randall gabriell wrote:I will keep this thread posted on our progress but we are aiming at a sterling that could be made for 500$ give or take and produces 1kW.
Bill Bianchi wrote:This thought is most likely unworkable, but here it goes for your consideration.
Since Stirlings seem to be good for high speed operation, but not so great for horse power, would it make more sense to drive a static electric generator with it?
Justus Walker wrote:Stirlings seem to be the silver bullet for us off girders! The stirling solution seems so obvious, so right there and yet so out of reach!
Might it be that using modern materials and machining technology, might we not be able to build these engines in the 1-2hp range for an affordable price?
Am I just off my rocker.
It seams to me that a 1.5hp stirling coupled with a Vulcan Gasifier, using a belt driven fan to produce the draw necessary to keep the gasifier going and storing the extra sun gas in a weather balloon for later use could provide a situation where you could run your little engine most o the day, keep a battery bank charged, rain or shine, using readily available biomass as fuel. The problem with an ICE is its short lifespan. It seems to me that the very nature of the stirling would mean a longer life, less hassle or concern with really clean gas, meaning you could use less quality fuel and gasifier etc. It all seems to make sense IF... we could get that engine!!
The Robertson/ Erricson engines were one of the most popular domestic engine in there time for many of the same reasons we want something like it.
Comments, input??
Marcos Buenijo wrote:
A few thoughts - there is no need to use a small gasifier designed to generate engine grade gas (i.e. an Imbert) for an external combustion application. A simpler furnace could work and would allow for using wood with a lot less processing. Also...
I think many external combustion engine configurations with biomass fuel can be configured to be more versatile and more efficient overall than biomass gasification with internal combustion. Unfortunately, the development of these systems is not there as you know. In particular, I think Rankine or Brayton systems are more promising than the Stirling. I've already mentioned the prospect for Rankine (i.e. steam) systems. A micro scale Brayton cycle might be configured from an existing air compressor, and using an appropriate expander. Something like a steam engine running on compressed air might work well if the expansion ratio were sufficiently high (compounding would help). The two features that I believe can make this option more promising than a Stirling engine include (1) the heater is not restricted with respect to size and can be configured for counterflow heat exchange (both will permit higher efficiency in heat exchange than a Stirling), and (2) a lot of heat can be regenerated easily by using the heated air exhausted from the expander to support all combustion in the furnace.
Len Ovens wrote:
So, then what if one was to use both? Use the waste heat from the steamer to run the stirling.... Or use the stirling as a chiller. The nice thing about a stirling is that heat does not have to be well controlled. So it would be possible to use more than one source of heat. I don't know if it would be as efficient as just PV cells to use solar heat though. The solar would need to be tracked and in the end sqft of solar collection is what it is. It ends up being wood heat to be practical. Be nice to try both.
Marcos Buenijo wrote:
Len Ovens wrote:
So, then what if one was to use both? Use the waste heat from the steamer to run the stirling....
The temperature from the steamer is too low to achieve worthwhile efficiency for a Stirling engine.
Marcos Buenijo wrote: This is so quite simply because low cost internal combustion systems are available along with low cost petroleum based refined fuels.
Len Ovens wrote:
IC engines that last as long as stirling or steam, cost as much or more. The average 3.5kw genset available at the big box with a b&s motor will not last a year doing 24/7... maybe not even half that. Even replacing the motor with something from a car will not last that much longer. Diesels start at $3500 with 2 year warranty... means not designed for continuous run, and go up from there. The diesels they use for backup in nuclear plants have a MTTF of under 10000 hours... about a year of continuous running. Basically, to get an IC that will last long enough for 24/7 use (not counting fuel costs which would keep you from running over night for sure) one is looking at a Lister(oid). If you can find a Lister, it will need TLC before it runs or cost a lot. A Listeroid from India will still cost $3500 without shipping... and generally still need some TLC (even brand new) before it runs. It will still need a generator, cooling, fuel system, shed, etc. At least it will be able to run on waste oil if properly treated... but waste veg oil has become a commodity with a price in most places. I don't know if a Lister(oid) can be run on wood gas reliably. or what it would take to do so, or if it would have even half the efficiency. The general rule of thumb for IC engines is gas gives 10 HP for 1 hour per gallon and diesel gives 20 hp for 1 hour per gallon (from the boat design world). I don't know where wood gas fits. That is the one thing about wood gas ICs is can they be made to last? They are all conversions from gasoline ICs and there are not many of those out there that last. There are some boat motors that are pretty good, but they will be older and need rebuilding before use as they all seem to have gone diesel. There are also some old stationary gas engines from days gone by that could last. Some of them even have intermittent firing.
All of the sudden, externally fired engines that can last the life of the owner don't look so bad.
Justus Walker wrote:Marcos - You keep coming back to the steam engine as a good fix, but then you keep saying that there is not one available on the market. So it is not a good fix!
Justus Walker wrote:Marcos - You keep coming back to the steam engine as a good fix, but then you keep saying that there is not one available on the market. So it is not a good fix!
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