Solar Coatings

Are you talking about mirror like reflection or black like absorption?

When your are talking about paints, coating, surface treatments a lot depends on the base material involved. Some will work better than others especially when you are talking about outside exposure. Could you detail more about your objectives?

Niel Leon

uni-tech-serv.com

Bring Your Vision to Reality

The only way in which this can effect is if it is very reflective - aluminium paint is used on boilers because it reflects the heat back in. So take the polish off the outside of any metal used.

The material should be conductive. The surface is heated by the absorption of the infra red rays. This will heat the surface and the heat must now be conducted away by the substrate so insulation properties could have an adverse effect. Heat can be lost by radiation and the higher the temperature the greater the radiation so you need to conduct the heat away by conduction through the substrate to the heat transfer (convection or pumped) medium - which in the case of water heaters is the water itself. Once the medium gets to be equal to the surface temperature the whole issue will become static.

Flat black or flat dark green oil base, preferably high temp., or it will 'chalk' after a few years. There are high tech paints purpose made for solar heating that have a 'spiky' surface when viewed under a microscope. Available from solar suppliers, but I have no idea as to their application methods. I'm going to try stove paint next time.

Thanx for the response.

Indeed I was thinking of black since dark green never crossed my mind, even though it sounds not bad as an alternative.

What is stove paint? Is it another painting method and if it is then how y'do it?

I was thinking that I saw videos where people coating pop cans after they stack them, to heat air, and I failed to see/notice the paint and method they use to do them with. I guess the paint has to be more temp proof as air could heat up well above the water's boiling temp than in hot water panels.

Stove paint is a high temp coating for wood/coal stoves, available at large hardware stores. Engine paint is an alternative from auto parts stores but probably more expensive. For the DIY project, flat dark green was found to have as much heat absorption as black, and may add a little class to the finished project.

How to do it: Make sure the metal is cleaned with detergent and water and a purple Scotchbrite (auto parts store). Brush on (cheapest) and let cure for a few days before installing.

I will definately try it. thnx

Thanx, but Do you think this paint gives good heat conduction at low temperatures also?

And how can you apply fine carbon (poweder) to Al or Cu, what other technique?

I built a really inexpensive solar panel many, many years ago using galvanized steel roofing and copper pipes (soldered to the roofing). I coated everything with stove black, which isn't exactly like paint, but it withstands high temperatures and remains black for a long time, and it's cheap.

NASA and Sandia labs were doing some heavy-duty research then to develop the "best" coating, and Sandia came up with an oxidation process for aluminum(and I don't recall what it was) to minimize the black-body radiation while maximizing the solar radiation absorption. I recall that the oxide layer thickness that had the best effect was 4 microns thick, and it cost an arm and a leg to produce it.

I figured, "What the heck? If the goal is to reduce water heating costs, isn't it a little ridiculous to spend more than can ever be paid back by the savings?"

Therefore, I spent as little as possible, and I found that my 'cheap' unit performed about as well as their incredibly expensive one.

Good on ya, Bill.

Just what is stove-black though? Can you enlighten me a little on that?

Lehman's Best is one, and Imperial is another.

Today it's generally made of a mixture of charcoal and carbon, but years ago, it was made with lead and charcoal and/or carbon and/or pulverized coal.

So, what is the best way to apply it on? Can you simply paint it?

Bear in mind I am talking about a Flintstones era (primitive) facility (no modern method) to do it with. Something that would add a Greene kind of effort to it.

It's a little like paste in some forms, and in that case, I suppose you spread it on like paste wax, but all that I have ever used was liquid, and you just paint it on.

Its a can of spray paint that is flat or gloss black. You can buy it about anywhere. We here in the midwest use it for repainting are BBQ grills.

Bill:

The coating you are talking about for aluminum is a special form of anodizing. It works very well on raw aluminum surfaces. When you have other materials (including painted aluminum as with soda can) you need to use other coating or surface treatment techniques.

Yes, you can simply paint the surfaces with stove black, but as you noted doing it right and getting a good bond between the native surface and your surface treatment will most like be beneficial in the long run.

Niel Leon - UTS

Did anyone try to powder coat,It must be good for high tempture because after your done powder coating the object you bake the part in an oven.Just an idea.Im still looking for solar cells for a $1.00 dollar a watt.

cheap and easy. You can buy bags of lamp black - or soot, or you can get plain old graphite in flake; mix with boiled linseed oil, and paint on. Can use shellac as the carrier and binder, as the shellac can be thinned down to allow a fast drying THIN film of residual binder to form - holding a very thin film of carbon or graphite to the surface. Could be made opaque, by using successfully applying additional coatings, using a french polishing technique. Thinness of the film is the key to transferring the heat into the object that it is coating. Carbon is fade proof, shellac in the dry should last a very long time, and so should linseed oil. Most house paints last a long time. My preference is for the shellac and carbon or graphite, on account of the thinness of the film, the speed of drying and the ease of removal with alcohol.

Solar selective coatings range from simple to very complex. The basics of a coating are high absorbtivity, low emissivity. ie. takes in max energy, radiates or emits minimum energy. An excellent product for this purpose is Solkote. Can Google for links.

straight forward - the best would be a flat black but flat paints could have less durability tan the enamel (gloss) types to get the best of both worlds use a gloss black and then take off the gloss with an abrasive - wire wool should be good.

Flat paints are often flattened by the use of high quantities of fillers and this can reduce its durability. (NOTE - "can" not "will). They can also retain dirt more easily.

The flattened surface will reduce reflectance.

If the substrate is a highly polished metal it will also reflect heat whether painted or not so abrade any shine from this also - it will also help adhesion.

There is a photovoltaic coating. It must be applied to a galvanized or metal roof. Wires are then connected to the roof and fed into your newly purchased energy management system along with batteries for storage. Incredibly enough, folks have been able to install these roofs in deed restricted communities as it falls under some federal law. Very cool to turn your roof into one big solar panel. It may not be pretty, but you will only notice it for about a week. You will notice the drop in your electric bill all year! And yes, it still works on cloudy days.

I will get the specifics from my colleague and post soon.

With all the systems mentioned previously, surface preparation is still of paramount importance. If the surface is not pristine, nothing will bond in direct UV exposure, not to mention extreme weather conditions. Coatings manufacturers are very helpful with detailed installation instructions and will provide field help from technical staff in this economy from their distribution.

Off Topic.

I suggest you read the original entry.

fair enough, scrap the first half. The second half on surface prep is worthwhile and I will bring back the resource from several specialty Coatings manufacturers which will last. Sorry. Got caught up before my morning coffee. Several US Companies do manufacture paints specifically designed for retrofit of solar panels. Since I stepped on my foot by typing before grasping, I will make the extra special effort to contribute and make amends. It was clearly off topic!

When I read the first post I thought the matter was about photovoltaic cells; I'm actually more interested in your answer than in the whole thread (no offense), a solar panel will give you hot water, that's great but not all in a house is about hot water, you might want to watch TV or run your air coller on "free" green electricity; just think about all those electric gadgets we keep at home.

When you contribute with a "correct and on-topic" comment, please include the wrong one for me.

Thanks

GA. I subconsciously recommend the use of purple Scotchbrite not only for 'tooth' for the paint, but to reduce reflection in the substrate in my post above. Better might be 120 grit wetordry sand paper, but this proved too laborious for for the area I needed to cover. I have a hot air (ie. 150 deg F @ 20f deg ambient) system so absorption through the substrate is a non issue. I did build a system with dual flow over and under, but with no appreciable gain. More important is the handling system sized for optimum transfer to the storage medium, and a good temperature differential switch between the collector and the storage.

BTW, dark green works as well as black for DIY. 'Hunter' green and black mixed 1:1 should do it. Or dark camouflage, but check the temp resistance.

What you are looking for whether trying to keep heat in a solar heating fixture, or insulating cool spaces from high heat, the only patented coatings that are proven to actual reduce thermal (radiative) heat in a multi layer mil thickness coatind our patented custom spec coating system we call Nansulation.

I have been working in the coatings of advanced aerogels for over 14 years, and i am a stockholder and exclusive distributor and certified applicator of two industrial grade coatings called Nansulation and ASTEC ceramic coatings.

We have combined the two different non toxic, water based coatings into a complete system that addresses radiative thermal energy transfer (heat).

We have light transparent coatings for use in solar projects, Nansulate Solar, also mixes for high temp up to 370F for covering pipes, metal tanks, boilers, plastic, LDX for lead encapsulation.

It so effective, so easy to apply and as consumption increases, raw costs will go down, and I predict that in ten years it will be a required coating on all new homes to be applied at the same time as when the primer and top coats are applied.

Its root material is NMhydroxy, which is Aerogels in a paint form.

For more information, the expected slurry, or "really ?!," questions and to download a study I have put together, regarding these materials please write me.

We have a prmotion going on right now with free shipping direct from the plant in florida. Both ASTEC and Nansulate ship directly from FLorida. I am a certified Warranty and Factory specialist, Installer and SPecifications Writer for many municipalities, for both ASTEC and Nansulate, my contracting company specializes in these coatings systems almost exclusively and we service, MD, DE, VA, NC, but we have an extensive network of certified applicators of ASTEC.

I cannot sell you ASTEC, because you must become a certified installer. Once you become a certified installer, then you may purchase materials direct from ICC.

I can sell you Nansulate, that is available to anyone.

As a manufacturer approved spec writer I can write you a custom Spec, but i need to know all the details of your project, with preferably pictures, if your in the mid atlantic states, I can travel to your site, We are Class A certified Industrial and Commerical Contractors with 1m general liability and worker comp, with over 4 generations of hands on construction expereince.

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www.warwickbuilders.com