Saturday, October 10, 2015

Did I Say Normal?

Well, things are truly getting back to least from the perspective of the weather causing me problems.  Today it is overcast, rainy, and cool...none of the qualities you want in a good day for fiberglass (OK, I'd like the overcast, but the 60 degree high and intermittent rain can go away).

We toyed briefly with the idea of running up to the boat show, but decided that the things I would be looking for were probably easier to find and figure out online.  So, thus far I've been playing with various solar panel configurations trying to come up with a design that is cost effective while maximizing the power output.

From a cost perspective, when looking only at the panels themselves, it seems that $1 (U.S.) per watt is considered a good price for rigid panels.  There are flexible and semi-flexible panels as well...but these are newer technology, less efficient than their rigid counterparts, and more expensive. Having spent a lifetime in the software industry chasing cool new high-tech stuff, I've learned to appreciate trailing edge technology.  The tried and true and usually cheaper options than the latest and greatest.

But price obviously isn't the only criteria, even if it is an important one. Even on a catamaran, there is only so much space where solar panels can be mounted. In my case I'll (hopefully) soon have a nice new hardtop that can support a number of panels.  There are other, and possibly better, places to put solar on the boat, but I'm not interested in taking on more structural changes to the boat right now, so for this discussion, I am limiting the location to the available space on the hardtop.

Trying to leave a space along the top to provide a walkway for dealing with the boom (and maybe a place to set the boom to avoid some shading of the panels), I came up with several potential placements.

I started by looking at a rather large Kyocera panel. Their 325 watt panels are just over 65 inches long and almost 52 inches wide.  There is only enough room to fit two of these on the top.  I was hoping for a bit more than 650 watts and at about $1.20 per watt, I was looking for something a little better in that category too.

65.5" x 39" panel placement, such as Renogy 270's.

Next I looked at panels in the 270 watt range.  Taking a look at the Renogy Monocrystalline panels, I was able to place 3 of them on the top while maintaining a walkway and access for the helm sail viewing port.  This would give me 810 watts of solar (theoretical...I know actual will be less) for about $765 plus tax and shipping. Under a buck a watt, not too bad.

47" x 21" panel placement, such as Renogy 100's.
While on the Renogy web site, I also looked at the size of other panels, in order to get to an option that would allow me to increase the number of panels, I had to step down to their 100 watt option. There are a couple variations on the placement, but it comes down to the fact I can squeeze 9 panels on to the top.  That is 900 watts.  A good amount of power.  Unfortunately, the smaller panels tend to increase in price per watt.  At $150 per panel, that is a total panel cost of $1350 or $1.50 per watt (all prices U.S. not including taxes or shipping).  And all of those panels would increase wiring cost and complexity as well.

62" x 32" panel placement, Grape GS-S-195 panels.
In between the two above options, I found the Grape 195 watt option. I seem to be able to fit 5 of these on the top, with some limitation to the access walkway (only 1 foot 3 inches between panels and one panel blocks the aisle).  This configuration gives the highest total wattage at 975 (again theoretical).  And these panels are exactly $1 per watt.  Unfortunately, I know nothing about Grape clearly more research is required.  But chances are even if they are an unknown, there are probably other manufacturers with similar specification panels.

While there are a lot of different panels out there with varying sizes and specifications, it seems that many of them are pretty similar in dimensions so I figure one of the above three placements will likely be what I end up doing.

In other news, the past two days have been good for fiberglass so we were able to get glass laid up on the PVC handhold/dodger holders.  There is at least one layer on everything, with second layers applied to the rails along the sides. We used the 10 ounce fiberglass for the straighter runs where the PVC was used and chopped strand for the more difficult complex curves of the corners and other foam details.

So, I guess things are normal...getting work done, in between rains, bad temperatures...and hurricanes.


  1. Thanks for sharing your research. We have solar, but we're thinking about upgrading in the future as the panels are older and don't produce enough for our needs. Looking forward to seeing that hardtop installed :-)

  2. Hi Mike
    I have been following your progress on the top, and I am sure that I would not have been able to do what you have done! I have done some small jobs, and have a huge appreciation for acetone to clean up the fingers, elbows and even my forehead. Oh well, did you know plain old vinegar does a pretty good job of cleaning off resin? Try it.
    Anyhow, when I did our solar system aboard Saltrun, I faced the exact same design questions that you did. Remember, the effects of shading on these things cannot be over-emphasized. Even a very small amount of shading (the shadow of a reef line or halyard across a panel) will effectively kill it's output. And, if wired in series to save wire guage problems to your charge controller (Amps stay the same, Voltages add up), the entire bank is rendered dead. Stay out from under that boom, our panels are a couple feet away, and run lengthwise down the edge of the top for that reason.
    The other consideration is in regards to those semiflexible panels. They have a couple advantages that are worth considering. They do not require complicated mounting and racking like the rigid panels do. They are made to twist, which will crack the glazing on the rigid panels and kill them. If you use rigid panels like I did, be sure to get them on a good mounting system to protect them (not cheap to do, believe me.) The second thing is weight. The flex panels are really light, and compared to the solid panels and their required mounting fiasco, this is a huge bonus. They might actually be less expensive when you figure in the cost of the appropriate mounting systems for the rigid ones. I believe the flexible panels can even be stepped on (though I would not), and they are put down with adhesive. Sounds simple to me!

    1. I'm aware of the shading issues and some of the mounting issues. I also heard of a fire related issue with some of the flexible panels. Knowing how headlights on cars turn yellow over time, I wonder how long it will be before they find a similar issue with the flexible panels. Mounting may be a pain with the rigid panels, but I do like the more proven nature of them.

      How much solar were you able to put on your boat?

  3. We put 360 watts on each side of the top, each side in series (24 volts each panel). There is a guy in Ocala that we bought the mounting rails from, they are very robust, and only raise the panels up around 2.5 inches. The panels work better with air having the ability to get behind them and help cool them, as they really get hot in full sun.

    1. 720 watts, did you find that sufficient or did you wish you had more? I have heard that about the panels, actually a couple people suggested integrating panels into the top and leaving the bottom open to allow for cooling...but I didn't like the idea of building my top so it required a very specific size panel...since technology changes faster than I can build/rebuild a top. ;-)

  4. hi Mike,
    My two cents. I like the 195 watt Grape Solar layout , output , specs and cost per watt. Layout -you end up with enough space to walk and deal with boom and sail. You can easily staddle the 32" one in the front if needed. The output- I've only heard people complain they don't have enough power , never too much so this gives you most for space and $s total and $s per watt. Specs- like that these panels are in the 30 volt range output. This allows you to go parallel with reasonable electric wire size and avoid the series problems. You would have to deal with 5 wires up and 5 down but probably in the 12AWG size range each so not too much to send via wire chases.They are mono panels with reasonable eff rating, I'd go with silver frame and white underside to keep the solar heating to a minimum . Cost - $1 per watt with a 10 and 25 yr warranty is good. Not sure if you can rely on the longevity of any solar panel co give the intense price competition.. Grape seem to have ok ISO certs so they seem to have their manufacturing in ok shape. Having 5 panels gives you 5 shots at generating power.- some redundancy.
    Doug in VT

    1. I like the 3 and 5 panel configurations the best. Both have pros and cons, so I'm still up in the air on that. I'm particularly concerned with shading making one or more panels issue that increases with the real estate used by the 5 panel layout.

    2. hi mike,
      brain fart. if you did the 5 panels, you could have 2 sets of 2 panels in parallel and the fifth by itself. since the panels are all the same voltage. that would make for 3 wires up 3 wires down plus ground
      Doug in VT