Simple Thermoacoustic Generator?

Why not just use a Thermoelectric Generator ?

Looked into it but: even with semi conductors is low efficiency (I know I'm only aiming initially for 5% overall, but would like to improve over time, and that seems about the ceiling for thermoelectrics), not cheap and harder to source materials, need quite a large assembly for higher power output, and difficult to separate and therefore optimise your hot and cold ends.

From your first reference, it looks like the efficiency is about 0.1%. You would need a 50 fold increase in efficiency and a 50 times larger scale. I would think you could get a lot more bang for your buck with a Stirling Engine.

Why bother with this?

Photovoltaic is way more efficient.

Other systems in development are talking about 20% thermal to electric efficiency, NASA made a real nice one that was getting thirty something.

http://peswiki.com/index.php/Directory:Fellows_Thermoacoustic_Cycle_(TAC)_Generator
http://cleanpowerresources.com/content.php?sub_section=thermoenergyconversion&name=the_thermocoustic_alternator
http://nextbigfuture.com/2010/07/thermo-acoustic-generator.html

I'm interested in this over PV because it's something people, especially in the developing world, can easily make themselves largely from scrap.

People in the developing world have ready access to conventional power generation.

I don't see how this could be cobbled into anything useful in the sticks. They'd starve to death in the time it took them to build it.

14 billion people don't have electricity. When I talk to people who are from or have worked in the developing world, it and water are usually the two greatest needs.

Cobbling this together from scrap is what I'd like to set out to solve, so I'm looking for what information and functioning versions I can find to reverse engineer and aim towards.

CR4 is definitely the best forum of it's kind on the net, and I've received a huge amount of help from here over the years, but I always have to spend the first half dozen posts explaining why my initial question wasn't wrong, along with my entire approach, and why I should be asking it in the first place...

*1.4 billion...

If your goal is to help people who do not have access to electricity, consider a design which meets critical needs directly.

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People who lack electricity are probably not going to have the appliances to plug in even if electricity suddenly became plentiful. Providing refrigeration for food storage directly via a duplex prime mover/heat pump design could offer significant advantages....

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No need for expensive copper windings or hard to replace/repair circuitry.

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Working fluid tailored to provide high efficiency can be completely sealed within. No speaker membrane or bellows to leak or wear out.

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Can be designed with few parts and completely without regularly moving parts, making inexpensive manufacture and high durability more probable.

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Here is a pretty good paper on various gas and liquid working fluid acoustic engines/heat pumps.

> consider a design which meets critical needs directly.

That's been my main focus, also got prototypes and concepts for solarthermal, air pressure refrigeration, ground mass temperature regulation, wind mechanical, others.

> People who lack electricity are probably not going to have the appliances to plug in

Seems the two big killer apps in some parts of the world are led lighting, so as to be able to study and work at night, and charging cell phones, which are turning out to form a major communications and economic backbone. People currently have to travel tens of kilometres to pay a significant portion of their income to have their phones charged.

> Here is a pretty good paper

Nice, lot of good info in there, I'll have a proper read through.

Which bit relates to the engine you mention?

The entire paper is full of good info, don't skip any of it!

Figure 16 on page 22 describes generally what I mentioned. It allows a completely sealed system without bellows or pistons. It can be made free of electronics and with no moving parts (well except for the working fluid oscillations).

As heat transfers from input (heat source) across a stack of thin plates to the reject the heat out the ambient cooling fins, work is done creating oscillations. These oscillations drive the fluid across an additional thin stack and heat from the 'refrigerated heat exchanger' is pumped out the same ambient temp cooling fins to which the heat source rejects heat.

I don't follow the design 100%, but it seems very similar to what I'm wanting to build, except using the acoustic oscillations to drive a linear alternator (loudspeaker) instead of establishing a temperature differential (which I thiink is what this is doing...?).

It's the no moving parts (pretty much), no piston, no machining, scrap makeability which I like, as it puts it within reach of a lot of people in the world who, like me, don't really know what they're doing.