Last edited: 12 November 2014
Cooking with the sun at 58° north latitude. I never knew such a thing was possible!
Garden plants were and still are a great hobby of mine. I searched the net for garden plants, and came across a site called Plants for a Future. There was, among others, a link to an ecovillage site, very interesting, and there was some mention of solar cooking and a link to http://solarcooking.org. I found the plans for solar cookers very interesting, and since I had some time at my hands, I started fooling around with cardboard and aluminum foil at once. Of course none of the plans were designed to solar cook in the far north, but it would be fun trying. I never really imagined that it would be possible to cook a full meal at 58° north, but at least it would be possible to show my science pupils something about solar energy.
Surprise, surprise! They work here too!
First I made a CooKit and a Reflective Open Box cooker (ROB). This was at the end of February, the sun was low in the sky here at 58° north. There was snow on the ground, but the ambient temperature was on the just above freezing. I realized that I must tilt the cookers to catch the low sun rays. I used half liter fruit cans for cooking pots, and put them in clear plastic jugs for insulation (greenhouse). The ROB brought the water to an active boil, the CooKit got to 91 °C (196 °F).
Now I really got interested. I searched for more information and plans, and decided to try to make a Heaven's Flame cooker and a Twelve-Sided Parvati cooker. Then I made a bigger Parvati too, 80 cm diameter.
The problem of stands
Now the real challenge was to create stands for these cookers and the cooking pots. Here in the southern part of Norway ( in northern Europe) the sun gets to a little less than 55° above the horizon at noon in midsummer, and to a little more than fifteen degrees in midwinter. It would be really useful to be able to catch low sun rays. With help from the local blacksmith, the stand for the 80cm diameter Parvati was made. The 60 cm diameter Parvati got a stand made mostly from wood. I used an old baby carriage for the Heavens Flame.
Now for the cooking of real food!
The suggestion from Prof. Roger Bernard to use a salad bowl to keep the heat in around the pot proved really helpful. I made soup in the Heaven's Flame, and cooked rice in the Parvati cookers. Delightful! After a while I used the Parvati most, because it needed no turning for two hours. I made casseroles, cooked potatoes, vegetables and fish, and even made bread which tasted really good.
But what if the sun shines for only a short while, and the temperature is below freezing point?
Obviously some sort of parabolic dish would get the food boiling much faster. I looked at the SK cookers from Germany, but was surprised that they needed so long to get one liter of water to boil. I thought that some sort of greenhouse would shorten the heating time and make it possible to cook in winter when it was cold. There is one picture at the SCInet website of a parabolic dish with a black pot placed inside some sort of glass bowl. This idea stuck in my mind, so I decided to try as soon as I could find a way to make or get such a dish.
Then our local TV salesman generously provided me with a discarded dish. It is 120 cm wide and 130 cm high. It is not a symmetric dish, so when I had covered it with kitchen foil and directed it towards the sun, the focal point was very low, and the pot got all the heat from above, which I did not find practical. Then my husband helped me to make a stand from old bicycle parts. We turned the dish and made a hanging arrangement for the greenhouse and pot. Now the heat comes from below, like it does on an electric stove.
Caution: Using a recycled satellite parabolic dish requires careful use. Because this style dish has a shallow curve, it places the focal point quite high, close to the user's eyes. Looking directly at the dish from this location can cause severe eye damage. Most commercial parabolic solar cookers use a deeper profile curve to contain the focus point more closely to the dish.
Trying to be scientific
First trial: October 23 2005 at 3:00 p.m., ambient temperature 7 °C (45 °F). One liter of water boiled in 14 minutes.
Second trial: December 17 2005 at 12:05 p.m., ambient temperature -6.8 °C (20 °F). One liter of water boiled in 25 minutes.
This proves that solar cooking is not only for hot climates. Even people at high latitudes, e.g., Canada, northern Europe, northern Asia and southern South America can use the energy from the sun in more ways than we previously thought possible.
Brit Bakken Oedegaard is a solar cooking researcher and school teacher in Norway.