Airport Power
Kyle Boatright
hangar. I need it for my 125 watt preheater if I'm taking an early-morning
flight in the winter, and will use it for a .25A trickle charger if I've let
the aircraft sit for more than a week or two.
The problem is that my T-hangar doesn't have power. One of the other hangar
renters had electrical service pulled to his hangar, and sublets 15A
breakers for $15/month = $180/year, which is a bit much for me, considering
my needs are for a dollar or so of electricity a year.
Any suggestions other than either buying a small generator or paying the
$15/month?
I'm asking because the "power guy" complained last week when I ran a
dropcord to a neighboring hangar for an hour last week to run the trickle
charger...
KB
JKimmel
--
J Kimmel
myn...@whereIwork.com
www.metalinnovations.com
"Cuius testiculos habes, habeas cardia et cerebellum." - When you have
their full attention in your grip, their hearts and minds will follow.
Kyle Boatright
"JKimmel" <myn...@whereiwork.com> wrote in message
news:bJadnYkz-P8AHTnZ...@centurytel.net...
> Kyle Boatright wrote:
>> I need a trickle of electrical power about a dozen times a year in my
>> hangar. I need it for my 125 watt preheater if I'm taking an
>> early-morning flight in the winter, and will use it for a .25A trickle
>> charger if I've let the aircraft sit for more than a week or two.
>>
>> The problem is that my T-hangar doesn't have power. One of the other
>> hangar renters had electrical service pulled to his hangar, and sublets
>> 15A breakers for $15/month = $180/year, which is a bit much for me,
>> considering my needs are for a dollar or so of electricity a year.
>>
>> Any suggestions other than either buying a small generator or paying the
>> $15/month?
>>
>> I'm asking because the "power guy" complained last week when I ran a
>> dropcord to a neighboring hangar for an hour last week to run the trickle
>> charger...
>>
>> KB
> Put a static inverter in your car.
>
> --
> J Kimmel
> myn...@whereIwork.com
> www.metalinnovations.com
Typically, I need power when I'm *not* at the airport. The preheater, for
instance, needs 3-4 hours to heat the engine a reasonable amount. Go by the
airport the night before, set the timer to turn on the preheater at 5AM, and
when I get to the airport the next morning, the engine is nice and toasty.
The trickle charger is worse, it probably needs power for 12 continuous
hours to do a whole lot of good.
I could install a piper style power receptacle on the airplane for cold
starting, but I'd prefer to have a cheap trickle of 120v power..
KB
ji...@specsol.spam.sux.com
> KB
A 125 watts isn't a trickle.
The battery you could take care of with a solar charger for RVs and
other seldom drive vehicles for about $20.
--
Jim Pennino
Remove .spam.sux to reply.
BTIZ
> I'm asking because the "power guy" complained last week when I ran a
> dropcord to a neighboring hangar for an hour last week to run the trickle
> charger...
>
> KB
Tell the "power guy" to stick it.. I'm sure the airport manager and the
power company would be interested in his selling of power at a premium. I'm
sure the drop cord you ran for an hour, you had the permission of that
hanger renter. I'm sure all of his connections from the 15amp service board
to all the other hangers are up to code?
BT
David Lesher
>I need a trickle of electrical power about a dozen times a year in my
>hangar. I need it for my 125 watt preheater if I'm taking an early-morning
>flight in the winter, and will use it for a .25A trickle charger if I've let
>the aircraft sit for more than a week or two.
Well, you can handle the trickle with a solar array of some kind.
The preheater, not quite.
Engineering out loud:
125W @ 8H = 1KWH
At 13.8 VDC; 72 Ah-H w/100% efficiency.
Say 150 Ah-H at real world inverter levels.
If only you had a 13vdc preheater, a deep cycle battery could
do the trick.
Hmm, you could use Qnty 9-10 13.8v batteries in series; 4 Ah-H
Gel-Cells are not all that pricy. Looks to be ~~$15 each for 5Ah-H.
Then a kludge to parallel them when charging off the array.
This assumes the preheater is unswitched; a regular AC thermostat
may not break DC correctly...
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
Vaughn Simon
"Kyle Boatright" <kboat...@comcast.net> wrote in message
news:UradnSyHoYgq6znZ...@comcast.com...
>
> Any suggestions other than either buying a small generator or paying the
> $15/month?
This 45 watt solar panel kit:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599
Plus a GOOD charge controller (not the one that comes with the kit) plus two
T105 golf cart batteries, plus an inverter will turn the trick. You would only
use the inverter for preheat, charging your battery directly. The kit even
includes 12V. lights for your hanger. Of course, for that money you could pay
the "electricity guy" for two or three years.
Vaughn
B A R R Y
>
> Any suggestions other than either buying a small generator or paying the
> $15/month?
Solar?
Ross
It is interesting that you are worried about your battery for just a
couple of weeks. That thing should maintain a charge for a month or
more. But a solar panel would work. There is a large up from investment,
but you could go with solar panels, inverters, and deep cycle batteries.
It does work, but the materials are expensive depending on the watts you
are wanting. I think my pre heater is 250 watts. One probe in each
cylinder and one in the oil pan. But, my hangar is wired.
--
Regards,
Ross
C-172F 180 hp
KSWI
e.dr...@nyetspam.verizon.net
probably provide 125 W (10 amps from a 12 V battery) for 6 hours or so. Use
a 12 V heater or a 125 VAC heater through an inverter. You would charge the
battery at home between uses.
As other have suggested, a solar panel might work for trickle charging.
-Elliott Drucker
mrob...@worldnet.att.net
>"Kyle Boatright" <kboat...@comcast.net> writes:
>>I need a trickle of electrical power about a dozen times a year in my
>>hangar. I need it for my 125 watt preheater if I'm taking an early-
>>morning flight in the winter, and will use it for a .25A trickle charger
>>if I've let the aircraft sit for more than a week or two.
>
>Well, you can handle the trickle with a solar array of some kind.
I agree. If you can mount the solar panel so that it has about the same
angle from horizontal as your latitude, and so that you can get to it
occasionally to wipe the dirt off of it, it will work a little better.
>125W @ 8H = 1KWH
>At 13.8 VDC; 72 Ah-H w/100% efficiency.
>Say 150 Ah-H at real world inverter levels.
In a later post, David said he only needed to run the heater for about
4 hours. I haven't measured any of them, but I can believe that a
really cheap inverter might only be 50% efficient. Tripp Lite claims
that their 150 W inverter is about 89% efficient at full load [1], and
another site [2] gives about the same numbers.
So, to get 125 W of AC to the heater, the inverter will need about 140 W
of DC input, or about 12.2 A at 11.5 V. (This is an average; the battery
will start out at around 12.5 V and shouldn't be run much lower than
10.5 V.) This is 48.8 Ah at the four hour rate. Powersonic [3] claims
that their 60.0 Ah/20hr gel-cell battery will do 48.0 Ah at the 4 hour
rate. Flooded batteries often have a "reserve capacity" rating, which
is the number of minutes they will run a 25 A load. Since your load is
about half of this, you would look for one with a 120 minute or better
reserve capacity rating. Interstate [4] says their SRM-24 will support
a 15 amp load for 4.6 hours, so that would work.
But wait! All of those ratings are at "room" temperature - 20 C for the
gel-cell and 27 C for the flooded battery. The curves for the gel-cell
battery show that its capacity at 0 C is about 90% of the 20 C capacity,
and its capacity at -20 C is about 65% of the 20 C capacity. So, at 0 C
you need a gel-cell with a nominal rating of 66.7 Ah/20hr or better, and
at -20 C you need one with a nominal rating of 92.3 Ah/20hr or better.
The flooded battery doesn't have curves like this, but looking at the two
cranking amp ratings, the rating at -18 C is 80% of the rating at 0 C.
If you ass-u-me that it follows a similar curve as the gel cells, the
SRM-24 might still cut it at 0 C (3.9 hours), but for -20 C, you
probably need to move up to the SRM-29 (6.4 hours at 27 C, derated to
4.0 hours at -20 C).
None of these batteries can be taken lightly. The gel-cells will weigh
40 to 70 pounds and the flooded ones will weigh 50 to 60 pounds. If you
have a choice, buy a battery that has a built-in handle. This becomes a
consideration if you're taking the battery home to recharge it every time.
You could put it on the solar panel, but it'd take a long time to charge
back up at 0.25 A - something like 200 hours of full sun, or three weeks
straight if you live in Phoenix.
If you do use a battery and an inverter, keep the wiring as short as
possible, but especially the DC wiring. I would cut off the cigarette
lighter plug that comes with most small inverters and wire the inverter
directly to the battery terminals. Anything that you can do to keep the
battery warm would also help; a plastic battery box that isn't sitting
right on the floor would help. For the extension cord from the inverter
to the heater, use as heavy and as short a cord as you can. It's only
about 1 A at 120 V, but since this electricity is relatively expensive,
you don't want to waste it if you can help it.
>Hmm, you could use Qnty 9-10 13.8v batteries in series; 4 Ah-H
>Gel-Cells are not all that pricy. Looks to be ~~$15 each for 5Ah-H.
>Then a kludge to parallel them when charging off the array.
This would work too; you don't lose anything in the inverter, but as you
noted, it may be harder to control. With one big battery and an
inverter, you can use a regular 120 V AC lamp timer to turn the heater
on when you want it. With this setup, you'd probably use something like
a spring-wound timer with a switch or relay rated for DC.
For ten batteries at an average voltage of 11.5 V each, you'd need
1.09 A from each battery for four hours, or 4.35 Ah/4hr. This is at
least a 7.0 Ah/20hr nominal gel-cell at 20 C or 0 C, or a 9.0 Ah/20hr
nominal at -20 C. These batteries together will all weigh 60-65 pounds,
but at least you can carry them two or three at a time instead of all
at once. It would still take a few weeks to charge all of these
batteries off of an 0.25 A solar panel.
Either gel-cell option will probably cost around $150 for the batteries;
the flooded battery option will probably cost around $80. The inverter
should be about $30 or so. There are chemistries like NiCd and NiMH that
have higher energy density, i.e. they don't hurt as much when you drop
them on your foot, but they also have much higher dollar density as well.
There are places that sell "solar kits" for cabins and other isolated
applications. They usually have the solar cell(s), charge controller,
mounting hardware, and some cable. Some of them include an inverter;
you get to buy your own batteries for most of them. Googling on "cabin
solar kit" or looking at the ads in "Home Power" magazine are good ways
to find systems like these.
Another possible source of power might be a wind generator, but this
probably wouldn't be too practical unless it's really, really windy
close to the ground; towers are expensive and you probably don't want to
stick it too high up in the air at the airport. Maybe you could put it
down low, by a busy taxiway, and convert prop wash into free juice... :)
If what you're really after is heat, the best answer is often to burn
the hydrocarbons fairly close to where you want the heat. That probably
wouldn't work very well in this situation, though. I had some other
creative ideas, like a weight on a rope that turned an alternator pulley,
but that turned out to require way too much weight.
Standard disclaimers apply; I don't get money or other considerations
from any of the companies mentioned.
Matt Roberds
[1] http://www.tripplite.com/products/product.cfm?productID=2553
[2] http://www.solar-electric.com/solar_inverters/inverters_for_solar_electric.htm
[3] http://www.power-sonic.com/techman.pdf
[4] http://www.interstatebatteries.com/www_2001/content/products/product_marine.asp
nrp
Garden tractor batteries (about 20 AH) go on sale at like $15 each. As
an alternate, you may even be able to collect used batteries from a car
repair shop. Connect them in series and run the heater from DC to
avoid the losses of an inverter.
You don't even need a full 120 V if the heat demand isn't that high.
Maybe better blankets and say 60 V for 12 hrs would do the job?
Another approach is to use a Dragon heater which requires propane and a
small amoount of 12 V power.
bill...@verigy.com
solutons--which require implementations using your time
at $0.05/ hour.
I'd guess your heater draws > 125 watts when cold, too.
For the next level, figure out a way to turn it on remotely!
Bill Hale who does it with X-10 but is looking for a cell
phone solution!
I'd be surprised if
Kyle Boatright
"bill...@agilent.com" <bill...@verigy.com> wrote in message
news:1151766335....@m79g2000cwm.googlegroups.com...
> The $15/mo is cheap compared to all these battery
> solutons--which require implementations using your time
> at $0.05/ hour.
>
> I'd guess your heater draws > 125 watts when cold, too.
Could be. The point is that I need a little bit 'o power once every once in
a while. As everyone has mentioned, batteries and an inverter are a
solution, but are capital intensive.
The real deal would be to pay the "power guy" a the airport a one time fee
of, say, $50 for my occasional use via drop cord. I inquired about that
once, but he was a pretty big a-hole about it.
>
> For the next level, figure out a way to turn it on remotely!
>
There is a way to do it remotely (a pager works), but I have two timers in
series so IF I know I'll be flying on a particular day, I can turn set the
heater to come on once (and for whatever duration I need) during a 14 day
period. Since I work 15 minutes from the airfield, it isn't a huge problem.
> Bill Hale who does it with X-10 but is looking for a cell
> phone solution!
KB
David Lesher
>Check at Wally World to find batteries with the most AH per dollar.
>Garden tractor batteries (about 20 AH) go on sale at like $15 each. As
>an alternate, you may even be able to collect used batteries from a car
>repair shop.
All batteries are not created equal. 'Starting' batteries are
ill-suited to deep-cycle service. You can use "marine/RV/cycle"
batteries if available. Note "Gel-Cells" [tm] come in both "float"
and "cycle" versions; you'll want the 2nd.
.Blueskies.
"bill...@agilent.com" <bill...@verigy.com> wrote in message
news:1151766335....@m79g2000cwm.googlegroups.com...
> For the next level, figure out a way to turn it on remotely!
>
> Bill Hale who does it with X-10 but is looking for a cell
> phone solution!
>
X-10.com has some sort of remote call in box gizmo thingie to do this....
Ron Rosenfeld
>David Lesher <wb8...@panix.com> wrote:
>>"Kyle Boatright" <kboat...@comcast.net> writes:
>>>I need a trickle of electrical power about a dozen times a year in my
>>>hangar. I need it for my 125 watt preheater if I'm taking an early-
>>>morning flight in the winter, and will use it for a .25A trickle charger
>>>if I've let the aircraft sit for more than a week or two.
>>
>>Well, you can handle the trickle with a solar array of some kind.
>
>I agree. If you can mount the solar panel so that it has about the same
>angle from horizontal as your latitude, and so that you can get to it
>occasionally to wipe the dirt off of it, it will work a little better.
If he is going to use it to run his heater, then he'd be better off
mounting it steeper -- say latitude + 15° -- since most of his power needs
would be during the winter months.
>
Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)
Kyler Laird
>The real deal would be to pay the "power guy" a the airport a one time fee
>of, say, $50 for my occasional use via drop cord.
You'd attend while using the drop cord, right? And you drive a car to
the airport? 'seems like it'd be a whole lot easier (and less expensive)
to buy a cheapo inverter (because waveforms and noise won't matter to
your heating element) to use from your car.
If you really only need 125W something like this should do the trick.
http://www.target.com/gp/detail.html/sr=1-1/qid=1151859215/ref=sr_1_1/602-4546155-7958254?%5Fencoding=UTF8&asin=B000157TNA
Even a 400W unit costs less than two years at $50.
http://www.target.com/gp/detail.html/ref=sc_ri_2/602-4546155-7958254?%5Fencoding=UTF8&asin=B000157TNK
I suspect that once you have one of these you'll find a lot of other
uses for it.
If using your car for power is problematic and you're considering a
generator then consider getting a tug with an electrical system (lawn
tractor) instead. Plug an inverter into that and you'd have a handy
dual-use device. Heck, if you rig it with a nice 12/24V battery
charger, inverter, lights and an air pump you could probably rent it
to others on the field.
--kyler
Ron Rosenfeld
Kyle,
Where are you located and do you have an unobstructed southern exposure for
solar panels? Could you south facing solar panels on the roof of your
hangar?
In Georgia, to set up a reliable solar system that would meet the
requirements you outlined above will probably cost about $500. Maintenance
would be to check the battery water at appropriate intervals (a few times a
year).
It might be less expensive to run a line from your neighbor's hangar, and
pay him a few bucks a month.
Kyle Boatright
"Kyler Laird" <Ky...@news.Lairds.org> wrote in message
news:i3bln3-...@snout.lairds.com...
> "Kyle Boatright" <kboat...@comcast.net> writes:
>
>>The real deal would be to pay the "power guy" a the airport a one time fee
>>of, say, $50 for my occasional use via drop cord.
>
> You'd attend while using the drop cord, right? And you drive a car to
> the airport? 'seems like it'd be a whole lot easier (and less expensive)
> to buy a cheapo inverter (because waveforms and noise won't matter to
> your heating element) to use from your car.
>
Again, the problem is that a pre-heater and/or a trickle charger need hours
to do their thing. Trying to run either from a car ain't gonna cut it.
<<<<snip>>>
.
>
> --kyler
Doug
generator would do it, but it's expensive and needs gas and
maintenance. The only other thing that makes sense is to run your own
power hookup to the power company. But find out what THEIR minimum is
first. If it were me, I'd pay the $15, or do without. Solar, battery
etc is all in the hobby area. Fine if you want to mess with it, but not
a cost effective solution.
Kyler Laird
>Again, the problem is that a pre-heater and/or a trickle charger need hours
>to do their thing. Trying to run either from a car ain't gonna cut it.
Yup, I sure did miss that. Let's find the "ain't gonna cut it" part.
125 watt heating element
inverter with 90% efficiency
Much better are available.
roughly 44 amp-hours available from regular 12V starter battery
A dual-purpose deep-cycle/starter battery would be much better.
125W / 90% = 139W = 12V * 11.6A
50 amp-hours / 11.6A = 3.5 hours to "discharge"
Hmmm...I'm still missing it. How many hours do you need to leave it
without starting the car? What are you doing at the airport all this
time?
And why would you run a trickle charger when you have a car available?
--kyler
Kyle Boatright
> "Kyle Boatright" <kboat...@comcast.net> writes:
>
>>Again, the problem is that a pre-heater and/or a trickle charger need
>>hours
>>to do their thing. Trying to run either from a car ain't gonna cut it.
>
> Yup, I sure did miss that. Let's find the "ain't gonna cut it" part.
>
> 125 watt heating element
> inverter with 90% efficiency
> Much better are available.
> roughly 44 amp-hours available from regular 12V starter battery
> A dual-purpose deep-cycle/starter battery would be much better.
>
> 125W / 90% = 139W = 12V * 11.6A
> 50 amp-hours / 11.6A = 3.5 hours to "discharge"
>
> Hmmm...I'm still missing it. How many hours do you need to leave it
> without starting the car? What are you doing at the airport all this
> time?
I don't want to be at the airport for any lengthy period of time. That's why
I'm looking for a power solution in lieu of paying the "power guy" $180/yr
for a buck or two of electricity.
> And why would you run a trickle charger when you have a car available?
Because jump starting an airplane isn't the most enjoyable thing in the
world. Cords, spinning props, etc. make it a process that could lead to a
dumb accident.
KB
>
> --kyler
>
Kyler Laird
>I don't want to be at the airport for any lengthy period of time.
That was my first question. ("You'd attend while using the drop cord,
right?") So the answer is "no." No problem. You could still buy a
deep cycle battery, charge it in your car and then pull it out to use in
the hangar. It should be able to run your 125W heater for several
hours.
Not quite as elegant but still a way to be independent of "the (power)
man."
>> And why would you run a trickle charger when you have a car available?
>Because jump starting an airplane isn't the most enjoyable thing in the
>world.
I don't have a problem with it. I just start the engine on the opposite
side of the nose from the charge port. Maybe it's your plane that's the
problem.
>Cords, spinning props, etc. make it a process that could lead to a
>dumb accident.
I still don't see how a "trickle charger" changes any of this. Do you
leave it on when you turn the prop? Then you still have "cords,
spinning props, etc." If not, then why would you leave a fast charger
(car) connected when you spin the prop?
Connect the car. Load and do your preflight. Put the car away. Start
the plane. What am I missing?
--kyler
nf...@home.com
purpose of generating heat - but it is certainly do-able. Were I to
decide to go this route I would find some sort
of a DC heating element to use - thus avoiding the expense and
conversion loss of running an inverter. If your winter flying is
infrequent you could figure your recharge time to be a week or more,
and thus size your solar array accordingly (and save upfront cost in
the process). I have had great success with using solar battery
maintainers in my airplane and also in a seldom-used vehicle.
This past winter I tried a different approach to preheat. AC was
available - with a long extension cord - and I had a couple of the
"cube" style ceramic heaters laying around. I picked up a couple of
dryer duct flanges and duct taped these to the business ends of the
cubes. Then I took an 8' dryer hose, cut it in half and attached the
halves to the cubes.
Feeding the heat to the engine by way of the cowl flap openings, I let
this rig run for half an hour with temperatures in the 20s. I have no
idea what the engine temperature was after this treatment, but it did
start immediately - just like in warm weather. If no AC is available,
one could power heaters of this sort with an inverter in a car. It
would take
a large one - 3 KW or so for a pair running on high. It occurred to me
that a couple of
cheap ($10 at Walmart) hair dryers might do the job just as well (the
wattage is similar - about 1500) - but I haven't had the opportunity to
try it.
David Johnson
Ron Rosenfeld
>I would hesitate to recommend solar panels and batteries for the
>purpose of generating heat - but it is certainly do-able. Were I to
>decide to go this route I would find some sort
>of a DC heating element to use - thus avoiding the expense and
>conversion loss of running an inverter.
For a building, I would definitely agree. For an a/c block heater, though,
one's choices are more limited. And 125W is a fairly modest load.
The issue, though, is whether the OP wants to jury-rig a heater for his
a/c, that might be only usable with a DC supply, versus perhaps he has
something already installed, which can be used at other airports, with an
AC source.
He'd really have to do some cost comparisons to determine the most useful
and economical method.
Since he already has a heater, the question would be whether purchasing or
fabricating a second heater, which would only be used in his hangar, and a
controller to avoid overcharging his a/c battery (he already has a charger)
would be more or less expensive than a small inverter and perhaps slightly
more panel than might be required without an inverter.
I still think that the economics would favor a few bucks a month to his
neighbor, and a long extension cord :-).
Kyler Laird
>Were I to
>decide to go this route I would find some sort
>of a DC heating element
What kind of heating element *doesn't* work on DC?
--kyler
Ron Rosenfeld
wrote:
Obviously, any resistive load will heat up if you put DC voltage to it.
But now you've got me thinking.
What are the design considerations for converting a heating element that
has been designed to function on 120VAC to 12VDC?
For example, I have a TANIS system in my a/c which draws about 375W @
120VAC.
It consists of four heated intake bolts, and a heated oil screen. It works
very well and heats the entire engine to 75-100°F on below zero F days
(with a cover).
I'd guess, as a minimum, I'd have to rewire everything to handle ten times
the current, depending on whether or not the 120V wiring is oversized, or
not. That might (or might not) add sufficient weight to have to do a new
W&B (A&P and logbook entry required). Obviously have to change the
connectors, too. How simple would it be to attach the larger wire to the
bolts and engine oil screen?
Will the heating elements handle a continuous (DC) as opposed to an
intermittent (AC) current? Or will I need some kind of
controller/thermostat?
I'd also want to retain the ability to run on AC, so I'd need some kind of
additional connector -- probably paralleled with the AC connector.
What about the AC neutral/ground? If that gets upset in the rewiring, I'll
wind up blowing GFCI breakers when I use AC.
??
Kyler Laird
>Obviously, any resistive load will heat up if you put DC voltage to it.
>But now you've got me thinking.
>What are the design considerations for converting a heating element that
>has been designed to function on 120VAC to 12VDC?
Note that I wasn't suggesting using 12VDC. I was thinking in terms of
an equivalent voltage DC. That would not require any changes to your
installed system.
I'm really not even suggesting using DC; I was just pointing out that
the heating elements can handle it. Nine 12V batteries in series should
give approximately the equivalent power to a resistive load as 120VAC.
It could be done but it'd be a pain.
I think you'd be happier using a special-purpose (cheap,
high-efficiency) inverter on a single 12V battery. You could have a
noisy 400 Hz inverter and it would be perfectly fine for your heating
elements.
...or you could just buy a decent general-purpose inverter and use it
for powering a video projector for late-night drive-in movies at the
hangar when the weather is nice.
--kyler
Aaron Coolidge
: What are the design considerations for converting a heating element that
: has been designed to function on 120VAC to 12VDC?
: For example, I have a TANIS system in my a/c which draws about 375W @
: 120VAC.
You wouldn't convert it. You'd just hook it up to ~125 VDC. It will work
great. You may have trouble if it has an electronic thermostat (SCR/TRIAC)
because these require the reversals of the AC voltage to stop conducting
(you can turn on a TRIAC with DC across it, but you have to interrupt
the current flowing to shut it off).
--
Aaron C.
Kyler Laird
>You wouldn't convert it. You'd just hook it up to ~125 VDC. It will work
>great. You may have trouble if it has an electronic thermostat (SCR/TRIAC)
>because these require the reversals of the AC voltage to stop conducting
>(you can turn on a TRIAC with DC across it, but you have to interrupt
>the current flowing to shut it off).
Good point. Do any engine heaters have electronic thermostats though?
I was under the impression that they limited themselves simply with the
increased resistance of the heating elements at higher temperatures.
--kyler
Ron Rosenfeld
Ok, I see what you have in mind.
So instead of a 12V DC PV system and 12V batteries, we would set up a
120VDC system and batteries. Depending on the batteries, some fancy wiring
would be needed also to do the trickle charging for the a/c battery.
I suspect the costs of setting up a low wattage 120VDC system would be
excessive compared with the 120VAC system.
I did find a 4.5W 12V thin film solar panel for $45. You'd need 10 of them
in series and they only have a 2 year warrantee. That's $450 without
putting together a 120VDC battery bank.
Sunwize makes a 5W panel available for $68.60 with a twenty year warrantee,
which is closer to the "industry-standard". You'd still need ten of them
for $686.00.
Then for batteries, you'd need to size them, too, appropriately. I guess
with the 60 cells a 120VDC battery would require, I'd want to use a sealed
AGM or Gel Cell or some other maintenance free battery bank. Then you'd
have to check the rating at the discharge rate. If the heater draws 1A for
four hours, and you have a deep discharge battery that you can draw down
50%, you'd need to figure the battery capacity at that current draw.
(Battery capacity changes depending on current draw). I see a 12AH 12V AGM
battery for $15.95. At 0°F and drawing 1.12A, it has a capacity of 8.16AH.
A four hour heating run would draw it down to 50% capacity. There's
another $159.50.
Since he's not running the heater every day, (I'm assuming once/week), the
array should replenish the batteries after a few days of sunshine.
Of course, when you get into PV systems with a nominal voltage of greater
than 50V, there are a variety of NEC code requirements to be complied with.
They are safety related but, if he's at a public airfield, there may be
inspection fees and a requirement for a licensed electrician.
I still think the 12VDC / Inverter system will be less expensive than the
120VDC system when all is said and done. It may or may not be cheaper than
running a line to a nearby hangar and paying for the electricity, depending
on those costs.
For an AC system you could save money by using larger panels. ($/watt
decreases as watts increase). I see a 12V 30Watt panel that would meet the
requirements for $178.20. A Trojan 27TMX 12V 105AH (20hr rate) battery is
$118.25 and you'd only need one of them.
So for panel and battery we're at just under $300 for battery and panel. I
see 300W inverters available for as low as $27 but I'd guess $100 would
purchase a more reasonable unit. Add mounts, wiring, etc. and we're
probably close to the $500 I originally guesstimated for the system, versus
probably double that for the 120VDC system.
Ron Rosenfeld
wrote:
I forgot to mention that the pricing source I used was
http://home.altenergystore.com/
You can probably find stuff a bit cheaper, although when I've purchased big
ticket items from them, they have matched any advertised price I've seen on
the web.
And sure, you can build your own PV panels from scrap for a lot less; you
can also build your own batteries; but unless you're a real tinkerer and
doing it for fun ...