Subject: Re: Optical concentration of solar energy

From: [email-masked] (Nick Pine)
Date: 15 Apr 1996 07:07:30 -0400

David Jones <[email-masked]> wrote:

>...does anyone know of a source for a magnifying lens to concentrate sunlight
>in a straight line, instead of the usual circular form.

Edmund Scientific and 3M sell cylindrical lens material, but for a large area,
perhaps a linear parabolic reflector would be less expensive, eg this solar
greenhouse and water heater that might be built quickly for less than $1,000
in materials to provide winter space heating and domestic hot water and fresh
vegetables and flowers for a nearby home or the urban building or swimming
pool underneath a flat roof. 

       .                                     ---
               .
      .             .
                        .
 <- S.                     .                 12'
                              .   y
    .    (32' long)             . |     z
       /                         .|   /  
   . /                            . /
x <...........................f............. ---
              water trench->.     .
                             .....

The reflective sheathing might be screwed to 16' kerfed 2 x 4s bent into a
4.5:1 concentrating parabolic shape, with the reflective surface inside the
greenhouse. This reflector would have a focus at about f=2.68' (y^2 = 4fx).

Howard Reichmuth, PE, designed the Ecotope greenhouse, a similar structure
built 20 years ago near Seattle. He's built several steam generators with
concentration ratios of 5 or 6. His advice: "Don't stand in the focus.
I almost melted a pair of boots."

US Patent number 4,129,120, expired 12/12/95, inventor Norman Saunders, PE,
describes an efficient concentrating steam generator using a flat transparent
boiler with a dark grate inside, just under the water surface. Copies of US
patents can be obtained for $3 each from the Superintendent of Patents and
Trademarks, Washington, DC 20231.

>	The idea is to use for domestic heating and/or energy generation a 
>linear shaped lens to concentrate solar energy on a pipe where the focus 
>of the lens corresponds to the shape of a pipe ie. a line of focused 
>sunlight instead of a spot.

Duffie and Beckman's _Solar Engineering of Thermal Processes_, 2nd edition,
Wiley, 1991, covers the design of these and other _non-focusing_ Winston CPCs,
concentrators which accept all light coming from within a certain beamwidth...

>I would guess this to be a cheap item to produce if someone is doing it...

Richard Komp is doing it at SunWatt, RR 1, Box 7751, Jonesport ME 04606,
207-967-5945. His hybrid 2:1 concentrating solar panels produce 150 Watts 
of electric power and 1600 Watts of water heating power simultaneously,
rounding up half the usual number of photovoltaic suspects. 

>	I live in Texas and have an abundance of sunlight for most of the 
>year, so would like to experiment with saving energy and money.

Hey, c'mon over to the Renewable and Alternative Energy Conference in Abilene
>from  4/22-23, where I'll be holding forth on solar closets and sunspaces for
house and water heating. The cost is only $40 to cover meals. Call Johnnie 
Lou Avery at 915-235-7332, or send her a check at Texas State Technical
College, 300 College Drive, Sweetwater, TX 79556.

Or come to Roland Winston's concentrator workshop in Philadelphia on 5/3,
>from  10:30-3 PM. $50/person by 4/22, ($15 for students, not including lunch.)
Send your checks or Faxes with credit card numbers to Kathleen DeLuca at
The Franklin Institute, Benjamin Franklin Parkway at 20th Street, Phila, PA
19103-1194, Fax 215-448-1364. Mike Nicklas, AIA, Bill Marshall, NREL,
Robert Bickmire, Institute for Energy Conversion and Morton H. Lerner,
Engineering Consultant will also be there.

Nick

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From: Ken Starcher <[email-masked]>
Date: 16 Apr 1996 15:10:19 GMT

Check out Entech, they have solar collectors that are 
long troughs and use a thin film to focus light in the 
center of the valley, then they rotate the entire tube 
to track the sun.

ENTECH
P.O. Box 612246
1015 Royal Lane
Dallas Ft. Worth Airport, Texas 75261

PH 214-456-0900  fax  214-456-0904

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From: [email-masked] (Fred)
Date: Tue, 16 Apr 1996 16:38:46 GMT

>>in a straight line, instead of the usual circular form.

There is an interesting product made in Japan called the "sun flower"
that focuses sunlight for transmission through a fibre optic cable for
lighting indoor/underground areas for growing, etc.