DIY Solar Options to Cook and Purify Water

How to Harness Solar Energy
Solar power is flavor of the month right now, but there is real value in your learning how to use the sun’s free energy to your advantage in an emergency.
With a regulatory and legal mess that has prevented the modernization of America’s antique and increasingly prone-to-failure power grid, you are increasingly exposed to the potential for electricity outages. One critical step to being prepared for an emergency is making sure you have enough fuel on hand to cook your food, keep yourself warm, and get around.
We’ll share a low-cost way you can cook your food and purify your water without using any fuel at all.
Now, there will be days you can’t use this cooking method, but on the days you can, it’s a fuel-free, no-fuss way to cook a delicious meal or boil water. It’s easy and affordable – you probably have most of the items on hand already – and it can be a real asset in a crisis. I’m talking about building your very own solar oven.

Passive Energy from the Sun
Can Be Harnessed for Free – If You Know How

Passive solar power concentrates sunlight to generate heat. Passive solar power is most commonly used to heat homes. The huge advantage of a passive solar system is that it doesn’t involve any mechanical or electrical parts. Because of that, taking advantage of passive solar power is one of the most efficient ways to use the sun’s abundant energy.
A passive solar oven system is a handy tool to have in your preparedness kit. When it’s sunny out, you can use your passive solar oven for fuel-free cooking. You can even use it to boil and purify water… it really does get that hot!

A Simple Box Oven
Can Serve You Remarkably Well

The easiest model of solar oven to build is a simple box oven. You’ll need some pieces of plywood, a piece of window glass, cardboard scraps, a hammer and nails, aluminum foil, glue, black paint, and duct tape.
Begin by framing your box. You can make your box any size you wish, but keep in mind that a larger box will not get as hot as fast and will be less efficient at retaining heat. On the other hand, the box must be big enough to accommodate a cooking pot.
Simple Solar Box Oven
A box 12 inches high and 18 inches square will probably prove sufficient. Depending on the height of the pot you intend to use in the box, you may want to add two or three inches to the height. You may also choose to base the length and width of your box on the dimensions of the glass you are using. It will be the top of the box, and unless you have access to a glasscutter, this may be the easiest route to go. Any glass shop and many home
centers and hardware stores will also cut glass to
your exact specifications.
Use your hammer and nails to assemble the box (four sides and a bottom), leaving it open on top. Use duct tape along each inside seam to create a tighter seal. Next, line the inside of the box with layers of cardboard. You want an inch worth of cardboard on each side and on the bottom. Make sure you cut your cardboard lining so it is flush with the top of the box.
Paint the outside of your box black. Make sure you choose a non-toxic paint. It’s unlikely that your food will come in contact with the paint as you cook, but better safe than sorry.
Your glass piece will sit on top of your box. That’s why it’s important the cardboard is flush with the top. Not only does it serve as an insulator, it also helps create a seal between the glass and the box. For safer storage and use, you may wish to use a piece of Plexiglas®.
Next, make a reflector using a piece of cardboard that’s the same width (less two inches) as the box. Wrap the cardboard in aluminum foil, using glue to affix the foil to the cardboard. Then, vertically nail two small pieces of scrap wood (about one inch by six inches) to the back of the box at each top corner. They should jut three or four inches above the top.
Nail two more pieces of similarly sized wood to the bottom corners of the cardboard. Finally, nail the pieces of wood attached to the cardboard to the pieces of wood attached to the box. Do this at an angle, so that your cardboard reflector leans over the top of your solar oven by about 20 degrees. (Or you can completely skip this system of affixing the lid to the box by using some other device to hold the reflector in place above the solar oven; for example, a coat stand, lamp stand, plant stand or similar device onto which you can clamp your reflector at the appropriate angle.)
Your solar oven will basically work as a slow cooker. Put your food into a pot and then put the pot inside an oven-roasting bag. The bag will help heat the food faster and keep it hotter throughout the day. Put the pot and bag into your solar oven. Place the glass lid onto the top of your oven, and face the solar reflector to the south (to the north if you’re in the Southern Hemisphere).
The food will take about twice as long as your crockpot recipe calls for to cook. You may need to start cooking by mid-morning, but as long as the day averages at least 20 minutes of sun per hour, your meal should be hot and ready to eat by dinnertime.
Solar Funnel Ovens:
Another Great Emergency Option
Simple Solar Funnel Oven
Another option is to build a solar funnel oven. To do this, you’ll need a two-foot by four-foot piece of cardboard. Cut a half circle out of the bottom of the cardboard. The diameter of the circle should be the same as the diameter of the cooking pot you intend to use with the oven. Next cover the cardboard with aluminum foil. Use glue to fix it in place.
Gently bend the two edges on either side of your half circle together to form a large funnel with a hole at the bottom. (The foil should be on the inside of the funnel.) Secure the funnel with metal brads, or use a hole punch and string to tie the edges together.
Place a block of wood in the bottom of a cardboard or wood box. Fill a black cooking pot with food, put it in an oven bag and set it on the block of wood. Put the foil-covered funnel down around your pot, so the hole at the bottom the funnel slips around it. The edges of the box will hold the funnel in place. Leave your solar funnel out in the sun to cook whatever is in your pot.
The cooking times for the solar funnel model are usually less than those for a box oven. Experiment with your own slow-cooker recipes to find what cooking times work best for your fuel-free oven.

Purify Water with Your Solar Oven
Key to Survival in a Pinch

Purify Water with Your Solar Oven
If you need to sanitize water, you can use your solar oven to bring it to a boil. In this case, put the water in a canning jar that you’ve painted black. Leave a strip unpainted, so you can see when the water boils. Once the water reaches boiling, allow it to boil for a full minute to sanitize it.
You can also boil water in a pot, if the pot has a clear lid. When you’re purifying water, you need to be able to confirm it’s reached a boil. The clear lid will make the process less efficient, but will allow you to see when the water boils.

Build Your Own
Ready-for-Anything Oven Today

Here are three more tips to help you get the most out of your solar oven:
  • Solar ovens reach temperatures of up to 275 degrees, and they will heat up your cooking vessel, so make sure you use potholders to retrieve what you’ve cooked.
  • For the best results, clean your reflective surface periodically so that they reflect the most sunlight possible.
  • Check that foods are thoroughly cooked before eating. This isn’t usually a problem, but it’s always best to be safe.
In an emergency, being able to cook a meal or purify water without using fuel is extremely useful. And, you can literally build a solar oven using things you can find in your own pantry and garage or at the local scrap yard.
Don’t wait until you’re in the stress of a full-blown emergency or power outage to get this simple task done. The time assemble your solar oven is now, when you have access to supplies and time to plan. This is definitely one tool you want to have on hand.