This was the second year we used the 160 Watt solar panel on a 35 day cruise in the North Channel area of Northern Lake Huron. The boat equipment and cruising pattern was essentially the same as last year (See prior blog entries). The solar panel performance was comparable to last year with a few minor exceptions. The data comparing the performance of the 160 Watt panel during 2013 and 2014 and the 140 Watt panel in 2012 is displayed below.
Average amp hours per day produced under various conditions:
140 Watt, poly 160 Watt, mono 160 Watt, mono
2012 2013 2014
Overall average output per day 53 amp hours 48 amp hours 48 amp hours
Sunny days 69 71 69
Mostly sunny days 50 50 56
Mostly cloudy days 35 37 39
Cloudy days 32 28 20
Avg. Output on days at anchor 62 61 51
Avg. Output when engine was used 43 44 45
(We had more cloudy days at anchor this year)
Min amp hrs for a day 27 28 4
Max amp hrs for a day 74 77 76
Max amps output 10.5 amps 11.5 amps 11.4 amps
This data is intended to provide a general idea of what to expect from the marine solar panels under various conditions. The two primary variables are the amount of sunshine and the running of the engine (the alternator charges the batteries so the controller shuts the panels down).
The test boat was running a freezer/refrigerator drawing 5 amps running 6 hours a day, LED lighting, laptop computer drawing 4 amps running 3 hours a day, radios drawing 3 amps running 8 hours a day, and instruments and autopilot when under sail and power. When at anchor on a sunny to mostly sunny day our batteries were at full charge by 2 PM so we usually had excess power.
At other places on this blog and on our web site we talk about how to determine the size of solar panel (how many watts) you will need to meet you power consumption requirements. Once you know your panel size requirement there are some things to consider in selecting a solar panel.
Panel Type - There are many articles written on the two types of solar panels; monocrystalline and polycrystalline. Monocrystalline panels are made up of single crystal silicon wafers. Polycrystalline panels are made up of silicon that has a multiple crystalline structure. There are pros and cons to each type of panel. Monocrystalline panels have a higher output per square inch in direct sun but are very sensitive to shading and output will degrade faster on cloudy days. Polycrystalline panels are not as sensitive to being shaded and output will not degrade as much on cloudy days. At CMP we offer both a polycrystalline and a monocrystalline panel.
Panel Crystal Quality - Because we have a confined space on our boats, we need to have the maximum output per square inch from our solar panels. The quality of the silicon crystals used to make the panel is a key factor in determining the panel output. Crystals are passed under a fixed light and graded as to their output (1-10). Grades are grouped into classes. Class A crystals are grades 8-10, Class B crystals are grades 4-7 and so on. Crystal quality follows a bell curve; there are many more Class B crystals than Class A. We at CMP specify only the best Class A crystals for use in our panels. Less expensive Class B and C panels are often used on land based solar farms where space is not an issue.
Panel Shape - The largest market for solar panels is commercial applications where many many panels are mounted on a roof or in a field. These panels are usually rectangular in shape often twice as long as wide. This shape is often not ideal for marine application. Often a more square shape is preferable, especially for pole mounting.
Choosing the right panel for your needs will require study and/or discussion with panel experts.
Thomas Trimmer has been cruising with his Ericson 38 sailboat on the Great Lakes for over 20 years. He has pioneered the use of solar energy for wilderness cruising. He is continually designing and building equipment to simplify and enhance the cruising experience.