Yesterday, with a clear blue sky, the GSO took only an hour to warm up to 275 degrees Fahrenheit (from 9:45 to 10:45 AM). I took a butternut squash from my cold storage room, stabbed it multiple times, and placed it on a baking tray, with a black cloth draped over it to increase heat-gain. Then I placed it in the pre-heated sun oven. Over the next few hours, I rearranged the GSO three times to aim it toward the sun, noting that it reached 300 degrees over the course of the baking time. The squash was really, really roasted by 1:45 PM. We used it last night to make butternut squash quesadillas.
The GSO works only marginally well during the three winter months at my latitude in Oklahoma City- from about mid-November until mid-February. It still works, but it takes much longer to warm up, and does not reach the same high temperatures that it does in spring/summer/fall. Also, since you have to jack up the back end so much to get proper sun-gain, it is a little more prone to falling over in high wind. On windy days, I would stabilize the box with bricks around the base, which helps to a certain extent. In a desperate situation, you could definitely still use it on sunny days, but you would have to plan your meals very carefully.
I've missed my Sun Oven! I love it for roasting butternut squash and baking banana/zuchinni/apricot nut bread - although I use it for much more when the solar cooking season is nigh. My banana bread seems to get a little drier and a little crusty around the edges when I bake it in the regular oven. But in the sun oven, ah! Moist perfection, with no worry as to how long I leave it in. In the regular oven, I have to cook the bread within about 4 or 5 minutes of the exact time. In the sun oven, I can leave it in for quite a ways longer - I would say at least an hour past when it finishes cooking.
So I'm glad to see the Global Sun Oven back in action. I hope I will be able to include some kind of solar cooking classes or demonstrations in our Transition Town work. It's such an amazing device, and yet so few people know how well it works. Especially, I find, if they've tried to make their own solar cooker at home. From what I've heard, the home-made solar cookers don't compare very well. Usually, they are a little flimsy, only heat up to about 250 degrees, and take a long time to cook the food. For me, it's worth the money for an appliance that works like a regular oven (at least when it's sunny). OTOH, it's also worth knowing how to make a solar cooker in case of an emergency.
I think a sun oven is worth having even if you plan to use a woodstove as your main source of heat and cooking. It will get pretty roasting hot in the summer, (or fall and spring if you live in a warm area), and it won't necessarily be so pleasant to cook with a woodstove at those times. Much better to cook with a sun oven, using no wood in the process, and keeping the house cool!
Maybe tomorrow I can cook some banana bread. Anybody out there have solar cooking in their plans for this year?