Solar power can enhance the performance and reliability of electric boats. We have developed lightweight integrated solar canopies as options for our prototype boats, wherein the panels are installed without frames onto a canopy constructed of square aluminum tubing with the panels forming the roof. We use Unisolar panels, the highest output amorphous type panels available. These panels are lightweight and are flexible enough for camber to be built into the canopy so the rain will run off.
The canopies provide backup propulsion and increased range. They propel the boat without drawing from the batteries, and recharge batteries while at rest.
Canopy Size and Capacity
The Electrocat canopy consists of twelve 29" x 54" panels, which produces 14 amps at 48 volts or 672 watts = .9 H.P.
The Explorer canopy consists of four 29" X 54" panels which produce 4 amps at 48 volts or 192 watts = .25 H.P. For the 36V 12 battery option, 3 panels are used for 4 amps at 36V.
You select what you do with the solar amps with the throttle. You have an ammeter to measure motor current, another to measure solar charging current. If motor is stopped solar current charges the batteries. If you throttle up motor current to exceed solar current the difference comes out of the batteries. To run on solar alone, as you might want to, to keep from over discharging your batteries, just set motor current equal to solar current. There is no switching required to change from solar assistance to batteries, running on solar only, or charging batteries while stopped.
Solar Boost while Underway
The Electrocat solar canopy will increase your daily range from 99 to about 115 miles when cruising at 25 amps (5.4 MPH). When cruising at 55 amps (7 MPH) your daily range will be increased from 50 to about 62 miles. (Based on an assumed average of 10 solar amps for 8 hours per day.)
Running on batteries and solar will increase the Explorer daily range from 49 to 56 miles with 8 batteries or from 77.5 to 84 miles with the 16 battery option. (Based on assumed average of 3 solar amps for 8 hours per day.)
Running on Solar power only
From the graph in Figure 1, Article 1 you can determine the speed at which you can run on solar power alone for both the Explorer and the Electrocat which is 2.4 knots (2.76 MPH) and 3.9 knots (4.48 MPH) respectively. Although not fast enough for normal operations, these speeds are fast enough to add a degree of safety and fun. For example, you'll never need to a tow when the sun is out. On the fun side, it can be fun when cruising to integrade solar power into your float plan. You can travel a bit faster and make longer distances between charging points.
Solar charging while stoppedThe Electrocat batteries will be recharged at a rate of about 2.5 hours for each hour of cruising at 25 amps or about 5.5 hours to one hour of cruising at 55 amps. To recharge a fully discharged standard pack of 16 batteries requires about 48 hours of sun.
Solar will charge the Explorer batteries at a rate equivalent to about 8 hours for one hour of cruising at 25 amps. To recharge the standard 8 batteries fully discharged requires about 76 hours of sun. About 152 hours of sun are required to recharge the optional 16-battery pack.