Utilization of alternate energy sources

Can you be more specific on what you are trying to accomplish? It sounds to me like you want to allow the inward passage of IR energy, and then trapping it in the room, kind of like a miniature version of the greenhouse effect. If that is what you have in mind, double glazing can do a decent job of it.

Thanks Darth

See my answer to Sparkstation. I am impressed with both of you. Where can one get double glazed glass. I might even get "hairy" and mount thermocouples on two versions--or even three[one with no one way street]----------BillZ

Hello bill zantow,

There is special glass, which has a special metallic coating, and transmits radiant heat mainly one way only.

This glass is often used for the "viewing window" in log (wood) fires.

It reflects the intense Infra-red heat radiation inside the firebox, allowing the happy home owner to watch the flames.

You see the difference when the door is opened on a glowing amount of burning logs, because the heat almost scorches one's face.

Please see here:

Scientists Formulate Intelligent Glass That Blocks Heat Not Light:

http://www.sciencedaily.com/releases/2004/08/040815234512.htm

This coated 1 way heat reflective glass, and other similar glasses, are commercially available....

Thanks Sparky

This is my first entry and I am impressed by the quality and quickness of the responses. I am on my way with your answer! Visualize a box 10"/21"/24". The 21/24 face fits in the opening of a south facing window. A flat black panel at 25deg from the vertical [I am on Cape Cod at about 42deg north of the equator] will be inside the box facing out. The back of the panel is finned and room air can flow thru the fins via vents at the top and bottom of the box. the flat black will re-radiate and it would be good to trap that energy in the box with your "special glass". What do you think? I'll let you know the results------BillZ

Thanks Guest, SparkY and Artbyjoe

I am getting an education here. I need something that passes ultraviolet and reflects IR. Glass is good. Is there anything better? I will try the stove glass that somebody mentioned. I think I need to do some experimenting---two or three small boxes in the same window so that other conditions are constant and some instrumentation.

Hello again bill zantow,

If you are intending to "heat your house" with that size box to the above design, the quantity of heat you receive will be insufficient to heat the house adequately.

As the heat is removed from the box, via "finned black painted box back", you will get heat into the room or ducting, but the total heat amount will be very little.

For your situation, perhaps a Trombe_wall , along with heat storage media (20 tonnes of gravel) with the trapped and warmed air blown through it, may be more useful, though more costly, and rather inconvenient.

Of course we don't know the quantity/temperature of actual heat you require.

If you advise further, you may be helped more....

Thanks SPARKY

I am sure you are right . I won't mention what kind of a hole in he snow this will make. If it will take the chill off a seldom used and unheated room in this 175 year old house and its fun to do it I will be satisfied. I had a ball last year making an outdoor-shower-water-heater that really works. We live near the beach and have a bunch of sandy kids to contend with. The glass may help with that heater and I will find out with this project.
-----BillZ----

hi,

if i was wanting to heat the air in my house i would use what we used to call solar chimneys. it now has a different meaning. but here is link to a solar dehydrator, that is similar.

basically it is an angled wooden structure, with a clear plastic face, painted flat black on the 3 inside walls. you build it so that it sets in a partially opened window, completely filling the window width. then you just pull the window down to it. the longer the chimney, the more heat it collects. of course this should be on the south side of the house.

one version is open on the bottom and the top. this takes in outside air and heats it up as it travels up to the window, releasing its heat at the top. and it does rise.

an improved version is a double stack, with the bottom closed to outside air. the bottom space is vented to the top space at the bottom, making a cold air recirculating return to the solar chimney. thereby reheating the air in the house. works even in snow country. because the black paint absorbs the long light waves, reradiating as short waves, which heats the air, causing it to rise.

for best effect with the double stack, i would cut an opening in the wall, and mount it such that the lower level, would be flush with the floor.

or you could use ben franklin's method. put cold air return registers around the house and duct them under the house to the bottom of the chimney. the reason this is better, is that warm air then moves TOWARDS these registers, warming the far corners of the house.

best of luck, and welcome to the alternative energy world.

"the black paint absorbs the long light waves, reradiating as short waves, which heats the air, causing it to rise."

Assuming 'long' refers to wavelength. you have this backward. The black paint absorbs UltraViolet and visible, as well as InfraRed light energy, re-radiating it as mostly InfraRed. The Ultra- and Infra- refer to the energy or frequency of the photons. High energy photons (UV) have high frequency and short wavelength; lower energy photons (IR) have lower frequency and longer wavelength.

BTW, what we call 'short wave' radio, has waves that are extremely long (tens of meters) compared to the longest IR wave (around a millionth of a meter).

Hi Guys and thanks for all the help!

I think I will sign off for now and build something. There are two windows with nearly the same vista that can be used for comparisons. Just the double pained "Andersons" vs the addition of intervening stove glass are my first choises to start. Thanks again-------BillZ

From my experience standard glass does not let much UV through but does let IR pass. Try setting in front of a sunny window. Metalized glass keeps IR out it is used to keep rooms cool.

Mike

"From my experience standard glass does not let much UV through but does let IR pass."

1. Then why is the color faded on the side of my furniture exposed to the window, while the side exposed to the fireplace is not?

2. Then why do we need special glasses to protect us from UV at the beach and ski slopes?

Hi Dk,

I know that when I use UV sensors in my work I have to buy special Quartz fiber optics that will pass the UV spectrum. Standard glass will not work. I have a link to some information http://www.newton.dep.anl.gov/askasci/phy00/phy00890.htm, one thing that Jim Swenson at Argonne says is "ultraviolet is actually the _least_ penetrating wavelength range in the whole electromagnetic spectrum".

Just my observation and I could be wrong again.

Going back to sources "Solar Heating and Cooling, Kreider & Keith" reveals that the great majority of the energy in solar radiation is in the visible range with a little in the near infrared. Very little in the ultraviolet. Silica glass transmitts about 92 percent of the radiation in this visible/near infrared range (minimum of 81% depending on conatminants) but transmitts only about 0.3% in the infrared that would be radiated by a 200 deg. F object. This is the way a greenhouse works. Of course, there is some absorption of heat by the glass leading to loss by conduction and convection. The point is - you want to allow visible/near infrared in and trap the infrared that is emitted by the "warmed" interior of your trap. Glass is generally pretty good at that for a common material.

1) the color has faded because it is photo sensitive not UV sensitive. Standard flat glass will not pass UV light. The light/heat coming from the fire place is primarily IR radiation and very little UV.

You need a more pure glass, such as the quartz or fused synthetic silica that has been mentioned. Even standard fused quartz will pass UV light very well. For specific band widths, you use the Synthetic, as the impurities are measured in the parts per billion.

2) When you are at the beach, the sun is reflected off of the water, and you need polarized lenses, not particularly UV coated. If you have plastic lenses, then perhaps the bands being passed are such that you need the UV coating. Otherwise it is good marketing. When you are in the mountains, there is much less atmosphere for the light to pass. Even the small amounts of UV that are passing through regular glass may become enough to cause harm, and UV coatings add a "feel good" measure of security. again, the reflected light focuses the intensity of the light you see, and polarized lenses would be a good idea.

Hello dkwarner,

Light consists of both electromagnetic rays and photons.

The photons have mass and energy, and do pass through the glass, being only slightly slowed or filtered.

Nobody fully understands exactly what Light really is, although scientists and others do have a few theories, and are still trying to solve the puzzle.

As I "see it", Light is just one of the puzzles we shall never find the full answers to, whilst still on this Earth.

You will note that metal objects are not easily affected by light damaging them.

Radiant energy from a fire, is not as energetic as Sunlight.

So, your "furniture fading" is caused by the energetic impact of those photons striking the furniture, causing the molecular structure of dyes or mainly other organic objects to change.

Please note that some colours are affected more easily, blue dyes and blue paint do not last as well as some other colours.

Likewise the special glasses, designed to remove most of those energetic photons - In snow areas on a fine sunny day, same as if at sea in a small boat, many extra photons are reflected towards any light-absorbent object, including eyes, skin etc.

Be sun smart ......

Hi Sparky!

Thanks for taking the time to answer. I taught physics at both university and high school level for 32 years, before retiring to become an engineer 12 years ago, so I'm fairly well informed on light (Also taught photography for about a third of the teaching time). On the other hand, I have never felt fully comfortable with the particle/wave duality of photons, and am quite open to better understanding...

I was always under the impression that most of the fading was due to the higher end of the spectrum. The easy chairs I am thinking of were wine (bluish red) and have faded to sort of a slightly bluish brick color.

"Nobody fully understands exactly what Light really is, although scientists and others do have a few theories, and are still trying to solve the puzzle." I think that is probably true!

It seems that many dyes and most plastics have relatively weak bonds that are relatively easily broken, while metals and Teflon™ have much stronger bonds. (I have some antenna parts that have been nearly fifty years in the sun with no apparent degradation!

Dick

BillZ

Sorry for the late addition to your thread. What you all are talking about is commercially called low-e glass. It is coated with a very thin layer which is reflective to the longer wave-length infra-red radiated by objects at temperatures lower than about 400 deg-C. The light from the sun has a much higher source temperature so it is in the shorter wave-length visible range, which passes through this coated glass with very little loss. Its one-way mirror effect is because of the difference in where in the spectrum the peaks of radiation are located. Room-sourced thermal energy is reflected back in and sun-sourced energy is passed through.

I believe that every manufacturer of double-glazed windows offers them in a low-e version which is suitable for the local climate. Since this coating is very thin, it is fairly easily damaged. You will not find it on a single-glazed window; it is on an inner face of the glazing on a double-glazed window.

This coated glass is much more efficient in holding heat in a building than standard glass. Wide availability. Very modest cost adder. Use it!

JMM

JMM

Thanks for your answer. If I understood you correctly, my "Anderson" double glazed windows are turned the wrong way around to trap heat inside the house. For my envisioned window heater I would need to open the existing "Anderson" and put a "wrong way coated double glazed" in on the front of my "heat exchanger box". I am assuming that the double glazed Andersons are designed to keep heat out.

Thanks again BillZ

What we need is a window with a coating that can be (electrically or physically) switched for summer or winter use...

Very Good Answer!

Still, it sure would be great if someone could develop a 'thermal diode' that could be switched for summer and winter purposes.

Dick

JMM

Thanks again. You did clarify. One last try. Is there a material that would reflect or not pass IR only. I assume the re-radiation from the black box would be IR. If the the energy in the Sun's spectra is not flat and skewed toward the UV end of the spectra one would gain from that semi-diode effect. Then there is --- Does flat black paint turn all the suns radiant energy into heat?

BillZ

BillZ,

1. I believe the low-e coating is the material you are thinking of. If you contact the Andersen window folks I believe that they can get you a graph or chart with the spectral characteristics of this coating. I know I had one once years ago.

2. Yes, the re-radiation is IR, in fact it is towards the long wavelength end of the IR (the end further from the visible).

3. The Sun's spectrum is very broad, but the greatest amount of its heat energy at the earth's surface is in the visible. The amount of energy carried by each "photon" or unit of sunlight increases in direct proportion to the frequency, so red is less energetic than blue, etc. The ozone in the upper atmosphere absorbs much of the (more energy-containing) UV, which protects us from the harm it otherwise would do to us and most larger life forms. These coatings on the glass are best called a "selective surface", and they act like the "bouncer" at the club--only admitting those deemed to be suitable customers (with the right "clothing" or wavelength). In the opposite direction, they act like a guard who only allows those with the right identification to get out.

4. Not perfectly, but pretty well. For better absorption, you would need the incident light which is not absorbed to reflect onto a second similar surface. A flat surface doesn't do this, but one with tapered pockets or flutes would. Unfortunately, this adds cost and complexity to the collector. You could contact the paint manufacturers for their recommendation of which pigment product and vehicle to use for your solar collector application.

Regards--JMM

JMM

Thanks

BiilZ