Liquid Heating/Cooling of Hot/Cold Alpha Stirling Engine Cylinders?

[skyofcolorado]

I would love to hear the opinions of those on this site.

Sure to be an unpopular opinon, but two sources of running water calls for a hydro turbine rather than a stirling with a relatively small delta-t.

Depends on whether it's being done for the edification of building the LTD engine, or for an actual power need. Seems like a simple LTD gamma design (like a big coffee cup stirling) could work and the 10-20C delta is more than enough to get a few watts out of it. Not much more though. Either way, any amount of 24/7 power generation is incredibly useful.

...using either vacuum-sealed hot water tubes to increase the temperature of the hot side, and/or some sort of evaporative cooling solution to further cool the cold side.

Use of evacuated tubes to heat the water is just solar PV with extra steps and losses along the way if electricity is the end goal.

[dj4hill]

Great - thanks for the answer @skyofcolorado.

Further up the main stream, there are areas with a much greater gradient. I have looked at a setup such as this and seems 800 to 1200 watts is feasible for quite a reasonable price.

https://www.powerspout.com/

The Hydro location is further from the dwelling, so that is a negative.

However, if this is simply a better, more feasible and cost-effective to go for micro-turbine, then I should indeed go that route.

Thansk for the answer!

Cheers,
David

[Tom Booth]

...
I have a property that contains:
(a) A free-running stream,... the water is quite cool - let's say 15oC-20oC average
(b) A free-running natural spring,... let's say 25oC average.
(c) an existing large metal shed. .
...leveraging the heat from the sun and the roof of the shed. I assume it would be quite feasible to add at least 10oC but probably more than 20oC to the warmer stream.

The climate is subtropical... the sun shines most days of the year.
...
I would love to hear the opinions of those on this site.

Thanks,
David

I would just say that IMO, 20° ∆T seems an extremely low estimate given the circumstances described.

Years ago I used a solar shower I built at my camp. Nothing more than a 30 gallon drum painted dark green perched on a scaffold out in the sun. Maybe 6 or 8 square foot of the barrel surface exposed to the sun on one side. Something like this:

Resize_20230120_045415_5040.jpg (279.75 KiB) Viewed 5191 times

https://preparednessadvice.com/problems ... ar-shower/

It got plenty hot for taking showers.

A large metal roof in direct sun, painted black in a subtropical climate would certainly get extremely hot. However, continually running cold water over it would only cool it down, probably wasting nearly all of the potential heat.

Maybe run the water over or just onto the roof during the heat of the day very slowly.

Concentrated solar though, could rather easily reach hundreds or even thousands of degrees, which would boil water.

Steam can get much hotter than boiling water if contained in some way.

Probably water trickling very very slowly through some pipes on the roof could transfer heat to the engine as superheated (above 100°C) steam.

https://youtu.be/R9uvIhgVz04

https://youtu.be/QqbrU3Nwab4

Or the steam could be used to heat some thermal mass (like a box of sand) to store some of the heat for extended use by the engine.

[JessIAm]

Howdy All!

I love this David! This is exactly what I posted this for! Please keep us up to date!

I'm the idea guy, but not the expert. I'd suggest making any Stirling engine (even a model engine) run with this temperature different as a proof of concept.

Also, here's a potential way to increase the heat of the water coming from the spring!

I came across this awesome idea for heating water with only solar:

https://www.youtube.com/watch?v=Y0za-AD5VZo&t=879s

Hello all,

What a great thread. I read through it all and read various other links, papers and articles. I think the thread is flexible enough to accept other similar ideas - so I hope this is allowed.

I have a property that contains:
(a) A free-running stream, most of which is covered by rainforest, so the water is quite cool - let's say 15oC-20oC average
(b) A free-running natural spring, lower flow than the stream, but still enough to always flow. It also flows via a small dam. The key difference is this stream is not shaded by the forest, so it is warmer by the time it reaches and joins with the main stream, let's say 25oC average.
(c) an existing large metal shed with a large roof. The shed is located at a lower elevation than a convenient point to capture some flow from the cooler stream, and the warmer spring

Using no pumps, due to the elevation change, it would be possible to pass the warmed source via a thermal hot water system, leveraging the heat from the sun and the roof of the shed. I assume it would be quite feasible to add at least 10oC but probably more than 20oC to the warmer stream.

The climate is subtropical and apart from frequent but short rain events, the sun shines most days of the year.

Therefore, with very little cost and effort, I can create two significant water inputs with >20oC temperature delta, without need for any energy inputs such as pumps.

Taking inspiration from the thread and the various ideas and examples, I am very curious - is there any potential to use a sterling engine for this application for a generation of a small amount of power?

I suppose I could think of using either vacuum-sealed hot water tubes to increase the temperature of the hot side, and/or some sort of evaporative cooling solution to further cool the cold side. However, both would add cost and complexity vs the simple base case.

I would love to hear the opinions of those on this site.

Thanks,
David

[JessIAm]

Um... why not both? The heating/cooling loops would only need a trickle of water to be effective. Take the normal streams and do the micro hydro, and pull off the heating/cooling trickles to create the proof of concept (and make yourself famous)!

I would love to hear the opinions of those on this site.

Sure to be an unpopular opinon, but two sources of running water calls for a hydro turbine rather than a stirling with a relatively small delta-t.

Depends on whether it's being done for the edification of building the LTD engine, or for an actual power need. Seems like a simple LTD gamma design (like a big coffee cup stirling) could work and the 10-20C delta is more than enough to get a few watts out of it. Not much more though. Either way, any amount of 24/7 power generation is incredibly useful.

...using either vacuum-sealed hot water tubes to increase the temperature of the hot side, and/or some sort of evaporative cooling solution to further cool the cold side.

Use of evacuated tubes to heat the water is just solar PV with extra steps and losses along the way if electricity is the end goal.

[skyofcolorado]

Um... why not both?

No reason, just my experience that maybe 1% of these grand ideas actually amount to anything being built, much less working, so keeping it simple and focused on practicalities is good. But, this is a Stirling engine forum, so if this person is driven to build a heat engine for power generation, then by all means, the more heat from any source the better!

I'm off grid now for a couple decades, so it's a familiar struggle. Practical power generation at levels that are useful vs. cost, maintenance, and other headaches is a real consideration.

[JessIAm]

Um... why not both?

No reason, just my experience that maybe 1% of these grand ideas actually amount to anything being built, much less working, so keeping it simple and focused on practicalities is good. But, this is a Stirling engine forum, so if this person is driven to build a heat engine for power generation, then by all means, the more heat from any source the better!

I'm off grid now for a couple decades, so it's a familiar struggle. Practical power generation at levels that are useful vs. cost, maintenance, and other headaches is a real consideration.

Good point!

[Tom Booth]

If you Google for "Pain Mound", that's the go-to technology for extracting heat from compost, but you really need to think in terms of large volumes- the power density of a compost heap is only about 250 Watts per cubic metre.

Great advice. I referenced Jean Pain back towards the start of the thread:

viewtopic.php?f=1&t=5234&start=15#p16029

The concept of running a large LTD Stirling on heat from a compost heap, even heating your home with it is a great idea and perfectly legitimate/viable IMO but demonstrating that it can't be done with a little 3D printed toy engine and a little tin can Stirling heat pump and a few pails of lawn clippings is a straw man argument.

Call me paranoid or whatever, but I think for every honest Stirling engine enthusiast in here sincerely looking for solutions there are two or three professional paid disinformation agents.