Anyone interested in building cheap DIY parabolic troughs?
azuredu
method easy enough to allow me to build one on materials bought from
DIY shops. Cheap but not of bad quality: I've had one with a
concentration ratio of 30 times, and am building an improved one
aiming at 80 times. This is top professional level, the same as the
huge troughs in Californian solar power plants. But I am only using
some plastic plates, a drill and a saw.
The retail materials cost me more than 200$/m^2. But if produced
industrially, the trough may cost as low as 30$/m^2 wholesale price.
Because it is extremely simple. Will publish all the details when
everything is ready, including the trough, a thermal storage unit, and
a thermoelectric unit that will allow you to generate electricity
round the clock.
Everything will be built on my balcony, so you too you can do it.
Solar energy, it's easy and cheap! Interested? Write me to "xiao at
unice.fr".
Morris Dovey
No - if you post to usenet, that's where the responses will be. Below is
a link to a small DIY parabolic trough with a "concentration ratio" of
44:3/8 with a materials cost of less than $140 for more than 2m^2. It
can produce temperatures in the 725F/385C range.
I would be interested in your mount and tracker designs, and suspect
that these would also interest others here.
--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto/Projects/Stirling/Heat.html
azuredu
> I would be interested in your mount and tracker designs, and suspect
> that these would also interest others here.
>
Thanks very much for the link. Nice pictures, although I am afraid
that the rib design gives you some inter-rib deformations which can be
seen from the photos. Cannot judge how severe they are; if you take a
front picture or some tracked pictures, then the severity of the
deformations can be evaluated.
The mount is easy. You have only to add a bearing at each end of the
tube, and whatever you like as chassis. I am using plastic tubes of
used water evacuation as bearings; worked fine.
Tracker is a bit more tricky. I have the circuit design and
microcontroller programming, and will be glad to publish them, but are
you ready to solder circuit boards and burn microcontrollers?
If you really want to go beyond water heating (above 100C), you need
something more than just a bare tube. The tube should be black chromed
(selective coating), and there must be an evacuated insulation layer
enclosed by a glass tube. But if you don't have the means to seal and
evacuate glass tubes, a small vacuum pump will do. See my article on
this. http://wims.unice.fr/xiao/collector.pdf
Once you get there, you still have to make sure that the thing will
last very long and stand to weather. Then it can go into every home.
Morris Dovey
> On Nov 13, 11:34 pm, Morris Dovey <mrdo...@iedu.com> wrote:
>
>> I would be interested in your mount and tracker designs, and suspect
>> that these would also interest others here.
>
> Thanks very much for the link. Nice pictures, although I am afraid
> that the rib design gives you some inter-rib deformations which can be
> seen from the photos. Cannot judge how severe they are; if you take a
> front picture or some tracked pictures, then the severity of the
> deformations can be evaluated.
It hasn't been a problem so far - the concentrated band at it widest
point is 3/8 inch (9.525mm) on a 1 inch diameter target. It would, of
course, be better to illuminate the entire bottom half of the target
tube, but we haven't gotten around to adding spacers to lower the tube.
> The mount is easy. You have only to add a bearing at each end of the
> tube, and whatever you like as chassis. I am using plastic tubes of
> used water evacuation as bearings; worked fine.
Everything has been easy - until we try to make it idiot-proof. :-)
I'm interested - please post links to photos when you have them. I'm
always looking for better methods...
> Tracker is a bit more tricky. I have the circuit design and
> microcontroller programming, and will be glad to publish them, but are
> you ready to solder circuit boards and burn microcontrollers?
Probably (I've been working on computer circuitry since the early
1960's) - although my eyes aren't as good as they once were. I think I'd
much prefer a passive pneumatic/hydraulic system to an
electrically-driven system, though.
> If you really want to go beyond water heating (above 100C), you need
> something more than just a bare tube. The tube should be black chromed
> (selective coating), and there must be an evacuated insulation layer
> enclosed by a glass tube. But if you don't have the means to seal and
> evacuate glass tubes, a small vacuum pump will do. See my article on
> this. http://wims.unice.fr/xiao/collector.pdf
I'm not interested in water heating at all. I just want to heat air -
and the 725F/325C is about all I need from the trough shown.
> Once you get there, you still have to make sure that the thing will
> last very long and stand to weather. Then it can go into every home.
I have the ability to CNC cut aluminum ribs up to eight feet wide that
can be used for sandcasting - but I think I'm a long way from being
ready to take that step - and the collector is not the primary focus of
my efforts.
For the testing done over the past two years, the plywood ribs have been
adequate.
Morris Dovey
> http://wims.unice.fr/xiao/collector.pdf
Worth reading. We're working toward different objectives which produce
different design criteria - but your presentation is good.
Thank you for sharing it here.
azuredu
> I'm interested - please post links to photos when you have them. I'm
> always looking for better methods...
Sure.
>
> > Tracker is a bit more tricky. I have the circuit design and
> > microcontroller programming, and will be glad to publish them, but are
> > you ready to solder circuit boards and burn microcontrollers?
>
> Probably (I've been working on computer circuitry since the early
> 1960's) - although my eyes aren't as good as they once were. I think I'd
> much prefer a passive pneumatic/hydraulic system to an
> electrically-driven system, though.
To me it is not obvious how you can reach the cost, precision and
versatility of electronics.
A microcontroller is just a few dozens of cents wholesale price.
Adding a motor, you get it. And you get things that passive method
doesn't offer, such as emergency resting when the HTF circulation has
a trouble.
> I'm not interested in water heating at all. I just want to heat air -
> and the 725F/325C is about all I need from the trough shown.
No, it is not that you can get 325C at dry burning that you can get
325C real heat output. The efficiency will drop to near zero at this
level. I've also got 300C+ temp for my earlier trough at dry burning,
even damaging the equipement. But with circulation, the only
reasonable thing is to heat water.
Therefore an evacuated receiver is a must for high temperature.
Morris Dovey
If you have even a passing interest in analytical geometry, you
shouldn't miss this gentleman's Gallery of animated algebraic surfaces at:
http://wims.unice.fr/~xiao/gallery/
Nice work!
Morris Dovey
> On Nov 14, 2:25 pm, Morris Dovey <mrdo...@iedu.com> wrote:
>> I'm interested - please post links to photos when you have them. I'm
>> always looking for better methods...
>
> Sure.
>>> Tracker is a bit more tricky. I have the circuit design and
>>> microcontroller programming, and will be glad to publish them, but are
>>> you ready to solder circuit boards and burn microcontrollers?
>> Probably (I've been working on computer circuitry since the early
>> 1960's) - although my eyes aren't as good as they once were. I think I'd
>> much prefer a passive pneumatic/hydraulic system to an
>> electrically-driven system, though.
>
> To me it is not obvious how you can reach the cost, precision and
> versatility of electronics.
Nor to me - that's why I was so interested in how you were solving that
problem. I really was looking for a solution - not a disagreement...
> A microcontroller is just a few dozens of cents wholesale price.
> Adding a motor, you get it. And you get things that passive method
> doesn't offer, such as emergency resting when the HTF circulation has
> a trouble.
Very true. My primary application is for regions where there may be no
electrical infrastructure at all, and requiring any kind of
electricity-generating subsystem is not an option.
>> I'm not interested in water heating at all. I just want to heat air -
>> and the 725F/325C is about all I need from the trough shown.
>
> No, it is not that you can get 325C at dry burning that you can get
> 325C real heat output. The efficiency will drop to near zero at this
> level. I've also got 300C+ temp for my earlier trough at dry burning,
> even damaging the equipement. But with circulation, the only
> reasonable thing is to heat water.
:) But I don't _need_ hot water (or even steam). We are addressing very
different requirements. BTW, 325C is a measure of temperature, not of
heat - although it works to think of temperature as a measure of heat
(energy) /density/.
> Therefore an evacuated receiver is a must for high temperature.
Ok. :)
Morris Dovey
> :) But I don't _need_ hot water (or even steam). We are addressing very
> different requirements.
My apologies - it didn't occur to me until after I hit <send> that you
might find more information about the specific application helpful in
understanding what I'm doing.
The second drawing at
http://www.iedu.com/DeSoto/Projects/Stirling/Fluidyne.html
Is of a fluidyne (Stirling cycle heat engine) under development. The
heat produced is used to expand the air within the engine and is then
discarded to cause the air within the engine to contract.
This expansion/contraction provides a direct conversion from solar
energy to mechanical energy that can be used for a number of
applications (such as pumping and refrigeration) in regions where there
is neither fuel nor electricity available.
azuredu
> The second drawing at
>
> http://www.iedu.com/DeSoto/Projects/Stirling/Fluidyne.html
>
> Is of a fluidyne (Stirling cycle heat engine) under development. The
> heat produced is used to expand the air within the engine and is then
> discarded to cause the air within the engine to contract.
Yes, I am greatly interested in that. Do you have a working model?
What is the cost and efficiency projection?
azuredu
> The second drawing at
>
> http://www.iedu.com/DeSoto/Projects/Stirling/Fluidyne.html
>
> Is of a fluidyne (Stirling cycle heat engine) under development. The
> heat produced is used to expand the air within the engine and is then
> discarded to cause the air within the engine to contract.
I should tell you that I also have a cheap thermal storage solution
(high temperature, 200C+). So if you have a working heat engine, you
may get round the clock electricity generation and so on. A real
solution to global warming.
But I have some worries about the efficiency of such engines.
azuredu
> Very true. My primary application is for regions where there may be no
> electrical infrastructure at all, and requiring any kind of
> electricity-generating subsystem is not an option.
The controller only consumes less than 0.1W per piece, so a very small
PV cell will be enough.
But I cannot simply post the circuitry somewhere. There are too many
specifications and uncertainties. You won't be able to make it run if
you don't reprogram the microcontroller, changing parameters. That's
huge trouble.
I have an idea. There's somebody in China who's test manufacturing my
controller. He's just collecting components, doesn't have a prototype
yet, let alone commercial product. And I don't know whether he's
willing to sell one at this stage. But I can ask.
The projected wholesale price is just a few dollars a piece. At this
stage, I know nothing about eventual prices.
Morris Dovey
We have a working model only of the low-temperature version shown at the
bottom of
http://www.iedu.com/DeSoto/Projects/Stirling/Dyne.html
The fins have been removed from the cold end of the regenerator tube and
both the hot head and the regenerator are now wrapped with fiberglass
wool - and the materials cost of that engine is just under $100. We
don't have the means to acquire the data needed to calculate efficiency,
but have set a target of 25% or greater.
Since I last updated the web site I've started design and software
modeling activity for a version of the high-temperature engine that uses
air only (no fluid) which I've labeled a "dryadyne". I'm hoping that by
eliminating the fluid component altogether, efficiency will be
significantly improved and maintenance eliminated completely.
Morris Dovey
> The controller only consumes less than 0.1W per piece, so a very small
> PV cell will be enough.
Yes, low-power CMOS controllers are power-friendly - it's the motors
that are the real headache. :(
I'd like to arrive at a design that would allow anyone with minimal
carpentry and plumbing skills to build with reasonably-available
materials - and that would provide reliable service to someone with neither.
I'm unsure that, for example, a farmer in a remote area would be able to
debug an electronic tracker problem - and I'm willing to accept a lesser
performance in order to have something he/she can fix on the spot.
Duane Johnson at http://www.redrok.com/led3xassm.htm has an led-based
tracking controller circuit that you may find worth a look...
azuredu
> > Yes, I am greatly interested in that. Do you have a working model?
> > What is the cost and efficiency projection?
>
> We have a working model only of the low-temperature version shown at the
> bottom of
>
> http://www.iedu.com/DeSoto/Projects/Stirling/Dyne.html
>
I should be missing something, but how do you do to output the
mechanical work?
Morris Dovey
At the tuning tube, where there's an alternating positive/negative
pressure. The pump diagram at
http://www.iedu.com/DeSoto/Projects/Stirling/Pump.html
should help you to immediately grasp the idea. Let me invite you to
browse through the pages with links at
http://www.iedu.com/DeSoto/Projects/Stirling/
(the pages are all fairly short) so you can get a more complete picture.
In fact, please feel welcome to browse the entire site - that's why it's
there. :)
Morris Dovey
> I should tell you that I also have a cheap thermal storage solution
> (high temperature, 200C+). So if you have a working heat engine, you
> may get round the clock electricity generation and so on. A real
> solution to global warming.
I've bookmarked your home page. Right now my focus is on the engines
themselves. (But thank you.)
> But I have some worries about the efficiency of such engines.
The efficiency depends on the temperature difference between the hot
head and the cold head. At 325C there's a theoretical limit around 55% -
which is good compared to current PV conversions.
These engines are only suitable for a limited subset of applications,
but I'd be happy to produce solar solutions to only a few of the world's
problems. :-)
Jeff
How are you doing that? What are using for transfer fluid?
I've been thinking of a low frequency acoustic stirling. The receiver
would have a glass front (toward trough) insulated on back and sides
with an absorber plate or screen in the middle. You can easily mock up
something like a Rijke tube. The acoustic stirling is closed circuit and
resonant. I don't think that you'd get the carnot efficiencies as you
might with other working fluids that could operate at higher temps.
Jeff
>
azuredu
>
> These engines are only suitable for a limited subset of applications,
> but I'd be happy to produce solar solutions to only a few of the world's
> problems. :-)
Here's my first suggestion for your fluidyne.
You could replace the open tube by a closed chamber with elastic
walls, such as a bellow. The moving wall of the chamber then will
allow you to output mechanical work, without friction.
Of course you'll have to translate oscillatory movement into rotation,
and fight for the material's wearability.
Moreover, when the whole system is closed you can increase internal
pressure to gain output power.
More suggestions will come later. I have got the impression that your
design is not very optimised. By the way, I suppose that you know that
the best working gas is helium?
Morris Dovey
> On Nov 14, 6:48 pm, Morris Dovey <mrdo...@iedu.com> wrote:
>> These engines are only suitable for a limited subset of applications,
>> but I'd be happy to produce solar solutions to only a few of the world's
>> problems. :-)
>
> Here's my first suggestion for your fluidyne.
>
> You could replace the open tube by a closed chamber with elastic
> walls, such as a bellow. The moving wall of the chamber then will
> allow you to output mechanical work, without friction.
Yes, friction will require work to overcome - but it also takes work to
deform an elastic wall.
> Of course you'll have to translate oscillatory movement into rotation,
> and fight for the material's wearability.
Why "of course"? I'm perfectly happy with linear oscillation.
> Moreover, when the whole system is closed you can increase internal
> pressure to gain output power.
I wish that were so, but output power is determined by the input power,
and efficiency is determined by the hot/cold head temperature
differential. The most effective way to increase output power of a
reasonably efficient engine is to increase input power. In this case,
that would mean increasing the capture area of the solar trough.
> More suggestions will come later. I have got the impression that your
> design is not very optimised. By the way, I suppose that you know that
> the best working gas is helium?
We are optimizing different things. You seem to be maximizing the device
efficiency, and my objective is to maximize availability of benefit with
efficiency as a secondary consideration. We aren't exactly at
cross-purposes, but neither are we trying to solve the same problem. :)
Having said that, let me emphasize that your suggestions are appreciated
and that I am still /very/ much interested in ways to build
inexpensive parabolic troughs, mounts, and tracking systems.
One additional note - I have a practical algebraic two-surface challenge
that, of all the people I've met, you might best be able to solve. If
you're interested, I'd be happy to pass it along. I've attempted an
intuitive solution, but I'm sure it's sub-optimal. :)
azuredu
>Yes, friction will require work to overcome - but it also takes work to
>deform an elastic wall.
The difference is that work applied to deform an elastic wall is not
lost: it is recovered when the wall deforms back. Well, depending on
the material.
>
> > Moreover, when the whole system is closed you can increase internal
> > pressure to gain output power.
>
> I wish that were so, but output power is determined by the input power,
> and efficiency is determined by the hot/cold head temperature
> differential. The most effective way to increase output power of a
> reasonably efficient engine is to increase input power. In this case,
> that would mean increasing the capture area of the solar trough.
Sorry, but I meant output power per volume of engine. This is
certainly an important criterion for such a product, whatever the
purpose.
>
> > More suggestions will come later. I have got the impression that your
> > design is not very optimised. By the way, I suppose that you know that
> > the best working gas is helium?
>
> We are optimizing different things. You seem to be maximizing the device
> efficiency, and my objective is to maximize availability of benefit with
> efficiency as a secondary consideration. We aren't exactly at
> cross-purposes, but neither are we trying to solve the same problem. :)
No, efficiency is only one of the objectives. There are also cost and
volume that are important too.
>
> Having said that, let me emphasize that your suggestions are appreciated
> and that I am still /very/ much interested in ways to build
> inexpensive parabolic troughs, mounts, and tracking systems.
>
Don't worry; that will come.
> One additional note - I have a practical algebraic two-surface challenge
> that, of all the people I've met, you might best be able to solve. If
> you're interested, I'd be happy to pass it along. I've attempted an
> intuitive solution, but I'm sure it's sub-optimal. :)
Yes but would it be better to send me by email? This is off subject.
GEOD998
i finally managed to find a few minutes to check out the group page
again..and at first glance i was ready to dump the whole thing.adds
for shoes purses and god knows what else made me wonder why i even
bother...BUT...then..i find this exchange between you two
brainiacs,and it rekindled my hope for the web and these groups.i must
admit that I was a bit leary of azured's first post and the tone of
the tit-for -tat that was seemingly winding up tightly,but then the
very spirit of what I think the group and the whole WWW beamed through
a spirited but civil exchange of ideas and info that i found
educational and exhilerating that addressed just about everything i'm
here for. Thank You Morris and Azured for keeping the true spirit of
free exchange of information alive....now if we could just get rid of
the shoesalesmen,lol
Morris Dovey
> i finally managed to find a few minutes to check out the group page
> again..and at first glance i was ready to dump the whole thing.adds
> for shoes purses and god knows what else made me wonder why i even
> bother...BUT...then..i find this exchange between you two
> brainiacs,and it rekindled my hope for the web and these groups.i must
> admit that I was a bit leary of azured's first post and the tone of
> the tit-for -tat that was seemingly winding up tightly,but then the
> very spirit of what I think the group and the whole WWW beamed through
> a spirited but civil exchange of ideas and info that i found
> educational and exhilerating that addressed just about everything i'm
> here for. Thank You Morris and Azured for keeping the true spirit of
> free exchange of information alive....now if we could just get rid of
> the shoesalesmen,lol
I'm afraid that there's only one brainiac in that dialog - and that's
the gentleman on the French Riviera.
I agree - usenet is (or can be) one of the most powerful tools for
sharing ideas. I've been tremendously enjoying one of the (normally
invisible) side effects of this conversation - a Korean engineer
resonated and posted links on a forum in Seoul resulting in a feeding
frenzy at my web site that's finally beginning to slow down a bit today.
It makes me wish I could speak Korean (along with French, German,
Cantonese, Danish, Mandarin, Italian, Finnish, Japanese,...)
Civility doesn't cost anything - and everyone knows things I don't. I
figure it's in my best interest to keep both these facts in mind and to
avoid burning bridges.
The shoe salesmen and the tinfoil hat wearers are vulnerable to
filtering if you use almost any regular mail/news client - and BTW,
there are a number of free news servers about. I use aioe.org as a free
backup for my normal/local service (without filtering so I have a backup
to handle cases where my filtering was overzealous).
john
Could you give more details? (Please...!?)
Thanks
John
azuredu
wrote:
> Now you've gotten me interested in your cheap thermal storage system.
> Could you give more details? (Please...!?)
Sure but I have to prepare technical explanations, so probably in
January.
For the time being, the rough idea. First all, this is (best suited)
for high temperature thermal storage, in the range of 200C to 400C.
With thermal oil as heat exchange fluid. This is usually the case for
large solar power plants, but the cheap sollar collectors will soon
bring this operating mode to ordinary homes.
The idea is very simple. You melt recycled glass to form some kind of
bricks, and let the oil pass thru these bricks. So it is the glass
bricks that store heat for nighttime use. As it is with high
temperature, you will be able to get electricity generation at night,
for example to charge your electric car.
Why this will be cheap: recycled glass is a kind of urban waste for
which it is hard to find reasonable use. So sometimes people will even
pay you to use it. All you need is the cost of energy to heat and melt
it.
And maybe the biggest technical point is why the glass bricks will not
break under frequent temperature changes. Well, please be a little bit
patient for these details.
azuredu
http://wims.unice.fr/xiao/solar/index.html
And the do-it-yourself manual:
http://wims.unice.fr/xiao/solar/diy-en.pdf
Enjoy!