Solar system on Catamaran

Seaking · May 2011

Hello,

I am new to this board and solar. I am putting together a system with Aurinco http://www.aurinco.com/solar-electric_us.html thin panels for marine use. They are 18 volt and at this time I am planning to get 8 @50watt panels and 2 @100watt panels for a total of 600 watts. I will have an 800amphr battery bank. The boat will have a 3000 watt inverter. It will also have a 6kw diesel generator and two diesel engines with 90 amp alternators. But I want to have quiet power also.

the wiring to the controllers will be from 15 to 25 feet. I was thinking of getting two 25 A controllers to split the system having each controller with 300 watts at 18 volts feeding it. Then if one controller goes bad I would still have half the output. Then I look at MPPT controllers and there are none that small except for the Blue Sky and it does not have great reviews.

Should I stick with a 18 volt wiring job with two flexcharge 25a controllers or go to 36 volt and get a single 60amp outback and 12 @ 50watt panels wiring them in pairs then parrallel

Hope I have made some sense, all help/ideas will be appreciated.

BB. · May 2011

Re: Solar system on Catamaran

There are several good MPPT controllers in smaller sizes:

Both are very good controllers. The Rogue is being released as Version #2 around June 1st (last I heard)... Very good price/performance MPPT charge controller.

Is this a sailboat or a cabin cruiser?

In the end, solar PV panels do not work well under shade or shadows from lines/gear/etc... They really only work well in full sun and facing relatively towards the sun (cosine of the angle--0 degrees = 1.00; 10 degrees = 0.98; 60 degrees = 0.50, etc.).

Ideally, for MPPT controllers, you would want series/parallel connected panels to be in the "same plane/mounting conditions" if you share one controller. If they are East/West mounted panels (for example), you would be better off with two MPPT controllers.

Also--Are you planning on getting a lot of power from the solar panels--or just enough to keep a few low power loads operating (radios, some LED lights, small TV/Laptop, etc.)--or are you planning on running the genset to recharge the batteries in the AM after a night of "quiet"?

Basically, the 3,000 watt inverter is a pretty large guy... and if you ran it at 50% load--your solar panels (if optimally mounted) would only run that load for around 30 minutes a day (plus or minus--depending on sun, orientation, shading, etc.). Plus you may be looking at 30+ watts just to run the inverter before you place your first load on it....

Normally, about now I recommend looking at conservation and possibly a second/alternative "lower power" inverter that would be a better balance for sustained loads--For smaller 12 volt system, the MorningStar 300 watt TSW inverter is a great unit. The TSW is good for small wall wart transformers, power supply bricks (laptop computers), and recharging cell phone batteries, etc....

What are your expectations from the solar array/battery bank (Amp*Hours/Watt*Hours per day, peak load, average load, etc.).

-Bill

Cariboocoot · May 2011

Re: Solar system on Catamaran

Bill; "Solar system on Catamaran".

I see the old familiar situation: 800 Amp hours of battery, 600 Watts of solar. Fortunately having a couple of 90 Amp alternators means the batteries will get charged; just don't expect the solar to do it all.

There's no need to split up the panels unless there are significant locational differences which would cause uneven output (some for, others aft or port/starboard division).

I'm going to guess 12 Volt system, since the OP is going with 18 Volt nominal panels. If that 18 isn't Vmp they will be hard-pressed to charge without being wired up in series and run through an MPPT controller. Even so, for full charge from solar you should have:

14.2 Volts charging * 40 Amps minimum = 568 Watts less typical derating = 737 Watt array. 600 Watts is likely to be a good strong maintenance charge, but not a full-blown recovery charge.

Personally I'm not keen on an 800 Amp hour 12 Volt set-up. Nor a 12 Volt 3kW inverter. Any chance of going up to 24 Volt? If you really need that much power. That would be about 4.8 kW hours potential, or twice what I run the whole cabin off from including refrigerator and water pumps.

BB. · May 2011

Re: Solar system on Catamaran

Cariboocoot wrote: »

Bill; "Solar system on Catamaran".

Still don't know if sail or cabin cruiser...

Twin diesel with 6kW genset--not a Hobie Cat.;)

-Bill

Cariboocoot · May 2011

Re: Solar system on Catamaran

BB. wrote: »

Still don't know if sail or cabin cruiser...

Twin diesel with 6kW genset--not a Hobie Cat.;)

-Bill

Oui! Or else it's been heavily modified.

Seaking · May 2011

Re: Solar system on Catamaran

It is a sailing catamaran. I expect to be able to keep the refrigeration running 24/7. Two 12 volt systems. have some extra power for sailing with auto pilot and some other instruments without the need to run an engine or the generator. For heavy charging the generator or running the engines.

I an looking to help prolong the life of the batteries by some charge going into them daily, hopefully to never allow the batteries to go dead or much below half charge.

My thinking of splitting the panels into two groups is due to potential shading of half the panels by the sail. Also to have redundancy of at least half of the panels working in case a controller does fail.

One of my questions is, if it would be better to set it up in a 36 volt system and use MPPT controllers.

this is the specs for the 50 watt panels
Electrical properties: Pmax 50 W; Vpm 18 V; Ipm 2.8 A; Voc 22 V; Isc 3.1 A

Thanks again

icarus · May 2011

Re: Solar system on Catamaran

Same rule(s) apply, be it a boat, cabin, house or RV.

All calcs start with the loading. Figure out your loads, figure out how much/often the engine or genset are going to run to contribute to the charge, then figure you PV and battery bank to fit.

My rule of thumb, off gird (and it is way worse for boat and RVs) Take the nameplate rating of the PV, divide by two to account for all cumulative system loses, then multiply that number by four to represent the average hours of good sun one can reasonably expect, per day on average over the course of the day.

600/2=300*4=1200 wh/day.

Because you are on a boat, the number will be worse as the panels are never (or seldom) ideally oriented, so I would add an additional derate.

A couple of other "rules" is that people tend to under estimate their loads, while at the same time underestimate the amount of solar harvest, leading to significantly poorer performance.

The other rule, is that loads alway grow with time.

Good luck, welcome to the forum, and keep in touch,

Tony

BB. · May 2011

Re: Solar system on Catamaran

1,200 WH / 12 volts = ~ 100 AH per day at 12 volts.

That is not a lot of power (barely enough to run many fridges?)--And may not be possible on your boat by the time you take variable orientation, lines/sails/etc. into account.

As an example, here is a sail boat thread about solar (racing--still ran out of power just running lights, radio and pilot):

low-amp system for small sailboat

-Bill

Cariboocoot · May 2011

Re: Solar system on Catamaran

To the good; there is no inverter to power, yes?

If there are two separate 12 Volt systems (positive sides isolated but common negative) then you need to have two charge controllers because the batteries will never be in an identical state. It might be a good idea to add battery monitors, and be able to switch over all charging power to whichever bank needs it most.

With a 600 Watt array there is usually some advantage to MPPT. With two 300 Watt arrays, the advantage goes down. Also, sail boats are notorious for casting shadows over panels. In that respect having parallel connections is better. Since you have an even number of panels, perhaps you can wire it up for 36 Vmp and run two small MPPT controllers. Although it looks like the output would potentially exceed the Morningstar 15 Amp. That means either the 45 Amp Tristar, one of the higher Voltge Blue Sky units, or the anticipated new Rogue as there is not much sense in going for the really expensive CC's from OB, Xantrex, or Midnight.

BB. · May 2011

Re: Solar system on Catamaran

Seaking wrote: »

They are 18 volt and at this time I am planning to get 8 @50watt panels and 2 @100watt panels for a total of 600 watts. I will have an 800amphr battery bank. The boat will have a 3000 watt inverter. It will also have a 6kw diesel generator and two diesel engines with 90 amp alternators. But I want to have quiet power also.

If the boat were in a dock and had a fixed orientation--you might get pretty good sun... However, at anchor/cruising, etc... I would wonder if you would get 1/2 the above output due to shadows and orientation.

Solar power is not very dense power on fixed land installations--on the water--it gets pretty dicey to expect significant amounts of power (more than trickle charging the battery bank/keeping a sump pump going when unattended).

Perhaps some other readers / boat owners can have some more accurate information and can help here.

-Bill

Seaking · May 2011

Re: Solar system on Catamaran

Thanks for the comments BB and Cariboo. My hope is to be able to run the fridge 24/7, if I am sailing the instruments should have enough power to run also. The engines charge the batteries pretty quickly with a short about of run time. The genset will bring them up the quickest. I am mostly concerned leaving the boat unattended and feeling like the batteries will be ready to go when I return. That includes at the dock, I hate hooking up shore power.

I am now planning to go with a 36 volt wiring job, that seems like it should help the output and installation using smaller wire(conduit limitations). I just have to decide on controller or controllers. I like the idea of two controllers so if one goes out I still have half of the system going. The way the panels are laid out the sun may only shade 200 watts if the sun was off to one side of the sail. I will try and attach a pdf of the layout when on another P.C., it is not on this HD

I'll be researching controllers now, all advice appreciated.

Thanks again

dwh · May 2011

Re: Solar system on Catamaran

icarus wrote: »

Same rule(s) apply, be it a boat, cabin, house or RV.

All calcs start with the loading. Figure out your loads, figure out how much/often the engine or genset are going to run to contribute to the charge, then figure you PV and battery bank to fit.

I don't think I exactly agree with that.

I think that for mobile rigs - boats and/or RVs for instance - the calcs often work the other way; You figure out how much PV you can fit, which determines your power budget and then you have to fit the loads to the budget. Then you can calc a battery bank size according to the budget and the loads.

icarus · May 2011

Re: Solar system on Catamaran

My reasoning for further derate compared to my normal 50% for Mobil installs is that the panels are seldom if ever ideally oriented. Add in a consistent few degree off aim, both is azimuth and elevation and you begin to add in smaller harvest pretty quick. Add in shading from lines, or masts or, in the case of RVs smaller air space under the panels and you add in a bit more.

Just my observation and opinion, worth every penny you pay for it.

Tony

Seaking · May 2011

Re: Solar system on Catamaran

Now with the shading factor, the supplier points out that wiring them all parallel would be better so that if one panel was shaded it would not affect the entire group but only its output. Below are the panels output.

Pmax 50 W; Vpm 18 V; Ipm 2.8 A; Voc 22 V; Isc 3.1 A.

I don't have an exact length of wiring yet, as the conduit placement in the hardtop is not decided. But now the wire size seems to be an issue, as the conduits are small in diameter. I need to verify that with the builder also. Everything is happening in Capetown, SA. and I am near Annapolis, MD. If I am hooking all in parallel can the trunk line/bus line to the controller get larger as the amp load increases or does that wire have to be the same gauge from the panel most far away from the controller.

The boat will be used in the Caribbean so it is in a sunny area and I am expecting decent output from the 600 watts of panels. The fridge is a 12 volt system and is to be my major concern.

Thanks All
Seaking

If anyone is near Annapolis,MD and would like to go sailing drop me a PM

mike95490 · May 2011

Re: Solar system on Catamaran

There are some high voltage ( in the 90V range) grid tie panels, that can solve the 10 pairs of #8 cable situation, but you would need a MPPT Controller, which can sometimes be easily confused when part of an array is "different". Maybe someone has a MPPT that can be locked to a preset voltage ?

Cariboocoot · May 2011

Re: Solar system on Catamaran

Panels wired in parallel can be joined near the panels and then larger wire (to handle the increased current) run to the controller. More than two panels in parallel and each will need to be fused.

Seaking · May 2011

Re: Solar system on Catamaran

Cariboocoot wrote: »

Panels wired in parallel can be joined near the panels and then larger wire (to handle the increased current) run to the controller. More than two panels in parallel and each will need to be fused.

Where and what size fuse. Here is the panel info
Pmax 50 W; Vpm 18 V; Ipm 2.8 A; Voc 22 V; Isc 3.1 A

So maybe a 5 amp fuse on the positive wire of each panel?

Cariboocoot · May 2011

Re: Solar system on Catamaran

Seaking wrote: »

Where and what size fuse. Here is the panel info
Pmax 50 W; Vpm 18 V; Ipm 2.8 A; Voc 22 V; Isc 3.1 A

So maybe a 5 amp fuse on the positive wire of each panel?

That sounds right to me. I could be wrong, though.

Solar system on Catamaran

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