# Power plants — literally

It is well known that some organisms can produce electricity. Therefore I think it would not be too much of a stretch to assume that also some plants might have evolved that ability (after all, it could be a great deterrent to predatory herbivores).

How could such a plant be used for energy production? Could it even be feasible at all?

• like trees? They take solar energy and use that to turn co2 into solid mass, which can be burned to power generators (steam or whatever). Does that count? – J. Musser Feb 25 '15 at 18:40

When dealing with organisms, you're pretty much always dealing with Electro-chemical energy, rather than "pure" electrical. It's not the sort of thing you'd wire up to a circuit exactly - but they could have protrusions you could use like say, rechargeable batteries.

You'd want to breed/GM the plants to grow their "cells" as big and as separate as possible - something like nodules in the roots or hanging fruit type structures would be great. Then you'd hook electrodes in to the cells (think a potato battery) and tap off the electrical energy. You'd have to carefully load balance though, or it would be easy to deplete very quickly - and depending on how the plant worked, you could drain it of sugars really fast as it tried to recharge and kill it. You'd want to use pretty huge fields of these crops to get much useable energy out of this - plant photosynthesis is already pretty poor on efficiency (order of 1 or 2% I think) and there are going to be other losses between forming sugar and generating electrochemical energy.

If you're really interested in the science of this, someone wrote a series of books on it http://books.google.co.uk/books?id=6a1_Gw8Tt10C&redir_esc=y - see more in the related below. No idea how much sense they make to a non-electrophisiologist though.

Edit: Wiki says that photosynthetic plants manage 3-6% efficiency on conversion of (photosynthetically available) solar energy into chemical energy. For contrast, solar panels typically manage ~15% solar into electrical energy, and more advanced (and more expensive) panels managing ~40%

• Efficiency compared to solar panels may be a point, but this would be an easy accesible source of electricity to the local civilication by far ealier because you just need a wire to use it (which may lead to electricity being found and made usable earlier) and the technical knowledge/effort required is minimal compared to solar panels. – Sebb Feb 25 '15 at 21:20
• This is a pretty poorly researched answer I'm afraid. The 3-6% efficiency rating has no bearing on how feasible this is. Plants have much higher quantum efficiencies than silicon when it comes to direct PV conversion. – Aron Feb 26 '15 at 15:25
• Not sure how quantum efficency is relevant? If you want to do work with the electrical energy, then what's relevant is the ratio of energy output (elec) to energy input (solar radiation). Sure, choloplasts might do a great job of turning photons in to electrons from photosynthesis - but the imporant part of it is the whole process. In a "battery plant" with some kind of electrolyte bodies on it, like I imagine, you're going light -> sugar -> ATP -> Pump Ions. I was trying to give a sense of how much energy you might be able to get out of such a system. – CMaster Feb 26 '15 at 16:53
• @CMaster my point is every step you have there is pointless. Why make sugars when you could harvest the light directly. large.stanford.edu/courses/2010/ph240/usui2 – Aron May 17 '18 at 14:36

Just some stats, hopefully my math is correct, please inform me if its not (a very real possibility)

In 2013, the average annual electricity consumption for a U.S. residential utility customer was 10,908 kilowatthours -eia.gov

Ends up being roughly an average of 32 kilo-watt hours per-day

(Electric fish can generate a) range from 10 to 600 Volts with a current of up to 1 Ampere, according to the surroundings - from OP's wiki link
and
600 volts and 1 ampere of current (600 watts) for a duration of two milliseconds. from Electric Eels wiki link

Watts = Amps x Volts and kiloWattHours = kiloWatts * hours

So one electric eel can generate up to (600 * 1 = 600) watts of energy / 2 milliseconds.

It takes 500 of these shocks to get to 600 watts / second, 30,000 shocks for 600 watts/minute, and 1,800,000 shocks to get to 600 watts/hour

32,000 watts/hour / 600 watts/hour = 53.3
1,800,000 * 53.3 = 95,940,000 shocks need to happen in each hour, for electric eels anyway. This is for one average American household.

That is 1,599,000 shocks per minute, or 26,650 shocks per second.

Since you also need to convert those shocks to some form of usable energy, (I'm not sure how that would be achieved), then there is also a loss of energy - so you'll need even more than that in practice.

Unfortunately, I haven't been able to find how often electric fish can achieve this level of shock, which is the next step I would need to do to actually figure out how many electric fish I would need, but that seems like a ton of shocks to me.

One other thing to note is that, in the electric eel's case, there are three organs which generate the electric shocks, which take up 4/5 of the eel's body. They can grow up to 2 meters long.

These organs are made of electrocytes, lined up so a current of ions can flow through them and stacked so each one adds to a potential difference. When the eel locates its prey, the brain sends a signal through the nervous system to the electrocytes. This opens the ion channels, allowing sodium to flow through, reversing the polarity momentarily. By causing a sudden difference in electric potential, it generates an electric current in a manner similar to a battery, in which stacked plates each produce an electric potential difference

This source seems to suggest that you would need 24 eels for 30 amps at 240 volts, and has a video of an eel powering christmas tree lights. Though most of the lights seem to be unlit for most of the time.

The heat pump uses 30 amps at 240v, the electrical eel produces approximately 1 amp at 500v. To make this happen, you will need an inverter to change the DC to AC, a voltage regulator to keep the voltage constant and 24 electric eels. Remember, the electricity produced is not constant, so this is really not a viable choice for power generation. Plus, you also need aquariums, feed and space for all these "free" power generators

• Electrocytes are not muscles, all they do is discharge (relatively) simultaneously, the nature of their connection to one another resulting in summation of the potentials of their discharge. As to the Sodium, it is pumped back into the electrocytes after a discharge, at the expense of energy in the form of ATP. – Monty Wild Feb 25 '15 at 22:47
• @MontyWild Nice catches. "muscle-like" electrocytes from the source, but there's a lot of information in my answer that I'm not completely confident is correct. -disclaimer ;) – DoubleDouble Feb 25 '15 at 23:08
• Of course just a hundred years earlier the average energy consumption of a typical household was much lower. Moreover the U.S. are not exactly known for energy efficiency … – celtschk Mar 4 '15 at 19:26
• Very true, Wikipedia has a nice list of energy usage by country. Funny enough, Iceland produces enough electricity for each person to use twice as much as the next highest country, and three times as much as the United States. (That's electricity provided to each person - not total electricity generated) – DoubleDouble Mar 5 '15 at 15:36

Is this plausible? You would have to ask the various active research teams in the world who are actively researching this field right now.

However last I checked there were still many many challenges before this is feasible.

As @Jasper pointed out, plants actually already do this, and very very efficiently as well. Its just that the selfish b£\$%^&ds use all that lovely electrical energy to feed themselves (or more accurately, the chloroplasts feed the cell).

Green plants have pigments (which make them green), called Light Harvesting Complex. These are insanely efficient solar cells, which absorb a photon, and kick out a high energy electron. Scratch that...no...Light Harvesting Complexes are friggin Light frequency Rectennas (or Nantenna for short), the bleep beeping holy grail of PhotoVoltaic technology (not some clumsy bandgap diode).

Last I checked on the research, scientist were able to capture the high energy photo from the Light Harvesting Complex and put it to good use. However, we were not able to donate a 'used' low energy electron back to the Light Harvesting Complex to 'reset' it for the next photon.

Even if we were to be able to complete the circuit with the Light Harvesting Complex, we would then need to figure out a way to wire up your power grid to individual chloroplasts.

So why bother? Well because the theoretical maximum efficiency of a semiconductor 3 junction PV panel is ~60%. Whilst we know that the same limit on an Nantenna array is close to 100%.

Should a civ be able to GM at an insane level, electrical production by growing PV panels would be logical, assuming a need for electrical power.

It looks like everyone so far is focusing on biochemical/solar. So, I'll toss out another theory...

I'm not sure if it could be harnessed in any really useful way, but I'm picturing trees that could build and store static electric charges.

I'm thinking that in a windy enviroment where the branches are frequently blowing and rubbing against each other it may be feasible for a strong static charge to develop... The hard part for the tree would be insulating/storing the charge and only discharging it when needed.

• If "when needed" is to deter grazing animals, then that should take care of itself - they provide a low enough resistance path to ground that it jumps. – CMaster Feb 26 '15 at 16:56

Yes, this is plausible -- with a great deal of genetic engineering. The key is to tap the electricity before it is used in photosynthesis. Much of the genetic engineering would be spent on producing wires to gather the electricity.

Imagine a surface, covered with chloroplasts. Each chloroplast has two branches, so that the inside of the chloroplast leads to one side of the "battery", and the intermembrane space of the chloroplast leads to the other side of the "battery". The chloroplast will use its gathered solar energy to produce a pH difference between the two leads. This pH difference is equivalent to a voltage difference. "Steal" a portion of the current produced, and you have a low voltage battery.

If you don't "steal" too much, the plant can be self-reproducing. If the "wires" are metallic, the plant would need a lot of that metal in its fertilizer. (Cellular material has a high specific resistance. An unmyelinated neuron has conduction losses of 10 percent in about 50 microns; a myelinated neuron has conduction losses of 10 percent in about 700 microns.)

• neurons cannot transmit electrical energy. They do (kind of) propagate an electrical signal, but that signal is continuously (for un-myelinated axions) boosted by Na/K ion pumps along the axion's length. However you could some kind of protein wire, it would have to have a structure very similar to a nanotube... – Aron Feb 26 '15 at 15:56

It is highly unlikely that plants would ever be able to generate the amount of electricity required to power a city, or even a single household.

This becomes clear when you study the first law of thermodynamics. This law has to do with the conservation of energy. The plant would have to get its energy from some outside source. This would most likely be the sun. It would be much more efficient to gather the sun's energy using solar panels instead of plants.

• It might make for more efficient gathering, but what about production? If, for what it costs to manufacture, ship, and install a single solar panel, you could grow an entire lawn full of solar grass, that might be worth it. – Mason Wheeler Feb 25 '15 at 16:13
• @MasonWheeler and then how much will it cost to wire your "entire lawn full of solar grass" into something useful? Especially when each blade of grass is technically an independent plant and they'd all need to be wired together? – Doktor J Feb 25 '15 at 17:57
• @DoktorJ: Have you ever looked at sod? Grass roots are all intertwined and connected into one big network. If the plant worked the right way, they could be already wired together. – Mason Wheeler Feb 25 '15 at 18:00
• I'm now curious if watering my electro-lawn is potentially dangerous if I am barefoot. (or even without water for that matter) – DoubleDouble Feb 25 '15 at 19:11
• @DoubleDouble Probably not because the current can' use you to uncharge itself. However, watering it from outside your lawn may destroy it. This is not going to be in the adverts, though. – Sebb Feb 25 '15 at 21:17

Electricity is nearly useless because it is hard to store.

Much better energy source is some substance which is easy to store and can be converted to electricity on demand - like, uhh, carbohydrates?

So best way to get energy is to get algae to produce oil (not ethanol, because you will use lots of energy to distill it), which is hydrophobic and can be skimmed from the top of vat. And there were found such algae, creating butanol (4 carbon).