Installing a Solar Panel Aboard Your Boat

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Following a recent five-day trip aboard our trawler where we had to frequently start up the genset to provide electricity to the 115 volt AC freezer to maintain temperatures, I began to mull over options. We put in an excess of ninety hours on the vessel generator in only five days; time for another oil change! I put in an inverter soon thereafter and that improved the run time for the generator drastically, but there was still work to be completed. I nonetheless needed to keep the batteries fully charged to operate the inverter. Then it occurred to me, why not explore solar panels for use aboard our yacht. Solar panels have been successfully utilized since the mid 1950s, originally utilized in manned space exploration. They have been dropping in cost since roughly 2004 when their popularity really went up. And now with the Green pressure going on, solar panels are as accepted as ever. So I commenced to delve into them and find out how to purchase and mount one; I was in for a big surprise. You can come across many retail vendors over the internet that will sell you a solar panel but nowhere could I locate a detailed description of how to determine what to buy and how to install it; much less on board a yacht. So this piece was written as I made my way through the progression; therefore is a truly a learn-as-you-go article.

What Exactly is a Solar Panel and How Do They Work?

Solar panels are basically any panel that makes use of the sun’s thermal energy to create electricity. A solar panel can be described as a photovoltaic panel, the name used in the business, for panels intended to create electrical energy from the emission of the sun. Despite the group of solar panel being discussed, nearly all solar panels are flat. This is because the surface of the panel needs to be at a 90 degree incline from the sun’s rays for the best angle to soak up the sun’s rays. Solar panels are able to absorb energy from the sun through a collection of solar cells on their surface. Very similar to how a plant is able to take in energy from the sun for photosynthesis, solar cells function in a comparable way. As the sun’s rays hit the solar cells on a photovoltaic panel, the energy is transferred to a silicon semiconductor. The power is then changed into (dc) direct current electrical energy and then passed through connecting wires to ultimately enter a storage battery.

Kinds of Solar Panels

Types of panels most normally used in yachting uses have either multicrystalline or amorphous thin-film cells. Multicrystalline panels are the oldest technology obtainable and in addition the strongest. When sized correctly and paired with suitable 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 bought in flexible varieties so they can roll or fold, or change to the shape of a boat cabin top or bimini. They don’t often have adequate yield for considerable energy replenishment, but can be used to lightly charge a battery bank.

How Much Power Can Solar Cells Make?

Normally, we measure 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 great as 200 watts or even larger. But it is simpler to understand when we change watts to amperage. We calculate these values by multiplying the number of hours the panel is in full sun (usually defined as 5 a 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. We can then figure, 975 watts/12 volts = 81.25 amps per day.

Power Consumption

Before considering which size panel to purchase for your boat, you will need to complete an energy budget to ascertain what sources of power consumption you have aboard while at anchor. I use the at anchor scenario as this is the place you will use the most energy; under power and your trawler can supply its needs without any issues.

Example, if you have 3 inside lights that pull 2 amps each and you keep them on for 4 hours per 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 at anchor.

DC Loads – calculate how many amps hours are used by each appliance

House Lighting
Anchor lights
Refrigeration
Freezer
Electric Toilet
Fresh Water Pump
Sanitation System
Stereo
Other

Inverter Loads

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

Calculate the amp hours used by each appliance

Computer
Microwave
Refrigeration
Freezer
Heater
Hair Dryer
Television
Other

Add up your overall daily energy use AH/per day

Solar Energy Creation

Different sources of power similar to solar panels can replace the amp/hrs pulled from the batteries. But similar to the power budget that determined 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 a gauge; complete accuracy can only be where the panel production is constant and a solar panel might at times function ineffectually due to cloudy skies. Compare the day by day power use in AH/Day to the solar power creation. Your solar energy production must be larger than the use. If it is not, pick a bigger wattage panel and recalculate. Always purchase more solar panel output than you think you will need; some professionals recommend at least 30% in excess. used boat

Case in point – 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 got your solar panel, where do you put it on board your yacht? As we mentioned before, installing the panel ninety degrees to the sun is best. You will get the best power production this way. But on yachts, finding a fitting spot is tricky at best. A number of boaters put them on brackets placed on the rails, others position them on top of the bimini, and I have seen them positioned on the trawler dingy stanchions. But wherever you decide to mount them, bear in mind that to get the most 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 while at anchor, the boat will turn to the sun twice daily because of the tides. I opted to mount our panel on the top of the boat back deck hardtop in a horizontal position. Here it will get the greatest view of the sun and be clear from the radar arch shade as the boat swings at anchor. The slope toward the sun is not precisely at ninety degrees but it will have to do. I selected a 195 watt panel so I get almost a 50% reserve ability in my panel to compensate for the small inefficiency of the sun’s angle. We got the panel from Sun Electronics in Miami, sunelec.com as they had the best prices I could find anywhere on the web. But bear in mind, panels must be shipped using freight as they are heavily packed to reduce the chance of damage so be sure to calculate those expenses in your acquisition.

 

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