Hello All -
A colleague of mine and I have been working on a Combined Heat and Power unit. As a disclaimer this is a project we are attempting to develop and market. We have some of the major components put together and have run some test data. We have decided to post some information to this forum to see if we can get some feedback on the concept and its performance.
We used a Yanmar 2TNV70 diesel engine and attached a 24 pole PMG generator. An electronic governor was installed on the engine so it can be controlled for variable speed to regulator the output of the PMG. We are able to get 8KW of electrical power out of the system @ 3600 RPM. We configured the unit for 48Vdc but could be configured for 24Vdc as well. During testing the output of the generator was roughly 54Vdc and 150Amps. We installed heat exchangers on the exhaust and engine cooling water.
Without getting too winded in the details here is what we were able to extract in heat and electrical energy running at full electrical output. The below data is based on a 160deg F input water temperature from the water storage tank.
Fuel Input: 0.7 gal/hr (2.7L/hr) = 93,000 BTU/hr
Electrical Output: 7.9KW = 27,000 BTU/hr
Exhaust Heat Captured = 12,000 BTU/hr
Engine Heat Captured = 30,000 BTU/hr
Sum of Electrical Energy and Heat Captured = 69,000 BTU/hr
System Efficiency = 74%
Our next step in the process is to package the systems in an enclosure and work on the automation. Thank you in advance for any feedback. I will post more as we move along and if any questions arise.
Regards, Eric
Hi Eric,
That looks very impressive. I hope to see pictures.
Henry
Isn't slower better for life expectancy?
Casey
Running the engine slower will increase life but will also lower output of electrical & heat output. I wouldn't suspect this to be a 24/7 application. It would be something that would cycle on/off on battery voltage or hot water needs. We started down the path of getting the most out of engine. Designing the automation to be flexible enough to operate under various installation will be the next challenge. Depending on the load, battery A/hr capacity, hot water usage and storage will require the generator to operate differently.
Slower is not always better. Any modern engine you purchase needs to be ran at the manufactures recommended speed. Manufacture spends Millions of Dollars on R&D. So they should know where there engines run best.
The B&S Marathon engine has a 20,000 + hour life expectency. But if you look at the oiling system you would understand why they last. The marathon engine oil is kept to operating temp with an electric heater when not running.
Running an engine below its operating range will cause vibration issues and can tear things apart.
The old Witte, Lister CS, Fairbanks Morse and Blackstone engines were fine engines in there days. But to me they are just engines of the past that will never meet todays Efficiency and Emission standards. They will never be able to pass the requirements of todays modern engines. I love old slow running engines but trying to use it on a CHP unit that will be ran intermittent is not efficent. Todays Modern engines have very low mass. The cooling passages are sized for quick heat-up of engine components. Yet they are designed to cool efficently. This is whats needed for any CHP project to be sucessful. Old slow running engines have to much mass and will take to much time to reach operating temp. For example, The Kubota Z482 engine I had reached operating temp in less than two minutes from 3000 to 3600 RPM's. This is whats needed to develop a effecent CHP unit.
Henry
Henry,
You make some very good points about modern engines and the requirement for fast warmup in CHP applications.
If a CHP system is to be stopped and started as demand requires, then it makes sense to have a rapid warm-up cycle.
As an example, it takes my Listeroid cooling system a 1/2hr of running to get to 190f. (I'm talking about the whole system, not just the liquid in the engine.)
This is not practical in a start/stop system.
I think one exception to fast warm up requirements is a CHP system that runs 24/7 (or almost continuous). In that case, once the system is warmed up there is a considerable amount of thermal stability in the "high mass" engines. For a continuous system perhaps the "old iron" is still workable. ;)
cheers,
veggie
Here is a short video showing the unit running.
very nice, what are you using for an exhaust heat exchanger? I would like to get something very similar for my kubota D905, it also appears you are just running the engine coolant through a plate heat exchanger. Is this correct? In planning my system I have considered running an electric fan on the t-stat. When there isn't a demand for heat the rad would heat up and turn the fan on, another thought was to use a electronic valve to bypass the radiator completely when demand for heat wasn't being called for....
-Randy
It uses a 155K BTU Tube and Shell Heat Exchanger. You can find them on Ebay. The engine coolant does go through a plate exchanger in series with the radiator. Through the plate first. The plan is to install an electric fan that will turn on if the plate isn't capable of removing the engine heat. We thought about a radiator bypass but elected to keep the radiator in the system and use a fan when needed. It was simple that way and eliminated a lot of design work.
Nice setup.
That rectifier -heatsink setup looks like the same as in that Kohler com6 that I posted a while back looking for info on.
I think I see a pyrometer probe in the exhaust manifold,what kind of temp drops are you seeing thru the exhaust HX?
Based on memory...(I'll double check the data) 600 -700 degrees exhaust temperature drop. We were pumping water at about 3gal/min.
I picked up a couple VW EGR coolers on ebay to use as the exhaust HX but I like that one you used better.
That Yanmar is a nice little engine. Mine has about 175 hours on it.It has run flawlessly with no oil consumption to speak of.
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.
Where did you get the 48V PMG? I am upgrading my system to 48V and need to source some 48V generators.
Nice looking project!
Jonathan
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.
Some people have done that. I understand that the Midnight classic is a good choice as the load on the generator can be limited.
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.
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.
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.
what do you use to control the engine speed based on load? Interesting setup. Can you run the output directly into a PV controller for either charging a batter bank or converting it into AC. Thinking a grid tied setup PV setup.
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.
I, too, have a 2NT70-HGE project going. I initially considered belt driven so the engine could operate at a higher speed for best torque. But, after consideration, I chose direct drive.
My thinking was that since Yanmar designed the engine plain, oil lubricated rear bearing for direct drive, any side thrust from belts would have to be supported by the oil film in the plain rear bearing...an iffy thing. I can imagine having to take down the engine after a few hundred hours to replace the rear bearing and seal. Not a nice thought.
However, if you could use a SAE-7-1/2 flywheel output shaft adapter with a long stubshaft running true, and support the far end of it with a ball bearing-pillow block, you might be able to eliminate the side wear on the rear engine bearing. I had one designed and built by Gardner with a 1-3/8 dia stubshaft and it should allow me to chose either sheave drive or direct drive. I will post more later when it arrives.
Tom
My understanding is you want to couple an 1800 rpm ST-3 to the Yanmar 2TNV70.
I would not recommend running that diesel at 1800 rpm it will be a shaker because of the odd firing of the 2 cylinders and could tear things up pretty fast. Those engines like to run loaded 2600 RPM's and up to 3600.
The sweet spot for those engines are Low side 2600, Ideal 2800, High side 3000 rpm's
Belt driving it would be the safest bet.
Henry
I forgot to mention that many Generator and APU manufactures like running these modern diesel engines around 200 rpm's over the peak torque curve. The reason is when the engine is loaded the RPM's drop and the engine will still be over the peak torque curve.
Henry
Quote from: vayidaho on February 24, 2013, 03:28:12 PM
I, too, have a 2NT70-HGE project going. I initially considered belt driven so the engine could operate at a higher speed for best torque. But, after consideration, I chose direct drive.
My thinking was that since Yanmar designed the engine plain, oil lubricated rear bearing for direct drive, any side thrust from belts would have to be supported by the oil film in the plain rear bearing...an iffy thing. I can imagine having to take down the engine after a few hundred hours to replace the rear bearing and seal. Not a nice thought.
However, if you could use a SAE-7-1/2 flywheel output shaft adapter with a long stubshaft running true, and support the far end of it with a ball bearing-pillow block, you might be able to eliminate the side wear on the rear engine bearing. I had one designed and built by Gardner with a 1-3/8 dia stubshaft and it should allow me to chose either sheave drive or direct drive. I will post more later when it arrives.
Tom
That engine can take a side load. Running double BX belts with the proper tension would be fine. And the side load would be less than a serpentine belt setup. Some APU Manufactures used that engine and they warrentee it for up to 4000 hours. http://www.truckgenerators.com/userguide.pdf
Henry
Quote from: hwew on February 24, 2013, 07:24:17 PM
My understanding is you want to couple an 1800 rpm ST-3 to the Yanmar 2TNV70.
I would not recommend running that diesel at 1800 rpm it will be a shaker because of the odd firing of the 2 cylinders and could tear things up pretty fast. Those engines like to run loaded 2600 RPM's and up to 3600.
The sweet spot for those engines are Low side 2600, Ideal 2800, High side 3000 rpm's
Belt driving it would be the safest bet.
Henry
Actually, I no longer plan to drive the 4 pole head direct. If I choose the ST head, I will use belts with the rear stubshaft support. I will run the engine at 2600 RPM as you suggest. My other thought is to direct drive a PMG through a Charge Controller to keep my 24 volt battery bank happy, and run my cabin off the inverter.
Thanks for the advice!
Tom
Your welcome Tom,
What PMG are you looking at?
PMG? Have not found one yet. I understand that George at UTTERPOWER used to make a pretty good one, but apparently it is no longer available. In the meanwhile, I found a self excited 2 pole 5KW Gen Head from BRANDNEWENGINES at a good price, so I will run the diesel at 2600 and the head at 3600 using belts, while I wait for a decent copper wound 1800 RPM ST to appear.
I tore my new ST head apart to confirm it was wound with aluminum as reported in another forum. Sure enough. And crappy solders where coils were connected. Also had an extremely loose coil which would have to be packed with RTV to keep from vibrating. So, it goes to the scrap dealer. Too much labor involved in trying to keep junk running. Besides, I never liked the open bearings. Too messy when heated up.
Got my flywheel adapter from Drew Yagelski at Guardian, 219-876-5248 at a very good p-rice for custom machining. Weighs 10.6 lbs, bolts to the SAE 7-1/2 flywheel, has a 1-3/8 stubshaft 5 inches long. He will make anything you need if you send him a sketch. The engine should benefit from more rotating mass at the lower speeds.
Tom
I have a Mec-Alt(spelling?)from that same supplier belt driven to a 2TNV Yanmar.
Henry is right on with his rpm recomendations. I run mine at 2640rpm and I think that would be the minimum for a good load.
Mine normally runs 4000-4500 watts thru the inverter-charger.
I have found that the voltage(from the gen head) drops quite a bit when loaded over 4500 watts.Sometimes down to 95-100v.Then the inverter spits the generator off.
I may try to re-pulley and get the engine up to2800rpm or so.
Quote from: vayidaho on March 01, 2013, 04:22:52 AM
..
I tore my new ST head apart to confirm it was wound with aluminum as reported in another forum. Sure enough. And crappy solders where coils were connected. Also had an extremely loose coil which would have to be packed with RTV to keep from vibrating. So, it goes to the scrap dealer. Too much labor involved in trying to keep junk running. Besides, I never liked the open bearings. Too messy when heated up....
Tom
Why not have a motor shop rewind it and get new bearings ? I just did new sealed bearings in mine - no heat issues with them, and much quieter now.
I considered that, but all the motor rewind shops in my hometown cannot work outside the box. If is not shown in their rewind manual, it cannot be rewound. Gone are the days of spirited initiative.
The few guys who "thought" they might be convinced to "try" to rewind it by following the old pattern, would not guarantee their work. I might rewind it myself if I find the time. I did it for a Harley-Davidson 125CC generator once before when I was 16 years old, and it worked. But that was almost 60 years ago....
vayidaho....George just happens to have a PMG for sale, along with a Lister engine. Check on his site.
dc
It is NOT a 3KW Utterpower MISSION CRITICAL PMG, it is a toy. Thanks for trying, however...
Quote from: SPSInc on November 19, 2012, 10:07:34 AM
Hello All -
A colleague of mine and I have been working on a Combined Heat and Power unit. As a disclaimer this is a project we are attempting to develop and market. We have some of the major components put together and have run some test data. We have decided to post some information to this forum to see if we can get some feedback on the concept and its performance.
We used a Yanmar 2TNV70 diesel engine and attached a 24 pole PMG generator. An electronic governor was installed on the engine so it can be controlled for variable speed to regulator the output of the PMG. We are able to get 8KW of electrical power out of the system @ 3600 RPM. We configured the unit for 48Vdc but could be configured for 24Vdc as well. During testing the output of the generator was roughly 54Vdc and 150Amps. We installed heat exchangers on the exhaust and engine cooling water.
Without getting too winded in the details here is what we were able to extract in heat and electrical energy running at full electrical output. The below data is based on a 160deg F input water temperature from the water storage tank.
Fuel Input: 0.7 gal/hr (2.7L/hr) = 93,000 BTU/hr
Electrical Output: 7.9KW = 27,000 BTU/hr
Exhaust Heat Captured = 12,000 BTU/hr
Engine Heat Captured = 30,000 BTU/hr
Sum of Electrical Energy and Heat Captured = 69,000 BTU/hr
System Efficiency = 74%
Our next step in the process is to package the systems in an enclosure and work on the automation. Thank you in advance for any feedback. I will post more as we move along and if any questions arise.
Regards, Eric
just checking in to see if this project has moved forward? looking to get a system ready for next years heating, power is would be a bonus!
Rich
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.
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.
Very Nice Indeed!