Solar-Heated Workshop (more)

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Epictitus wrote:
| How effective is the type 3 panel at trapping air flow? Have you | done any airflow measurements?
It's /really/ good.
When a lit cigarette was held close enough to scorch the bottom lip of an intake vent (about half an hour past sunset), there was no visible effect on the (straight up) smoke plume.
The test was repeated at the discharge vent with identical results.
I think this test was a finer/fussier measurement than the (zero) reading givin by my HVAC flowmeter.
The other measurements of interest are full-sun noontime flows of (installed) panels at both solstices.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/interest.html
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I stopped smoking on Nov 16, 1976, so your technique is not practical for me. Also, I need to make sure the fume hoods in our lab do function before I start working with stinky and flammable solvents (ammonia, methanol, etc). The best "instrument" to ascertain air flow is a 1/2 inch wide by 4-6 inch long strip of single-ply tissue. For permanent (sort of) placement, attach to the top lip of the hood opening. While not necessarily elegant, it is very easy to see whether the hoods work. If they don't, we call Engineering to change the belt on the rooftop fan.
--
Best regards
Han
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Han wrote:
| I stopped smoking on Nov 16, 1976, so your technique is not | practical for me. Also, I need to make sure the fume hoods in our | lab do function before I start working with stinky and flammable | solvents (ammonia, methanol, etc). The best "instrument" to | ascertain air flow is a 1/2 inch wide by 4-6 inch long strip of | single-ply tissue. For permanent (sort of) placement, attach to | the top lip of the hood opening. | While not necessarily elegant, it is very easy to see whether the | hoods work. If they don't, we call Engineering to change the belt | on the rooftop fan.
Sound like a workable strategy to me. It's also possible to buy a smoke bottle for checking very small air flows (I've never used one, but saw it used in an episode of This Old House).
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/interest.html
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You mean one of those....what do the kids call them nowadays..a bong?
r--->kids a lot
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Don't know about nowadays, but 30 years ago that's what we called 'em ;-)
Dave Hall
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Hiya Morris!
Ohhh...if I had a work-space like that! I did, but retired...but,..yeah...the non-competition agreement ran out..and now I have hired 2 people, one from my previous company. My conscience is clear on this as the new owners haven't done a thing to keep the solid surface profit centre going in their business model. So I have started the ball rolling on expansion. I have the opportunity to move into two portable class-rooms, which I can put on the property in any orientation I like. The building code enforcers won't let me join the two portables together, they must remain 'portable'. So, one will be The Dirty Room and spray centre as I will again start on custom laminate tops as well as solid surface. NO post-formed installations!!!!
Now, one concern I have, is dust. I think the passive aspect of your product is the cat's meow (pyjamas), but would it be possible to gently force-feed the panels with, say, some muffin fans, and then push the air through some filtration? Or do you think that there's enough convection to pull through some basic filtration? In my line of work, dust is a bitch. The stuff is like talcum powder in consistency, but heavier so it does fall down to floor level pretty quickly. What if one made a box to hold a furnace filter, and then reduced to the inlet of your panel? Kinda like a funnel shape?
I'm sure all that has crossed your mind already...would you like to share?
r
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Robatoy wrote:
| Now, one concern I have, is dust. I think the passive aspect of your | product is the cat's meow (pyjamas), but would it be possible to | gently force-feed the panels with, say, some muffin fans, and then | push the air through some filtration? Or do you think that there's | enough convection to pull through some basic filtration?
Those panels were the first of a new design, and the convective air flow wasn't particularly "gentle" - we (the customer, the construction crew, and I) were all surprised. In full sun a couple of weeks past the vernal equinox it was more like what you might expect from a furnace blower.
The speed at which the panels move air is dependent on the differential between the temperature of the intake air and the temperature of the air passing through the heat exchanger. Raising the temperature of the air is less of a design challenge than producing designing an absorber/heat exchanger that maximizes the convective flow.
| In my line of work, dust is a bitch. The stuff is like talcum powder | in consistency, but heavier so it does fall down to floor level | pretty quickly. | What if one made a box to hold a furnace filter, and then reduced to | the inlet of your panel? Kinda like a funnel shape? | | I'm sure all that has crossed your mind already...would you like to | share?
Of course! (Not /everything/, but enough to provide some "handles" for grasping the essentials. <g>)
The short answer is that it works best to control dust right at the point of creation. There just isn't any other effective solution - because once it's loose, you're "herding cats".
Next best is to provide a totally closed path for collector air (no flow of room air through the panel). This would keep the collector clean in the dirtiest of environments and would be "spendy", but could still be done with a passive system. If we end up with "Carbon Taxes", this might begin to look like a more affordable zero-carbon solution for messy operations.
What can't be seen in the photos is that the absorber/heat exchanger are highly reflective - with smooth, shiny surfaces. The front of the box itself is painted flat black, but that's only to satisfy expectations of what everyone "knows" a solar collector should _look_ like. But "look" has only to do with the human eye and the limited range of _visible_ frequencies.
I'm much greedier than to settle for that limited range. The challenge here is to effectively trap as wide a range of radiation frequencies as I can - all the way from RF through IR - most of which isn't visible to the human eye - and use it to heat air.
The physics says that I could use mirror-bright absorber elements and the panel would still appear black - and I'd get a bit more heat. I'm positively itching to build that experimental panel!
Anyway (back to the subject) the biggest problem with dust isn't that it's the wrong color, and it isn't even that it interferes with absorbtion (although it does that to a minor degree) - it's that the dust interferes with the airflow and heat exchange process.
Probably more than you wanted to know...
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/interest.html
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Never!. <G>
In the new place, I will be paying a LOT of attention to dust control. Possibly a separate room for sanding and cutting with a furnace-blower- based recirc system. I'm not even sure what I can accomplish with heating. The portables come with electric baseboard heaters. I can't see that as a solution.
I visited a home-show over the weekend and spent a bit of time talking to a guy who sells PV cells. After drawing him a rough lay-out of my house, he said: $ 31,000.00 installed. *Gasp* (I would be replacing the batteries before payback x 2) I guess we have a long way to go.
As always, I appreciate your input.
r
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Robatoy wrote:
| What if one made a box to hold a furnace filter, and then reduced to | the inlet of your panel? Kinda like a funnel shape?
Here's another aproach: use a "Type 1" collector with a removable back panel (follow the link in my sig to an explanation of what I mean by a "Type 1" collector) and just let the darned thing get dusty. Whenever you notice that the collector isn't performing as well it should, just remove the back panel, vacuum out the dust, and re-attach the panel.
-- Morris Dovey DeSoto Solar DeSoto, Iowa USA http://www.iedu.com/DeSoto/SC_Types.html
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