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Concentrating Solar Energy on Evacuated Thermal Tubes With Stationary Mirror - Page 3

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Posted by Free Energy on December 27, 2006, 1:18 am
 
Hi Rob,
OK, You are just not seeing this for some reason.
I think you are trying to make this more complex than it really is.

The greater precision IS required at larger concentrations to keep the
energy collected at all times throughout the day tightly focused on the
collector tube (imaging or not!).
For all practical purposes the spacing CAN certainly be extended
indefinitely between the troughs, but WHY would you want to do that
since your frame would just be filled with useless gaps, since the
closest spacing yields more energy per unit area!
The sun has parallel rays, that are only slightly off parallel because
the sun even at 93,000,000 million miles away,  is 0.5 degrees (30
minutes of arc) of arc across, because the sun is huge!
 That is the fundamental limiting factor of how high we can concentrate
the sun's energy even if the reflector is perfect. That limit is
nearly 500 suns!
As a practical matter, the combination of a slightly imperfect compound
parabola curve AND the fact that the suns rays are not all perfectly
parallel since they emerge  at different points of the solar disk
rather than a single point combines to limit the concentration ratio to
amount 36-50 suns using a simple compound solar parabola
Remember.

You do not need ANY space between the collector troughs to allow for
tracking, BECAUSE there is need to track at all, each day.

The only adjustment needed is a slight seasonal tilt adjustment, about
once every two months at the solstice, and every moth around the
equinox.
Let me ask you to do a thought experiment.
If you quadruple  the size of the collector in two dimensions and
quadruple  the length of the collector tube in length, and you have
enough added precision in the curvature WITHOUT CHANGING THE SHAPE of
the compound parabola  (not proportionately deeper or shallower, but
proportionately exactly the same shape) (and ignoring reflective
losses) how can the solar absorber tube NOT collect 16 times the Solar
Thermal energy?
This has absolutely nothing to do with the acceptance angle, or the
space between the troughs!
The troughs are horizontal, and the co-focal compound parabolic
geometry includes the collector tubes at the co-focus and collected
soar energy at the same co-focus all day long.
There is no need to move the reflectors at all during the Sol. The
seasonal adjustments are occasional not diurnal.

2006
Patrick Ward
26 Dec. 2006

With Best regards
FREE ENERGY
Patrick Ward
Richmond VA
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Rob Dekker wrote:


Posted by Jeff on December 27, 2006, 11:53 am
 
Free Energy wrote:


Are you copyrighting a Usenet post?

   Jeff


be extended indefinitely.

reflector,

collector.

make the spacing

the troughs would get very deep).

collector,

what you could

capturing

generate higher temps in the collector.

months ago,


Posted by Free Energy on December 27, 2006, 8:05 pm
 
Jeff wrote:

Patrick Ward
27 Dec. 2006

With Best regards
FREE ENERGY
Patrick Ward
Richmond VA
fossilfreedomATyahoo.com                fossilfreedom@yahoo.com
fossilfreedomATyahoogroups.com     fossilfreedom@yahoogroups.com
biogasolineATyahoo.com                      biogasoline@yahoo.com
biogasolineATyahoogroups.com           biogasoline@yahoogroups.com
fossilfreedomATgmail.com                 fossilfreedom@gmail.com

http://www.fossilfreedom.com


Posted by Rob Dekker on December 31, 2006, 1:49 am
 
[....]

degrees is steep, but if the focal point is nearer the

the collection point?

Look at Fig 1 of the patent. It shows theta-max. Its the vertical angle of the
line that runs from the edge of the reflector to the
top of the collector.
More importantly, it is the angle under which rays can enter the aparture of the
devide and still always hit the collector.

There is no focal point in this device. Parallel rays coming into the aparture
exactly vertical (theta = 0deg) will 'lighten' the
entire collector, but with more intensity on the back of the collector. If you
increase the angle (theta) of these rays (as the sun
moves up and down during the day) then these spots of intensity will move
towards the front. Only when the angle exceeds theta-max
is when the intensity spots will drop off the collector, and are reflected out
of the device, causing suddenly loss of energy in the
collector.

You cannot make the collector smaller than what is required to keep the
intensity spots enough space to 'walk' the collector when
incoming ray angle changes.
That's where theta-max comes in and how it determines the concentration factor.


from the reference axis (the vertical line) for

larger angle will be reflected back out of the device !

to be very small (deep trough) which also means that

hand, if you choose theta-max to be much larger (up

much of any concentration either.

6deg. That is a very deep trough, and it would need

rising/falling sun.

even than system requires semi-annual adjustments.


Posted by Rob Dekker on January 2, 2007, 2:44 am
 
Just got a brain wave.

If, instead of using a trough, we use a round dish, with the (cross) shape of
Winston's compound parabola, then the collector can
change from a pipe with some diameter d to a small piece of pipe with length d,
sticking up, right in the center of the dish. This
would enhance the solar concentration BIG time, and I would not be surprized if
we can get to 30 sol or more.

The nice thing about this dish (as opposed to a normal parabolic dish, is that
it has a small focal area which does not change much
with the position of the sun, rather than a single focal point which moves
around if the position of the sun changes. So we could
make a parabolic concentrator without much need for solar tracking...

Wonder if anyone thought of this before.

Rob



I am not trying to place multiple tubes in a single collector trough.
Nor do I need to to get the needed concentration.
If you need still more power, you can just use multiple tube/reflector
troughs spaced several times farther apart.
You can get several times increase, with a single tube, if the aperture
area is several times larger than the total tadsorber tube area.
Think of it, like the whole reflector getting larger relative to the
absorber tube's constant  diameter while the tube remains at the
focus, and you will get the idea.
I am also using a vacuum thermos type EVAC tube which gets a lot hotter
than the copper tube used in the link.
That's a good link, however.
 There are some reflective losses, but you can just increase the
aperture area to compensate.
The PRECISION of the reflector, does have to increase as the reflector
sizes grows relative to the collector tube, however.
At some large concentration ratio, the thermal movements from expansion
and contraction may begin to exceed that precision limit.
So your not going to get up to 500 suns like a good tracker can.
However, concentrating to several suns or tens of suns is indeed
possible.
By the way, despite the puffery in that link, the old Winston patent
dates to 1977, so the Winston Compound parabola Solar Collector is now
squarely in the public domain.

2006
Patrick Ward
19 Dec. 2006

With Best regards
FREE ENERGY
Patrick Ward
Richmond VA
fossilfreedomATyahoo.com                fossilfreedom@yahoo.com
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http://www.fossilfreedom.com



normal spacing ?

thus the acceptance angle increasingly smaller.

over....

:http://www.solargenix.com/pdf/Technicalmanual.pdf

time I try it!

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