Our 175 Watt Rigid PV Solar Panel Tilted and Rotated on a Pole Supplied Us All the Power Needed on a Four Week Wilderness Cruise

175 Watt PV Solar Panel on a Pole

This year we again tested our CMP 175 Watt SunPower cell solar panel with our integrated water heating system on a 4 week cruise in the Canadian waters of Northern Lake Huron.  The area is known as the North Channel and is at a latitude of about 46 degrees. The 175 watt panel provided the power necessary to meet our 70 amp hour per day requirements.  Our CMP pole mounting system enabled me to tilt and rotate the panel to achieve optimum sun angle.  I set the sun angle once and rotated the panel three times a day (morning, midday, evening) and estimate we got about 30% more performance over a fixed horizontally mounted panel.  When more power was needed to bring up the batteries, I would tilt the panel to capture the maximum possible sunlight.  We used an EP Xtra-N 20 amp MPPT Controller (same as last year) to manage the solar charging and to capture solar system performance data.  

Operating statistics:

Our power usage averaged approximately 70 amp hours or 850 watt hours in a 24 hour period. Our appliances at anchor included a laptop computer several hours a day, refrigerator/freezer running 24/7, cell phone chargers, our LED lights in the evening, and our radios and instruments during the day.  We have a 75 amp Balmar alternator with a smart regulator.  We are using two 100 amp hour CMP LiFePo4 batteries for our house bank and one for our starting battery.  This is the second year for the CMP LeFePO4 batteries and they again performed beyond our expectations.

Results and findings:

1. Even running the ice maker late in the day, our LiFePO4 battery bank was fully charged by 2 PM most sunny or mostly sunny days when at anchor; about the same as last year.
2. The EP Xtra-N MPPT controller with the remote display proved to be an excellent piece of equipment.  On occasion we disconnected the remote meter and plugged in the BLE Bluetooth dongle to monitor the solar system from our phones and tablets.  Both monitoring techniques worked well however the meter captured more cumulative data such as watt hours produced so I used it more.  It was interesting to watch the solar system pouring in as much power as available to recharge the LeFePO4 battery bank then pull back in the afternoon when the batteries reached full charge.  There is no need for a float charge phase with these batteries.
3.  Rotating the panel during the day to achieve optimum sun angle, especially in the morning, significantly increased the power generation of the panel.  When we would leave the boat for extended periods for exploring and kayaking I would tilt the panel to the near horizontal position.
5. The data gathered confirmed that this panel configuration supplied all the power we needed on sunny days and had sufficient capacity to catch up on battery charge after a string of cloudy days; although sometimes it took a day or two to fully catch up.
6. The panel was affected by shading as would be expected.  Occasionally the panel was shaded by the back stay or the mast.  While the shading was minimal, it degraded the performance by up to 40%.  Panel performance degraded by over 70% on heavily cloudy days.
7. The heat exchanger on the back of the panel for our water heating system  worked well on sunny days so we had warm water for showers and dish washing.  Power consumption of this system was minimal.

Data:

This year - 2019

175 Watt Solar Panel                    At anchor   Motor         Sunny to         Cloudy to
                                                                                        Mostly Sunny  Mostly Cloudy

Average watt hrs per day                     766        495              930                 423
Average amp hours per day                     59          38                72                   32
​Maximum watt output in 24 hours    1,130        810           1,130                 810
Maximum amp hours in 24 hours             87          62                 87                   62

Last year - 2018
 175 Watt Solar Panel                    At anchor   Motor         Sunny to         Cloudy to
                                                                                        Mostly Sunny  Mostly Cloudy

Average watt hrs per day                    750        480              900                  435
Average amp hours per day                     58          37                69                   33
​Maximum watt output in 24 hours   1,280        750           1,280                 570
Maximum amp hours in 24 hours            98          58                 98                   44
​
Observations:
1. The minimum watt hour output doesn't mean much because it is dependent on both the cloud cover and the state of charge of the bank as a result of alternator charging,
2. The maximum watt hours per day of 1,280 is not the maximum output capacity of the system in a 24 hour period because the batteries were charged by 2 PM so the controller shut down the charge from the panel.  A higher drain on the house battery bank would have resulted in this number being higher.
3. Average amp hours per day is computed by dividing the watt hours by 13 volts.  This is a ballpark calculation.
4.  We did not use shore power to charge the battery bank for the entire cruise.

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