|
Home > Archive > Alternative Power sources > November 2005 > Using electric generator exhaust to heat water?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Using electric generator exhaust to heat water?
|
|
| stu@aaronj.com 2005-11-25, 10:21 pm |
| Here in South Florida we've had 3 hurricanes in a year.
I'm setting up a 3,500 watt generator on a shelf in my garage with the
exhaust tube through the wall to vent all the gasses outside.
I am looking to add a heat exchanger to capture some exhaust heat and
use it to warm water in my HW tank.
Suggestions of home-brew or off the shelf heat exchangers please.
| |
|
|
<stu@aaronj.com> wrote in message
news:1132968596.561358.220500@g47g2000cwa.googlegroups.com...
: Here in South Florida we've had 3 hurricanes in a year.
:
: I'm setting up a 3,500 watt generator on a shelf in my garage
with the
: exhaust tube through the wall to vent all the gasses outside.
:
: I am looking to add a heat exchanger to capture some exhaust
heat and
: use it to warm water in my HW tank.
:
: Suggestions of home-brew or off the shelf heat exchangers
please.
:
I believe it's highly unlikely you will be able to get enough
heat, regardless of the heat exchanger, to heat any amount of
water that would be usable, especially with a genset that small.
Besides that, it's highlt likely that the added back-pressure
from any sort of workable heat exchanger would upset the engine
tuning and you might end up wiht a pretty gunked up engine, not
sure.
No expert so I'll be interested in what others have to say, but I
doubt it would be worth the effort -
Pop
| |
| Ecnerwal 2005-11-25, 11:21 pm |
| In article <1132968596.561358.220500@g47g2000cwa.googlegroups.com>,
stu@aaronj.com wrote:
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
>
> Suggestions of home-brew or off the shelf heat exchangers please.
Simple off the shelf solution, ranges from free to expensive - either a
hot water boiler (aka furnace) of the oil or gas fired variety, or a gas
or oil fired hot water heater. Might be a bit difficult to find boilers
in Florida (at least free used ones). Very low restriction, so little if
any added backpressure. Tons of heat exchange surface in a boiler,
somewhat less in a hot water heater.
I have a cast-iron boiler waiting for me to get the rest of the "real"
system in place which will be applied in this manner to the exhaust of a
diesel genset. Intact, working, replaced by newer and more efficient
boiler, cost was hauling it away. 8 inch stove pipe on that, so I don't
think backpressure will be any trouble at all with a 1-1/2 to 3 inch
pipe exhaust in place of the oil gun. Heat output will obviously be much
less than with direct flame, but there's plenty of heat there being
wasted, so I expect it will be a worthwhile operation to extract it.
With any such exhaust plumbing work, considerable detail should be
applied to both reducing the odds of a leak, and detecting any such leak
before it can kill you. One way to help with that is to place the entire
generator setup in a separate shed away from the house, rather than in
an attached garage.
When I run my present gasoline generator "with the exhaust tube through
the wall to vent all the gasses outside", my level-indicating carbon
monoxide detector _always_ indicates some indoor pollution (5-15 ppm),
so all the gasses are not leaving, in fact. Several times, something not
obvious to a casual inspection has gone wrong with the system and levels
inside have become dangerous (50 to as much as 500 ppm) - I never run it
without the detector, and I have decided that the permanent setup will
be located in a separate shed, with a chimney. Screwing around with this
stuff can kill you, so I'm not screwing around with it.
--
Cats, coffee, chocolate...vices to live by
| |
| Harry Chickpea 2005-11-26, 12:21 am |
| "Pop" <nobody@devnull.spamcop.net> wrote:
>
><stu@aaronj.com> wrote in message
>news:1132968596.561358.220500@g47g2000cwa.googlegroups.com...
>: Here in South Florida we've had 3 hurricanes in a year.
>:
>: I'm setting up a 3,500 watt generator on a shelf in my garage
>with the
>: exhaust tube through the wall to vent all the gasses outside.
>:
>: I am looking to add a heat exchanger to capture some exhaust
>heat and
>: use it to warm water in my HW tank.
>:
>: Suggestions of home-brew or off the shelf heat exchangers
>please.
>:
>I believe it's highly unlikely you will be able to get enough
>heat, regardless of the heat exchanger, to heat any amount of
>water that would be usable, especially with a genset that small.
> Besides that, it's highlt likely that the added back-pressure
>from any sort of workable heat exchanger would upset the engine
>tuning and you might end up wiht a pretty gunked up engine, not
>sure.
>
>No expert so I'll be interested in what others have to say, but I
>doubt it would be worth the effort -
>
>Pop
>
I have metal five gallon pails that I've stuck in the path of the
exhaust of my 5KW generator. The water got fairly hot, but had that
distinct eau' de fumes that made it unusable. Then I found that the
lower element of my water heater was 4.5K watts. Two hours of direct
connection to the generator (with no other loads) made a nice 40
gallons of hot water. That is closer than I like to run to rating,
but seemed to work OK. You could get a small capacity electric water
heater with smaller elements and do something similar.
The more sane way to heat water down here is solar. With FPL's rate
increase, and tax breaks, the payoff period is beginning to make sense
again. If you must use gasoline to heat water, get a Coleman gasoline
camp stove. You won't wear out the generator and the efficiency is
better.
There is no way I'd run a generator in my garage. Getting all the
exhaust fumes out is one problem, getting out the gasoline smell is
another, dealing with the possibility of a fire is another, and doing
the regular oil changes that these generators need is yet another.
Even if all those problems are resolved, there is the throbbing noise
that I wouldn't put up with.
| |
|
|
<stu@aaronj.com> wrote
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
During the 5 days of terror last year after Charley, hot water was the last
thing on my mind.
In fact, at one point I was ready to murder everybody in order to get some
ice water.
jeezis it was miserable.
We set (4) 5 gallon buckets of water in the backyard and by 5pm we were
taking makeshift showers, well, in the shower.
| |
| nicksanspam@ece.villanova.edu 2005-11-26, 3:21 am |
| Ecnerwal <LawrenceSMITH@SOuthernVERmont.NyET> wrote:
>Simple off the shelf solution, ranges from free to expensive - either a
>hot water boiler (aka furnace) of the oil or gas fired variety, or a gas
>or oil fired hot water heater... Tons of heat exchange surface in a boiler,
>somewhat less in a hot water heater.
A gas water heater sounds like a nice off the shelf solution, with
the insulated pressurized tank and plumbing :-) Maybe Grainger's 1PZ64
Vanguard/Rheem 50 gal 140 pound $209 heater, listed at a 36K Btu/h input
with a 36.4 minute 90 F recovery time, R6.7 R-value, 0.58 "energy factor,"
and a 6-year tank warranty.
How efficient would that be with a $900 1500 W 90 lb Honda generator
that also makes 21K Btu/h of heat? Could we just plumb the generator
exhaust into the gas line?
Nick
| |
| nicksanspam@ece.villanova.edu 2005-11-26, 9:21 am |
| Ecnerwal <LawrenceSMITH@SOuthernVERmont.NyET> wrote:
>
>A gas water heater sounds like a nice off the shelf solution, with
>the insulated pressurized tank and plumbing :-) Maybe Grainger's 1PZ64
>Vanguard/Rheem 50 gal 140 pound $209 heater, listed at a 36K Btu/h input
>with a 36.4 minute 90 F recovery time, R6.7 R-value, 0.58 "energy factor,"
>and a 6-year tank warranty.
>
>How efficient would that be with a $900 1500 W 90 lb Honda generator
>that also makes 21K Btu/h of heat? Could we just plumb the generator
>exhaust into the gas line?
And block up the water heater's combustion air openings and the draft hood
and enclose the generator and water heater in a plastic film room in
the basement depressurized by the generator combustion air supply,
with the water heater flue pipe running outdoors?
And a CO detector.
Nick
| |
|
| I've seen it done with a smaller engine- just a simple heat exchanger with a
larger water pipe welded around about 2 feet of exhaust pipe and plumbed in
to a water tank to form a thermic syphon- after about 3 or 4 hours you have
a tank full of hot water. Simple technology that worked like a charm, and
worked for years with no maintenance.
<stu@aaronj.com> wrote in message
news:1132968596.561358.220500@g47g2000cwa.googlegroups.com...
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
>
> Suggestions of home-brew or off the shelf heat exchangers please.
>
| |
| Robert Morein 2005-11-26, 7:21 pm |
|
<stu@aaronj.com> wrote in message
news:1132968596.561358.220500@g47g2000cwa.googlegroups.com...
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
>
> Suggestions of home-brew or off the shelf heat exchangers please.
>
How about modifying a smallish gas heater, by piping the exhaust through the
heat exchanger?
I would use a separate heater for this purpose, permanaently removing the
burner, welding a new bell around the bottom of the heater.
Then put the whole thing outdoors for safety, as the others have noted.
| |
|
| stu@aaronj.com wrote:
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
>
> Suggestions of home-brew or off the shelf heat exchangers please.
Yup, can do. I know a guy who is doing it right now, works excellent for
him. He's running a lyster diesel and he pipes the exhaust into the **top**
of a 40/50 gal gas water heater and vents off the bottom (no burner in it
of course) He has so much hot water that sometimes he needs to drain some
off to cool it down if his demand is not high enough. I think his lyster
is about 6hp or so. I can send you more info (post your munged up email
addr and a note) or his contact info if you like.
Eric
| |
| nicksanspam@ece.villanova.edu 2005-11-27, 2:21 am |
| Eric <nospam@email.com> knows a guy who's:
>... running a lyster diesel and he pipes the exhaust into the **top**
>of a 40/50 gal gas water heater and vents off the bottom (no burner in it
>of course)
Using the top makes thermal sense, altho that seems to make the exhaust
plumbing more complex and potentially leaky. Where does condensation go?
>He has so much hot water that sometimes he needs to drain some off to cool
>it down if his demand is not high enough.
It would be nice to take care of that automatically, or avoid generation
unless there's a need for heat, in order to waste less fuel.
Nick
| |
|
| On 27 Nov 2005 00:30:27 -0500, nicksanspam@ece.villanova.edu wrote:
>
>It would be nice to take care of that automatically, or avoid generation
>unless there's a need for heat, in order to waste less fuel.
Easiest way is to keep two exhausts, just cap the end of the one you
don't want to use. With a bit of ingenuity a slide which can cover one
outlet but never two can be connected to a waxstat in the hot water
tank.
AJH
| |
|
|
<stu@aaronj.com> wrote in message
news:1132968596.561358.220500@g47g2000cwa.googlegroups.com...
> Here in South Florida we've had 3 hurricanes in a year.
>
> I'm setting up a 3,500 watt generator on a shelf in my garage with the
> exhaust tube through the wall to vent all the gasses outside.
>
> I am looking to add a heat exchanger to capture some exhaust heat and
> use it to warm water in my HW tank.
>
> Suggestions of home-brew or off the shelf heat exchangers please.
>
Lots of good ideas here, but putting an air-cooled generator inside isn't a
good one. Carbon monoxide levels will be marginal at best, the noise has
got to be intolerable after awhile. The fire risk is not only very real, but
it will probably cancel your insurance policy as well.
Liquid-cooled powerplants are a much better choice. The coolant can be
plumbed inside through radiators with very little risk to human health and
safety.
| |
| RF Dude 2005-11-27, 11:21 pm |
| Yeah... we are hobbiests that work within our means.... So having an air
cooled generator is a gimme at our price point. Improving overall
efficiency by using waste heat for hot water turns it into a co-generation
plant. By the numbers, these small engines are only about 15% efficient at
electricity out versus energy in. Does anyone know what the energy loss
split is between heat out the exhaust versus heat out the radiator?
| |
|
| In article <Xiuif.1427$wf2.126848@news20.bellglobal.com>,
"RF Dude" <post@thisnewsgroup.com> wrote:
> Yeah... we are hobbiests that work within our means.... So having an air
> cooled generator is a gimme at our price point. Improving overall
> efficiency by using waste heat for hot water turns it into a co-generation
> plant. By the numbers, these small engines are only about 15% efficient at
> electricity out versus energy in. Does anyone know what the energy loss
> split is between heat out the exhaust versus heat out the radiator?
>
>
The ROT (rule of thumb) for diesel engines is:
33% out the crankshaft
33% out the exhaust stack
33% out the cooling system
Me who cogenerates with 1800 rpm diesels..........
|
|
|
|
|