My Solar Project

[Hkalan]

Greetings,

Spent the last 4 days faithfully reading all the forums, but still can't wrap my head around the "Solar Power" system for a new vessel I am planning for my retirement in 2012 to be a 100% live aboard.

The vessel is a Dyna (Taiwan built) 63 foot motor yacht. Will have two CAT C12 engine and a 12KVA (230V/50Hz) Genset. I want a hard top over the flybridge to place solar panels. The area of the hard top is 5.9 meter by 2.5 meter (in front of a tapered mast at stern) See the attached draft.

While at the mooring. The vessel will be facing 182 degrees south.

From my calculations, I can place six 250w, 48.6 Vm(Volt), 5.48 Isc(Amp) on the top, I am also talking with the shipyard about the area in front of the flybridge (roof above the lower helm) to add more panels. Do not know that actual size right now, so I use the 6 panels as the foundation. I have an 8 string combiner (string box) that I can connect the 6 panels in parallel if I want, so that is an open option.

An 80amp MPPT controller should work for the 6 panels... from my calculations.

So... The vessel comes with the following battery banks as standard...
- 24 volt 200ah house bank (2 12v in series),
- two 24 volt batteries for the C12 CAT's (1 each for starting),
- one 12 volt battery for the Genset (starting),
- one 12 volt for navigation equipment and radio,
- 24 volt 200ah (2 12v in series) for the bow thruster.

As standard, it has an 80amp AC to DC charger for the 24 volt systems, and a 25amp AC to DC charger for the 12 volt systems.

I have now calculated the AC gear (fridge, ice maker, TV's, computers, microwave, WITHOUT any Air-conditioning or the 100% DC lighting). That seems to add up to 13.05Kwh a day (.54Kw each hour on average), that I would like to have connected to a Sub-panel that is powered from an inverter off of a "Beefed Up" house bank or seporate bank from the solar controller.

I can't wrap my head around the Amps... I read about AC amps and then DC amps, and have to multiply by 10... etc...

I believe I am more confused right now then when I started.

So my questions still remains un-answered in my head... At sea, or at the mooring.
1 - Is 1.5Kw of solar enough ?
2 - Would a 3,000 watt Xantrex Freedom 3000 with a Outback 80 be enough ?
3 - Should I up the House Bank to 600ah or even 1,000ah ?

Hope you can put me on the right path to know the right way of setting this up right the first time !

Thank You,

Alan

[Alecadi]

Originally Posted by Hkalan

Greetings,


While at the mooring. The vessel will be facing 182 degrees south.


Alan

It depends on the wind direction.. I'll be very surprised that your boat will stay on a constant heading of exactly 182 deg... what about wind shifting, tides current etc...

[Hkalan]

Hello,

Direction is just as a rule of thumb for the post... The birth I have now, places my current vessel in that general direction (and thus will do the same for the new vessel), so I should get a nice path of sunshine during the day... nobody knows what will happen while I am out or anchored, but the mooring is just there as some info.

Thank You,

Alan

[deckofficer]

Nominal panel voltage for charging batteries should be around 135% of battery bank's nominal voltage if you don't want a prolonged taper as the bank starts reaching 70% SOC. You of course need a controller to keep from over charging and gassing the batteries. A 12 volt battery at full charge is about 12.9 volts, so a panel of about 17.5 volts nominal with controller would be the way to go. A lot of panels with more cells in series (0.55 volts per cell) for a nominal voltage of 48.6 volts are used in a grid-intertie system where you will be running enough in series to be producing 350+ volts. If yours is a 24 volt system, then you would be running 17.5 volt panels (2) in series, and for more amperage run those 2 in parallel with as many groups of 2 that you want.

For your math, just remember that tasty PIE. P (power in watts) = I (current in amps) X E (electromotive force in volts). So a 250 watt panel that you would use at the voltage of 17.5 would deliver 14.25 amps. Two in series would be 500 watts, 35 volts (for charging you 24 volt bank) at 14.25 amps.

[Hkalan]

Hello,

This is one of the things that confuses me.

I am going off the specs of the Outback FLEXmax 80.

1 - It can be set for a 12/24/48volt battery Bank
It should auto-detect the 24volt bank
2 - Adjusts for the 48.6volt panel and the 24volt bank

Using small watt panels (17.6v) will waste the available space I have on top of the flybridge.

I was on the understanding that the MPPT in the FLEXmax 80 would take full advantage of this voltage.

So a 36.8 volt panel at 185W would be a better matched panel for a 24 volt bank ? But then a major loss in Watts.

Alan

[cal40john]

MPPT controller won't waste the higher voltage. Its job is to maximize power transfer by making best use of the panel, whatever its nominal voltage is. (Within limits.)


John

[deckofficer]

Within limits might just be the operational term here. I'm not too up to date on all the specs of the current crop of charge controllers, but solar panel outputs are rather cut and dried. Here are the specs for a common 12 volt, 120 watt panel that sells now for just $210.00.

Model Name: PV-SC120J12
Number of Cells: 36 cells in series (4 x 9)
Max Power: 120Wp
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 7.4A
Maximum Power Voltage (Vmp): 17.6V
Maximum Power Current (Imp): 6.82A
Dimensions (inches): 57.33 x 26.13 x 1.365
Weight: 20 pounds

As you can see, 17.6 X 6.82 = 120.032 watts, a 120 watt panel. No matter what a charge controller can do, max short circuit current is 7.4 amps, so I can't understand how a controller can still give rated wattage of a panel array that is something higher than 135% of battery bank voltage. If it does with some PWM magic, I'm all ears for an explanation on how its done.

[cal40john]

There's a whole slew of threads on whether it's better to wire panels in series or parallel to use with an MPPT. They focus mostly on topics of power loss in wires and shading of panels, not on whether the MPPT's efficiency changes with input voltage.

Threads on CF
series parallel mppt - Google Search

The limit I was talking about had to do with max voltage the MPPT accepts to not burn up.

How MPPT works:
https://www.google.com/#hl=en&sugexp...a4de9b5c8930c4

John

Originally Posted by deckofficer

Within limits might just be the operational term here. I'm not too up to date on all the specs of the current crop of charge controllers, but solar panel outputs are rather cut and dried. Here are the specs for a common 12 volt, 120 watt panel that sells now for just $210.00.

Model Name: PV-SC120J12
Number of Cells: 36 cells in series (4 x 9)
Max Power: 120Wp
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 7.4A
Maximum Power Voltage (Vmp): 17.6V
Maximum Power Current (Imp): 6.82A
Dimensions (inches): 57.33 x 26.13 x 1.365
Weight: 20 pounds

As you can see, 17.6 X 6.82 = 120.032 watts, a 120 watt panel. No matter what a charge controller can do, max short circuit current is 7.4 amps, so I can't understand how a controller can still give rated wattage of a panel array that is something higher than 135% of battery bank voltage. If it does with some PWM magic, I'm all ears for an explanation on how its done.

[Alecadi]

Originally Posted by Hkalan

Hello,

Direction is just as a rule of thumb for the post... The birth I have now, places my current vessel in that general direction (and thus will do the same for the new vessel), so I should get a nice path of sunshine during the day... nobody knows what will happen while I am out or anchored, but the mooring is just there as some info.

Thank You,

Alan

I understood mooring, not docking...

[goboatingnow]

Originally Posted by deckofficer

Within limits might just be the operational term here. I'm not too up to date on all the specs of the current crop of charge controllers, but solar panel outputs are rather cut and dried. Here are the specs for a common 12 volt, 120 watt panel that sells now for just $210.00.

Model Name: PV-SC120J12
Number of Cells: 36 cells in series (4 x 9)
Max Power: 120Wp
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 7.4A
Maximum Power Voltage (Vmp): 17.6V
Maximum Power Current (Imp): 6.82A
Dimensions (inches): 57.33 x 26.13 x 1.365
Weight: 20 pounds

As you can see, 17.6 X 6.82 = 120.032 watts, a 120 watt panel. No matter what a charge controller can do, max short circuit current is 7.4 amps, so I can't understand how a controller can still give rated wattage of a panel array that is something higher than 135% of battery bank voltage. If it does with some PWM magic, I'm all ears for an explanation on how its done.

Not sure what's the fixation on 135%.

Unless you have a boost convertor, the input voltage to the solar regulator must be above the necessary max needed battery charge voltage. ( plus a bit for the electronics). But with most solar panels thats easy to do.

What a MPPT Controller does is actually give you what that panel spec says the panel should do , ie the max power point voltage times the mac power point current.

What people doesn't realise is the voltage. Current relationship of a photovoltaic panel is not linear. The specified PIE is only valid at the max point.

Hence a 100w panel is not 100w at other voltages. MPPT solves this by keeping the panel at the max power point. It doesn't generate anymore power then the panel is rated for.

Dave

[noelex 77]

A couple of general points.

1. Generator run power boats are often set up with power inefficient appliances, because the generator can supply all the power necessary). Often when converting to solar power it is cheaper and easier to replace these appliances with more efficient products rather than trying to increase the solar array size to produce enough power for their inefficiencies.

2. 1.5Kw of solar will only generate 9Kwhrs under very good conditions of high insolation at the right time of the year. This is still well short of the 13Kwhrs you need, but you need to size the array for less favorable conditions or be prepared to use the generator frequently. You will not have enough room for this.


3. There are inefficiencies in the system. If you work in KWHrs these inefficiencies are very noticeable (which is part of the reason boats talk about AHrs ).
To use 13Kwhrs you will have to generate something like 16-17 KWhrs.

4. For MPPT to work well the solar cells need to be similar. Make sure the area in front of the flybridge can accommodate panels with at least the same Voc etc.

5. Your hose bank is too small. Your thinking of something like 600 -1000Ahrs will be a necessary upgrade.

[goboatingnow]

OP, 1.5 kw of solar running a .5 kwh system in theory is enough. ( to a point ) There are several caveats.

(1) actual panel output can be severely degraded by shading and sunlight levels and incorrect angles of incidence. Actual output could be a lot less then max output.

(2). Using average Kwh figures can be a trap. You also need to look at max consumption and see how long the batteries can support that load and most importantly how long it will take the panels to recover that power loss. You may need a much bigger bank to sustain the peak load requirements. But remember batteries Don't generate power. Unless you can recharge at sufficient high rates, large battery banks do nothing for you.

(3) theres a significant loss of efficiency in conveying solar to battery charging and a loss of efficiency in charge acceptance in batteries. Batteries can loose 50% of their charging current in absorption phases. What that means is that overall efficiencies will be in the 80% range.

I really wouldn't sweat it. Given the onboard diesel generation. It doesn't make sense to seek total solar independence. Hence the solar system will handle most of the domestic load but you may have to use high powered battery charging to replace peak load power.

(4) a definitive answer is complex as it means profiling accurately your power consumption profile over time.
Dave

[Hkalan]

Hello,

Thank you for the wonderful input.

House Bank:
Today I have found 12 - 2 volt 2,000ah Forklift batteries (the weight is too much I think). I have also found 4 - 6 volt 2,000ah Forklift batteries that will solve some issue...

Extra Panels:
After talking to the shipyard. The area in front of the flybridge will only accept 3 more matching 250W panels for an additional 750W (2,250W Total). The panels are only $325 USD. I really like the price for this size panel (directly from the China Factory).

Solar Water Heater:
I have found a factory that can supply a flat solar water heater panel that would heat a 40 Gallon tank below deck (they can put in an additional coil in the tank that could connect to the Genset cooling system, so the water heater would be Electric/Solar/Engine heated to eliminate any worries for hot water.

I know that we will be running the generator regularly on the summer evenings for the Air Conditioning (Hong Kong summers are hot and sticky). I was just hopeful that the daytime hours, and autumn/winter/spring could be quiet without the generator, and take advantage of the sun that is so ample here.

The addition of 2 wind generators is always an option to help. There is always a wind here (3 to 5 meters per second in the evenings as I am told by others that use them in this area), but it is the size and noise of the wind generators I worry about.

This is the first, and last brand new vessel I will ever buy, so I really hope I can make use of the sun and wind cut down on the carbon footprint it already has... My heart is in the right place, but still want the modern comforts too !

Alan

[djmarchand]

Alan:

Your calculation are all theoretical and don't consider how cruisers really use their boat's electrical system.

For example, even high end cruisers (and with your new 63' MY you certainly qualify as high end) rarely use more than 250 amphours at 12 V each day or about 3,000 watts. What you are probably not considering is the percentage of time in an average day that the appliance is actually running, like the refrigeration (25-50%) and the microwave (1%).

A good rule of thumb is that a flat panel solar array will put out on an average sunny day 4 times its rated output. This rule takes into account losses due to the angle of the sun but not cloudy days or local shading. Add more depending on where you are and how much sun you get (not so much for Phoenix, but at least double for Maine).

So for the sake of calculation lets add 25% to make it 5 x the solar array nameplate wattage. So 3,000 watts (my number) div 5 equals 600 watts. You may want to add more, but I can't imagine anyone needing more than 1,000 watts of solar on a boat UNLESS YOU WANT TO RUN AIRCONDITIONING. Then the skies the limit.

So lets use 1000 watts for the next calculations. At this wattage you definitely want to use the high voltage (30-40 V) 200+ watt solar panels. So lets assume you have 5, 200 watt panels. The pertinent spec iis Voc (voltage at open circuit). Your MPPT controller needs to be spec'd to take this max voltage.

Your 1000 watts will put out approximately 1000/24 = 42 amps from the controller at 24 V. Most solar controller standards increase this amperage by 25-50% for various safety factor issues, so a 60 amp controller looks like it will work.

Now for the size of the battery bank and inverter. It all depends on how long you want to be able to run without sun, ie a long stretch of really cloudy days. Let's assume 2 days and at 3,000 watts that is 6,000 watts of battery USABLE capacity. Since you don't want to run batteries down below 50% for decent life, double that number to 12,000 watts. So 12,000 div 24 = 500 amphours of battery capacity at 24V. You don't need another battery bank for the solar controller, just add to the house bank.

A 3,000 watt inverter should cover any reasonable AC load EXCEPT AIR CONDITIONING. I would't buy anything from Xantrex. Victron and MasterVolt are good brands.

David

[Hkalan]

Great information, Thank You David !

I am in Hong Kong and we get a lot of sun - Unless A typhoon comes, but we are connected to shore power and morning ropes are tight at those times.

I have calculated the "AC" power and the amount of hours used daily. See Attached. I was reading - and plan use a timer on the AC fridge to only run for 8 hours a day. They say it works fine for them on their Off-Grid system. We mostly cook on the BBQ grill and LPG cooktop attached to the grill, or the portable Butane Gas Burner in the galley (sits on top of the Electric stovetop).

Panels:
1) I will have 9 panels (See attached Specs) to total 2,250W.
2) I have traded in my 8 string for a 16 string Combiner Box / DC-Disconnect
... Thus I can connect in parellel if I want

House Bank:
The House Bank will be 24V 2,000Ah

Controller:
I have already purchased the FLEXmax 80

Inverter:
I will look more into Victron and MasterVolt.
a) Having the "Auto Gen Start" feature is a must... I feel

New Addition:
Just ordered a 24 volt water maker, so that will add 1,000W per day to the used power.

Thank you very much for your direction ! It is helping greatly !

Alan