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Energy autonomy on board is the goal of every ship owner. A target that can be achieved through many different technological approaches. One of these, however, has become the indisputable preferred choice  for cost-efficiency and zero environmental impact: solar energy.

Thanks to the rapid progress in recent years in the energy industry, nowadays most sailboats are provided (also) with photovoltaic panels. Solar systems able to keep on board batteries fully charged in winter months are available with some dozens euros, while just a slightly higher investment is required to cover the normal energy need of a roadstead cruise.

In bigger boats solar panels are an integral part of a system including different energy sources, from the traditional generator (not exactly ecological but surely very useful if not too noisy) to wind turbine generators and hydrogenerators. While a traditional generator requires an engine running and fuel, while to operate a wind generator some wind force is needed and therefore constantly updated weather information and while a hydrogenerator necessarily requires hull motion in water, none of this is necessary to have solar energy. Solar panels provide ready energy all day long. Of course all relevant factors have to be taken into account such as technology of the panels installed (which affects the initial investment), technological level of the system, good or bad solar radiation condition, etc. etc. However, even considering all the involved variables, solar panels are chosen by most of the ship owners who want to spend the shortest time possible at a dock 220V charging column.

Leaving aside the endless debate on the different typologies of panels available on the market and produced by leading Italian companies or by Chinese companies or by companies from different countries and on the quality and peculiarities of each of them, every ship owner shall make his own assessment and decide according to his needs and, above all, his budget. The second step is to choose how and where solar panels will be positioned as sailboats are well-known for their lack of space and, moreover, they need to be manoeuvred during sailing.

So let’s see what are the most common technical options about where to mount solar panels on a sailboat. There are essentially five installation options: a bimini, a frame placed aft, coach roof, life lines, poles.

Let’s begin with the bimini: a lightweight cover made of fabric stretched on a steel frame for sun and rain shading during sailing or when resting at anchor in a roadstead. It is probably the option chosen by most of the sailors due to its clear advantages: it does not hinder on board manoeuvring, it allows total radiation of the panel being this far from shades areas caused by the mainsail and/or the boom and, last but not least, following some tips the panel is easily removable and can quickly be safely stored below deck in case of an incoming storm or other troubles.

So, the bimini option is a very good one, however some precautions are to be taken. First of all only flexible or semi-flexible panels can be installed on a bimini as they are lighter than rigid ones. Special attention shall be paid to solar panel overheating. If panels get too hot, they can overheat and even burn the bimini. Several specialized companies supply installation kits with Velcro strips, zippers and buttons designed for fabric installation.

In case of DYI, pay attention to leave sufficient space below the panel to allow for ventilation. Also proper thermal insulation is essential. But what are the cons of this option? Only one, I daresay: panels cannot be oriented to best catch sunlight and therefore solar radiation can never be perpendicular to the panel surface. However, their being so fit for the purpose highly balances this unique drawback.

Those who do not want, or cannot choose the bimini option for lack of space can install the panels on a frame similar to that of a bimini, i.e. a simple steel arch frame placed aft. This option offers a couple of additional advantages: the steel frame can hold the weight of traditional (and less expensive) fixed panels and panels can be oriented on an axis, which is not ideal yet surely better compared with energy collected by static solar panels.

The rapid technological growth of recent years has conceived solar panels that can be walked on. They offer clear pros such as easy installation (they can be secured to eyelets even only through houselines or Velcro strips) and low weight that allows fast and effective positioning during the day in order to best catch solar radiation. These panels are usually installed in the area directly in front of the mast, or behind it, or on the coach roof.

However, there are also some cons as both the mast and the sails (as well as the space under the boom) create shade areas affecting the panel performances. Add to this that these panels can be walked on, but this does not mean they cannot get damaged. Standing on the coach roof or in the mast area during long manoeuvring may cause troubles.

An option widespread abroad, where being efficient is known to be more important than looking good, is to mount the panels on the transom. This installation option, also adopted by Mini 650, offers a unique advantage: their complete orientation towards the sun. A joint placed under the frame provides an almost total orientation on the two axes. Houselines and cleats may serve to the purpose. Only rigid panels can be housed on the transom, the same as for the arch frame option.

Lastly, there is one more option: to install the panels longitudinally outside the life lines, overhanging water. This installation is chosen by those who do not want to have either poles or frames aft. Two are the pros: easy installation and orientation possibility.

They are fastened to life lines and houselines just through the eyelets many panel are provided with or, if you choose, to a couple of small telescopic supports to expose panels to maximum sun radiation (of course on a single axis). This option allows panel removal in a few seconds to store them below deck. Another advantage is that the life line area is more roomy than elsewhere and a larger number of panels can be installed compared to a bimini. Now let’s see the cons: panels are not installed on the boat but they overhang water and are beaten by waves: this can be risky as they are fragile. When manoeuvring in a marina, panels shall be positioned inside life lines to reduce to the minimum the risk of breakage. Sun exposure is good but not very good.

In short, this option is a good choice in case of long cruises and long time spent lying at anchor in a roadstead, a little less if the boat often returns to port. But it is also true that solar panel are not very much needed by a boat that often returns to port.

Stefano Sergi
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