# Re: Feasible new approach to solar power use? - Metal bars thermal - Page 7

Posted by oksid on January 16, 2009, 9:30 am

azuredu wrote:

Ok let's go. I'm playing.

The energy in water is thermal.
The energy that you want is mechanical (expansion).

If you want to convert the all thermal energy to mechanical energy,
then, after the expansion has been done, the water must have been cooled
to its initial temperature.

Expansion doesn't cool down the water significantly (thermal energy is
still present in the water), so mechanical energy is not significant.

Sentence (1) and (2) are right.
Sentence (3) is wrong. Expansion energy is not high.

Posted by Mike Hennessey on January 16, 2009, 1:33 pm

The expansion doesn't cool the water down...The temperature
remains hot until the following night when the tank cools down
due to the lack of solar energy.  The ratchet mechanism holds
the load at it's highest point while the piston lowers due to the
cooling water.  The next day the solar energy re-heats the water
causing the piston to rise and lift the load even higher.

The tank can be large giving a significant amount of volume
increase.  The volume of the piston can be small giving a
significant amount of lift.

I have not run the numbers so this is just brainstorming at
this point.   Still....it's fun to do in my spare time.

Mike

Posted by Bruce Richmond on January 17, 2009, 8:15 pm

As has been pointed out elsewhere water is not totally
incompressible.  There are limits, but it wouldn't be difficult to
work within them.  The main problem is that the energy recovered
wouldn't be enough to justify the expense of the equipment.

To put some numbers too it let's take a weight of 66 tons, about the
size of a train locomotive maybe.  A 12" diameter piston has an area
of 113 sq. in. so it would only take 1168 lb/sq. in, to lift it, but
it would be rather precarious balancing 100 feet up on a one foot
shaft.  It would probably be better to use a platform supported by
four 6" shafts which would provide the same piston area.  I think you
still might want some additonal structure to keep it from tipping
over.

To raise the load 100 feet the water will need to expand 113 X 1200 =
135,600 cu. in. or 78 cubic feet.  I'll leave it to you to figure out
the volume of the tank required.  The tank will need a large surface
area to absorb the sun light, but must be strong enough not to buldge
out as the pressure builds.  Any give in the tank would reduce the
movement of the piston.

Next we need a way of converting the stored energy into a form that we
can use to produce useful work.  Let's just say a hydraulic motor
driving a generator.

Raising our 66 ton load 100 feet takes 13,200,000 ft lbs of energy.
One horsepower is 33,000 ft lbs per minute or 1,980,000 ft lbs per
hour.  So at 100% efficiency we could recover 6.7 hp hrs or about a
bit under 5 KW hrs with a market value of less than one dollar.

BTW, "perpetual motion" is usually reserved for devices that do not
require the input of energy.  A hydroelectric generator may run
continuously for years but is not considered a "perpetual motion"
machine.

Bruce

Posted by azuredu on January 17, 2009, 8:57 pm
On Jan 17, 9:15 pm, Bruce Richmond

Perpetual motion can be easily constructed if a device is able to
output more energy than the energy input.

Of course, the mine is just for play, and the answer is given by David
Williams.

Posted by azuredu on January 16, 2009, 6:47 am
On Jan 15, 11:24 pm, david.willi...@bayman.org (David Williams) wrote:

Thanks for your advises. But don't worry: if we produce, that will be
because somebody else placing orders. And these guys won't send money
without knowing what they do.

There are a few people in the world who have the feeling. And of
course things will be thouroughly tested before appearing in the
market.

It has taken me sometime to figure out what you mean there. You must
have taken somebody else's words for mine.

My collector can be placed at whatever angle, orientation and
inclination facing the sun, and it automatically starts tracking to
micrometer level precision. Taking a flat east-west installation and
trying to retrack only once every few days is a "poor mans tracking"
having nothing to do with mine. And being a mathematician, I of course
know the angle calculations.

I even tested my collector on a kind of (slowly) moving support. As
long as the support does not move too fast, the collector always
points to the sun. That's why I say that my collectors can be floating-
installed on a water surface.