Original Message: ----------------- From: hkhenson [email protected] Date: Tue, 13 Jan 2009 20:17:41 -0700 To: [email protected] Subject: Re: biofuels and Li Batteries.
At 01:00 PM 1/13/2009, "Dan M" wrote: >>I agree, but bioengineered fuels are not ethanol. There are algae that >>exist right now that produce aviation fuel with 1000x the efficiency of >>ethanol. >I have a hard time with this statement. Corn comes fairly close to >3% sunlight to fixed carbon. Well, let's look at the official ethanol numbers. If you assume only 5 hours of the solar flux per day, there is about 3.6e7 MJ/acre available per acre of land per year. Corn yields about 150 bushels/acre and we produce 2.7 gallons of ethanol per gallon. With 89 MJ per gallon of ethanol, that gives about 3.6e4 MJ/acre for the ethanol. That's a factor of 1000, and would require that the algae be perfect, which I wouldn't expect. But if you put in 2/3rds of the energy available in ethanol in the process of making ethanol (which is not a bad estimate, it use to be worse....>100% of the output energy was lost in process), then the algae would have to be 33% efficient. Plus, I'm guessing that the lab conditions they worked under were pretty ideal, and that they assumed that the algea farms would be at lower lattitudes than Iowa...so they upped the values from 5 hours to 6 or 7. The factor of 1000 is probably a streach. When I wrote it, I wasn't thinking of a big time production reaching it. But, let's look at what just a factor of 100 would do (which puts the algae at 3% efficiency with 5 hours. We need all of the acres devoted to corn switched used for ethanol to get about 12% of the moter fuel. With a factor of 100, we're talking about 8% of the corn acreage as algae ponds. Since algae can grow in sea water, they can be set up using ocean water, removing the demand on fresh water resources for fuel. I'm not saying we can get there en mass. I'm saying, with bioengineering costs going down, it is possible that we can get there, and that we have gotten there under lab >No, there are breakthroughs in many fields that are never mass marketed. >What I am saying is that we don't know until we know. In my own career, >there have been many times, before I ran an experiment, I was pretty sure I >knew how something would work, but it didn't, and I had to scramble. Take >for example, scaling up the recent Stanford breakthrough of increasing the >Li-I battery capacity 10x. >Is that possible from an energy standpoint? Yea, I know of no fundamental physical laws that prohibit 100x or 1000x the energy densities. Now, there may be an upper limit to chemical storage, but fundamental QED doesn't limit it. If I understand correctly, they have increased the surface area by nanotech. That sounds logical to me. The references given by Rob discuss this work, so I'll leave my contribution to this bit. Dan M. -------------------------------------------------------------------- mail2web - Check your email from the web at http://link.mail2web.com/mail2web _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
