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.