This idea is to use a looooong tube made of a non flexible material. This tube is painted black to absorb heat from the sun. Inside the tube there is water, and the end of the tube there is cylinder and a piston. It is water in the whole tube untill the piston, so there is no air inside.
When water is warmed up, it expands. From 277K to 373K the water expand its volume by 5%. That means if the tube is 10m long, the water will expand 50cm at 373K compared to 277K.
This is a force which is incredibly strong, because water is hardly compressable. The piston will face a force of about 50 atm. pressure if it is prevented to move inside the cylinder during the warmup of the water (It requires 50 atm. pressure to compress water 5%).
So how much energy can we expect to harness from a device like this?.

Say the surface of the cylinder is 100cm^2. The stroke is 50cm. The average pressure is 25 atm. The maximum energy output would be:
100cm^2 * 25kg * 9.81 * 0.5m = 12262 Joule. If we manage to heat and cool the water in 1 cycle pr. minute, we have a potential energy output of 735,7kWh.

We make a push-pull system, so we also can get the same force when the piston returns, so we get > 1.5MWh of energy.

What do you think?

Vidar

how much energy to heat the water and tube?
100 sq cm X 10 meters=100,000cc of water
100 degrees k rise in temp X 100,000cc=10 million callories=41868000joules
one cycle per minute is 204 watts
12262/60=204
input power is 700 thousand watts
workable in pricipal but nobody is ever going to make one for the power.
fritznien

I did read more about compressibility of water. It happens to decrease its volume by 1.8% at 40 MPa, or approx 400 bar.

So the numbers changes a bit...

There is 100 cm^2 piston. The force at 5% compression of volume is 1.09MN. The average is 545kN. Distance is 0.5m, so the energy out will be 272.5kJ. That is still not more that 4.5kW per minute...

However, these figures are not correct, because the compressibility decrease with higher temperature and pressure. It is not easy to predict the energy out vs energy in.

Some litterature here: http://en.wikipedia.org/wiki/Bulk_modulus

any way you cut it is going to have poor conversion.
solar pannels for sunlight and an old steam engine for plain heat will
do far far better.
fritznien

I think so too. I have been told that steam engines is one of the most efficient technologies for converting heat energy into mechanical work, and is far more efficient than gasoline and diesel engines, and even higher efficiency than electric motors - when taking the whole chain of energy conversion and transportation from the power plant, till the power outlet which charges the electric car into account.

What if all cars had a butane burner which ran a steam engine - converting 70% of the heat into mechanical work, instead of loosing 70% energy as heat from a gasoline engine? Or what if the heat loss from a gasoline engine could be recycled into mechanical work like they did with the Corsair fighter and old fishing boats. They injected water mist directly into the combustion chambre to increase the efficiency by 30% - they combined the efficiency of the steam engine, and the flexibility from a gasoline engine.

I remember the fishing boats left the harbor. You could hear the engine say "thud. thud, thud, thud, thud", but when the boats reached open sea, and the engine was hot, I heard the water injection which changed the sound; "thud, thud, thud, thud, thcknock, thcknock, thcknock, thcknock". Then the fishermen could stay at the sea for longer because the engine became more efficient.

The Corsair figheter used water injection to escape the enemy if the plane did not have enough power to fly faster.

This is off topic, but very interesting

Vidar

who tells you these things?
steam locomotives ran about 10% effiecient when we changed to diesels
coal fired power plants around 30%
marine diesels 50%
combined cycle gas turbies over 60%
water injection is used on gas engines as an intercooler, the effect is a cooler denser charge
that alows higher compression and more output from a given size engine and octane rating.
the only reason to use steam in a car is that it alows a wide range of fuels and fuel qualities.
remember carrnott rules.
fritznien

Probably someone who did not tellme the full story. I did reat about steam powered engines, and the steam turbine is the most efficient. I can read there is about 70% efficiency in a steam turbine. Therefor it is widely used in powerplants to create electricity.

Vidar

acording to wiki its 75%
but that iis steam to mechanical power.
when you consider the whole plant coal to eletricity its down in the low 30,s.
fritznien

When everything taken into account, no machine is very efficient.
You seem to know this stuff quite well, so I have a question for you:
A regular gasoline engine gets quite hot when it's not water-cooled. The temperature will rise to way more than 100 degrees celcius. Do you think this heat qould be used to make high pressure steam to run either a turbine- or a rotary (Wankel, G-rotor style) steam engine? Could this increase the engines efficiency?

I have in mind that if the temperature is too high in the engine, the gasoline/air mixdure will detonate rather than burn, so ignition and injection timing and temperature control would be quite neccessary.

What do you think?

Vidar

A gravity powered machine is almost 100% efficient.

This topic isn't about gravity powered machines, but you are close to right. A turbine in a powerplant based on water falls (using gravity and mass), will convert 90% + of the turbines kinetic energy into electricity. However, there are loss everywhere.

1 - This idea is to use a looooong tube made of a non flexible material.

2 - This tube is painted black to absorb heat from the sun.

3 - Inside the tube there is water

4 - at the end of the tube there is cylinder and a piston.

I love Rube Goldberg incantation puzzles, heheh.

Let add a few things that are already used to get it to workable.

Erect a long half-circle mirrored surface the length of the pipe,
suspend the pipe at the circles center focus apex.

Now you have what people are already using to make steam.

But, lets forget that for the moment and stick with your idea
of only using water's thermal expansion ratio instead
while still retaining the state of it in the liquid form.

If the tube is large,
and you place a very small piston at both ends of it.

The load on the piston resisting can be calculated into the concept
to prevent the conversion process into steam instead to meet your criteria.

I'm sure I need not clarify that a load must be available without fail,
or all your doing is making a simple water bomb.
(YouTube a vid of a hot water heater exploding for reference !)

so, apply sunshine,
amplify sun (mirrored trough),
absorb highest Infrared possible (black),
utilize predicted coefficient of expansion for work (pistons),
repeat and rinse...

The last one is a pun actually.

Once you have said pipe and water heated/expanded,
your at the end of the recoverable work cycle now.

rinse and repeat actually translates to blocking the sun from the collector,
and cooling the work medium for another cycle.

I see this as the sticky sticking point.



Place a second larger piece of pipe around the existing first pipe,
let the outer pipe me a half circle only that has two states,
directly on top not blocking any of the sun from the collector,
and of course being on the bottom blocking the sun from the collector.

Now add a water bath from the top of the pipe
that is collected at the bottom of the pipe by the "Blocker",
and you have kept your blocker cool and have quenched the collector.

Not to mention recovered the cooling medium
which oddly enough is also the power medium.



Good start, but you need more, water is resistant to thermal change.

Don't believe me, what happens when you put a red hot metal item
into a small amount of water, it is quenched of more heat than ignorable !

Just by ratio alone the water should boil instead of course.

But it doesn't, does it.



The very medium that powers this idea of capturing expansion,
is capable of storing such a huge amount of energy that the
amount of energy to cool it outweights what you captured...

The only thing that quenches a small amount of hot water,
is a substantially larger volume of water in contact with it.

Note how I didn't say heat-exchanger,
and oxymoron in my book so far !



If you add a full factor (squared factor) of water by volume,
and you purge the heated water into that larger volume of water,
you almost instantly disperse the collected retained heat.

Water is amazing, it can incur amazing heat and absorb it
without changing It's state into the next state (gaseous in this case).

But in the same vain,
it can redistribute the heat amoungst It's "Brothers" almost instantly.

That transfer travels fasters than fart's aroma 



So, to recap:

Trough to focalize available input energy,
black pipe to absorb at most efficiency,
blocker to swing into place at end of cycle,
water to cool blocker and pipe,
100% (by volume) exchange of water
from the colector into a larger water volume.



The amount of recovered "Work" needs to pump
the volume of the heat collector pipe in full,
and quench the blocker and collector pipe,
and of course cycle to two-state blocker.

What's left over is yours to use somehow.



Did I get anything wrong ?


.