Solar Nest

An affordable solar box style cooker can be constructed from
transparent sheet plastic (polyethylene), some fibrous
material, and four reasonably straight sticks (or possibly the plastic could be secured on top with small stones). The
oven comprises a “nest” of fibrous material- in this case
shredded coconut husk- about 200 mm high with a cooking
cavity approximately 450 mm diameter and 150 mm deep.
Commonly available transparent sheet polyethylene was stapled to a 500 mm by
500 mm frame made from 40 mm by 20 mm battens (like a
double-glazed window with an effective aperture of about
0.25 ), which was placed over the cavity. The cooking
vessel was a 200 mm square pressed steel pan 50 mm deep.
A small sheet of the same plastic formed a lid to the pan to
maximize direct solar gain to the pan and to minimize heat
loss by evaporation/convection.
==Testing==
A series of cooking tests were conducted on clear sunny
days during March 2007 in Perth, Western Australia
(Latitude 32° S) with maximum air temperatures of .
A mass of water plus grain of 1 kg was placed in the pan,
and placed in the cavity at 11am local solar time. In all cases
satisfactory cooking was achieved before 15:00 local solar
time. A dish of chicken and vegetables and a 1kg leg of
lamb were also fully cooked.
The tests demonstrated that by using an aperture of
0.25 , practical cooking temperatures and times can be
achieved with transparent sheet plastic without the need for
complex reflectors to increase the effective aperture or glass
to increase the heat trapping.
The “nest” eliminates the need
for a box, and could be made from any locally available
fibrous material, such as bark, grass, straw, cloth or
sterilized animal manure. While the performance of the
oven can be enhanced by being deeper, blackened and by
using one or two sheets of glass, these tests demonstrated
that satisfactory cooking can be achieved with as little as
50 cents (US) of sheet plastic in a wide range of circumstances temperatures and/or shorter cooking times) would always be
desirable within cost constraints.
The test was standardized using an electronic probe
thermometer immersed in 1 liter of water in the pressed
steel pan used above. Temperature measurements were
taken every 15 minutes. Temperatures of were
obtained in the cooker without the pan of water.
The first enhancement was to place a black steel plate under
the pan. As this showed a marked increase in performance,
it was used for all further tests, which were:
•
Single glass sheet
•
Double glass sheet
•
Double Tedlar® plastic sheet
The results for these tests are shown in Fig. 3. All glazings
achieved the cooking threshold within 3 hours, with
the black metal plate making about difference, which is
an important increase at these temperatures. The single
glazing, double glazing and double Tedlar® achieved the
 threshold at least an hour earlier than the double
plastic and achieved maximum temperatures of about 
higher than double plastic. Tedlar® was chosen as it is
durable at high temperatures and has low infrared
transmissivity than polyethylene.
==Articles in the media==
*September 2010: Solar Nest, an idea for providing cheap, clean water for Pakistan - Innovations
*May 2007: A low-cost solar oven - ABC Rural
==See also==
*John Barker
*Solar puddle
==External links==
*The Solar Nest - A very low cost solar cooker - Dr. John Barker
==Contact==
Category:Solar cooker designs
Category:Australia
Category:Western Australia
Category:Solar box cooker designs
Category:In-the-ground solar cooker designs