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We recently took a five day cruise on our boat and had to continually power up the genset to provide electricity to the 115 volt ac freezer to sustain temperatures. I then began to contemplate alternate options. We put in excess of 90 hours on the vessel generator in only 5 days; time for another oil change! I installed an inverter soon thereafter and that improved the run time for the generator appreciably, but there was more work to be completed. I still needed to keep the batteries charged to run the inverter. Then it dawned on me, why not explore solar panels for use aboard our vessel. Solar panels have been effectively used since the mid 1950s, originally used in manned space exploration. They have been dropping in cost since roughly 2004 when their popularity increased significantly. And now with the Environmentally friendly attitude abounding, solar panels are as popular as ever. So I began to delve into them and determine how to purchase and install one; I was in for a shock. You can locate many retail suppliers on the internet that will sell you a solar panel but nowhere could I come across a comprehensive explanation of how to decide what to get and how to install it; much less on board a yacht. So this piece was born as I made my way all through the progression; thus is a truly a learn-as-you-go article. What Exactly is a Solar Panel and How Do They Work? Solar panels are in theory any panel that makes use of the sun's thermal energy 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 power from the emission of the sun. Despite the class of solar panel being mentioned, virtually all solar panels are flat. It is because the face of the panel must be at a ninety degree slant from the sun's rays for the most favorable angle to absorb the sun's rays. Solar panels are able to absorb energy from the sun through a group of solar cells on their face. Much like how a plant can absorb energy from the sun for photosynthesis, solar cells function in a comparable method. As the sun's rays hit the solar cells on a photovoltaic panel, the power is moved to a silicon semiconductor. The power is then changed into (dc) direct current electrical energy and then passed through connecting wires to finally enter a storage battery. Kinds of Solar Panels Types of panels most normally used in boating functions have either multicrystalline or amorphous thin-film cells. Multicrystalline panels are the oldest technology available and also the most effective. When sized correctly and paired with proper batteries, these are the panels to make use of for operating large loads such as refrigeration. Amorphous thin film solar panels are only about 50% as effective as multicrystalline panels, but can be purchased in bendable forms so they can roll or fold, or correspond to the contour of a vessel cabin top or bimini. They don't often have sufficient production for large energy replacement, but can be used to trickle power a battery bank. How Much Energy Do Solar Cells Make? Generally, we gauge solar panels by wattage and that is how we purchase them. You can get solar panels for yachts as little as ten watts to as great as 200 watts or even larger. But it is simpler to understand when we change watts to amperage. We arrive at these numbers by multiplying the number of hours the panel is in full sun (frequently defined as 5 per day in Florida) by the panel's wattage. For a 195 watt solar panel the amount produced would be 195 x 5 hrs = 975 watts/day. Taking it step further, 975 watts/12 volts = 81.25 amps per day. Power Use Before you consider what size panel to buy for your boat, you will need to complete an energy plan to ascertain what sources of energy consumption you have aboard while on the hook. I utilize the at anchor situation as this is where you will use the most energy; under power and your boat can provide its needs without any problems. Case in point, if you have 3 interior lights that pull 2 amps each and you leave them on for four hours per night, your use 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 functioning while anchored out. DC Loads: calculate the amp hours used by each item below: House Lighting Anchor lights Refrigeration Freezer Electric Head Fresh Water Pump Sanitation System Stereo Other Inverter Loads: Inverter loads also utilize DC power but they are running AC appliances and appliances. If you want to change watts to amps use (12watts/12 volts = 1amp). Calculate the amp hours used by the items below, if applicable: Computer Microwave Refrigeration Freezer Heater Hair Dryer Television Other Compute your total daily energy consumption AH/per day Solar Energy Production Different sources of energy like solar panels can replenish the amp/hrs pulled from the batteries. But like the power budget that calculated your usage, you will also need to compute your re-supply of amp hours. Keep in mind the formula - (12 watts/12 volts = 1 amp). But be mindful, the formula is only an estimate; complete accuracy can only be where the panel production is constant and a solar panel may now and then run inefficiently as a result of cloudy skies. Compare the day by day energy consumption in AH/Day to the solar energy production. Your solar energy creation must be greater than the utilization. If it is not, select a bigger wattage panel and recalculate. Always get more solar panel output than you imagine you will need; some professionals advocate at the least 30% in surplus. Illustration - 100 watt solar panel/ 12 volts = 8.3 amp x 5 hours = 41.66 AH/Day production Installing Your Solar Panel Now that you have a solar panel, where do you mount it aboard your trawler? As we mentioned already, putting the panel ninety degrees to the sun is optimum. You will receive the greatest power creation this way. But on vessels, finding a fitting place is tricky at best. Some boaters put them on brackets placed on the rails, others position them on top of the bimini, and I have seen them located on the trawler dinghy stanchions. But wherever you choose to put them, bear in mind that to get the most out of them they must be in the open, free from any shade from booms, yacht radar arches, or cabin structures. Remember that on the hook, the vessel will veer toward the sun two times daily because of the tides. I decided to install our panel on the top of the yacht sundeck hardtop in a horizontal manner. At this point it will have the greatest view of the sun and be clear from the radar arch shading as the boat swings at anchor. The angle to the sun is not right at 90 degrees but it will have to suffice. I selected a 195 watt panel so I have roughly a 50% reserve capability in my panel to make up 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 pricing I could come across anywhere online. But bear in mind, panels have to be shipped by way of freight as they are heavily packed to decrease the chance of damage so make sure to determine those costs in your purchase. What exactly is the best technique to fasten the panel to your boat? There are a number of manufacturers of solar panel mounting rails and supports but almost all of them are made for roof or ground mounting. West Marine does supply a product for mounting small panels to the rails. A lot of boaters construct their own mounts. I found a mount made by Sunsei referred to as a Sunsei Glue Mounting Kit that is attached to the trawler and panel using 3M 5200 Marine Adhesive. The mount enables the panel to be placed with roughly 2 inches of room under 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 incredibly specialized and dangerous; if you are not at ease in performing this part of the chore, please check with a trained marine electrician. Your panel will be prewired for securing to your trawler but you will want to supply the linking cables that will also be sold by your panel provider; they are referred to 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 need a controller. The controller regulates the power stream from the panel to your batteries keeping your batteries charged yet stopping over-charging. Some controllers are easy but others have LED displays indicating the amount of charge etc. The more whistles and bells the more pricey it will be. Your panel supplier will be able to recommend a controller that will satisfy your needs. I selected a controller made by Specialty Concepts. It is straightforward and also does the job. And the folks at the firm are a huge help in assisting you to choose the correct model for your panel. When you contact them, they will want to be familiar with which size panel (wattage) you possess and what the voltage is. You can find them at specialtyconcepts.com. I also got my controller from the people at Sun Electronics in Miami. The associates at Specialty Concepts have also determined how heat will affect current flow and advocate that their controllers not be placed in engine rooms since the heat produced will reduce the controller efficiency by about 25%. I put mine in the electrical panel under the lower helm. And finally, you will need the appropriately sized cables to run from the controller to your batteries and a fuse to connect the controller to the battery bank. In selecting the right fuse, you will need to find the short circuit current for your panel and select the breaker at 125% of that figure. This will give you the amperage of the breaker you will need. Your controller operating guidebook will have guidance on these as well. Having a solar panel to preserve your batteries appears to be a great idea but you will also want to have a method to monitor your batteries. I decided to also install a Trimetric 2025RV Battery Monitor; bogartengineering.com. This gadget is wired into your battery bank to give an accurate measurement of voltage going in to the bank, amps being utilized by your trawler, the percent full charge on the bank, and the amp hours used since the last charge. Panel Operation So we have now mounted 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 anchored up with sunny skies. I concluded that our energy use is 112.5 amp hours per day. The freezer is the main draw utillizing 60 of the amp hours followed by the refrigerator. Did you know that a regular anchor light pulls 18 amp hours a night? I think I'll check out LED bulbs now. The battery monitor told me that our actual draw from the battery bank was merely 65 amp hours which means we received the remaining from the sunlight, a full 42% was from the sun. Now we are able to turn on the genset for around one hour to bring the battery bank up to full charge. Mike Dickens, the author, is a live aboard boat owner and owner/Broker of Paradise Yachts in Florida USA. Paradise Yachts offers used quality yachts to customers worldwide. 904/556-9431 Visit the Paradise Yachts website to view our selection of Used Trawlers, Used Motor Yachts, and Used Sailboats for Sale
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