Since writing my first post about solar ovens for backpacking I’ve been longing to try out my own DIY solar oven, but this has been a very wet and cloudy Spring. Literally we’ve had one day since I built my test solar oven rig that was clear enough weather for solar oven cooking, and I wasn’t able to cook that day. Instead I cooked yesterday, with results I’ll get to in a moment.
I think solar ovens are a great idea, but my initial skepticism of whether they’re great for everybody is just getting confirmed. There are many solar oven problems which can go wrong and probably will. If it’s really cold, for example, you can lose as much heat as you gain from the simplest versions, which are not much more than foil reflectors and a black cooking pot set on a stand in front of that. If it’s really windy, you’ll have an awful time getting that reflector to stay put. But for most of us the ultimate problem will be clouds and haze, which has pretty much eliminated any opportunity for solar cooking where I live for the past month. Today’s no different, with cloudier weather than yesterday.
I still like to tinker with things and making a solar oven didn’t seem too hard. Using a two dollar styrofoam cooler as an oven base, a section of copper tubing as a hangar for the cooking pot, and a fold-up reflector that I bought to put in the back window of the car last year I managed to put something together that ought to work when the sun does come out. I haven’t found a cheap black pot as yet and now I’m thinking that’s a critical component. I’ve cooked in brown paper bags before and thought that might work well enough here, and on a good day it might.
The reflector is sewn to the cooler with flexible steel wire we used for a grape trellis a few years ago and had laying around in the garage, so the total cost of my project thus far is two bucks plus found materials. I guess add plastic cooking bags to that, because I used two of them also.
When I set the solar oven up at 11 a.m. the conditions were great, a clear blue sky and hot sun glaring down. The copper pipe was too hot to touch by the time I put two cornish hens in a clear plastic baking bag. To increase heat retention I put that in a brown paper bag and hung it on the pipe. Then I laid a clear layer of cooking bag over the top of the oven base. Using the solar oven seemed simple and the solar cooking experiment appeared to be going well.
The sky soon filled with high patchy white clouds and only occasionally yielded stretches of clear blue over the next two hours. When I checked the solar oven temperature by poking a thermometer into the cooking zone, the oven had only produced a pitiful 110 degrees F of heat, perfect for breeding the best tasting bacteria a chicken ever carried.
After a moment of weather predicting I set up the little charcoal grill and lit the fire. While the charcoal got going I had a chance to observe the oven at work while the sun peeked through the clouds, and the internal temperature of the oven rose to about 150 degrees in that short period of time. To eliminate the chances of food poisoning, the temperature of the chicken needs to be above 160 degrees F, so that wasn’t such a good deal. When I took the chicken out of the cooking bag it was only about a hundred degrees. Nearly three hours in the solar oven had only warmed it up.
Several things could have helped. First, a black cooking pot sealed in the cooking chamber would have heated up better. Two cornish hens was at least one hen too much for this size of cooker. Steady merciless sunshine is going to be completely essential for safe cooking of poultry and other meats, beans, and if you want to be smart, everything else.
A hour of slow cooking on the charcoal grill, with the grill’s cover holding the heat in and the fire burning so hot I couldn’t keep my hand near it for more than a few seconds, finally raised the internal temperature of both chickens above 160. A few more minutes took it up to 180, which made me happy. Fire’s a great thing to have around.
For more about solar ovens for backyard cooking and camping see my post about LightStoves.