Limitations Of Solar Ovens
Solar ovens do not work at night or on cloudy days . Windy conditions reduce their efficiency considerably unless the oven is heavily insulated. When solar ovens are used to cook food over a period of several hours, someone must be present to reposition the solar collector to follow the sun as it moves across the sky . The largest barrier to solar oven use, however, is the perception that solar cooking is inefficient .
References
Capturing Extra Sunlight Energy
One or more shiny surfaces reflect extra sunlight onto the pot, increasing its heat potential. Mirrors, aluminum foil, Mylar, mirror-finish metals, chrome sign vinyl, and other shiny materials have all been used successfully for solar cooking, depending on the type of cooker and the environment in which it will be used.
- Main article:Reflective material
How Long Does It Take To Cook In A Solar Oven
Well, various factors determine how long it takes to cook in a solar oven. Some factors include the design of the solar cooker, the materials of the cooking ware, the weather, the type of food and the ambient temperature.
As the factors above vary, the cooking time of solar ovens varies too. In many cases, your oven will only be suitable for slow cooking. Nonetheless, you can use the following times as a guide while you cook with your solar cooker:
- Melted cheese, butter, omelet and baked egg typically cook in less than an hour.
- Grains, vegetables and pastries should cook in 2 to 3 hours.
- Soup and whole vegetables should be ready in 3 to 4 hours.
- Dried beans, pumpkins, and large dishes typically cook in 4 to 7 hours.
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Three Types Of Solar Ovens
Solar ovens utilize different designs to suit cooking needs and budgets. Broadly, they can be classified into three categories:
The panel design is the most basic, affordable, and easy to assemble among solar ovens. Reflector panels direct sunlight into an insulated box or pot, which accumulates heat till the pot is ready to cook.
These ovens, often DIY models employed by people in poorer countries, do not have the capability of reaching over 200 to 250 degrees of heat. They also tend to lose heat fast. As such, they may not be useful for significant activities in the winter months in North Americatheir limit may be boiling water and cooking simple dishes.
2. Box Ovens
Box ovens have grown extremely popular in India and other tropical countries. They are not very expensive, but usually have a more durable structure than panel ovens.
The reflectors in a box oven are of better quality than panel ovens. Specific designs allow angular adjustments to aid winter cooking when the sun placed lower in the sky. The central glass/plastic-encased box may be smaller, suitable for smaller quantities, or be expanded for larger quantities. Vacuum seals and non-reflective outer surfaces can be added to produce higher heat. Extra insulation can help maintain temperatures longer.
3. Parabolic Ovens
Parabolic ovens are the Cadillacs among solar ovens often used for cooking in large batches and are used commercially in countries such as China.
Reflection & Ray Tracing
To generate functional cooking temperatures from the sun, you are going to need to gather or concentrate a lot of sun. Using mirrors and other reflective surfaces, we can move the suns rays around and increase their intensity onto a specific surface. By using aluminum foil, Mylar, or mirrors, solar ovens basically multiply the amount of sun on a cooking chamber to boost its efficiency.
Ray Tracing is a method of calculating the path of waves or particles through a system of regions by varying propagation velocity, absorption characteristics, and reflecting surfaces. Many conditions and surfaces complicate the analysis because waves and rays tend to bend, refract, and reflect off surfaces. Good, everyday examples of the complexity of ray tracing are radio, tv and cell phone waves, each with different parameters and affecting the way our receivers capture those waves for our use, which becomes very apparent when mountains interfere with them.
There are many ways to manipulate solar rays before directing them to strike an absorbing surface that can be heated. We carefully crafted the GoSuns reflectors to direct sunlight coming in from various angles to be centered onto the tube. Examine your GoSuns reflectors and see if you can make out any images your eyes rays should see your tube reflected just as the sunlights rays.
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How To Make Solar Ovens More Efficient In Winter
It becomes difficult to cook on winter days because the sun is closer to the other hemisphere.
To overcome this problem, you should tilt the sun oven so that it is almost in a horizontal position.
- You can get a plastic square from any hardware store and then tilt the sun oven after you place the square on the glass and then tilt the cooker at an angle so that you are no more in a position to see its shadow.
At this point, the cooker is properly focused to intensify the suns heat at a particular point to aid cooking.
For those food items which makes us wait longer, we can adjust the focus twice or thrice.
This would ensure that suns heat stays concentrated for a longer period of time. In this way, the muffins and cookies can be cooked easily.
You can overcome the problem of undercooked food by trying to cook between 10 a.m. to 2 p.m. during winter months usually.
So that the food remains hot for a longer period of time in winter months, you should try to insulate it by placing piles of old leaves or an old blanket around it.
The glass lid and the box of the oven should not even allow the passing of a thin sheet of paper. If it does then the heat retention design has not been taken care properly.
Building Your Solar Oven:
1. Using scissors or box cutters cut a flap on the side of your can. Cut along 3 sides. We cut the Nutrition label and that seemed a good size.
2. Fold the flap back so that it stands up
3. Cover the inside of the flap using aluminum foil to reflect the rays from the sun. Use tape to secure the foil to the flap. With a Pringles can it is already reflective on the inside, this is just for extra precaution.
4. Prop the flap open.
5. Place a sheet of black construction paper inside the can
6. If you have a second thermometer place it outside your solar oven so you can compare the two temperatures.
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Solar Ovens: Food Fueled By The Sun
JAH/iStock/Getty images
Solar energy isnt limited to home lighting anymore. Today, the sun can power nearly any device that would otherwise consume electricity, from phone chargers to refrigerators and even air conditioning units. But one solar appliance in particular can reduce power plant pollution and contribute to communities around the world all while serving up snacks.
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Its Usually Not About How Cold It Is But The Amount Of Sunshine
Unless the weather exhibits an unusually low temperature with high winds, in which case you have other problems, the use of a solar oven is not constrained by the winter coldquite the contrary. Solar ovens have been famously used on the slopes of Mount Everest. This is not only meant to be a cool storyit aptly illustrates the point we are about to make.
Solar cookers require strong, enduring sunlight to work which is why they cannot be used at night or on consistently overcast days. For optimum use, the daily amount of sunlight must exceed 4 KW hours per square meter. There is no reason why you cannot get an equivalent amount of sunlight during the winter monthsit depends on where you are located and how clear the skies are on any given day.
As a matter of fact, winter sunshine may produce direct, bright sunlight for several hours during the day in many areas, whereas the sun may be partially obstructed due to humidity and dust in the air. Solar ovens are frequently used year-round in tropical areas such as many in India and China.
In the Americas, there are typically multiple hours of sunlight during the day in many areas, unless you are too far south or north. There will be many occasions when freezing temperatures, clear skies and bright sunshine will be more ideal for solar oven use than a hot 100 degrees day with 95% humidity.
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Why Go Solar With Your Oven
Now that we have answered what is a solar oven, lets take a look at its advantages.
Popular culture makes a lot of fun of environmentally conscious people. While it may seem like youre the butt of a joke or two among friends, the benefits of a solar oven will make it all worthwhile. Solar ovens help us in four categories.
Disadvantages Of Most Sun Ovens
- Solar cookers or sun ovens usually take a long time to cook meals compared to fuel-based cooking systems.
- The cooking takes place at its best mainly during the hottest hour of the day. Now this can get heavily affected on cloudy days or partly cloudy days and during the winter months.
- Sun oven cooked food needs to be consumed soon after they are cooked. They do not retain the heat after sometime, so most people who would like to eat it hot and fresh do not have the choice in this case.
In the reflector type of sun ovens reflectors get highly affected with strong winds. When the reflectors angles change or its line of operation shifts from the point where the suns intensity is the most, the cooking efficiency reduces and it takes longer to cook the food.
For cooking the simplest food by a sun oven, it is important to grasp the techniques since it is not easy as it is for normal food.
Usually, simple food items which are devoid of oil and those that do not require deep frying can be cooked with the help of sun ovens. But thick food or fried food items cannot be prepared by a sun oven.
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Solar Oven Facts: How The Technology Works
The GoSun’s patented solar cooking technology can bake, boil or fry a meal using nothing but energy from the sun, even in clouds, wind and freezing conditions.
This article features solar oven facts that explain how the technology works and its comparable advantages and disadvantages to conventional cooking. We’ll also describe why we think the GoSun makes the best solar ovens.
Solar Oven Facts: The Solar Vacuum Tube
The core of GoSun Technology is with the vacuum tube cooking chamber, which absorbs light while acting as a perfect insulator. We think of it as a physics hack, one of thermodynamics only free lunches.
A perfect insulator? Thats right. Between the tubes two layers of borosilicate glass , is a pocket of beautiful nothing . Heat requires a medium to transfer. Without a thermal bridge, the heat absorbed by the stove collects rapidly.
How is the heat absorbed? Great question! The internal face of the tube is coated in three layers of metal: aluminum nitride, stainless steel, and copper. Placed on the inside of the vacuum , these three layers work in unison to trap both viable light and ultraviolet, allowing one to cook in a light overcast.
- Aluminum Nitride: An absorber common in the semiconductor industry with fantastic energy absorbing properties.
- Stainless Steel: Moves heat evenly, cooking food cooking from 360°.
- Copper: Reflecting heat, in the form of infrared radiation, back into the tube.
What is borosilicate glass?Borosilicate glass is known for its chemical and thermal resistance, making it a go-to choice for bakeware, LED lights, and lab equipment.
So this is high-tech, right? This technology is new but not cutting edge. GoSun founder and solar energy expert, Patrick Sherwin, got the idea while working with a solar vacuum tube water heater. The tubes used for solar hot water heaters have been known to last decades on roofs around the world.
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Is A Sun Oven Right For You
If you want to contribute even to a small extent in the energy crisis period and save some energy, then go for a sun oven which makes use of clean and renewable energy from sun.
A sun oven may be a little different to use in the initial days but with unreliable LPG supply especially in India, this may be a good option to try out with so many sunny days. More research work is invited in this field and there has been quite a number of improvements in the models that are now reaching the market.
Before buying a good sun oven you can also choose to make a simple solar cooker for your home. It is simple to construct a sun oven with simple readily available materials. In this way you can test the working efficiency of your sun oven and then you may have a better understanding while buying a sun oven for your home.
Sunny Science: Build A Pizza Box Solar Oven
An engineering enterprise from Science Buddies
- Shipping tape or black electrical tape
- A sheet of black paper
- A wooden skewer or pencil
- Warm, sunny day
- Graham crackers, marshmallows and a chocolate bar
Preparation
- If needed, clean out the pizza box so it is ready to become a solar oven. Remove any liners that the box came with.
- Adult assistance is recommended for using the utility knife. And use caution when cooking with the solar oven as it can get quite hot!
Procedure
Observations and resultsDid your solar oven get hot? Were you able to cook a tasty s’more using your oven? In this activity you built a simple box-type solar oven that should have been able to cook a s’more in sunny, warm conditions. In some trials using a solar oven that was made based on this design, at 85 to 90 degrees F on a sunny afternoon it took about 30 to 35 minutes for the marshmallow to get warm enough to become soft and melt some of the chocolate to make a tasty, solar-powered treat! In ideal conditions this solar oven can easily heat up to about 160 to 200 degrees F. Using full, direct sunlight is important for heating this solar oventhe sunlight needs to be reflected into the oven , and the heat must be trapped and retained inside by the plastic “window.” This heat is also absorbed by the black paper to heat the food that is placed on top of it.
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Wind Is Likely To Be A Factor
Expect the wind to be more of a factor during the winter. This is par for the course since solar ovens lose heat fast during high winds at any given time during the year. Oven designs can be chosen for maximum insulation. Also, the oven must be put in an adequately sheltered spot to ensure that there is not an unusual amount of heat loss.
If you follow these basic guidelines and make some adjustments, you should be able to use solar ovens during the winter, whether it be in your backyard or packed for a ski trip.
Having said this, there are some other considerations.
How To Use Solar Ovens
There are some simple tips you need to know before using solar ovens. Those tips will assist you in preparing your food faster without any stress.
Whenever you want to cook with a solar oven, you should use black pans or pots because black materials absorb heat best. Place your pan or pot at the center of the oven after adding all the necessary ingredients to the food and cover the oven with its glass lid.
Position the oven outside where sunshine reaches and leave it there. It might take up to 2 hours or more before your food gets done properly. Therefore, we advise you to be patient when using a solar oven.
You may have to reposition the solar oven if the shadow of nearby objects starts casting on it before your food is done. Its not advisable to remove the glass lid on top of the oven or stir the food you are cooking until the food is done.
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Solar Oven Facts: Compound Parabolic Reflectors
Compound parabolic reflectors concentrate light from a variety of angles onto the cooking tube. This means that there’s little need to re-adjust the stove while cooking and even diffused light can be focused on the tube.
Roland Winston invented the first compound parabolic concentrator in 1974, a breakthrough technology in solar energy. His discovery has now been used extensively in solar energy collection, wireless communication, and biomedical research.
Making A Lightweight Solar Oven
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