Scaled up solar Stirling

[Cherryman]

Hi all, came across this side and youtube vid.

Tamera - SolarVillage Testfield 2011 - YouTube

They have a large Stirling solar engine powering real stuff, a solar "village"

Operating temp as low as 100c to 200c !
Low RPM
1.5kW Electrical output
1.7 kW Mechanical output

It's a low RPM Stirling type engine, operating gas is normal unpressurized air. and they use either water or oil as a heat transfer medium.

They also incorporate some other solutions, as energy storage they use a large drum filled with small stone to store heated fluid. Later to be used on demand with the Stirling.

They even manage to use the same working fluid for cooking and other household equipment.

They use the sun, (even the greenhouse sun is fresnelled into heat) But i can see this also working on a small fireplace, burner !

It even seems doable as a DIY project if you have some welding skills.

Anyway, just to inform


Cheers


Not OU , but it is not often you see a Stirling engine doing actual work.

[Cherryman]

Here is another little shorter vid:

Sunvention Sunpulse System at Tamera - YouTube

I really like this low RPM upscaled Stirling.

By using a working fluid, you can place the Stirling away from the heat source.

So Sun in summer, and your home fireplace in winter

And your Stirling in a shack , the cellar or wherever you want.

[mnsman]

Nice find Cherryman. I've never built a sterling but I've imagined one attached to my device to extract heat loss and convert to useable electricity.

[mbrownn]

I must admit that I have considered building sterling engines from oil drums to be run directly from the sun or from tne output of aircon units but the output is too low to make it useful. by intensifying the heat such as in the video the output would be significantly bigger. Maybe it would be viable then.

[theremart]

Wow...

Is this open sourced? there is some great ideas here, and the sterling engine design looks to be very much out of the box thinking. I have not seen a piston that big before.

[redeagle]

Is this open sourced? there is some great ideas here, and the sterling engine design looks to be very much out of the box thinking. I have not seen a piston that big before.

I have seen the video it sounds great until you think about the cost. though there is practical application in remote areas I have been pondering something slightly more useful in a homeowners perspective.

If you have piston pump compressor and a compressed air motor driving 1:1 the motor is not likely to turn, but if you cool the intake air for the compressor and heat the cylinder for the motor. The air in the motor will expand causing the cooler air to be compressed into a temporary holding tank. Through application of principles known from stirling engines we know that once the temperature difference is great enough it will continue to run without recharging the initial pressure in the tank.

If and only if there is enough available torque to drive the heatpump required to created the temperature difference in the system, the unit could be made portable. with only the need to change the refrigerant based ambient temperature. It would offer some academic opportunity as an alternative to traditional stirling as at any given time the only outside mechanical input would need to be is an initial tank pressure and the refrigeration cycle. if there is a build up of pressure in the tank additional pistons could be driven for an increase in overall torque output.

Something to think about, but I have no idea on where to source affordable or at best free parts.

[Peter Lindemann]

Totally Awesome!

Hey Guys,

I've been thinking along these lines for a couple of years now. It started when I bought one of those "coffee cup" Stirling Engines and thought, why not make a bigger version?



Here is the basic layout of one of these Low Temperature Stirling Engines. The only difference between these and other Stirling Engines is the size differential between the displacer and the power piston.



That is pretty much what these guys have done! But, I agree with Redeagle here as when you start to think about their design, it has got to be pretty expensive. So I started trying to think of ways to make something like this, dirt cheap!

What I've come up with so far is a set of rotary displacers 180* apart. Each one could be made of a 55 gallon drum and a Styrofoam cylinder inside.



The two displacers would run a double sided piston that could be made of two of the bellows type foot pumps, one fully compressed while the other is fully expanded.



This set-up would eliminate almost all of the critical machine shop work the Sunvention system requires. Add a flywheel and a simple crank mechanism between the bellows and the rotary displacers and you are good to go.

If we bury the bottom half of the displacers in the ground for the cold side, and collect some solar energy on top for the hot side, it should run pretty well on a 100*F differential. It could also be run by pumping hot (solar heated) and cold (earth cooled) fluids into contract with the appropriate displacer locations. This way, hot fluids could be stored for night-time running, like the Sunvention film suggests.

Anyway, I think this could be the beginning of an open source "home power plant" that is affordable and within the "low tech" category we are all looking for.

More later,
Peter

[gene gene]

Rotary Displacers

Hi Peter,
Good to see activity here again. I too have been fascinated for many years by the Stirlings. I am always drawn to them at the old engine shows.

I live in the north woods of Wisconsin and have thought for years that these temperature differentials are available at nearly all times when needed. In the winter a wood stove or furnace in the home easily creates temps needed in comparison to out side temps. The colder it is the hotter we fire our stoves.

In the home where I now live we have a hydronic heating system and all radiators are located on out side walls below a window. If I was to raise the window and put a rotary displacer there. At the floor where the hot water comes up from the furnace I could easily create a loop to circulate the hot water around the hot side of the displacer, and the cold side being outside would only need to be finned.

For summer cooling I have a project I'm working on that probably doesn't belong in this thread, but may start a thread for it.

Regards, Gene

[redeagle]

Does anybody have enough knowledge about refrigeration cycles to know if the mechanical output of a stirling can mechanically power a heatpump with enough btu/hr to provided the thermal displacement? i'm curious if it's possible. if so I would really like to design and build a self charging compressed air system. understanding that the stirling system would shut down once the equalization pressure was reached.

Additional solar energy may be needed from time to time in the system. if could be worked out, then the system could be used to charge pressure tanks for high efficiency motor vehicles. Sort of a pipe dream I know, but the idea is over 100 years old and yet to be confirmed or busted.

[mbrownn]

The answer is yes, but its not easy, the other problem is practicality.

If we have an aircon operating at a cop of 10 attached to a stiring engine it would work, but lets look at the details.

For the aircon to work at such a high cop the temperature gradient between the hot and cold sides has to be small, thus the temperature gradient the stirling works on has to be small too. This means that the stirling would have to be very large to produce the power required. The stirling itself is about 27 to 30% efficient so now our COP would be in the range of 3. We also have to consider the losses in the ducting which would also reduce your COP further. This engine would have to be somewhere in the region of the size of a small house or garage to operate a 1hp aircon. Obviously such a large device would be prohibitively expensive for most people.

There are ways to mitigate this problem such as cooling the cold side of the stirling with a source of free cold water such as a stream, but I think you see the problem is that of size and cost. The excess power could be used for anything but in my example it would only be a few hundred watts.

Using a free source of heat and cooling such as in the original post has brought the system into the range of being practical in some cases, but as you can see it is still quite large and expensive. When you see the size of the collector (the greenhouse) you can see this isnt going to be so cheap. Mass production could reduce costs to some extent but we still have a size issue.

[VacuumEnergyMan]

Stirling Powering a Heat Pump

When I was in mechanical engineering at college, we built a stirling engine in the shop after reviewing and 'enhancing' previous designs. When it was all said and done, using a blow torch on the hot side, the thing barely turned. So, may not be practical for mechanically driving a heat pump compressor.
Anyways, my thoughts on compressing air from a heat source like the sun is, forget the stirling engine and have a compound-parabolic concentrator heat a water boiler from the sun. This could produce high pressure steam capable of driving a large area piston developing tremendous force according to F= P*A. This piston is directly linked to a smaller piston compressing air into a storage tank. The process reciprocates much like a stream engine. What do you think?

[rosehillworks]

When I was in mechanical engineering at college, we built a stirling engine in the shop after reviewing and 'enhancing' previous designs. When it was all said and done, using a blow torch on the hot
side, the thing barely turned. So, may not be practical for mechanically driving a heat pump compressor.
Anyways, my thoughts on compressing air from a heat source like the sun is, forget the stirling engine and have a compound-parabolic concentrator heat a water boiler from the sun. This could produce high pressure steam capable of driving a large area piston developing tremendous force according to F= P*A. This piston is directly linked to a smaller piston compressing air into a storage tank. The process reciprocates much like a stream engine. What do you think?

You could certainly do it that way with an air driven hydraulic booster pump. Refrigerant gas can easily be compressed the same way.