2% Sky Cover!

A high pressure weather system has been centered over Texas. The National Weather System’s graphical map indicated 2% Sky Cover. Not a cloud in the sky! The Helios baked bread, zucchini loaves, squash, potatoes, beans, rice, cakes, including an angel food cake, and several chickens. The cracked microwave turntable 1/4" thick glass cracked even more, and fell to the ground. We replaced it with some 4" wide strips of optically clear glass that had been recycled from junk Xerox copy machines. The strips cracked, and fell out of the frame. Even without any glass on the front of the oven, it still reached 450 degrees F. Here is a photo of the oven with the door open:

The oven door needs to be "made pretty" yet. Perhaps an alumimum sheet over that fibreglass, with a shaded box to hold my temperature meter. I did drill the hole for the thermocouple so the sensor will be located near the center of the pans placed on the upper shelf of the oven. The dimensions of the oven, are 22" at the bottom, 22" on the right side, 22" deep, and at the top the dimension is 12" (because of the steel plate). Currently, there are three rack or shelves, which came out of an expensive Jenn Aire Electric Stove, thus they are standard oven racks, just turned sidewise. Since I have them wired together, they are not adjustable. The heavy steel plate had some rust on it, so I covered the upper part in the oven with some aluminum foil, and held that in place with a cookie sheet. (In case you are wondering why it is between the steel plate and the oven area.) We cooked some potato slices brushed with olive oil and mrs dash seasoning, and a bit of rust fell on a few of them! Bad news..some one else discovered the rust (wife)..good news...it brushed off, and the potatoes were delicious! The aluminum foil will prevent that from falling onto the food. The oven seems to be working quite well without any glazing. The mirror array is directing the light onto the steel plate which is deep inside the insulated box and protected from air currents. If my cart would hold more weight, I think I would look for a several hundred pound block of iron to use instead of the steel plate and chunks of iron I have now. Might not even need the glazing?? Also, a large hunk of insulation could be placed over or in the stainless steel ring to retain the heat stored in the thermal mass of the iron. Here is a photo of the array taken one evening after a baking session. When I looked at this photo on my computer, a very interesting pattern was visible.

The mirror on the far right end of the second row had an adjusting bolt in the spider that was too long so I had removed all pressure on the mirror by backing out the bolts. The mirror was flat when the photo was taken. Some of the other mirrors show strange patterns, that I will have to think about.

Here is a photo of my mounted cable adjusting pulley system, as explained in a separate article. (I guess I could replace those C-Clamps with bolts, now that it is working well.) Each pulley adjusts two rows of mirrors. Before solar noon they need to raise the focus point on the oven approximately every ten minutes. In the morning, I set the "solar bright light" at the upper right corner of my entrance hole (for light/heat) at the front of the oven. In about seven minutes, it has moved to the lower left of the entrance hole and needs to be adjusted back to the upper right. At that time, the oven needs to be pushed or pulled to get the beam back to the right side of the entrance hole. The pulleys only move the mirrors up or down. Before solar noon they are cranked up, and after solar noon, they are cranked down. In fact, for oven use, the round entrance hole on the front of the oven could be replaced with a wide slot on the diagonal from upper right to lower left on the oven. Before solar noon (1:30 p.m here) I set the beam on the upper right edge of the front of the oven, and set my timer. In ten minutes, it will have moved to the lower left of the front of the oven. Some of the time, it will cross dead center, and the iron and steel will accumulate maximum heat for the oven. It is actually more convenient to cook an evening meal in the oven, because by 6 p.m., the Helios doesn’t require much tracking adjustment, and the oven is really hot. At Solar noon, I need to pull the oven several feet, and crank like mad on the pulleys. (In the evening, the beam keeps rising up on the front of the oven. In the morning, it keeps falling off the bottom of the oven, smoking the paint on the sheet of steel protecting my carriage wheels..) If the weather wasn’t so dangerously hot, one could find chores to do in the vicinity of the oven.

Sky Cover forecast from the national weather service. Here is a screenshot: Notice the blue graph in the bottom section of this photo. It shows my current sky cover at 40%, which means that sometimes when my timer "dings", and I run out to adjust the tracking, there is no sun to track. For the last five days, the sky cover was at 2%, and that is probably why everything got hot enough to bust up my glazing ;) Here is a link to my weather forecast data: http://forecast.weather.gov/MapClic...

Here is a site that will show you the Surface meteorology and Solar Energy data for your location: http://eosweb.larc.nasa.gov/cgi-bin... Check carefully to see how many hours of clear sky you might expect each day. My site is probably not ideal for solar energy, so we bake four loaves of bread at once, lots of vegetables, rice and beans etc, when the sun shines. Then we can go for days without cooking. If we need to cook something when the sky is overcast, but not raining, then we have a series of very efficient cook stoves that can be used to fry or boil food using only a handful of bio-mass. I may need to write another article on "cooking without the sun". Maybe " Cooking with Carbon Monoxide"? One situation might be where the weather changed, and we had four loaves of bread already in the oven, but solid clouds and no further chance of sun. Then, perhaps a small wood gas unit (my smallest stove) with the flame directed into a pipe running through my solar oven. Has anyone seen exactly how this works in The Villager Sun Oven? (which offers propane backup.) http://solarcooking.wikia.com/wiki/... With iron and steel as thermal mass, and a gas burner backup, the baking could go on and on...Did I mention how much I like to eat Biscotti? When our chickens are really laying well, we often have too many eggs. The angel food cake uses 2 cups of egg whites (about 1 1/2 dozen blue eggs), and reduces our excess egg supply. It is nice to have the baking done outside, else the house would be even hotter than it is. (Subtropics in July/August can be miserable!)