suitable engines for cogen use

[mobile_bob]

thought i might start a topic on the merits of an engine suitable for cogen use.

it would seem to me that such an engine should have the following merits

1. have an expected lifespan of ~5000 hours before minor overhaul, such as rings, big end brg, valve job

2. have an expected lifespan of ~20,000 hours before it needs a complete major overhaul

3. have an expected lifespan of perhaps 60,000hours before it is just gone, or needs major casting replaced
and other major components replaced such as the crankshaft

4. preferably electric start

5. thermostatically controlled cooling system, with a real water pump?

6. ??

what i am beginning to consider is the use of either a lister/petter, or one of the other similar engine's that are of modern design
come with a sae bellhousing, real full flow oil system with filtration and a real pump, decent modern cooling system, etc
probably have to settle for 1500rpm for 50hz or 1800rpm for 60hz

i expect the engine would be anywhere from 3 to 4 times the cost of a changfa for a similar hp rating, probably in the 2500 dollar range
and fitted with a decent radiator, and all the ancillary bits and pieces like solenoids, sensors etc.

obviously the advantage to such an engine would also be its ability to be epa compliant, so there would be no issues in procuring one or using
it for cogen application or any other compliant use.

there are engines in the 12 to 28hp class available that fit this criteria, however

there is really not much in the 6hp class

personally i am not a big fan of the listeroid, because of the myriad of issues that some of the units from india come laden with, but
they seem to have a following and there is a primal desire for open dual flywheel engines.

George over at utterpower.com is working on an indian compressor that looks like it could be converted for engine use, and this might be a
possibility for compliant use in a cogen application. the concept looks good, however i am not sure of the combined cost of the compressor
and the related parts to convert the thing to become an engine.

personally i really like the s195 changfa design, however from a practical standpoint i am thinking a lister/petter or one of the "superstar" engines
with the ability to get them with sae bellhousing, and all the related upgrades as standard equipment might not be a better engine for my use?

there are st single brg heads that would drive mate to an sae bellhousing, negating the need for drive pulleys, belts, tensioners, mounts
and would make for a compact in line unit, i would assume that there are other generators that would also fit the bill.

i bring up this topic because those that are serious about building a real and functionally efficient cogeneration unit, will find that there is a signicant
investment in both time and money to get something that is truely useful and not a hobby project.  i wonder if faced with the  fact that one is going to spend 5 grand or better on a system, perhaps buying a more expensive and better suited prime mover would make better sense both economically and in simplicity of implementation and use.

maybe its better just to buy the "silk purse" rather than trying to make one out of a sows ear?

would be interested in hearing thoughts from the SOMRAD group on this topic, at some point we will be having a conversation with the EPA
about suitable prime movers for micro cogen use, we might as well talk about it now rather than later.

bob g

[Crumpite]

8. A longish history of being in manufacture, so that spare parts will continue to be available.
    Or a history of excellent parts availability, long term.

[cschuerm]

Adding to Crumpites thought....
Preferably a design that utilizes some well-proven and readily available "wear components".  ie: small block chevy bearings, Cummins cylinders and pistons, Detroit injectors.... you get the idea.  Basicly a set of Lister-like high quality castings but designed to use standard parts.

Chris

[Crumpite]

Oh, I get it now.

Sort of a Frankenengine. 

That *is* an interesting thought - just pick the best parts of many designs and paste them together with a little cast iron...
I'm not an engine specialist, but it sounds intriguing !

Crumpite

[cschuerm]

I guess I had a different interpretation of the point of the thread Jens, but I think both directions should be investigated.  We have historical evidence (and group gut feel) that slow-speed engines are more likely to give us the long life operation and greater tolerance to alternative fuels that we all seem to be looking for.  At this time, the options are very limited in that arena.  The closest thing I'm aware of are the oilfield engines such as those made by Arrow/Fairbanks.  I'm working under the assumption that the end-game goal is a design which not only makes the EPA happy but is something that's actually reproducible and usable by a broader range of people than just us die-hard hobbyists.  (but then I often miss the point :-)
Either way, I was just looking at this thread as an opportunity to ponder out-of-the-box concepts which could lead to more discussion on engine options.  Other than the oilfield engines, has anyone identified any really good prime mover candidates?  As an owner of a large number of various old-iron stationary engines (including a couple of listeroids), I feel that most of them are a dead-end.  My 10hp McCormic Deering is probably the one I'd trust to have the highest reliability although it's a gasoline/kerosene fueled engine and not a diesel.  The little 3 cylinder diesel in my Kabota tractor is certainly a sweet running package and they're known to run many thousands of hours trouble-free.  Is such an engine (current modern design high-speed) the direction one should focus on as a prime mover?  I just don't know.  It's just not what I think of when I'm dreaming about a "lifetime" solution....

chris

[mobile_bob]

i guess the point i was making was not so much trying to design an engine from scratch and build up from there
but rather sorting out the various options available to find the better solution(s)

for instance, the listeroid 6/1 seems to cost something around 1400 bucks these days, if you can find one, then to make
it a really good candidate for cogen it needs electric start, so add another 400 bucks, then there is the issues of build quality
so add another 200 bucks or so for teardown and modifications and all of a sudden we are at 2 grand and we don't have a
water pump, oil pump, oil filtration system, tstat etc. factoring in all of this and we get closer to 2500bucks on average.

now finally you have an engine that is likely good for 10k hours before it is due for minor overhaul.

on the other hand, the lister petter 2 cylinder can be bought for about the same money ~2500bucks, it is epa compliant
comes with all the electric start, a waterpump, electric solenoids, alternator, filters, radiator, oil pump, etc. and it is warranted
of 5k hours, so the likelihood is it will run twice that without issues.

that superstar engine that Henry posted about recently is another option, it is a bit more expensive but comes with everything
and has a good lifespan as well.

the isuzu c201 has a long history of reliable service as well, can be bought for ~3-3500bucks reconditioned, and a lot cheaper
as a good running used unit. it is rated ~23-26hp, and for my money would be a serious competitor to any of the indian twins.
it will also run under load at 1300rpm and produce ~12hp. i know of reports that they run 40k hours regularly and more with synthetic
oils and good maintenance, reportedly upwards of 60k hours.

i wonder what other engines are available that would fit the bill and be a better match to start with for cogen use.

bob g

[EBI-WPO]

Bob,

You beat me to it! I was going to suggest the C201, but also mention the Yanmars, and others used in the "Reefer" role. They are typically used for Mega hours with standard maintenance. They are also set up for a superb refrigeration unit. This could easily solve the "Cold storage" desire needed by many in warm climates. Using technology adapted from reefer trailers, you could freeze a water reservoir and "pull" off of it like a chiller when the unit was not actively making ice. Put this hand in hand with DC charging, or AC running of large loads at specific times/demands. The equipment is out there, we just need to use it.


Terry

[Crumpite]

Very good questions, Jens !

I don't know anything about engine longevity, so won't add anything except that it's vitally needed knowledge for our CHP work.

The variable speed transmission option is *wizard* though !

With the ability to vary the Hp and speed at the same time, a *lot* of the problems of heat vs. electrical output are way simplified.

Now we only need a cheap, efficient variable speed drive... 

Crumpite

[EBI-WPO]

Jens,
I believe if you looked at the torque spec of the engine, you would find a loss of torque at 900 rpm. 1800 may be doable but "Heat" efficiency may be down, especially with Veg oil. Low heat and low efficiency would work against the whole concept. The stroke (and camshaft timing) in a modern diesel are not aimed at low rpm efficiency. Running at the torque curve 1800 at least and probably 2000 and up, puts you in an economical and efficient mode of power and heat recovery. I know that is different than "Lister" thinking, but I believe that is what you would find.

The variable speed transmission exists in a few forms, but compromises must be made. Efficiency in many are not great, coupled with low efficiency mode in the modern engine would work against you. The Variable sheave belt drive (CVT) have been used extensively and are reasonably inexpensive, but have a limited lifetime.

I don't believe cutting engine rpm would necessarily extend operating intervals, especially if "heat output" and efficiency were compromised in any way, and that is with diesel. With Veg, I would think matters would be complicated further.

My opinion only,
Terry

If you were to run the modern engine efficiently for limited amounts of time , doing More work, the fuel usage would probably equal slow speed, long runtimes.

[cschuerm]

Darn good question and line of thought Jens.  One of the reasons I've been following the DC generation threads so closely is that it at least in part addresses the ability to vary engine speed.  I have not seen any hard research on engine life vs operating speed unfortunately, but there are well-documented issues in the aircraft engine world with operating at lower than designed RPMs while maintaining high manifold pressures.  Mechanical stress/strain issues aside, I do believe you could find a fairly linear hours improvement with a corresponding decrease in RPM.
I'm pretty sure that the linearly variable speed transmission is the holy grail of the auto industry as well, and their substantial resources have not been able to come up with a great solution.  Given the state of the art in multi-speed automatic transmissions, you might be able to come up with a setup with multiple specific speeds without sacrificing too much efficiency though.

[mobile_bob]

before i went with a mechanical vari-drive setup, i would look at generating DC and use an inverter to get me
the 60hz i needed.

it would be so easy to do, and virtually maintenance free from a drive standpoint.

if the load was low the engine speed could be reduced to it lowest rpm and if it were high it could be brought up to
full rpm, and everything in between.

these little honda, kawasaki, yamaha gas inverter/generators work very well and increase the overall efficiency
and i would expect also the lifespan of the engines.

as far as lifespan, in my opinion engines from 650-1800rpm probably have their lifespan predicated on the quality of parts
used, build quality, and perhaps most of all, providing clean air, fuel and oil for them to run with, along with a stable temperature
where everything works best like 200degree's F or thereabouts.

building with induction hardened liners, crankshafts, high quality rings, silicon/aluminum pistons, and keeping the tolerances right, and
building the engine cleaner than an operating room , along with stable temps and good maintenance probably has more to do with
longevity than rpm ever will. that is between 650 and 1800rpm or so, all bets are off at 3600 because most engine's built for that
speed range are generally built for low weight and longevity is a secondary concern.

cheap engine probably does not equate to long life, more expensive engine might equate to long life, but
there are always those that make exaggerated claims so common sense will likely weed out the bullcrap.

the more i think about this subject, the more i am convinced there is no "one" single engine that is appropriate for all applications

to answer the earlier question, in re to what modern engine will tolerate veggie oil fuel, probably none of them over the long run
but then again there is no engine that will tolerate raw veggie over the long run without some intervention, minor overhauls along the way.

if i were to want to burn raw veggie oil and particularly waste veggie, i would probably use an electric start GM90 or an electric start listeroid,
or even an electric start changfa, and i would expect to be fiddling with it from time to time to keep it in operating condition. that is if i asked it
to run long hours on a daily basis.

actually i would pick the cheapest and easiest to work on engine that was sized appropriately to provide my base load and have the engine
running at 75% plus of rated capacity.

now in my case, i don't plan on long runs on a daily basis, so burning pump fuel or a blend of pump and wmo is ok with me, and i would
expect any of the newer designed idi engine's would tolerate either fuel quite well, although i would be running the engine at near full load
as i could keep it, and get the job done as quickly and efficiently as possible.

the c201 will tolerate a 50/50 mixed fuel just fine, and i would not expect it to reduce the longevity of the engine either, but then again
a 10k hour engine would run me for approx 13.5 years and a pair would run me nearly 30 at which time i would be likely either dead
or cooling my heals at an old folks home.

the main difference to me is that i am not too much concerned with the cost of fuel, provided the engine is always running in cogen mode
where the overall efficiency would likely keep my cost per kwatt/hr reasonably close to the utility company anyway, factoring in everything.
(that is for a 50/50 mix, somewhat higher of course for straight diesel)

just my thoughts

bob g

[mobile_bob]

i think i would like to add a bit more to my comments as it relates to different engine's

i am no fan of the indian listeriod, but i will concede that they can be made to be a reliable engine
and are simple and easy to work on, the parts are relatively inexpensive as well. they also seem to tolerate
just about any fuel that is flammable.

folks like JohnF have amassed 20k hours plus on these engines and this cannot be discounted, there is also
the air compressor (gm90) that could be made into an engine and it ought to be pretty reliable as well.
Veggie is importing engine's to canada and those look pretty good to me as well.

the changfa is just a tough little sonofabitch, cost per hp is about as good as it gets, a bit more complex than a listeroid
but certainly within the capability of any diy'er that puts his head into it, my understanding is the changfa is noted for being
a 20k hour engine, and likely will do so if fitted with a full flow oil filter.

as for the big twins, JohnF has been working out the kinks with these big boys, and when he gets the camshaft done these
engine's ought to be as good as it gets for a 2 cylinder 1000rpm engine, and they too ought to make 20k hours properly
perpared.

the petteroid twins, i personally think ought to be a good engine, they are 1500-1800rpm engines, but can run at 1000rpm
without issues, we don't have much feedback on these engine's but i see no reason why they ought not be at least a 15k hour
engine if they are properly prepared.

any of the aforementioned engine's are familiar to most of us, simple in design, parts realistically priced and no problem to work on.

for just a tough engine, that will be asked to burn a variety of alternate fuels, these are probably the best available to do so in my opinion.
and for long hour operation where owner repair is of top priority maybe these are the best choices?

on the other side of the spectrum are the more modern engines, like the kubota, cat/perkins/shibara, isuzu/thermoking c201, the lister/petter,
and other engines like the superstar engine.

these engines are somewhat more complex, being multicylinder and mono head means if you have one valve hanging you will be removing
the head from all cylinders as opposed to a single cylinder head. most of these engines use head gskts that are not reusable so there will be
added costs associated. the cost of parts can be quite high for some of these engines, but not all, for example a complete overhaul kit for a c201
can be had for about 650bucks or so. the injection pumps are likely more expensive to service, so it might be risky to use alternate fuels? i would expect a higher cost of ownership when it comes to the injection systems. the upside is all of these engine's use real oil pumps, full flow and in some cases bypass oil filters, some cases oil coolers, water pumps/tstat controlled cooling systems, and are generally of very high build quality.

as would be expected their first cost is substantially more than the first group of engine's in most cases.

where i think this tier of engine pulls ahead is in reliability, and the ability to run long hours at a fixed load, which can be engineered to fit the need.
most of these engine's will be either epa compliant as engine's or at least much more so than a typical indian engine, most all will be as high or slightly higher in efficiency, and most will have a cleaner exhaust that will help in keeping the heat exchanger from clogging as soon as the first tier engine's (generally)

just more rambling

bob g

[cschuerm]

Jens,
That sounds exactly like the design of BMWs continuously variable ratio steering box.  I hadn't thought about using that concept for a variable speed control.  Seems like you'd loose a lot of torque...

http://www.usautoparts.net/bmw/technology/afs.htm

chris

[veggie]

I think there would need to be multiple solutions for CHP systems based on the varying needs of the system.
Rather than looking for that one ideal engine. I would propose a general "criteria" that would apply to any engine that was being considered as a CHP candidate.

REASONS:
1] Depending on the size of the system, the engine rating could vary anywhere from 2kw to 15kw for micro CHP. The maker of a 3kw engine may not have a valid offering in the larger sizes.

2] Climate: The system may be needed for cooling or heating depending on the location.

3] Fuel: Where diesel fuel may be the primary fuel in one area, natural gas may be abundant and inexpensive in another. In some areas, WVO is prevalent and free, while parts of the USA have no available WVO. This too may effect the choice of engines.

So Bobs original suggestion of a general spec makes sense to me. Various engines (of various sizes) could be compared against the spec.. Some may meet all requirements while others may become the best choice because they meet more criteria than others ( but not necessarily all the criteria).

veggie