Tuesday, September 1, 2015

Solar Panel Installation & Experience

It's now been ten months since we installed solar panels on Mowzer and so here's a more technical post on the details of the installation and our experience with it so far.

One of our primary goals when we moved aboard Mowzer was to be as energy self-sufficient as possible with solar and/or wind power generation.  If nothing else, our five years of visiting the boat in it’s charter configuration had taught us that the last thing we wanted to do was to have to run the engines or a generator for a couple of hours a day, both from a noise point of view but of course also from a desire to use as much renewable and free energy as possible.  Of course the energy is not really free because you have relatively high setup costs for both systems, but once up and running, they have relatively low operating/maintenance costs.

For solar, we mapped out the cabin top and bimini top space, documenting where all our lines, blocks, cleats and other sailing paraphernalia lie and while still at home, mapped out a plan to add thin, flexible solar panels to the tune of 345 watts.  The flexible panels are a bit less efficient than rigid but much lighter and they don’t require a frame to support them so there is pretty much a weight/installation cost vs. efficiency equality in our minds.

We ordered four Solbian panels for delivery to St. Thomas:  two square 90W panels and a rectangular 40W panel for the bimini and one rectangular 125W panel for the cabin top.

Once in St. Thomas we played around with the configuration to get maximum sun exposure with the assumption that most of our time will be spent in the Caribbean sitting at anchor with the wind blowing from the east which puts the best energy producing sunshine on our mid-line in the summer months and slightly to starboard in the winter months.  The one disadvantage of mounting on bimini and cabin-top is that they both tend to sweep upwards from fore to aft which results in the panels being more angled away from the sun in the later afternoon hours - pretty much after 4pm there is little solar production.

Three panels sewn to our bimini and one affixed to the cabin top.

To mount the panels we used two different methods:

For the cabin-top we first tried sticky-back Velcro but this quickly succumbed to the wet conditions and the adhesive really only lasted a couple of weeks.  We toyed with using a 3M adhesive product to stick either the panels or the velcro down but really didn’t want to deal with the mess and in hind-sight, we ended up moving the panel a bit so we were glad we did not go with a fully permanent solution in the beginning.  Our final installation used 3M Lock-Tite which holds the panel solidly in place even in 35 knot winds.

Cabin top panel affixed with 3M Lock-Tite under the leading edge.

For the panels on the bimini top we used the placket and velco method described here http://www.bruceschwab.com/uploads/solbian-to-canvas-guidelines.pdf .  The only addition we made was to provide a little more rigidity for the panels by inserting a piece of corrugated plastic board between the solar panel and the bimini.  I used my SailRite machine to sew the Velcro to the panels in a long, wide zig-zag stitch.  As with the cabin-top panel, these panels have remained in place through 35 knot winds but if we felt the need, any or all of the panels are easily removed and stored inside.

To protect wires from sun, they run under a flap of Sunbrella on top of the bimini.

Profile showing the thin solar panel with velcro, the corrugated plastic board and velcro on the bottom.

Velco plackets sandwich the two layers together and hold them to the bimini.

I didn't make my flaps quite big enough to give full coverage and protection so the exposed Velcro will eventually break down in the sun.

Each panel has two wires that we connected to longer wires with MC4 connectors which we routed around the bimini and above the main cockpit door.  We drilled two holes into the port bulkhead directly below the bimini where we installed gasketted conduits to pass the wires into the cabin, and then routed them down behind the navigation station and into the berth below.  We mounted four MPPT controllers each protected by a 15 amp fuse, on the wall in the berth where they are easily visible and monitored.  The outputs are then combined, with the negative run through a shunt to measure real-time amperage and then connected to the negative bus in the electrical box under the port berth.  The positive runs through a switch under the berth which in turn is connected to the house battery bank in the port engine room.

Conduits in the bulkhead feed the wires inside the cabin.
MPPT controllers and 15 am fuse.

When sitting at anchor, we pull the boom as far to port as possible so that all four panels get full sun.  We also ease off lines that cast shadows on the panels and tie them off at the mast.  At maximum sun, we routinely see 15 to 18 amps at the shunt but lower if the battery charge exceeds 85%.

We installed our solar panels in November and they were our only means of renewable energy production through the winter months in the north-eastern Caribbean.  We have a house battery bank of 500 amp-hours and in general we found that on a good sunny day we still needed to run our generator or engine for approximately an hour a day.

To give you an idea of our energy use, our main consumers of power are our refrigerator and freezer and for much of the time we do not turn on our freezer, opting to shop more often.  We do not use our big anchor light since that consumes 5 amps, instead opting to hang a 0.1 amp LED ‘anchor light’ in our rigging.  (As an aside, we will be upgrading our main anchor light to LED once in Grenada.)  All of our inside lighting has been converted to LED bulbs so very little power draw there, we have our propane gas solenoid that gets its workout at dinner-time.  We have an electric water pump for the galley and heads, and then there are the electronics that need a daily charge - two tablets, a phone and a laptop computer.  Underway, we have one chart plotter, various navigation instruments and Sulu, our trusty electronic auto pilot.  In busy anchorages the VHF radio is on all of the time.

What have we learned and what would we do differently?  What are we going to change?  Well, we definitely need either additional panels or to add a wind generator to this configuration since 345 watts is just not enough for us.  We also find that given the angle of the cabin and bimini we really only have good power production between about 9am and 4pm - six to seven hours on a good day.  That leaves 18 hours when we are losing the power struggle with our batteries and without a boost on the batteries at about 9pm our morning levels are just too low to maintain good battery health.  If we turn on the freezer we have to add more generator time.

So, in April we bit the bullet and decided to add a wind generator (more on that in a separate article) and are still toying with the idea of adding more solar.  We will most likely upgrade our bimini so that the entire surface is solid rather than the current configuration of the solid central area with canvas on the sides.  This would give us a more secure attachment point and more water-proofing for the cabin below.  The bimini has lost its water-proofing over the years and having the sewn plackets has greatly reduced it further since water pools against the Sunbrella ridges and finds it’s way through the stitching holes.  We would also consider adding a rigid panel on a frame over the dinghy davits that would allow us to angle it toward the later afternoon sun and therefore extend our hours of solar production.  For the moment we will hold off on more solar panels until we have completed a full year in the Caribbean since we fully expect that the summer months (hurricane season) will be more cloudy and therefore would not gain us as much solar production anyways.

Overall impression:  we love the Solbian panels and the option that the thin plastic and slight flex gives for easy mounting options.  The only maintenance we’ve had to worry about is to clean them with fresh water after a salty crossing or when in an anchorage with dust blowing from land (or the Sahara).  Where wires are exposed to the harsh sunlight we have installed Sunbrella sleeves to protect them.  We are careful not to walk on the panels and in the course of ten months we have only one small mark on one that we can only assume is from a rope slap when a genoa line flogged.