Changfa Slow Speed Experiment

[Wizard]

Redo this test with redstone at 1330ish rpm with head at 1800 once have correct pulley?

Cheers, Wizard

OOPS!

Change Redstone for changfa and my question applies, been awake too long overnight twice. 

Cheers, Wizard

[Veggiefuel]

Wizard,

Aaaahhhh!
Now it makes sense.

Easy to get the two mixed up. Both are excellent powerhouses 

Veggie

[mobile_bob]

harvesting and putting to use low value heat is certainly a challenge
radiant heat from the engine, genhead, piping etc, add up to significant btu's, but
not generally high enough in temp to do much real work, except for space heating.

the smell of diesel and oil limit that use though, wives and kids don't seem to have the same
appreciation for either

have you considered a compressor/freon heat pump system

iirc you have a fully enclosed genset, maybe an evap in there could take our the low value heat, move it
where it is usefull and leave the smell behind?

in any event it will certainly improve the quality of the heat, so it could also be used to preheat domestic water
in times where domestic space heating is unneeded?

i am using a sanden rotary compressor and plan on driving r22 to do just that, i figure why not take all the waste heat
and put it to use?

i wanna try and grab all the waste heat normally left to flitter away.

anyone else going that route?

bob g

[mobile_bob]

we need a totally new forum dedicated to micro co/trigerneration

there are lots of forums for the big boys, that build cogens in the megawatt class
and there are forums for commercial manufactures of mid and small size units, but

to my knowlege there is no such thing for micro units designed and built by individuals
at least that i am aware of, at least none that are serious about doing so.

there are literally dozens of approaches to this subject, everything from heat pumps, exchangers
and heat pipes

all which are within the ability of a relatively sharp guy in a home shop in my opinion.

and there is literally tons of parts, bits, and pieces ready made and ready to be adapted for our uses.
as well as many good how to books written to make these technologies a reality.

one can certainly buy all the parts, assemble, and fit a heat pump system, and if forced to hire an hvac guy to
come out and evac/charge the system.

for that matter a complete system can be removed from a car at a wrecking yard, without the loss of refrigerant
all in one piece given enough time and some persistance, i know because i have done it.

an old ford wagon with an r12 system can produce about 20-25kbtu without much problem
and about 50 percent more if it is recovered, flushed and the oil changed, and r22 used instead or r12.

anyway i digress

still looking for a micro cogen forum for the home built guys

bob g

[Veggiefuel]

Guys,

Have look at this Yahoo group dedicated to home CHP systems.
It has a very small membership, but if enough of us interested users signed up, it might liven things up !

http://tech.groups.yahoo.com/group/HomeCHP/

Veggie

[Veggiefuel]

Jens,

Re:  "Don't forget that it's easy to draw heat from a 185F tank but a lot more difficult when you are down to 80F"

I too have been thinking about that lately.
Heat transfer in a fan coil is closely related to CFM passing through the coils.
One solution I thought of was to put a 3 speed fan on the fan-coil unit.
At first, when there is a high temperature delta, the fan comes on at low speed, then when the temp drops to 130f it speeds up to medium speed. When the temp reaches 100f is shifts to high speed. Effectively giving the same BTU's throughout the run.

Would not be very hard to rig up.

Veggie

[Veggiefuel]

You might find this post interesting.
The Volvox exhaust gas heat exchanger.
have a look....

http://tech.groups.yahoo.com/group/HomeCHP/message/22

Here's the Volvox/Listeroid CHP website...
http://www.volvoxengineering.com/

Veggie

[ronmar]

Jens,

Thanks for the tips.
I currently have a 100 gallon H2O tank. The shop space I am heating is only 625 sq.ft. and based on 185 deg.f water and a 10,000 btu/hr fan coil I suspect I could run the heater for 5 to 6 hrs (through the night) before the water tank temp drops to 80 deg. f.
I'm learning as I go and when it comes to generators and diesels, this forum has been a big help.

PS: My calculations for a 4 hour heat recharge are based on having a fairly efficient exhaust/water heat exchanger. Know where I can get one ??   

Veggie

Yeah, that isn't much square footage ... but it does get a bit chilly out your way
Don't forget that it's easy to draw heat from a 185F tank but a lot more difficult when you are down to 80F ..... but you are right, it all depends on what you are after.
One thing I am trying to figure out (and maybe it's not cost effective) is how to utilize the available heat better. For example, you can use 80F water for heating but that same 80F water poses a problem for domestic hot water. If one could somehow set up to utilize the colder water where it can still do the job and reserve the hotter water where it is needed then efficiency could improve. Oh well, just rambling on .....

Re heat exchanger .... Bob will have some plans for us real soon now (I hope). His design promises a self cleaning action which seems to be much more important than I had realized. Those are just the plans and not the full unit though .....

Jens

About the best use for 80F water is for radiant heating.  You don't want the loops that hot, as it is a gentle wide area heat.  Have you seen the solar shed article?  Here is a link.   http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

Interesting and very descriptive setup by the author, including BTU calcs.  In his system, he used a thermal regulating valve that only mixed in enough hot water from the storage tank to maintain his desired radiant loop temperature.  Eventually as the tank temp dropped with the heat being put into the house, the thermal reg valve would mix in greater and greater qantities of storage tank water.  Once the tank reached a set low temperature, it would shutdown for he night, and his other domestic heat source would take over to maintain house temps.  With a heat storage tanks natural tendency to separate by temperature, a small loop and heat exchanger could be used to keep a domestic hot water tank "topped off" untill it's temperature dropped below 120F.  But with a thermal reg valve, the entire tank volume would be available for radiant heat untill say 80F was reached.  

We are in the process of planing our new home, and a very large thermal storage tank(750-1000 Gal) is in the basement area plan.  Ideally, if I can collect enough solar, this will meet the heat loads of the house(should be low with super insulated 15" thick walls), and maintain the domestic water temp.  I have a plan for a very low cost solar collector in my head that I am going to prototype this summer.  Maybe $3 per sq/ft, VERY efficient, and very easy to produce at home...  Ideally, I hope to be able to collect enough solar on a sunny day, for that days needs, and perhaps 2 days after that.  I am cooking up a chip wood fired boiler using a heat exchanger design I have had bouncing around in my head for the past year or so, as a cloudy backup for the solar system.  The fallback will be electric, but only as a last resort if something in the system fails, as electric is the least cost effective option.  The real key is the house insulation envelope, and to just plain need less from the beginning...  

Thanks for the link Veggie, I will have to check it out.  I think a CHP forum or section is an excellent idea.

[Veggiefuel]

ronmar,

Don't forget to tap your Lister(oid) into that system somehow.
You can make a lot of heat when charging a battery bank at 3kw/hr or during a power outage on a cloudy day.

I signed up at that Yahoo CHP site. Lets get it rockin' !!

Veggie

[mobile_bob]

what i would be most interested in, in a forum is "quality" not "quantity"

one post that clearly presents for instance a test protocol, that was clearly illustrated, closely adheared too
and which results were laid out in an understandable format, that is credible and reproduceable by others
is worth far more than 500 posts that go all over the place, with faulty, false or inflated claims.

personally i just find it hard to believe that we need to accept less, or rather why we do?

for instance, test equipment
most everyone accepts the killawatt meter as being adequately accurate for test purposes, a pair of which can
handle everything the typical 6/1  can throw at them, and they are low cost.
a decent surplus gram scale is pretty cheap as well, leaving maybe a  10 dollar stop watch to time events?

electric kitchen cooktop elements are dirt cheap from the bone yard and make for easy load bank parts,

all one needs then is to agree to a test protocol, then we got "apples to apples" and can make sense of what works
and what don't, and perhaps more important why it works or why it don't?

so maybe a scratch built low volume forum fixated on serious testing and results might be useful? i have to belive it would slowly
attract those that are trying to exact the best out of what they have?

just a thought

it might even be better to link up a set of websites with a common theme or goal, and allow each the ability to develop in their
specific area of interest or expertise.

it just seems like maybe there are a few folks that are about tired of reading yet another account of "how the lifter turns"
or "like sand through my crankcase, so are the days of our lives"
and are ready to take the next step?
whatever that is?



bob g

[Veggiefuel]

Jens,

That's quite a "system". Be careful it doesn't start thinking on it's own !! 

[lowspeedlife]

Maybe we should be asking for a new section to this forum for CHP ideas?

   Scott R

[Veggiefuel]

most likely posted before, but here's a couple of Listeroid CHP systems....

http://www.youtube.com/watch?v=YArccvSb9s8&feature=channel_page

http://www.youtube.com/watch?v=UAZKxYZ3QH0

[ronmar]

ronmar,

Don't forget to tap your Lister(oid) into that system somehow.
You can make a lot of heat when charging a battery bank at 3kw/hr or during a power outage on a cloudy day.

I signed up at that Yahoo CHP site. Lets get it rockin' !!

Veggie

Yep, just shy of 18,000 BTU/HR at a 3KW electrical load(from the cooling system)  The exhaust should also yield just about as much heat at that load...

[Jim Mc]

Hi Bob,

I stand by my post, but I’ll take a shot at clarifying.   And concede that I did make an approximation…

while i agree he is limited by engine power, the head is not maxed out.
at unity power factor (for the sake of discussion) theoretically all the kva generated go to making useful work, measured in kwatts

Agreed.

if however the powerfactor of the load drops to .7 there is a significant amount of power kvars? that is doing no useful work?
this power is circulating between the alternator and the load, creating nothing but heat

Ummm… Sort of.  Here’s the area where precise language is really beneficial.  The thing is that, yes there is extra current flowing (circulating as you say) but it doesn’t equate to heat in the magnitude you might be thinking.  Some heat, to be sure, but I’ll leave it to you as to whether its significant…

Here’s an example that may help put it into perspective.

Let’s say he needs 2.6 kW, but he has a 0.7 PF, as you say. 

At 120V, this means his line current is 31A.  (If he had a  perfect 1.0  PF, his line current would be 22A)

So, clearly, the line current is higher with the low PF.  But how big of a problem is this? 

The 31A is still within the rating of his 5kW ST head, so no problem there.

Now, If you’ll allow me to pull a number out of my ass, I’d like to estimate the resistance in the ST head stator windings and wiring to the load.  And I’m going to estimate it at 0.3 ohms.  (Actually this is not a total rectal extraction – My 12 kW head is 0.1 ohms if wired for 120V, which I doubled to 0.2 ohms for this case, plus I added 0.1 ohms for an assumed 100 feet of 10AWG copper wire to the load)

Thus, in the 0.7PF case, the total power lost as heat in the ST head winding, and copper wire due to I2R loss is 31^2 * 0.3 =  290 Watts

Now, in the 1.0PF case, we have 22^2 * 0.3 =  150 Watts

So, yes, some power is being lost due to the poor power factor. (290-150 = 140 extra Watts lost)

This 140 Watts of loss, compared to the 2600W being delivered represents about 5% of the engine’s output power.

Significant?  You decide.


BTW, your first post said this

at .7 pf you might only be able to cover about 1.8kwatt of loading

Which is way out of whack, based on the analysis I show above.  And it indicated to me a misunderstanding where  you multiplied 2600W by the 0.7 PF.  This is irrelevant, and not the correct approach to this problem.