the start of my chp system

[Fordguy64]

well not sure if most of you know what a chp is but it stands for combined heat and power. basically a small motor driving a generator to power house and then use the waste heat from the coolant and the exhaust to heat dhw or even heat your house in some cases.

ive started the project on another forum.

Battery/generator project

basically i picked up 2 semi truck apu units. and those both have generator heads on them. one is a 7.5kw at 3600 rpm (ill be selling this one i think) and the other drives a 4kw head at2600 rpm.

my plan is to add a large frame alternator to this motor to charge my 24v 840ah batter bank. that was the main goal anyway. now ive decided to go a little further...

So my latest thoughts for this system are:

1. Use system to charge my battery bank of 24v at 840ah with a 110-555 alt and maybe even 2 of them at some point. UseAls smart dc generator to control that

2. I'd like to be able to drive a 5-8kw generator head also.

3. Use waste heat to heat dhw and maybe some of the house depending on run times in the winter and also the outside temp.

4. This is the one that I know least about and have only seen people talk about but have yet to see a system actually in use. That would be to drive an ac compressor to heat/cool. I've seen a few people talk about it on here but I have not seen any systems in use? Correct me if I'm wrong. Anyone seen any on another site? Links?

Obviously I wouldn't be able to run them all at the same time..


And more info/thoughts on the ac/heat pump idea. I don't use much ac in the summer as I have a whole house can that draws just over one amp at 120v. It does a really good job of keeping the house cool as long as the humidity isn't high. So I would probably use it more in heat pump mode then anything and that actually works out because that's when I have the least amount of solar input to the batteries. So the generator will be running more anyway. I've thought about making a 200 gallon thermal storage/buffer tank for the heating/cooling and just pump that water thru a water to air heat exchanger in my central hvac system. I know that the water would have to be kept very cold (below 40*f) to get any kind of good dehumidification and cooling. On the heating end of things I could use the engine heat on the cold side of the ac system to increase the efficiency and the overall heat output of the ac system..

Anything I'm missing?

so i know we have a lot of handy people with regular ac unit but im looking into the engine driven end of things.. thats where i think ill need your help the most.

any thoughts or other ideas are welcome..

Rob

[Fordguy64]

ok so i started this a long time ago but now its actually happening. i sold one of the generators for 4 times what i paid for it and kept the second one. i now have a 5kw 240v gen head, an ac compressor off of a mazda3 and the old alt off of my truck(will eventually upgrade to heavier duty one). the alt will spin all the time and be controlled with the controller i mentioned above. im in the process of retrofitting a clutch off of an automotive ac compressor onto the gen head. that way i can turn it on and off for less wear on it when im not using it. im going to recover the heat from coolant and exhaust along with the ac compressor.

in the winter time ill recover all that heat and heat my garage or the house. and in the summer i can plumb the heat into the pool and the cold into the house or garage. the electrical load will most likely be the alt doing the most work. the gen head with be for back up. I have a ms4024 inverter thats a charger and inverter it also has 240v input and output.

IM planning on using a 3x8 30 plate exchanger for the coolant side of things.the motor will run no higher that 2600rpm.


ill need the most help sizing the refrigerant side of things. ive been trying to figure out what rpm i need to turn the compressor to get x amount of btu. my findings so far

So some general info.. from what I’ve found a 13k btu r22 compressor has a 18cc capacity per revolution. Assuming it runs at 3600rpm (I can’t find what speed it runs at) that turns into 64,800 cc a min for 13kbtu. The car ac compressor is between 100-120cc per revolution. To get to 3 tons heating/cooling the car compressor only needs to spin at roughly 1700 rpm. Obviously the nice thing about this system is that I can very the rpm of the motor a little to match the heatin/cooling load. The pulley I have for the drive is 6.25” and the pulley on the compressor is 4”. That puts my engine rpm at 1100 and I don’t think the little z482 will have the power to run it at that rpm but I’ll give it a try lol I’ll just have to keep an eye out for another pulley for the motor.

can anyone verify what rpm most compressors spin at? or if im even on the right track for this. ill need help sizing the FPHEs for the refrigerant side. i think ill just need 3ton sizing but a little bigger wouldn't hurt i suppose.


thoughts?

[jeff5may]

Auto ac compressors are designed to run reliably in an operating range. Usually the range is between 1000 and 10000 RPM. If your rig can make it spin inside the range, the compressor will do what it can to satisfy the load.

[Fordguy64]

https://digitalscholarship.unlv.edu/...sdissertations


TONS of info in 180 pages lol