> ... Anyway it would cost less than half to build, compared to what a 
> 500 Watt Stirling costs (5000 EUR).

Why?
People seem to want to dismiss Stirling engines for all sorts of 
reasons but most seem to be based on false impressions or uncertain 
assumptions. What it costs to BUILD a 500 watt Stirling engine is 
quite different from what it presently costs to buy one. The 
difference between cost and selling prices includes such factors as 
marketing, suitability for niche markets which will tolerate higher 
profit margins and the consequent "what the market will bear" 
costings. If you are making say 10% profit then if you double the 
selling price you can afford to sell somewhere around only 10% as much 
before you lose money. Fixed costs, volume sensitive costs, size of 
plant and many other factors apply but as a general rule, for a niche 
market product the true cost of production is quite different from the 
selling cost. It's only when you get a highly competitive commodity 
market that the two approach each other closely. (The invisible hand 
at work :-) ).

So: The same would apply to any other engine you built. The Whispergen 
may be the basis for that statement about cost. I greatly doubt that 
it *costs* E5000 to build a Whispergen. There is nothing overly magic 
about Stirlings or arcane in their engineering, as long as you don't 
want high volumetric power density. In the applications being 
discussed here that's not a requirement.


        RM

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