Hank.Walker%CMU-CS-UNH@sri-unix.UUCP (08/09/84)
The talk about the cells costing a tenth what silicon solar cells do must be bunk. Current module costs are maybe $5/W, so he is talking $0.50/W, or $5/wafer. The cost of silicon cells is primarily the crystalline silicon. The cost of the antenna cells is the complex lithographic step. Rectifiers will probably have to be integrated onto the same wafer, so an alignment problem is created, and it looks a lot like you're making an integrated circuit. Note that according to the article, a prototype won't be available until next year, so the process must be rather difficult.
hutch@shark.UUCP (Stephen Hutchison) (08/20/84)
< The robot doesn't seem too energetic since it got a tan > Has anyone looked into organic solar collection? Plants do a real fine job of collecting and storing solar energy; does anyone know how efficient they are (not 100% by any means, since they are usually sensitive in a fairly narrow bandwidth of yellow-green) ?? An organic compound engineered to translate sunlight into ATP and another that turned ATP into electricity would be an interesting way to power a car. . . OK, I know, this is all just a bit beyond current state-of-the-art. But not too far, I suspect. Hutch
mcgeer%ucbchip%Berkeley@sri-unix.UUCP (08/22/84)
From: Rick McGeer (on an aaa-60-s) <mcgeer%ucbchip@Berkeley> There's a short discussion of plant efficiencies in Pournelle's "A Step Farther Out". I loaned my copy out, so I don't have it with me, but as I recall the figures he used were certainly under 10%, and (I'm pretty sure) under 5%. The great thing, though, is that we can probably use genetic engineering to double plant efficiencies. Plants also store energy well. Rick.
Woody.pasa@XEROX.ARPA (08/23/84)
> Has anyone looked into organic solar collection? Plants do a real > fine job of collecting and storing solar energy; does anyone know > how efficient they are (not 100% by any means, since they are usually > sensitive in a fairly narrow bandwidth of yellow-green) ?? Plants are around 15-20% (as far as my memory tells me; it's been a long time since my biology), and no-one really has a definite idea exactly how a plant manages to convert light to ATP. There's a lot of theories, but nothing really concrete. Photosynthesis is a fairly complex chain of events which occure in most plants, and some of the theories do suggest a sort of compound which gain an electrical potential (which is then converted into the chemical potential needed to convert ADP to ATP). It may be possible to create a process which converts this molecular electrical potential into something useful, but that's many, many years off. (Even if the electrical potential of P700 and related catalysts in photosynthesis does exist, even if the chemical process can be imitated, even if the efficiency of the plants can be achieved, even...) It's easier to burn alcohol. - From the scattered remains of Bill Woody
andy@istbt.UUCP (Andy Greener) (09/17/84)
[everyone else seems to be wary...] hutch@shark.UUCP writes: > Has anyone looked into organic solar collection? Plants do a real > fine job of collecting and storing solar energy; does anyone know > how efficient they are (not 100% by any means, since they are usually > sensitive in a fairly narrow bandwidth of yellow-green) ?? > > An organic compound engineered to translate sunlight into ATP and > another that turned ATP into electricity would be an interesting > way to power a car. . . What colour are your plants in Oregon Hutch? Ours are green and yellow because they DO NOT absorb green and yellow light. You must have an interesting garden! The majority of the spectrum is absorbed except those wavelengths around 550 nm (green), 600 nm and 640 nm (yellow). However the efficiency is not great (I'm not sure of the exact figure). Photosynthesis is a two-stage process; the light stage is the photo-chemical reaction with sunlight that splits water and provides the free hydrogen for the second (dark) stage to turn into carbohydrates. The first stage produces ATP anyway to power the second stage (nature did the engineering already!). The light stage produces faster than the dark stage can cope with so periods of darkness are actually beneficial to the process. However, a problem with the utilisation of this process is its extreme sensitivity to temperature and the fact that because enzymes are involved any temperatures above about 40 Centigrade will kill it due to protein denaturing. Andy Greener Imperial Software Technology London, England ...!vax135!ukc!qtlon!ist!andy ...!vax135!ukc!qtlon!ist!istbt!andy