| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 722.1 | pricey and no bang.... | HYEND::J_BORZUMATO | | Wed Jul 25 1990 11:03 | 20 |
| I have no "hands on" experience. But i have over the last 4 yrs.
been looking into this.
What i've found is that the solar panels are expensive, and do not
put out enough to meet our needs.
Soooooooo i bought a 1kw portable generator. If we plan on staying
more than 2 days anywhere, i begin running it for 2 hrs. a dayt
beginning day 2. I charge batteries with the onboard charger,
and bring the 2 fridges onto 110v. (the fridges are the small
Norcold type. Beyond this, i found i can kick the hot water heater
for about 1/2 hour, and if needed i can also charge my handheld,
and other portable rechargable items. Also, if needed my wife
can run the vacuum and or fan.
From and $'s and cents point of view, the gen. is a better bang
for the buck.
JIm.
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| 722.2 | | FREEBE::FEUERSTEIN | If it isnt a SEARAY... | Wed Jul 25 1990 12:17 | 23 |
|
-<275 amp-hrs>-
Just how big is this battery,anyways??(physical dimensions)
I have two oversize deep cycle marine batteries and together
the amp-hours total only 210. I'm able to run the fridge,fans,
and lights from one battery nearly four whole days before
switching to the backup. It does take a long time to recharge
though. The only solar power charging setup I've seen has
been a trickle-charge variety. This probably would not help
you a whole lot. I don't have any details ' cause it was in
a magazine in some office I'd visited.
andy
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| 722.3 | how low do you go... | HYEND::J_BORZUMATO | | Wed Jul 25 1990 12:22 | 3 |
| Andy, you must run it down to "dead" before switching ???
JIm.
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| 722.4 | | THEBUS::THACKERAY | | Wed Jul 25 1990 12:36 | 14 |
| The trickle charge variety of solar panels are useless, they will not
even keep up with the battery's internal discharges.
You need an Arco solar panel, which will give you about 3-4 charging
amps on a regular basis. You may consider buying two panels, at about
$650 from Boat US, although you can find them at about $250 each if you
look in the magazines.
That will cover your charging requirements nicely, for when you are
away from dock.
Cheers,
Ray
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| 722.5 | | FREEBE::FEUERSTEIN | If it isnt a SEARAY... | Wed Jul 25 1990 15:12 | 20 |
|
-<pretty low>-
Jim,
On those long weekends,I do run it down to
almost death. The deep cycle batteries are
designed to be able to recover. On normal
weekends I don't take them that low. The
indicators show from 50-70% charge depending
on how much company I've had on the boat.
Andy
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| 722.6 | | SEARAY::EAST | | Thu Jul 26 1990 19:28 | 12 |
| There's a company in Seattle that has a wonderful "how-to" catalog that covers,
among other things, using solar panels.
Cruising Equipment, Inc
6315 Seaview Ave NW
Seattle, WA
(206) 782-8100
Their catalog is amazingly complete. Not much in the way of specific products,
instead, it's 60 pages or so of "to do this...use this".
Jeff
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| 722.7 | Sun & Refrigeratorse | SSGVAX::REDFIELD | | Fri Jul 27 1990 11:31 | 19 |
| As pertains to my "perceived" need I though about a generator prior to
purchasing the third battery. There really wasn't enough room for a
poratble and doing a permanent installation was much too costly when one
considers fuel inatke and exhaust requirements.
The battery seemed to be my best bet. It is pretty large ( the battery box
is about 1X1X2.5) and well mounted in the bilge between the two engines.
It is wired into the stbd alternator with appropriate isolation from the
starting batteries.
The application has been great. I am not sure, however, how much of the
alternator's output goes to this battery vs the stbd starting battery and
though to enhance the process utilizing a solar approach.
If solar generated output is negligible I wouldn't bother, of course.
On the other hand if I can generate say 10 amp-hrs/day that would be a nice
addition to the ole charge when I show up on the weekend.
Carl
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| 722.8 | DEJA VUE | FREEBE::DUCLOS | RON DUCLOS | Fri Jul 27 1990 13:44 | 8 |
| I thought I saw in one of the recent issues of either Motorboating
and Sailing or Boating magazines an article on exactly what you
are trying to accomplish. It talked about using solar charging,
inverters,etc. in the marine environment. I will try to find the
articles and could send you copies.
Ron D.
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| 722.9 | Offshore, August issue | GOLF::WILSON | Because the Earth is 2/3 water | Tue Jul 31 1990 11:57 | 10 |
| The August 1990 issue of Offshore magazine has an article on inverters
for converting 12VDC to 120VAC. The same issue also has a good article
on marine batteries and maintaining your boat's electrical system, and
includes a small sidebar on solar charging.
Offshore is sometimes hard to find at the magazine rack - if you would
like a copy of these articles send me your mail stop.
Rick
GOLF::WILSON
|
| 722.10 | quantitative data | MSCSSE::BERENS | Alan Berens | Tue Jul 31 1990 18:14 | 157 |
| Here are the results of an approximate quantitative analysis of the
total power that can be obtained from a solar panel. The results are
interesting.
On page 6-2 of the Elecro-Optics Handbook, RCA Corporation, 1968, there
is a graph of the spectral energy distribution of the sunlight
vertically incident on a horizontal surface at sea level. This graph
plots the incident energy (in watts per square meter per Angstrom) as a
function of the wavelength of the light. The light below the visible
(the infrared) is ineffective in producing electricity using solar
panels. A rough numerical integration of the energy distribution in the
visible and ultraviolet regions of the spectrum provides an estimate of
the power (sunlight) available for conversion to electricity by a solar
panel. This estimate is:
508 watts per square meter
47.2 watts per square foot
(Note: Though I used three significant figures in my calculations, I
doubt the numbers are accurate to much better than 10 to 20%. The amount
of sunlight reaching the earth varies some plus/minus 3.5% from the mean
depending on the distance between the earth and sun.)
This is an estimate of the practical MAXIMUM power that can be obtained
from a solar panel since it is for:
the sun vertically overhead (ie, minimum path length through the
atmosphere)
a 'standard' clear day
Smog, haze, clouds, and fog can reduce the intensity of the sunlight by
a factor of 10 or more (absorption and scattering is an exponential
function). A 'standard clear day' means a day with visibility > 14.6
miles. An 'exceptionally clear day' is one with visibility > 37.3 miles.
Such days are all too rare (which is why they're exceptional). On an
exceptionally clear day the incident power is very approximately 50%
greater than on a standard clear day.
Every day life indicates (and scientific research confirms) that
sunlight is less intense when the sun is not directly overhead. From
Figure 6-2 in the Electro-Optics Handbook the following data can be
derived:
altitude of sun relative solar energy on
(deg) a horizontal surface
0 0.6%
10 8.8%
20 22.2%
30 37.9%
40 53.8%
50 68.5%
60 82.3%
70 91.1%
80 96.8%
90 100.0%
(This data is for only the visible spectrum, but it is convenient to use
the data for visible and near ultraviolet light.)
From this data, it is obvious that output of a solar panel will vary
significantly with time of day, so the question is: how much?
Using standard celestial sight reduction equations and data from the
Nautical Almanac, the altitude of the sun can be easily determined as a
function of time-of-day.
hours before/after altitude of sun (deg)
local noon @ 42 deg 30 min latitude latitude =
solstice equinox declination @ solstice
0.0 70.9 47.5 90.0
1.0 67.2 45.4 76.2
2.0 58.7 39.7 62.5
3.0 48.3 31.4 48.8
4.0 37.4 21.6 35.4
5.0 26.3 11.0 22.1
6.0 15.6 0.0 9.1
7.0 5.4 -3.4
8.0 -4.0
Most of my sailing (cruising) is done in June, July, August, and
September between Marblehead (42 deg 30 min north latitude) and Maine.
So the sun altitudes at 42 deg 30 min N latitude on the solstice and
equinox provide an approximate maximum and minimum for my sailing. When
the observer's latitude is the same as the latitude of the sun -- the
sun's declination -- the sun will be directly overhead at local noon.
The third column gives the data for latitude 23 deg on the solstice.
The data from the two tables above can be combined to estimate the solar
light intensity as a function of time-of-day:
hours before/after percent of maximum sun intensity
local noon @ 42 deg 30 min latitude latitude =
solstice equinox declination @ solstice
0.0 91.7 64.9 100
1.0 88.9 61.8 94.9
2.0 80.6 53.3 84.7
3.0 66.0 40.2 66.9
4.0 49.7 24.4 46.6
5.0 31.8 10.0 25.2
6.0 15.8 0.6 7.9
7.0 4.2
The area under these curves is proportional to the total watt-hours of
solar energy available.
solstice 360 watt-hrs per square foot per day
equinox 206 watt-hrs per square foot per day
zenith 352 watt-hrs per square foot per day
(Since these calculations are rather tedious, I haven't done any others.)
It is interesting to note that, to some extent, the longer days in the
higher latitudes compensate for the reduced intensity of sunlight.
Unfortunately, solar panels are not 100% efficient. An Arco 42 watt
solar panel has an area of 3.84 square feet. This implies a light to
electricity conversion efficiency of 23%. (This higher than I would have
guessed -- perhaps Arco's ratings are conservative).
For a 42 watt Arco panel (23% conversion efficiency) charging a battery
at 12.6 volts the number of amp-hrs per day from the solar panel will
be:
solstice 25
equinox 14
zenith 25
Assuming I've done all the number crunching correctly on my HP
calculator, these results are not partcularly cheerful for anyone hoping
to supply much of his/her electrical needs from solar panels. Unless, of
course, one is very frugal with electrical consumption and a profligate
spender of money for panels. These results assume, again, a standard
clear day. Here in New England, really clear days are not as frequent as
one might like. Solar panels on a boat on a mooring cannot be kept aimed
at the sun. About the best one can do is place them flat on the deck
with minimal shade.
Note that the gain in panel output by facing the panel directly at the
sun isn't as great as you might expect. As the sun's altitude decreases,
the path length of the sunlight through the atmosphere increases. On an
exceptionally clear day, the atmospheric transmittance for the sun at an
altitude of 30 degrees is about 60% of the transmittance with the sun
directly overhead. Since the intensity reduction is an exponential
function of path length and attenuation coefficient, intensity decreases
rapidly with decreasing visibility and with decreasing sun altitude.
From this data you can estimate the probable amount of battery charging
you can expect from one or more solar panels. It certainly appears the
the cost per amp-hr of charging capacity is quite substantially higher
for solar panels than other other means (at today's prices). For
example, an Arco 42 watt solar panel (25 amp-hr per day) is about $350.
A 400 watt portable Honda generator with a 110 vac battery charger
(around $500 new) will supply over 600 amp-hr per day.
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