Stop me before I spend -- Solar Panel Edition

Questions & Answers
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I’m always looking for the cool new tech to try. But when you’re hot for cool tech, it’s always wise to see if there are cooler heads who might prevail.

This time, my itchy trigger finger is twitching over a solar panel purchase, so I’d like to see if anyone in the group who’s knowledgeable about these things has an assessment.

What’s tempting me started with a relatively new article in Practical Sailor: Testing CIGS Solar Panels: Are Most of Us Holding onto an Inferior Technology? - Practical Sailor . (For those of you who aren’t Practical Sailor subscribers, this appears to be nearly identical to a post on the author’s personal website: Testing CIGS Solar Panels)

CIGS stands for Copper Indium Gallium Selenide. The two versions of this article claim it’s got two virtures that make it very interesting for boat installations. The first is that the technology purportedly allows for very thin, very flexible, and very tough panels. The second is that the panels are claimed to handle a great deal of shade and installation on curved surfaces, without nearly as much reduction in energy output.

There’s an overview article that also makes them sound pretty good: What Are CIGS Solar Panels and How Do They Compare to Silicon Panels - TERLI New Energy Technology Co., Ltd. Those folks don’t sell them, which makes the review a bit more reassuring. This article adds additional points that make the technology interesting for boats: better weather resistance (including hail), more reliable energy production across temperature ranges, light weight, even more readily recycled.

Although there are a bunch of other companies selling them, the company with the most pronounced web presence seems to be BougeRV.com, which has a 10 year product and 25 year performance warranty. The performance warranty part claims they will still produce at least 80% of original output after 25 years. Their line is at: https://www.bougerv.com/collections/flexible-solar-panels

As an illustration of the price difference, BougeRV sells a 100W rigid panel for about $91 USD and charges about $215 USD for their CIGS flexible panel.

So, with that background, folks – your thoughts, suggestions, advice?

Thanks,

– Bob

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Hi Bob,

My solar setup looks like this:

  • Two CIGS BougeRV 100W self-adhesive flexible panels on my hard top dodger.
  • One 100W “Wattstunde” rigid classic panel mounted over the davits, wide and narrow model.
  • One flexible Dometic NDS 60W panel glued on the hatch garage, because it fits nicely there.

Each of the CIGS panels has its own Victron MPPT 75/10 controller, and the Wattstunde also has one—so three in total. These panels provide enough voltage for the controllers to operate properly.
The Dometic panel runs on a Victron PWM controller, since its voltage is too low for MPPT.

My verdict: the rigid Wattstunde performs the best, because it’s not shaded and I can tilt it slightly to aim it at the sun. The CIGS panels each produce almost as much as the Wattstunde, but I do need to swing the boom aside for them to get full sun. If I don’t move the boom, the two CIGS combined will perform as good as one rigid panel without any shade.

I don’t keep track of what the Dometic produces, since that controller doesn’t have Bluetooth.

The nice thing about the CIGS panels is that they start earlier in the morning and keep going later in the evening—they perform better in low light. And it’s true: if they’re, say, 10% shaded, they’ll still deliver about 90% output. With the Wattstunde, shading kills the panel completely. With the CIGS, even if 90% is shaded, they’ll still push through at about 10% of capacity.

By the way, I’ve removed the lead-acid batteries from the boat and replaced them with Redodo LiFePO4 batteries. I also replaced the chargers, and for charging the LiFePO4 from the engine I use a Sterling alternator booster plus a 50A Victron DC-DC charger.

If I had to choose today between first installing solar or switching to LiFePO4, I’d definitely ditch the lead-acids and go LiFePO4. The boat sails better without the heavy lead-acid weight.

Let me know if you like details about the battery setup or pictures of the panels or something else.

Happy shopping,
Mark

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Hi Bob,

I’d second Marks suggestion to invest in power storage and management before investing in energy production on a boat.

I have very little experience with marine PV, but have done lots of analysis for home energy management systems. Home energy models need to be tweaked a bit to be useful on a boat but some general principles definitely apply.

Similar to home energy management, your question would be worthy of a very detailed analysis that would start with specifics of how you use your boat, where you keep your boat, and the other energy systems you have or plan to add in the future. Having the dialog in the forum would provide lots of insight for others ( like me) that are interested, but currently have other priorities for boat maintenance/upgrades.

Rob….

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Thanks, Mark. I’m with you 100% on LiFePO4. I’ve got them for my electric engine, and will be switching my house batteries to LifePO4 in the near future.

I’m very interested in hearing more about your set-up, although my details will differ. I’ll need to deal both with 12V house batteries and 48V engine batteries, both of which will charge of both solar and shorepower. Since I’m electric, there’s no alternator in the picture.

I’m really interested right now in who’s building/selling what, and is it any good? I.e., quality and performance evaluations of particular technologies and suppliers.

It’s interesting that you’ve got BougeRV CIGs; they seem to be the primary source. Were there competitors you considered before you went with them?

It sounds like your observed performance matches the claims well. The installation I’m contemplating is going to be on my own hard top dodger. The greater space limitations and location constraints on a smaller boat really favor using flexible panels that can handle low light and partial shade. They also raise the priority of finding panels in sizes and shapes that’ll fit in that more limited space.

The apparent knock on flexible panels until CIGs came along seemed to be their lifespan. My impression is that, prior to CIG, people were increasingly disappointed with their flexible panels after three years. How long have you had your panels? What’re your impressions of how your Dometic panel’s holding up compared to the BougeRV CIGs?

– Bob

P.S. Gotta through in another plug for cute features in Discourse. In Mark’s post, he used the term MPPT, which I have to confess I didn’t recognize. I highlighted it to look it up. If this had been Google Discussion, that’d be all I could have done – select it and cut-and-paste it somewhere. With Discourse, when I highlighted MPPT, I saw this set of choices:

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A much handier set of options. BTW, I’m not a big fan of AI. (My skepticisim is based on 43 years of professional experience performing, managing, and funding AI R&D.) However, I thought I’d try the “Ask AI” option. It popped up several things I could ask AI to do. I chose “Explain” and was impressed with what came back:

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As I said, cute feature.

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Sorry if I used terms without explaining them first. MPPT stands for Maximum Power Point Tracking. In short: a panel gives its highest voltage open circuit, its highest current short circuit, and the real power lies in between. An MPPT controller constantly looks for that sweet spot to maximize output.

This only works if the panel voltage is high enough above battery level. With small crystalline panels (few cells), there isn’t enough headroom. In those cases, a simple PWM controller can actually be more efficient.

I also agree with Rob that how you use the system should guide component choices, but I didn’t. I just filled all the “cosmetically acceptable” space on my Nonsuch with solar. My main consumers: a compressor refrigeration system, under‑deck autopilot, nav gear, electric winch/windlass, charging phones/laptops, and some entertainment.

I swapped a 400 Ah lead‑acid bank for 200 Ah of lithium. Why half? Because lead‑acids were only about 40% usable (down to ~60% SOC), while lithiums can safely go down to ~10% SOC. In practice my Victron BMV‑712 has never shown under 70%. Overnight I use about 15%, and by 11:30 a.m. it’s full again. Capacity is fine for now, though I’m eyeing future toys like an electric outboard for my dinghy.

Starting the Westerbeke and charging lithium from the alternator works like this: a 100 Ah lead‑acid handles engine start. It’s charged by the alternator with a Sterling booster for stronger, faster charging. A 50A DC‑DC converter then charges the lithium bank whenever the engine runs. These devices are made for the job — directly tying a boosted alternator to lithium would be unwise.

As for BougeRV’s CIGS panels: I checked competitors but came back to BougeRV for price, reviews, and their story. I installed them when the dodger went on — two seasons ago. On my previous boat I had walkable panels on an aluminum cabin top in the Caribbean. They rarely lasted a year; I replaced them several times. Back in Europe I chose a Dometic panel for the hatch garage, hoping that the tech has improved; to be fair, the old failures were cheap, unbranded units.

I hope I’ve answered all your questions without making this too long.

Happy shopping,
Mark