Solar Concentrator Revival: Solar Tracking
Marcin Jakubowski
Please welcome a new member to the group - Milton Ellis. We just had
interesting discussion - and there may be some insight to cracking the
solar tracking problem on the linear slat concentrator - by using
linear actuators. Here is a copy of our last conversation (ME-Milton,
MJ-Marcin). The following is also instructive as a review - of some of
the progress to date.
ME:
My interest in in a solar concentrator system I guess is similar to
yours, perhaps not quite as idealistic. I have been researching to
construct my own system. My thinking is that I can create an energy
self sufficient home complete using Solar thermal energy. The trick is
to make it cheap enough that works well enough. I would like to
develop a system that will be obviously good for me, and the panet.
But also other people will think it is great and want me to make one
for them. My ultimate goal is to build some small apartment blocks, or
townhouse development with these systems incorporated, as well as
other differences like many of the Zero Energy Design concepts etc.
I was thinking along the lines of using a trough system like
http://wims.unice.fr/xiao/solar/collector.pdf .
MJ: We were in touch with the man, but I question the cost performance
of this system. Present material costs of $200 per collector (only
about 1 sq. meter) are about 20x higher than our expectations for our
collector design (http://openfarmtech.org/index.php?
title=Solar_Turbine_Working_Paper)
ME: I have also found your system and can see it has a lot of merit. I
was/ possibly still am, thinking contructing a trough system by
creating a mould, then replicating the design easily from fibre glass.
MJ: This is a good option for a one-off system. If our goal is
replicability, I suggest the design in the Working Paper.
ME: For a receiver I was thinking of using a single vacuum,
commercially producd tube collector. I have many other ideas that I am
looking into.
I hope I am not boring you too much but, to give you a bit of an
idea. Gas back up/ supplementation for the water heating. Your biomass
pellets or pyrolysis oil would also work fine of course. Wind tubines-
I also have many ideas. For horizontal axis, I would look at having a
varible pitch system to maximise it's performance- like CSU (constant
speed units) aircraft propellors. Controlled by an Audrino over
hydraulic control system. I would also like to use a driveshaft to
bring the mechanical output to ground level- think of a helicopter
tail rotor boom turned vertical. A bit of extra complexity, expense
and transmission losses but many advantages like generator, pitch
control, braking, speed control systems all on the ground. To go
further why not tie it to the Solar generator/ steam engine shaft with
a sprag clutch. This way whether the sun is shinning or the wind
blowing, or the pellet furnace is stoked there is mechanical power to
the generator. All of these systems could essentially be seperate
autonamous 'modules'. There would be a option to add them at different
times or not at all. I also like the idea of vertical axis turbines,
or banks of them space permitting- small clear perspex, outputs gear
tied together. Solar thermal energy could also drive airconditioner/
refigeration systems using absorbtion chillers or my favourite steam
jet ejector vacuum chillers. Sure a luxuray, but can also be an
atmospheric water generator using heat pipe dehumidifying evaporator
units. If you want any details of any of this stuff, I would be happy
to send you more.
Anyway back to the subject at hand. Hydraulic slat controls. I
would use a linear hydraulic/ jack/ ram. Constucted the same way as
your uniflo steam engine. No crankshaft of course, but the 'con' rod
would be actuator rod to change the slat angle. The control of the
hydraulic actuator would be driven by a photo resistor/ or similar,
feed back sensor attached to the slat. The sensor would have an
adjustor screw to lean it to aim/ align the slat correctly. The photo
sensor would be connected to a control circuit the same as for
electric motors- Adruino etc. You guys are already going down this
path with your Steam engine injection valve timing control system. I
would also have a slightly wider collector opening, seeing the slats
are also 6 inches, to allow for a little misalignment etc. Depending
on the motive 'fluid' ie temp and press's involved, decided on you may
be able to use PVC tubes, or something similar, for cylinders, nylon
(kitchen cutting boards) for the cylinder end plates and pistons.
MJ: History has not yet produced any workable plastic engines - the
poorly designed Green Steam engine is a good case of such failure. One
guy I know of is currently developing a mass-producible plastic one. I
doubt this would provide the longevity required in our project,
relegating such concepts to the status of toys.
If you talk about ORC, that is a feasible route, but exotic
refrigerants, among other issues, limit the ease of their
replicability. We will consider this if we fail with the steam engine.
Plastic is out for steam, unless we want to add this development point
to an already complex project. Stick with metal, as it's proven. The
key is simplicity - our main point being that this is feasible with
proven technology and clever design - we don't need to reinvent the
wheel on anything, we just need to add low-cost electronic actuation
to this.
If we disprove this possibility, we can go further.
ME: The actuator rod could be stainless bar stock as long as works
with threads on either end to attach the piston head and slat linkage/
bellcrank. No corrosion issues, cheap and readily available, easy to
machine using stainless, PVC, nylon etc. End plates tied together to
the cylinders using bolts, threaded rods etc. I would look at doing
all 16 actuators in one unit ganged together using one end plate.
MJ: Are you suggesting a single moving actuator or 16 actuators?
By researching the UK system, ( http://openfarmtech.org/weblog/?p=446
) , I found that the system failed to achieve satisfactory alignment
when using a ganged linkage - and they had to go back to individual
actuators on each slat. .
ME: Unit attached to the slat frame through the end plate/s in a
convenient location, probably under the collector.
Heat engines, no I fully agree you are using the most cost effective
soluton that I can see. The simplest, cheapest possible (but done/ put
together well) is definately the key. I was just curious if you know
about them/ have looked at this stuff as I like to keep an open mind
and learn about different ways to do things.
MJ: After a year or two of probing the question, we went through ORC,
turbines of all sorts, Stirlings, and concluded on steam piston.
http://openfarmtech.org/index.php/Solar_Steam_Engine_Selection_Process
ME: You didnt comment on inclining the slat frame from the
horizontal. Think of the cinema, with the sun close to the horizon,
like the screen, if everyone was seated horizontally the people in the
back would not be able to see. Not my idea the Greeks used it for
their Greek tradgedy amputheatres, then the Romans copied for Collesum
design etc.
MJ: Sure, agreed. Inclining the slat frame is the correct route. The
limit of this is cost considerations once the height at the back
reaches a certain value. The consideration there is structural
stability for wind loads. Windless conditions may make this feasible
in certain locations. Using natural slopes is another solution.
The key consideration is that - usually, the most expensive part of a
concentrator system is structure. Our system avoids this cost by
virtue of low-to-ground structure.
ME: Yes, I would be happy to contribute on a monthly basis.
MJ: Please Subscribe at http://openfarmtech.org/index.php/Support_Open_Source_Ecology
ME: It is good value for me to be able to communicate some of the
stuff in my head with people that think about the same sort of things
as myself. I have virtually no body I would dare to bore, or is
socially responsible enough with my ideas.
MJ: Well, let's then see how we can work on that together. The stakes
are high. This is not boring stuff, indeed I am convinced that cost
reduction on the solar concentrator power system is one of the
breakthrough steps required to attain a renewable energy future.
Others may propose a solar hydrogen/fuel cell future, but I am of the
opinion that the simple steam engine-linear concentrator system will
prove economically superior to the former. Our goal is to porduce data
points for this question.
ME: Most people complain, accept the bad norms, and dont try to
think of solutions or try to drag themselves away from their TVs. If
you like what I am saying so far please feel free to run it by, or I
can, some others involved in the project to get their veiws and I will
take up the direction with the questions raised.
MJ: I think you may be right on with the concept of linear actuators.
As a first technical point, tell me what the strategy would be for
effective linear actuation with a hydraulic or pneumatic system. Can
you get the accurate positional/angle control necessary for alignment?
I think this will be our main development point to crack - and I
suggest that you work on prototyping this at your earliest
convenience. If we can solve this, that would be a major
accomplishment for the project. The longevity issue will then be
guaranteed - as opposed to the fickleness of electric drive.
...
This seems to be a synopsis of the discussion about tracking in this group so far. Red Rok energy guy (sorry, his name slips my mind right now) raised concerns about precision and accuracy.
talking about the fresnel trough:
tracking with feed back for each mirror is tricky because the mirrors aren't trying to face the sun directly, but hit a target. Can our actuators translate the motion of something following the sun exactly in to 1/2 that movement for the actual mirrors to follow? conventional gears, for instance, would probably be too sloppy.
With hydraulic linear actuators, I doubt one could get necessary accuracy controlling many arms centrally. Often, pistons have feedback so that their position is constantly known and their length is adjusted based on that. would this sort of control make our system too expensive? controlling the position of hydraulic pistons is old hat in industry.
The question is entirely accuracy in tracking and in carrying out adjustments in response to the tracking signal. I say, figure out what tracking we can do cheaply, and then design the system to perform well with those tracking figures (ie, non-imaging design).
Others might say keep the design as is and try to perfect tracking.
-Elliot
Marcin Jakubowski
-----------------------------
Very interesting. I've subscribed to the group.
But haven't found out how to reply to a discussion via email, so feel
free to put this mail including attachments into the group if you
think
it to be valuable.
BTW, you should fix the "scheduled for mid-2009" in the group
description.
concerning the discussion on controlling the slats:
I'd also go for individually controlled slats -- I've already thought
about
the necessary electronics for arduino to be able to control more slats
than
the arduino has I/O pins by using a serial-in/parallel out shift
register.
That way we can select which slat and corresponding sensors we want to
read/write and use the arduino to adjust each slat in a round-robin
fashion.
I have thought about using cheap linear motors and probably some
plastic gear
for controling each slat (gear can probably be made with a RepRap).
The
arduino would turn one of the slats (quite slowly) until a
photoresistor has
seen the edge of the reflected light on both edges of the slat. The
arduino
would measure the time it took from one edge to the other and then
adjust the
slat to the middle position just by measuring the time when turning
the motor
backward. Since the arduino can do quite good time measurements we
would
achieve enough precision, I think.
I've attached a drawing how I think the photoresistors could be
mounted
in the path to the central concentrator, and, yes, this will cast some
shadow but the resistors can be mounted on a very thin structure, the
resistors I'm envisaging are 5mm in diameter (0.2 in)
Drawing: http://openfarmtech.org/index.php/Solar_Concentrator_Tracking
Ralf
--
...
Since the arduino can do quite good time measurements we
would
achieve enough precision, I think.
Accuracy, not precision, is the concern. arduino's time precision is one thing, but does that precise number accurately match the position of the mirror? Slop in the gears, motor speed variation and differing wind/gravitational loads on the mirrors need to be accounted for.
Again, in industry, piston synchronisation is usually achieved through feedback. but it is a topic worth researching more.
-elliot
Marcin Jakubowski
angle, as well as active feedback control for fine adjustment.
Marcin
Marcin Jakubowski
and the tracking process:
---------------------------
We cant really practially have two seperate position signals. Firstly
they are bound to be different outputs so which one to we use? 2
different signals would cause a conflict. In an aircraft system there
are usually two systems, for redundancy. However there is a priority/
hierachy system where only one gets used at a time. The priorty order
is determined by what signal has proved in the past to be more
reliable. The others may be on but not driving anything, just waiting
until the others above them in the priority sequence to have failed.
They will be deemed failed when they act outside reasonable limits.
May be we will do this too if for example the sensors prove to be
unacceptably unrelable, or it is just too important to not have the
system work. Of course it is extra complexity, expense, twice as many
things to break etc.
May be if we could get the one actuator all slats linked together
arrangement working it would be far more worth it. I will do some more
work on this and get back to you on the feasibility of a single
actutor system. Remember if we took every past failure as a reason not
to try something ourselves we would not try anything. Of course the
crux is why they failed, and if we can do it differently and better.
As you say we shoud learn from other's mistakes, not needing to
reinvent the wheel. May be a redundancy sysem is not needed, because
the system is quite reliable- we hope. May be we decide our design
compromise is best that it has a self diagosis, perhaps online even,
alarms for faults. We simply run out to change a sensor for example
when an alarm is triggered.
Yes the actuator is just 'moved' until the position sensor says the
slat is at the correct angle to the sun. After all we dont care where
the actuator is only where the slat is. Having said that the actuator
is physically connected to the slat, so for every positon of the slat
there will be a corresponding position of the actuator. We could in
fact measure the slat position on the actuator if we wanted, maybe it
will be easier/ more convenient to do that? At the end of the day it
is all the same thing.
Getting a bit more into Auto pilot theory what actually happens is the
system will hunt/ oscillate back and forth around the 'null' point. It
is not as bad as it sounds as the oscillations get smaller and smaller
until it settles into it's new position. However this is where the
controller/ driver circuit helps.
It will do things like control the
1. rate of travel and
2. widen null point.
The rate control obviously means the actuator will moves slowly so
there will be less 'overshoot'. This is all determined in the
electronic controller circuit. However because we dont know what will
work best we will probably have to experiment with this setting. If
the controller system doesnt allow us to change this setting, this
might be a good mod for the electronics wizzes (not me) in the group
to do. I dont know anything about Adurino, but I would assume that it
has this capability and much more. We would be aiming for things like
quite slow moving actuator movement as the sun moves very
slowly.
Widening the null point is not as desirable because it is decrease in
accuracy. It still might be better than having actuators continually
hunting backand forth overshooting the null because it is so small.
Again more design considerations to thrashed out at some point. We
will practially have to allow for some inaccuracy, like widdening the
collector opening.
Speaking of inaccuracy, another thought that came to me was twist in
the slats. Ie if we move one end of the slat is the other end going to
be the same angle?
Actuator position sensor? I will answer your question about it, even
though from what we have discussed above it might not be needed.
Keeping in mind that 'aviation' technology is actually quite old/ not
cutting edge. This suprises most people. Of course it is very precise,
and reliable for that age. The bottom line is that because of the
standards imposed/ certification process, and the relatively small
volume it is not worth spending lots of money to go through an
expensive certification process just to sell a small volume of planes.
Position sensrs, for actuators, control surfaces or whatever are
usually old technology variable resistors- called fancy names like
LVDT's or RVDT's . Sometimes syncros (like analog electronic
instuments), but yes I think the better modern version would be hall
effect sensors-(remember I am not an electronics wizz by any measure).
They could also be achieved with lasers and grey code readers, and I'm
sure many other way better than variable resistors. Indeed they are
definately one of the week points of the system that keeps us busy
changng them regularly. They have an inherant design fault of rubbing
carbon- it will eventually wear.
Encoding the sensor to know which way to move the actuator. Yes of
course this is needed. Well with my limited knowedge of sensors I will
try to explain this. The type of sensor I have read about in my
research- there are probably more ways to achieve the same thing. Two
photo resistors with with either a wall between them or a tube around
them. Let's call them S1 (sensor 1) and S2. Let's assume the sensors
are facing up and the wall between them, or tube around them, is
vertical up as well.
When the light or sun is direcly above S1 and S2 both will have the
same amount of light hitting them. In this the sensor is aligned with
the sun, ie the 'null' point. The controller circuit will sense they
are equal resistance and will give NO output to drive the electro
hydraulic control valve. Everything is happy, aligned and we are
making power.
However when the sun moves away from directly above the sensor then
one of the photo resistors is shaded by the wall. The controller
circuit now sensors a difference in resistance between the two photo
resistors. Let's for argument sake say when S1 is less resistance than
S2 the controller will give a (-)ve output which will operate the
electro control valve to drive the actuator in the direction of lets
say to lift the slat more vertical because the inclination of the sun
is getting a lesser angle from the horizon. Ie this woud be the case
in the afternoon when the sun is moving towards the horizon. Of course
in the morning the opposite would occur S2 resistance would be
frequently less than S1 so the controller circuit would give a (+)ve
output to the electro hyd control valve driving the actuator to lay
the slat down to align with the sun that is getting higher. I will get
some more pictures done.
Sorry to bore you, but if you have stuck with me you are now very auto
pilot/ solar tracking system literate. I have tried to be as concise
as possible but as you can see there is a bit of ground to be covered.
I know when I'm in trouble whensomeone asks m to 'just' do something.
Usually a pilot wanting me to 'just' work some miracle for him. Or
someone saying can we 'just' design a economical sustainable household
energy system. Doesnt sound like much when they say it quickly. Just
some of my off beat sense of humor. Seriously I love this stuff. And
all the more because it is stuff that no one else has managed to get
right yet.
One quesion for you, what is the collector design output fluid,
pressure and temp.
I look forward to your next questions,
Thanks,
Milton.
Ozheliguy
good to hear from you.
Yes, I can not comment on the accuracy capabilities, as I have no
experience with that. I have read some unverifiable information only.
I am only suggesting the possibility of using hydraulics for the
motive force to aim the mirrors. That I am aware the two motive forces
in contention are electric motors, or my proposal of hydraulics. The
system used to control either a electric motor or a hydraulic motor/
ram actuator can essentially be the same. I have got some
correspondances that I will get onto this discussion group, and some
drawing to illustrate further what I am talking about. Give me a
little bit of time to get it done and loaded.
Costs, well you could well be right. I will look further into the
potential costs involved for what I propose and get details posted for
further comments. It is essentially constructed the same way as the
steam engine. And that seems to be easy enough. Of course we haven't
done it yet, but many before us have done similar. In fact what I am
proposing can be constructed far simpler than the steam engine because
they would have less parts, ie no crank shaft etc, far less pressures
involved, less speed involved etc. So a lot of the same equipment,
skills, technology can be used as the steam engine. Even better I
suggest using off the shelf, cheap and easy to find materials eg
stainless tube with no extra machining ie boring, apart form cutting
it to a decided on length.
I am not sure I understand what you are saying about "Often, pistons
have feedback so that their
> position is constantly known and their length is adjusted based on that"? Perhaps when I get some of the other stuff on here I will have covered what you are saying?
Aligning the mirrors, as you correctly say, not directly at the sun. I
have some ideas, but as I said I am not an expert on solar tracking.
Let me have some more of a think on this and I will get back to you if
I have a possible solution.
To be honest, I am not fully aware of what the current proposed design
is. I am new on here an still trying to catch up. Anything I could
look at to help me get with the program gratefully accepted. Pardon my
ignorance but what is a "non imaging design"?
Cheers,
Milton.
...
do we have to fabiracte our own steam engine like device to do this? I hope not.
Milton said
Yes the actuator is just 'moved' until the position sensor says the
slat is at the correct angle to the sun
I am not sure I understand what you are saying about "Often, pistons
have feedback so that theirposition is constantly known and their length is adjusted based on that"?
1) based on pre-programmed positions, the actuators move the mirrors to set positions. In this case there must be a sensor on the actuator to tell the controller what its position is, so the controller can tell it how far to move. The controller sending commands to the actuator without this feedback will certainly be too sloppy.
2) the mirrors are adjusted until light hits a sensor.
2a) This would require a photosensor for each individual mirror (google linear fresnel array, our proposed system has probably over 30 mirrors). I doubt the accuracy and cost effectiveness of trying to aim each mirror at the target based on photosensors.
2b) a central sensor tracks the sun directly, and each mirror is moved half as much as that one. I think this would need position sensing on all the actuators. splitting hydraulic pressure or whatever would not be accurate enough.
I am in favor of #1 or #2b
linking the slats and only having one actuator would be nice. each linkage has some slop to it though. how much is bearable?
Two
photo resistors with with either a wall between them or a tube around
them. Let's call them S1 (sensor 1) and S2. Let's assume the sensors
are facing up and the wall between them, or tube around them, is
vertical up as well.
This would need a linear lens. the shade from a wall will not give a precise enough signal.
you are thinking something like 2b with linked slats and only two actuators (one to move tracker and one to move mirror array?
Ozheliguy
ah the issue of piston syncronising and position sensors for the
actuatators. My thought was a seperate piston, snesor and control
system for every slat. I am talking a multi piston (one for each
mirror) indvidually controlled, because that was what I though the
direction the group was wanting to go down. I think one piston and one
control system and sensor controlling all the slats would be the way
to go. However it has been unsuccesful in the past apparently?
Yes I was thinking to fabricate it. It should be signifcantly easier
and much less time and effort. I think we could simply use easy to
source stainless tubing for the cylinder, and bar stock for the ram
maybe? Turn up a piston, machine some end plates (the biggest work)
and some O rings and tie bolts. Just some thoughts.
Thanks.
Rick Thomas
work perfectly well on 12V.
They are cheap and come in a variety of sizes.
Rick...
Hi,
Thanks.
--
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For more options, visit this group at
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See
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ranscript
Marcin Jakubowski
Links to others are here:
http://openfarmtech.org/index.php/Medium_and_Small_Scale_Concentrated_Solar_Thermal_Power_Platform
Marcin
--------------------------------------------------
Marcin Jakubowski, Ph.D.
Open Source Ecology
http://openfarmtech.org/weblog
http://www.replab.org
opensourceecology at gmail dot com
Skype: marcin_ose
--------------------------------------------------
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Ozheliguy
good to hear from you. You may well be correct. I'm all for using
existing available cheap components. Can you give some more specifics
on how cheap, how perfectly well they work?
1. The cost, is crucial to this project succeding so can you give more
info of what can be bought for how much? The electric actuators I
deal with on aircraft, like anything on aircaft, arent cheap, as the
hydraulic actuators arent.
2. The accuracy seems to be of prime concern. I can say that the
electric acctuators I deal with are atleast as inaccurate as the
hydraulic actuators I deal with. They are both of course adequate
otherwise they wouldnt be used. But I guess which millimetre of the
sky an aircraft is in is not as crucial as the angle of a mirror
trying to relect the sun into a small collector. The electric
actuators I am familiar with have things like reticulating screw jack
mechanisms internally or gearing. Then of course the also have to be
connected in some way the device being moved- like links, bearings,
bolts, pins etc. This of course is also the case with hydraulic
actuators.
3. My main comment was the reliability of anything electrical.
Electric actuators have things like travel limit micros, and some even
have internal clutches and brakes. Also the electrical connections
often seem to become loose, corroded, arc pitted etc. Of course
hydraulics are not without their problems too- leaks etc. Although you
can usually find a hydraulic leak much easier than an electric leak.
The other issue is that you need some way to electrically power
electric actuators. So some of your project budget gets used to
provide extra electrical capacity. Of course we will still need some
electrical power to power a control circuit anyway but control systems
will use less power than driving several actuators. The hydraulic
system could be potentially operated with the fluid in the collector
which could be around 500 psi - ample to drive an actuator. The fluid
would not have to be wasted as the hydraulic return could be fed back
into the collector system input. Of course some generated heat energy
is lost. Of course when the steam engine electrical is functioning the
extra electrical capacity is not required, but you still need it to
get to that point before the system is up to temperature, speed etc.
To be completely fair this is also true that a hydraulic system wont
function either until adequate pressure is generated some how. Maybe
an electric pump- (extra expense, elec capacity required as well), an
accumulator possibly or even a head of water in an elevated storage
tank? However hydraulics require on less energy conversion step (all
conversions involve losses). Ie We get hydraulic pressure before
starting the steam engine and putting the generator online. That
conversion from heat to electricity is particularly inefficient, I
think 18% (ie 82% loss) then there is generator losses.
Thanks,
Milton.
These are all design issues and questions to be decided on.
> Seehttp://openfarmtech.org/index.php?title=Solar_Power_Generator_Distill...
> ranscript- Ocultar texto das mensagens anteriores -
>
> - Mostrar texto das mensagens anteriores -
Rick Thomas
Price wise, I can get an actuator with 18" of travel for £25.00
See http://www.maplin.co.uk/module.aspx?moduleno=100901
If I was buying in bulk I could probably get them cheaper.
They are specc'd at 36V but work fine at 12V
I played with some awhile age and the current draw was about 300mA
Accuracy wise they are designed to point a satellite dish at a particular
point in space consistently, so I guess they will be accurate enough. They
have an internal mechanical pulse generator (reed switch and magnet)
They are also designed to be stuck on the side of a house and forgotten
about.
For more ideas than you can shake a stick at, have a look at
http://www.redrok.com/main.htm but if you buy one of his trackers, he takes
forever to deliver.
Also have a look at http://www.ausra.com/ in particular the photographs of
the Liddell plant to see an elegant way to build a collector.
If you can get hold of a copy of the White Cliffs report, It makes
interesting reading as well.
See http://www.rossen.ch/solar/wcengine.html
I have been toying with various ideas for some while now, but as being based
in the UK, my problem is lack of usable sunshine.
Rick
Hi Rick,
Thanks,
Milton.
Rick Thomas
http://groups.google.com/group/solar-turbine?hl=en
Enjoy.
...
ozheliguy:
I didn't catch much of an introduction.
Do you have machining experience?
Did/Do you work on aeroplanes?
etc.?
-elliot
Ozheliguy
thanks very much. That is all good stuff.
Lister diesels- that is very interesting. I had some flash backs as I
was doing my apprentiship on Listers, and others, in a place a little
South of there around the time that report was written. Encouraging
for steam technology on a reasonably small scale.
I knew of Ausra, but had never been to their site. Yes again very good
to see that the technology seems quite feasable, atleast at that
scale. My question is what can we learn from their experience, that
might be applicable to this project.
Yes I have been to the Red Rock site before. As you say there is
certainly a volumous amount of information about a wide range of
related subjects. Yes I saw the trackers on the site previously.
Sounds like you have purchased one? How is it?
Indeed GBP 25 is quite reasonable for acutators. As for what things
are 'designed' to do, and how well they do it. Call me scepticle but
from my practical experience I can say that on the equipment I work on
the electric actuators rarely make their quoted service life.
Conversely the hydraulic actators rarely have to be change before
their quoted service life. I can say they are never as clean as
electric actuators and indeed often weep (slow small leak) from when
they are installed. As for precision by sheer fact of how they are
both constructed, a linear electric actuator can never match a
hydraulic actuators precision. Hydraulic actuators are a solid piece
of metal. The corresponding equavilent in an electric actuator has
gears, balls runnining in a groove etc. If you have one there grab the
body and pull the output end. I would be supprised if you dont get a
little clunk. Which in itself is normal and not a problem. However you
wont get this in a hydraulic actuator. I am certainly not bashing them
or dislike them. Indeed if they are chosen to be the way ahead good. I
am only saying that every option has cons, and putting forward a
possible alternative. This wheel, the small scale solar generator,
hasn't been invented yet. No one I know has done this on a small scale
reliably and cheaply enough yet. So yes we might have to reinvent some
old wheels or make them round enough to roll well atleast.
I will get a material costing together for some various options to put
together a hydraulic actuator, so apples can be compared with apples
when the time comes to make those descisions. I am pretty sure we can
do them for half that, but I wont shoot my mouth off just yet. Of
course we would still have to manufacture them, but that might be a
day to do the first one. Again I am shooting from the hip here.
Thanks,
Milton.
On 26 fev, 11:21, "Rick Thomas" <r...@wirecomms.com> wrote:
> Hi, well let's see.
>
> Price wise, I can get an actuator with 18" of travel for £25.00
> Seehttp://www.maplin.co.uk/module.aspx?moduleno=100901
>
> If I was buying in bulk I could probably get them cheaper.
>
> They are specc'd at 36V but work fine at 12V
> I played with some awhile age and the current draw was about 300mA
>
> Accuracy wise they are designed to point a satellite dish at a particular
> point in space consistently, so I guess they will be accurate enough. They
> have an internal mechanical pulse generator (reed switch and magnet)
>
> They are also designed to be stuck on the side of a house and forgotten
> about.
>
> For more ideas than you can shake a stick at, have a look athttp://www.redrok.com/main.htmbut if you buy one of his trackers, he takes
> forever to deliver.
>
> Also have a look athttp://www.ausra.com/in particular the photographs of
> the Liddell plant to see an elegant way to build a collector.
>
> If you can get hold of a copy of the White Cliffs report, It makes
> interesting reading as well.
> Seehttp://www.rossen.ch/solar/wcengine.html
> For more options, visit this group athttp://groups.google.com/group/solar-turbine?hl=en
Ozheliguy
machining- learned during my apprenticeship to an adequate level. I'm
certainly not an expert, and havent done much in recent years but I
can drive a lathe. I'm not scared, and will have a go. But I
definately have my limitations. Then I go and get better advice,
research or get somone better than me to do it.
Yes work on Helicopters supporting offshore oil and gas. Have worked
in the jungles and deserts of many different places in the past.
Certainly not as glamorous as it sounds, but keeps me off the streets.
Cheers.
On 26 fev, 14:38, "..." <offonoffoffon...@gmail.com> wrote:
> I am all for hydraulic over electric.
>
> ozheliguy:
>
> I didn't catch much of an introduction.
>
> Do you have machining experience?
> Did/Do you work on aeroplanes?
> etc.?
>
> -elliot
>
>
>
> On Fri, Feb 26, 2010 at 9:38 AM, Rick Thomas <r...@wirecomms.com> wrote:
> > I'm uploading some files that should be of interest to
> >http://groups.google.com/group/solar-turbine?hl=en
>
> > Enjoy.
>
> > Rick
>
> > -----Original Message-----
> > From: solar-...@googlegroups.com [mailto:
> > solar-...@googlegroups.com]
> > On Behalf Of Rick Thomas
> > Sent: 26 February 2010 14:21
> > To: solar-...@googlegroups.com
> > Subject: RE: [Solar Turbine] Re: Solar Concentrator Revival: Solar Tracking
>
> > Hi, well let's see.
>
> > Price wise, I can get an actuator with 18" of travel for £25.00
> > Seehttp://www.maplin.co.uk/module.aspx?moduleno=100901
>
> > If I was buying in bulk I could probably get them cheaper.
>
> > They are specc'd at 36V but work fine at 12V
> > I played with some awhile age and the current draw was about 300mA
>
> > Accuracy wise they are designed to point a satellite dish at a particular
> > point in space consistently, so I guess they will be accurate enough. They
> > have an internal mechanical pulse generator (reed switch and magnet)
>
> > They are also designed to be stuck on the side of a house and forgotten
> > about.
>
> > For more ideas than you can shake a stick at, have a look at
> >http://www.redrok.com/main.htmbut if you buy one of his trackers, he
> > takes
> > forever to deliver.
>
> > Also have a look athttp://www.ausra.com/in particular the photographs of
> > the Liddell plant to see an elegant way to build a collector.
>
> > If you can get hold of a copy of the White Cliffs report, It makes
> > interesting reading as well.
> > Seehttp://www.rossen.ch/solar/wcengine.html
> >http://openfarmtech.org/index.php?title=Solar_Power_Generator_Distill...
> > ranscript
>
> > --
> > To post to this group, send email to solar-...@googlegroups.com
> > For more options, visit this group at
>
> ...
>
> mais »- Ocultar texto das mensagens anteriores -
Ozheliguy
for your support. I am certainly not convinced myself. But I
definately think it is worth spending some more time looking into it
as a possibility. Maybe it has no legs and I'm barking up the wrong
tree, it wouldnt be the first time. I'm trying to keep an open mind.
Maybe I can get enough good information to convince highly scepticle
minds. Not many certainties in this end of the development curve.
That's what the system is about eh?
On 26 fev, 14:38, "..." <offonoffoffon...@gmail.com> wrote:
> I am all for hydraulic over electric.
>
> ozheliguy:
>
> I didn't catch much of an introduction.
>
> Do you have machining experience?
> Did/Do you work on aeroplanes?
> etc.?
>
> -elliot
>
>
>
> On Fri, Feb 26, 2010 at 9:38 AM, Rick Thomas <r...@wirecomms.com> wrote:
> > I'm uploading some files that should be of interest to
> >http://groups.google.com/group/solar-turbine?hl=en
>
> > Enjoy.
>
> > Rick
>
> > -----Original Message-----
> > From: solar-...@googlegroups.com [mailto:
> > solar-...@googlegroups.com]
> > On Behalf Of Rick Thomas
> > Sent: 26 February 2010 14:21
> > To: solar-...@googlegroups.com
> > Subject: RE: [Solar Turbine] Re: Solar Concentrator Revival: Solar Tracking
>
> > Hi, well let's see.
>
> > Price wise, I can get an actuator with 18" of travel for £25.00
> > Seehttp://www.maplin.co.uk/module.aspx?moduleno=100901
>
> > If I was buying in bulk I could probably get them cheaper.
>
> > They are specc'd at 36V but work fine at 12V
> > I played with some awhile age and the current draw was about 300mA
>
> > Accuracy wise they are designed to point a satellite dish at a particular
> > point in space consistently, so I guess they will be accurate enough. They
> > have an internal mechanical pulse generator (reed switch and magnet)
>
> > They are also designed to be stuck on the side of a house and forgotten
> > about.
>
> > For more ideas than you can shake a stick at, have a look at
> >http://www.redrok.com/main.htmbut if you buy one of his trackers, he
> > takes
> > forever to deliver.
>
> > Also have a look athttp://www.ausra.com/in particular the photographs of
> > the Liddell plant to see an elegant way to build a collector.
>
> > If you can get hold of a copy of the White Cliffs report, It makes
> > interesting reading as well.
> > Seehttp://www.rossen.ch/solar/wcengine.html
> >http://openfarmtech.org/index.php?title=Solar_Power_Generator_Distill...
> > ranscript
>
> > --
> > To post to this group, send email to solar-...@googlegroups.com
> > For more options, visit this group at
>
> ...
>
> mais »- Ocultar texto das mensagens anteriores -
Rick Thomas
dispute service in the end to get my money back. Absolutely no communication
from Duane C. Johnson at all, he didn't even respond to the PayPal dispute
process. I have heard that this is normal for him.
I have a few of the actuators, and they are all rock solid, no movement at
all. Which when you think about it, with the wind loading on a 1M dish must
be the case.
I have to admit that I prefer the ease of use of an electric actuator over
that of a hydraulic one, but that is what I am used to using.
I have been looking into small scale solar thermal power generation for a
couple of years now, and am coming to the conclusion that it is impractical
for a domestic implementation. Solar PV while much more expensive at the
moment is much more "Fit and Forget" than any thermal based generating
system.
The dangers of a boiler producing live steam coupled with constant
monitoring and the ongoing maintenance are too much for the average
consumer.
My ideal implementation, which I will never do unless I win the lottery, is
a largish solar generating plant used to power an electrolysis system to
split water into Hydrogen and Oxygen. Also to power an atmospheric Co2
scrubber.
Combine the Hydrogen and Co2 to create Methane using the Sabatier reaction.
The Methane can then be liquefied and used for all sorts of things, power
generation, transport etc... Build it on the edge of the Sahara, and ship
the liquefied Methane round the world.
Still it's all good fun and keeps me sane(ish)
Rick
Thanks,
Milton.
