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greybeard
01-18-2008, 11:25 AM
Has anyone yet made a start at trying their hand at a "TAG" ?
I'd been refreshing my interest in Stirlings as a preparation for this summer's project(assuming the cnc is ready to cut parts for the solar dish :)) when I noticed a lot of the university and patent links of the last few years keep referring to thermoacoustics.
I'd had a discussion about 18 months ago on this topic with Evodyne, and decided to re-read what he'd sent me.
The latest work I've come across looks very promising, and with only one moving part - the vibrating magnet assembly for the generator - is enticing to consider.

Has anyone else any ideas/thoughts on this development ?
Regards all,
John

delt0r
01-18-2008, 01:11 PM
There was a big boost in interest with the gas industry in the US. The idea was that they could use them at the pumping stations and have no moving parts. Efficiency is however very low in every paper on the topic i have read. I am about 6 or so months out of the loop tho.

My original interest was the other way round. Pulse tube cryo coolers. Very cool. ;)

If you get stuck getting hold of a paper, sing out. I still have all the PDF's somewhere in my backups.

greybeard
01-18-2008, 01:36 PM
...................If you get stuck getting hold of a paper, sing out. I still have all the PDF's somewhere in my backups.

Thanks, deltOr, that's a kind offer that I'll bear in mind.
Regards
John

greybeard
01-19-2008, 04:52 AM
For anyone not familiar with the technology, a good starting point might be the link below. It's very easy reading. :)
After that, googling "thermoacoustic generators" produces a lot of information.

John

http://www.americanscientist.org/template/AssetDetail/assetid/21006/page/3?&print=yes

greybeard
01-19-2008, 06:02 AM
DeltOr - have you ever come across any reference to the use of a fluid filled TAG ?

I wondered if such a device would be possible, or have any advantages over the gas filled devices vis-a-vis the increase in heat capacity.
Just a thought.

By the way, re your pdfs of papers, do you have a list, or could you send me a screen shot of the list ?

Regards
John

delt0r
01-19-2008, 07:17 AM
Fluid filled? No, you won't get adiabatic compression that matters, hence little or no work done. Unless the is a fluid and a gas, but then the fluid would not provide better thermal contact than any other solid.

So the real answer is that no i did not see any with fluid in them.

As for the PDFs. Well as a physics guy I read a LOT of papers on a lot of topics. Now as someone working in Bioinformatics I have a lot of papers on that two. I have about 10+gig of pdf's. The problem is i did not organize them properly. I even wrote a tool to try and search them. But finding things is slow.

However i will have a bit of a search over the next few days.

delt0r
01-19-2008, 08:01 AM
I could only find a few old pulse tube cryocooler papers. Most must be back at work in my archive. That will take some time. But i did google a little just to see how far out of the loop i was.

I found this: http://www.nature.com/nature/journal/v399/n6734/full/399335a0.html

I have downloaded it so could email to you (Private msg me?). They boast 30% effenciy. Pretty high.

Oh and the coolers that I was interested in became popular because they can be used to liquefy natural gas.

delt0r
01-19-2008, 08:05 AM
One of my posts has gone missing.... I will repeat a little of what i said.

First was that liquid does not work because you don't get the adiabatic heating. Or expansion on heating.

2nd. All my pdfs are very disorganized. I will see what i can do before i head of to nz in a week.

greybeard
01-19-2008, 09:17 AM
Had a quick look at the Nature article. The authors have done a lot of work since, some published in patent applications etc.
A recent patented work I've found,(different authors), is US pat. no. 2006/0119224 where they talk of a Carnot efficiency of 49% !

Thanks for the heads up on liquids - it was an idle musing on my part, but who knows.
I do have a reputation for crazy ideas I have to protect.

pm coming.
Regards
John

edit I think that figure is 49% of theoretical maximum at the given temperature differential, not overall efficiency of conversion!

greybeard
02-10-2008, 02:55 PM
Update on my original question.

Given that there is a lot of information on a variety of methods to get from solar radiation to power, be it electricity or motive power, my first direction is to build a solar collector, most likely a dish, given my location and space available.
With that set up at the bottom of the plot, I can then try a variety of methods and compare results.
Having said that, it is immediately obvious that two identical mirrors would make the comparisons a lot easier, so thats what it will be.
Prototype collector is to be a 3' x 2' x 1/16" ply sheet cut and formed to an approximate parabola with an aluminium foil surface. This will be to check my construction method/maths etc, then two mirrors using 8x4 sheets should follow in short order.

Then the fun will really start, so the cnc construction had better make some progress as well.

epineh
02-10-2008, 06:17 PM
Interesting concept John, I will be interested in how this goes. I don't really understand the concept (yet) but it sounds like a challenge, I have always thought it would be nice to harness some of the noise around this place, with 3 kids and a Pug dog we have a plentiful supply :D

Russell.

Ferny
02-10-2008, 08:29 PM
Delt0r, You made me laugh! Thanks!
I once worked for a physicist who was very unorganized to say the least.
Every prototype device looked like an explosion of clip leads, the lab cabinets overflowed with equipment, his office had stacks of papers strewn about with tall piles leaning... ready to fall over. Perhaps you can can relate?

Now that I think of it out of the half dozen I have known, all but one is organized!
It's OK, with all that heavy duty thinking going on!

I sure do like working with physics guy's since I am continually learn new things.

Thanks for the visual,

Ferny.

greybeard
02-13-2008, 11:41 AM
Halfway through the construction of the prototype mirror(applying the aluminium foil) I'm underwhelmed by the surface I'm producing.
I've made the 'petal' type ply base, with 32 sections, and cutting into the central area was a pain. The template leaves a fairly large flat area(16 cms diameter) in the centre if one is to avoid the likely possibility of a petal snapping off during the sawing.
This was then stapled up before the joins were glued together.
First lesson was that a ply sheet bends easier one way than the other, so the whole thing has a tendency to become a trough.
Second lesson was that cutting out foil is most easily done with scissors. The sharpest scalpel rips the foil, instead of slicing through it.
Spraying a mount adhesive was straight forward, as was laying it down and burnishing the surface with a small pad of cloth.
As this was a prototype I'd left in the staples and made no attempt to improve the ply surface. Burnishing the aluminium showed up all the imperfections, even the grain, though it is a very fine surface ply I'm using.

So, what next? At the moment we have thick fog so I'm not in a position to play around, setting fire to bits of paper, but it does give me the opportunity to pose the following questions.

How 'good' a curved surface is actually needed ?
What I have in mind is that if the solar energy hitting an 8' diameter parabolic surface is reflected back to hit a target 6" in diameter(the hot plate of my stirling engine), does it matter if the image is greatly distorted ?
Suppose a second 8' mirror was made up of 2" square flat tiles. Each one would produce a 2" (roughly) square patch of light on the target, so the total light hitting the mirror would still be all hitting the 6" target after reflection.

Is there any difference in the amount of energy received that I have overlooked ?

The aluminium foil, as noted above, shows up all the blemishes, so now I'm considering using a plastic sheet instead of ply. If I managed to keep it dust free(no small task) it should produce a major reduction in light loss through 'scattering' from the surface. I'll keep to the foil as a reflector, as plastic sheeting and kitchen foil are readily available to most people, whereas aluminized plastic isn't, never mind the cost.

delt0r
02-18-2008, 12:02 PM
Been in NZ for 3 weeks and had generally limited internet.

Anyway, How good a curved surface do you need.

It depends. Its not high quality optics level, but if you need a high concentration ratio they need to be pretty good. Also there is usually a non-imaging optics 2nd stage focuser.

non imaging optics are very cool. again if after a Google your interested i have some papers on them.

But for low level focusing the only problem with a poor reflector is uneven heating of the surface. this is not really a problem for low temperature absorbers (ie copper <1000 C).

I have used a hand made Al foil and got to 250 C will a little insulation on the absorber. It was pretty bad so doing better should be easy.

greybeard
02-18-2008, 04:47 PM
non imaging optics are very cool. again if after a Google your interested i have some papers on them.


delt0r - thanks for the heads up on non imaging optics.
Did as you suggested, an googled the subject, and read a couple of papers.
Interesting to discover there's a name for what I had in mind :)

I'd be glad to read anything you have on the subject. It may be a bit of a side issue, but I'm a great believer in acquiring as much knowledge as I can - you never know where it may lead, and doesn't take up much room.
Regards
John

delt0r
02-18-2008, 07:14 PM
There was a good article back in 1991 in Scientific America (march). There digital archive does not go back that far however.

I can't find any good links now, but generally the curves are pretty complicated and are not easy to make without CNC. I have just found a good way to full text index my PDFs (swish-e) but I can't find my really old PDF archive. I will have a look at work tomorrow.

cozmicray
03-08-2008, 12:29 PM
Lamina Flow Engine

http://www.stirlingengines.org.uk/thermo/lamina.html

http://www.youtube.com/watch?v=cjjkj-UGboM

The basic parameters of the engine are

1. Bore - 20mm
2. Stroke - 18mm
3. Hot cylinder - 14mm ID X 140mm test tube
4. Flywheel - 75mm diameter 3 spoke
5. Con Rod - 75mm long with ball bearing big end.

OneAndy
03-08-2009, 04:25 AM
I realize this is grave digging... but any progress?

I'd love to start building my knowledge and skill-base in this area so I can eventually try to build a usable Stirling engine genset.

greybeard
03-08-2009, 08:42 AM
I realize this is grave digging... but any progress?
.......

Bit too close for comfort Andy, but thanks for posting, as it's got another part of the brain working again.


.....I'd love to start building my knowledge and skill-base in this area so I can eventually try to build a usable Stirling engine genset.

I've got as far as re-building my first cnc, which is meant to be the workhorse and first step to the ultimate goal of generating our own power.
My plan has been(is) cnc/solar mirror/hot water/hotter working fluid(oil?)/generator.
So you can see I've a long way to go, never mind the domestic life that slows us all down.

But now the sun has started to shine again in this neck of the woods, I feel encouraged to change up a gear.
Any information you can bring in, Andy, would be most welcome, and help to keep my brain going :D
Regards
John

epineh
03-08-2009, 09:00 AM
While that brain is going again John :) ... what sort of temp diff would be needed to make any sort of usable power using a stirling generator ?

We have so much sunlight here it seems a crime to be using coal fired power stations (during daytime hours anyway) Our plumbing is run through the roof space and on a hot day when the cold tap is run the water that has been in the pipes in the ceiling is hot enough to scald you if you put your hand under it, until the cold stuff kicks in. For me a dish that could go above 100deg c would be enough to generate steam which is easily converted into electricity using good old fasioned technology, the used steam/water could be kept in the roof space at a nice warm 70ish degrees. I know that last 50 or so degrees takes a lot of effort but it seems worth a shot.

Surely a simple mirror array like those solar furnaces but on a small scale is not that hard, and I am sure a few steppers/servo's could be used (this is CNCZone after all :D ) to keep alignment of the mirrors while the sun moves about.

Just adding another project to the list (chair)

Russell.

greybeard
03-08-2009, 10:25 AM
Hi Russell.
I suppose there's no simple answer - the stirling's great attribute is that it can work with very small differential temperatures. However, like all energy conversion processes, the greater the temperature difference, the greater the efficiency of the conversion.
This in turn raises problems with avoiding heat losses/choice of materials/capital costs of the system.
Many years ago, a friend had the idea that with a low temperature difference, the way to go was to use huge lightweight pistons, 6 foot diameter polystyrene foam. We never got to the fine details of his ideas, which might have been just as well, and instead, concentrated on finishing the bottle.

With your situation in Oz, perhaps using the solar energy to purify waste water might be more useful.
Another fundamental problem, of course, is how to match the timing of the solar energy input to your energy needs. Storage of the energy will kill most schemes from an economic point of view, I think, so if you can identify an electrical energy need that matches daylight hours, then a sterling/generator should be a good way to go.

My most recent thought on this topic in general was to modify my mirror design to make use of a local sheetmetal company with a seriously big laser cutting facility.
I'm thinking of laser cut stainless sheet, with suitable notches/tabs, that will assemble without fastenings to form a reasonable parabolic surface.
The reason I'm not considering a simple "trough" shape, is that I want a high temperature area to become the hot end of my stirling. The trough is perfect for producing hot water in a very cheap fashion, but there's a limit to how many hot baths I can take :D

Regards
John

skippy
03-08-2009, 11:04 AM
Hi John, I was in contact with Lance (Evodyne) for quite a while some years back but we lost contact and I don't think he checks in here any longer. You wouldn't happen to have an email address for him would you?
regards
Phil

CJL5585
03-08-2009, 11:50 AM
John,
A couple of years ago I downloaded from a thread on this site (I think), a program for parabolic dish and trough reflector design. I have since that time lost a hard disk or two, along with the program.

Do you have, or know of a link, where I can get such a program? I have done a couple of searches without results.

Also, any luck on the CNC?

Jerry

OneAndy
03-09-2009, 02:08 AM
Bit too close for comfort Andy, but thanks for posting, as it's got another part of the brain working again.



I've got as far as re-building my first cnc, which is meant to be the workhorse and first step to the ultimate goal of generating our own power.
My plan has been(is) cnc/solar mirror/hot water/hotter working fluid(oil?)/generator.
So you can see I've a long way to go, never mind the domestic life that slows us all down.

But now the sun has started to shine again in this neck of the woods, I feel encouraged to change up a gear.
Any information you can bring in, Andy, would be most welcome, and help to keep my brain going :D
Regards
John

Thanks. My plan is similar, tho I'm skipping some steps and going a slightly different route.

CNC (nearly done). It's a moving gantry style for hardwood cutting to ramp up my main money making business with gun grips, stocks, signs, engraving, etc...

Even though it's primarily for wood, I've taken great pains to make it very stable against load in alignment of leadscrews to bearings and nuts, spindle to table, and flex in parts. This baby ain't going nowhere.

And I beefed up my travel. 50x36. Yep, I'm going to get into METAL CASTING using the lost foam process! I figure any adventure in making engines from scratch will be greatly aided by the ability to cast somewhat precision parts. Precision cut-foam for investment casting seemed alot easier and precise for metal work than the traditional green sand casting method.

So while waiting for my flanged bearing upgrades for the CNC to come in from MSC, I went ahead and poured a heavy(ish) duty foundry in an old air bottle I had a welding buddy of mine cut the top off of. Inswool and 2.5 inches of satanite refractory morter! I'll be able to stick a 5x7 crucible made of 3/8 well pipe in there. Satanite is rated for 3,000 degrees F, so I should be able to cast something like Brass, once I've cut my teeth on Aluminum.

The overall objective here is complete energy self sufficiency. While I am totally intrigued by Stirling technology, it just doesn't seem to be developed to the point of real feasibility, yet. I've not given up and will be happy to brainstorm and experiment, but I need/want to become self-sufficient as quickly as possible.

So I hit upon extremely low rpm Lister Diesels. They're ridiculously long-lived, easy to maintain, extreme fuel sippers, and will probably run on at least some used motor oil (not to mention veggie oil), plus road diesel has been coming down in price pretty fast recently($1.95 at the closet station). The only problem is, yeah you guessed it... new EPA regs came out. I don't think they can be imported here any longer. I just love our Federal overlords. :tired:

I'm stuck either trying to find an old one or building a new one from scratch. Which, I'll have the means, if not the ability right off the bat, to do with a CNC, Foundry, Metal lathe w/ milling attachment setup.

Tomorrow I'll know whether or not I've won a decent Atlas lathe from the wonderful world of government auction. If so, I have the dubious honor of making a 1500 mile round trip to go get it. Whee!

So I suppose my setup process so far is:

CNC, Foundry/casting, metal lathe, Lister Diesel restoration OR Lister Diesel fabrication OR maybe an old Bamford or similar.

Simultaneous effort on Stirling research and design. One big roadblock I've come up against in THAT tho, has been finding books by the big names in the field that are actually still in print!

I tried to find a copy of James Rizzo's two volume set "Stirling Engine Manual"... and could only find Volume I. Volume II is where most of the meat is at, I think.

Nor was I able to locate Andy Ross's book "Making Stirling Engines." It appears to be in revision.

I may eventually buy "The Regenerator and the Stirling Engine" but I haven't bought a $200+ book since college and I'm sure I don't know enough about the Stirling Engine field for this book to be worth the outlay, yet.

OneAndy
03-09-2009, 02:19 AM
Oh, I also had another idea:

I wonder if it would be worthwhile to have two engines working on the same alternator or generator head?

For example, build a super duper alternator. Build a wind turbine. Then build a Solar Stirling and have both the shaft of the Stirling and the turbine spinning the same alternator. This would save you having to build or buy a second alternator.

And if you could place the Stirling in such a position that the wind turbine is helping the Stirling achieve a greater temperature differential by increased air cooling... well then all the better.

Big problem I foresee, tho, is the engineering requirements of putting your Stirling up there on the tower with the wind turbine. You could avoid this by placing the Stirling on the ground underneath the turbine and link it to the alternator with gears and such, but then you lose the theoretical temperature differential advantage plus mechanical inefficiency in the linkage to the alternator.

greybeard
03-09-2009, 05:11 AM
Phil - pm for you

Jerry - Hi. Re the cnc, I finally got the #1 going, but as the software seemed a bit erratic to the extent of gently lifting the gantry off the rails with an unprogrammed z movement of its own, I decided to move on to #2 and a switch to another programme. I've got quite a bit downloaded, so I'll play with that later.
For the moment, though supposedly retired, I seem to be cramming in more work than ever, so progress on all fronts is as slow as ever.
Re the parabolic/trough progs. Was the parabola from an Indian article showing a "petal" form raised from an ally sheet ? I've got that somewhere, or can find a link I'm sure. Ditto the trough - if that's a simple graph calculator, I'll attach that here.
I'll have a search for stuff today, and post later.

Andy - I didn't think I'd ever say it, but casting hot metal is probably one step too far for me :D
I know what you mean about making even a wood router completely rigid(see above), tempting though it is to think of the product as having a much lower tolerance, and a bit of movement here and there might give it a hand made look...(chair)


..... While I am totally intrigued by Stirling technology, it just doesn't seem to be developed to the point of real feasibility, yet. I've not given up and will be happy to brainstorm and experiment.....

This is painfully familiar, and I sometimes stop and wonder if it's the principle or the goal that's driving me.


I wonder if it would be worthwhile to have two engines working on the same alternator or generator head?

For example, build a super duper alternator. Build a wind turbine. Then build a Solar Stirling and have both the shaft of the Stirling and the turbine spinning the same alternator. This would save you having to build or buy a second alternator.
That has a certain appeal.
Though I know of the arguments for and against vertical axis turbines, it's what I have planned for my own situation, and that would make coupling a lot easier.
Regards all,
John

greybeard
03-09-2009, 01:15 PM
Jerry - I'm not sure if this was the site you had in mind, but I'll put the link up anyway.
This site also carries a link to the Indian(?) site I mentioned above, and another to an earlier article.
http://graffiti.virgin.net/ljmayes.mal/var/parabola.htm

Here's a link to the parabola graph software I found very useful to print out huge curves to paste onto plywood formers.

http://mscir.tripod.com/parabola/

CJL5585
03-09-2009, 04:22 PM
Greybeard,

The Parabola calculator was the program that I was looking for. The other one appears to be good too.

Thanks a million. I have been run ragged for a couple of days trying to get retired. I did not know there was so much paperwork involved.

Thanks again.
Jerry

greybeard
03-09-2009, 05:33 PM
.......I have been run ragged for a couple of days trying to get retired. I did not know there was so much paperwork involved......


That's only the start.
It's taken me about three years to persuade people that I have retired, and taken me about the same length of time to believe it myself.

Enjoy it.:)

John

OneAndy
03-10-2009, 01:40 AM
Phil - pm for you



Andy - I didn't think I'd ever say it, but casting hot metal is probably one step too far for me :D

John

Very doable.

www.backyardmetalcasting.com This guy is AWESOME.
www.buildyouridea.com Same, but he mostly does castings in support of his CNC work.

greybeard
03-10-2009, 04:51 AM
Daren't let SWMBO see those sites :D

Edit: too late !
Her quote " I remember hearing an interviewer asking Henry Moore's duaghter what her early memories of her mother were. 'Mother complaining of finding all the saucepans with lumps of molten lead in them' ".

John

OneAndy
03-11-2009, 02:35 AM
Daren't let SWMBO see those sites :D

Edit: too late !
Her quote " I remember hearing an interviewer asking Henry Moore's duaghter what her early memories of her mother were. 'Mother complaining of finding all the saucepans with lumps of molten lead in them' ".

John

Hah, prior to getting into CNC, I built a real basic pantograph for wood working...

I made all my stylii from melted lead in a friend of mine's old Lee melting pot.

The molds were just hardwood (mesquite scraps) that I plunge cut with the specific bit on a drill press.

Drill hole, remove bit and replace with steel rod, lower into hole, pour lead into hole. It's amazing how smooth a lead casting will turn out, even in wood.

So who is SWMBO? Is that your wife unit?

greybeard
03-11-2009, 04:19 AM
You can us both, if you've a mind to, at www.fanmaker.co.uk
"A wife unit". Is that like a SWAT team ? :D

OneAndy
03-11-2009, 03:20 PM
You can us both, if you've a mind to, at www.fanmaker.co.uk
"A wife unit". Is that like a SWAT team ? :D

Hahaha...

Nice beard. Lovely bride.