Control Systems & PLC's

Panel Amp

Installing a Solar Panel On Your Boat

After a recent five-day cruise on board our boat where we had to frequently start up the genset to provide electricity to the 115 volt ac freezer to maintain temperatures, I began to contemplate some other options.  We put more than ninety  hours on the boat genset in only five days; time for another oil change!  I put in an inverter soon thereafter and that enhanced the run time for the generator appreciably, but there was more work to be done.  I still needed to keep the batteries charged to operate the inverter.  Then it dawned on me, why not look at solar panels for use on our trawler.  Solar panels have been effectively used ever since the mid 1950s, initially used in manned space exploration. They have been falling in cost since approximately 2004 when their popularity increased significantly.  And now with the Ecological movement taking place, solar panels are as accepted as ever.  So I set out to research them and decide how to buy and mount one; I was in for a big surprise.  You can find countless retail suppliers on the web that will sell you a solar panel but nowhere could I find a comprehensive explanation of how to decide what to buy and how to mount it; much less on board a boat.  So this piece was written as I made my way all through the progression; therefore is a truly a learn-as-you-go commentary.

What is a Solar Panel and How Do They Function?

Solar panels are in theory any panel that utilizes the sun's thermal power to create electrical energy. A solar panel can be described as a photovoltaic panel, the word used in the industry, for panels designed to make electrical energy from the rays of the sun. In spite of the group of solar panel being discussed, virtually all solar panels are flat. It's because the face of the panel must be at a 90 degree angle from the sun's rays for the best angle to soak up the sun's rays.  Solar panels are able to soak up power from the sun through a collection of solar cells on their surface. Very similar to how a plant can take in energy from the sun for photosynthesis, solar cells function in a similar way. As the sun's rays hit the solar cells on a photovoltaic panel, the power is moved to a silicon semiconductor. The energy is then changed into (dc) direct current electricity and then run through linking wires to ultimately enter a storage battery.

Varieties of Solar Panels

Types of panels most often used in yachting functions contain either multicrystalline or amorphous thin-film cells. Multicrystalline panels are the oldest technology accessible and in addition the most effective. When sized appropriately and paired with appropriate batteries, these are the panels to make use of for operating great loads such as refrigeration.
Amorphous thin film solar panels are only about fifty percent as effective as multicrystalline panels, but can be bought in supple varieties so they can roll or fold, or change to the shape of a yacht cabin top or bimini.  They don't often have sufficient production for considerable energy replacement, but can be used to trickle power a battery bank.

Just How Much Energy Do Solar Cells Make?

Normally, we measure solar panels by wattage and that is how we purchase them.  You can purchase solar panels for vessels as little as 10 watts to as large as 200 watts or even larger.  But it is easier to understand when we switch watts to amperage.
We calculate these numbers by multiplying the amount of hours the panel spends in complete sun (usually defined as 5 per day in Florida) times the panel's wattage.  For a 195 watt solar panel the output would be 195 x 5 hrs = 975 watts/day.  We can then figure, 975 watts/12 volts = 81.25 amps per day.

Power Consumption

Before you consider what size panel to purchase for your boat, you will need to compute an energy analysis to ascertain what sources of energy utilization you have aboard while on the hook.  I utilize the at anchor situation because this is the place you will utilize the most energy; under power and your vessel will supply its requirements exclusive of any issues. Example, if you have 3 interior lights that draw 2 amps each and you keep them on for four hours each night, your consumption would be 3 x 2 x 4 = 24 AH/Day.  We are not concerned by running lights and electronics as they will not likely be running while on the hook.

DC Loads - calculate the amp hours used by each appliance.
    
House Lighting
Anchor lights
Refrigeration
Freezer
Electric Toilet
Fresh Water Pump
Sanitation System
Stereo
Other
                                           

Inverter Loads - calculate the amp hours utilized by each appliance below.  Inverter loads also make use of DC energy but they are running AC equipment and appliances.  If you need to convert watts to amps use (12watts/12 volts = 1amp).

    
Computer
Microwave
Refrigeration
Freezer
Heater
Hair Dryer
Television
Other

Determine your entire daily energy consumption AH/per day

Solar Energy Creation

Different sources of power like solar panels can restore the amp/hrs pulled from the batteries.  But like the energy budget that determined your usage you will also need to compute your re-supply of amp hours.  Remember the formulation - (12 watts/12 volts = 1 amp). But keep in mind, the formula is only an estimate; absolute precision can only be where the panel production is continuous and a solar panel may at times work inefficiently due to cloudy skies.  Compare the day by day energy consumption in AH/Day to the Solar Power creation.  Your solar energy creation must be larger than the use.  If it is not, select a larger wattage panel and recalculate.  Always purchase more solar panel output than you think you will need; some planners advocate at the least 30% in excess.  Example - 100 watt solar panel/ 12 volts = 8.3 amp x 5 hours = 41.66 AH/Day production

Installing Your Solar Panel

Now that you bought your solar panel, where do you install it on board your trawler?  As I mentioned before, installing the panel 90 degrees toward the sun is optimum.  You will get the best power production this method.  But on boats, finding a fitting place is difficult  at best.  A number of boaters place them on brackets located on the rails, others put them on top of the bimini, and I have observed them positioned on the boat dinghy stanchions.  But wherever you decide to mount them, bear in mind that to get the best output out of them they need to be in the open, away from any shading from booms, boat radar arches, or cabin structures.  Remember that at anchor, the trawler will veer toward the sun twice daily because of the tides.  I decided to install our panel on the top of the trawler back deck hardtop in a horizontal position.  Here it will have the greatest view of the sun and be clear from the radar arch shade as the vessel turns while at anchor.  The slope in the direction of the sun is not exactly at 90 degrees but it will have to suffice.  I selected  a 195 watt panel so I get nearly a 50% reserve capacity in my panel to make up for the small deficiency of the sun's angle.  I purchased the panel from Sun Electronics in Miami, sunelec.com since they had the best pricing I could locate anywhere online.  But keep in mind, panels need to be shipped via freight as they are solidly packed to lessen the likelihood of breakage so be sure to compute those costs in your purchase.

What Exactly is the Right Technique to Fasten the Panel to your Boat?
 
There are numerous suppliers of solar panel mounting rails and supports but almost each and every one of them are made for roof or ground mounting.  West Marine does stock a product for mounting small panels to the rails.  Many boaters build their own mounts.
I located a mount developed by Sunsei known as a Sunsei Glue Mounting Kit that is attached to the yacht and panel using 3M 5200 Marine Adhesive.  The mount makes it possible for the panel to be placed with approximately two inches of space beneath the panel for ventilation.  I did not have to drill any holes in the hardtop either.  You can get these mounts at amazon.com.

Wiring Your Panel

Marine electrical wiring is extremely technical and dangerous; if you are not at ease in doing this element of the job, please seek advice from an experienced marine electrician.  Your panel will be prewired for securing to your boat but you will need to provide the connecting cables that will also be sold by your panel supplier; they are referred to as MC4 cables.  The cables will come in different lengths suitable for your needs with a male and female connector attached; you cut one connector off.  In addition, you will also need a controller.  The controller regulates the electrical stream from the panel to your batteries keeping your batteries charged yet preventing over charging.  Some controllers are uncomplicated but others have LED displays indicating the amount of charge etc.  The more fancy features the more costly it will be.  Your panel provider will be able to suggest a controller that will satisfy your requirements.  I selected  a controller developed by Specialty Concepts.  It is easy but does the job.  And the people at the business are a huge help in assisting you to select the best model for your panel.  When you get in touch with them, they will need to understand which size panel (wattage) you have and what the voltage is.  Check them out at specialtyconcepts.com.  I also got my controller from the individuals at Sun Electronics in Miami.

The associates at Specialty Concepts have also determined how heat will influence current flow and advocate that their controllers not be positioned in engine rooms because the heat produced will diminish the controller efficiency by approximately 25%.  I located mine in the electrical panel beneath the lower helm.  And lastly, you will need the correctly sized cables to go from the controller to your batteries and a fuse to connect the controller to the battery bank.  In selecting the right fuse, you need to locate the short circuit current for your panel and select the breaker at 125% of that figure.  This will provide you the amperage of the breaker you will require.  Your controller operating manual will have guidance on these as well.

Owning a solar panel to preserve your batteries looks like a good idea but you'll need to have a way to check your batteries.  I decided to also install a Trimetric 2025RV Battery Monitor; bogartengineering.com .This smart device is wired into your battery bank to provide a real time measurement of voltage going in to the bank, amps being used by your trawler, the percent full charge on the bank, and the amp hours utilized since the last charge.

Panel Functionality

So we have now put in a 195 watt solar panel along with an 1800 watt inverter and a battery bank with 443 amp hours.  I ran our tests this week at anchor with clear skies and I concluded that our power use is 112.5 amp hours per day.  The freezer alone is the major pull using 60 of the amp hours followed by the refrigerator.  Did you know that a standard anchor light uses 18 amp hours each night?  I think I'll check out LED bulbs now.  The battery monitor told me that our actual draw from the battery bank was only 65 amp hours which means we received the remainder from the sunlight, an entire 42% was from the sun.  Now we will operate the genset for roughly one hour to bring the battery bank up to full charge.

About the Author

Mike Dickens, the author, is a boat owner and owner/Broker of Paradise Yachts. Paradise Yachts is a Yacht Brokerage offering used yachts to customers worldwide. Visit our website to view our selection of Used Trawlers, Used Motor Yachts, and Used Sailboats .

Interact with us at our Paradise Yachts Blog

National and international sales. We ship Used Yachts and Used Boats worldwide. Located in Florida, USA. 904/556-9431

How to calculate amp-hr from the solar panel?

The current measure from the solar panel is 0.05A.

"amp-hour" has no meaning for a solar panel. It's used for batteries only.

The current is 0.05 amp as you noted. There is also a voltage and power specification.

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Electrical Panel Replacement Part 2