■ate
Weather Condition
Outside Temperature
Time
Oven temperature
1 ---------------------------------------------------
Remarks
Place the oven thermometer inside a zip-lock bag and record the temperatures. What is your observation?
2. Heating food
Although your Solar Oven is just a small
model of a real solar oven, the temperature inside could reach 70°C (158°F)
or higher on a sunny day—that's high enough
to melt some types of food. Place a piece of cheese or chocolate on a piece
of aluminium foil, and wrap the foil over the
food to form a packet. Place the packet inside the oven. Put the oven in the
sunshine (see setting up instructions above).
After a while the chocolate or cheese should become soft.
3. The egg cooking experiment
Warning: Do not eat the cooked egg from this
experiment. The Solar Oven may not cook the egg evenly or thoroughly, and an uncooked (or soft boiled) egg may contain
harmful bugs. Adult supervision is needed.
You can also use your Solar Oven to
demonstrate some "rear cooking. Due to its small size, your miniature oven is ideal for demonstrating how an egg can be
cooked by sunshine. Wrap a small egg in the
large square black paper provided. If your egg has been in the fridge, leave it somewhere at room temperature for a while
as a cold egg will require a longer cooking
time, and dry the egg shell to get rid of any condensed water. Place the egg into a small zip-lock bag, place the bag into the
oven and put the oven in the sunshine. If you
are using an oven thermometer, you can watch the temperature rise. On a day with hot sunshine, the egg should be cooked
to a "soft boiled" state in 3 or 4 hours.
Try to improve your Solar Oven so that an egg
can be cooked more thoroughly and more quickly. You can enlarge the reflector with aluminium foil so that more of the
Sun's energy is collected. Or you can add
insulation so that more heat is retained inside the oven. For example, you could cut a square opening (slightly larger than
the oven body) in one side of the package box,
and place the oven into the openin.
The space between the oven and the package box will act as a layer of insulation. Try to think of other ways of insulating the box and compare the eggs "cooked" in the non-insulated and insulated ovens.
IOW DOES YOUR SOLAR OVEN WORK?
Your Solar Oven works by collecting and concentrating heat rays from the Sun. All rays that hit the shiny collector are reflected down into the oven, heating the oven's inside. The black paper absorbs heat that hits it, which
helps to warm the air inside the oven. Because the collector covers an area greater than the oven body, the Sun's rays are concentrated in the oven. Food inside the oven is warmed by rays that hit it, and by hot air inside the
oven. The food absorbs the heat, wh ich makes it cook. Although quite small, your Solar Oven demonstrates the working principles of a real working solar oven or solar cooker, some of which can reach temperatures high
enough to bake a cake or cook a meat steak.
TROUBLESHOOTING fl
If your solar oven does not heat up:
•
Check if there is enough sunshine. The Sun is at its hottest in the few hours around midday - so from about 10 a.m. to about 2 p.m. Try the experiments during these hours. Or try it again on a sunny day.
•
Make sure that the top of the oven is facing the Sun directly so that the oven can collect the maximum number of rays. And remember to adjust the position of the oven
as
the Sun moves across the sky.
•
Avoid doing the experiments on cold or windy days as the air will remove heat from the oven.
•
You can also seal the edges of the oven box with sticky tape or wrap the whole oven body in kitchen food wrap. This will help to prevent hot air escaping.
FUN FACTS
•
A solar cooker/oven is a simple reflecting device that collects heat from the Sun and focuses it onto food to cook the food.
Summary of Contents for Solar Science
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