Re: [asa] UN Downgrades Man's Impact On The Climate

From: Randy Isaac <randyisaac@adelphia.net>
Date: Sat Dec 16 2006 - 19:13:41 EST

I asked our former council member Ken Touryan about this 40% measurement since he's at the DOE Renewable Energy Lab. His reply:

The trick is that it is a triple-junction cell,GaInP(1.8ev)/GaInAs(1.4ev)/Ge(0,7ev) under 10 sun concentration. It is very efficient but expensive. Best use is for space applications where volume is a premium and a $50-$100/watt is an acceptable price. Eventually it may compete with the less efficient cells
Cheers
Ken
  ----- Original Message -----
  From: Jim Armstrong
  To: asa
  Sent: Friday, December 15, 2006 12:14 PM
  Subject: Re: [asa] UN Downgrades Man's Impact On The Climate

  The 40% figure was recently reported by Boeing Spectrolab and verified by the US dept of Energy's National Renewable Energy Lab. For example:
  http://news.monstersandcritics.com/energywatch/renewables/features/article_1233268.php/Solar_World_An_efficiency_milestone
  No question as to the continued use of liquid fuel for some time.
  The delivery infrastructure is a significant issue, even if the conversion efficiency of a source is reasonable.
  The infrastructure exists (as is the case for petrofuels) for electricity. For direct conversion electricity, there is no fuel-to-deliver-fuel overhead.
  That's kinda nice!

  JimA

  Don Winterstein wrote:

    Don't know what you're referring to with the 40%. In any case, cars are likely to need liquid fuel for some time to come. How efficient cellulose will be is unknown at present; it'll depend on the biochemists.

    Don

      ----- Original Message -----
      From: Jim Armstrong
      To: asa
      Sent: Wednesday, December 13, 2006 8:18 AM
      Subject: Re: [asa] UN Downgrades Man's Impact On The Climate

      But does it not seem unlikely to be able to hit an overall figure anything like the 40% direct solar energy conversion efficiency recently reported? JimA

      Don Winterstein wrote:

        The important thing about this recent Bus. Week article is that it doesn't concern such intensively farmed crops....

        To clarify, the really important difference between use of corn and soybeans and use of cellulose is not that corn and soybeans are intensively cultivated while prairie grasses are not. It is that cellulose constitutes a far larger fraction of all plant material than the starches, sugars and oils currently being used from corn and soybeans. So if you can figure out an efficient way to use cellulose, you have a vastly larger reservoir of useful plant material at your disposal and the consequent possibility of making a serious dent in oil imports.

        The solution to this problem is a biochemical one and hence--unlike getting useful energy from fusion--within the realm of near-term possibility. The amazing things that biochemists have done gives confidence that they'll be able to solve this as well. The solution will have a major effect on agriculture and the rest of the economy.

        Don

          ----- Original Message -----
          From: Don Winterstein
          To: asa ; Ted Davis
          Sent: Monday, December 11, 2006 7:29 AM
          Subject: Re: [asa] UN Downgrades Man's Impact On The Climate

          The advance publicity for Pimentel talks about intensively farmed crops such as corn and soybeans. There's long been a concern that these won't be economical long-term--although I've read that those who are producing the ethanol from corn say their processes are economical by a sufficient margin.

          The important thing about this recent Bus. Week article is that it doesn't concern such intensively farmed crops but plants like switchgrass and the Asian grass miscanthas, which don't need to be cultivated but only harvested from existing or new prairies. Also, waste paper, wheat straw, etc. Anything with cellulose or hemicellulose. The corn and soybean processes in contrast make use of sugars and oils. The big problem at the moment is finding an efficient way to break down cellulose into its constituent sugars. The article discusses several alternatives that are being explored.

          There certainly will be important problems they're probably minimizing at the moment. For example, how many times can you harvest grass before you have to apply fertilizer?

          Don

            ----- Original Message -----
            From: Ted Davis
            To: Dawsonzhu@aol.com ; asa@calvin.edu ; dfwinterstein@msn.com
            Sent: Monday, December 11, 2006 6:28 AM
            Subject: Re: [asa] UN Downgrades Man's Impact On The Climate

>>> "Don Winterstein" <dfwinterstein@msn.com> 12/11/06 9:03 AM >>>writes:
             Don't forget too, that there are other looming issues such as energy.

            The current issue of Business Week (Dec. 18) states in an article entitled
            Put a Termite In Your Tank, "If efforts [involving 'bio breakthroughs' for
            digesting cellulose] can be scaled up efficiently, America's forests,
            agricultural waste, and 40 to 60 million acres of prairie grass could supply
            100 billion gallons or more of fuel per year--while slashing greenhouse gas
            emissions. That would replace more than half the 150 billion gallons of
            gasoline now used [by the US] annually...."

            Lots of "ifs" there, but still a rather remarkable statement. Pilot
            facilities are already being built.

            Ted responds:
            A couple of months ago, I heard a lecture by David Pimentel that all but
            rejected this approach as unrealistic, both economically and in terms of
            energy production. Advance publicity is here:
            http://www.dickinson.edu/news/nrshow.cfm?981

            Ted

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Received on Sat Dec 16 19:14:17 2006

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