the save-heat cooker and update on the byu solar funnel cooker/cooler
we have continued to develop the brigham young university solar funnel cooker/ cooler, and this report provides a brief update. the original report is found at http://solarcooking.org/funnel.htm.
1. new support for the cooking vessel or jar.
originally, we used a block of wood to support the canning jar in
which food was cooked or water pasteurized. but this support blocked the
sun's rays from hitting the bottom of the vessel. so we have experimented
with other supports. two work particularly well, as shown in the photo.
the first is a cylinder of rabbit-wire, formed to hold the canning jar
snugly. the cylinder is approximately 10 cm diameter and 5 cm high. about
2.5 cm down into this cylinder, we placed an "x" formed with wire, to
support the jar. this wire-cylinder support allows sunlight to hit all
sides of the jar, including the bottom. the second support is simply a
large "x" formed from high-heat plastic or from a metal. with either
support, solar heating of the jar and its contents takes place very rapidly.
the jar-on-support is still placed inside an oven-safe plastic bag to take
advantage of the greenhouse effect, as explained in the original report.
2. reduced angle for the funnel.
the original report describes a large solar funnel, having a 60-degree opening angle. our ongoing experiments show that a reduced angle of approximately 45 degrees allows about 10% faster solar cooking. such a funnel is shown in the second photograph. start with the funnel described in the original report, then simply bring the sides a and b together with a 20-cm overlap at the top of the funnel. this makes a funnel with steeper sides.
3. save-heat cooker (a retained heat cooker for canning jars heated using the sun or fire)
the third photograph shows the save-heat cooker which we have designed and built. the box is made from a polystyrene cube, 30 cm on a side. we have drilled 4 holes each about 10 cm in diameter into this block, so that each holds a canning jar. then a lid fits over the top to hold in the heat.
when a jar is placed in the solar funnel cooker, a maximum
temperature of about 110 degrees c is reached in approximately 45 minutes
(depending on solar conditions). then steam is released around the rim of
the canning jar, which becomes an inexpensive pressure cooker. but the jar
will not get hotter � so one takes the jar out of the cooker (with a gloved
hand) and places it into the save-heat box. our experiments show that the
temperature drops slowly in this box, about 5 degrees c per hour, so that
cooking continues for 4 hours or so, without a heat source. in this way,
one can prepare up to four quarts of food per save-heat cooker at mid-day,
and have the food cooked and hot for the evening meal! or, if desired, the
food will keep in the box overnight and be ready for eating the next
morning. thus, a solar cooker can supply food for mid-day, evening and the
next morning, as desired. (another design of the save-heat cooker holds up
to seven quart-sized canning jars.)
the save-heat cooker is particularly useful for foods such as beans which take a long time to cook. food heated using a wood fire could be likewise be placed in a jar, and then this jar placed in the save-heat box, in order to save fuel-wood consumption, and cooking time and effort. the box can be cheaply molded out of polystyrene or styrofoam or other material, so long as it is a good insulator and capable of withstanding temperatures of around 110 degrees centigrade.
4. funnel-cooling during the day.
we noted in the original report that the funnel works as a cooler at night, by reflecting heat out of the canning jar and up to the cold sky. we have found that this works during the day also, when the funnel is pointed to a region of the sky away from the sun (and buildings, etc.). we found cooling of about 12 degrees f., compared with about 20 degrees cooling at night. to achieve this, the jar was placed on a rabbit-wire support as described above, and housed in two cheap, clear polyethylene bags, such as used for vegetables in the united states.
5. hot-and-cold running water.
by placing a large funnel around a water barrel, it will be solar-heated during the day, or cooled at night. thus, having two barrels each with a funnel-like reflector around it, and covering one when not sunny and the other whenever it is sunny, one can have hot and cold water. these barrels could be placed on a platform or roof to provide hot-and-cold running water!
we are hopeful that these developments will help many people, especially those in areas of the world where electricity or even wood or gas are in short supply, if available at all. these ideas are offered freely to all.
prof. steven e. jones, colter paulson, jason chesley, will shakespeare and jacob fugal.