Solar panels

Every year, more and more yachtsmen want to install solar panels on their multihulls. And they’re right to do so: photovoltaic energy is natural and clean, and above all, it enables them to be self-sufficient during long crossings and at anchor. The result of this craze for solar energy - on land and at sea, in fact - is an explosion in the market, accompanied by a wide range of products. Many boat builders are now integrating custom solar panels into the superstructures of their models.
Before starting your installation, it’s a good idea to give careful thought to your project, and in particular to the power you’ll need and the location of these solar panels. And be aware that not all technologies are created equal. Here are a few important points to consider.

Two main technologies

Solar panel technology is evolving rapidly, and today there are two main kinds of solar panel on the market: monocrystalline and polycrystalline. These two technologies offer distinct advantages and disadvantages, depending on the specific needs and constraints of each project.

Polycrystalline technology, a budget friendly choice
Polycrystalline solar panels are made from solar cells composed of several silicon crystals, making them relatively inexpensive to produce. While polycrystalline panels are not the most efficient, they do offer a good compromise between performance and cost. Polycrystalline solar panels are also considered relatively durable, with little risk of breakage or degradation over time.

Monocrystalline technology for greater efficiency
Monocrystalline solar panels are made from pure silicon solar cells, giving them high energy efficiency. In fact, monocrystalline panels are significantly more efficient than polycrystalline panels, which means they can produce more electricity per square meter of surface area. The resulting truism is that these panels take up less surface area for the same power output. What’s more, monocrystalline solar panels perform better for longer, and charge better when sunlight is low. On the other hand, they are slightly more expensive than polycrystalline panels.

A choice dictated by space and budget
The choice between monocrystalline and polycrystalline solar panels depends on your needs and your budget. If space is limited and your budget allows, monocrystalline solar panels are the best option, as they offer better performance for a smaller surface area. On the other hand, if cost is a determining factor, polycrystalline solar panels can be an effective alternative with good value for money.

Flexible or rigid solar panels?

Today’s solar panels are available in rigid or flexible form and look very different indeed. So, what are the advantages and disadvantages of each type of solar panel?
The first criterion for deciding between a flexible or rigid panel is, of course, where the panel is going to be installed. If you don’t have a flat surface, the choice is quickly made. If you do, it’s up to you to weigh up the pros and cons.

Rigid solar panels, cheaper and more efficient

Advantages:
1. Energy efficiency: rigid solar panels tend to be more efficient in terms of electricity production per square meter than flexible panels.
2. Durability: rigid solar panels are generally more durable and have a longer lifespan than flexible panels.
3. Lower cost: in general, rigid solar panels tend to be less expensive than flexible solar panels.

Disadvantages:
1. Difficulty of installation on irregular surfaces: due to their rigidity, rigid solar panels can obviously be more difficult to install on irregular surfaces.
2. Weight: rigid solar panels are heavier than flexible ones, which can be a disadvantage if you intend to install a number of them.

Flexible solar panels: they fit anywhere!

Advantages:
1. Lightweight and flexible: this makes them ideal for installation on multihulls.
2. Easy to install: their flexibility means they can be installed just about anywhere and are easy to attach.
3. Discreet: flexible solar panels can be integrated more discreetly and aesthetically on different surfaces without compromising the overall appearance.
4. Shock resistance: they are more resistant to shock and vibration than rigid solar panels, making them suitable for moving environments such as multihulls.

Disadvantages:
1. Slightly higher cost: in general, flexible solar panels can be a little more expensive than rigid solar panels, due to their specific technology.
2. Less efficient: flexible solar panels may be slightly less efficient in terms of electricity production per square meter than rigid solar panels.

How many solar panels do you need?

Before you start installing solar panels, the first thing to do is establish the power you need.
To calculate the amount of electricity you’ll need on board a multihull, you need to take several factors into account, including all the electrical equipment you use, their energy consumption and the length of time you use them.

List the electrical appliances on board
Make a list of all the electrical appliances you use on board your multihull, including lights, galley appliances, electronics etc.

Determine their power consumption
Consult the user manuals of the appliances to find their power consumption in watts. If this information is not available, you can use a wattmeter to measure wattage consumption when appliances are in use.

Estimate how long each device will be in use
Make a realistic estimate of how long each appliance will be used each day. For example, you may estimate that the lights will be used for 4 hours a day, while the refrigerator may be on 24 hours a day.

Calculate the daily consumption of each appliance
Multiply the power consumption of each appliance by the estimated duration of daily use to obtain the daily power consumption of each appliance in watt-hours.

Add up daily consumption
Add up all the appliances’ daily consumption to obtain the total daily electricity consumption for your boat.

Convert to ampere-hours (Ah)
Since batteries are generally indicated in ampere-hours (Ah), you’ll need to convert your boat’s total daily consumption into ampere-hours using the following formula:
Ampere-hours (Ah) = Watt-hours (Wh) ÷ Battery voltage (V).
Make sure you know the voltage of your boat’s battery bank, usually 12, 24 or 48 volts.

Consider solar panel efficiency
Solar panels have a percentage efficiency, which represents the ability to convert sunlight into electricity. For example, if a solar panel has an efficiency of 15%, this means it can convert 15% of the sunlight exposed to it into electricity. In concrete terms, a 100-watt solar panel won’t necessarily give you 100 watts of energy.

Calculate the power of the solar panels you need
Divide the watt-hour consumption you’ve calculated by the solar panel’s efficiency ratio to determine the power of solar panels you’ll need. For example, if your consumption is 200 Wh per day and the solar panel’s efficiency rate is 15%, then the required solar panel power will be 200 Wh / 0.15 = 1,333 watts, or approximately 1.3 kW.

Add a safety margin
It’s a good idea to add a safety margin to your calculation to allow for variations in sunlight, energy losses and other unforeseen factors. In general, a safety margin of 10 to 20% is often recommended. Finally, don’t forget that your batteries store energy and therefore contain more electricity than your solar panels can produce instantaneously.

Solar panels installation

Once you’ve calculated the amount of electricity you’ll need on board your multihull, you can choose the size and number of solar panels and design an electrical circuit that incorporates a charge controller adapted to your battery bank.

Determine the best location for your multihull’s solar panels
Now that you’ve defined your needs and selected the technology you need, it’s time to decide on the best location for your solar panels. Multihulls have a major advantage in that they offer a large surface area and ideal locations for such installations. However, you need to find the ideal location based on a number of criteria.

Sun exposure
Solar panels need to be installed in a place where they will receive maximum exposure to the sun for optimum electricity production. Be sure to choose a location that is not overly shaded by items such as the mast, boom, sails, or other equipment that could block sunlight.

Tilt and orientation
Ideally, solar panels should be installed with a tilt and orientation that maximizes exposure to the sun. On a multihull, this may mean installing the solar panels on a tilted support to follow the angle of the sun throughout the day.

Available space
Take into account the size and shape of your multihull to determine the space available for solar panel installation. Make sure the solar panels do not interfere with the crew’s movements. The cabin coachroof or flybridge T-top are good solutions.

Avoid high-traffic areas
Even if you’ve opted for flexible panels that can be walked on, trampling them non-stop won’t improve their lifespan. So choose areas that are safe from knocks and foot traffic.

Pay attention to aesthetics
Just because you’re going solar doesn’t mean you have to turn your catamaran or trimaran into an industrial complex! Try to find a location that won’t detract too much from the lines of your multihull.

Weather protection
Solar panels should be installed in such a way as to be protected from the worst weather on board - i.e. exposed to salt water at the very least. Avoid areas that are regularly exposed to waves and spray. Make sure the panels are properly fastened to withstand the most severe marine conditions.

Some location ideas

On superstructures
The coachroof, the bimini or the top of the hard-top are probably the perfect places to install photovoltaic cells. Installed in this way, solar panels benefit from maximum sunlight, are sheltered from traffic and do not detract from the aesthetics.

On deck
This positioning may seem ideal, but in the end it’s not, because it’s located in a high-traffic area, which in the long term can lead to deterioration of the panels. If it’s a sailboat, the cells will also often be in the shadow of the rigging and especially the sails. Finally, unless you have a very large boat, the available surface area is not that great.

Vertically on the hulls
Unless you own a Sunreef ECO, this option is still not very feasible, as it requires photovoltaic cells integrated into the topsides. However, this is an excellent location, since apart from direct exposure to the sun, the panels benefit from reverberation off the surface of the water.

On an arch
This is the ideal solution for small trimarans, as it allows the panels to be installed «outside» the boat. However, this is only possible for a limited number of solar panels. Some Owners may be tempted to cover the cockpit with panels, which provides shade, but also cuts off the view of the sail plan while generating significant windage.

Polycrystalline panels are less expensive, but their output is lower than that of monocrystalline panels.

The electrical installation must include a charge controller and a good battery bank. A specific interface is obviously a plus.

Sunreef Yachts offers photovoltaic cells integrated into hulls, superstructures and even masts.

Air conditioning and refrigeration are the biggest energy consumers on board.