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Solar panels

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glivs
Admiral

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USA
836 Posts

Initially Posted - 02/16/2008 : 19:38:05

I've been reading and trying to decide whether to go for a flexible (and convenient) or rigid (and efficient) solar panel. I created a simple power budget spreadsheet and was really surprised by just how much power our original anchor light and electronics consume. We are on a mooring so some changes in our power use and battery maintenance protocols are needed.
<ul><li> To plan and size our system, I assume that any panel is only probably 50-60% efficient on average for a variety of reasons. For those of you who have done this, how many days of solar charging do you plan for to recover one day of energy consumption. </li><li> Dedicated so-called smart chargers vary their voltage output in an effort to gain a 90-95% capacity charge. Do solar voltage regulators perform a similar function? I assume they must reduce their voltage output to keep from overcharging wet cells but how effectively? Should I plan on an 85% capacity charge or better? </li><li> Larry, I like the mount for your rigid panel that you designed but in your photos your OB is not tipped up. How do you accomplish that when your panel is deployed? </li></ul>
Thanks.

Gerry Livingston, Malletts Bay, VT
"Great Escape" 1989 C-25 SR/WK #5972

Edited by - on

OLarryR
Master Marine Consultant

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USA
3441 Posts

Response Posted - 02/16/2008 : 20:22:33

I designed my mounts so I would have enough clearance to tilt the motor up. Actually, I have even removed the motor off the outboard motor bracket without taking the solar panel off it's mounts. Though, probably not the smartest thing to do.

The flexible solar panels have shorter warranties and the size/footprint is much larger because they are not as efficient as a rigid solar panel. I believe they are also more expensive comparing equal watt/amperage units flex to rigid. But the flexible panels can be ut pretty much anywhere and then taken up when not in use - so they are versatile.

My 20 watt panel puts out a max of 1.2 amps/hour. But there are factors that when figured in reduce the amps to a range of .4-.8 amps/hr. If the panel is not exactly at a right angle to the sun, that reduces efficiency. If the panel is blocked from the sun from say a pole that casts a shadow or the mast, then during that time, the panel may produce lower amps or none at all based on how the cells were configured on the panel. You would have to go into the nitty, gritty on each panel to check out cell arrangement, etc to comapre pro/con of each.

I have a Morningstay Pro15M controller. It has a digital readout of the battery volts and the panel amps. It can be set for different types of batteries...so that must change the way it charges but I do not know those details. It has a blocking diode so the batteries do not lose any amperage back out the panel at night and when the motor charges the batteries, once the voltage goes over a certain number, then the controller shuts down the circuit and the panel is not effected.

Edited by - on

stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 02/17/2008 : 11:25:25

I have a 5 year old flexible solar panel that is used to maintain my two 12 volt house batteries.
It has gotten progressively weaker every year. I threw it out last fall.
I've spoken to several retailers and they consistently say that the flexible ones are not reliable.
We're trying to figure out what we need for our boat, in terms of solar power. We use a lot of rechargable battery run devices (A AA and AAA) and have found that we no longer need two house batteries, that one more than suffices. All our lighting, navigation and entertainment is run from rechargable batteries. The only thing that runs from the battery is running lights and a couple of interior lights that we rarely use. Once in a blue moon we run a string of rope lights up the jib and run that from our house battery - as you can see from my profile pic.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 02/18/2008 : 00:58:50

The West Marine Advisors, both in the catalogs and online, offer extremely good information about these products and their applications. Among many other websites is this one: http://www.freesunpower.com/designtools.php

You are ahead of the curve in knowing your energy budget. Research the products and make your choice.

Edited by - on

Turk
Admiral

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USA
736 Posts

Response Posted - 02/18/2008 : 07:11:28

Glivs

I have a rigid 65 Watt panel (BP). I am on a mooring and do not sail everyday, but do get out 2-3 times a week. I've done something a little different. I just lay the panel on the cockpit floor. I connect it using a thru-hull 12v connector (near the outboard) into a mornistar regulator and then to 2 group 27 batteries. During a season my batteries are always fully charged and never have to be charged using an AC charger or the outboard.

Of course the panel cannot be used while sailing, but by then, the batteries are usually fully charged. Keeping it on the floor also keeps it out of site of the casual passerby. The panel is not small (I think it is 24 x 48) but is stowed under the cockpit while sailing. I think 20 watts would maintain a battery, but would not give you enough output especially up north, to get a full charge if using your lights and electronics often. I converted to all LED's inside the cabin and LED on the masthead. Believe me this helps a lot with power consumption lowered to 1/6th to 1/10 the amps. Of course I'm not powering a flat screen TV either!

The output of my panel on a good day is about 3.14 amp/hr. Amazingly the lowest reading on a cloudy day is about 1.5. Mine has the "blue" crystal look to it. Hope this helps as a reference.

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Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 02/18/2008 : 10:09:47

I also have the Morningstar controller with digital read out. It does three stage charging, and also does pulse width modulation, which essentially hammers in more charge to your bank.
I would recommend that you get a new LED anchor light, one that is USCG approved for obvious liability reasons. I suspect that an incandesent light is your biggest battery drain.
I have had my Uni-Solar flexible panel for about 5 years and h ave not had a drop in amperage output. there are websites which will give you your effective solar gain for various lattitudes. I live in Knoxville, and on a good sunny day with my 11 watt Unisolar panel pointed directly at the sun I will get .6 amps out of it, rarely .7 amps.
Make sure you get a panel with several blocking diodes built in. If only a portion of the panel has shade, like from a mast or boom, it will drain off power.
Good luck

Edited by - on

Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 02/18/2008 : 11:28:27

I suggest you replace the anchor light with an LED one. We did and it cut the amp usage by a factor of 10. The LED light is very bright. Our anchor light was the biggest draw on the batteries since it was on at least 10 hours per day while cruising.

Edited by - on

glivs
Admiral

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USA
836 Posts

Response Posted - 02/18/2008 : 17:20:12

Thanks all -- great feedback. An LED anchor light (probably OGM) is definitely in the plans. A single Group 27 battery will meet most of our needs, but want the ability to spend a long weekend or a few days on the boat. Need to do some more reading. Looks like I should take advantage of dropping the mast for this project to check/fix/replace whatever else is on the masthead. One problem of living in the north country is that sailing and boat project have to compete with admirality projects(home projects)over a short season. Still plenty of snow and ice, but spring is in the air...

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Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 02/18/2008 : 20:38:17

One advantage of a flexible Uni Solar panel is that you can place it on your cabin top while sailing, or next to your cabin by the window if you are on a long broad reach. You can step on them with out hurting them, not that you wouldn't try to avoid that. I don't know if you could do that with a fixed paned with a glass top.

You could at least get some more amp hours in while cruising.

Do you have an electric start motor which will charge for you?

Edited by - on

lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 03/16/2008 : 20:06:21

I have a 50 watt rigid Kyocera panel mounted from the stern pulpit over the outboard. It seems to provide enough power in the summer months to keep the two house batteries topped off. However, I have not spent more than three days on the boat since it was installed, so I don't know for sure if 50 watts is enough for an extended cruise. The acid test will be this summer when I will be up in the San Juans for three weeks. I try to minimize my electrical loads, but some are on almost all the time: the GPS/Depth sounder, the VHF radio, and in the evenings a 25 watt florescent cabin light. If I am watching a movie or downloading photos to my laptop computer, it's drawing 75~150 watts. Each 12v incandescent bulb like the anchor light is 10 watts. I use a CPAP respirator at night, and that's 20 watts. My Yamaha T8 outboard puts out about 40 watts at 2500 rpm, and I'll be counting on that power to help keep the batteries charged.

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Gloss
Master Marine Consultant

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USA
1916 Posts

Response Posted - 03/16/2008 : 20:45:20

Hey Larry,
sounds like a good trip you have planned.
You may want to look into replacing your anchor light with an LED anchor light. Much less amp hour draw than a regular incandescent.
Do you have to use an inverter with your CPAP machine? If so, do you have to have a pure sine wave (expensive) or will a modified sine wave (cheaper) work without blowing out the electronics or compressor. I would hate to see you be out there without your machine.
When I used to go to the keys for a couple of weeks of sailing I would run the motor at night when I was cooking dinner with the stereo on to drown out the noise (not much with the Honda) and then while cooking breakfast and coffee have the motor on then too.
Your flourescent light should help cut down on power usage too.
How many amp hours in your house bank? Can you pull start your motor if needed?

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 03/17/2008 : 04:55:53

25w Fluorescent... would flicker for me as I would be turning it off frequently to save watts left in the battery.

Totally agree with Frank about the anchor light, but would take it much further and we are replacing every lamp in the boat with LEDs.
Typically an LED will consume about 1/10th of any 12v incandescent lamp equivalent (very ball park figure).

We have a loud Genny on board that will charge the batteries, but that forbids using the 12v system while charging. However it's pretty much a necessity for us as we have 110v air conditioning onboard. So we'll be changing out our existing battery charger for one that permits using the 12v system while charging.

Solar power is the way to go, we have read that chapter in Ben Casey's Boat Electrics Simplified a dozen times, probably the clearest description of solar on a boat available.

Flexible panels (amorphous) are typically 50% efficiency of Polycrystalline types and tend to be more expensive. However the cost of a supporting frame for solid panels balances out the initial cost to some extent. For us the important issue is power! So we're going with rigid panels mounted on gimbals at the end of a pole.
Our first step is to mitigate power consumption, hence swapping out all lamps to LED. We already have a 2nd Battery, but we're reviewing the electrical layout to ensure we are not loosing any power between batteries. Finally the solar panels. Ours will mount above the back of the Bimini, as mentioned, on gimbals. It's not our idea that we'll be constantly adjusting the panels, but when if on a long tack then it might be worth it early or late in the day. At least we'll have the option.

Edited by - on

OLarryR
Master Marine Consultant

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USA
3441 Posts

Response Posted - 03/17/2008 : 05:43:13

Agree that the rigid solar panel does require a mount and that then adds to the cost when compared to a flexible panel. There are pro/con going the flex vs rigid solar panel. It really is an individual thing.

In regards to my rigid Kyocera solar panel, it is out of the way above the outboard and so I never mess with it except to change it's angle. I keep it horizontal in the summer months and angled in the winter. The mounts did cost but less than if i bought them commercially and at least my opinion is that my mounting is superior than anything else I saw by a mfr. I can adjust my mountoff the stern for angles to the sun and also can still lean back on the outboard when it is up and sailing downwind - so the panel does not get in the way for those that like to relax that way sailing downwind. Details of the build and photos are on my website. Here are some photos:

Edited by - on

stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 03/17/2008 : 17:24:07

we all know the popularity of OBs to thieves.
Do many of these mounted solar panels go missing?

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OLarryR
Master Marine Consultant

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USA
3441 Posts

Response Posted - 03/17/2008 : 18:57:19

I think most that travel down the dock past my boat are oblivious to the panel. Though, it would not seem possible except that my marina has 90+ percent motorboats in it and believe most owners and visitors are interested in power craft....not a wimpy 20 watt solar panel on a sailboat.

Now if there were any nerds coming down the dock, then maybe I would start to worry.

Edited by - OLarryR on 03/17/2008 18:59:30

Voyager
Master Marine Consultant

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USA
5353 Posts

Response Posted - 03/17/2008 : 23:06:12

Not to change the subject, but to what extent do flexible cables and padlocks protect one's OB or Solar panels? There's the kryptonite stuff, but don't you just need a good set of bolt cutters to dispense with a padlock?

Edited by - Voyager on 03/17/2008 23:07:01

OLarryR
Master Marine Consultant

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USA
3441 Posts

Response Posted - 03/18/2008 : 05:50:41

In regards to cables in general, believe most of them are easily cut. I think the main benefit of a cable w/padlock is to act as a deterrent so whoever is looking to do some stealing moves onto another boat that has no protection. They have those channels that fit over the outboard handles and that is then padlocked but believe a past discussion on this subject indicated that also can be circumvented - Still it is an easy deterrent with minimal hardware visible detracting from your boats appearance/clutter. Another method that is used is to bolt the outboard bracket support block to the motor by drilling a hole thru the outboard motor support block. But if they have the proper tools, they could unbolt it. Again..it's a deterrent.

In my marina, we have security gates to each of the main docks. So limiting the docks to mostly boat owners helps. While we have little , if any theft, if it does happen it is mostly from the waterside entry. Other motorboats can come into the marina and board the boat. having a slip further into the marina is then a sort of deterrent and while docking the boat stern into the main dock may make it easier to unload a motor to the dock, it makes it harder to take the motor off if accessing the boat from the waterway.

In regards to the solar panel....well the flexible ones will be the easiest to just pick up and skedaddle. The rigid panels have various mounting arrangements and it would take some time to undo all that. Then any solar panel over the 5-10 watt size is going to have to have a solar controller and they are not goig to get that unless they get into the boat and really go to town on helping themselves to your goodies. The panel is rather hard to secure with a lock. Many panels are constructed with just a no frills aluminum channel around it's border and the channel is oftentimes used to secure the panel to the mounting hardware with small diamter bolts & nuts that should not be all that hard to loosen or break off with a padlock cutter even if the bolts and nuts are made of stainless steel. On my panel, I have made it even easier to unbolt from the panel channels by the use of wing nuts !

Edited by - OLarryR on 03/18/2008 05:51:09

stampeder
Master Marine Consultant

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1608 Posts

Response Posted - 03/18/2008 : 10:43:43

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">On my panel, I have made it even easier to unbolt from the panel channels by the use of wing nuts !<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">
That's exactly what prompted my question. There were two dingys and at least two OB's stolen from our fenced/gated marina last summer. Just as I'm in the process of pricing out equipment in the $1.5-2K price range, I'm wondering if the thieving community has set their sights on this kind of equipment yet. Seems to me that there would be many more places to fence a solar panel than an OB.

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