Posted on June 28, 2012 by shira
Last Saturday, Shawn Reeves of EnergyTeachers.org came over to our house to give a workshop on how to make a solar panel cooker using recycled materials. Read on for photos and info on how to make your own!
The class was offered through Ithaca Freeskool and we got the word out through Facebook, local email lists geared towards sustainability, and the Freeskool calendars, which are distributed to high-traffic spots around town. Besides Ari and Shawn and I, there were 14 people at the workshop.
There are many commercial solar ovens out there, but this cooker can be made using a cardboard box and aluminum foil, or even better, the reflective inside of chip and cookie bags. Since you only need three corners of a large box, you can make two cookers out of one box. To make sure your solar cooker gets hot enough, make sure it’s at least two feet wide / tall / deep. You can use gesso, an acrylic primer, as glue – paint it onto your cardboard and stick your shiny stuff down. Just watch out for your clothes – it dries quickly and doesn’t come out easily.
Once your box is all reflective, you need to get a pot into the center of it. A dark pot is best – enamel or ceramic could work, or you can use BBQ paint to darken a stainless steel pot. Be sure it has a lid to keep moisture inside, where it won’t cause sun-blocking condensation.
When cooking, you can sit your pot on top of a wire basket to raise it up a little – if it has some clear plastic on it that’s okay, but other colors of plastic will melt. You should also nest it inside another large jar (or two, or a terrarium) or put it inside a roasting bag, to keep its heat from escaping. Roasting bags are the only plastic bags you can safely expose to heat without leaching plastic into your food; you’ll want the “turkey” size since it’s largest. If you really get into solar cooking, you can buy a large box of roasting bags from a kitchen supply place – they’re also used as institutional warming tray liners.
For extra maneuverability, you can put your cooker on a music stand – you may need to rotate it to keep it aimed at the sun throughout the day.
Here we are gathered in the kitchen, using Shawn’s nifty infrared reader to see how glass works as an insulator to help food cook efficiently in a solar cooker:
Visible light goes through glass and plastic, but infrared light (heat) can’t get out; glass is more effective than plastic. We also tested the aluminum, which reflects so well you can see a mirror image of your hand in its surface. Shawn told us that when a solar panel cooker is set up right, you can see six reflections of the sun being projected onto the pot, along with the direct rays of the sun. Yay science!
Shawn also told us about a cool device called a WAPI that makes it easy to tell if whatever you put in your pot has been heated above the temperature required for pasteurization. If you leave the cooker during the day, you’ll have a little record to tell you if your food got hot enough to be safe to eat.
Think of your solar panel cooker like an EZ-bake oven or like a very slow cooker. Cookies are faster and easier to cook than is soup – the more water you’re heating, the more sun you need. If you’re baking bread, try low-gluten recipes, and watch out for sourdough; it can get too sour due to the long slow heating process. Frozen vegetables heat up very easily since they were partially cooked as they were processed.
Here’s Shawn helping to test a cooker built by one of the workshop participants, who was able to raise the temperature of the water in a can 20 degrees in less than a half hour using the sun.
A bunch of solar cookers were constructed at the workshop – thanks to everyone for coming! You can make your own by following the plans online. There are lots more variations on the Solar Cookers World Network wiki. Thanks again to Shawn Reeves for teaching us how to do this. Click here to learn more about solar cooking at EnergyTeachers.org.
We plan to use our own cooker soon and are psyched to further reduce our dependence on fossil fuels!
- The Power of the Sun
- Ithaca Freeskool: We Are All Teachers – New Video!
- Logo for Sol Kitchen, a Cool New Solar Cooking Education Project
- Report from the Community Sneak Peek of “Empowered”
- Video: Highlights from Ithaca Freeskool’s Summer 2010