How to Build a Solar Cooker From a Broken Umbrella

Solar cooking is an eco-friendly way to prepare your meals without relying on electricity or gas. In this instructable, I'll guide you through the process of making a homemade solar cooker using a broken umbrella, aluminum foil, tape, scissors, and some basic crafting skills. Let's harness the power of the sun to cook delicious meals sustainably!

1. Broken umbrella
2. Aluminum foil
3. Tape
4. Scissors

More and more people are embracing the idea of cooking with the sun's rays. Solar cookers offer the ability to prepare various types of food, albeit requiring a bit more time. For history buffs, it's worth noting that the solar cooker was invented by a Swiss naturalist named Horace de Saussure in 1767.

How Does a Solar Cooker Work?

A solar cooker harnesses the UV rays of the sun. It allows UV rays to penetrate and then converts them into infrared rays that cannot escape. These infrared rays possess the energy to vigorously vibrate the molecules of water, fat, and proteins in the food, heating them up.

It's not the sun's heat or the external ambient temperature that cooks the food, though these factors may affect the cooking pace or time. Rather, it's the solar rays that transform into heat energy, cooking the food. This heat energy is retained by the pot and the food through a cover or lid.

Think of it like how a greenhouse traps heat or a car with windows rolled up. An effective solar cooker will utilize solar energy to heat a cooking vessel and efficiently retain that energy (heat) to achieve maximum cooking efficiency.

To achieve maximum efficiency, it's necessary to "follow" the sun, adjusting your solar cooker so that it directly faces the sun to better concentrate and absorb the solar rays. This doesn't mean you have to constantly be next to the solar cooker during the entire cooking period. However, occasional adjustments in angle and direction may be needed, perhaps every hour or so.

The more direct the sun's rays are towards the food and the pot, the greater the energy (heat) capacity of the converted solar rays.

Ideal cooking results with a solar cooker occur when the sun is bright and unobstructed by clouds, shadows, etc. While cooking is still possible on days with high and sparse clouds, it may slow down the process slightly, so it's advisable to start a bit earlier than usual.

Slow and moderate solar cooking, such as stews, chili, vegetables, etc., will work well under less bright skies if given more time. However, cooking may take longer, and temperatures may not be as optimal as they could be, resulting in uneven baked goods.

How Do the Different Parts of a Solar Cooker Work?

In most solar cookers, there are three main components, or one could say, three primary principles for effective solar cooking: Concentration (reflection or reflectance), Absorption (capacity to attract or retain heat), and Retention (mediums or capacity to retain heat).

Concentration of solar rays is achieved in most cases through reflective panels, petals, and similar surfaces that can "focus" or concentrate UV rays onto a point or concentration. These reflective panels are usually made of materials that are bright and reflective due to the substance used in their manufacture, such as silver, chrome, and aluminum. Without a means to concentrate solar rays, it may take longer to heat objects or surfaces, so most solar cookers are built with reflective panels to accelerate the heat accumulation process.

Absorption of solar energy (heat) in the solar cooker is best achieved when a surface is dark in color. Hence, the interiors of most common solar ovens are usually black, as are the utensils used to cook the food. Dark colors absorb heat, while light colors don't absorb heat well. And some colors can reflect solar energy, like silver, for example. In general, the best cooking utensils for solar cooking are dark and thin because they absorb heat (energy) well and, being thin, can transfer heat more quickly and evenly to the food.

If a solar cooker is not well insulated and doesn't have a lid, then all the concentrated heat (energy) and absorbed heat will dissipate quickly into the air and be lost to the environment. A solar cooker must have the means to "trap" or retain the concentrated heat, allowing it to accumulate and "build up" to sufficiently high levels to effectively cook.

A fourth principle, though not vital in all forms of solar cooking (the parabolic solar cooker is one of them), is the transparency of its retentive materials, or in other words, its lid in a solar oven or its enclosure around its cooking pot/pan in a panel solar cooker must be able to allow solar rays to penetrate into the interior to where the food/cooking vessels are. This capability of solar ray penetration is typically achieved by using transparent glass or plastic covers on the lid/door/enclosure of the solar cooker, which in turn acts as an inhibitor, also trapping heat.

Through these principles, a solar cooker efficiently captures and utilizes the sun's energy to cook food, offering an eco-friendly and sustainable alternative to traditional cooking methods.

Carefully cover the entire surface of the umbrella frame with aluminum foil. Make sure to smooth out any wrinkles to ensure maximum reflection of sunlight. Use tape to secure the foil in place if needed.

Shape the aluminum foil-covered umbrella frame into a parabolic surface. This will help in concentrating sunlight onto the cooking vessel placed at the focal point. You can do this by gently bending and shaping the foil-covered frame until it resembles a parabolic dish.

Once you've shaped the foil-covered frame into a parabolic surface, create a stable platform at the focal point where you'll place your cooking vessel. Use additional layers of aluminum foil to fashion a tray or platform for your pot or pan to sit on securely.

Once your solar cooker is assembled, place it outdoors in an area with direct sunlight. Adjust the angle of the cooker throughout the day to ensure it's facing the sun directly for maximum efficiency. This may require occasional monitoring and adjustments.

Now that your solar cooker is ready, you can start cooking! Place your pot or pan containing your food onto the prepared platform at the focal point of the cooker. Keep an eye on the cooking progress and adjust the cooker's position as needed to maintain optimal sunlight exposure.

In this instructable, we've embarked on a journey to repurpose a broken umbrella into a functional solar cooker, demonstrating the power of creativity and sustainability. By leveraging simple materials like aluminum foil, tape, and scissors, we've constructed a homemade solar cooker that harnesses the sun's energy to prepare meals without electricity or traditional fuels.

Through understanding the principles of solar cooking—concentration, absorption, and retention—we've transformed our broken umbrella into a powerful culinary tool. By focusing sunlight onto a cooking vessel covered with dark materials, we've effectively heated our meals using the sun's natural energy.

While our DIY solar cooker may face challenges such as dependence on sunlight and longer cooking times, its eco-friendly nature and ability to produce delicious meals make it a worthwhile endeavor. By embracing solar cooking, we contribute to environmental sustainability and reduce our carbon footprint.

In conclusion, this instructable highlights the ingenuity of repurposing everyday items for sustainable living. By converting a broken umbrella into a solar cooker, we've not only reduced waste but also empowered ourselves to cook delicious meals using renewable energy. Let's continue to explore creative solutions for a greener future, one project at a time.