diesel co gen with PV assist..

freddy · November 2016

just bouncing this off everyone lol
i wan to run a kubota 8kw diesel gen utilizing the waste heat to warm my home and charge a battery bank.i have radiant floor heat in all three levels of my house. im thinking twin 4448 magnum inverters, 8 415 surrets @48v and a 3000 watt solar package in series the gen is sized for heat requirements 140000 btu of fuel per hour @ 90% load the engine will be loaded by electric hot water tank filled with glycol.im thinking 2 glycol and one for DHW. i will be off grid but with NG for cooking and heating and close drying and DHW i would like less than 3 hour run time on the gen in the winter and there is 5 months here for sure. the summer i anticipate 0 run time utilizing the sun as my prime power generator.. good sun light hours in the spring /summer... so hit me with ideas or opinion thanks freddy in sunny but cold alberta

jonr · November 2016

With NG, I'd consider a NG generator. You can store ~100K btu/hr x 3 hr in water tanks - say 350 gallons.

freddy · November 2016

welll we had a forest fire and guess what the gas was shut off... so the basement flooded .. so that's why diesel heating oil . i was considering ng there is more btu in diesel .. the delivery charges make ng more expensive,,, the power costs 1.00 per kWH ..there is an option i was thinking is NG injection.. still not decided ..thanks

mcgivor · November 2016

There will be losses that will have to be taken into consideration such as engine cooling, exhaust and electrical generation losses, not to mention wear and tear and maintenance.. A diesel engines thermo dynamic efficiency is in the region of 50% and the fuel efficiency drops exponentially, as load increases. Scavenging waste heat from the exhaust and cooling systen adds complexity. Solar water heating on the other hand is efficient and quiet when using the vacuum tube type collectors, however the initial cost can be high.Just some thoughts.

jonr · November 2016

Since you will be using the generator a lot, it's worth optimizing it for efficiency and wear. Usually around 1800 rpm/85% load/~50% rated output. Not clear to me what off-the-shelf device exists to divert current to a water heater as the batteries become fully charged and amps drop off.

freddy · November 2016

@mcgivor..of course losses to be expected ,case studies are saying 90 % fuel usage so by that i mean, 30 electrical 30 water jacket,and 30 exhaust and the fuel consumption is directly related to load,, exhaust temp run 900 f i would check your source about the efficiency of a diesel as it is very efficient and far from dropping efficiency exponential .google kubota model 1005 hp graph .. fuel consumption is also listed and the climate where i'm at, the is 4 hour of low angle sun ,, and temps of -40 so we need fuel in the winter to live.

@jonr the gen is sized for the heat value, specific fuel consumption is 1 gph, fuel has 140 000 btu the house has a 120000 btu NG furnace it is sized correctly. i am anticipating 3to 4 hours run time per day, one hour every 5 hours in this time period im am thinking the batteries will take a big gulp of current .the demand on the glycol tanks will decrease as the thermostat is satisfied and the battery voltage will increase thus shutting off the gen.. there is quote" You can store ~100K btu/hr x 3 hr in water tanks - say 350 gallons. "so that should get me my time period between generator stat stop cycle
anyway thanks for the ideas.. keep them coming... ..

mcgivor · November 2016

Thought I would include an attachment which describes some of the fundementals, pretty scientific stuff but thought it may be of help. Exponential simply means a curve rather than a linear rate of consumption. If what you are proposing is to use the excess electrical energy production and divert that to energy storage, I apologize for the miscommunication and yes 4 hours of low sunlight is not much, Ft Mc Murray area I'm guessing, you have to burn fuel, no doubt at minus 40, C or F is the same.

freddy · November 2016

@MCGIVOR..GOOD STUFF.. DEEP LOL I INTEND TO GRAB THAT WASTE HEAT.. AT LEAST THATS THE PLAN..
THANKS

mike95490 · November 2016

You might look at, and try to get registered at the Micro Co-Gen forum, where much has been discussed and tried
http://www.microcogen.info/index.php PM me here if you can't get past the spambot protections

jonr · November 2016

Your batteries should accept about 6000 watts (20K btu) of bulk charging power. Engine life will be better if you can run at less than 3600 rpm. Perhaps others can talk about occasionally getting the batteries through a complete absorption charge.

Pet peeve: using % load when % of rated output is meant. One can have 100% load at only 1000 rpm.

freddy · November 2016

@jonr,, ya i be using a 4 poie so rpm be 1800 nice and quiet.. and engine will run 90 % of rated kw as to get exhaust heat ..iam hoping for a run time of 4 hours or less about 4 gallons of diesel = 560000 btu per day i do have a wood stove also. just not real sure of battery bank sizing and pv sizing im thinking 3000 pv and 8 x 400 amp hour surrets?? bulk charging with the gen and finish with solar?

oil pan 4 · November 2016

You know you can take a diesel engine generator and run it off diesel and natural gas right?
Stationary power generation is the ideal application for diesel/natural gas.
Then if you you turn off the natural gas it just goes back to being a normal diesel engine.

freddy · November 2016

@oil pan yup i was looking for a injector kit that incorporated control module and some feed back, ie exhaust temp and intake mass flow.. but cound not find i understand they NG will cut 50 % of the diesel i would be happy to find some thing that fits the bill

freddy · November 2016

one other item im wondering about is ac or dc coupling ..with the magnum inverter.. it doesn't look possible.. can i rectify and transform the generator to dc ? and add this to the battery bank? thus getting 12 kw?

mcgivor · November 2016

www.sigmathermal.com
Google the above for exhaust hear recovery.

oil pan 4 · November 2016

I found the perfect application for generator waste heat recovery.
http://ecomodder.com/forum/showthread.php/fast-warm-up-ideas-exhaust-heat-exchanger-29085.html
Take off medium and heavy duty EGR coolers. They are cheap, made of stainless steel, purpose built to recover heat from a diesel engine exhaust stream via liquid working fluid such as water or antifreeze.

You can make a AC to DC power supply to power up your battery bank and inverter.
To get 10 to 12kw would take a huge transformer.
I did something like this on my solar inverter hybrid genetator.
I took a 1kva 380vac to 28vdc industrial control transformer, hooked up to 240vac to produce 22vac, rectified the AC to DC then sent the 22v DC to a morning star 30a PWM charger. To provide 25 amps of 12v power for charging and running the 900w kisae pure sine inverter and charging the 100ah AGM battery.

jonr · November 2016

> and engine will run 90 % of rated kw

Consider getting a larger engine such that you can get the heat you need while running at 50% output and a low rpm (say 2300). There will be less engine wear.

Also consider fewer but longer runs by using more water storage. Fewer cold starts will result in less engine wear (engine oil doesn't work well until it is up to ~160F).

freddy · November 2016

@jonr as a 40 year diesel mechanic i cant agree with your idea.. diesel wont make any exhaust heat with light loads , i want hard a run to heat my glycol storage and charge batteries and then shut off and a 4 pole gen wants 1800 rpm for 60 hertz and case studies iv read suggest sizing the engine for heat not current requirement. and running 80 to 100 % load .
6k is a lot of continuous power for a house.. but i do agree with the large storage cap. and less run time between heating cycles..

mcgivor · November 2016

Freddy mentioned running a diesel engine at its optimal load/RPM, this usually coincides with the peak torque of the engine, thus givIing the best fuel economy , over or under this threshold results in wasted fuel. So purposefully attempting to reduce RPM in an attempt to gain efficiency and wear reduction can in fact have the reverse effect.

Case in point, if I drive my pickup which is a 2.5 liter diesel at 80 Kmh in 5th gear rather than in 6th it actually shows on the fuel consumption gauge that I would use less fuel in 5th, To be fair the torque band is pretty broad, being that it has variable turbo technology developing 403 Nm between 1500 and 2500 RPM, but the point is maintaining the RPM within the torque peak actually uses less fuel.

Diesel engines are inherently torque engines and need to be loaded, this is the reason heavy trucks and locomotive prime movers are generally diesel.

oil pan 4 · November 2016

Even at idle the exhaust gas temperature will be around 400°F.
The diesel engine is only going to be around 1/3 efficient to putting fuel to shafts power.
The rest is waste heat.
So you willhave some where around 90,000 BTUs of waste heat for every gallon of fuel.

A Kubota diesel on a 6kw generator will burn around 1/3 gallon of fuel per hour with a 2kw load.

If you need more heat burn some natural gas.

jonr · November 2016

> engine will run 90 % of rated kw
> diesel wont make any exhaust heat with light loads

I suggested 85% load - which isn't light.

It is most efficient to run somewhere around (but not exactly) the rpm that provides peak engine torque. Which requires running at much lower than the engine's peak output rpm. And much lower than the engine's peak output. About 2300 rpm on a Kubota 1005. Lower rpm (like 1800) will have have slightly lower efficiency.

If a generator runs a Kubota 1005 at 1800 rpm (it's rated to 3000 or 3600 rpm) then it is running well below the engine's peak output rpm and at most, 52% of rated engine output. This will be a rpm that produces low engine wear. Keep the engine load reasonable (50+% is certainly enough) and there will be plenty of exhaust heat.

If you actually meant that the 1800 rpm generator (not the engine) will run at 90% of rated output, then we agree.

https://www.dieselenginemotor.com/kubota/super05/D1005

> If you need more heat burn some natural gas.

I agree. once you have enough to supply the electricity you need, just switch on your NG furnace.

Estragon · November 2016

3000 watts of panel s/b okay for 400ah 48v batteries. That said, you haven't said much about loads (electric or heating).

mcgivor · December 2016

Been reading a lot lately into what you propose to do as it is what I would be attempting, recovering as much of the otherwise wasted energy and converting into something useful. Read the specs on your Kubota and it has an impressively flat torque curve throughout the rev range, was supprised that it has an over square bore stroke, unlike most with a longer stroke. From all the information I've seen, the exhaust is where the most waste occurs, around 25%, the water jacket around 5% with others being lower.

Read an article where a generator was used in freezing conditions and the waste cooling system heat was used to preheat the induction to help maintain efficiency, as we know diesels do not like to run cold, an exhaust heat recovery was used for heating, much the same as you are going to do, wish I had saved the link so I could pass it on, can't seem to find it again but if I do will forward it to you. There is quite a lot of information on large scale and rather complex systems bot not much on the small scale, although information is not knowledge, the principals can be applied.

mcgivor · December 2016

Some more useful information

mike95490 · December 2016

mcgivor said:

Some more useful information

Nice, Exhaust Gas Heat Recovery for I.C.E. But you can't preheat the intake air too much, or you loose density, and then loose power.

Dave Angelini · December 2016

Freddie, I have a fur hat like yours even in California. The mountains here are cold this time of year. The pix is of up North of some trackers with Canadian Solar panels. The long summer hours are perfect for tracking, if you have the loads. The people in the building are doing production mining.

oil pan 4 · December 2016

Don't preheat the diesels intake air unless it's below 20°F. Test preheating if the intake air is between 20°F and 40°F.
Preheating the intake air above freezing doesn't help most engines.

Dave Angelini · December 2016

Preheat never hurt my Isuzu sailboat diesel in 90F seawater with 95F+ air

oil pan 4 · December 2016

Warmed air doesn't hurt the engine it just reduces power output and fuel economy.

mcgivor · December 2016

@freddy More to ponder

freddy · December 2016

@mcgivor thas sweet.. i was going to use a EGR cooler form a cummins ISX ...

diesel co gen with PV assist..

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