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Most people associate the name Archimedes with a screw that pumps low-lying ditch water into nearby fields for irrigation, though some historians no longer credit him for this invention (it may have been Assyrian or Egyptian and from three centuries earlier). Still, his name lives on — and not just for his engineering legacy.
It seems that as soon as the Romans showed up near his Sicilian city-state of Syracuse, he switched from scientific inventor to Roman-killing machine designer. There was the Archimedes' Stonethrowers, Archimedes' Claw (which ripped full-sized boats from the water), and — relevant to our interests here — Archimedes' Death Ray. Yep, a contraption that harnessed the sun to burn invading ships.
Though debunked a couple of times by Mythbusters, and then proved a few other times by scientists and historians from MIT and other egghead factories, it's debatable whether the Death Ray actually existed. But the science is sound. Bounce light from the sun via a series of mirrors at something, and the electromagnetic radiation from the sun is redirected to that object, along with its heat. According to lore, Archimedes did just that in 214 BC when the Romans rowed into town, and his aptly named Death Ray was never heard of again.
But that's exactly what makes solar ovens so efficient. They use no electricity, gas, or external power. They make no noise and cost nothing to use. Just point one at the sun, fill it with your favorite food, “set it, and forget it.”
Regardless of the environmental benefits, the economic perks, and the ease of use, is a solar oven practical for your application, lifestyle, or situation? Would you use it as a daily oven or a kitschy novelty to bake cookies while the kids play in the backyard? Or is it your omega oven, your last line of defense against starvation when faced with a wasteland where there's no more wood to burn, no propane tanks to tap, nor fuel of any kind but the blazing sun?
A solar oven is a versatile tool if used properly, but not necessarily something you'd keep in your bug-out vehicle or store in your cache of gear. Some are flimsy, some fragile, some intricate, and some are just plain bulky. But they have a purpose, however limited in application, within the scope of survival, prepping, and thriving under adverse conditions. Their initial cost is comparable to gas camp ovens, and if you'd like to save even more dough (to buy dough for your oven), have your local Cub Scout make you one out of a pizza box and some tin foil.
Getting the obvious out of the way first, weather plays a huge part in whether you'll eat that day. If there's rain, snow, high winds, fog, or even those puffy white clouds that look like circus animals, you won't be eating warm food that day. At higher latitudes during the winter, the sun sits lower in the sky and isn't as effective — that's why we experience winter to begin with. Some places, the sun disappears for months at a time.
Other drawbacks of solar ovens are few, but important. They're not especially convenient. You'll need to plan ahead and start cooking early if you want a decent meal. Some need constant realignment as the sun arcs across the sky, while others don't hold heat very well or contain much food at all.
There's a higher risk of burns, especially on the parabolic ovens, because there's no flame to remind us that cooking is happening, and eyesight can be affected by being around a bright reflective object for extended periods. In addition, solar ovens don't maintain steady heat, as a light breeze will cause the temperature to fluctuate on some models. It can be challenging, to say the least, to monitor the temperature and cooking times of your food.
There are a few styles of solar ovens, and depending on what you want to cook or bake with it, you may favor one style over another. Some are simple with no frills, while others are complex engineering achievements. Here's a look at the main categories:
Box Oven: A box solar oven is exactly as you might imagine. It's usually a black box with reflective panels around the lid to aid in heat gathering. It's the most popular variety of solar cooker, as it can achieve high temperatures (up to 350 degrees F) and is ideal for general baking, but will also cook most foods well.
They're more stable, better constructed, less susceptible to wind, and have more insulation around the box than other types of ovens. They retain heat better and cook food more evenly.
Panel Oven: This is the simplest and lightest variety of solar oven. It usually consists of a pot inside a plastic enclosure, surrounded on most sides with a reflective surface, either hard panels or soft reflective material. These don't achieve very high temperatures (usually 250 degrees F max) because of the lack of insulation, so baking is a challenge.
A panel oven is the least expensive to buy and the easiest to make, and it's nearly impossible to overcook food in this type of oven. Foods with a lot of moisture do best in a panel oven. Because of its size and material, it can be stored in smaller spaces than the others.
Parabolic Oven: If there were a Cadillac of solar ovens it would be a parabolic oven. This type has an array of highly polished mirrors that concentrate the energy of the sun on a very small spot, similar to a magnifying glass. It can achieve scorching temperatures in a very short time, and it's great for grilling or frying. It's the most expensive, most complicated, largest, and most difficult to use.
For maximum cooking efficiency, the parabolic panels need to be adjusted frequently. However, because of its speed, food can be cooked and cycled through quicker, thus feeding more people.
The five solar ovens we reviewed represent the aforementioned varieties: two parabolic, two box, and one panel. With such widely differing types of designs, we focused on testing the ovens with some basic cooking tasks — boiling water and cooking some tasty sausage. We waited out an unusual spring cloud cover in normally sunny Los Angeles for a perfect solar oven kind of day. When the ambient temperature spiked at just above 90 degrees F, it was time to get cooking.
Exposing each oven to direct sunlight, we added exactly one pint of water in the included vessels and waited to see what would happen. How hot would the water get? How effective would the oven be at maintaining that temperature? Could we cook some sausages? Sure, we could, and we did with great success!
Although not all of the solar devices could boil water, that really isn't entirely important when cooking or baking. The fact that each oven reached over 250 degrees means that, given enough time, the water too will reach that temperature. And just exceeding 160 degrees will kill bacteria and protozoa via water pasteurization, so a full boil isn't necessary for that.
In fact, each oven cooked the small bite of sausage we placed in the ovens thoroughly and nicely. Side by side on the plate, you probably can't tell which piece of sausage came from which oven, as they all performed exceedingly well in this regard.
These ovens and other solar cookers like them — with the exception of the Haines Solar Cooker — aren't portable enough to take on the trail, pack in your bug-out bag, or leave tucked away in your vehicle. They're big and bulky, and some of them are fragile.
That said, there's nothing wrong with adding one of these to your cache of gear in the event that you can't have an open fire, don't want to give away your position, or have run out of fuel for a fire. This is another cooking option worth taking seriously. The energy from the sun is powerful, and it's there every day for you to use.
So, if you have the time and the inclination, don't feel ashamed to egghead out a bit and channel your inner Archimedes. And if you get one working as a death ray, our brothers at RECOIL will definitely want to hear about it.