Solar- design and planning
I am probably going to add some solar to ease the load on our bank and
lower our genset run time. Our daily amp hour demand is close to 275
AH, yes, Maerin is a power hog. Our bank is 1200 AH, and when cruising
we generally must run our genset 3-4 hrs/day to keep the cycle to about
60% SOC (per battery monitor) with an extended run or marina stay about
every 2-3 weeks to give the batteries a full float. But it is such that
meeting it 100% with solar would exceed both the real estate I have
available as well as the budget, so I believe a reasonable objective
would be to reduce the genset run time. A 2 hr daily run would give us
enough run time to do what we need to do- water, hot water, laundry, and
recharge- all while keeping the genset well-loaded. Some fuel and
operating cost savings to be realized, but payback would probably be 2-3
yrs, not the primary consideration.
I'm doing lots of reading, trying to assimilate as much as possible.
Some decisions that I could use help with-
- Type of panel- will likely rack mount on PH roof, I'm not enamored
with the prospect of mounting on my bimini for mechanical concerns
plus shading from my radar array. My inclination is toward rigid
mono panels. - Number of panels- shading from stay & two antennas might make it
better to mount 4 smaller panels vs. 2 larger ones to reduce the
shading impact on the whole array. Layout of roof/clearances will
require mounting 4" above the surface. I'm looking at 300-400 watts
of capacity. - Controller- PWM vs MPPT and a single controller vs. a controller for
each panel, or perhaps a controller for 2 pairs if I use 4 panels-
to minimize the effect of partial shading. - Controller location- better closer to the panels or battery?
- Tie-in -
o I can tie the panels into my main distribution panel that has a
pair of 2/0 conductors to the main bank panel in the ER, tie-in
here would require about 20ft of cabling from the panel
o or- run about a #2 cable from the panels to the battery panel in
the ER, a cable run of about 45 ft.
I've been accused of over-thinking things, but my experience in my trade
has taught me that the best time to figure things out is long before the
tools come out.
Welcome any input.
Steve Sipe
Solo 4303 "Maerin"
Middle River, MD
Hello Steve.
A couple of comments that I hope will be helpful:
My panels are raised 2" above the deck. The benefits are twofold:
#1) Cooler panels perform better.
#2) Under my panels on the inside the overhead is significantly cooler.
Viking Star is the genius (and technical) regarding the differences between
MPPT and the less expensive controllers. Basically it's this:
At the FL/GA border I'm getting watts divided by three equals amps with a
cheap controller. So my 75 watt panel is giving me 25 amps per day.
Viking Star far further north gets the same watts divided by three equals
amps with his MPPT controller. So it buys you more amps in the end.
I wrote a couple of articles about my set-up. Here is one:
http://janice142.com/Articles/SolarRegulators.htm
DEFINITELY look for Viking Star's write up. His is far superior and gives a
lot of technical details.
As for me, I have my controller where visible. It pleases me to see what is
happening and I would not be happy with it buried in the bilges. If you
like checking on things have yours easy to view.
That's it from here. Good luck with your project.
Janice aboard Seaweed
http://janice142.com
And you're very correct saying "I've been accused of over-thinking things,
but my experience in my trade has taught me that the best time to figure
things out is long before the tools come out. Steve Sipe." I've already
added it to my Aphorisms collection, so thank you Sir.
On Sun, Aug 23, 2015 at 10:56 AM, Steve Sipe via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
I am probably going to add some solar to ease the load on our bank and
lower
- Layout of roof/clearances will
require mounting 4" above the surface. I'm looking at 300-400 watts
of capacity. - Controller- PWM vs MPPT and a single controller vs. a controller for
each panel, or perhaps a controller for 2 pairs if I use 4 panels-
to minimize the effect of partial shading. - Controller location- better closer to the panels or battery?
I'm starting my installation on Friday, planning four semi-flexible 100
watt Renogy panels with a single 40 amp MPPT controller located right next
to the batteries. We are mounting them directly to the new bimini top
because they are much lighter, although less efficient, than rigid,
especially when you tie in the framing and extra support, all in the
location on the boat where don't want extra weight. And we don't have
anyplace else to put them.
I was hoping to find some sort of system that would totally replace the
bimini top with solar panels, but no luck, so far.
I haven't decided for sure on the one vs two controllers. Another topic
that just cam \e up is the business of a backing panel under the solar
panels. Some say it is necessary.
I think this arrangement will take care of refrigeration and maybe hot
water while in the bahamas next winter, as I can run the water heater from
the inverter. yes, very carefully!
Jeff Janacek, on Adirondack,
a 36' Monk trawler
in Portsmouth, VA
On Sun, Aug 23, 2015 at 10:56 AM, Steve Sipe via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
I am probably going to add some solar to ease the load on our bank and
lower our genset run time. Our daily amp hour demand is close to 275 AH,
yes, Maerin is a power hog. Our bank is 1200 AH, and when cruising we
generally must run our genset 3-4 hrs/day to keep the cycle to about 60%
SOC (per battery monitor) with an extended run or marina stay about every
2-3 weeks to give the batteries a full float. But it is such that meeting
it 100% with solar would exceed both the real estate I have available as
well as the budget, so I believe a reasonable objective would be to reduce
the genset run time. A 2 hr daily run would give us enough run time to do
what we need to do- water, hot water, laundry, and recharge- all while
keeping the genset well-loaded. Some fuel and operating cost savings to be
realized, but payback would probably be 2-3 yrs, not the primary
consideration.
I'm doing lots of reading, trying to assimilate as much as possible. Some
decisions that I could use help with-
- Type of panel- will likely rack mount on PH roof, I'm not enamored
with the prospect of mounting on my bimini for mechanical concerns
plus shading from my radar array. My inclination is toward rigid
mono panels. - Number of panels- shading from stay & two antennas might make it
better to mount 4 smaller panels vs. 2 larger ones to reduce the
shading impact on the whole array. Layout of roof/clearances will
require mounting 4" above the surface. I'm looking at 300-400 watts
of capacity. - Controller- PWM vs MPPT and a single controller vs. a controller for
each panel, or perhaps a controller for 2 pairs if I use 4 panels-
to minimize the effect of partial shading. - Controller location- better closer to the panels or battery?
- Tie-in -
o I can tie the panels into my main distribution panel that has a
pair of 2/0 conductors to the main bank panel in the ER, tie-in
here would require about 20ft of cabling from the panel
o or- run about a #2 cable from the panels to the battery panel in
the ER, a cable run of about 45 ft.
I've been accused of over-thinking things, but my experience in my trade
has taught me that the best time to figure things out is long before the
tools come out.
Welcome any input.
Steve Sipe
Solo 4303 "Maerin"
Middle River, MD
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we cruise. "Trawler Time" is my new charter business, featuring the east
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charters out of Portsmouth, VA.
Steve,
We have no solar on the boat, for a variety of reasons. But we did have
it on the bus that served as our home for a decade before we hit the
water. Back when I was something of a figure in that community, I
lectured on the topic, and I do keep up with it so I am not too out of
date. See my comments in-line, below:
On 08/23/2015 10:56 AM, Steve Sipe via Trawlers-and-Trawlering wrote:
...
- Type of panel- will likely rack mount on PH roof, I'm not enamored
with the prospect of mounting on my bimini for mechanical concerns
plus shading from my radar array. My inclination is toward rigid
mono panels.
Rigid panels are the way to go. In the RV community, where the extra
height, weight, and fragility of rigid panels does make a difference, we
go around and around on this every few years. Flexible panels are simply
not there yet with regard to efficiency or longevity. You are wise to
realize that any shading at all will kill the output and thus you need
to install the panels well away from radar arrays, GPS mushrooms, and
the like.
- Number of panels- shading from stay & two antennas might make it
better to mount 4 smaller panels vs. 2 larger ones to reduce the
shading impact on the whole array. Layout of roof/clearances will
require mounting 4" above the surface. I'm looking at 300-400 watts
of capacity.
Larger panels will give you more watts per square meter, but if partial
shading might be an issue then you should take that into consideration.
Also, it is often the case that the size and shape of the roof as well
as any obstacles to a full-coverage, flat installation will mean you can
get more watts with many smaller panels rather than fewer larger ones.
Many installers do not realize that solar panels need ventilation space
below them. 4" above the existing roof is more than ample; make sure
there are no obstructions to the air flow below the panels.
Note that panel voltage is important. I recommend a minimum of 24-volt
(nominal) panels, even if your house system is 12 (I don't remember if
your boat was built before Selene went to a 24v house system). The
panels are more efficient and the panel wiring down to the controller
will be smaller gauge for the same drop.
We had 330 watts on the bus, which was just enough to keep the fridge
running full time and a vent fan on (thermostatically controlled), plus
a bit to keep the batteries topped off. We could park the bus for a
couple of weeks with food in the fridge while we went off on a cruise or
whatever and come back to full batteries and a cold fridge. YMMV.
- Controller- PWM vs MPPT and a single controller vs. a controller for
each panel, or perhaps a controller for 2 pairs if I use 4 panels-
to minimize the effect of partial shading.
MPPT, no ifs, ands, or buts. Lots of people skimp on the controller --
get the best one you can afford that meets or exceeds the size of your
system. A single controller will yield more overall power because
multiple controllers, like multiple regulators, can end up "backing off"
based on charge voltage generated by other controllers in the system.
Properly designed and connected panels should not propagate the shading
problem beyond the single panel that is partially shaded; if the panels
you buy do not have integral bypass diodes for this purpose they can be
added at the paralleling bus.
- Controller location- better closer to the panels or battery?
The controller will be able to use more of the available solar if it is
closer to the battery, all other things considered. But this is also
partly about wire gauge and voltage drop. Since most controllers are
dropping the PV voltage to meet house voltage, there will be less drop
overall if you have the controller closer to the battery as well. That
said, sometimes it's just not possible. Note also that the controller
does expend energy and has a heat sink, so keeping it out of hot
machinery spaces is more important than getting it closer to the batteries.
- Tie-in -
o I can tie the panels into my main distribution panel that has a
pair of 2/0 conductors to the main bank panel in the ER, tie-in
here would require about 20ft of cabling from the panel
o or- run about a #2 cable from the panels to the battery panel in
the ER, a cable run of about 45 ft.
This is a tough one. You want to do the math to minimize the ohmic
losses in the PV circuit. That said, the controller really needs to see
true battery voltage, so connecting it as close as possible to the
battery terminals will yield the best results, so long as it does not
introduce more drop.
I've been accused of over-thinking things, but my experience in my
trade has taught me that the best time to figure things out is long
before the tools come out.
More people under-think solar than over-think it, so I applaud you.
-Sean
m/y Vector
lying Wood's Hole, MA
http://OurOdyssey.BlogSpot.com
Steve,
Will pass on what we did, and perhaps some ideas on your questions:
Type/ number of Panels: The best value (in terms of $/watt) are the large
'house' panels. They all seem to measure around 39 x 65" or so and it
should be easy to locate panels for $1 / watt. I would say a common panel
today would be in the 260W range. (Ours are 245w, but are a few years old).
These are commonly made of in a way that 'looks' electrically like smaller
arrays in parallel. Example, our panels (REC-245w) are configured as 3
strings of 20 cells each. So in effect, it is 3x 82W panels mounted next to
each other and wired in parallel.
So, you could purchase some smaller panels and put them in parallel. You
gain some flexibility in placement, but if you place them physical next to
each other you have gained nothing in terms of shade protection. And you
will spend more money as the smaller panels are usually not as good a value
in terms of $/watt.
You should mount them were there is good air flow under them. They will get
hot and need a way to dissipate that heat. If you use them for an overhead
and want to put some covering on the bottom to protect the bottom of the
panels (panels are easily damaged physically from the bottom) try to make
sure it allows air flow for cooling.
MPPT vs. PWM will depend ultimately on the panel specs you get. If you get
a panel with a 'Monomial Voltage' of around 16v or so (assuming you have a
12v battery system), you can get away with a simple PWM controller. Larger
panels often have a nominal voltage of around 30v or more, and for those you
will really want a proper MPPT controller - else you will lose a lot of
energy due to inefficiency. However, if your boat is 24v, again you could
get by with a simple PWM controller. But even so, a proper MPPT controller
will always give better efficiency then a PWM controller. And by 'proper' I
mean one which is in effect a buck power supply -there are some Chinese
'MPPT' controllers which are actually simple PWM ones - so keep an eye out.
If you have a MPPT controller it would be best to locate the controller near
the batteries - or your main distribution panel. (more later). The idea
is to keep the '12v' wires as short as possible. As the panels will often
be at a higher voltage (e.g. 30v above) you will experience less loss over
the wires from the panels to the controller for a given wire size.
And for the tie-in point, I would say it would be fine to tie into the
distribution panel for several reasons (lower cost, less losses). Do make
sure the controller has remote battery voltage sensing though - and fuse
appropriately. I do not know if there is something in ABYC that would be
contrary to this, maybe someone else knows?
We installed two panels on our boat several years ago and are very happy
with them. You can read about our install here:
http://mvvikingstar.blogspot.com/search/label/Solar
http://tinyurl.com/ps6uwm2
And if you are interested, there is a way to accurately predict the solar
output - one of which I documented here:
http://mvvikingstar.blogspot.com/2012/10/solar-panels-on-boat-modeling-and.h
tml
http://tinyurl.com/lyxlco5
Hope this is of some help. Good luck, and let us know what you end up with!
-al-
Viking Star
45' Monk Sr. / McQueen
mvVikingStar.blogspot.com
In my experience, the flexible panels that have the "cover glass" made of plastic do not hold up as well as the glass-covered rigid panels. Sunlight eventually clouds the plastic and output falls off. If the flexible panels are allowed to flex in the wind, the panels may fatigue and crack, letting in salt and corroding in short order.
I'm a fan of rigid, aluminum framed panels. Either mono or poly crystalline are now reliable long-term.
Two controllers give you redundancy, a big plus if leaving the US and easy access to replacements. Heating water takes a whole lot of electrical energy; don't expect much heat from your solar electric system. But it can make a good dump for when the batts are full and the sun is shining.
Mark Richter
Ortona, FL on the Okeechobee waterway.
Sent from my iPhone
On Aug 24, 2015, at 6:00 AM, Tamaroak via Trawlers-and-Trawlering trawlers@lists.trawlering.com wrote:
I'm starting my installation on Friday, planning four semi-flexible 100
watt Renogy panels with a single 40 amp MPPT controller located right next
to the batteries. We are mounting them directly to the new bimini top
because they are much lighter, although less efficient, than rigid,
especially when you tie in the framing and extra support, all in the
location on the boat where don't want extra weight. And we don't have
anyplace else to put them.
I was hoping to find some sort of system that would totally replace the
bimini top with solar panels, but no luck, so far.
I haven't decided for sure on the one vs two controllers. Another topic
that just cam \e up is the business of a backing panel under the solar
panels. Some say it is necessary.
I think this arrangement will take care of refrigeration and maybe hot
water while in the bahamas next winter, as I can run the water heater from
the inverter. yes, very carefully!
Jeff Janacek, on Adirondack,
a 36' Monk trawler
in Portsmouth, VA
I remembered one more thing Tamaroak. Fryedaze did what you're planning and
as I recall there were issues with both heat and the bow of the panels. He
wrote an article for my website that can be found here:
- Self-induced Work (engine won't start)
http://janice142.com/Topics/GuestAuthors/Self-inducedWork.html by guest
author Dave Frye aboard Fryedaze. Dave and his wife Betsy are doing The
Loop. Their first day didn't quite go as planned. Dave shares with us the
how, why and, wherefores of what went wrong, and right, on Day One.*
*From the article: *
-
Captains Dave and Betsy Frye are traveling in a Monk42 built in 1989 by
Overseas Ltd. Visit their websites: * -
http://mvfryedaze.blogspot.com/ http://mvfryedaze.blogspot.com/ and
http://home.comcast.net/~davebetsy/site/?/home/
http://home.comcast.net/~davebetsy/site/?/home/ *
And now I'll hush. Really! (with apologies for the weird fonts)
J.
On Aug 24, 2015, at 6:00 AM, Tamaroak via Trawlers-and-Trawlering <
trawlers@lists.trawlering.com> wrote:
I'm starting my installation on Friday, planning four semi-flexible 100
watt Renogy panels with a single 40 amp MPPT controller located right
next
to the batteries. We are mounting them directly to the new bimini top
because they are much lighter, although less efficient, than rigid,
especially when you tie in the framing and extra support, all in the
location on the boat where don't want extra weight. And we don't have
anyplace else to put them.