Is anyone working on LTD SunPulse-style engines?

[7spoons]

Hi guys,

I'm looking for some homestead-appropriate stirling engine design that can be built with low-to-moderate skills and budget. SunPulse naturally grabbed my interest since they claim to not use advanced materials and yet reasonable efficiency. However, it appears that the team stopped all work on the engine - their web site is down and I couldn't find any recent news about them. So, does anyone know what's the status of original SunPulse team? Also, has anyone tried to make an engine based on their design? It looks like there may be enough information on youtube and in the patent to build something similar...

Thanks for any thoughts you can share!
-- spoons

[danalinscott]

I too considered the SP design but decided the equipment and skills required to fabricate it put it out of the DIY range for most people. I have the skills and equipment to make one...but most people do not. Having owned a prototyping business in the past I also estimated it's per kW cost to be awfully high. When I translated the cost of the SP engine/generator, solar heat collectors, heat storage, etc it was several times more than the cost of an equivalent PV array and battery.

I liked the idea of using stored heat in place of a battery to provide 24hour electrial production but after running the numbers decided a low cost 1kW unit combined with a small "surge compensating" battery was several times less expensive and much easier to fabricate.

I am currently attempting to adapt an existing working Beta engine design that actually seems to have the potential you describe. It will be open source all the way from development to "production". The main goal is to only have a few small parts which are not easily procured "off the shelf" or produced with very simple skills and inexpensive low tech tools.

I am not discouraging you from moving forward on a SP clone. In fact I may be able to help.
I would encourage you to post all the info you have gathered so far. If I have any info you do not I will add to that knowledge base.

I developed a pretty good ability to "ball park" the cost of prototypes and have an extensive catalog of materials and their sources which may also prove helpful if you decide to proceed. Do you have the skills required and tools to fabricate the SP engine/generator if you somehow obtained a "blueprint" of one?

[7spoons]

My background is in computers and metal fabrication is more of a hobby. I weld and have access to a basic machine shop though no EDM or CNC for the moment. My initial impulse was to make a "toy" SP-style first, no more than a foot diameter, learn what I can and see if it inspires enough confidence for a bigger unit. If I had blueprints, I'd probably attempt something similar based on them. As you mention, fabrication of 1kW or even 500W machine has to be fairly expensive so I'll only commit to it if I have reasonable chance of success. Out of curiosity, would you mind sharing your estimates for fabricated SP-500?

On the other hand, your project sounds intriguing as well! Is there a place I can learn more about it? What's your progress so far? It sounds pretty well aligned with my needs, maybe we can find a way to collaborate?

[amusesmile]

I too considered the SP design but decided the equipment and skills required to fabricate it put it out of the DIY range for most people. I have the skills and equipment to make one...but most people do not. Having owned a prototyping business in the past I also estimated it's per kW cost to be awfully high. When I translated the cost of the SP engine/generator, solar heat collectors, heat storage, etc it was several times more than the cost of an equivalent PV array and battery.

I liked the idea of using stored heat in place of a battery to provide 24hour electrial production but after running the numbers decided a low cost 1kW unit combined with a small "surge compensating" battery was several times less expensive and much easier to fabricate.

I am currently attempting to adapt an existing working Beta engine design that actually seems to have the potential you describe. It will be open source all the way from development to "production". The main goal is to only have a few small parts which are not easily procured "off the shelf" or produced with very simple skills and inexpensive low tech tools.

I am not discouraging you from moving forward on a SP clone. In fact I may be able to help.
I would encourage you to post all the info you have gathered so far. If I have any info you do not I will add to that knowledge base.

I developed a pretty good ability to "ball park" the cost of prototypes and have an extensive catalog of materials and their sources which may also prove helpful if you decide to proceed. Do you have the skills required and tools to fabricate the SP engine/generator if you somehow obtained a "blueprint" of one?

I've been interested in the SunPulse concept ever since I saw it a number of years ago and I just can't seem to let go of the idea of trying to recreate it or spend enough time to understand why it won't work (i.e. to be competitive with PV but longer lasting and with less energy invested to manufacture).

If I were able to get plans to make a solar powered Stirling engine I think I could fabricate one or find someone who could. I also wouldn't mind spending the money to make it happen as a pet project. Would you be able to forward any information or calculations you've done on this project and/or provide more info? What design do you think is being used by the SunPulse team? Is that a beta configuration? I was under the impression that most LTD Stirling engines are Gamma or Gamma derived. Maybe I'm incorrect.

Knowledge background: software engineer interested in Stirling Engines. I've read "Low Temperature Differential Stirling Engines" by James Senft and I'm about half way through "The Next Great Thing" about William Beale and Sunpower. I've read Senft's paper "Development of a Direct Solar Stirling Engine: Mechanical Energy for Developing Countries" where he ends by claiming that it shouldn't be overly difficult to create a 200-300 Watt direct solar Stirling Engine without an exotic design (more or less).

[staska]

Its all depend on targed "market" non concentrated solar stirling is just to big to ship.

[Tom Booth]

As far as the design of the Sun Pulse, it seems to me that there is a rather large, and probably unnecessary structure or metal framing that has to be lifted continuously. How many pounds is that?

https://youtu.be/SMMELH7CSNE

I'm not certain about the internals, but presumably there is also a large displacer of some sort also being lifted?

Anyway, I'm very interested in power producing LTD type Stirling's, but what has caught my attention is a Stirling design by TK Motors that does not require all this heavy lifting.

This TK Motors design uses a diaphragm that oscillates the working gas through a large stationary regenerator.

For a small "tin can" type engine, this design appears to result in a quite impressive, powerful running engine.

This is not LTD however, but seems quite efficient running on just a tea candle so perhaps this design could be adapted to a low temperature difference engine.

Video showing internal design:

(Note that the large internal can/regenerator is held stationary, is not lifted like a displacer, instead a diaphragm serves to move the air through the steel wool regenerator)

https://youtu.be/iFXiaO8iwhk

https://youtu.be/dJCG9r15kuM

Another internal view of a similar engine:

https://youtu.be/CXsFNPmjluo


And the results:

https://youtu.be/up8wS3D4mwc

https://youtu.be/r9lYsW0Df08

A goal of mine is to adapt this design to an LTD -Sun Pulse type/size engine, which I'm assuming might involve simply increasing the heat exchanger surface area with a wider LTD type chamber.

That is the direction I'm working in at the moment anyway.