want to build a solar dish stirling engine system

[mpm]

Hello Respected members of this forum,
I have been trying to build a solar run stirling engine from past few months,but it is not possible on my path. I have fabricated a solar concentrating parabolic dish and the mounting for the engine also, but unfortunately the engine is still not fabricated.
Initially, i tried using a toy stirling engine which is run using a alcohol burner, but it didn't work with my solar engine setup :wall:
so, please help me out. I need it for my engineering project urgently!

thanks,
mpm

 

[ignator]

While searching for Stirling engines, this old post came up, and zero replies.
The OP only posted once on this forum.
My first attempt at a Stirling was from the attached pdf article from a 1960s Popular Science magazine. I never did finish it, as I was in HS and only had use of a lathe for too short of time, and beyond my skills at that time.
Hope MPM gets an email from this post.
Note this engine has a problem with the displacer connection to the crank, as there is no mechanism to float the displacer shaft, so the shaft has to bend.

 

[Entropy455]

The solar flux at the surface of the Earth on a bright sunny day averages about 1000 watts per square meter. Significantly less when it's overcast, or if the sun is low on the horizon.

For comparison, a typical candle flame is 80 watts.

Not sure how much heat input your engine requires, but if it's more than a few candle-flame's worth, you'll need a pretty large solar dish/reflector.

 

[ignator]

The solar flux at the surface of the Earth on a bright sunny day averages about 1000 watts per square meter. Significantly less when it's overcast, or if the sun is low on the horizon.

For comparison, a typical candle flame is 80 watts.

Not sure how much heat input your engine requires, but if it's more than a few candle-flame's worth, you'll need a pretty large solar dish/reflector.

It certainly is not a LDT Stirling, but they published it. I still have the unfinished part laying in a tool box in the shop. I also started one that was in a book that is a reproduction of an antique Stirling that spins a cooling fan. I ran into trouble with the crank shaft. I could not get the two crank throws (one for the power piston, one for the displacer) to run true. After 2 attempts at trying to precision drill and ream, and have it run wanky, I put it aside.
I've always like the idea of Stirling's, I know their Carnot efficiency is poor. A dream that will never happen would be one that produces 1Kw at 40 degree differential. One end of the heat source would be the ground (earth) the other either capture sunlight, or radiate to space. A double displacer, double acting power cylinder. It would probably be a 2 meter piston diameter to get enough pressure difference for the force needed to make 1Kw. The engine body would be stamped metal like a transformer/motor laminations (thickness unknown) with insulating stampings (fiberglass printed wiring board type material), so there could be a thermal distribution across the engine that would act as a regenerator. The displacer would probably not be round but a surface with V grooves that would have a mirror copy in the engine case. The idea to increase the surface area of this heat exchanger. The stamped laminations would have long truss rods to clamp it tight so it can be pressurized. ......A pipe dream.

 

[ignator]

Someone spent the time to model the Popular Science plans;


And it was this post the indicated a design issue;


Here is the engine running on a flame;

 

[Cogsy]

From memory the Carnot efficiency of Stirling engines is actually quite good - better than steam and much better than I.C., but the problem is the sheer size of engine required to make usable power. I've seen a video of a 5 Hp (maybe 5Kw?) engine running on lpg and it was the size of 2 large wheelbarrows. Not ideal for a lawnmower...

 

[mnay]

One of my local home shop friends bought the kit advertised in Popular Science. He still has it and the small reflector that came with it and it runs well.

 

[mnay]

One of my local home shop friends bought the kit advertised in Popular Science. He still has it and the small reflector that came with it and it runs well.

Another friend took a small satellite dish and lined it with mirror tiles. It would start his stirling in a few seconds or start a piece of wood on fire in 5 seconds or less. He was afraid that it would melt the hot end cylinder

 

[olympic]

Here's my Sun Motor, a commercial offering from Phoenix, Arizona way back when, now available in modifed form from PM Research.

I ran it for the video in a Canadian February; the sunlight was still more than sufficient to run it.

 

[ignator]

From memory the Carnot efficiency of Stirling engines is actually quite good - better than steam and much better than I.C., but the problem is the sheer size of engine required to make usable power. I've seen a video of a 5 Hp (maybe 5Kw?) engine running on lpg and it was the size of 2 large wheelbarrows. Not ideal for a lawnmower...

That depends on the temperature difference. But you know, if you have the cold junction of the engine at absolute zero, the engine is 100% efficient. Understand that that is not realizable on our planet surface, but this is made use of in deep space power systems, as well Stirling engines, with uranium or some other fission heat source.
With low differential temperature engines, they are very low efficiencies.

 

[Cogsy]

That depends on the temperature difference. But you know, if you have the cold junction of the engine at absolute zero, the engine is 100% efficient. Understand that that is not realizable on our planet surface, but this is made use of in deep space power systems, as well Stirling engines, with uranium or some other fission heat source.
With low differential temperature engines, they are very low efficiencies.

Absolutely I agree the temperature differential is of vital importance. The engine I was describing above was LPG powered so had a large Tc/Th difference and using a suitable parabolic mirror should generate quite a high difference as well. LTD stirlings do indeed have very poor Carnot efficiencies, as do Carnot engines themselves. Even using the theoretical maximum efficiency values with a 40 degree differential, the solar collector would be quite large indeed.

 

[Naiveambition]

I seen one of these run at the craftmanship museum in Carlsbad California, and I do believe their is also a small description on the website, that may be of some help. Very neat idea but, of note is that it was running inside off of the sunlight thru the window glass. I'm sure it really kicks when in full noon sun. If I remember there was a fellow that built a sun dial clock that ran on the same principles.
Good luck with your build