New Solar Thermal Concept Panel

[sundug]

sundug: "I have had a PV pumped solar water heater on my roof for over 18 years, it is a closed loop, and uses propylene glycol antifreeze, which can be damaged by high temps. Since the PV powers the circulation pump whenever the sun shines, stagnation of the collector is not a problem. I have never had water temps over 165*F, since I sized the storage to collector area correctly."

The problem I see is that I want to use solar panels to heat my house (santa fe, NM). Thats were I would get a huge benefit. For me, space heating costs in the winter far exceed any other energy costs (other then gas for my car). The temperature fluctuations here are crazy. freezing one morning and 65 in the afternoon. Sizing the system for heating in the winter is a huge mismatch for summer hot water heating.
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Sundug- I suggest that you seperate the domestic water heating from the space heating systems. water heating is a daily need, space heating seasonal. Consider using vertical air collectors for winter space heating, and placing the domestic solar collector at a steep angle to improve winter collection, and lessen the chance of summer overheating. Forget polycarbonate and hot water-it breaks down. Don't worry about propylene glycol's viscosity. I suggest you join us at
http://groups.yahoo.com/group/SimplySolar/ we have been group thinking plastic collectors, and can help you avoid mistakes already made. Doug

[mountain]

I'm thinking that Alex's concept would work very well regardless of the containment, whether glass or polycarbonate.

I'm thinking glass tubes would work great filled with black silicon carbonate.

Glass is easy enough to weld, (I have used oxy-propane torch) & can withstand high temperatures. Availability from laboratory supply is good, pretty affordable.

I am presently building a parabolic trough mirror. A silicon carbonate filled glass-tube at the parabola focus might just work like a hot damn!

[Mike90250]

As long as you are using glass tube, there is the evacuated glass tube, for toasty winter use! With a trough mirror, you'd have to cover them up in the summer, unless you have a hot tub. Use the borosilicate, zero expansion glass though.

[alex]

I'm thinking that Alex's concept would work very well regardless of the containment, whether glass or polycarbonate.

I'm thinking glass tubes would work great filled with black silicon carbonate.

Glass is easy enough to weld, (I have used oxy-propane torch) & can withstand high temperatures. Availability from laboratory supply is good, pretty affordable.

I am presently building a parabolic trough mirror. A silicon carbonate filled glass-tube at the parabola focus might just work like a hot damn!

mountain,

you are certainly right. I was also thinking of somthing like an evaculated tube, where a "straw" chanels the water to the bottom, and the water exits the top. I am really interested in the physics of the design of the absorper. I am new to this, but it would apear that it could allow some re-thinking of solar thermal design.

First, the absorption is happening on the particle surface, which is in the liquid, so the transfer of heat is maximal and not limited by thermal conductivity of the absorption plate.

Second, the particels are dynamic and constantly being pulled back into the channel. A particle that absorbs some energy goes back into the channel, particles in the channel go back to the sun, etc. This must have a positive effect on the absorption rate. I suspect it take time for a particle to 'cool off', so while this is happening another particle is on the surface absorption a photon.

Third, the particle size can be increased to increase the flow-rate of the system, which would ultimatly increase the efficiency of the system. My first panel used larger panels, but the resistance to flow in the panel and my main pressure could not sustain them against gravity. The glass tube idea would increase the channel size, reduce the resistance to flow, and help increase the efficieny even more.

Fourth, the particle material could be optmized for high absorption with low thermal emmitance.

Fifth, since the absorption is happening in the liquid and the liquid is exposed to the light, you could alter the chemistry of the liquid to achieve low thermal emmitance.

[alex]

SunDoug,

Your coroplast heat exchangers seems like a fantastic idea. I have been thinking of the possibility of solar space heaters. Imagine the possibility of using solar thermal panels to channel heat into a tank, which becomes a "sculpture" of sorts in a room and serves as both heat storage and radiator. During the day the tank fills and it radiates it back at night. The whole assembly must be very inexpensive and reliable and straight-forward, something that a person could go down to home depot and pick up and install themselves. Such a device would certainly need an inexpensive heat exchanger as part of the storage tank, and I suppose everything could be made of polypropylene (including the solar panels), which is recyclable and thus sustainable.

I saw your youtube video...have you pursued this idea further? I am new to this topic as I said, but I do see the potential of a solar thermal economy powered with recyclable plastic. Heat exchangers such as yours would seem to play a key part.

[sundug]

I am still developing the coroplast collector, along with others in http://groups.yahoo.com/group/SimplySolar/ group. One guy there has had one on his roof in Texas since April. The main problem is finding a good way to attach the header to the coroplast, using inexpensive, locally available products. I have tried several hot glues and cold adhesives, the trick is to keep only low pressure in the panel. Doug

https://www.builditsolar.com/Projects/SolarHomes/Doug/DougsProjects.htm

http://www.youtube.com/user/sundug69

[boza]

Activated charcoal?

I wonder if granulated activated charcoal would work as the particulate medium in this application. Activated charcoal has very high surface to volume ratio and should be a good light absorber. Here is what Wikipedia says about it:

"Granular activated carbon (GAC): Granular activated carbon has a relatively larger particle size compared to powdered activated carbon and consequently, presents a smaller external surface. ... GAC is designated by sizes such as 8x20, 20x40, or 8x30 for liquid phase applications and 4x6, 4x8 or 4x10 for vapour phase applications. A 20x40 carbon is made of particles that will pass through a U.S. Standard Mesh Size No. 20 sieve (0.84 mm) (generally specified as 85% passing) but be retained on a U.S. Standard Mesh Size No. 40 sieve (0.42 mm) (generally specified as 95% retained). AWWA (1992) B604 uses the 50-mesh sieve (0.297 mm) as the minimum GAC size. The most popular aqueous phase carbons are the 12x40 and 8x30 sizes because they have a good balance of size, surface area, and headloss characteristics."

[sundug]

Polycarbonate and hot water

Polycarbonate and hot water

A description of how hydrolosis affects polycarbonate is here:

http://www.nhml.com/resources/2001/4/1/polycarbonate-high-performance-engineerin\

g-thermoplastic



In the wikipedia article (http://en.wikipedia.org/wiki/Polycarbonate) it says
about water:
"Considered safe ... At room temperature. Above 60

[Mike90250]

re - granulated activated charcoal

I think that would fail after a few months, the abrasion of the grains against each other, screen & tube, will chip and grind the particles, to smaller dust that will pass thru the screen eventually, and the carbon may stick to the sidewalls, defeating the drainback idea. Good thought, but the granulated activated charcoal is likely too soft.

[mountain]

coroplast & UV

I work at a ski-hill... a very sunny place called Panorama, and coroplast has been used for years as a substrate for signs. It is available in a wide range of colours in addition to clear.

In the strong mountain sunlight, intensified by reflection from the snow, the coroplast lasts several years before it begins to look ragged & eventually fall apart. 5 Years max before it's in the garbage bin.

Perhaps it is the colour additives that degrade it's UV resilience. Is clear coroplast really UV stable polycarbonate? Anyone got a spec-sheet to post?

On polycarbonate vs glass
I have 2 direct air solar-thermal panels, one unleaded glass & the other polycarbonate ripple-board (sun-tuf) . The polycarbonate outperforms the glass by 20%, probably due to it's texture, which catches more energy when the sun is at an acute angle to the surface. Time will tell how well it lasts.

[BRYANinNC]

Great idea with the particles

Alex,
I think that's a great idea, using the particles.

Please continue to update us.

Thanks!
--Bryan

[sundug]

Coroplast is not the same as polycarbonate, as it's polypropylene, which can have UV protection added to it. Also, corplast signs are not under a UV stopping glazing as they would be in a solar water heater.

[gortie]

New Solar Thermal Concept Panel

In this process the heat is produced by using coal and then the solar beams are imergged into it for further use.This is is the only way the panels work.hope you are satisfied by this information.

[russ]

In this process the heat is produced by using coal and then the solar beams are imergged into it for further use.This is is the only way the panels work.hope you are satisfied by this information.

Do the big coals mate and make little coals or something? Water is the best heat carrier - the color is not of any importance. Coal has a lot lower heat carrying capacity/transfer than water.

Now if you plan to burn it that is another thing!