[Request] How much energy do you get per acre of solar panels vs an acre of corn grown for ethanol

[u/capilot]

I googled that, but the difference seems too much to believe. Google says an acre of solar panels will produce 250-500 MWh/year while an acre of corn produces about 12.3 MWh/year.

So an acre of solar panels replaces 20-40 acres of ethanol corn? That seems too good to be true. And TBH, I trust the Google AI about as far as I can throw it.

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[u/Fragmatixx]

This is dependent on what numbers you use to calculate but yes… photovoltaics are ~10 times more efficient than photosynthesis at turning sunlight into usable energy. Also a corn plant does not use 100% of that energy to make corn.

[u/sheltonchoked → u/Fragmatixx]

And not all the corn energy gets converted to ethanol.

Edit:
If all the acreage for corn ethanol was converted to solar, it would provide 4x the total electricity demand for the USA.

[u/toupeInAFanFactory → u/sheltonchoked]

and every year you have to re-plant that corn field, and fertilize it (more energy invested) and then harvest and process it. which is both work and energy investment. once the solar's in, you just let it do its thing.

[u/anothercorgi → u/toupeInAFanFactory]

And solar panels work in the winter, corn won't grow when it's freezing out...

Granted, snow covered solar panels don't work so well, neither does snow covered corn.

[u/vespers191]

Why would you be surprised? Corn does a great job of turning sunlight into corn, but then in order to further extract energy out of corn you have to process it into ethanol, which loses energy, transport that ethanol to a fuel depot, which loses energy, mix it into the fuel, which loses energy, and then burn it in an engine, which, you guessed it, loses energy.

Electrons, on the other hand, lose energy through heat and transmission losses, but don't need to change form in the meantime, are being delivered free from the solar panels, and benefit from being intentionally harvested in their final form, rather than being repeatedly chemically changed like corn ethanol.

[u/archontophoenix → u/vespers191]

A great job for a plant but a terrible job in terms of raw numbers. Only 3-6% of the solar energy that hits the corn gets turned into plat matter and only about half of the corn’s mass is harvestable corn.

[u/pbmadman]

Well here’s an answer that predates Google ai.

https://www.reddit.com/r/solar/s/zltrBp4fdZ

Depending on what exactly you are comparing, PV is 14 to 197 times better than corn ethanol per area used

From the article:

Assuming average EROI, net energy production per
acre is 100-125x greater for solar PV than for
corn-based ethanol
Looking at total energy generation from corn to
account for useful by-products of ethanol
production used as animal feed, solar PV
generates 14-17 times more gross energy per acre
than corn produces.
Looking at land-use efficiency, corn-derived
ethanol used to power internal combustion
engines requires about 85x (range: 63-197x) as
much land to power the same number of
transportation miles as solar PV powering electric
vehicles.
Technological advances provide substantial scope
for increased land use efficiency from solar PV:
energy density (MWh per acre) has increased 25-
33% from 2011-2019.
Even if the ethanol is converted to electricity to
power more efficient electric vehicles, corn
ethanol still requires 32x the amount of land to
power the same number of vehicle miles.

[u/Alpha_Hellhound]

Yeah, solar farms produce far more energy than corn. Its pretty basic. Direct energy from the sun vs energy transferred through growth, then made into heat. Also, if you take into consideration that things can be grown under the solar panels to add to the energy production, it gets even farther ahead.

[u/AnotherAnonymousA]

Solar has a lower production cost. Install panels, wire for usage, and wait for sun. Corn requires water, mechanization, fuel, and labor.

[u/curiouslyjake]

That's about right. Replacing corn fields used for ethanol with solar panels is a great idea in terms of energy. It would generate several times the total electrical power consumed in the US per year, and a significant chunk of all energy from all sources. It's worth noting that corn grown for ethanol is not entirely consumed by producing ethanol. There's still corn left for animal feed and for some corn oil products, but that doesnt change the basic idea.

[u/OopsIMessedUpBadly]

Every comment seems to be saying that yes, solar is far more efficient. So you may ask: why would anyone opt for producing ethanol?

The obvious answer is that it works on petroleum cars to a certain extent. The other reason is that solar power only works when the sun is shining, which might not be when you need the energy.