Post by thread:[OT:] Stirling engines

A response I wrote for another list that may be of passing interest here: Subject was whether existing internal combustion engines could readily be replaced by alternatives. _______________ > Turbines are far simpler, lighter per horsepower, and vastly more > reliable - but they do so at the cost of less thermal efficiency. > Reciprocating engines, at least to my limited knowledge, wring more > mechanical energy from every BTU than just about anything else out > there. I suspect, though I do not know this to be the case, that a > small turbine driving a generator and charging a large capacitor bank > could drive an AC induction motor for a system that *might* do better > than an all-mechanical drive train connected to a piston engine. Best of all, theoretically, is the "external combustion" Stirling engine which runs on the Carnot cycle, unlike standard internal combustion engines which use the theoretically non-ideal Otto Cycle. An ideal Carnot cycle engine is as efficient as can be achieved thermodynamically. However, a very good xxx cycle engine can of course be more efficient than a bad Stirling engine. Modern diesel engines do a very good job of making an inferior thermodynamic cycle look quite good. In practice, practical compact and power-dense Stirling engines have, so far, proved too hard to implement economically except in niche applications where cost is secondary. The main barriers are the extremely high sealing pressures and high temperatures which the engine needs to run at. Ideally a Stirling engine would use Hydrogen as the working gas but as this has the bad habit of diffusing out through the engine castings and leaking out through everywhere else at the temperatures and pressures involved, people usually compromise and use Helium, which is good but not as good as Hydrogen. Starting soon after WW2 Philips spent many tens of millions of dollars trying to commercialise this technology. They built vehicular demonstrators in conjunction with various automotive people including a van with Ford and a bus with ??AEG??. All attempts proved to have insurmountable problems with sealing. Along the way they did produce a very successful line of Stirling cryocoolers. This business was sold off when they rationalised their activities a decade or two ago. AFAIR Philips estimated that IF/ONCE the problems were solved that the payback time for the investment based on world petroleum savings would be about 4 months !!!!!!!!!!!!!!!!! :-). However, they also placed a rather large figure on the estimated cost of getting it right ($14 billion comes to mind but it was basically "heaps".) So far nobody has seriously risen to the challenge of multiplying their money several times over every year. A NZ designed & modestly successful Stirling combined-cycle heat and power system is selling internationally. Known as the "Whispergen" it produces approaching 1 kW of electricity and about ?4 kW of heat and is targeted at small off-grid applications. The price ($10,000 or so?) makes it unattractive financially compared to grid power where it is readily available. I believe the Swedes make/made a Stirling powered submarine run from heat of crystallisation from a thermal store. The major advantage is presumably very low noise operation. Various military applications exist. A niche market exists for free piston solar Stirling engines and various people have made 10 kW plus solar engines using large dish concentrators and typically liquid sodium as the heat transfer fluid. Russell McMahon -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Like the last part ........... > A > niche market exists for free piston solar Stirling engines and various > people have made 10 kW plus solar engines using large dish concentrators and > typically liquid sodium as the heat transfer fluid. > Would like more detail on this idea. ************************************************* Roy Hopkins spam_OUTrdhopkinsTakeThisOuTihug.co.nz ************************************************* --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.571 / Virus Database: 361 - Release Date: 26/01/2004 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Like the last part ........... > A > niche market exists for free piston solar Stirling engines and various > people have made 10 kW plus solar engines using large dish concentrators and > typically liquid sodium as the heat transfer fluid. > Would like more detail on this idea. ************************************************* Roy Hopkins .....rdhopkinsKILLspam@spam@ihug.co.nz ************************************************* --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.571 / Virus Database: 361 - Release Date: 26/01/2004 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics .

> Like the last part ........... > > > > A > > niche market exists for free piston solar Stirling engines and various > > people have made 10 kW plus solar engines using large dish concentrators > and > > typically liquid sodium as the heat transfer fluid. > > > Would like more detail on this idea. Start here - http://www.sunpower.com/ RM -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Russell McMahon wrote: <snip> > available. I believe the Swedes make/made a Stirling powered submarine run a little more info and a picture is available here <http://www.kockums.se> click "products" and then "kockums sterling" (seriously stupid layout of these pages :-( {Quote hidden}> from heat of crystallisation from a thermal store. The major advantage is > presumably very low noise operation. Various military applications exist. A > niche market exists for free piston solar Stirling engines and various > people have made 10 kW plus solar engines using large dish concentrators and > typically liquid sodium as the heat transfer fluid. > > > > Russell McMahon > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>AFAIR Philips estimated that IF/ONCE the problems were solved that the >payback time for the investment based on world petroleum savings would be >about 4 months !!!!!!!!!!!!!!!!! :-). However, they also placed a rather >large figure on the estimated cost of getting it right ($14 billion comes >to mind but it was basically "heaps".) So far nobody has seriously risen to >the challenge of multiplying their money several times over every year. I've seen interviews with Dean Kamen (Mr. Segway) where he suggests that he's seriously pursuing Stirling engine technology. Or rather, he's putting engineers up to it. I don't know what he's going to do with it, but there it is. Of course, he doesn't have that kind of money, and his Segway of course isn't the model of an ideal product. Mike H. _________________________________________________________________ There are now three new levels of MSN Hotmail Extra Storage! 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I hear what you are saying about the obvious no-hopers, the ones who blame the hardware for there own coding errors, but I don't see any evidence that this chap falls into the 'no-hoper' category! -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. *** MESSAGE TRUNCATED *** .. .

source= http://www.piclist.com/piclist/2004/01/28/094249a.txt? Mike Hord says: > I've seen interviews with Dean Kamen (Mr. Segway) where he > suggests that he's seriously pursuing Stirling engine > technology. Or rather, he's putting engineers up to it. I > don't know what he's going to do with it, but there it is. > > Of course, he doesn't have that kind of money, and his > Segway of course isn't the model of an ideal product. Ok... Lets not start a holy war over Mr Kamen... I've run into a number of people who seem to think he is the ULTIMATE engineer, and while he sure has come up with some nice stuff and has overcome the odds to do it, I think everyone has some good and bad. If you want a good laugh on the subject of alternative heat engines, check out my little fantasy at http://techref.massmind.org/techref/idea/mc-heat-inject.htm --- James Newton: PICList.com webmaster, former Admin #3 @spam@jamesnewton@spam@spam_OUTpiclist.com 1-619-652-0593 phone http://www.piclist.com/member/JMN-EFP-786 PIC/PICList FAQ: http://www.piclist.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics .

James, On Wed, 28 Jan 2004 20:01:32 -0800, James Newton, Host wrote: > If you want a good laugh on the subject of alternative heat engines, check > out my little fantasy at > techref.massmind.org/techref/idea/mc-heat-inject. htm Just a minor technical point: if you "snap off the intake valve stem" it will fall open! The valve is held shut by the spring pushing upwards (on an OVH engine) by the spring. Best to remove the pushrod or rocker arm, if it's a side-camshaft, or as you also say grind away the cam if it's OHC. It would also benefit from having the exhaust valve open twice as often, making it 2-stroke, and stay open until close to TDC, otherwise the compression stroke is a total waste of energy and would probably stop it working. Using a 2-stroke engine in the first place would solve most of the above, of course, but you'd probably have to modify the ports, or use one that had active (such as disc-) valves. I'd like to try it just for a laugh (I have a spare Triumph Tiger-Cub engine) but sadly the amount of energy from the Sun here is rather a lot less than where you are! Cheers, Howard Winter St.Albans, England (currently snow-covered) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. .

>If you want a good laugh on the subject of alternative heat >engines, check out my little fantasy at >http://techref.massmind.org/techref/idea/mc-heat-inject.htm Hmm, now pick up an old car alternator, use it to charge the battery float that keeps the house running, Hmm solar power, here I come :)))) -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. .