After a 5-day trip on our trawler where we continually started up the genset to provide electrical power to the 115 volt ac freezer to maintain temperatures, I began to think about alternate options. We put more than 90 hours on the vessel generator in just 5 days; time for another oil change! I put in an inverter shortly afterward and that improved the run time for the genset drastically, but there was more work to be completed. 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 board our vessel. Solar panels have been successfully utilized since the mid 1950s, initially used in manned space exploration. They have been dropping in cost since roughly 2004 when their popularity really went up. And now with the Environmentally friendly move occurring, solar panels are as accepted as ever. So I started to research them and decide how to purchase and install one; I was in for a big surprise. You can come across numerous retail suppliers over the internet that will sell you a solar panel but nowhere could I locate a comprehensive explanation of how to decide what to get and how to install it; much less on board a boat. So this commentary was born as I made my way through the progression; thus is a truly a learn-as-you-go article.

What is a Solar Panel and How Do They Work?

Solar panels are basically any panel that utilizes the sun's thermal energy to produce electrical power. A solar panel can be described as a photovoltaic panel, the name used in the industry, for panels designed to produce electrical power from the rays of the sun. In spite of the group of solar panel being mentioned, nearly all solar panels are flat. It's because the face of the panel needs to be at a 90 degree slant from the sun's rays for the most favorable angle to take in the sun's emission. Solar panels are able to take in energy from the sun through a collection of solar cells on their surface. Very similar to how a plant can absorb energy from the sun for photosynthesis, solar cells perform in a comparable 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 converted to (dc) direct current electrical energy and then passed through connecting wires to finally go into a storage battery.

Kinds of Solar Panels

Types of panels most often utilized in yachting uses contain either multicrystalline or amorphous thin-film cells. Multicrystalline panels are the oldest technology existing and also the most powerful. When sized correctly and matched to proper batteries, these are the panels to utilize 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 purchased in supple forms so they can roll or fold, or change to the shape of a vessel cabin top or bimini. They don't normally have sufficient output for considerable energy replacement, but can be utilized to lightly charge a battery bank.

How Much Power Can Solar Cells Create?

Generally, we gauge solar panels by wattage and that is how we buy them. You can get solar panels for boats as small as 10 watts to as large as 200 watts or even larger. But it is simpler to comprehend when we convert watts to amperage. Calculate these numbers by multiplying the amount of hours the panel spends in full sun (typically defined as five a day in Florida) by the panel's wattage. For a 195 watt solar panel the output would be 195 x 5 hrs = 975 watts/day. Taking it step further, 975 watts/12 volts = 81.25 amps per day.

Energy Consumption

Before you consider which size panel to buy for your vessel, you will need to put together an energy plan to ascertain what sources of energy expenditure you have on board while on the hook. I utilize the at anchor scenario as this is where you will utilize the most energy; under power and your boat will provide its needs without any issues. Example, if you have 3 inside lights that pull 2 amps apiece and you keep them on for 4 hours each night, your consumption would be 3 x 2 x 4 = 24 AH/Day. We are not concerned with running lights and electronics as they will not likely be operable while on the hook.

DC Loads: Calculate the amp hours utilized by each appliance.

House Lighting, Anchor lights, Refrigeration,

Freezer, Electric Head, Fresh Water Pump,

Sanitation System, Stereo, Other

Inverter Loads

Inverter loads also make use of DC energy but they are running AC equipment and appliances. If you want to change watts to amps use (12watts/12 volts = 1amp).

Calculate the amp hours used by each appliance below:

Computer, Microwave, Refrigeration, Freezer,

Heater, Hair Dryer, TV, Other

Calculate your overall daily energy consumption AH/per day

Solar Energy Creation

Different sources of energy like solar panels can replace the amp/hrs pulled from the batteries. But similar to the power budget that determined your usage you will also want to calculate your re-supply of amp hours. Keep in mind the formulation - (12 watts/12 volts = 1 amp). But bear in mind, the formula is only an estimate; absolute precision can only be where the panel output is continuous and a solar panel might occasionally run ineffectually because of cloudy skies. Compare the daily energy expenditure in AH/Day to the solar power production. Your solar energy creation should be larger than the use. If it is not, select a bigger wattage panel and recalculate. Always buy more solar panel output than you imagine you will need; some planners advocate at the least 30% in excess.

Illustration - 100 watt solar panel/ 12 volts = 8.3 amp x 5 hours = 41.66 AH/Day production

Mounting Your Solar Panel

Now that you own a solar panel, where do you install it on your vessel? As we mentioned already, mounting the panel ninety degrees in the direction of the sun is optimum. You will receive the best power creation this method. But on boats, finding an appropriate location is difficult at best. Some boaters place them on brackets located on the rails, others put them on top of the bimini, and I have witnessed them placed on the vessel dinghy stanchions. But wherever you decide to install them, remember that to get the best performance out of them they ought to be in the open, away from any shading from booms, vessel radar arches, or cabin structures. Bear in mind that at anchor, the vessel will turn toward the sun twice every day as a result of the tides. I decided to mount our panel on the top of the trawler back deck hardtop in a horizontal manner. At this point it will get the best view of the sun and be clear from the radar arch shading as the yacht turns while at anchor. The slope toward the sun is not precisely at ninety degrees but it will have to suffice. I picked a 195 watt panel so I have roughly a 50% reserve ability in my panel to compensate for the minor deficiency of the sun's angle. I purchased the panel from Sun Electronics in Miami, sunelec.com since they had the best prices I could come across anywhere online. But keep in mind, panels need to be shipped via freight as they are heavily packed to lessen the chance of damage so make sure to calculate those expenses in your purchase.

What Is the Best Method to Connect the Panel to your Trawler?

There are quite a few suppliers of solar panel mounting rails and supports but almost all of them are intended for roof or ground mounting. West Marine does supply a product for mounting small panels to the rails. Many boaters construct their own mounts. I located a mount developed by Sunsei called a Sunsei Glue Mounting Kit that is affixed to the vessel and panel using 3M 5200 Marine Adhesive. The mount makes it possible for the panel to be installed with roughly 2 inches of clearance beneath the panel for aeration. I did not have to drill any holes in the hardtop either. You can find these mounts at amazon.com.

Wiring Your Panel

Marine electrical wiring is very specialized and hazardous; if you are not comfortable in doing this part of the job, please check with a skilled marine electrician. Your panel will be prewired for attaching to your vessel but you will need to provide the connecting cables that will also be sold by your panel supplier; they are known as MC4 cables. The cables will come in different lengths suitable for your requirements with a male and female connector affixed; you cut one connector off. In addition, you will also require a controller. The controller regulates the power flow from the panel to your batteries keeping your batteries charged yet preventing over-charging. A number of controllers are simple but others have LED displays showing the amount of charge etc. The more whistles and bells the more costly it will be. Your panel dealer can suggest a controller that will satisfy your requirements. I picked a controller manufactured by Specialty Concepts. It is straightforward yet does the task. And the individuals at the company are a big help in helping you to choose the right kind for your panel. When you contact them, they will need to understand what size panel (wattage) you have and what the voltage is. Check them out at specialtyconcepts.com. I also bought my controller from the people at Sun Electronics in Miami.

The associates at Specialty Concepts have also calculated how heat will influence current flow and recommend that their controllers not be positioned in engine rooms as the heat created will diminish the controller effectiveness by approximately 25%. I positioned mine in the electrical panel under the lower helm. And finally, you will require the appropriately sized cables to go from the controller to your batteries and a fuse to connect the controller to the battery bank. In choosing the correct fuse, you need to find the short circuit current for your panel and select the breaker at 125% of that number. This will give you the amperage of the breaker you will need. Your controller operating manual will have guidance on these also.

Having a solar panel to maintain your batteries seems great but you'll need to have a method to monitor your batteries. I opted to also install a Trimetric 2025RV Battery Monitor; bogartengineering.com. This smart contraption is wired into your battery bank to give a genuine measurement of voltage going in to the bank, amps being utilized by your trawler, the percent complete charge on the bank, and the amp hours utilized since the previous charge.

Panel Functionality

So we have now installed a 195 watt solar panel as well as an 1800 watt inverter and a battery bank with 443 amp hours. I tested our system this week on the hook with bright skies. I concluded that our power consumption is 112.5 amp hours per day. The freezer alone is the major pull utilizing 60 of the amp hours followed by the refrigerator. Did you know that a normal anchor light pulls 18 amp hours each night? I think I'll investigate LED bulbs now. The battery monitor indicated that our actual draw from the battery bank was merely 65 amp hours which means we got the remaining from the sunlight, a full 42% was from the sun. Now we are able to run the genset for roughly one hour to pull the battery bank up to complete charge.