Solar panels provide an excellent solution for obtaining the electrical power needed  to support on-board electrical systems.  They are quiet, require little maintenance and are reliable.

While cruising, we take a very conservative approach to using electricity on board our 38 foot sailboat.  Even so, when considering the solar option, I concluded that  using solar panels to supply all our electrical needs would be expensive and would require considerable panel surface area.  With this in mind,  I set out to use solar power to augment the generation of power with the goal that we could be at anchor for three days without running the diesel to charge the batteries.

The 85 watt Kyocera KC85T is rated at 5 amps (17 volts) and measures about 26" by 40".  We can generate about 35 amp-hours on a sunny day on the Great Lakes by adjusting the angle 3-4 times a day for optimum efficiency.  Our energy usage is roughly 55amp-hrs a day at anchor.  Thus we run a deficite of about 20 amp-hours per day.

Here is how we calculated our energy usage per day at anchor.
Equipment            Amps            Amp-hours/day
Refrigeration          5                        20
Instruments            1                         4
Computer               4                         6
Lighting                  2 (avg)                10
Pumps                    5                         5
Other                     1                       10
 (propane monitor, etc.)
                                                ________
Total amp-hours                                55

When under sail we have an additional current draw of 20 amp-hours from our auto-pilot and instruments.

We have a 75 watt alternator on board and a 360 amp-hour battery bank.  Because we typically run the engine several hours on the days we are moving, the battery bank gets charged on those days.  This system works out well for us.

Each cruising boat has different patterns of energy usage and different requirements.  Calculate your usage, consider your sources of power generation and select the size of the solar array you will need.  Based on this, you can determine whether a single panel or multiple panels will be required to meet your needs.

Contact us if you would like assistance in determining the size of panel that will be required to meet your needs.

Top-of-Pole Mount

The top-of-pole mount offers excellent functionality for getting the maximum performance out of your solar panel.  The closer the surface of the panel is to being perpendicular to the rays of the sun the higher the performance (amps output).  Thus, the panel needs to be both tilted and rotated.  I have found that adjusting an 85 watt panel 3-4 times a day will achieve power generation of up to 40 amp-hours on a clear day on the Great Lakes.

A panel mount should be adjustable easily without the use of tools.  Our panel mount provides 13 tilt positions by simply pulling a pin, tilting the panel and replacing the pin.  The panel, which is atop our crane pole can be rotated 360 degrees.  We provide a pole locking mechanism to keep the pole from rotating on a windy day and have found that using the mechanism as a brake to limit free rotation of the pole works well.

As shown in the picture, our pole is mounted to the stern rail away from the boom so there is nothing to cast a shadow on the panel.  Shadows can significantly reduce the efficiency of a solar panel.  The pole is mounted high enough to clear the bimini yet easy enough to reach to adjust the angle to the sun.

My sense is that the 120 watt solar panel is about the maximum size
(31" X 48") to mount on the top of a pole such as ours.  The limiting factor is the strength of the stern rails that stabilize the pole.  A larger panel would require bracing struts from the pole to the deck.  Clearly this is possible but I would recommend mounting larger panels to a frame above the bimini, on dinghy davits or directly to the stern rail.

Pro and Cons:

Top of pole mount
Pros: Easily adjusted for best sun angle, clear of shadows, out of the way.
Cons: Limited size of panel that can be pole mounted.

Bimini frame panel mount
Pros: Can mount large panels, out of the way.
Cons: Cannot easily adjust for best sun angle, often have shadows cast by the boom, back stay or topping lift.