Solar heat for your entire house extremely cheap

[iammeiamfree]

I have been testing with the black sheets infront of windows and am getting quite good results. The gains are large. The other morning I was seeing air coming off the top of the drape on the large window at 29.5 celcius and the air is gusting. It will even draw the drape in and stick it to the glass. I believe it is working well about a foot away from the glass so that there is little interaction with the glass with a good gap at the top and bottom. This is producing good heat even when the window is in the shade or there are clouds. Some windows appear to produce more on cloudy days than in shade conditions. At first I thought it would not make any difference but it makes a big difference. We have all white walls inside and the neighbouring houses are all painted white on the outside. This is to keep things cool in the summer. They have a rough finish to disperse the light. In the winter this is working beautifully because there is piles of light in all directions. Anyway with white walls inside a large proportion of the light is coming back out of the room. It comes out just as easy as it can get in. This is why you can see lights on in a house from miles away. With the black drapes most of it is not getting more than a foot in and most of the rest is getting caught on the way out. The temperatures are much higher than I have been able to get in previous years at this time of the year. I am planning to make up drapes for all the windows for a total of 17 square metres of collectors. I was trying to build external collectors but it is much easier and cheaper to use the existing windows and you get a huge panel at little cost. When they have strong light I get 4 or 5 degrees celcius warming on a single pass (up about 6 feet). The air is off towards the ceiling and away after only a few seconds and piles of it. I can feel the house go into a fortex with strong currents and over the days it is heating the neighbours house and going down underneath. On lower light conditions it still increases passing air a degree or two! and the air comes round to be reheated over and over again. The other morning there was a gail coming down the far wall where the heated air was pouring down as the heat was being absorbed by the wall. This would certainly save people billions of dollars in heating costs if it was widely used. A lot of the time the light isn't needed for anything (else) e.g. if people are out at work or in the bedrooms that are not being used during the day. If using a room some drapes can be removed for lighting but the insides of the remaining drapes will still take up a lot of that light before it has a chance to leave the room. In locations further north the production would be somewhat lower in December and January but if there is any light it is working and they still require heating in March and April when the days are much longer. They also generally have much better insulation than here and some houses could even over heat if there was too little absorption by the walls.

Cleaning the windows appears to significantly increase heat production and at night the drapes help reduce air moving over the glass and creates a cusion of cooler air there or atleast brings the cooled air down to the floor where it can be warmed by the stored heat. The inside of the room is acting as a huge battery. By making the drapes with plenty of space for air to pass in the bottom and out the top air does not warm as much in one pass but much more of it is is heated and quickly spread more evenly down to the floors. By having a bit of a curve outwards at the top the heated air rising on the indoors side of the drape appears to cause some suction and help draw the air out from the window side of the drape. The drapes may require some weighting (paperclips) to prevent it getting sucked onto the glass when there is full sun. When there is full sun however the glass and metal frame of the windows warms up so the vaccum (drape getting sucked closer to the glass) can work as an advantage as you can get high speeds of air drawing off extra heat from the glass and frame whilst being further away under lower light (cold glass) conditions.

I am planning to get hold of more fabric that is cotton as this should produce safe heat without contaminating the air as some synthetic materials would. The only concern I think is if the dyes give off any toxins when heated but if the material is intended for clothing and making drapes I would hope that is should be safe and with so much air moving over and thru the material it isn't even getting hot to the touch. I generally change all the air atleast once a day in any case. With vapour from an electronic cigerette I am able to really see what is happening e.g. how fast air is moving and which direction.

This would be a great little business to install these for people. I was thinking you know you take the measurments, cut the material and have seams sown on and hang them on hooks or existing curtain rails. Easy money.

[gtojohn]

You might try different fabrics.
Try wool, it might be too heavy but is super insulative. Or try silk, not sure if there are different kinds of silk, thermasilk long johns are quite warm, light weight. Flannel cotton might be the cheapest warm natural fabric.

[jeff5may]

What you all are discussing here is known as a selective surface. Flat black paints and fabric dyes are good absorbers (i.e. they absorb visible and uv light) but they re-radiate most of the light they absorb in the near or middle infrared spectrum. They work much like the fluorescent colors, such as hot pink and blaze orange. If you put a uv light up to these colors, they glow brightly because they are absorbing uv light and emitting it at visible wavelengths.

The dyes you are speaking of do the opposite. They simply "bend" the visible light a little down the spectrum into the near infrared. You can't see it, so it tricks your eyes, but the near infrared radiation bounces around the room just about as well as visible light.

In order for a material to be a good selective surface, it should not re-radiate much (if any) of its gathered energy at a wavelength higher than its incident temperature. For this window collector, all the energy collected should be radiated in the far infrared spectrum. The long-wave infrared is the stuff that comes off hot plates and electric skillets and buck stoves. The more energy you can emit at these frequencies, the better your selective surface is.

Here's a good list:

Heliostat Concepts

[gasstingy]

Two things are keeping me from trying this project. First of all, we have 9 1/2' of exterior roof / overhang on the south side of the building {8' porch roof + 1 1/2' overhang} and a wife who would not accept a sizable amount of flat black into the room.

Keep in mind that it's always easier to increase the home's temperature when other heat sources such as space and radiator heaters remain active... Once you turn everything off and rely only on one source, the true story emerges.

Now I save money the old fashioned way, too.
By dressing appropriately for the climate.

You don't wear warm clothes in my house, you will be uncomfortable.

[ecomodded]

Somebody forgot to wipe down their Remote !

Originally Posted by ecomodded

Somebody forgot to wipe down their Remote !

This may be hard to believe but there is no remote for that thermostat.

[ecomodded]

might be for the best , they tend to get lost fast with more than one person in the house and especially with children around.

I will go away now..haha

[ThePrudentNinja]

Heating your home with solar. Something I experimented with a little last winter.

My results: open curtains in the day and closed at night seems to work, but I found a better method. Similar to what "Solar" has said, I put black cloth over the windows. I left a 2-3in gap at the top and bottom. I covered the entire window when the sun stopped shining on it. The effect I noticed was the sun would heat the black fabric and the heat would rise into the room. Using a ceiling fan helped distribute the warmth. On the majority of winter days, I was able to keep my whole house warm (60+ degrees F) when the sun was shining (in other words, I didn't use any other form of heat during most winter days despite temperatures outside being between 20-35 degrees F). I didn't manage to figure out any worthwhile solution to STORING any heat and had to use supplemental heat at night. My home is setup in a rather useful way. Half the windows are on the south facing side and half on the north facing side. In the summer I can block the south windows and leave the north windows bare and it helps keep the inside temps a little cooler. The best effect I've seen this summer is 10 degrees cooler inside than outside without the use of any air conditioning (using ventilation through the north side windows with the help of nearby trees). This winter I may attempt a little more "radical" solar heating setup just to see how well it works. Basically a large exterior box to collect solar heat and pump it into the house. Still not sure a good way to store any collected heat. It helps though that I have low ceilings and a large south facing exposure compared to the square footage of the house (think rectangular).

Now, the "average" BTUs in sunlight on an "average" day is around 300 useful BTUs per hour per square foot. If you halve it, that's still 150 BTUs per hour per square foot. A watt can be turned into 3.412 BTUs. So a square foot of area could realistically see about 44 watts worth of heat on a winter day. The exact amount can vary WILDLY depending on so many factors. Just roughly estimating here and trying to be conservative.

So, let's assume you have a room that is 100 square feet and of "average" insulation with 7ft ceiling. You will "typically" need about 7,600 btus an hour to heat it in a typical cold area of the USA (sorry Canada, this example is not for you). This figure too can vary WILDLY. So you would need about 50 square feet of solar collection to heat that room entirely with solar and be pretty dang sure. Of course this will only be during sunny days when the sun is actually shining on the collector. So, you would need a collection area of roughly seven feet by seven feet. Using a typical window, the collection box could be about 3ft by 16 foot. So in theory for a 100 square foot room with a south facing window, you could heat it entirely with solar by having a roughly 3ft by 16ft solar collector. You could also just install a bunch of windows lol.

Can a home be entirely heated by solar? Of course. Can a typical home be heated entirely by passive solar? Probably not without a lot of work. Can you save money by using solar to help heat your home? Of course. Just realize one typical south facing window in a room will not do all that much if your house is not heated by other means. It's still worth it. For a typical window, you could gain about 2200 BTU/hr of heat that doesn't cost you a penny. Almost like a 650 watt heater running. About 75-80 kWh a month of free heat if you get four hours of good sunlight every day. Of course you will probably get closer to 50. For me, that is $5 a month I could save for one room by spending roughly a few minutes a month opening and closing the window curtain. Multiply that by however many windows you have that can get good solar. Not bad and worth it to me.

The issue with solar is it isn't a steady constant source of heat. If you get a string of cloudy days, you will be using some other form of heat. A rocket stove mass heater may be a better solution for small homes. Not sure about large homes. Of course the best solution would be to build a house to be heated passively by solar, store the heat for the night time, and be passively cooled in the summer. Earthships come to mind (and boy can they be pricey).

If I made errors in my stats/calculations, forgive me. It's late, I'm tired.

[Barrowman]

As the temperature of the heat source increases the wavelength of the light( and heat ) gets shorter. As the sun is so hot the light easily passes through the glass. When it heats the black material up that starts to radiate but the wavelength is much higher than from the sun and it doesn't pass through the glass so well. A very good article is at https://phys.libretexts.org/Bookshel...body_Radiation.