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.
The following is the result of testing the CMP130 watt monocrystalline solar panel with the top-of-pole mount and dual output controller cruising for 3 weeks in the North Channel of northern Lake Huron. The panel mounting system is shown on our Gallery of Installations; the Ericson 38. (Well, somebody has to do it. :-) )
Date Amp Conditions of the day
7-7 46 At dock, shore power on
7-8 39 Motored 4 hours, partly cloudy
7-9 17 Motored all day, cloudy tried solenoid
7-10 26 Cloudy, motored 1 hour, sun 5-6 hours
7-11 55 Mostly sunny, travel day – under sail
7-12 64 Mostly sunny, at anchor
7-13 79 Mostly sunny, at anchor, reset meter when rewired batteries
7-14 70 Mostly sunny, at anchor, panel not turned for part of the day
7-15 49 Cloudy morning, sunny afternoon, motored for 2 hours with solenoid on
7-16 51 Mostly sunny, motored 2 hours with solenoid on, topped off batteries
7-17 34 Mostly cloudy, at anchor all day
7-18 47 Mostly cloudy, motored 2 hours
7-19 20 Hazy, cloudy, motored 2 hours
7-20 71 Sunny, at anchor
7-21 80 Sunny, at anchor
7-22 67 Mostly sunny, ran engine 1.5 hrs, topped off batteries
7-23 39 Mostly cloudy, at anchor
7-24 73 Mostly sunny, at anchor
7-25 68 Mostly sunny, at anchor
7-26 16 Hazy, cloudy, motored 4 hours, topped off batteries
7-27 26 Cloudy, hazy, motored 9 hours, batteries charged
7-28 42 Mostly sunny, motored 2 hours with panel connected, batteries charged
Definition: amp hour – amps produced or consumed in one hour
Average amp hours per day produced under various conditions:
Overall (22 days) 54 amp hours
Sunny days at anchor 71
Cloudy days at anchor 37
All days at anchor 62
Days engine was used 35
Max amp hrs for a day 80
Min amp hrs for a day 16
Max amps output 10.5 amps
The 130 watt panel generally met our power needs for the duration of the cruise. We occasionally ran a small deficit of amp hours during an extended anchorage but never used the engine alternator to charge the battery banks except when motoring from place to place. On days when the engine was used we often had an excess of power generation from the 75 amp alternator and the 130 watt solar panel.
The solar panel is very sensitive to cloudy days and to shadows. The panel output on sunny days exceeded it rating. This is the nature of mono-crystalline solar panels.
The weather for our cruise in the North Channel of Lake Huron this year was excellent. It was warmer and sunnier than last year. Our Kyocera 85 watt solar panel performed very well. The following are some statistics:
Days cruising: 22 days
Max power generation: 40 amp-hours
Min power generation: 13 amp-hours
Average power produced per day: 35 amp-hours
Average power consumed per day: 51 amp-hours
Our primary use of power was for the refrigerator/freezer. We ran a power deficit each day of about 16 amp-hours at anchor but with our 360 amp-hour battery bank, this not a problem. Moving on every 4 days or so gave the 75 amp alternator plenty of time to bring the batteries back up to charge.
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.