Solar panels: what you need to know before fitting them on board

Despite Covid-19 we will sail this summer, and how. Starting June 3, when it will be allowed to move from region to region, all boat owners will actually have access to their boat. And since from May 18 we will be able to meet with friends as well as relatives, it seems plausible to us that very shortly we will be able to return to the boat also not only as “family,” taking the necessary precautions and with a lot of common sense (masks, social distancing in arriving at the boat, etc.). What will this summer’s cruise be like? Definitely under the banner of the roadstead. So much sparse: the less you stay ashore, the lower the risk of coming in contact with the virus.

Certainly a cruise involving many nights at anchor brings with it the problem of energy autonomy: hydro generators, wind turbines, solar panels. All interesting solutions for energy storage for on-board utilities (refrigerator, lights, windlass, air conditioner…).

Leaving aside hydro generators, a great solution if you sail a lot, in the Mediterranean, cruise passengers are asking themselves. “solar panels or wind generators?” The debate has animated the discussions of sailors for a long time, but in recent years it really seems that Aeolus is getting defeated by the sun… The reason is quite simple, especially in our latitudes: the output of a wind turbine under fifteen knots of wind is really minimal. Solar panels, for their part, on the other hand, are winning over more and more boaters, and not only those who engage in long sailing.

Environmentally friendly and quiet, the panels moreover have more and more deck area available. Above all, charging capacity (so-called energy efficiency), weather resistance and flexibility have definitely increased in recent years.

PANEL FAMILIES
Solar panels are divided into three families: flexible panels (10% flexibility and above), semi-rigid panels (3 to 8% flexibility) and rigid panels. In contrast, there are practically no soft panels of the old generation, which were completely collapsible, on the market anymore.
By now when we talk about soft panels we mean those that have good flexibility. The characteristic that must be taken into account when choosing a solar panel is the type of cells of which it is made. The quality of the cells, in fact, determines the efficiency of the panel, that is, the percentage of solar energy it is able to convert into electricity. There are monocrystalline silicon cells and others made of polycrystalline silicon.

MONO OR POLYCRYSTALLINE?
The former are generally more efficient (and expensive) than polycrystalline silicon. It is not at all true-as we often hear-that polycrystalline cells are more efficient in cloudy skies or low light conditions. It is safe to say that the performance of any type of cell (mono or polycrystalline) collapses inexorably in cloudy skies.

WHERE DO I MOUNT IT?
Installing solar panels on board is a fairly simple operation, you just need to have a minimum of electrical skills. First, you need to figure out whether to opt for a rigid or flexible panel, depending on where you want to mount it. In general, rigids are mounted on roll bars, thus being able to orient them according to the position of the sun and gaining–shade on deck!

Instead, soft and semi-rigid are often installed on the deckhouse, aft or forward of the mast. However, they must demonstrate good resistance to saline agents. Soft panels, for their part, are mainly mounted on bimini. Three elements are needed for installation: the panels, which must cover on-board consumption; the charge controller, which must avoid overcharging the batteries; and finally, precisely, a battery pack for energy storage and distribution. In some ways, the charge controller is the most important element in a photovoltaic system.

THE IMPORTANCE OF THE REGULATOR
Solar panels used in boating deliver electricity at a voltage that varies (depending on the type of panel) between 5 and 30 volts. To properly charge service batteries, the voltage should never exceed 14.7 volts for 12-volt systems and 29.4 volts for 24-volt systems. If you choose an unsuitable charge controller, you risk losing quite a bit of the energy produced by the panels.

There are three charge controllers on the market:

– PWM (pulse Width Modulation). This is the least expensive and simplest type. Its electronic circuits can only lower the panel voltage to a value suitable for battery charging.
– MPPT (Maximum Power Point Tracking). Also called “Tracer.” These regulators have more sophisticated, and for that reason more expensive, circuits that not only lower the voltage as in PWM, but also increase the current sent to the batteries so that the total power generated by the panel remains the same.
– Step-Up. Also called “boosters.” These are somewhat special regulators that should only be used in cases where the panel voltage is less than that required for battery charging (example: using a 10-volt panel in a 12-volt system, or using an 18-volt panel in a 24-volt system). In fact, the technology used in these charge controllers allows the voltage of the panel to be raised to a value suitable for charging.

HELP US KEEP YOU UP TO DATE

Journal of Sailing journalists, together with Barche a Motore and Top Yacht Design are committed every day to ensuring quality, up-to-date and correct information about the boating world free of charge through their websites. If you appreciate our work, support us by subscribing to the magazine. The annual subscription costs only 49 euros!

Also support us on Motor Boats and Top Yacht Design!

——————————————————

SIGN UP FOR OUR NEWSLETTER, IT’S FREE!

To stay up-to-date on all the news from the world of sailing, selected by our editorial staff, sign up for the Sailing Newspaper newsletter! It is semplicissimo, just enter your email below, accept the Privacy Policy and click the “Sign me up” button. You will then receive on your email, twice a week, the best sailing news! It’s free and you can unsubscribe at any time, no obligation!