Adding additional load to you engine (if needed)

[carlb23]

For those who run their engines a lot.

Has anyone thought about using an automotive A/C unit to help heat or cool by liquid phase change?  My thinking is that if you are running your engine at a relatively light load you may want to add some additional load to the engine for greater efficiency and an automotive a/c compressor might be a good way to add a constant load to the engine.  Depending where you place the condenser and where you locate the evaporator you could either put cold air into the house or hot air into the house.  Since these use a simple electric clutch system uncoupling them from the engine drive is quite simple.
You could use one compressor with two evaporators and two condensers fitted with three way valves for both summer and winter use thus making your own heat pump.

Carl

[Doug]

Yes
Bob brought up the idea....
Was it last year oir the year before??

Darn good idea if you have the parts

[carlb23]

Darn I thought I had a new Idea, oh well.  Parts are cheap go to any junk yard and you can find hundreds of donor cars.

[ronmar]

The only problem I could see you encountering if you took a complete system from an automobile, is that they cycle based on pressure.  The Thermal Regulating Valve releases gas thru a variable orifice to control the ammount of expansion and keep the evap from freezing up.  The compressor output feeds an accumulator tank that feeds this TRV and evap(a least in the few systems I have played with).  When pressure is reached, a pressure switch uncouples that pully clutch.  When pressure inthe accumulator drops, the compressor re-engages.  In order to do this as a steady state load, you would need a undersized compressor, or oversized evap, so that high pressure point is never reached.

For heat, I think a liquid heat tank/bank would be easier to manage with various elements that can be switched on/off to maintain a good load...  Never really have a problem keeping cool where I live, so havn't thought of cooling too much.  Heck it is into summer already and we are stuill using the electric blanket at night to get the bed comfortable.

[Quinnf]

Never really have a problem keeping cool where I live, so havn't thought of cooling too much.  Heck it is into summer already and we are stuill using the electric blanket at night to get the bed comfortable.

Ron,
 
Better stock up the ice chest.  It's supposed to be 85 tomorrow, and 88 Sunday, and 85 again Monday.  I'll be in Gig Harbor reroofing a friend's place, then doing the Tall Ships parade-thing around the 4th.  Thought it'd be a piece of cake, but tearing off, then nailing down roofing on a hot day is going to be more like work.

Quinn

[sid]

I am having a hard time understanding how 85 and 88 is hot / we are talking about F and not C/ around here that would be night time temp/sid

[ronmar]

Thats hot for around here.  For roofing, those are the kind of temps when you get up real early and only work till noon.

[mobile_bob]

85 degree's F is blazing hot here in the pacific nw, when you have to run the furnace at night to keep from
freezing your nads off!

up till about a week or so ago seattle only got over 60 for a high something like 23 times since the first of the year
and even then probably only up to 65 the majority of those days.

when it is cold your blood thickens, and then when it jumps up to 85 plus it takes a few weeks for your body to
regulate and thin the blood, so for us cold blooded folks 85 gets very unpleasant if you have to be out in the sun
doing vigorous labor.

my problem is 80-85 is horrible for me, my body does fine up to 75F and when the temps go over 90F
the inbetween temps my sweat glands don't work right and i cannot get cooled off without a fairly constant dousing of water.

when i go back to kansas in the summer where it can be 95-105 with some regularity, i seem to tolerate that fairly well.

on the topic of adding an AC compressor, i think it is a good idea myself and with fuel prices going ever higher anything that
can make the engine run at peak efficiency is  plus in my book.

i have been so covered up for the last several months with work and other issues that i have had little to no time to work on my
trigenerator, but
i did clear a spot in the garage to set up the frame and set the changfa 195, st7.5 and a pair of 175amp leece nevilles on it
in a mock up fashion, i still need to fab a support for the AC (sanborn) compressor.

my goal is to limit run time and to get the engine up to probably 90% load capacity and keep it there for its 1 to 1.5 hour run time
during which time i can get my heavy 120/240 loads met, my batteries charged and make some ice/refridgeration.
the hope is to limit the run times to no more than twice a day, and then schedule my needs/loads to those times of the day when it is running.

only way i can see it working at a high level of efficiency is to put it under some form of control, such as a bs2 stamp or another project
a dl305/bs2 hybrid system.

that way the controller can scan for whatever needs that need to be met and autostart to meet those needs and then shut down again.

the last thing i want is an engine (any engine) running long hours just loafing along at low/part load burning fuel no matter if it is pump diesel
or some other alternate fuel that is cheaper.

if i could meet my needs/goal and burn less than 1.5 gallons of fuel per day i would be thrilled, i think it will be attainable now that i have some
solar to suppliment the system.

maybe i will get some time in the near future to get back to work on the trigen and actually get it up and running to do some testing on.

so little time, and so much i wanna do

bob g

[sid]

just check and it is 9.30 p.m and the temp is 83.7 f// good sleeping weather. cooled off just enough to be comfortable/ i will admit. when it gets 97-100 I slow down some//if I am out west, nevada.arizona,etc 110 is a little hot but not as bad as here..but on the other hand.. the cold bothers me/ if it gets down to 32f // I try to find a warm spot//sid

[jzeeff]

Agreed, for maximum efficiency, you don't want to run your engine at less than 70% load.

I suspect that a good electric  heat pump/air conditioner (look up "toyo mini-split  heat pump or 12RLQ")  might beat out the automotive one, even with the mechanical->electrical->mechanical conversion.

You mention load adjustment - it would seem to me that there is a need for some type of switch unit that would turns off certain electrical loads when the generator exceeds maximum output.   Say for example, that I'm running house lights and an air conditioner.  The well pump kicks on and overloads the gen.  I don't need a bigger  generator, I just need something to quickly  turn off the AC for a couple minutes.  Perhaps generators should have two outputs - required and "optional, can be switched off as needed".

[Stan]

http://listerengine.com/smf/index.php?topic=3548.0

Stan

[mobile_bob]

jzeef:

that is what the control system is designed to do, that is monitor all loads, and drop those not critical to prevent overloading the system on a priority
basis.

for instance top priority items
furnace blowers or boiler pumps, certain lights, must have power to complete their cycles or provide safety

other loads such as refrigerators and freezers can be interrupted but, must be timed before being allowed a restart
so that head pressures can stabilize. sure they can restart under head pressure but that is usually hard on the motors
so i figure if interrupted provide for a timeout of 2-3 minutes before allowing a restart.

then there are less sensitive loads that can be interrupted and allowed to come back online with little timeout if any.
things like TV's, stereo, washer/dryer, and most general lighting. Allong with intermittent interrupt in battery charging
or reduction in charge rate to provide for a pump start etc could be done very easily.

using a rack position sensor, torque sensor, opacity sensor, tach signal, pyrometer, or any combination of these one could determine
pretty closely the amount of loading the engine is under.

and the use of load scheduling, load sharing, load shedding etc principles a workable system can be made to function to whatever
level of sophistication one can dream up and manufacture, in my opinion.

it would require a well laid out design of the total system to start with, a chart of all the loads, their power requirements, their priority
whether of not they can be interrupted, etc.
then put together a large truth table to determine how all the possible combinations that might happen will occur
and then move the loading schedule around to such a point overload does not occur or alter the priority list to provide loads that can
be shed to keep thing under the max limits.

sitting here thinking about it, now i am thinking a single pyrometer probe in the exhaust would be all the feedback i would need to determine
if i am overloading the engine, with possibly a rack sensor to compare it to would be enough to read loading, although a torque sensor and a tach signal
would do just as well.

bob g

[mobile_bob]

an additional thought, after going back and looking at some of my design notes.

if the cogen or trigen is also setup to charge batteries for an inverter system (as is generally the case)
the ability to switch of divert loads onto the inverter side adds another level of contol and a more seemless system.

for instance if one had his generator running at peak design load and a pump needed to start
it could be started on the inverter side off the batteries, the batteries absorbing or rather provideing the surge
capacity  needed to get a startup, and

if your switching capabilities are fast enough, after a startup the pump could be dropped from the inverter and switched
onto the genset ( i am thinking that any switching that can take place in under a 1/2 second is probably fast enough)

i want to experiment with this switching scheme anyway, because i have a 1500watt rotarty inverter that can take a serious
surge load (up to maybe 4.5 kwatt for a few seconds) and see if i can start a difficult load with it and after startup rapidly switch the load off
the rotary inverter and onto a much smaller electronic inverter.

the rotary inverters are typically only 60-65% efficient, but i figure if used only for starting surge loads for short bursts, who really cares
about a lower efficiency,, you can't hardly kill a rotary, but you can kill an electronic inverter or cause it to trip out, blow a fuse or whatever.

anyway i digress (damn i am good at that!)

the idea is to learn through the experiment if loads such as a refrigerator or well pump could be started by the rotary (which i know they can), but
also learn if after the startup if i can quickly and successfully switch over to either a smaller and more efficient inverter or to the genset.

i think it can be done with a bit of thinking and careful design, especially if the contactors/switch gear are controlled by a microcontroller or plc
where subsecond swithing can be programmed in.

bob g

[ronmar]

With the mechanical governor on the roid, and my testing with known loads, I have found frequency to be a pretty good indication of load.  I set 62HZ no load, and am up around 3.5KW at around 58 HZ with a pretty linear progression between these two points.  This is nice, in that I can plug in my killowatt where ever I am at, such as in the kitchen cooking diner, and can monitor load on the engine 100' away by watching the frequency.  This of course is a result of the governor spring selection, but as the spring should remain fairly constant, so should this relationship, and mine so far has.  

This is particularly interesting to me in that this might make it possible for a controller to be placed at the power panel or even at the loads themselvs to control a contactors based on frequency.  No comms circuits, just a frequency controlled contactor with some timing circuits to help eliminate short cycling of loads.  

[jzeeff]

I agree, RPM makes sense to me - when the engine doesn't have enough power to keep up the speed, the "load shedder" needs to kick in.

Does anyone have a circuit design that would turn off a relay if Hz went to less than 58?