Keeping the Heat Out: baking in a solar oven


I’m addicted to low-tech gadgets. In a former life I studied ecological agriculture at MacDonald College (a campus of McGill University) with Dr. Stuart Hill (who has since moved to Australia). In our classes Dr. Hill was always going on about elegance in the design of systems and technology. The height of elegance is a simple technology that needs minimal energy or uses waste products to run, generates little waste of its own, and is easy to use, maintain, repair, and replicate. A passive solar oven is a perfect example of elegant low-tech design.

In a previous post I discussed some of our strategies for reducing the amount of solar heat that enters our house in the summer. It’s also a good idea to reduce the amount of heat being generated inside the house by appliances.  Baking in our natural gas-fired oven, for example, is a bad idea on a day with a predicted high of 30 C. But what if you have a hankering for some fresh-baked muffins, roasted baby potatoes, or bread pudding. (Can you tell the pre-lunch munchies are setting in?) A solar oven seemed like an elegant solution. I couldn’t find an Ottawa source for one, and sadly I’m not much of a DIYer, so after doing a bit of research I ended up buying a Sun Oven on-line straight from the manufacturer.

On a clear sunny day in Ottawa, the Sun Oven maintains an internal temperature between 325 F and 350 F from about 10:30 am to 3:30 pm. As all you cooks out there know, this is a perfect temperature for baking. For those few items that require slightly hotter temperatures, I just let them cook for a longer period.  This usually works, though I once had a banana bread that refused to cook all the way through.  The baking chamber is sealed shut to keep in the heat, which has the added benefit of sealing in moisture. Of course if you want crispy this is a disadvantage, but every technology has its pros and cons.

Speaking of cons, there are some challenges to using the Sun Oven. The main one is that you have to adapt your cooking routines to the sun’s schedule. This can be a problem if you work a 9 to 5 day or if you want your supper to be brought to the table piping hot at 6:30 pm. I mostly use the Sun Oven for baked goods that can be eaten after they are cooled or for roasting vegetables that I’ll throw into a salad or sandwich.

The other problem with relying on a solar oven comes from the tendency for haze and smog to accumulate in Ottawa skies during the summer. The best temperatures are achieved under clear blue conditions. Clouds, haze, and smog all reduce the sunlight reaching the oven and consequently lower its temperature. Fortunately this year smog and haze have not been a problem, though clouds certainly have been plaguing us lately.  Still, today looks like the perfect day for elegantly baking under the sun.

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