Our 120 watt rigid marine solar panel with premium SunPower cells has been so popular we have expanded our product offering to include 100 and 160 watt rigid marine solar panels with premium SunPower cells.  These high performers are well suited for top-of-pole mounting or frame mounting on a bimini or on dinghy davits.  This line of marine solar panels is made to our specification and offer the highest output per square inch in the industry.

I have installed our radiant water heating heat exchanger to the back of a 160 watt SunPower panel and will be testing and reporting on performance after our cruise in the North Channel of Lake Huron later this summer.  This promises to be our best top-of-pole system yet.  See my earlier blog reporting on the 120 watt SunPower cell panel from last year's cruise.

I recently ran across this article from the Department of Energy about solar panel performance.  It identifies the three key factors related to panel performance; heat, dirt and shading.
​Link to article:   Getting the Most Out of Solar Panels

This year we tested our new 120 Watt SunPower cell solar panel with our integrated water heating system on a 5 week cruise in Northern Lake Huron at a latitude of about 46 degrees.  We used an EP 20 amp MPPT Controller.  A 10 amp controller would have been sufficient but we wanted extra capacity so we could plug in an auxiliary 100 watt semi-flexible panel as a backup if we needed additional power because of a series of cloudy days. Plugging in an extra panel is simple using the MC4 connectors and an MC4 T-branch connector. We had mostly sunny days so we didn't need additional power beyond what the 120 watt panel provided.  The weather was awesome!  The 120 watt panel was mounted using our CMP pole mounting system so I could 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 figure I got about 30% more performance over a fixed horizontally mounted panel.

Operating statistics:

Our power usage averaged approximately 70 amp hours or 850 watt hours in a 24 hour period.  Our current draw was from a refrigerator/freezer running 24/7, our LED lights in the evening, cell phone chargers, laptop computer several hours a day and our radios and instruments during the day.  Our windlass is only run when the engine is running so we don't include it in our power consumption calculation as the alternator quickly makes up for its power usage.  We have a 75 amp Balmar alternator with a smart regulator.  Our house bank consists of 3 flooded cell batteries giving us a total capacity of 330 amp hours.  We started the engine to move anchorages about every three days.

Results and findings:

1. Our battery bank was fully charged by 2 PM most sunny or mostly sunny days when at anchor.  This is in contrast to 12-1 PM in past years using our 150 or 160 watt panels on poles.
2. The EP Tracer BN MPPT controller with the remote display proved to be an outstanding piece of equipment.  It was simple to program, easy to read, collected the appropriate data and was very efficient.  It was exciting (I get excited about these things) to see 8+ amps being poured into the battery bank in the morning.  It would be frustrating to see it only outputting and amp or two in the afternoon in full sun but then you realize it is doing its job.  It fully charged the batteries in the morning and was in float mode topping off the battery bank in the afternoon.
3. Rotating the panel during the day, especially in the morning, significantly increased the power generation of the panel.
4. Our weather was so sunny and the panel performed so well we had no reason to plug in the auxiliary 100 watt flexible panel using an MC4 T-branch for extra charging power.  I plugged it in one morning just to confirm the configuration would work and was easy to do.  It worked well and brought the charging amps to well over 12 amps.
5. The data gathered confirmed that this panel configuration supplied all the power we needed and has excess capacity to catch up on battery charge from a string of cloudy days.
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%.

Data:
                                                  At anchor   Motor         Sunny to         Cloudy to
                                                                                 Mostly Sunny  Mostly Cloudy

Average watt hrs per day                  740        540             650                 290
Average amp hours per day                 57          45               50                   22
​Maximum watt output in 24 hours    960        630             960                 540
Minimum watt output in 24 hours        200         200             420                 170

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 960 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. This configuration proved to have plenty of capacity for our cruising needs even without using the auxiliary solar panel.  We have not used shore power to charge our battery bank for the entire summer.

Solar Water Heater:

We installed our new solar water heating system.  It consists of a heat collector or heat exchanger mounted on the back of the solar panel, and a circulating pump.  See our earlier blog for design considerations.  The pump circulates water from the water heater through the heat exchanger on the panel.  We used the same configuration on our 150 watt panel last year.

Results:

On sunny days at anchor we had warm water for showers and dish washing.  The water temperature in our 8 gallon hot water tank would warm from 60 degrees to about 105 degrees in 2-3 hours on a sunny calm day.  This was slower than the system we tested last year on our larger panel but it was perfectly adequate to meet our needs.  As expected, we confirmed that strong winds tend to cool the panel and reduce the heating efficiency as do clouds.  Overall, the water heating system cools the surface of the panel by at least 20 degrees.  This increases the efficiency of the panel since solar panel performance degrades as they are heated by the sun. Insulating the tubing running between the heat exchanger and the water heater significantly increased the efficiency of the system.  In conclusion, the radiant energy water heating system works well on sunny days with both our larger and our standard sized panels. See our product section or read our earlier blog for details.

We have been testing our 150 and 160 watt solar panels for the past few years on extended cruises.  While at anchor, on a sunny day, our battery banks are usually topped off by about 1 PM.  We run our refrigerator/freezer 24/7. So why not use a smaller 100 or 120 watt  solar panel and plug in a flexible panel on the rare occasion we need more charging power?  This is what we will be testing while cruising this summer.  It's a simple arrangement.  We will carry a 100 watt flexible solar panel under a bunk cushion.  If we need extra charging power we will simply plug it in using a T-branch connector at our pole mounted 120 watt panel and secure the flexible panel to the bimini top.  That gives us 220 watts of power through our 20 amp MPPT controller.  Several of our customers have reported using this configuration and are very satisfied with it.  I'll report our results at the end of the season.  Now, gotta go sailing and start testing.

We have all heard about tax credits for putting solar on our home but what about for our boat?  Sure, why not?
The US Federal Government offers a solar energy tax credit, applicable to your second home.  If you have a head and galley onboard and your boat is docked in the United States, your boat qualifies as a second home. This tax credit,extended to December 31, 2019, is a 30% credit on qualified expenditures to purchase and install solar panels placed in service after 2008. This credit can be retroactive – as long as the solar system was placed into service after January 1, 2006.
​
The Department of Energy website gives a simplified description of the energy tax credit: http://energy.gov/savings/residential-renewable-energy-tax-credit. The actual IRS form is easy to fill out: http://www.irs.gov/pub/irs-pdf/f5695.pdf. It may also worth investigating your state government solar tax credit. 

We are often asked questions about how to wire a solar system.  This can appear to be a daunting task for those new to the world of solar but it is actually quite easy and straight forward.  In this blog I will walk you through the wiring process for our dual output controller step by step.

First, the definition of a few terms:
​* MC4 Connector - A water proof connector used in solar wiring.  Most solar panels come with MC4 connectors attached to 3 foot solar wire pigtail coming from the panel junction box.  These connectors are easily disconnected.
* Solar Controller - Except for small trickle charge systems, all solar systems should have a solar controller.  The purpose of a controller is to prevent batteries from being overcharged, apply the optimal charging current to the battery bank and prevent current from back flowing from the batteries to the solar panel at night.  Controllers are sized by their amperage capacity.  Controllers designed for residential and commercial (lighting) use are generally overkill and not well suited for marine applications.
* Temperature Sensor - This device is connected to the controller and senses the temperature of the battery bank.  If the batteries are heating up due to heavy charging, the sensor signals the controller and the controller reduces the charge current appropriately. A temperature sensor is only useful for systems with larger solar arrays as smaller solar systems do not provide sufficient power to over heat the batteries.
* Solar Wire - While most any wire can be used in a solar system, solar wire is designed for maximum conductivity and is well insulated with a UV resistant cover.  It is typically single conductor and the insulation is .25 Inches in diameter.

The wiring diagram below is taken from our dual output controller manual and illustrates the basic wiring required for a two panel system, a dual output controller and two battery banks.  Most solar controllers are single output so charge only one battery bank. In this case, it is common to wire the positive wire to the common on the battery 1-2-both battery switch to select which battery bank is to be charged.






​
A few things to note in the diagram:
* The two solar panels are wired in parallel using an MC4 T-branch connector,  If one panel is shaded, the other panel will still provide full power to the controller.
* There is a switch in the positive wire between the solar panel and the controller.  This is optional.  The purpose of the switch is to turn off the panel should it interfere with the alternator output when the auxiliary engine is generator is running. It has been reported that some smart regulators are confused by the power coming from the solar panel.  It sees the sum of the battery charge plus the panel output and senses the batteries are fully charged so goes into float mode prematurely.  This is easily remedied by flipping the switch thus disconnecting the solar panel.
* The optional temperature sensor is shown to the left of the larger house battery bank.  It is simply taped on to the top of the battery.
* If you have a battery monitor such as a Link or Xantrex 1000 or 2000, it is important to connect the  negative wires from the controller to the shunt of the battery monitor.  Otherwise, the monitor doesn't see the power coming in from the solar panel and will give inaccurate readings.
* There is a sequence to follow in connecting the solar system.  Connect the controller to the battery banks first.  Then connect the solar panel to the controller.
​

In an earlier blog post I described how a solar panel can be used to heat water using the sun's radiant energy (not the electricity generated by the solar panel).  This year we put the concept of heating water by collecting the sun's radiant energy coming through the back of the solar panel to work during our 35 day cruise.  I mounted a custom made heat exchanger to the back of our 150 watt solar panel, added some insulation and a new back panel.  Water is circulated from the boat water heater through the heat exchanger and back into the water heater using a small circulation pump that draws less than .4 amp.  

Here is what we found during our 35 day cruise in northern Lake Huron:
1.  Running the circulation pump for several hours midday on sunny days provided us warm water for showers and dish washing within two hours.
2.  Water was heated from 60 degrees F to about 110 degrees F on sunny days.
3. Water was heated faster and to a higher temperature on calm days than on windy days.  This is because the wind tends to cool off the front face of the solar panel.
4. We enjoyed warm water from the solar panel water heating system 12 days at anchor.  Other days we either had warm water from running the engine to move the boat or the days were cloudy so no heat was collected.
5. The small circulation pump did not draw a significant amount of solar power.  Besides, our batteries were topped off by early afternoon so we had plenty of excess power.
6. Having the system tapped into our boat's water system made it very convenient to take advantage of the warm water.
7. The added weight (10 pounds) of the water heating system was no problem for the pole brackets or stern rail.
8. I added a T and a valve in the solar heater tubing to make warm water available in the cockpit for showering or rinsing off after a swim.  It worked perfectly.

All in all, the system worked as planned and provided us with warm water conveniently when we needed it.  Our next step will be to make a kit available to our customers to retro fit their solar panel systems or to order a water heating system with new installations.  We will have kits available for both our larger 150-160 watt panels and our smaller 100-105 panels.

We tested our new 150 watt polycrystalline solar panel on a 35 day cruise in the North Channel area of Northern Lake Huron.  This panel was equipped with the prototype of our solar water heating system which will be addressed in another blog entry. The solar panel was mounted on our pole mounting system and was rotated toward the sun The boat equipment and cruising pattern was essentially the same as last year (See prior blog entries).  We were powering a freezer/refrigeration system, instruments, laptop computer, radios, autopilot, windlass and LED lights. Data was gathered using the remote display on our EP 10 amp dual output solar controller.  The solar panel performance met our expectations.  Our house battery bank consists of three 120 amp hour flooded batteries.  
Both battery banks were usually fully charged by 2 PM when at anchor and on mostly sunny days so we often had excess power. 

Data comparing the performance of the 150 watt solar panel with our 140 and 160 watt panels is presented below.

Average amp hours per day produced under various conditions:

                                                       150 Watt poly  140 Watt, poly    160 Watt, mono    160 Watt, mono
                                                                2015             2012                   2013                    2014

Overall average output per day         49 amp hours    53 amp hours       48 amp hours          48 amp hours

Sunny days                                                 60                 69                        71                        69
Mostly sunny days                                       56                 50                       50                         56 
Mostly cloudy days                                      36                 35                        37                        39
Cloudy days                                                22                 32                        28                        20
                    
Avg. Output on days at anchor                     60                  62                        61                       51
Avg. Output when engine was used              42                  43                        44                       45
 
 Min amp hrs for a day                                 4                   27                        28                        4
 Max amp hrs for a day                               84                   74                        77                      76

Max amps output                                      11.8 amps      10.5 amps            11.5 amps           11.4 amps

This data is intended to provide a general idea of what to expect from the 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 off power from the panels).   Because the panel was equipped with a water heat collector on the back, it may have run hotter on sunny days when the water circulation pump wasn't run thus degrading the performance by up to 10%.The average panel output on sunny days at anchor with no motoring was 67 amp hours.

Several of our customers have recently attached their semi-flexible solar panels using nuts and bolts.  
Here is what they did:
1. Place the solar panel on the canvas and mark the grommet holes on the canvas.
2. Glue a vinyl disk about 2 inches in diameter to the underside of the canvas at points where attaching bolts will be placed.
3. Puncture a hole in the fabric through the vinyl.
4. Place a 1 inch diameter or greater plastic or stainless fender washer on a 10-24 or similar stainless bolt and pass it through the canvas.
5. Place another fender washer on the bolt on top of the canvas and secure with a nut.
At this point, you have a reinforced canvas sandwiched between two fender washers.
6. Pass the bolt through the solar panel grommet and secure with an acorn nut.
7. Repeat for each solar panel grommet.
See diagram below for details.


On the installation shown above, the solar wires were run through the channel used to attach the canvas to the frame thus hiding most of the wiring.

The excellent performance of our semi-flexible solar panels is opening up new ways to easily implement solar systems on cruising boats. There are several ways to attach our flexible solar panels to a canvas bimini top.  Here are some creative ideas our customers have implemented:
1. Zipper solar panels directly to the bimini canvas - Stitch zippers along the sides of the solar panel using an industrial sewing machine.  Stitch the mating zipper onto the bimini top with a flap to cover the zipper to protect it from UV rays.  Zip the panel onto the bimini and run the wires as necessary.  See picture to the right.

2. Attach solar panels to canvas and zipper canvas to the bimini canvas - Panels can be attached to a piece of canvas using zippers, snaps or grommets.  Sleeves can be sewn into canvas to hide and protect the wires.  The canvas with the solar panels can then be attached to the bimini canvas using zippers.
3. Attach solar panels to the bimini canvas using snaps or grommets - Our flexible solar panels come with 4 or 6 sets of grommets installed.  These grommets can be used to stitch the panels directly to the bimini canvas.  Alternatively, these grommets can be drilled out and replaced with snaps.  The mating snaps can be installed in the bimini canvas so the panels can be simply be snapped into place.
4. Attach solar panels to the bimini canvas using outdoor Velcro (hook and loop) - Stitch or glue the Velcro to the back of the panel and stitch the mating Velcro to the bimini canvas.  Panels can be easily removed for storage.

Note: Because the PV cells of the panels are black, they will absorb and radiate considerable heat.  Some customers have inserted insulation between the panel and the canvas to reduce the radiated heat.  They have used the bubble wrap encased in silver foil insulation available at most home improvement stores.  It is about 5/16" thick.

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.

Our top-of-pole solar system addresses the need for power while at anchor and under sail.  In fact, we have found the solar system usually provides us an excess of electrical power while cruising.  Now we find the only additional thing we need while at anchor for an extended period is warm water for showers and cleaning dishes.  Sure there is the old black bag absorb the sun's heat option but this is a bit cumbersome.  
Then there is the option to run the engine until it heats up the water in the water heater.  Running the engine for warm water is inefficient and undesirable. 


Now we have what promises to be a pretty good solution; solar heated water.  Because the solar panel is dark in color, it absorbs a significant amount of the sun's energy in the form of heat.  This is dissipated through the back and front of the panel by air currents.  By attaching a heat collector/exchanger to the back of the panel, properly insulating it and circulating water through the heat exchanger we are able to collect that excess heat and store it in the water heater tank or in a separate holding tank.  While still in the test stages, we have completed proof of concept and can make the heat exchangers available to DIY mariners who are interested in setting up such a system.  We plan on offering a complete water heating system retro fit kit within the next year. 

Initial tests indicate that with our 140 and 160 watt systems we can heat 3 gallons of water from 60 to 110 degrees F in less that a half hour on a sunny day with the ambient temperature of 65 degrees F.

Our top-of-pole system is about to be a 3 in 1 assembly; solar panel mount, outboard motor crane and solar water heating system.  Call us if you are interested in participating in our test program.

When our supplier told me they had a new high output marine solar panel that was flexible I was skeptical.  The specifications seemed just to good to be true.  So I ordered some to test.  Well, I was pleasantly surprised.

These panels are very well constructed and they have a power generation comparable to our hard panels.  These panels can be flexed to 30 degrees so can conform to most boat curved surfaces.  The 100+ watt panels have an electrical box on the front (not shown in the picture) which contains two blocking diodes.  The 50 watt panel has one blocking diode.  The base material is very sturdy and strong.  Each panel has grommets for attaching the panel.  

I have tested the output of these panels under various weather conditions and their susceptibility to shading.  Below is a quick comparison of output of our three mid-range panels laying flat at mid day on a mostly sunny day measured with a meter:

                                                      Flexible 100 watt         Rigid 105 watt          Rigid 100 watt
                                                      Monocrystalline           Monocrystalline        Polycrystalline

Short Circuit Current (Isc)                      5.48 amps                   5.50 amps                5.26 amps
Open Circuit Voltage (Voc)                    19.2 volts                    19.7 volts                  20.5 volts
Computed Power (not rated power)         105 watts                    108 watts                 108 watts

Additional information is available on our solar panel page.

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.

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.  

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 very warm so the frig compressor ran more than usual; 8+ 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 bank 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 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; usually about 45 degrees.  The panel was rotated for optimum sun angle on an average of 3 times per day.

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

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.

Observations:

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.

I mounted our new 140 watt polycrystalline solar panel and tracked its performance for four days in northern Lake Huron, Michigan.  Fortunately, I experienced different weather conditions each day so there is some data to compare the 140 watt panel to the 130 watt monocrystalline panel.  The panel was tilted at a 30 degree angle and rotated three times during the day; morning, noon and late afternoon.  The panel was partially shaded by the back stay during the late morning.  This seemed to degrade panel performance by about 1 amp. When pointed toward the sun during a clear sky period, the panel produced between 8 and 9.6 amps, considerably higher than its rated output.  The controller recorded a max output of 10.6 amps.  This is very impressive and shows the Class A silicone wafers are clearly worth the added cost over Class B wafers.  Power consumption was from refrigerator/freezer, computer, lights (LEDs) and radio.  The house battery bank was negative 28 amp hours after four days.  Had the sunny day been the last day, the battery bank would have been fully charged.   Below is the data:
          Amp Hours    Weather
Day 1     80 AH       Sunny all day
Day 2     62 AH       Hazy, partly cloudy all day
Day 3     31 AH       Cloudy, overcast, rain until 5 PM
Day 4     56 AH       Hazy, partly cloudy, no clear sky all day

Preliminary conclusions:
The 140 watt polycrystalline panel performance is comparable to our 130 watt monocrystalline panel.
The panel performed above its rated output by 1-2 amps.
Performance during cloudy and hazy periods was very good.
The 140 watt panel appeared to have less sensitive to shading than the 130 watt panel.

Relative solar panel size:  the 140 watt panel is smaller than the 130 watt panel by only 3 square inches.
The performance of our 130 watt solar panel is documented in an earlier blog entry below.

I will publish additional data as it becomes available.