Solar Cooking Archive Discussion Forums

coconino · Joined: 21 Nov 2006 Posts: 77 Location: Sunny Brixton

It�s been lovely sunny weather here over the last few days but I�ve not been able to take advantage of it to get out with the cookers. However, the wind has been quite strong so it might not have been practical; these cardboard cookers tend to catch the wind.

Looking at the sky got me thinking about rules of thumb for gauging how the cooking will go. From my few experiments it seems that what the weather forecasters call �sunny and warm� doesn't tell the whole story. I�ve observed that it is when the sky is blue and shadows are sharp-edged that cooking goes fastest, and on other �sunny� days the sun may be strong and bright but the sky is whiter rather than clear blue and the cooking has taken longer.

It seems that slight diffusion of sunlight can have an effect, but without a pyranometer I can�t say precisely how much, so I was wondering if anyone here could point me to any data on this subject? I�d be very interested in any rules of thumb which have been derived from such data, something perhaps which used a baseline of blue sky and sharp shadows and added (for instance) thirty minutes to cooking time if the sky was sunny but not blue, and another thirty if there was high cloud. I realise of course that exact conditions vary due to factors such as latitude, time of day, type of cooker, insulation, etc., but I would be interested to know what those with more experience have to say on the subject.

coconino · Joined: 21 Nov 2006 Posts: 77 Location: Sunny Brixton

I found this site which gives excellent descriptions of cloud formations, and I think what causes the white sky I was trying to describe is a cloud type called cirrostratus nebulosis, which is given as �extremely thin, with vague edges that are difficult to discern and a lack of the texture or fiber common to other cirrus clouds� and with this type the only sign of cloud formation will often be just a slight diminution of the intensity of sunlight.