4 plants, that is of incoming sunlight.

Cheap solar panels, the type used for example on building roofs have a practical efficiency of around 20%. The most efficient but a lot more efficient are 47% efficient, they are used on for example satellites. The max theoretical efficiency is 86%

So we have already lowe cost solar panels that are over 3x as efficient as the theoretical efficiency for plants. Copying photosynthesis is not a good idea for efficiency because we already have more efficient technology.

Plants have the advantage the grow from seeds and do not need to be made in a factory. They also produce sugar chains that are stable molecules we can extra energy from later. There is no need to copy plants we can just use plants and harvest them as an energy resource.

Energy forestry is something that is done. Humans have done it for centuries by letting trees grow used for firewood.


NameUnavail t1_jacf5rk wrote

There's already technology to create power from sunlight. It's called solar.

There's no point in trying to get a plant to do it


ScienceIsSexy420 t1_jacfs9r wrote

Plants have been doing photosynthesis and harvesting sunlight energy for far longer than humans have. They are significantly more efficient at doing so than humans are, and it is very much a goal worth pursuing. Our best solar cells are currently around 20-23% efficient, implants are far more efficient than this. More efficiency means more electricity generated


einmaldrin_alleshin t1_jacjjlu wrote

Plants are significantly less efficient than solar panels, particularly because they are limited by the amount of CO2 that they can get. 400 PPM is a lot when it comes to climate change, but when you're trying to synthesize carbohydrates, that's a problem.

On top of that, photosynthesis only works in a narrow temperature range, it requires a lot of water that just gets evaporated, and it requires minerals and nitrogen, which have to be produced expending a lot of energy.


ScienceIsSexy420 t1_jack5ac wrote

Plants are more efficient in terms of energy generated per photon absorbed. As you mentioned, CO2 concentration is absolutely limiting factor for plants, but this could be fairly easily addressed when adapting the technology for a PV cell.


einmaldrin_alleshin t1_jacq42c wrote

> Plants are more efficient in terms of energy generated per photon absorbed.

That is an incredibly misleading, since chlorophyl does not absorb all photons. It doesn't absorb any infrared, and is mostly transparent between 500 and 600 nm. So by that measurement, you're not counting about half of all sunlight that hits a plant. Silicon based solar may be less efficient per photon, but it absorbs everything from 800nm up to UV.

> but this could be fairly easily addressed when adapting the technology for a PV cell.

You mean DSSC cells? I suppose it's "easy" to demonstrate the effect in a lab under controlled conditions, but in real world applications, where they need to work for decades exposed to the environment, it stops being easy and becomes very, very hard. There's a reason you can't buy them.

They are also not projected to be more efficient than regular solar panels under sunlight, there's just hope that they might become cheaper.


NameUnavail t1_jacg7ui wrote

Yeah I think engineering more efficient solar might be a better investment than trying to GMO a plantable phone charger....


mytrickytrick t1_jacgeu1 wrote

It could be the next gen pickup line: "hey cutie, I see your cell phone is low on battery. Here's my charger and a flower for you"


ScienceIsSexy420 t1_jachhxh wrote

It's not about making GMO plants, it's about making solar cells with the highest efficiency possible. The most efficient means we have discovered in the entire universe can for converting sunlight into electric energy is photosynthesis, so why wouldn't we try and emulate that?


ScienceIsSexy420 t1_jacfljd wrote

I've been intrigued by this very question since I first learned about photosynthesis and the electron transport chain 20 years ago. Much work has been done trying to accomplish exactly what you're describing, but so far we have yet to successfully recreate photosynthesis. The major sticking point is that the compounds that we create to synthetically reproduce photosynthesis are not nearly as durable as the biologic molecules in a plant. We cannot directly use the same molecules that plants use because we are trying to accomplish something slightly different: plants use the electrons generated by photosynthesis to create sugar molecules, while humans are trying to harvest the electrons directly. Moving electrons is a chemical reaction called an oxidation-reduction reaction (called redox for short), and our redox molecules simply aren't as stable or efficient as their protein counterparts.


kinyutaka t1_jaci27d wrote

I think that the biggest problem with trying to use plant-based photosynthesis for electrical power generation is that photosynthesis is the creation of sugars through the combination of CO2 and water, utilizing energy from the sunlight.

Those sugars are great for animals to produce heat energy, but not good at generating electricity directly.

Meaning, we would need to translate the sunlight into sugar, then use the sugar to generate one kind of energy, then use that energy to generate power. Each step involves a decrease in efficiency.

Plants overcome that efficiency issue by growing larger and taller, to get more sunlight. Animals overcome that issue by eating more plants or eating more plant-eaters.

Photosynthetic power plants would have to become exponentially larger to overcome three or more steps of inefficiency.


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A_Meal_of_Pain t1_jacfphh wrote

For thousands of years plants were our primary source of power in the form of burning wood. It was even the primary source of power at the beginning of the industrial revolution.

The reason it phased away as a source of industrial level power is because it just is not concentrated enough. That and the fact that extracting it has so many negative side effects for the environment.


ScienceIsSexy420 t1_jacfutf wrote

This question is about replacing photovoltaic cells with photosynthesis as a means of generating electric currents. They're not asking about combusting plans to generate electricity


kinyutaka t1_jaciiuk wrote

The point he was trying to make with his answer is that burning plant material (wood) or fossil material (coal) is the most efficient way of getting the energy out of a plant.

It is dirty and bad for the environment, but it is efficient.


ScienceIsSexy420 t1_jacivow wrote

But that's not what the question was asking about. The question was asking about utilizing the chemistry of photosynthesis for a new generation of photoelectric cells, which is both more efficient than burning fossil fuels as well as being better for the environment. This is an area of active and ongoing research, and shouldn't be dismissed by simply saying " burning fossil fuels is better"


kinyutaka t1_jacjkms wrote

We can and probably are trying that very thing, but the way plants do it creates sugars and fibers, not creating free electrons.

It's just not something that we can replicate completely for our purposes.

One thing we might be able to do is capture the carbon emissions from burning plant material, like sugars, then use the CO2 from those emissions to feed a new generation of photoelectric cells. There would probably be loses in the system, but...


ScienceIsSexy420 t1_jack1ov wrote

Photosynthesis does indeed generate free electrons, these electrons are used to power redox reactions which are used to synthesize starches. This is indeed an area of ongoing research, one of the professors at the institution I just graduated from was focusing his research on this very topic. Both plants and animals generate free electrons during metabolism, and use these electrons to do things. Harvesting the electrons is quite feasible


kinyutaka t1_jack5sx wrote

Harvesting the electrons might be feasible, but is it efficient enough for our purposes?


ScienceIsSexy420 t1_jackcdp wrote

As per my understanding, it is continuously harvesting those free electrons that is the limit of our ability and the focus of the current Research into the topic. Currently no, the materials that we use to harvest the energy generated do not have the lifespan to be of significant use. But the point is that this is a goal worth pursuing further


kinyutaka t1_jaclj18 wrote

I am not trying to say that it isn't worth trying. Only that it is clearly not good enough for mass market.


[deleted] t1_jacg3a6 wrote



No_Dust_5360 OP t1_jacglli wrote

Would it be possible to somehow genetically modify plant's to not use all their power for the following processes and extract the power in some way?


kinyutaka t1_jaciav7 wrote

Probably not. Biological drive would cause the plants to grow larger if excess energy is provided.


ScienceIsSexy420 t1_jachoww wrote

Photosynthesis absolutely is a means for generating energy, plants use the energy created to fuel the creation of sugar molecules which are then later break down for food. The starches created by plants during photosynthesis can only be created with the energy from the sunlight. Saying photosynthesis doesn't generate energy is pretty ridiculous


[deleted] t1_jacihxa wrote



ScienceIsSexy420 t1_jacj18h wrote

Right, the question is about the electrons generated by photo system 1 and photo system 2 during photosynthesis, and harnessing that as a means of electricity production. So by responding by saying photosynthesis doesn't generate energy, you're missing the fundamental aspect of the question in my opinion