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General Discussion / Re: Stirling engine revolution
« on: March 20, 2020, 11:30:38 PM »
Be interested in seeing what you come up with.
Forgive me, and this is certainly not personal, but I have been reading my whole life I can remember about Stirling engines and miracle breakthroughs with them about to change the world. Bit like the endless new engines that weigh 3 Kg, do 500HP and get 196 MPH.... All just around the corner and NEVER happened.
I look forward to all new developments in engines BUT, the only ONE I have ever seen come to reality was the rotary. And now that's gone too. To me there are sound mechanical and physics based reasons the stirling is unsuitable for automotive and the majority of other power applications despite their merits and until someone comes along that disproves those beliefs, everything else is the same old hype or yet just another press release mainly aimed at raising investment $$.
I'll believe something new and wonderful has been created when I see it in the showrooms . :0)
Yes, I have seen the very same thing all the years. Marketing is the main culprit. In the older days stirlings were more complicated in theory and weighed more for the same horsepower of regular automobile engines and so were not competitive. They also took longer to start. Nowdays, with all the emissions BS there is on regular car engines...... NOT SO! Really now, the BS is deeper than ever berore! Modern emissions garbage has made the once complicated stirling cycle look like a toy compared to all the complexity of all various catalytic systems, and for diesels now we add the particle filters, piss injectors, and yet another extra catalytic converter!
Now if we add really modern materials and knowledge to the old stirling concept, what we get is a little like Star Trek. There is a very serious efforts on going with major energy corporations to use thermoacoustic stirling cycle based technology to liquify natural gas, with large prototypes (over 500 gallonsLNG/day) already in operation. The most modern submarines use stirling engines and can stay under water for weeks without nuclear power. Nasa currently uses stirling engines in spacecraft where efficiency and weight are extremely important.
I mentioned the free piston type engine, very simple in construction. Very complicated calculations needed to design. Only two moving parts, no cranks, or bearings. Pistons are gas floated or magnetic floated. Most efficient of all concepts. The Thermoacoustic concept has NO moving parts but is a little less efficient. About 30%-35% at best, but hey, that's as good as most diesels. Good design principles are always needed, and I see a lot of amateur engineering used for testing these engines, with the expected bad numbers emerging from these tests.
Oh yea, they are also very quite! The reason they are used in submarines. For off grid, electricity is easily, and very efficiently generated from burning wood, or anything else! Refrigeration for food storage and air conditioning is just as easily done with a stirling driving a compressor and a refrigerant, or compound stirling machines and NO refrigerants.
The machine work and shapes are very simple. The dimensions are not simple to calculate if a viable machine is expected. All dimensions and the weights of the two moving parts are very important. Dimensional tolerances will not be extremely tight however. Material choices and assembly techniques (I.E. welding processes) will be very important. Working gas will be extremely important with high pressure helium the best. The best machines will have higher pressure combined with higher hot side temperatures. This is why materials and assembly must be carefully chosen. Just because there are stirling engines that will run on the heat of your hand doesn't mean they are efficient and of any practical use! These are "bait" engines used to draw young people into college engineering programs, for which the other incentives (scholarships) will not be offered the next year and the school will get all your money, which you wont get back because your field of study will be obsolete before you graduate! Yea, the system is broken and a very corrupted racket with loads of greed, a modern day mafia type system.
Also, a well built free piston engine (hermetically sealed system) will last 30 years or more.
I am posting all of this info for all off gridder's out there that need a good sustainable low or no maintenance power source.
Who knows, with this virus stuff going around we might all need to live isolated in the woods like our pioneers did for a while.