Power producing low delta T state of the art?

[Pete_vb]

I figure this forum could be the best place to see how my new machine stacks up, so I thought I'd ask the experts:

I've just finished a small prototype heat engine:
-Dimensions: 6" by 1.5" by 1.5"
-.5 watts mechanical output at 50 degree C temperature difference
-30C minimum temperature difference to run.

I believe I can improve this to about:
-Same size
-5-10 watts at 40C
-20C minimum temperature difference to run

I could make something more powerful as well, but it would need to be larger.

I'd like any help comparing this to what already exists, and I'd like any suggestions for practical applications for this type of thing. It's not super cheap, but it's not terribly expensive either. What do you guys think- is this good/ useful, or? Any links to similar devices?

[SScandizzo]

Hi Pete,

I'd research both NASA and Phillips work to see how you stack up. Half a watt is quite an accomplishment at the scale you describe. I'm not sure if you meet the definition of a low delta T engine at 30C, though. I'll have to defer to someone else, but I believe at difference of less than 10C is usually accepted. Nonetheless, it sounds like you have built a fantastic engine- post pictures if you can!

-Stefan

[Pete_vb]

Thanks Stefan,

I've seen some of the NASA designs with much higher temperature differences- they look very nice. I'm not aware of anything they did in this temperature range, though- any info on that? Or any links to the Phillips effort, which from what I've read so far also looks like it's higher temperature difference? This 50C temp difference space seems pretty empty from what I've seen...

I'm afraid I'd prefer not to post pics just yet due to the fact that some of the features are probably patentable. It's not much to look at, however- pretty much and aluminum box with some plastic and a shaft coming out the end.

Regards,

-Pete

[andonrangelov]

Hi Pete,
can you give any updates after 10 years?

[Pete_vb]

Wow, I got an email on this, blast from the past.

I did make a second prototype that hit about 1 mechanical watt output from similar dimensions and delta T around the time I posted this. Not long after I shelved the work because I never found a great application for it. I keep my eyes open, but in some ways it's still a technology looking for an application- a terrible place to get to.

I co-founded a solar thermal company shortly after that (around 9 years ago). I'm CTO, we've grown to over 300 worldwide and we're currently building one of the largest solar fields in the world using a unique technology we developed. Thus I'm more than keeping busy. So busy that I'm not sure if I'll come back to a version of this at some point in the future. Perhaps no huge loss if there's no compelling need.

Thanks for asking- a trip down memory lane!

[andonrangelov]

Nice development.
Can you give link to your company web site? I wan to see what you are doing with solar thermal, because I am going to this line as a hobby.

[Pete_vb]

Sent via pm

[derwood]

Must be a top secret company. no link for the public to see.

[Pete_vb]

I just try to limit my online footprint where possible. That said... www.glasspoint.com

[cbstirling2]

What was so revolutionary about your Stirling engine? You had a year to patent that but that timeframe expired long ago.
So you might as well share the idea.
Post a picture, etc.

[Pete_vb]

What was so revolutionary about your Stirling engine? You had a year to patent that but that timeframe expired long ago.
So you might as well share the idea.
Post a picture, etc.

There is no time limit from date of invention until filing. You can file whenever you want, but under "first to file" rules you lose claim if either a) someone else files before you, or b) there is "public disclosure" of the invention beforehand. You're likely thinking of provisional patents- you have 1 year to convert a provisional patent into a final application or you lose the priority date secured by the provisional.

I'm not yet ready to limit options by disclosing details. I can however say that it is not a true sterling engine, it only functions like one. Rather than using gasses as a working fluid, however, it uses shape memory alloy. This imposes limits on the design such as theoretical efficiency and working temperature range. In trade you get a couple orders of magnitude higher power density for a given size and delta T along with the ability to self-start.

The best applications I found were pumps for cooling. If you're water cooling a computer CPU, for example, you could mount a small temperature driven pump to that CPU that would pump water faster the hotter the CPU got. You could do something similar for rooftop hot water heaters to circulate the water. In both cases you'd eliminate a temperature sensor, traditional pump, etc. Unfortunately that's all cheap and easy to do, so there does not appear to be a compelling need.

[harry56]

I recently created a Stirling engine software program which can be used to design a high-power Stirling engine. My blog post describes this in detail:


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