This post will collect links and calculations posted in comments elsewhere. This may become a monthly feature.
Posted 2005-Sep-11 at Peak Oil Optimist in a story about biomass:
Well, let's see.
Land area of Illinois: 57918 square miles
, or about 37.1 million acres. 8% of that is 2.97 million acres; call it 3 million. (This is about 1/4 of the 11.8 million acres planted to corn in Illinois in 2004.)
Yield of Miscanthus or switchgrass: roughly 10 tons/acre/year. Call the yield 30 million tons/year.
Heat of combustion: 10 million BTU/ton?
Total available energy would be 300 trillion BTU; converted to electricity at 33% efficiency, it would yield 100 trillion BTU or 29,300 million kilowatt-hours.
Total electric consumption in Illinois in 2001 was 92,358 million kilowatt-hours
So no, growing grass to fire electrical generators wouldn't satisfy the state's needs. Not even close.
Boosting efficiency from 33% to 40% isn't going to make up for a 3:1 gap. If you can get 2.5 tons/acre of corn stover from the crop acreage, the ~30 million tons of biomass from that would get you closer but not all the way there.
But riding my hobby horse for a bit... 30 million tons of biomass with 30% conversion to char would make 9 million short tons of charcoal. If each pound of char can make 5.448 lb of zinc metal and you can get 423.6 Wh/lb out of the zinc, you'd get 41,500 million kWh out of it. That's better than 45% of requirements.
Double the 8% of land area to 16% and you've hit 90%; add 30 million tons of corn stover and you're up to 135%. That looks good, especially if you add some wind (if I were designing this I'd shoot for wind capacity of 30-50% and use zinc to run transport).
Heiko Gerhauser posted figures that I'd missed (glossed over or mis-read) or didn't have:
12-60 (!) metric tons per hectare (5.4-27 short tons/acre).
"17.4 million BTU per metric tonne" (15.8 million BTU/short ton)
Switchgrass is capable of yielding upwards of 10 short tons/acre, so the performance of Miscanthus
is less impressive than it first appears; still, 27 tons/acre is nearly twice the best prospective yield I've seen for switchgrass. However, such figures appear exceptional and may not be available absent very favorable conditions. If it is possible to get a consistent 13.5 dry tons/acre from a grass crop and it produces 15.8 MMBTU/ton, the annual available energy over 3 million acres would be 640 trillion BTU or 187,000 million kWh thermal. The electric production would be 62,500 million kWh from a 33% efficient steam plant, or 75,000 million kWh from a 40% efficient combined-cycle plant. If 30 million tons of corn stover is added to the grass and it has a similar energy content, the total electric output would be sufficient to supply Illinois' 2001 requirements.
Over at The Energy Blog, zinc got a mention... but only as a way of making hydrogen. I took issue with the concept of hydrogen as the best product:
of zinc oxide from solid zinc is 84670 cal/mol; the ΔHf
of water is 70600 cal/mol, so the conversion from metallic zinc to hydrogen is about 83% efficient. PEM fuel cells are roughly 60% efficient, so the overall efficiency of the zinc-hydrogen-PEM FC system is just about 50%.
According to Electric Fuel's published figures for their electric bus system, the efficiency of a zinc-air FC is about 62%. That's 24% more energy out of a given amount of zinc than you get by taking a detour through hydrogen.
Hydrogen is a boondoggle.
Posted 2005-Sep-15 at Green Car Congress in a story about hybrids, drifting to the suitability of zinc-air cells for running semi-tractors:
Well, let's see. If you can devote 7500 pounds of a tractor to its combined "fuel" and "engine" (electric motors are light) and you use Electric Fuel's bus cells
, you'd be able to carry 38 of them. Total energy would be 38 * 17.4 kWh = 661 kWh. If you did some aerodynamic cleanup to let the semi achieve 10 MPG and its engine efficiency is 35%, it would be using 1.5 kWh/mile  and the batteries would allow 440 miles of range. That's not much compared to what you'd get from 200 gallons of diesel at even 6 MPG, but it's clearly not impractical.
If you combined this with a dual-mode (road/rail) system like Blade Runner and electrified the rail system, you'd have unlimited range on the rails and several hundred miles off-rail range. That's sufficient for most everything.
 If diesel fuel has 19,110 BTU/lbm and 7.67 lbm/gallon, each gallon has 146,600 BTU/gallon (42.9 kWh/gallon). Conversion at 35% efficiency yields 15.0 kWh/gallon, so 10 MPG would be equivalent to 1.5 kWh/mile.