I think this is the beginnings of an economy based on perpetual growth and fossil fuel energy running headlong into geological energy constraints. Basically I see an undulatory downward path for the rest of my life. From here out, I think any rallies in our economic condition are going to be met with spiking commodity prices that knock us right back down.
Joined: Oct 18, 2004 Posts: 266 Location: San Francisco, CA
Posted: Mon Apr 30, 2007 12:51 pm Post subject: Why ethanol sucks -- can someone check my math
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
Joined: Apr 17, 2005 Posts: 2750 Location: Vancouver Island
Posted: Mon Apr 30, 2007 1:01 pm Post subject: Re: Why ethanol sucks -- can someone check my math
The likely hood of getting perfect solar conditions 8 hours a day 365 days a year is likely zero in most parts of the world. _________________ shame on us, doomed from the start
god have mercy on our dirty little hearts
Joined: Jan 03, 2005 Posts: 1206 Location: western Wisconsin
Posted: Mon Apr 30, 2007 1:31 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Here in Western Wisconsin, we get the equivelant of 4 hours of good sun per day, on an annual basis (from a couple of years records of actual electrical output.)
Joined: Apr 16, 2007 Posts: 218 Location: New Mexico
Posted: Mon Apr 30, 2007 2:23 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Clouseau2 wrote:
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
Although the assumptions a little generous, your calculations are on the right track. But step back a level. Comparing corn/ethanol to solar cells is like comparing apples to puppies--while both edible, they are really vastly different:)
For one thing, you could fairly easily grow an acre of corn, year after year. Even *without* fossil fuels. But if you can puchase an acre's worth of solar cells, then I salute you!
If you can grow corn, I would grow corn. But I would have *some* solar cells on hand too, for redundancy and backup, the quantity determined by your budget. You could *always* trade them later. Ditto for wind turbines.
However, your post does hit the nail on the head in one sense, comparisons aside...producing fuels in a world of peak oil is going to be HARD work. Alot of folks get excited because we *can* create biodiesel and ethanol, thinking it is the 11th hour black-box solution we are looking for to enable to continue business as usual. But they have no Idea what the numbers actually look like. Your calculations were definitely a peak under the lid of that box.
Joined: Oct 18, 2004 Posts: 266 Location: San Francisco, CA
Posted: Mon Apr 30, 2007 2:38 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Sheb wrote:
Clouseau2 wrote:
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
Although the assumptions a little generous, your calculations are on the right track. But step back a level. Comparing corn/ethanol to solar cells is like comparing apples to puppies--while both edible, they are really vastly different:)
For one thing, you could fairly easily grow an acre of corn, year after year. Even *without* fossil fuels. But if you can puchase an acre's worth of solar cells, then I salute you!
If you can grow corn, I would grow corn. But I would have *some* solar cells on hand too, for redundancy and backup, the quantity determined by your budget. You could *always* trade them later. Ditto for wind turbines.
However, your post does hit the nail on the head in one sense, comparisons aside...producing fuels in a world of peak oil is going to be HARD work. Alot of folks get excited because we *can* create biodiesel and ethanol, thinking it is the 11th hour black-box solution we are looking for to enable to continue business as usual. But they have no Idea what the numbers actually look like. Your calculations were definitely a peak under the lid of that box.
I was mostly thinking it from two divergent futures ...
One future where we attempt to switch over to biofuels to keep things running.
Another where we invest heavily in battery driven electrics.
Assuming the costs of solar cells come down significantly, it looks like the latter future has more hope.
Especially since the efficiencies of the energies produced by the solar cells are so much better too.
Joined: Jul 29, 2005 Posts: 252 Location: Show-Me State
Posted: Mon Apr 30, 2007 2:40 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Good luck: From Pheba, from the farm:
You can figure at least one pound of synthetic nitrogen fertilizer (think natural gas) for each bushel of corn. Not each acre, each bushel. The maximum corn output on the top land in the U.S. is 200 bushels per acre. That is an amazing figure. Add potash and phosphate to the mix. Also, add fuel for the tractor and combine, etc. Add fuel to transport the corn, process the corn, etc. etc.
Here at our farm we have stopped feeding corn to our cattle. We can no longer afford it.
We are spiralling into a black hole of negative energy in the U.S. because of ethanol.
Ethanol is insane.
Pheba.
Posted: Mon Apr 30, 2007 4:14 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Phebagirl wrote:
Ethanol is insane.
Pheba.
Yup, the physics is really simple. Any moonshiner knows you must burn cordwood to power your still. If you fueled your still with the ethanol you collected, you would end up with nothing.
But politicians are smarter than that. They say "Corn is grown by farmers, farmers vote at the polls"
Economists say "look at the Business Plan. If the end product is priced high enough, it will work." _________________ Remember: 73.3% of statistics are made up
and the other 23.6% are wrong
Posted: Mon Apr 30, 2007 4:55 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Clouseau2 wrote:
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
MY advice are as follows:
(1) You can't use all the area for solar panel, so drop the area from 4046 square metres to 2023 square metres of solar panel per acre.
(2) You do not get 8 hours of sunshine per day. So drop that to a conservative 4 hours of sunshine per day.
(3) You do not get 20% in photovoltaic, so drop that to 10%
The end result is 236,000 kwh/acre/year of electricity.
Still better than ethanol.
Joined: Oct 18, 2004 Posts: 266 Location: San Francisco, CA
Posted: Mon Apr 30, 2007 5:10 pm Post subject: Re: Why ethanol sucks -- can someone check my math
ohanian wrote:
Clouseau2 wrote:
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
MY advice are as follows:
(1) You can't use all the area for solar panel, so drop the area from 4046 square metres to 2023 square metres of solar panel per acre.
(2) You do not get 8 hours of sunshine per day. So drop that to a conservative 4 hours of sunshine per day.
(3) You do not get 20% in photovoltaic, so drop that to 10%
The end result is 236,000 kwh/acre/year of electricity.
Still better than ethanol.
Posted: Mon Apr 30, 2007 7:09 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Clouseau2 wrote:
ohanian wrote:
Clouseau2 wrote:
I was just going to compare the equivalent KWH energy production on one acre of land using corn (ignoring inputs) versus having an acre of solar panels.
1 acre can produce 370 gallons/ethanol per year. 1 gallon of ethanol is 75,700 BTUs or 22 KWH.
So you get 8140 KWH/acre/year worth of energy.
1 acre of solar panels gives you:
800 watt/sq meter * 8 hrs per day * 365 days a year * 4046 sq meters per acre * .2 solar cell efficiency / 1000 (watt to KW) = 1,890,291 KWH worth of energy
You get 232 times as much useful energy from solar cells as from ethanol.
If I made any mistakes or wrong assumptions, please correct them.
MY advice are as follows:
(1) You can't use all the area for solar panel, so drop the area from 4046 square metres to 2023 square metres of solar panel per acre.
(2) You do not get 8 hours of sunshine per day. So drop that to a conservative 4 hours of sunshine per day.
(3) You do not get 20% in photovoltaic, so drop that to 10%
The end result is 236,000 kwh/acre/year of electricity.
Still better than ethanol.
Also, I sure do get 8 hours of sunshine here in California ...
Straight from wikipedia
Typical solar panels have an average efficiency of 12%, with the best commercially available panels at 20%. Thus, a photovoltaic installation in the southern latitudes of Europe or the United States may expect to produce 1 KWh/m²/day. A typical "150 Watt" solar panel is about a square meter in size: such a panel may be expected to produce 1 KWh every day, on average, after taking account the weather and the latitude.
In the Sahara desert, with less cloud cover and a better solar angle, one can obtain closer to 8.3 kWh/m²/day. The unpopulated area of the Sahara desert is over 9 million km², which if covered with solar panels would provide 750 terawatts total power. The Earth's current energy consumption rate is around 13.5 TW at any given moment (including oil, gas, coal, nuclear, and hydroelectric power).[1]
Let's calc again
1 kw/m^2 Sunshine at Equator
10% efficiency of Solar Panel
0.1kw/m^2 power per metre square of solar panel
4 hours sunshine/day (very conservative)
0.4 kwh/m^2/day energy per metre square of solar panel per day
Joined: Sep 16, 2004 Posts: 4863 Location: Southwest WI
Posted: Mon Apr 30, 2007 10:27 pm Post subject: Re: Why ethanol sucks -- can someone check my math
Last i heard, it requires a lot of energy to produce solar panels, so figure that in. You also HAVE to figure in inputs when growing corn. Just trying growing corn year after year with no inputs. Good luck with yields. You need to plant/weed/hope to god or great power for rain/sun/heat...etc etc. Another problem is solar panels produce when its sunny out, no power when dark and scary. Life is so complex. _________________ Clothing should be optional.
Posted: Tue May 01, 2007 12:07 am Post subject: Re: Why ethanol sucks -- can someone check my math
you must consider cradle-to-grave life cycle analysis when measuring and comparing primary energy sources. This entails an energy accounting and a tally of debits/credits and (for capitalized assets like solar panels, windmills etc.) depreciations.
Thus, the acre will produce corn ethanol year after to but each season it requires chemical inputs (including fertilizer and biocides) and especially energy for planting, cultivating, and harvesting. The grain must be milled, hydrolyzed, fermented, distilled, and cleaned to make ethanol. This cost energy.
Likewise silicon must crystalized at great energy expense to form solar arrays.
The value generated by this study is commonly called EROEI (energy returned on energy input.) It is an up-and-coming discipline that you might want to consider studying when you get to college. _________________ ree rah rip ram. sunofabitch godamn. hidey didey christ almighty. rah rah crap
Posted: Wed May 02, 2007 9:51 am Post subject: Re: Why ethanol sucks -- can someone check my math
A large taxpayer donation would be necessary
to make a 1-acre project fully cost competitive.
The same amount of subsidy devoted to wind power would
create a lot more energy, and the same bonus to greater
efficiency wisely applied much greater still.
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ree rah rip ram. sunofabitch godamn. hidey didey christ almighty. rah rah crap 
