Slingshot - clean water, Kamen?

Question

In reading a brief article about the Slingshot water purifier, it would appear that he is also providing a Sterling engine that burns "anything" to produce 1 kilowatt. Can this be improved by adding solar energy as a further catalyst to the Sterling engine? Are there any references that better explain how the Slingshot or his Sterling engine actually work?

I agree that clean water is the first step to helping impoverished people - but I'd prefer to see how a whole project plan can be used to transform poor communities into strong communities where people have a chance to live without fear of starving or dieing from disease. I believe there are a myriad of solutions and I'd like to know of comparable tools that could enable the poverty stricken.

Answer 1

Not sure what the arrangement is here, but...

I think you might have a temperature problem with using solar heat for Stirling engines. You want the hot end nice and hot to give you any efficiency at all, which is why actual burning stuff is the preferred method. Getting high temperatures with solar means a lot of collection and concentration - not practical for 1kW.

However, "ambient" energy (i.e. renewables where we don't control the input, like solar) can work well in combination with a fuel burner - you just modulate the fuel burner to whatever is lacking from the ambient. Keeps fuel burn to minimum. This IS done in various places (Unst and Uganda are two I know of) but no-one has done it with Stirling engines to my knowledge.

Answer 2

The term "slingshot water purifier" isn't familiar to me, although the Sterling engine is.

The original Sterling engine was invented by a minister of the Church of Scotland, the Rev. Dr. Robert Sterling, who was distressed by the number of his parishoners killed by boiler explosions from the primitive steam engines used in the mining industry in early 19th century Scotland.

His invention, technically known as a "closed cycle" heat engine requires only a difference in temperature between the 'hot' and 'cold' side of the engine. (see: first reference below)

The air originally trapped inside the engine when it is assembled is the only air the engine needs. There is no intake, no exhaust, no valves, and is extremely quiet in operation.

It operates by virtue of the expansion of air trapped in the 'hot' side of the engine which pushes a reciprocating piston, while another 'piston' (called a 'displacer' and much looser fitting in the chamber) sweeps the entrapped air from the 'hot' to the 'cold' side of the engine.

It is only the expansion and contraction of the entrapped air when swept from the 'cold' to the 'hot' side that makes the engine work.

It's heat source is immaterial. It should also be noted that if the 'hot' side of the engine is maintained at 'room' temperature, and the 'cold' side is exposed to a lower temperature, the engine will still operate. It only needs a DIFFERENCE in temperature to run.

The Sterling engine provides little acceleration, but substantial speed, and a reasonable amount of power, hence it isn't used in automobiles.

There is some interest in 'ultra-low temperature Sterling engines' with at least one book on the market by James Senft that I have purchased entitled "An Introduction To Ultra Low Temperature Sterling Engines" that goes into great detail of several engines designed to operate on the differential temperature between 'room air' and the heat from the human hand.

I was unable this evening to locate it on Amazon, nor it's ISBN number.

I have spent a few years researching the use of low-temperature differential Sterling engines for use here in Alaska.

My intent is to design an electrical power generating station using only the difference between the liquid water beneath river ice (+39 deg F), and the -40 deg F. ambient temperature to replace the costly (and polluting) diesel generators used now. I have had little 'outside' interest so far, but continue anyway.

If I can be of any assistance, you can contact me here, and we can discuss this further.

I wish you luck in your endeavor.

Ouzinki