Solar Ovens

Can you think of another explanation then?

Yes. It converts sunlight into usable heat, instead of just illuminating the room and reflecting the light back outside. The reflectors bring more light inside, so you get more heat that way as well. If I were to have the interior of the heater painted white, it wouldn't generate heat, but because I use black metal the light gets converted to heat and warms the house more than it would if reflected off of my white walls and carpets.

It is simply storing heat that would not usually be stored :)

"(3) prop the board so that it reflects as much sunlight from the winter midday into the window [the board should be about as big as the window]"

I suspect the midday sun in your location is probably *above* the horizon year-round, so if you are mounting a reflector *beneath* the window to reflect sunlight through the window, you should probably angle it to reflect the suinlight *upward*.

The exact angle that will work best will depend on your latitude, the compass orientation of your house, and any nearby obstacles to sunlight.

Go outside at noon and adjust it.

Suit yourself. I found that a single reflector did the job of keeping the house comfortably warm. I once saw plans for a solar oven for baking (bread, cookies, etc) that was basically a glass-fronted, foil-lined box with three such reflectors around it. Properly angled and faced towards the sun you could easily cook food with it. I don't think you want *that* much heat, though.

Tom Davidson Richmond, VA

Black surfaces in general absorb radiation better. White surfaces reflect an appreciable fraction. But if that light does not bounce back outside, it goes to make the same amount of heating. It may not be obvious....

Brian Whatcott Altus OK

I have a specific question. My solar heater is tall enough a person could stand inside, and just wide enough a person could squeze their shoulders into it. It stretches up a window of the same size, that is tall and faces the south side of my house.

Right now it is 12:25 and the temperature just above the solar heater, where I have an opening in the top is 80 degrees farenheight.

Do you think that this heat is going to help warm up the house? When I put my hand down into the heater it is even warmer. Should I find a way to blow the air out of the heater, so it circulates into the house?

Also, I've been measuring the temperature in the house. In the large living room where the solar heater is the temperature has been staying at 70 degrees F, and in the rest of the house it has been staying at 65 F.

There's your problem. You need to collect the sunlight from an area LARGER than the window and let it in through the window.

You are trying to *HEAT* your house.

You are trying to GET the heat from sunlight.

You need to get MORE sunlight into your house than you normally would for the heat to accumulate inside the house.

If you look at the design of the through-the-wall solar oven you linked to earlier, the oven collects sunlight *outside* the souse that normally would not enter the house, and brings it in.

I am not sure how your solar heater is designed, but if you open the bottom on the outdoor side to let cool air into the hteater, and then open the top of the window to let the warm air into the house, then convection should be enough to get the air to flow.

You still need to gather more sunlight than the window would *normally* gather to get any heating benefit.

Tom Davidson Richmond, VA

OK here's a low, low cost solar heating method. Assuming you have a pitched roof, you put a clothes dryer air exhaust hose in the peak of the roof , with a little fan sucking this air into the lower rooms. Ideally, you control the fan with a little box that senses temperature of 75+ in the roof peak, and temperature below 71 in the living room before turning on. That warm air assist from maybe 400 sq feet of solar heated roof could provide an extra 10 kW of warm air. Worth 50 cents per hour. Say $20 / wk. Set against that a $50 set up cost for the blown air.

Brian Whatcott Altus OK

Dear Brian Whatcott:

The problem is, where heating energy costs are high, the under-the-roof temperature never gets above 45 deg even with the Sun out. And this intermediate temperature, if harvested, puts colder air adjacent to the (apparently) poorly insulated ceiling, providing a net heat loss.

The best solution is to move where it is not that cold in the winter. But somewhere there is water.

David A. Smith

$20/wk does NOT qualify as 'low cost' when a total investment of a few dollars (aluminum foil, large used cardboard carton, tape) will heat your home *all winter*.

Tom Davidson Richmond, VA

///

Well, I have done solar heating in a cool climate, and done roof evaporative water cooling in a hot climate and I've measured under roof peak temperatures - I found they can get quite high. Don't understand why you would never measure more than 45 degF in Sunlight. I suppose that's equivalent to saying there are places where the hottest day temperature is less than 40 degF. That doesn't apply anywhere on Earth as far as I know?

Brian Whatcott Altus OK

Now hang on a durn minute! I proposed $20/week SAVINGS at a putative one-time cost of $50 Are you pushing trhe idea of carboard and foil ovens inside the house still?

Brian Whatcott Altus OK