Uses of Solar Energy

TO TELL TIME

    As the Sun appears to be lower or higher in the horizion, and as Earth spins from West to East (so that the sun appears to moving from East to West) a stick's shadow will clearly change length and position throughout each day and through the year. By studying and reflecting on that stick's shadow, you will come to understand our path, as the Earth spins, and orbits the Sun.

    The gnomon casts a shadow.

TO COOK

If you go to
http://www.solarcooking.org/plans/
you can see lots of cookers!
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As well, take a look at the work students are doing at the Miami Country Day School. Excellent introductory movies and slide show, great humanitarian work abroad, using solar cookers.

Teachers' Resources for teaching solar cooking are also at this site.There are also printable worksheets, and solar tunes provided for singing while you work!

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There are lots of variations possible for solar cookers, and lots of room for innovative improvement.
It's a field in which an amateur may make a significant contribution. Note that the simple reflective cone has re-appeared as a simple but effective way to concentrate solar energy. And who would have thought of an inner tube and a pane of glass? The Cook-Kit has proven to be as good a design as any. Lately it's been noted that using a circle of chicken wire as a base for the pot allows solar radiation to strike the bottom of the pot, increasing temperatures and decreasing cooking times.

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Not all solar cookers are portable for outdoors. Provided you're near the equator, consider building a "through-the-wall" solar cooker onto your next home. Pictures of Barbara Kerr's wall-oven.
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Or keep up to date with the good work Solar Cookers International is doing around the world by reading their latest newsletters.

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REVIEW OF SOLAR COOKER DESIGNS
For a survey of the thoughtful designs that have arisen from our desire to cook with sunlight, please visit the historical and highly informational site of Dr. Ashok Kundapur of India. His Web site "presents about 56 major designs , 59 variations and 66 drawings of solar cookers."

Sun Ovens are Wonderful!
[Part of the Solar Havens site, with accounts of building a solar-powered strawbale home.]

Joe Radabaugh  explains how to make a solar cooker from cardboard boxes.

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If you'd like to go directly to a fellow who sells excellent plans/templates for this solar hot-plate cooker
($12 U.S.) (along with recipes);
 

and 
one of the best solar-cooking books,
"Cooking With the Sun: How to Build and Use Solar Cookers" by Beth & Dan Halacy ($9.95 U.S.),
showing how to make solar ovens, and including lots of recipes;
please visit:  http://home.ix.netcom.com/~jdhowell

Subject:  SOLAR project for a 10 Year old. Dad, get out the Solar Cooker! The Sun is shining!
From: Carroll D Hampleman <diysuntracker12vdc@juno.com>

    Dad, look what I have done !  I have ordered two simple "things": (no batteries, few ounces. less that $25.00).  Hooked together,  you can now "read" how hot the Sun is, in units of  "BTU per Sq. Ft. per Hour (BSH)", or in units of "Watts per Square Meter (WSM)".
    Both of these simple "things" can be ordered from one Supply House:  "H & R  Company", 1-800-848-8001, (with a valid Credit Card). First item:  "Solar Mini Panel" - Item # SW-005,  for $8.50. This item will detect the Sun Rays as electricity in units of "milliAmps".  Note: This is sized 3 & 1/8th inch by 1 & 7/8ths inch by 1/4 inch, and will read  400 milliAmps  at "FULL SUN".
    I have "blocked off" (using vinyl electrical tape) a full 5/8 of one inch, OF ITS  LENGTH, (so that it will detect FULL SUN as : "3l7.l  BTU per Sq. Ft. per Hour, (BSH)", or  same as  "1,000 WATTS per Square Meter (WSM)". This is considered to be "FULL SUN", at the face of the Earth.
    The second item is a meter, to read out this electricity (in "milliAmps") which we can  call "BTU per Sq. Ft. per Hour, (BSH)".   Item #S3-190,  a 2 & 1/2 inch  meter for $16.95, or  Item #S3-191,  a  3 & 1/2 inch meter for  $19.50.

    I have these two "things" hooked together,  and I can now just  LOOK  at the meter,  and read DIRECTLY the Energy of the SUN!  in units of "BTU per Sq. Ft. per Hour (BSH)" or, can be labeled, as:  "Watts per Square Meter (WSM)".

TO PUMP WATER

TO PURIFY WATER

By Evaporation (Solar Distillation):  Solar energy can heat water to vaporization. (It happens all the time, with our clouds.) Heating water to vaporization leaves behind many impurities. Water vapour accumulates on a cooler surface, and trickles toward the center of the Earth (gravity) into another (clean) water container.
    A very simple solar still can be formed by digging a hole in the ground, placing a cup in the bottom of the hole, and covering the hole with clear plastic. Put a small stone in the center of the plastic, so that the condensed water vapour drips into the cup. There is always some moisture in soil. Even in the desert, this will apparently save your life. Want to try it?

By Ultra-Violet Irradiation  - Remember that the shorter the wavelength, the more energetic the radiation? Recall how ultra-violet light from the Sun can cause bad sun-burns, or, ultimately perhaps skin cancers, by damaging our skin cells? We can also use that energy to kill bacteria directly. In a sense we do that when we hang laundry out to dry in the sun...we are also purifiying the laundry with ultraviolet (think "ultra-violent") radiation. There has been some research done suggesting that putting bacterially-contaminated water out in clear plastic bottles in bright sunlight will kill the bacteria in it, making it safe to drink.

TO HEAT  WATER

    Although pumps are usually used to circulate the water, solar water heaters can also rely on what is called "thermo-siphoning" (and which might more accurately be called "density-displacement" towards the center of the Earth's gravitational field). Heated water, less dense because occupying more volume per unit mass, is displaced by denser colder water, and so rises against the gravitational force-field (we call that "up").
   Buckminster Fuller would have called that "out"...out from the centre of the Earth. Bucky had it right...Bucky was on the ball...the rotating ball we call "Earth".
    In the case of simple "thermosiphoning" batch heaters, the hot water tank is above (out from) the cold water source.

    Passive solar water heaters can be inserted into a pressurized water line fed to and from the sunny roof, to operate as pre-heaters for regular hot water tanks. These are suitable for 3/4 of the year on the Pacific Coast, saving gigajoules of hydro and fossil fuel energy and preventing the emission of tons of carbon dioxide each year.

    Where large volumes of heated water are required, solar water-heating rapidly makes financial and environmental sense. Some hospitals and large hotels use solar water-heating for washing sheets and laundry. Car washes and swimming pools can heat water with solar energy. Most buildings in Israel have solar water heaters on their roofs.

Flat Plate Collectors: Solar radiation shines through a glass cover to black absorber fins attached to thin pipes laid out in an insulated box. Sometimes glycol is used as a transfer fluid (to prevent freezing problems) and the heat must be transferred by a heat exchanger to water at the other end of its loop. Solar pre-heated water in the hot water tank saves substantial fuel.

Evacuated Tube Collectors:  Solar radiation shines through an enclosing evacuated glass tube, and is absorbed by black metal fins attached to a thin central tube containing a small amount of water under low pressure. Because the outer tube is evacuated, heat cannot escape into the atmosphere from the warmed metal by conduction or convection, and radiational losses are blocked by the glass. So the water at low pressure in the small central inner tube is heated to vaporization. Vapour rises to the top of the pipe, which is a metal tip. This hot metal tip is clamped into a manifold containing a flowing liquid (such as glycol or household water). When the vapour condenses,its heat is transferred through the metal tip and manifold into the liquid. This heated liquid (glycol or water) can be pumped through water pipes into a house to pre-heat domestic hot water (laundry, showers, washing), or to provide heat for circulating liquid home-heating systems, such as baseboard radiators or radiant floor heating.]

TO HEAT AIR

To Dry Food

To heat homes and industries

    By passing air over solar-heated metal, air can be pre-heated for a home or a factory or a grain-storage bin (crop-drying), saving on fossil-fuel useage. Canada's own patented Solarwall (by Conserval) is the world's leading example of this.

  Solarwall not only absorbs solar energy on its dark outward-facing side (transferring solar heating to air at an efficiency of 75%) but, with its shiny backside, also reflects radiated heat losses from the building back toward the building. R-value?  55.

Back to Basics:  Build Your Own Solar Air Heater

    Using tin snips or a large sheath knife, cut into the top of a can, making four or five "pie" sections. Bend these down into the can at an angle. Cut completely around the side of the can near the bottom, and remove the bottom. After several (or many) cans are prepared this way, stove-pipe them together...the bottoms will jam onto the tops. Lay several "pipes" out into an open box, spray-paint them black, and cover the face of the box with plastic or glass, leaving openings at the bottom of the box (to let cool air in) and the top (to let warmed air out). [Design by Dennis Fath of H.D. Mechanical in Edmonton, Alberta, Canada.]

TO EXPLORE OTHER PLANETS