Free Fuel! Cooking With The Sun.

A few years ago I invested in a solar oven.  Ever since then, once Spring arrives, whenever we have a sunny day I look out the window and think "I am wasting all that beautiful" sunlight--I could be cooking delicious food for FREE!  And the benefits of cooking with the sun are not just the fuel savings...the food tastes better (slow cooked in its own juices so nothing is lost) and it's tender.  With solar cooking it's almost impossible to burn food.  Instead, it is mouthwateringly juicy, delicious, and you cook it for free.  You can buy solar cookers with many interesting features or you can make your own simple solar cooker for under $10.

Many people in the developed world choose solar cooking because it is the simplest, safest, most convenient way to cook food without consuming fuels or heating up the kitchen. That means it can be used when you're away from fuel sources (e.g. camping) or in emergency situations, but it also means that you can save money as well as conserve flavor and nutrition.  For the undeveloped world solar cooking actually saves lives.  For hundreds of millions of people around the world who cook over fires fueled by wood or dung, and who walk for miles to collect wood or spend much of their meager incomes on fuel, solar cooking is more than a choice — it is a blessing. For millions of people who lack access to safe drinking water and become sick or die each year from preventable waterborne illnesses, solar water pasteurization is a life-saving skill. The World Health Organization reports that in 23 countries 10% of deaths are due to just two environmental risk factors: unsafe water, including poor sanitation and hygiene; and indoor air pollution due to solid fuel use for cooking.  Here's a great National Geographic video on the value of solar cookers in the developing world.  

Types of Solar Cookers:

• Box cooker - This is the most common type.  It consists of some sort of box painted a dark color on the inside and sealed with a glass window to let the sun in and keep the heat from getting out.  There is usually a reflector to multiply the amount of sunlight shining into the window.  Box cookers have the advantages of being simple / inexpensive and of being able to hold multiple pots of food at a time.  They do tend to cook food more slowly but they are simple and safe.
• Parabolic cooker - This type is curved like a small satellite dish but it has a reflective surface so it concentrates the solar energy on a spot out in front of the parabola where a shelf is mounted to hold a dark cooking pot.  This cooks the fastest and at the highest temperature but it requires frequent adjustments and supervision to be operated safely. 
• Panel cooker - This is a combination of the box and parabolic cookers.  Angled panels concentrate the sunlight to the middle where a dark pot is placed inside a sealed clear container of some sort (the simplest is a clear plastic oven safe bag such as those for roasting turkeys).  These cookers generate more heat than the box cooker but are safer and easier to use than the parabolic cooker.  They do tend to have more limited cooking space so fewer pots can be used.

The basic principles of solar cooking:

• Use the sun's energy for fuel - You need to place your solar cooker in an outdoor spot that will remain sunny for several hours.
• Converting light to heat energy - Dark surfaces absorb heat and light ones reflect it.  Food cooks best in dark, shallow, thin metal pots with dark, tight-fitting lids to hold in heat and moisture.
• Trap the heat - Take advantage of the green-house effect (i.e. light enters a sealed transparent chamber but the heat is retained).  This can be accomplished by using a clear, heat-resistant plastic bag or large inverted glass bowl (in panel cookers) or an insulated box with a glass or plastic window (in box cookers).
• Multiplying the sunlight energy - One or more reflective surfaces can be used to concentrate additional solar energy onto the cooking area.

Make or buy?

You can make your own low-cost solar ovens or you can buy pre-made solar ovens.  The purchased ones tend to be more durable (e.g. waterproof, wind-resistant etc.), but there are some truly simple and innovative home-made options (e.g. there is one that is made simply and quickly from one of those reflective car windshield shades).

I chose to buy a unique solar oven that is an hybrid (solar / electric).  It was invented in India, is called the Tulsi Hybrid Solar Oven, and can be purchased for under $300 (see the pictures below).  It is a box cooker (although it has two additional reflective side panels that give if almost panel-cooker efficiency) and, for portability, it is designed like an old-style clamshell suitcase.  When it's opened the inside of the lid contains a reflective surface and the lid can be locked in place at any angle to maximize the reflection of the sun into the chamber below.  The inside of the bottom chamber is lined with dark plastic and the chamber is sealed shut by a hinged window to let the sunlight in but keep the heat from coming out.  What is quite innovative about this cooker is that it can be plugged into a 110 V power source to engage low-amperage infrared heating elements to boost the heat from solar cooking on cloudier days.  You can even cook with only the heating elements in the early morning if necessary.  The electrical heating elements have a regular setting (200 Watts) and a high setting (400 Watts) and with them the unit can actually reach oven-like temperatures of up to 400 degrees fahrenheit.  The electrical draw is low enough that I could use it with the inexpensive solar power system I set up at home for a backup.  What all this means is that you can still cook food when there is little or no sun (e.g. make your breakfast in the morning, cook on cloudy days, or make dinner in the winter).  Of course you can cook strictly solar when there's plenty of sun.  The unit also comes with an oven-thermometer and 4 stainless steel pots with lids.  The tops and bottoms are painted black to maximize heat absorption.  

Cooking in a solar oven:

If you have a box-type cooker start by setting up the solar oven to preheat (not necessary with parabolic or panel cookers), aiming it toward the sun and then turning it slightly ahead toward where the sun will be in the next hour or so.  Then go start preparing your food.  You can cook almost anything in a solar oven.  The cooking times are longer than in a conventional oven and will depend upon the type of food you are cooking (see this site for guidelines to cooking times).

For the meal illustrated above I decided to make breaded chicken breast (dredged the chicken in kefir and then rolled it in breadcrumbs--ground up homemade bread in my Blendtec--with salt, pepper, and garlic powder to taste) with roasted cauliflower, mushrooms, and sweet potatoes.  I could have done it all in one pot but the Tulsi that I own gives me plenty of room to spread out so I cooked the food in three different pots.  I spray the pots with cooking spray and then put the food in.  Don't use any water. The food cooks in its own juices--that's what makes it so flavorful and succulent.  If you are preheating a box cooker once it has reached at least 300 degrees fahrenheit you can put the food inside.  Close the glass lid tightly or seal the oven cooking bag you're using in order to retain the heat.  The temperature in my solar oven drops initially, both because I opened the glass to put the food in and because the food is cooler than the chamber, but it climbs steadily.  I can tell when the food I'm cooking is done because condensation forms on the inside of the window (see the middle left photo above).

Advantages of solar cooking:

According to the non-profit Solar Cookers International which promotes solar cooking around the world the advantages of solar cooking include:

• Moderate cooking temperatures in simple solar cookers help preserve nutrients.
• Those who otherwise could not afford the fuel to do so can cook nutritious foods — such as legumes and many whole grains — that require hours of cooking.
• At times many families must trade scarce food for cooking fuels. Solar cooking can help them to keep more food and improve their nutrition.
• Smoky cooking fires irritate lungs and eyes and can cause diseases. Solar cookers are smoke-free.
• Smoke from cooking fires is a major cause of global warming and dimming.  No environmental impacts.
• Cooking fires are dangerous, especially for children, and can readily get out of control — causing damage to buildings, gardens, etc. Solar cookers are safe and fire-free.
• Millions of people routinely walk for miles to collect fuelwood for cooking. Burdensome fuel-gathering trips can cause injuries, and expose people to danger from animals and criminals. Solar cooking reduces these risks and burdens, and frees time for other activities. In the Iridimi Refugee Camp in Chad the necessity of leaving the camp to gather firewood was reduced by 86% through the introduction of tens of thousands of solar cookers.
• With good sunlight, solar cookers can be used to cook food or pasteurize water during emergencies when other fuels and power sources may not be available.

Try cooking with the sun.  It save you money, it's environmentally sound, and the food is more nutritious and tastes great.  Here is a list of recipes or you can adapt your own.