Performance Comparison of a 130 Watt Mono-crystalline and a 140 Watt Poly-crystalline Solar Panel in a Cruising Application
In an earlier blog entry dated 8/10/2011 I documented the performance of our 130 watt mono-crystalline solar panel on a 22 day cruise in the upper Great Lakes. This year I documented the performance of our 140 watt poly-crystalline solar panel on the same boat under similar conditions. The only variables were the weather and the running of the engine when moving from anchorage to anchorage (wind was on our nose quite often this summer). Also this panel performance was documented over a longer period of 34 days.
Definition: amp hour – amps produced or consumed in one hour
Average amp hours per day produced under various conditions:
130 Watt, mono 140 Watt, poly
Overall average output per day 54 amp hours 53 amp hours
Sunny days 71 69
Mostly sunny days 51 50
Mostly cloudy days 46 35
Cloudy days 24 32
Output on days at anchor 62 62
Output when engine was used 35 43 (difference because 130W was disconnected often
when engine was used. Not so this year for 140W)
Min amp hrs for a day 16 27
Max amps output 10.5 amps 10.5 amps
Interpreting the Results:
Both solar panels performed as expected. Their average daily output was about equal. The 130 Watt mono panel provided a slightly higher average output on sunny days and the 140 Watt poly panel provided a higher average output on cloudy days. My sense was that the poly-crystalline panel was less sensitive to shading from the rigging but this is difficult to document. On sunny days, both solar panels often performed above their sticker rating of 130 and 140 watts by as much as 50 watts (9.5 amps at 21 volts is 189 watts) . I believe this is due to the high quality of silicone crystals used.
Both the 130 watt solar panel and the 140 watt solar panel generally met our power needs for the duration of the cruises. We occasionally ran a small deficit of amp hours during an extended anchorage when cloudy 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 solar panel.
Choosing the right type of solar panel:
Based on the performance data, both solar panels will perform adequately under most conditions. The 130 watt mono-crystalline solar panel is an excellent choice for boats in mostly sunny areas with little possibility of shading from the rigging. The 140 watt poly-crystalline solar panel is an excellent choice for areas with more partly cloudy and cloudy days and on boats where there is some shading from the rigging.
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.