Solar Ovens: What Are They? How Do They Work?

Solar is a clean, renewable energy source, which decreases deforestation, fossil fuel usage, and greenhouse gas emissions. Solar ovens are devices that collect energy from sunlight to focus the heat and cook food without other fuel sources. Solar ovens enable affordable off-the-grid cooking. They are also a sustainable option for cooking in isolated communities and rural areas.

Solar ovens can be moved easily and set up anywhere sunny, and DIY versions can be made at a very low cost.

How Solar Ovens Work

Solar ovens direct sunlight into a cooking space, where the trapped heat gathers. The exact process varies by design, but all solar ovens require highly reflective materials (such as mirrors, polished metal, or aluminum foil) set at particular angles to gather light.

Solar ovens must retain heat well for stable cooking. This is often accomplished by separating outside air from the air inside the oven or the cooking vessel. This can occur by a process similar to the greenhouse effect, trapping heat under the clear lid of the oven. However, other ovens simply target heat at a sealed cooking vessel, minimizing wasted hot air.

There are dual electric/solar ovens available, which use an electric hot plate at the base for overcast days or faster cooking. However, most solar ovens won't function at night or when it's overcast.

How to Cook With a Solar Oven

Solar ovens can operate anywhere the sun is shining, which makes them great for portable cooking. However, they do require adjustments to cooking with a fire or traditional oven.

To make the most of your solar oven, make sure that you:

• Reposition the oven every thirty minutes to target the sun and collect the most rays.
• Use pressure-sealed cookware or vent your vessels to prevent overheating and explosions.
• Cooking times vary widely based on sun exposure, so use a thermometer and your eye to determine when your food is cooked.
• Start by cooking vegetarian foods until you become more confident using your solar oven.
  

Benefits of Solar Ovens

There are many different reasons people choose solar ovens, including their safety, sustainability, and reliability.

Economic Benefits

High-end solar ovens are very efficient but aren't cheap. However, DIY options can be made with everyday items, like aluminum foil, plastic wrap, and pizza boxes.

After the initial purchase cost, even expensive solar ovens remove the cost of cooking fuel, meaning there are long-term cost reductions.

Safety Benefits

Solar ovens work without electricity, making them a great survival option. They are handy elements of hurricane preparedness kits and in situations when areas could be without power for an extended period of time.

Because they don't require a fire, they're considered safer than burning wood or other materials.

Environmental Benefits

Solar energy is a renewable resource. It is less environmentally harmful to cook food with this energy source when compared to non-renewable sources like wood and fossil fuels.

Using sunlight to produce heat means less air pollution and deforestation, as wood isn't burned and petrochemicals aren't being processed for fuel.

Choosing a Solar Oven

Selecting the right solar oven first requires determining what you'd primarily like to cook. The most basic DIY varieties are great for S'mores, but they won't sear a steak.

For all types of ovens, it's ideal to have a thermometer, if one isn't integrated into the oven's design. It's also important to consider if you plan to travel with your solar oven. Some ovens are much lighter and easily broken down for transport than others.

Here are some pros and cons for different types of solar ovens.

Box Ovens

Box ovens are made of reflective boxes with a clear lid surface. They typically contain the most space for cooking and can often allow multiple pots of food to be prepared at once. However, they are usually not very portable, since they cannot collapse.

These solar ovens are great for baking, cooking beans, or foods that require a longer, cooking time. When cooking with box ovens, make sure that you:

• Keep the lid clean to allow the maximum amount of light to enter the container.
• Try to avoid opening the lid during cooking as that will release heat. The exception is if steam obscures the top of the box it could reduce how much sunlight can enter, and it will need to be released.
• Use dark, shallow, pans, as that will help absorb optimal sunlight.
• You can place a dark brick or stone inside and place the box in the sun to preheat.

Panel Ovens

Panel ovens are made up of reflective panels that focus energy toward a cooking source. They are ideal for people on the go, typically lightweight and easy to transport. That said, they don't reach the temperatures that box and parabolic ovens can, so are less effective for longer cook times.

When using these ovens, work with a dark pan or glass jars that have been painted black. To further concentrate heat, you can put the cooking vessels in a sealed oven bag.

Parabolic Ovens

Parabolic ovens are the most efficient solar ovens, as they are mathematically designed to concentrate solar energy to a single point. 

Parabolic ovens are difficult to transport and can only cook one vessel at a time. But they are the most powerful solar ovens available, reaching temperatures of up to 400 F.  They can cook food faster than other ovens and even bake breads.

When cooking with a parabolic oven, you must regularly reposition the parabola as the sun changes positions. This makes it less ideal for passive cooking.