This is the third in a series of guest blog posts by Alissa Emmel about renewable energy projects in Nicaragua.

Cookies baking in a solar oven

You can imagine that I was pretty excited to learn how to make a solar oven. What’s a solar oven? There are many ways to make a solar oven (also sometimes called a solar cooker), but at its most basic it is a box with a glass top and a reflective lid that takes advantage of the greenhouse effect.  Sunlight enters the solar box through the glass or plastic top. It turns to heat energy when it is absorbed by the dark absorber plate and cooking pots. For those of you who don’t remember your physics classes, when light waves are converted to heat waves they become longer.  They basically become trapped in the box and just bounce around. This is the same effect that you have in a room with a lot of windows on a sunny day.

Cookies fresh from the solar oven

We got to participate in the actual construction of solar ovens (sawing wood, hammering nails, cutting aluminum paper for the reflective lid, etc.) and then we got to put the ovens to use. The oven can get up to about 300 degrees Fahrenheit, and it works great for anything that you would make in an oven or a slow cooker.

Pros:

• There is no energy cost
• The energy is completely renewable
• The food is delicious
• There is a decrease in the need to firewood, which helps combat deforestation
• There are no respiratory diseases associated with this type of cooking
• The materials are readily available and the construction is simple
• The ovens provide more free time for women who are doing the cooking

Cons:

• They don’t work well for making items that need quick bursts of heat, like tortillas
• They can’t be used for breakfast (since there is no sunlight that early)
• Most of the food is ready between 11:00am – 4:00pm, since as the sun sets the cookers lose heat
• During cloudy days or rainy seasons the ovens may not heat up

Chicken and rice cooking in a solar oven

So, as you can see, solar ovens are not a complete solution, as most people would still need or want a supplementary cooking source for early in the morning or on cloudy days. However, if firewood was only used for those times and the solar ovens were used for the rest, the use of firewood would be greatly decreased. (The Solar Women of Totogalpa are also engaged in creating more efficient stoves that can burn briquettes made of agricultural waste such as corn husks.)

I think most of the pros and cons are fairly self-explanatory except for my last item on the pros list. In general cooking items in a solar oven takes longer than over an open fire (about two times as long).  However, when you cook something over an open fire you have to stand at the fire, breathing in the toxic fumes, to make sure that the item doesn’t burn and that nothing catches fire. In contrast, with a solar oven, you put the oven outside and let it heat up, stick the food in the oven and then walk away. When you come back the food is ready.  This then frees up time to do other activities like washing clothes, gardening, caring for children, studying, etc.

Below are pictures of members of my group constructing an oven.

Other posts in this series:

1. Renewable Energy Projects in Nicaragua
2. The problem: cooking with firewood
3. The solution: solar ovens
4. Re-seeding the Forest
5. Is renewable energy practical?
6. The Solar Women of Totogalpa
7. Making a biosand water filter