Posted by azuredu on January 9, 2009, 4:05 pm
On Jan 9, 9:10 pm, david.willi...@bayman.org (David Williams) wrote:
> The expansion of a metal bar can produce an enormous force, but it moves
> only a tiny distance. In order to use this effect for most practical
> purposes, you'd have to use some sort of gear or lever system to increase
> the distance at the expense of the force. This would make the machine more
> complex and expensive.
No, the problem is not here. It is the difference between force and
energy.
Once expanded, the bar stops moving, and there is no longer energy
output until the next day. Unless you cool it down, but that'll
consume more energy than you get.
Posted by Father Haskell on January 9, 2009, 6:14 pm
On Jan 9, 3:10 pm, david.willi...@bayman.org (David Williams) wrote:
> On 01/09/2009 8:27 AM, fkoh...@yahoo.com wrote to All:
> -> Basically, I don’t know if anyone knows anything about the use of
> -> solar energy to heat up metal bars (a metal bar being used as a
> -> thermal collector in a parabolic trough) and then use the metal linear
> -> thermal expansion to generate energy. Due to the sluggish linear
> -> expansion of a metal bar (movement) into a direction, I thought
> -> something like using this small movement each day to lift up heavy
> -> loads cumulatively until a certain height (several ways to do it, with
> -> cables connected to a ratchet wheel mechanism for instance -- I didn’t
> -> figured out the better mechanism to be used with the metal bar)
> ->
> -> Fabiano Kohler Silva
> -> Brazil
> The expansion of a metal bar can produce an enormous force, but it moves
> only a tiny distance. In order to use this effect for most practical
> purposes, you'd have to use some sort of gear or lever system to increase
> the distance at the expense of the force. This would make the machine more
> complex and expensive.
Try either nitinol springs or bimetallic strips, same as used in
thermostats. The coiled bimetallic sensor strip used in cheap
outdoor dial thermometers can move the tip of the needle
several inches in response to a 20 degree temerature change.
Posted by Father Haskell on January 10, 2009, 6:11 pm
On Jan 9, 10:57 pm, david.willi...@bayman.org (David Williams) wrote:
> -> Try either nitinol springs or bimetallic strips, same as used in
> -> thermostats. The coiled bimetallic sensor strip used in cheap
> -> outdoor dial thermometers can move the tip of the needle
> -> several inches in response to a 20 degree temerature change.
> That's true. But the springs are very flexible. They can't exert much
> force.
Use several.
Check these:
http://www.imagesco.com/articles/heatengine/HeatEngine.html
Posted by FKohler on January 11, 2009, 6:43 pm
> On Jan 9, 10:57 pm, david.willi...@bayman.org (David Williams) wrote:
> > -> Try either nitinol springs or bimetallic strips, same as used in
> > -> thermostats. The coiled bimetallic sensor strip used in cheap
> > -> outdoor dial thermometers can move the tip of the needle
> > -> several inches in response to a 20 degree temerature change.
> > That's true. But the springs are very flexible. They can't exert much
> > force.
> Use several.
> Check these:http://www.imagesco.com/articles/heatengine/HeatEngine.html
Thank you all for the ideas and critics as well.
Well, in fact, the tiny distance is true. Thats the issue, with the
tradeoff of the enormous force. I was thinking of heating up an
aluminium bar of 10m (thorugh parabolic solar concentrator). Throwing
some figures as an example, if we heat up 300o C (feasible?) we would
have a final expansion of roughly 7cm.
7cm to continuosly turn a simple ratchet wheel day by day (instead of
any gear mechanism) to lift some heavy load (as an "arcaic" but cheap
way to accumulate potential energy until the object is released down).
Of course, depending on the target height it would take 5, 15, 30 days
or more, but having several devices running at the same time (reducing
overall costs as well due to scale) would generate energy in a more
stable and constant output....
In fact, I thought somthin really simple because of the cost of the
whole system, but innefficiency is part of the game as well: steam has
its own innefficy (and still the key source of energy generation...),
as well as stirling, etc. However, dont you think guys this is much
more a matter of total cost x energy generated than efficiency?
Again, thank you all for this discussion. Its awesome to be discussing
such topics (solar energy) and reading different ideas and experiences
in a regular basis, in this group
Best regards
Posted by Mauried on January 12, 2009, 1:07 am
wrote:
>> On Jan 9, 10:57 pm, david.willi...@bayman.org (David Williams) wrote:
>>
>> > -> Try either nitinol springs or bimetallic strips, same as used in
>> > -> thermostats. The coiled bimetallic sensor strip used in cheap
>> > -> outdoor dial thermometers can move the tip of the needle
>> > -> several inches in response to a 20 degree temerature change.
>>
>> > That's true. But the springs are very flexible. They can't exert much
>> > force.
>>
>> Use several.
>>
>> Check these:http://www.imagesco.com/articles/heatengine/HeatEngine.html
>Thank you all for the ideas and critics as well.
>Well, in fact, the tiny distance is true. Thats the issue, with the
>tradeoff of the enormous force. I was thinking of heating up an
>aluminium bar of 10m (thorugh parabolic solar concentrator). Throwing
>some figures as an example, if we heat up 300o C (feasible?) we would
>have a final expansion of roughly 7cm.
>7cm to continuosly turn a simple ratchet wheel day by day (instead of
>any gear mechanism) to lift some heavy load (as an "arcaic" but cheap
>way to accumulate potential energy until the object is released down).
>Of course, depending on the target height it would take 5, 15, 30 days
>or more, but having several devices running at the same time (reducing
>overall costs as well due to scale) would generate energy in a more
>stable and constant output....
>In fact, I thought somthin really simple because of the cost of the
>whole system, but innefficiency is part of the game as well: steam has
>its own innefficy (and still the key source of energy generation...),
>as well as stirling, etc. However, dont you think guys this is much
>more a matter of total cost x energy generated than efficiency?
>Again, thank you all for this discussion. Its awesome to be discussing
>such topics (solar energy) and reading different ideas and experiences
>in a regular basis, in this group
>Best regards
Id start at looking at how much energy is needed to make your
aluminium bar in the first place , and whether you will ever recover
that energy in your lifetime, by expanding and contracting the bar.
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> only a tiny distance. In order to use this effect for most practical
> purposes, you'd have to use some sort of gear or lever system to increase
> the distance at the expense of the force. This would make the machine more
> complex and expensive.