Solar Ovens

The light that comes in through the windows _already_ heats your house. What you need to do to make it work is to get more light in through your windows; basically, turn your whole house into a solar "oven" (but not quite as hot!).

You could use reflectors to do that. They'd have to be outside.

You might be interested in looking at energy-efficient house designs; often they have large windows which are shaded from middle-of-the-day sun in summer, but not in winter. Of course, you might not be wanting to build a new house, but some ideas, such as moveable awnings for controllable shade, skylights, etc., might be useable.

Depending on how ventilated your roof cavity is, you might already have a nice solar oven attached to your house. Perhaps you could use a fan to move some of that hot air downwards to where you want it in winter?

Like Timo said, your house is already a solar oven. If you want the sun to heat your house more efficiently, you could always put in black flooring in the areas where the sun comes in. That would help to heat up those rooms. Another thing you could do is to put in some windows that have a high R value. You could also install more insulation/better insulation (high R value) and that way your house wouldn't lose much heat during the day. I would also suggest growing some large trees on the south side of your home (assuming you are in the northern hemisphere) so that during the summer you don't have as much sunlight heating up your house.

I just built a solar heater in one of my south facing windows. I used

3 tall mirrors, and placed on of them at an angle with the window and the two others along the sides of the windows. I then covored up all the holes with aluminum foil, and put a black piece of metal along the floor of the heater. I put a tiny fan in the heater to blow the hot air into the rest of the house, and covored the whole thing in a sheet for looks.The sun is starting to set now, and it isn't very hot, but during the day it was cooking in the heater.

What makes you think this isn't going to help heat my house? When the sun shines in through the windows it mostly just lights the house, and the heat gets lost. With this system the light gets trapped in the mirror box, and converted to heat. It then gets used to heat the house.

What heat is coming from the solar heater that hadn't already entered the house?

Assuming deciduous trees If you really want to get into it - borrow, hire, etc. a thermographic camera and identify where heat/cool's coming in and going out - fix-up whatever you can and get out the thermographic camera once again - repeat seasonally until your totally satisfied (If your in Australia, you can pay us to do it).

All of the sun light that the mirror box converts to heat, that would otherwise just illuminate the house and eventually escape and get lost without heating the house at all.

How would it escape? Some small amount would reflect back out the window, but the same is true (perhaps more so) for your solar box, no?

When light illuminates common surfaces (rather than perfect mirrors), it is partially reflected and partially absorbed. The absorbed portion is degraded to heat.

It seems to me that concentrating the heat in the solar oven only serves to create on spot that's significantly higher in temperature at the expense of other areas in the room.

Of course, you could then use this concentration of heat to move it to remote areas (ducted fans, for example).

Perhaps you should consider building your solar oven outside, and ducting warm air in. That way you'll be bringing in energy that would not have otherwise entered the house.

I think what you would really want to do is convert an entire wall (sun side of course) to be the "solar oven" for best results. :)

I wish I could do that, but I don't have the materials, and already have a house with a good wall I don't want to tear down. Spaceman, do you have any ideas I could use to improve what I am doing already?

That was my origonal idea, but the work involved in creating that system is more than I have time and energy for right now. What I am doing inside is an expiriment, so I'll get back to you on how well it works tomorrow when the sun comes back out.

You'll probably want to measure the room's temperature with and without the set-up. Shut off heating to the room and keep the door closed to minimize heat sharing with the rest of the house. You might also put a fan in the room to mix the air.

Or, I could build one of these into my house:

is a solar oven built into the side of a house)

Not really Besides gathering more light to enter the window. (ugly mirrors outside that only work part time unless you actually get them to move automatically with the sun) and maybe,.. You also have the option of building upon the wall with cheap materials that would still get some of the job done.

It is all a matter of money though sadly. :(

Apparently you just haven't gotten it yet.

If you want to *heat* your house during the winter with soalr energy, you are going to *ahve* to get more sunlight into your house that it would normally get.

The solar oven you linked to that is built into the side of the house catches sunlight that is *outside* the house and stores it in the cookpots. Then when the oven is opened from the inside of the house and *especially* when the pots are brought inside, the added heat comes with them.

You may want to try building an *anti-awning* outside a south-facing window: (1) Cover a board with reflective material. [cardboard and aluminum foil will work to prove the principle] (2) mount the board outside the house with one edge *beneath* the window (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] (4) leave the window shades open all day

If you do this right, the *extra* sunlight coming in through a single window will make the room almost unbearably hot, and with the help of a simple fan to circulate the heat could heat a three-bedroom house.

It worked for me a few years ago in Brighton Colorado all winter!

Tom Davidson Richmond, VA

What angle should I prop the board? I have a lot of extra sheet metal which is way more reflective than aluminum foil I can use. Do I want it to be at an upward angle to the window ( \.| ) or a downward angle ( _.| ). Also do you think I could make some of these on the other sides of the windows as well?

It worked for me a few years ago in Brighton Colorado all winter!

Tom Davidson Richmond, VA

Sunlight which enters the house and does not reflect out again, is absorbed completely on surfaces which it touches. No ovens needed. The trick is to allow sunlight in, in a controlled way, to store it for overnight reemission, while not allowing warmed air to escape.

People have used black drapes, or water bottles (lots of em) and blown the warmed air into rock box reservoirs.

Brian Whatcott Altus OK

To *some* extent that's true, but the loss is small. This is the reason why glass greenhouses work, and you'll note that the inside of the greenhouse doesn't have to be painted all black for the warming to occur. The reason for this is that light entering into a greenhouse is generally downshifted on reflection to be more toward the IR, which glass is more impervious to. So the light comes in, but it can't escape through the same route.

Now in your device, the light is trapped and converted and confined to a small volume, whereas in the house the *same* light is dispersed through a larger volume. Since the heat is confined to a smaller volume in the device, it gets *locally* warmer than the surroundings. But if the device weren't there, the same amount of heat would get deposited, just in a more distributed way, and so you wouldn't notice a local temperature increase.

PD

PD

I uploaded some photos of my solar heater to Image Shack.

Outside Reflectors:

The Box Inside: I put 3 big reflectors outside of the window, and inside have two mirrors that direct the light to a tall piece of black metal. The black metal gets really warm, and heats up the air in the box, which then escapes out the top of the heater.

The air inside the box is much warmer than the air in the rest of the room, and I don't feel this is only because the heat is getting concentrated.

Just so you know, the "solar oven" idea simply takes a given area (about 1/2 a square meter to about a square meter) and focuses the sun's energy (about 1000 W/sq. meter) on a *smaller area* to increase the temperature (but *only* to this *smaller area*, the focal point).

If you do this on the inside of your house, you'll only notice the increased temperature as you get closer to your "pot". Total energy input is the same as if you've never built the solar oven: 1,000 W/m^2.

Now, if you *surrounded* your *house* with mirrors and focused the sun's rays on your house, now that's a different story... :)