Micro CoGen.

Do you have pictures of these units? I have pretty good knowledge of these PMGs. Most likely going to have to spin them in the 2700 - 3600 RPM range to make voltage. Were designed to output 52Vdc in a high wye config while being attached to a small air cooled engine.

-Eric

My website is www.shawneepower.com

I don't have any information on the PMG alternators themselves. I haven't been selling them as individual components just used in complete generator systems. I will be happy to answer any questions you might have.

Eric

I am manufacturing them.

It is a spark ignited (dual fuel, LP or gasoline) Kubota. The engine block is the same as the diesel D902. The latest tier models are called WG972 instead of DF972.

I've built a few 1800 RPM LP generators using a Kubota DF972 engine. You can get about 6 kw output at that speed. If you want a DC output you can run the engine slower. Idle set point on them is 1500. With an electronic governor you could probably go down to 1200 RPM. This engine would outlast any air cooled engine if it is going to run for a significant amount of time per year.

Don't know if this will help you but here is some data I got while testing a CHP.

I used a Yanmar 2TNV70 engine and it ran at 3600 RPM. Output was 8kW (27,000 BTU electrical). It burned .7 gal of diesel/hr (93,000 BTU). Using heat exchangers I was able to capture 42,000 BTU from the exhaust and engine heat.

Maybe that can help provide a starting point to scale the system to your size. If you use hydronic any extra electrical capacity could be used to heat the water placing the engine under an optimal loaded condition.

I wanted to put a closing to this project. I never was able to make the time to finish up the electronic controls for the CHP portion of the project however it has been put to use assisting solar panels at an off grid residence in the northwest. The output of the unit is for a 48V battery system. It can produce a maximum output of 150 Amps of charge at 55.8V (8.4kW) at 3600 RPM. It runs at a variable speed based upon load from 2200 - 3600 RPM. The automatic controller will start based upon battery voltage or the generator output from the inverter. When started by the inverter or for a low battery voltage the generator runs until the charging current falls below an adjustable amperage level. The starting voltage, charging voltage, max charging amps and shutdown charging amps are all adjustable. It will also compensate the charging voltage based upon the battery temperature.

I'm disappointed I wasn't able accomplish the starting goal of a CHP unit but I thought this unit turned out nice and will provide many years of service assisting a solar array.

Progress has been made but it has been slower going than anticipated. Had other projects that have side tracked me. A new skid base has been designed. It came out quite nice. I will try to get some pictures up soon.

Next step - the electronic controls.

HI. I've enjoyed reading your posts. Very interesting project. How would you do the gate drive on the high side drive? Would you use zener diodes to clamp the gate voltage to an acceptable value? A low side drive is much easier to do as you can reference the gate drive to gnd. When you do a high side you have to reference the gate drive to +Batt voltage. When you drive the gate you have to keep it offset from ground to be within the limits of the devices gate-source voltage. +/-25V for the device you have chosen. If you have a 35V battery rail you can't just drive the gate to gnd. The high side would be fine for 12V system but anything over that will require more components in the gate drive. The low side drive can drive any voltage within the limits of the FET as the gate drive is referenced to gnd.

I will be designing a microprocessor based controller to control the engine speed. I installed a linear actuator in place of the electronic fuel stop solenoid to do the electronic engine governing. You could do a set speed application and rectify and run the output through a solar charge controller too.

Quote from: RJ on January 21, 2013, 10:17:58 AM
Speaking of 48v PMG's. How do you regulate them? I was interested in one of Henry's awhile back but was unclear how to regulate them. I was thinking perhaps you could feed them into a solar charger as PV voltage isn't fixed like a traditional alternator.

To regulate the output you either have to adjust the speed at which the PMG spins or put a converter on its output like a SCR chopper circuit or PWM controlled device or better yet a solar controller.

Quote from: mr.fixit on January 20, 2013, 04:30:03 PM
i watched the video again and have a question.

Would the exhaust HX be more efficient and work better if the engine exhaust went thru the center with the coolant surrounding it?

The egr coolers that I was going to use have the exhaust going thru the center small tubes with the coolant around them,so just wondering.

Mr.Fixit - I guess you can argue which is more efficient. It's been done both ways. It just so happens it works out for a better mechanical fit later in the next revision to run the exhaust over the tubes than through them. This HX took about the perfect amount of heat out of the exhaust so I didn't look any further.

I have a handful of them left over from a previous product line. What kind of power are you needing? I probably have one that will work for you.

Hi Bob,

I might be able to help you out. I layout PCBs on a fairly regular basis. Do you have a schematic of the boards? Doesn't appear to have too much on them.

I've used Advance Circuits a lot. The $33 special is good but their "Barebones" special is great if you can live without a soldermask and silkscreen. Take a look a Imgineering Inc. (pcbnet.com). They have some good prototype specials too.

Eric

Based on memory...(I'll double check the data) 600 -700 degrees exhaust temperature drop.  We were pumping water at about 3gal/min.