Comparing Our New 160 Watt Solar Panel with Our 130 and 140 Watt Panels

140 Watt Poly-crystalline Solar Panel

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.  In an August 2012 blog entry I documented the performance of our 140 watt poly-crystalline solar panel.  This year I documented the performance of our 160 watt mono-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).  The number of days of each cruise varied so I an presenting average performance based on four weather conditions; sunny, mostly sunny, mostly cloudy and cloudy.


Test conditions:

• The boat has two deep cycle wet cell battery banks; 315 amp hours and 105 amp hours.
• The boat has holding plate refrigeration which draws 5 amps.  The weather was generally cooler than previous years so the frig compressor ran less than usual; 6+ hours a day.  The lap top computer was used for navigation and draws 3 amps.  All lights are LEDs.
• When motoring, the panel was usually connected to the controller.
• The dual battery bank solar panel controller shuts off power from the panel when the batteries are fully charged.  i.e. After 3 or more hours of motoring.
• The Remote Display of the dual battery bank controller was used to collect all the data.
• Our mode of cruising was to anchor for 2-4 days at a time and move on to another anchorage.  We did not dock and use shore power during the cruise.
• The tilt angle of the panel was rarely changed. I was usually set at about 45 degrees.  The panel was rotated for optimum sun angle on an average of 3 times per day.
• When the battery banks are fully charged the dual output controller will shut off the panel charge to the batteries.  This is reflected in the performance of the panels.  This year our battery banks were at full charge more often than the previous two years because there was less draw from the refrigeration system due to the cooler weather.  I believe this is reflected in the performance of the 160 watt panel.

Test Results:

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    160 Watt, mono

Overall average output per day         54 amp hours    53 amp hours       48 amp hours
Note: 160W had only 5 sunny days, 140W had 10 sunny days and 130W had 8 sunny days

Sunny days                                    71                          69                       71
Mostly sunny days                          51                          50                       50
Mostly cloudy days                         46                          35                       37
Cloudy days                                   24                          32                        28
                    
Avg. Output on days at anchor         62                          62                        61
Avg. Output when engine was used  35                          43                        44 
 (difference partially because 130W was often disconnected often when engine was used. Not so for 140W and 160W)

 Min amp hrs for a day                    16                          27                        28

Max amps output                           10.5 amps           10.5 amps            11.5 amps

Interpreting the Results:

Each solar panel performed about as expected.  The average daily output was less for the 160 watt panel but it had half as many sunny days and comparable mostly sunny days.  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. The max output of the 160 watt panel was an amp higher that the others. 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, 140 and 160 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.

Observations:

All three solar panels 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 needed to use 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, each solar panel will perform adequately under most  conditions.  The  130 watt and 160 watt mono-crystalline solar panels are 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.

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