trigeneration, anyone doing or planning one

[mobile_bob]

just wondered if anyone is or has thought of building a trigenerator, ie, electricity, heat and refrigeration?

bob g

[aqmxv]

I've definitely been thinking about it.  The quick&dirty method would involve a car compressor running at some low speed (for long life, and because car a/c systems are huge by house standards), and cycling it with the stock clutch.  Rather than have pressurized hoses snaking around the house with refrigerant in them, I thought I'd use an evaporator coil in an antifreeze tank near the compressor and engine, and then pump chilled water around.  The compressor cutoff and the circ pump cutoff would be controlled by the house thermostat.  An extra-fancy version would include several water tanks for thermal storage so the listeroid could be shut down during the night and still have some cooling capacity available.

I'm in PA, so we only need a few cooling degree days, but we have a surprising amount of humidity from lake effect here.  This summer, I ran three window units (2x 5K, 1x12K) to keep the house bearable during July.  One listeroid that also provided hot water would be just fine instead.

That's all speculation, though.  For the time being, I want to see if I can recover all the heat I can from the engine, which means an exhaust heat exchanger as well as a coil in the cooling water tank.

[mobile_bob]

for some idea's on diy refrigeration,

http://www.rparts.com/index.asp

going to use r22, and a thermal mass storage as well, ice on tube looks good to me

bob g

[aqmxv]

Ice on tube should be very space efficient - you get your 80 cal/gram (sorry - learned water physics in in chemistry class, so calories, not BTU) phase change energy bump for no additional volume/mass.  I'm guessing that there's an optimum shape and size for thermal transfer - I suspect that getting the heat away from the pipe through the water surrounding it so that it can melt the ice further away is the limitation to cooling rate (heat dump rate).  The storage rate equivalent would be how fast you can conduct heat out of the water layer through the ice layer into the tube.  Seems like arranging the tubes vertically in a barrel might help with both, since it would encourage gravity circulation.  Maybe use a bubbler circulator like ice plants do?

Another powerful argument for using a newer tech car compressor is variable displacement.  I like the idea of being able to dial the a/c compressor back in response to electrical requirements without actually turning it off entirely or losing effiiciency with a throttling valve.  Get a variable compressor from some high demand vehicle application, run it at 1/3-1/10 maximum RPM, and use the variable displacement function to load balance electrical and refrigeration demand to keep the engine at some magic load value all the time.  Properly done, you could even use the a/c compressor as a governor assist - detect a frequency (rpm) change and shed or add compressor load to keep frequency in a tight range.  Denso's latest offering is 5 CI max displacement with a 11000 RPM redline, has five cylinders...

R22 sure is nice to work with.  If the thing is out in the back yard and I'm only pumping antifreeze/water into the house, I might be inclined to try ammonia with it... OTOH, that could get you on the DEA radar, since tweakers seem to use that, too.

[DaveW]

I'd like to steal the post for a moment if I can.  Three times now I've seen reference to this term and I don't understand.  Tweaking an engine doesn't seem to fit, nor does tweaking a circuit.  So what is a tweaker in the latest jargon?  Just an old country boy and I obviously don't get out much.

[rgroves]

I have been corresponding with an Amish guy from Iowa. He's buying an oilseed press from me, and he mentioned that he and his neighbors share an engine powered walk-in freezer in town. It's run by a 5 hp Honda gas engine now, and they're interested in Listeroid power for lower fuel economy and the ability to make their own diesel.

I haven't picked his brain much, but I can see how the compressor would easy as can be to run with an engine. But a walkin also has blowers inside, and unless they're cheating a little and making electricity with the engine I can't see how they're doing it.  (Unless they are using compressed air motors to drive the blowers)

Aside from renewing my desire to have another walkin, this really got me thinking about A/C.  It's the difference between "Kansas sucks in summer" and "Kansas sucks and I'm leaving"  

I'm intrigued - have a Mini-Petter that would drive a compressor all day on small amounts of fuel.  Or I could piggyback this load onto my other engine/generator equipment.  
That would really be trigen.  Anybody know how long a run of compressor lines I could get away with?

rg

[rgroves]

I've definitely been thinking about it.  The quick&dirty method would involve a car compressor running at some low speed (for long life, and because car a/c systems are huge by house standards), and cycling it with the stock clutch.  Rather than have pressurized hoses snaking around the house with refrigerant in them, I thought I'd use an evaporator coil in an antifreeze tank near the compressor and engine, and then pump chilled water around.  The compressor cutoff and the circ pump cutoff would be controlled by the house thermostat.  An extra-fancy version would include several water tanks for thermal storage so the listeroid could be shut down during the night and still have some cooling capacity available.

I'm in PA, so we only need a few cooling degree days, but we have a surprising amount of humidity from lake effect here.  This summer, I ran three window units (2x 5K, 1x12K) to keep the house bearable during July.  One listeroid that also provided hot water would be just fine instead.

That's all speculation, though.  For the time being, I want to see if I can recover all the heat I can from the engine, which means an exhaust heat exchanger as well as a coil in the cooling water tank.

I used to have a dairy bulk tank, 300 gallons I think it was.  It had a fairly small compressor and kept the liquid inside near freezing. Seemed to be well insulated too.  If you could run that compressor with a small engine, you'd have a significant amount of cold liquid to circulate into the house.  I'd use Pexflex for the buried run, and could maybe even use the same tank for captured engine heat during the winter.

HMM. Those tanks aren't hard to find and they sell used for about $1 per gallon.

rg

[mobile_bob]

on the topic of trigeneration

went to my peterbilt dealer today to pickup some parts, and found this little jewel

http://www.scsfrigette.com/html/TruckSystems/APUw35.htm

7hp kubota single cylinder diesel, combined with a 3.5 kwatt genhead , a/c pump, 60 amp battery charger
pretty nice compact unit.. heat,power, and cooling,, a true trigenerator

all for a 9,000 dollar price tag! wow


now for my project,

engine c201 thermo king isuzu, 1300 low speed, 2300 high speed
dual leece neville 320 amp 14 volt alternators, with 3 step charge controller, giving maximum 640 amps at 70 degree F, and 520 amps at 93 degree C.
15 kwatt st head,
york compressor 10 cu/in  running r22, for a max of approx 50k btu, driving ice on tube thermal mass storage, and hold plate for refrigeration
full flow filtration, bypass filtration, primary and secondary fuel filtration
exhaust heat exchanger, noise suppression intake and paper element air filter
electric start, glow plug system, murphy engine shutdown protection, remote panel for monitoring and starting
a bit of electrical control for load shareing, and scheduling, shedding.

the goal is a unit that can produce up to 13 kwatt 120/240 at 60 hz. , up to 50k btu of chilling, up to 50k of heat, up to 500 amps charging capacity,
all in a well designed compact and easily maintained and serviceable system.
all in a package approx 30" tall, 30" wide and 42 inches tall, and approx 1500 lbs.

an i think i can do it for a bit less than 9 grand, quite a bit less.

i figure if i am going to build one, i may as well build a reasonable sized one.

bob g

[aqmxv]

That frigette thing is cute!  I don't know if it's 9 large cute, but it's cute.  I bet doesn't sound as nice as a 6/1 running, though.

DaveW: I work in IT, so I keep up on young people slang in self defense.  A "tweaker" as I understand it, is someone who makes methamphetamine--which is a lot bigger problem in the country than in the big city.  Unfortunately, they can use just about anything to do it, so we're seeing purchase restrictions on things like acetone, anhydrous ammonia, methanol, etc.

This is not to be confused with tweaking something to get it to perform better/in spec, or whatever.  I guess we just have to be aware of context...

rg: Good idea.  Those chilled dairy storage tanks are common around here.  You'd probably have to replace the existing compressor with a shaft-drive one, but it's standard refrigeration stuff to do so.  Spreading the day's a/c load over 12-20 hours sure would reduce the instantaneous power demand.  And then there's the fact that efficiency (unless you're sinking heat down a well) is going to be a lot higher at night than during the day anyway because the temp difference across the condenser is higher.

I'd be curious to know how much energy it takes to keep 300 gallons of milk at a constant 34 degrees F on a hot summer day in one of these things.

Another point:  When refrigeration plants were large and maintenance-intensive, everything was chilled by brine pumped to things like walk-in coolers or a/c coils.  Large buildings still use water as the heat transfer medium for HVAC.  There's no reason in the world why you couldn't chill an antifreeze mixture to cold enough to keep a walk-in at 0 F or so and run *that* line where you want it instead of a pressurized refrigerant line.  Efficiency is going to be lower by the amount of energy required to pump the transfer fluid and the amount of heat lost in transfer (insulate line well), but will be higher by the amount of energy not lost in electrical transfer and conversion.  I suspect that if you combined all your refrigeration demands in one unit, and then ran transfer lines around, you'd probably see a substantial win on energy cost.  At least, that's the cost model the large building a/c systems use.  As for turning a fan, you can do it electrically, with a solar fan, compressed air...lots of ways.  Walk-ins don't generally need huge amounts of air circ unless you're moving lots of not-frozen things into them to freeze in a short period of time.

I can see a model where the circ coolant goes first to the walk in freezer, then to the refrigerator, then last to the house a/c coil.  You'd only need one loop of coolant that way and you would have great efficiency at each step of transfer because of the large (but not too large) delta-t and delta-h.  Do thermostatic control by turning the fan on and off or with a bypass valve, or both.

[listeroidsusa]

I'm picking up a 50's model Servel full size ammonia refrigerator in the Atlanta area tomorrow. It is set up to run on propane, but will run on any heat source. It normally uses a pilot light size flame but I'm going to see just how much heat it takes to run it. My 6/1 will supply electricity and the exhaust and cooling system will be set up to first run the refrigerator and then on to the floor slab with the pex tubing in it for winter heating.

Mike Montieth

[dkwflight]

Hi What I see in A/C, refrigeration useing standard equipment. When setting a system up with really long tubeing runs (over 100') you need an accumulater. It is a small tank to hold liquid refrigerant to keep it from the comperessor on start up. The liquid refrigerant can "Slug" the compressor. Liquid  hitting the compressor will damage it as in breaking the reed valves and possibly breaking something else.
I don't know much about the Servel units except they are OK when using a cheap source of fuel. I was thinking A/C, sorry. I have seen several Servel central A/Cs. They circulated a brine solution to the house.

Travel trailer refrigeraters can use an electric heater in stead of the flame. I would assume 250deg. or higher.
I do know some Servel refrigeraters  could be run on a kerosene lamp. Some body had to light the fire and after a certain time put it out. Depends on use and ambiant temps. If the door doesn't get opened you don't need as much. Some late model refrigeraters had a different ammonia circut and could run continuously at a high flame.

If you are on a well, check the water temps. You might be able to cool the house using water in a coil direct. Cornell university spent millions on a pipe line to get cold water from the bottom of Cayuga lake for just this pourpose!.If you has 45deg or lower you are in buisness. Or just keep your beer cold
Dennis

[Rtqii]

It's hot where I am moving... But I am a few thousand feet out of the valley and the humidity is much lower than what I am accustomed to in the mid-west US.

My present thoughts on air-conditioning are probably not congruent with most other locations... But I am confident I can air condition with a spray fountain and a cistern.  I am still working on the house plans but it is clear at this point that the walls will be concrete masonry with foam panels sandwiched in the extra thick construction. On the inside (insulated) I will cast in as much PEX tubing as I can, probably 2-3x the number of feet used for radiant heated floors... I will lay tubing in the floors and walls.

Outside, I will dig a cistern and put a spray fountain in above it... Build a roof over it for shade, and a ceiling fan directly over the fountain to chill the water thru evaporation.  Colder water would be picked up at the bottom of the cistern and pumped with a taco pump thru the pex.... Warm water coming out would be directed to the spray head in the fountain for evaporative cooling.

It's not going to get real cold... But if you have sufficient battery to run the pump and fan at night, it will get cool, much cooler than ambient, and should make the house comfortable.