sailboat solar installation questions: mixed panel types, mppt, etc

[susswein]

The current solar system on my sailboat (75 watt monochrystalline panel and older morningstar PWM controller) isn't keeping up with demand, so I'd like to add additional capacity.  I don't have the space to mount another rigid panel, but I've got four uni-solar amorphous (flexible) 22W panels that I could attach in various places on the cabin top.  Battery bank is 240AH of wet cells, and demand is about 50 AH/day.

1) any problem mixing (in parallel) the 88 watts of amorphous panels with the 75 watt mono panel?  Should I hook all the panels into a single charge controller, or would I be better off having a separate controller for each panel type?  If I go with 2 separate controllers, do I just hook them up to the batteries in parallel, or will they interfere with each other?  BTW- these are all 12V (nominal) panels)

2) On this size installation, is it worth upgrading to an MPPT charge controller?  The boat is only 27', so I estimate my wiring runs will be 15' or less.  I'm limited in the square footage available to mount panels, so an extra 10-20% more amps from mppt sounds attractive.

[Rover]

I probably would not go through the expense of using an mppt controller with what you have, I'd probably just mix and parallel the panels through a pwm style controller. Solar panels on a sailboat are troublesome, there are lots of items that can cast shadows( mast, boom, etc) doesn't take much of a shadow to drasticaly cut the panels output. I used to own a 26' Pearson sailboat, I  only mounted a small panel on the cabin forward of the mast.

Do you have a bimini ? or other structure over the cockpit?

The 50AH day requirement is that for : live aboard, at a mooring , cruising?  What time of day do you use the power (daytime/nightime)?

I see you've also posted about fixing the amoprphous panels to the van .. interesting.

What kind of sailboat is she?

[susswein]

The boat is a balboa 27 located in the sea of cortez.  I live aboard and cruise her for about 3 months of the year, mostly boodocking (the ultimate in off grid living!).  The 75 watt panel is mounted on the rear rail where it's mostly not shaded, but the 22 watt panels would be in different places on the deck and cabin top.  The shading issue is one reason I'm considering an mppt controller.  If I hook up these panels in pairs in series (giving me 24V nominal), then the mppt controller should maximize the power output even if partial shading reduces the voltage, right?

The 50 AH estimate is while I'm cruising and at anchor.  Most of it is used by an 80 quart 12V fridge that draws 4.5 amps but only runs for around 8 hours/day.  the rest is a mix of led lighting, laptop, gps, vhf radio, etc.

[ghurd]

Partial shading issues will drop the output amps like a rock, for any kind of panel.
Even a line shadow or rail shadow has a very substantial impact.

I expect the output would be better if the panels were paralleled, instead of seriesed to MPPT.

Like Rover, I think the cost of MPPT would be better spent on another couple of small panels.
G-

[DanG]

Have you tested the 22W panels in realworld situations? Yes, amorphous panels better accommodate small shaded spots; bird droppings and leaf shadows etc. but the shadow of a lines' crossing an entire panel face may seriously drop the output.

cruise her for about 3 months of the year, mostly boodocking

If you often anchor w/o radically shifting position to catch the daily 3-5 hours peak solar output then yes the MPPT controller may better help keep up with aging batteries or increasing loads. If you need cruise power then the parallel only might be your best bet. If you have the money setting up up switchable both ways may make you really happy with that arrangement.

My opinion on solar is is kind of down to decide what piece anchors your PV solar system install, which piece to keep for the longest - If you are set on purchasing a MPPT remember to try and buy only once - sell off the other pieces of the system and gradually improve it overall but keep the (over-sized?) MPPT as base for everything else in the future. Panel efficiency has improved in the last few years, in the space taken by your 75 watt mono-crystalline panel you might be able to get 80, 100 or 120 watts depending on who made them when and with what process.

[Rover]

Partial shading issues will drop the output amps like a rock, for any kind of panel.
Even a line shadow or rail shadow has a very substantial impact.

This is typically why you see more wind turbines on sailboats then solar panels. Also on a 27' sailboat, at some point you need all the deck space, at one time or another, for working with  running rigging, sails , etc , so you really want to avoid deck/cabin top mounting anything permanent.

Wind turbines are the preactical way to go, even though most are noisy buggers, seem to get noisier in my marina then anywhere else . If you decide to go with a marine wind turbine, please reaseach it well, the most common one, err.. not my favorite