For those of you who have been paying close attention, you might have seen a little extra something perched on our roof in the last few photos we’ve shared online. Or you may have noticed that Cherie teased about leaving me behind visiting friends at AM Solar while she headed off to visit her mom in Florida.
Yes, the blatant foreshadowing is true – we at last have solar panels mounted on top of Zephyr.
800 watts of them!
And… it may be a bit of a surprise to some… we didn’t go thin and flexible!
New! We’ve added an entire Solar for RVs series to the blog with lots of articles on the topic. Included will be our on-going testing results of comparing flexible panels from GoPower, Renogy and Grape Solar.
Being Flexible About Going Flexible
When we began researching our Solar Challenge – this is what we set out to accomplish:
Our goal is to design a system for Zephyr capable of powering the bulk of our typical energy needs for several days without needing to regularly resort to a generator.
We expect that this will require somewhere between 500W to 1000W of solar, with the ultimate goal being to install as much power as we can while still looking good.
We knew from the beginning that keeping our curved-roof vintage bus looking good was going to be particularly challenging.
We were under the assumption that “Only thin panels that can meld with the roof lines will look good on our girl”, and we set out to find out whether any of the new crop of thin and flexible solar panels would prove worthy of the task.
We absolutely wanted to discover flexible panels that would be suitable – and we managed to get several representative samples to test.
But – the goal was never “flexible or bust”, and we even added a traditional glass panel to our testing arsenal.
We were always open to the possibility that maybe glass would win out in the end.
If only we could find a way to make it look good.
Even before we started – we were already aware of some yellow-flags around flexible panels.
Greg (the owner of AM Solar) had covered the roof of their personal RV with prototype flexible panels in 2013, and they had proven to have some major issues – as detailed in his original report:
The most serious problem we noticed was during a spell of 90 to 95 degree temperatures last summer. The thin covering over the cells (3mm thick) was not sufficient to keep the cells from “cupping”. This, in essence, caused each cell to form a shallow bowl which collects dust that any moisture will push to the middle of the cell. When the water evaporates, there is a small circle of dried debris that blocks enough sun to cause a power loss.
We had seen first hand how badly these relatively brand new panels were aging when we visited last year (and they are in even worse shape now), but with a new generation of thicker panels on the market for 2014 we hoped that the cupping issue in particular had been solved.
But that was only one of our concerns. As we researched more and began to test the sample flexible panels we had received, we began to become more and more aware of the potential downsides of going flexible:
- Not Walkable: Despite our dear friends Nikki and Jason Wynn dancing on their panels, we have come to learn that this is a REALLY bad idea. All the flexible panels currently available use mono-crystalline silicone cells, and even though they are encased securely inside a flexible material these crystalline cells can still develop microscopic cracks under pressure that will reduce their power output and shorten their lifetime. Therefore, walking (or dancing!) on these panels is NOT recommended – potentially making roof maintenance complicated (and dangerous) if we maximize the area covered.
- Not Tiltable: Normally tilting solar panels is more trouble than it is worth, but in the winter it can increase output substantially when the sun is low in the sky. Permanently installed flexible panels give up this flexibility.
- Scratching & Scuffing: After just a couple weeks of testing, all the flexible panels we were looking at began to show some signs of scratching and scuffing despite our careful handling. I can only imagine what scrapes against tree branches might do to a roof mounted installation! These are not just cosmetic issues – anything that keeps light from reaching the cells will lead to diminished power output. Glass by nature is just more scratch resistant.
- Longevity Concerns: Flexible panels tend to come with 10 year warranties, a third that of rigid glass panels. But having seen how badly the first generation panels aged after just a year on Greg’s roof, we had concerns on how well flexible panels will perform and how good they would look after just a few years – regardless of the warranty. Meanwhile, we have seen many rigid solar panels still looking and performing great that were installed on RV roofs a decade ago.
Heat Buildup: Solar panels, ironically, perform better when cold. But they absorb heat and get extremely hot in the sun. The framing on rigid panels have built in ventilation to help the panels stay cooler, while flexible panels get hotter and transmit all the heat buildup right into the interior of the roof they are mounted on. On a winter day (like today!) I am actually wishing for some of that heat absorption, but we were starting to have real concerns about the heat buildup potential from hundreds of watts of flexible panels on our roof in the summer. We were becoming worried that the heat build up would send us seeking power hook-ups to run the A/C sooner than we would otherwise.
- Essentially Permanent Install: The best way to install thin and flexible panels is to glue them to your roof, and after you do it is not at all an easy job to remove them down the road – especially without destroying the panels in the process. This makes it tricky to deal with defective panels, warranty swaps, upgrades to better technology, or even things like roof maintenance or painting the bus.
None of these concerns individually are insurmountable, but cumulatively there were starting to sway us away from flexible panels. We didn’t want to make a major investment into our roof that we would regret a year or three down the road.
Of the flexible panels on our radar, essentially every manufacturer had quality control issues that raised concern:
- Grape Solar: Grape Solar overall has a great reputation for their rigid panel, but they are the manufacturing partner responsible for the flexible panels that AM Solar had issues with last year. Though their new thicker 5mm PhotoFlex panel we have been testing seems to have addressed most of the issues, they still have last year to live down and their flexible panels clearly do not have a proven track record. Also – old inventory still seems to be out there too, making it tough to know in advance what you are getting unless you know what to ask for when ordering. (AM Solar sells the thicker panels now…)
We were however impressed with the performance of our test panels, and had we decided to gamble on flexible – the Grape panels probably would have been our choice.
- Renogy: Though Renogy declined to send us one of their Renogy Bendable Solar Panels for comparative testing, we have had our eye on them as the cheapest flexible option we have seen – even though they are also just 3mm thick. Lynne of Winnie Views recently wrote us to share: “Renogy called me last Friday night to say they discovered that the batch of flex panels they’d been selling were lacking a waterproof coating. So, they are now in the process of sending me 3 replacement (now waterproof) panels and getting my original 3 returned.” Fortunately, she had not permanently installed the defective panels yet!
Panel Sample #3*: We were surprised to discover these panels substantially underperforming expectations. And one of the panels actually had a bad crimp on the connector wire, leaving it loose and unreliable. When I shared my preliminary test results with the manufacture, they replied in e-mail with: “Something is wrong with those panels. We will need to swap them out. …. It sounds like the original panels you got with the square corners were the prototype panels that were from the first run. There was not a large run of these and I don’t think there are a lot of consumers in the RV industry that would have one… The units with the round corners are all we will be producing for the RV industry moving forward.”
We delayed our testing for a long while to wait for replacement panels, which ate into a lot of our available testing time.
So far, the replacement panels have indeed been performing great. But discovering such a major issue with the first sample sure doesn’t inspire confidence for doing a full-roof install.
They are also 3mm thick, and we’ve not had enough experience with them yet to know if cupping will become an issue with them.
- Panel Sample #4*: The major selling point of these panels is an integrated MPPT controller built right into the panel that is supposed to make the panels especially shade tolerant. But, in our testing, though the panel has performed well, we just haven’t seen any special benefits. And then, I just recently received this mail from the manufacturer throwing all our test data into question: “I went back on my record and I noticed that the panel I sent you had a manufacturing defect. Such module would have not be sent out to paying customer but we determine it would have been ok for your testing. If you look on the first two columns of cells there may be a short.”
- Note*: When I was an editor for a computer magazine, I occasionally busted manufacturers for sending me specially tweaked and optimized samples that performed better than what regular consumers would receive. But I’ve never run across the reverse.
We’re intentionally leaving the names of these two manufactures anonymous for now… the point of this post is the frustration of having taken so much personal time to do testing on these panels, and having late disclosures potentially invalidate our data. This is what rocked our confidence in proceeding with them.
What is it with flexible panels and manufacturing defects?!? The curse of a new technology just now coming to market, I guess.
We don’t mind being on the bleeding edge (as evidenced by over three years on lithium batteries!), but we do trust our guts. And our guts just weren’t feeling it when we contemplated making a major investment into any of these, at least not without more extensive testing in a variety of situations than we were able to accomplish while meandering around coastal Oregon.
All of these companies have good products and are worth taking a close look at, but especially with the semi-permanent nature of a flexible panel install, we just weren’t feeling ready to make that leap.
In the end, all these issues had us reconsidering our plans…
Maybe we should give up on having a large install, and settle for just a few hundred watts instead?
Or maybe we should consider waiting another year hoping for better and more proven flexible options?
Maybe glass panels are worth another look?
Opportunity Knocks & Serendipity Shines
We’ve been too swamped launching our book and the RV Mobile Internet site the past two months to write much more about solar, but we’ve continued to set up our ground deploy array of panels at various locations to test panels under a range of conditions, and we have gathered a lot of data that we are still planning to share.
But mostly, we’ve been too busy to think things through long-term to come up with a plan for what we wanted to do next. The past month was full of ridiculous amounts of mobile internet news to cover, and we didn’t have the mental bandwidth to think about solar planning much at all.
When we visited Eugene, OR last week – we really were only intending to accept the kind hospitality at AM Solar to camp for a few days, visiting with friends before dropping Cherie off for her flight to Florida.
We did not anticipate that we might have an opportunity to tackle an install – after all, AM Solar is usually booked months in advance. And, well, we didn’t think that we were ready.
We knew that we were heading into a period of extended boondock caravanning with Nina & Paul of WheelingIt and a winter of meandering around the desert southwest with lots of off-grid opportunities. Having solar on the roof would be extremely useful, and we were getting a bit frustrated constantly deploying and packing up the sample solar panels at each stop.
So when we saw that AM Solar had a last-minute cancelation and the service bay was open, Cherie challenged us as she left for Florida: “Glass or flexible – figure it out, get it done!”
We had only a day to come up with a plan, but when serendipity knocks – we don’t let the opportunity pass us by!
After all – if we wanted a good looking and professional install, no one does nicer work than AM Solar.
The Roof Plan
But could we come up with an installation plan that would look good on our roof?
To figure out what was possible, Greg and I engaged in the time-honored engineering practice of CAD – cardboard-aided-design. We used empty solar panel boxes, and played with several roof layouts figuring out how many panels we could fit, how they would look from the ground, and how they would mesh with the roof curves and obstructions.
We considered flexible panels, and a range of sizes of rigid glass options.
My initial paper sketches and measurements had me thinking that just 400W – 500W of glass panels would be possible, centered on the roof. More would require resorting to an asymmetric layout, awkward overhangs, and/or panel placement that just wouldn’t look good from the ground.
But once we got on the roof and started playing with cardboard, we discovered that the narrow GS100 glass panels could be placed side-by-side, tilted slightly, conforming to the curved shape of the roof. To enable this, we realized that the rigid panels could actually rise above the roof AC power conduits in a way that flat-mounted flexible panels actually could not.
Greg came up with the idea to replace our tall sewer vent with a new low-profile 360 Siphon RV Fume Extractor that could actually fit under the glass panels, opening up the center of our roof for panels where I didn’t think any would be possible.
I even realized I could hide our WiFiRanger Sky underneath the glass panels too, further freeing up roof space.
By being able to rise above obstructions – the rigid panels ironically enabled a more flexible roof layout than would have been possible with flexible panels! But by conforming to the roof curve, we still ended up with a symmetric design that should look great from all angles.
In the end, we figured out how to fit 800 watts of panels on the roof – 8x 100W GS100 panels. Each only weighs 14.5 pounds, adding just 116 pounds to our roof – which is nothing for our sturdy bus.
And we actually worked out the mounting and wiring so that the panels could be tilted up, or folded over onto their pair to open up a walkway for future roof maintenance!
With a plan in place, Greg told his team to prepare for a long day Friday (Halloween!) tackling the installation…
This was going to be a team effort – first I had to tackle taking down our array of WiFi and cellular gear from the roof to clear room for the AM Solar guys to work.
This also gave me the opportunity to run wires to roof mount the WiFiRanger Mobile Ti, and the new Wilson Sleek 4G.
After I cleared the way over night, the AM Solar team spent the day up on top – replacing the sewer vent, removing the old giant out-dated TV antenna, and meticulously installing and wiring up the eight panels.
Inside the bus, it felt like a ship at sea, rocking back and forth. Kiki was particularly confused.
To provide the optimum 34V input for our MPPT solar charge controller, we decided to wire up pairs of panels in series, and then brought all the wiring together in parallel in a combiner box – also hidden under one of the panels.
From the combiner box, we dropped a 4-gauge wire pair down through the fridge vent and into the electrical bay.
Interestingly – the 3/4″ conduit I had put in place over two years ago for a future solar install was actually too small for the thick wire, so we instead used the 1″ conduit I had been using for ethernet wires.
In hindsight – I should have installed thicker conduit the first time, but fortunately I had an easy backup option.
Down in the electrical bay, I wired the panel up to one of our Victron MPPT 100/50 charge controllers, passing first through a Midnight Solar Baby Box circuit breaker panel.
And then after the AM Solar team had gone, I returned to the roof to reinstall the cellular and WiFi gear neatly in a new location.
It was an exhausting marathon – but worth it.
The final bill was extremely reasonable too for such professional quality work – less than $4,000 for parts and labor.
Now that we have glass on our roof, does that mean we are done with flexible panels?
Not at all.
I set up the second Victron MPPT 100/50 to be able to easily support an external ground deploy, and we think that 400W or 600W of flexible panels at the end of a long extension cord will actually prove to be the perfect compliment to our roof mounted 800W.
For ground deploy, the strengths of flexible panels shine through – they are small, light, easy to setup, easy to aim towards the sun, and easy to store. And we don’t have to worry about the heat build up in this configuration.
And best of all – they can be generating power out in full sun even if our bus is parked in the shade.
I do have a lot of comparative data to share on how the panels we have been testing have been performing – and as soon as I have the time I plan to compile it up and share it. We will also be gathering more data in a variety of climates too, now that we have left Oregon behind.
But… We couldn’t go on hiding the roof of our bus any longer – so this post on the install had to come first.
We’ll get caught up sharing more of the other details later.
As I write this, it has been just over a week since the bus has last been plugged in to shore power.
In that time, we haven’t needed to run the generator.
But… It is winter in northern Nevada.
The sun is low in the sky, the days are short, and the mountains and trees cast long shadows.
This means that we have been needing to be always concerned with power conservation, shutting down the computers and the big inverter at night.
The literal cold reality of solar is that 800 watts of flat panels doesn’t generate an abundance of energy this time of year at these latitudes, and we have grown used to electric heat, induction and convection cooking, working all night and plugging in our electric block heater on cold mornings to start the engine.
Our all-electric coach setup will need some further refinements to thrive in these sorts of situations.
We are needing to re-learn our power-miserly ways – especially using our Mr. Heater Portable Buddy propane heater to keep the cold at bay, and putting our extra fuzzy warm sheets on the bed. Thankfully our water heater can still utilize propane, so our BBQ grill tank is supplying hot water for dishes and showers.
But during the day, we’ve been able to charge in excess of our usage and still get work done on our two huge monitors with power to spare for the evening. It has been fabulous.
We have been taking advantage of 400W of ground-deploy panels to supplement too – and being able to angle them makes a huge difference. For winter boondocking, angles really do matter. Despite the inconvenience we will need to get some tilt bars to maximize the power potential of our roof soon.
And for us – solar is about flexibility, not about never needing hookups. When the temperatures drop or work projects call for more abundant energy – there are plenty of places hookups can be found when needed, even in amazingly scenic places. It is all about finding the right balance – and at last having solar we have the flexibility to go without when we choose to.
But even if we are looking forward to our next full-hookup interlude, there is more boondocking ahead in our future – and it is great to contemplate some beautiful days out in the middle of nowhere.