|
|
re: solar collectors
6 apr 2000
dw wrote:
>i understood that stirlings were inefficient but i didn't realize how much.
upping the temperature helps. collecting heat at 500 f (260 c or 533 k)
with a linear concentrator and a 30 c (303 k) cool sink makes the optimum
heat engine temp sqrt(533x303) = 402 k (129 c), with a max theoretical
recovery fraction of (533-402)x(1-303/402) = 0.323. john corey suggests
that a reasonably-priced heat engine might turn 16% of that collected heat
power into shaft power, while also heating a house.
compare this to ordinary pv panels with silicone potting and water cooling
and 2:1 non-tracking solar concentration that increases their efficiency
and cost-effectiveness without the danger and complexity of steam, hot oil,
moving parts, fires, and explosions...
paavo kousa's us patent no. 5,851,309 (about 100 pages, issued 12/21/98,
available from the superintendent of patents and trademarks, washington,
dc, 20231) describes a number of solar attic concentrators, including some
inexpensive versions with downward-facing linear targets over mylar film
that is stretched in a catenary to approximate a parabola. some are non-
tracking. others track by tightening the film with an upper roller and a
stepping motor.
norman saunders has a patent on another concentrating low-loss steam
generator with a novel transparent bottom and a water flow scheme
that minimizes heat loss.
nick
|
|
