Tuesday, April 19, 2011

What Is A Solar Oven and Where Can I Get One?

A solar oven, or solar cooker, is a way of cooking food that does not require wood for burning, or natural gas or electricity. A solar oven uses the power of the sun to heat and cook the food. They are very simple to make, and there are multiple designs available. The design for the solar oven I ended up with was a bit of a mix of two designs I found online, due to materials I had on hand or could easily obtain with minimal out of pocket expense. Also, I have included some tips to make the building of your solar cooker easier, based on my experience. In my next blog, I will include a picture of the oven, and hopefully a video of my first test of the completed oven!

Here is the website where I got the inspiration for my idea: http://www.solarcooking.org/plans/

Part of my ‘green genie’ project is to keep each project low cost, so I completed this project with materials that were on hand or free. I didn’t succeed entirely, but I believe the whole project cost me about $6-10 all told.

Here’s what you’ll need to build your solar oven:

1. Three boxes, one with a lid. I like copy paper boxes for size and sturdiness. I used that as the outside box. The inside box should be smaller and fit within the larger box, leaving a gap of at least ½” room to spare on each side (more is okay). The inside box does not need a lid. I used a business envelope box. My third box had to be as long as the copy paper box because that is what I will use to create a sunlight reflector. My cost: FREE

2. Newspaper (or any balled up paper). My cost: FREE

3. A piece of glass or an oven cooking bag. My cost: $2.99

4. A glass cutter (they are $3.79 at Home Depot) My cost: FREE

5. Scissors or utility knife. My cost: FREE

6. A straight edge or ruler. My cost: FREE

7. Aluminum foil. My cost: FREE

8. Flat black paint (tempera, non-toxic spray paint, permanent marker or a mix of soot and flour paste.) My cost: $1.99

9. Stapler with staples. My cost: FREE

10. Black duct tape. I like Gorilla Tape, but it is pricey. (I had this on hand from another project). My cost: FREE

11. Heat resistant glue. My cost: $.99

12. Goggles and gloves for glass cutting & handling. My cost: FREE

I painted the bottom, outside and inside of each box with black paint. I rolled out, measured and cut sheets of aluminum foil for the inside of each box, but left the bottom and outside of each box black. Once the paint was dry, I stapled the sheets of aluminum foil along the sides with the stapler. I set them aside.

For the copy paper box lid, I painted it black, too. Then, I measured a rectangle in the middle of the box, leaving a one inch lip from the edge. The box lid should look a lot like a picture frame.

I am not big on plastic oven bags but they are an alternative if you have no glass and you don’t mind replacing the bag when it deteriorates from heat. I prefer glass and bought a piece cheaply. I went to Goodwill and found an old picture frame for $2.99. I made sure it was made with glass because that’s really the bit I wanted. (I got a quote for having a piece of glass custom cut, and going to Goodwill is by far the cheaper option). If you’re really lucky, you’ll get a piece that matches your box lid dimensions. I wasn’t so lucky and had to cut mine. I used a glass cutter. (This is probably the most labor-intensive and risky part of the project. The first time I tried, I broke the piece of glass and had to use another. Fortunately, I had a spare for that reason.)

You’ll need a stable surface, a glass cutter, gloves, goggles and a sharpie marker. I took my ruler, measured the box length and width, and took my sharpie marker and marked up my piece of glass according to my measurements. I used the glass cutter to score the glass. Gently, I broke off the piece of scored glass. Please be sure to use glove and goggles, because those glass fragments can really hurt!

Slide the piece of glass you’ve cut inside the box lid and ensure a good fit. If your glass fits, you can glue it on the inside of the box lid and set it aside to dry. You can edge it inside and out with the black duct tape if you would like some additional support.

Alternately, you can open your oven bag (splitting it down two sides), lay it flat and tape it into place in the lid. Be aware that although this method is simpler up front, you will need to continually replace the bag each time it wears out due to heat. I have found it has much less durability than the glass method, with longer costs over time (those turkey-sized oven bags aren’t cheap!) Also, it is my experience that the glass retains heat better.

Now, onto the sunlight reflector!

Open up the third box and lay it flat. Cut a rectangle that is the same length and height as your bigger box. If you have a piece that is bent into three panels, like a triptych, that is even better. (I had a piece like that and it really helps with the reflection of sunlight.) Using flat black paint, blacken the cardboard. When it is dry, cover the front side with aluminum foil and staple it into place.

Assuming the rest of your black paint and glue has dried, you can begin assembling the components.

Take your balled up newspaper and place some in the bottom of your bigger box. Put the smaller box inside and add more newspaper around the sides for insulation. This stabilizes the inner box and allows for heat to flow under your inner box, as well as around the sides, for more even, rapid cooking. Place your completed lid over the top, and you’re nearly there! You can, if you like, staple or tape your reflector on, but I find you can just rest the lip at the bottom on the back of the box and fold the side flaps forward a bit it works fine without having to add and remove it each time.

I believe this project took me about 75 minutes, start to finish. (The paint dries quickly on cardboard) It is kid friendly, except the glass cutting. That is something only an adult should do.  I would say this project is a good family project, for children 11+ with strong adult supervision.

We are going to give our solar oven a trial run on the weekend, and next week I will post pictures and video of how our oven worked and what we cooked in it, and how long it took to cook the food.   Stay tuned!


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Anonymous said...

very good my friend!!!<3

Tom Watson said...

I have included some tips to make the building of your solar cooker easier, based on my experience. In my next blog, I will include a picture of the oven, and hopefully a video of my first test of the completed oven. View website here

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