Yanmar 2TNV70 CHP Project

[SPSInc]

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

[Henry W]

Hi Eric,

That looks very impressive. I hope to see pictures.

Henry

[LowGear]

Isn't slower better for life expectancy?

Casey

[SPSInc]

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.

[Henry W]

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

[veggie]

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

[SPSInc]

Here is a short video showing the unit running.

[RJ]

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

[SPSInc]

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.

[mr.fixit]

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?

[SPSInc]

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

[mr.fixit]

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.

[mr.fixit]

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.

[Mad_Labs]

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

[RJ]

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.