Solar Choices

[bobbydrango]

Hi
fascinated by the latest info (been out of touch with solar for years ),thought I had worked things out but obviously not .My boat has 3 old Arco panels (30 cell 16v and 33 cell 18v ) and 2 newer Kyocera 50w panels and 500 AH AGM battery bank .I just acquired a Sanyo 200watt panel (3 1/2 amps at 55v ) .My controller gave up working ( with the old panels ) so the only money I would like to spend is for a new controller .

.Reading the thread, the new panel's capacity would be wasted without a MPPT controller (there is a Gowe 60 amp on Amazon for $250 ) ?
Also would I wire up the 3 old panels in series to get to get approx 50v ,the 2 Kyocera seperately in series for 43v and then all 3 groups in parallel (3 arco ,2 Kyocera and 1 Sanyo )to approx 50 v ,connected to the Gowe Mppt .
I also have a Wind generator and seperate water generator( for offshore ),would these fit into the system or need a seperate controller?
I'm beginning to think that big 200watt Sanyo may not be worth all the extra trouble ?
By the way I have a 40' Trimaran so have lots of deck space to spread the panels around to minimise shading from the rig.
thanks

[noelex 77]

Welcome to the forum Bobby.

For a MPPT to work the Vmp of the panels has to be similar for parallel connection and the Imp has to be similar for series connection.

With the diverse mix of panels that you have with different cell numbers (30, 33 and 36) and sizes you are limited to using a non MPPT (PWM) controller with your older panels.

Unfortunately the 200w will need a MPPT controller. Hooking the older panels up in approximately 50v strings will result in some mismatched Vmp and I think the best solution is two different controllers. (Hooking up the older panels to a PWM controller and the Sanyo to a different MPPT controller)

Wind and water generators require a different means of regulation to solar. These generators cannot be switched off like a solar panel to regulate as they will speed up under the no load conditions. A dump resistor is used. Some solar controllers can be used to control this, but the configuration is difficult once again a separate controller is generally the best solution.

[s/v Jedi]

Originally Posted by wdkester

Jedi,
Could you give a link to Mark Coles testing results or his user name?

Also I'm wondering: 1. if you have series connected panels and you cover 100% of a panel, will it look like a direct short?
2. if you cover part of the panel you do get the same voltage but less current compared to an uncovered panel?
3. do most (all?) popular panels (e.g. kyrocera) have bypass diodes?

Mark is Cruisers & Sailing Forums - View Profile: colemj

1. No, it will become high impedance, so the opposite of a short. Most panels have 3 sections that each have a bypass-diode so that you have a chance of 1/3 or even 2/3 output with partial shading. When it is fully shaded, most have an extra diode to bypass the whole panel.

2. No, for every bit that is shaded, you loose array voltage, while the current stays the same. Power output is voltage x current so the decrease in voltage becomes the loss of power due to that shading. Here's the thing: with a parallel connection, a partially shaded panel looses so much output voltage that it is not used anymore. When a series connected array gets a partially shaded section, it only looses that bit of voltage, so with 6 panels it might go down from 120 (6x 20V) to 113V (5x 20V + 2/3 of 20V).

3. yes, all panels sold in the past 25 years or so have them.

[S.V.Duet]

Hello all, just my humble opinion I found this very good info.
Sailboat Solar - Installing Solar Panels and an Arch on a Boat
In fact I am following this install on my arch.

Lots of good information on this post thank you all..

[angelssson]

Originally Posted by GILow

Hello Cruisers,

I am tossing up between two solar options, after getting good prices on both the Kyocera 140W 12V panels and the 215W 18V panels.

In summary, I can fit a pair of panels up on our davits, and according to my calculations, a pair of 140W panels would be adequate, whereas a pair of 215W panels would be a bit generous in their power production. (We have light power consumption with the backup of an Aerogen 6, plus we have shore power and are unlikely to do much more than week long hops for the foreseeable future. Adelaide is VERY sunny pretty well all year round, the davits are rarely shaded. I plan on a 300AH - 400AH Lithium battery bank. Finally, I do have plenty of other places on the boat I could put panels, but I am keen to see if I can avoid putting panels anywhere they might get in the way, such as the old pair currently ont he cabin roof.)

I need to replace my current regulator, no matter which I choose, but I will need a MMPT reg for the 215s, whereas I would only need a PWM for the pair of 140s.

The cost for the panels are practically the same, so economically, its a no brainer when it comes to the panels themselves. The cost of the regs are very different, of course, but ASIDE from the extra cost of the MMPT regulator, are there other concerns I should factor in to the equation?

I have read of interference from the MMPT regs with SSB radio, but I don't have one of those any more, all we have at the moment is VHF and AM.

Thoughts or cautions on the above...?

Matt

Hello,
Just wondering why you have expensive Lithium batteries installed as against regular lead acid ones, in view of what said in this link:
Sterling Power Products: What is the best battery to use for an auxiliary charging system?

[wdkester]

Originally Posted by s/v Jedi

Mark is Cruisers & Sailing Forums - View Profile: colemj

1. No, it will become high impedance, so the opposite of a short. Most panels have 3 sections that each have a bypass-diode so that you have a chance of 1/3 or even 2/3 output with partial shading. When it is fully shaded, most have an extra diode to bypass the whole panel.

2. No, for every bit that is shaded, you loose array voltage, while the current stays the same. Power output is voltage x current so the decrease in voltage becomes the loss of power due to that shading. Here's the thing: with a parallel connection, a partially shaded panel looses so much output voltage that it is not used anymore. When a series connected array gets a partially shaded section, it only looses that bit of voltage, so with 6 panels it might go down from 120 (6x 20V) to 113V (5x 20V + 2/3 of 20V).

3. yes, all panels sold in the past 25 years or so have them.

Thanks Jedi

I was unaware of how the internal diodes worked and have in the past used parallel connections. This was out of fear that if the entire panel was shaded it would appear as an open circuit and thus get no output from the system.

I think it should be noted that if you only have 2 panels in series, and one of them were partially shaded, you would lose 1/6 of your capacity. Perhaps you would lose even more if they were parallel. The more panels you have in series the greater the benefit.

Now I'm wondering about the panel layout of these 3 sections. Do they lie along the long axis or the short axis? Hopefully, this is answered in Colemj's posts.

Thanks again

[Dsanduril]

As Jedi says, with bypass diodes you lose voltage (voltage is a function of the number of cells, current is a function of the surface area of each cell). So, with two panels in series and one section of one panel you'll lose 1/6 of your voltage. As long as the voltage is still high enough to drive the system and your controller can deal with it you will lose about 1/6 the power.

In parallel you will lose 1/3 the voltage on the shaded panel. 36 cell panels are usually around 18/22V Vmp/Voc. So, if you lose 1/3 of your voltage you will be down to 12V Vmp and 14.3V Voc. That means your panel will likely not produce enough to do anything so you may lose the entire panel's output. And, depending on wiring, diodes, and controllers it could drag down the unshaded panel. Higher cell count panels may still be able to charge a 12V system, but...

A controller with boost capability may be able to help, but likely only if you have a single controller per panel.

[s/v Jedi]

In theory, the series-setup wins from parallel setup in 99% of all possible shading scenarios. Even when there is no shading, the series-setup would win because of the reduced losses in the cabling (lower current).

So it is about shading. We have had members testing this; I remember somebody posting results from partial shading where all panel output was lost with two panels in series and one panel with partial shading. It turned out that the part he shaded was covering part of every section of the panel (duh!). But that detail only came up after days of discussions. This is typical for these threads.

Here is a diagram that should help; think about how shadows from boom or rigging move over the planned panel position to find out which is the right orientation:

[downunder]

Originally Posted by CarinaPDX

Dave- I probably overreacted - sorry.

What you and Jedi have added is how an MPPT works; I have just taken it as a given that it does work at Vmp. Looking at one MPPT manual (Morningstar) the efficiency at 16.5 Vmp is between 97-98% efficiency, dropping to 92-93% at 98 Vmp. I take that to mean that the greater the DC-DC converter voltage the greater the loss, somewhat reducing the advantage of the higher voltage.

I have only looked at systems in the few hundred watt area, and the 5-10% efficiency gains aren't enough to justify the additional cost of the MPPT controller when compared to putting the money to another panel.

Jedi's 25% gain is very impressive (as is the massive 660W of panels!). I think it would be interesting to break out what is happening there. Were the panels' Vmp higher than 19V? Or are they operating at 24V or higher? What was the loss due to cable resistance? There is more to that story than simply a more efficient controller.

All good fun...

Greg

For a new installation on a multihull these days that would be considered at the low end for installation. Plenty of installs these days in excess of 750-1000kw.

Thanks Jedi for that explanation.

[Dsanduril]

Nice graphic (picture worth a thousand words and all that). Too bad the original author can't count, that's a 54-cell panel. Doesn't make a difference to the meaning, just that we all let things slip through from time to time.

[CaptainChaos104]

Originally Posted by downunder

For a new installation on a multihull these days that would be considered at the low end for installation. Plenty of installs these days in excess of 750-1000kw.

Thanks Jedi for that explanation.

I'm in the middle of planning the solar array for a new boat and have selected four Kyocera KD250GX-LFB2 panels. Under standard test conditions (SCT) for each panel, Vmp is 29.8V and Imp is 8.39. Kyocera also publishes Nominal Operating Conditions (NOC) which is 800W/m^2m irradiance (instead of 1000), 20 deg C ambient/45 deg C panel temp and under these conditions, Vmp is still 26.8V and Imp 6.73 amps for Pmax of 180 watts.

I plan to wire 2 of the panels in series fed into one Outback Flexmax Extreme MPPT controller and duplicate the setup with the other two panels. All of this feeds a batter bank of four 260AH batteries (1040AH total).

On our previous boat, we had two Kyocera 215W panels with a PWM controller and though the system was reliable, I don't think we got the maximum benefit.

We live aboard, don't like being in marinas and prefer to not have the noise of the generator or main engine. On the previous boat, we had to run the generator for a few hours every 3 days or so unless we turned off the refrigerator. Without the frig, the two panels kept the batteries full the vast majority of the time.

On the new setup, we're hoping we'll never have to run the generator or main engine unless it rains for a week without enough wind to turn the wind generator.

[s/v Jedi]

Originally Posted by CaptainChaos104

I'm in the middle of planning the solar array for a new boat and have selected four Kyocera KD250GX-LFB2 panels. Under standard test conditions (SCT) for each panel, Vmp is 29.8V and Imp is 8.39. Kyocera also publishes Nominal Operating Conditions (NOC) which is 800W/m^2m irradiance (instead of 1000), 20 deg C ambient/45 deg C panel temp and under these conditions, Vmp is still 26.8V and Imp 6.73 amps for Pmax of 180 watts.

I plan to wire 2 of the panels in series fed into one Outback Flexmax Extreme MPPT controller and duplicate the setup with the other two panels. All of this feeds a batter bank of four 260AH batteries (1040AH total).

On our previous boat, we had two Kyocera 215W panels with a PWM controller and though the system was reliable, I don't think we got the maximum benefit.

We live aboard, don't like being in marinas and prefer to not have the noise of the generator or main engine. On the previous boat, we had to run the generator for a few hours every 3 days or so unless we turned off the refrigerator. Without the frig, the two panels kept the batteries full the vast majority of the time.

On the new setup, we're hoping we'll never have to run the generator or main engine unless it rains for a week without enough wind to turn the wind generator.

This setup sounds good. You need to work out where and how to mount the panels, and which are to form the pairs. Normally the best results are found when taking panels on port side as a pair, and the others on starboard as the 2nd pair. Mounting all of them lengthwise.

I think you can use the Flex60 controllers as I have 660W into one of those (as opposed to the Flex80)

[GILow]

Originally Posted by angelssson

Hello,
Just wondering why you have expensive Lithium batteries installed as against regular lead acid ones, in view of what said in this link:
Sterling Power Products: What is the best battery to use for an auxiliary charging system?

Hi Angelssson, the battery choice thing is a whole separate discussion. It has been discussed at great length on C.F. Some big threads on the issue. Suffice to say, after WEEKS of reading, I came to the conclusion that Lithium would best suit our particular needs.

Matt

P.S. That particular link points to an extremely limited scope article. Regardless of the veracity of the arguments presented, it does not even cover a fraction of the available battery chemistries.

[CarinaPDX]

Originally Posted by s/v Jedi

In theory, the series-setup wins from parallel setup in 99% of all possible shading scenarios. Even when there is no shading, the series-setup would win because of the reduced losses in the cabling (lower current).

My takeaway from this is that there are an awful lot of 12V (nominal) solar systems that are using undersize cables. That is certainly what I have seen. And of course when the cables are too small, the voltage drop increases, and the panels may be operating above MPPT and thus with reduced output.

Of course if the cables are the proper size there is no advantage per se of series over parallel in unshaded conditions. There still remains a small (percentage-wise) advantage to MPPT controllers, but I suspect that much of the advantage of the MPPT controllers used with the same cables derives from the initial poor design of the parallel system with undersize cables.

Whichever way one goes, I don't see any substitute for working out the total design in order to achieve the best efficiencies.

Greg

[s/v Jedi]

Originally Posted by CarinaPDX

My takeaway from this is that there are an awful lot of 12V (nominal) solar systems that are using undersize cables. That is certainly what I have seen. And of course when the cables are too small, the voltage drop increases, and the panels may be operating above MPPT and thus with reduced output.

Of course if the cables are the proper size there is no advantage per se of series over parallel in unshaded conditions. There still remains a small (percentage-wise) advantage to MPPT controllers, but I suspect that much of the advantage of the MPPT controllers used with the same cables derives from the initial poor design of the parallel system with undersize cables.

Whichever way one goes, I don't see any substitute for working out the total design in order to achieve the best efficiencies.

Greg

No, the 25% extra power with MPPT is from the MPPT technology alone. Reduced cabling loss is still to be added to that. Maine Sail has a nice video up which shows how this works

Edit: here it is:

http://www.youtube.com/watch?v=-uhj6dgjbhw