Salt, science and energy.
#41
All that moving around of components is the part that double parabola design supposedly might avoid. I know this movement can be automated, but anything automated tends to fail eventually, too.

Ditto for those vacuum tubes he's using. I know those are most efficient, and I found a wholesale source for them, but they're so fragile they won't ship them unless you buy 100 at a time (and, can you imagine shipping such a product to others???). Also, the vacuum they're under (what makes them work) makes some people say will make them fail at some point (as, the vacuum fails). This guy hasn't protected those tubes with anything against branches falling or ice, etc. (or, neighborhood kids). So, it's advised by at least some to cover the entire assembly with glass or polycarbonate of some kind (I think that's the right word). I've wondered if it would make a longer-lasting system (and cheaper too) to dispense with those vacuum tubes and just use pipes of some conductive metal (like, copper or aluminum) and cover the whole thing in a box so it's insulated and has glass or the polycarbonate on top. (Glass being more clear and longer lasting, polycarbonate being more impact resistant).
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#42
(12-31-2011, 08:24 PM)tvguy Wrote: People have been using fixed solar collectors for years to heat their water that are mounted on a roof top that don't track anything.
They work fine although I'm sure they would work better if you went to all the trouble to make them track the sun.
I have some and although I haven't used them yet I was shocked at how hot the copper plates and pipes were on a cloudy day.
Basically I don't see that's it's worth all the effort to make something that needs to rotate two different ways.

What these designs have in common makes them called "concentrating collectors", versus the flat plate panels you bought. The concentrating collectors do require aiming at the sun, at least the designs that aren't something like the one I showed earlier. That's what made it different than most.

You could turn your flat plate collectors into some kind of hybrid concentrator if you could extend mirrored flaps out from the edges to capture more sunlight and direct it into the middle.
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#43
(12-31-2011, 08:36 PM)PonderThis Wrote:
(12-31-2011, 08:24 PM)tvguy Wrote: People have been using fixed solar collectors for years to heat their water that are mounted on a roof top that don't track anything.
They work fine although I'm sure they would work better if you went to all the trouble to make them track the sun.
I have some and although I haven't used them yet I was shocked at how hot the copper plates and pipes were on a cloudy day.
Basically I don't see that's it's worth all the effort to make something that needs to rotate two different ways.

What these designs have in common makes them called "concentrating collectors", versus the flat plate panels you bought. The concentrating collectors do require aiming at the sun, at least the designs that aren't something like the one I showed earlier. That's what made it different than most.

You could turn your flat plate collectors into some kind of hybrid concentrator if you could extend mirrored flaps out from the edges to capture more sunlight and direct it into the middle.

True I don't know if it's necessary


My point was, it it worth all the effort? I think some of these people are anal about the whole thing. Just like your comment about vacuum tubes versus a freaking metal pipe.
I'm more of a get er done and get er done cheap. I'm not going to spend a bunch of time, money and energy making something that is only a little bit more efficient.

KISS .. keep it simple stupidBig Grin To me the more innovative and simple the better.
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#44
I happen to have a graph showing the differences in efficiency of vacuum tubes versus metal pipes. Where the pipes do substantially worse is when the wind is blowing or the outside temperature is very cold.

The advantage of concentrating collectors, of course, is they attain higher temperatures than other types, with fewer materials.
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#45
I agree that moving parts should be avoided if you can, but tracking can max collection surface area.
I think I would rather have a larger area to cover for a cheaper more durable collection tube, than the high efficient vacuum tubes.


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#46
So Ponder, you don't happen to have those math formulas for the double parabola.
Actually, what I need to know is, what angle does the axis of the two parabolas make.
Is it 23.5 degrees to match the tilt of the earth?
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#47
Oh you are a technical one. I thought I put a plea out on the forum when I was wrestling with this one, where were you then? OK, I'll look for it, I know I have it in my emails if not on my desktop. I save everything to the desktop, it's a mess. Smiling Might take me a day to get you this.

There's some online calculators for calculating parabola shapes too, and some have suggested they could be used if you calculated these like single parabolas, then stitched them together. I wondered how to figure that angle too.

I'd help fund this project or possibly even underwrite it if you wanted to do the labor on it.
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#48
(12-31-2011, 09:43 PM)PonderThis Wrote: Oh you are a technical one. I thought I put a plea out on the forum when I was wrestling with this one, where were you then? OK, I'll look for it, I know I have it in my emails if not on my desktop. I save everything to the desktop, it's a mess. Smiling Might take me a day to get you this.

There's some online calculators for calculating parabola shapes too, and some have suggested they could be used if you calculated these like single parabolas, then stitched them together. I wondered how to figure that angle too.

I'd help fund this project or possibly even underwrite it if you wanted to do the labor on it.

I do some research on the shape. Then we'll print a cross section on a printer(several sheets of letter size).
Maybe we can use one of those new 3-D printers and just print one out.
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#49
OK, I found the files, that wasn't as tough as I expected. They're .pdf files, and I don't find them online, so you're going to have to send me a pm with your email address to get them (or, anyone else that's interested).
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#50
An alternative is heating with DU, it's only 60% as radioactive as natural Uranium. That should still warm stuff up.
I was thinking it could be mixed with phosphors to make stuff glow in the dark.

Best of all, the US government finds it's safe enough to use as ammo spraying dust up in the air. So how bad could it be?
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#51
I think I'd like to see a second opinion on that. Smiling
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#52
Quote:There's some online calculators for calculating parabola shapes too, and some have suggested they could be used if you calculated these like single parabolas, then stitched them together. I wondered how to figure that angle too.

This is a PDF also that should give all the info on the shape of a parabola.



https://docs.google.com/viewer?a=v&q=cac...8uPA&pli=1
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#53
OK
I got a chance to look at one of the PDF Ponder sent. It shows four types of concentrators and gives the design for a "V" plate collector. The water pipe has fins to increase collection area. This helps in increasing verticle acceptance angle. The sun path being plus or minus 23.5 degrees from June to December requires 47 degrees of acceptance. It appears that they use top half to focus ligth in the winter and the bottom half to focus in summer. Again I say that I would favor increasing size over making more expensive with tracking and special pipes.
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#54
[Image: ancient-greek-women-5.jpg]

That's all greek to me. Smiling

OK, are you sure you have adequately checked out this patent (which, the patent holder has graciously placed into public domain):

[Image: how3.jpg]

The fins idea sounds more difficult to fabricate to me, wouldn't a bigger tube be easier?

One problem I have read with large concentrators is if the reflector portion isn't made sturdy enough, slight movement moves the focal point away from the collection surface.

My own suggestion would be to start with a one meter width, and a two meter length, but that's only my suggestion (taken because, off the top of my head now each meter of collection area in direct summer is said to have about 1100 watts worth of energy, and figuring 50%+ losses, I figure a 2 meter collection area might give you 1000 watts net in direct summertime, and substantially less in winter, making that about the minimum size to be worth playing with.)
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#55
Here's your boy...

[Image: Merced.jpg]





http://www.solarnovus.com/index.php?opti...Itemid=247
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#56
All kinds of good info here...


http://www.fossilfreedom.com/increase-output.html
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#57
I am seeing the pipe is about 1/6 the size of the collecton area. Larger pipe means larger volume of water , which requres more energy to heat
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#58
OK, Did some more thinking on the tilt of the earth thing. If we point a box at the sun in spring or fall equinox, then the sun moves up and down 23.5 degrees. This reduces the collection surface to the cosine of the angle, or 91.7%. So we loose 8.3% of are light spring to summer, for any design that doesn't tilt towards the solar plane.
[Image: solar1.jpg]


This also means that the effect of the angle of the sun morning, noon and night will be seen in our trench design. The cross sectional area of the sun absorbed will follow the rule of the cosine of the sun's angle, times the area of the concentrator/collector.

So the trench will give good mid day performance , with no need for east west tracking.
Double parabola gives consistent collection over the seasons, no need for up down tracking.
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#59
(01-01-2012, 11:19 AM)tvguy Wrote: All kinds of good info here...
http://www.fossilfreedom.com/increase-output.html

Yes, this is the site that clued me in to this idea as well. That's also where many of my drawings earlier in this thread came from.
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#60
(01-01-2012, 10:41 PM)chuck white Wrote: OK, Did some more thinking on the tilt of the earth thing. If we point a box at the sun in spring or fall equinox, then the sun moves up and down 23.5 degrees. This reduces the collection surface to the cosine of the angle, or 91.7%. So we loose 8.3% of are light spring to summer, for any design that doesn't tilt towards the solar plane.
[Image: solar1.jpg]


This also means that the effect of the angle of the sun morning, noon and night will be seen in our trench design. The cross sectional area of the sun absorbed will follow the rule of the cosine of the sun's angle, times the area of the concentrator/collector.

So the trench will give good mid day performance , with no need for east west tracking.
Double parabola gives consistent collection over the seasons, no need for up down tracking.

I'm sorry, I can't remember now what you're referring to as "trench". Do you mean trough?

Yes, some designs do adjust for the difference in sun position between seasons. I think they're often pointed for optimum during winter, when the sun is needed most, in favor of summertime angles when you might not need the heat (or power, etc.) as much. But those are minor design issues I think.

I'm thrilled to hear you've got your fertile mind working on this. Smiling
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