Nimrod catamaran: Solar rethink

This post is a bit meandering, as I have toyed with various possibilities:

1) Replace the thin flexible panels on the canvas shades.
2) Replace the solid glass panels over the davits.

If you want to 'cut to the chase', I have made a decision to order two thin flexible 180 watt panels made by eArche, and distributed by Solar 4 RVs. We will keep the old BP3125s over the davits, and their frames will not need to be changed.

A very kind Seawind 1160 owner gave us his surplus solid Targa infills. These are the panels to take the place of the canvas shades over the cockpit. The canvas shades are a bit of a death-trap. Unwary crew can promenade down the solid walkway beside the boom, and if they haven't ensured that the boom is tethered securely, an unexpected gust of wind can cause the boom to sweep them off the walkway like a windscreen wiper sweeping a bug off a windscreen. Said crew then steps on the canvas shade and falls into the cockpit, breaking things.

So we were delighted to be given these solid infills.

Meanwhile the 120 watt SolarPlex thin flexible solar panels that we installed by zipping them onto the canvas have deteriorated. They were new in mid 2014, so they are now 3½ years old. They have gone all milky and opaque.

BP3125 panels over the davits. SolarPlex SR120 watt thin panels zipped into the canvas.

It may be that all flexi-panels are not the same. I found this NZ supplier who distinguishes the different models. SolarPlex is Chinese, and uses PET as the plastic coating. SolbianFlex is Italian, a lot more expensive, and uses a 'high-tech polymer'. A discussion on PET degradation on the Cruiser's Forum here.

We bought ours from Solar Future, a company that appears to have gone broke. Their website is visible on the Internet Archive. They sold the three ranges: SL, SP and SR. Ours are the cheaper Chinese SR Solarplex brand.

Our setup is very similar to Alan Hunter's Talisker. Alan has Solbianflex panels, (although they look identical to our Solarplex panels). He has larger Enerdrive 200 watt panels over the davits.

So the question I want to explore is how to reform our solar power. On the Seawind FaceBook page a few others have expressed an interest in following the topic.

Nimrod was launched in 2008. The BP3125 panels were fitted then. They produce 125 watts each. The original solar regulator was a Steca Solarix PRS 2020, which used the PWM system and was good for 20 amps. When we were struck by lightning in 2013, I replaced it with a Morningstar Tristar TS-MPPT-60. If you haven't understood the importance of MPPT, I suggest you check it out. It made a huge difference to us when we changed from PWM to MPPT, as I discussed in an earlier blog. In addition, if you want to join panels of different voltage together in series, it is essential that you have a MPPT controller.

So. What developments have occurred in the last 9 years?

Efficiency

A massive amount of research has been going on. The efficiency is the ratio of the solar energy hitting the panel and the electrical energy passing out of the wires.

My BP3125s have an efficiency of 12.3%. Modern LG NeON R 360 panels have 20.8%!

Size

Panel	Length mm	Width mm
LG NeON 330W	1686	1016
Irex IR205M-72	1580	808
Enerdrive 200W	1580	800
BP3125	1510	674

If one put some LG NeON 330W panels over the davits, in place of the BP3125s, they would be 176mm longer, and 342mm wider. Would that matter?

Compared to Talisker's they would be 106mm (4") longer and 216mm (8½") wider.

I think that would be acceptable. Opinions from others welcome.

Panel	Watts	Weight kg
LG NeON 330W	330	18.0
Irex IR205M-72	205	15.5
Enerdrive 200W	200	15.3
BP3125	125	12.0

Panel	Price	Voc volts
LG NeON 330W	$365	40.9
Irex IR205M-72	?	45.4
Enerdrive 200W	$359	43.7
BP3125	Out of stock	22.1

If you create a sub-array of two or more in series, it is important that the sum of the Voc figures is below the limit on the solar controller. The Morningstar Tristar TS-MPPT-60 can take 150 volts. Thus a single string of four panels in series would be risky, but two strings of two panels in series, with the strings connected in parallel should be fine.

Panel	Impp amps	Efficiency
LG NeON 330W	9.8	19.3%
Irex IR205M-72	5.62	16.1%
Enerdrive 200W	5.37	?
BP3125	7.23	12.3%

The issue with Immp is that if you buddy up two panels in series with widely differing ampage capacities, it may cause a restriction in the current flow and a heating of the smaller cells in the series. This may reduce the system performance and /or cause premature aging of the small modules.

I asked MorningStar tech support about possibly pairing some LH NeONs with my BP3125s. He said: 'Although the rated current (Imp) of the two modules is slightly different (7.23a and 9.8a), the current mismatch is much less than your present configuration. I do not expect much (if any) current limiting due to this mismatch, in real-life performance.'

Meanwhile, Mike Rees from Seawind in Vietnam tells me: "We are still in the process of getting the panels in but we have worked out a way to fit 1.12 Kw if required. At this stage we are looking to have a 350 Watt panels either side of the tri-fold door line above the cockpit. 820mm W x 2600mm L x 2.5mm Depth. That's 700 Watts on the roof + the standard 2 x 210 Watts above the davits. This configuration would also fit on the 1160."

The ones he has been considering are made by DAS Energy in Austria. The panels look very nice, with ETFE-Film on the front, which should be more resilient than the PET surface layer that we had on the SolarPlex SR120s.

I note that the new ones being tried in Vietnam are 2600mm long. That is longer than the solid infills which are 1900mm long. In other words, the thin flexi panels would pass over a join in an older 1160 being fitted with solid infills, which might make for an irregular connection to the roof.

When I approached the decision to buy the DAS Energy panels I was put off by the high cost of transport. Two 200w panels delivered would have cost about $2,000, plus possible tax.

2) Replace the solid glass 125 watt panels with larger 200 watt panels.

Alan Hunter of Talisker strengthened the frame that supports the solar panels when he increased the size of his solar panels over his davits.

Compared to BP3125s

If I were to put on the LG NeON 330w panels, the overlap would be significant. I'm inclined to go with an extension to the frame using welded stainless steel.