solar power yacht

• Yachting World
• Digital Edition

Review: Silent 55, the extraordinary solar powered yacht

• January 18, 2019

Silent Yachts is tapping into the solar zeitgeist and creating a new meaning for the term ‘powercat’.  Sam Fortescue reports

There is a slow, silent revolution under way in the yachting world. It is a revolution that is introducing tonnes of lithium and a sprinkling of silicon to the spec list of new boats. Holding out the promise of silent mobility, plus limitless domestic power on board, it made a big splash at the last Cannes Festival of Yachting – not least thanks to the new Silent 55 catamaran which debuted there.

From the pontoon side, the Silent 55 looks like a typical modern catamaran, with a big coachroof studded with windows and a flybridge helm. Except there’s no mast. Now, bear with me here. I realise that this is a sailing magazine, but we will shortly get back to more familiar territory. The unique qualities of this catamaran only become apparent from up top, where an expanse of solar panels stretches away fore and aft, embedded into the coachroof. The hard top itself carries yet more panels, and can be folded down flush to give an unshaded solar array of 49m2. During the heat of a summer day in the Med, this is capable of generating 10kW of power and up to around 60kWh in the course of the day.

But to make a solar system work in reality, Köhler had to go back to the drawing board on yacht design. The saloon and hulls have extra thermal insulation to keep air-con losses down, and the use of carbon and aramid in key areas helps reduce the overall weight to a decent 17 tonnes (a Lagoon 52 weighs 22.5 tonnes). He has tried to keep windows out of the direct sun with long overhangs and in contrast to the Lagoon’s 12 deck hatches, the Silent 55 has just two.

Holistic design

On the other hand, it has lots of opening windows, to allow a natural draught to do its job. “It’s a holistic approach – you can’t take the batteries and the drivetrain and drop it into another boat.”

Of course, using the propulsion system quickly takes its toll of the boat’s 140kW battery bank. The model on display at Cannes had two 135kW motors, giving you just half an hour of silent motoring flat-out, albeit at a top speed of over 20 knots. More reasonable 30kW engines and a single-digit speed give you greater range. Nonetheless, the electric drive alone isn’t going to allow you to outrun a storm, or race home after a day at anchor, so the boat is designed to work with a generator hidden in the heavily insulated transom of its starboard hull. At cruising speed of around 5-6 knots, Köhler says there is rarely any need to use the generator, citing an owner who has just emailed him triumphantly about a second year totally generator-free. “In the end, you have to compare it to the performance of a sailing boat,” Köhler says. “It is as fast as a sailing boat in similar conditions – after all, there is no wind without sun.” He went so far as to tell me during the sea trial in Palma, Mallorca, that he believed the majority of sailors would happily dispense with the hassle of sails and a rig if only they could enjoy silent motoring and anchoring. “As soon as people realise the incredible concept of this boat, they won’t understand why they ever did anything else.”

The market does not seem to agree with him – yet. Sales of the boat have been good – they have already sold six, five of which are already in the water. But of those, four customers have taken the sail option, which means planting a 19.7m tall mast complete with boom and rigging slap bang in the middle of the coachroof solar array. “I was a bit amazed,” Köhler admits. “The shade from the rig reduces the energy generated by the solar area, while it costs more and is heavier, so consumes more fuel. Maybe it is for optical reasons.” In fact, the shade of the rig slashes the average yield of the solar panels in half. In the Med, that means around 30kWh per day. But perhaps it figures. The typical profile of buyers is an environmentalist who has a Tesla electric car and is “an early adopter who likes to have things before others”. And at low speeds, with modest use of the air-con, the reduced energy generation should still cover daily consumption.

The performance under sail should be reasonable because of the lightweight build of the boat, its broad 8.47m beam and stub keels added to each hull. Control lines are led back via conduits in the coachroof to the flybridge helm station, to make single-handing under sail a possibility.

More interesting, I think, is a sort of halfway-house option using a kite rig. This optimises the performance of the solar panels and gives plenty of propulsion. On the smaller 55 and the 64, Silent Yachts currently recommends a 19m2 kite that costs around €25,000 – a fraction of the cost of a new mast, boom, shrouds and sails. “The sail automatically makes a figure of eight above the boat, and you can steer it with a joystick or an app on an android phone,” Köhler explains. “It can propel the 55 at up to 6 knots, even in light winds.” Perfect for an Atlantic crossing, then.

For the bigger Silent 79, which will hit the water in the summer, a commercial grade Sky Sail system needs to be used – a smaller version of the ones used on cargo ships. This kite can propel the boat at ten knots, but it costs more than ten times as much as its smaller cousin. Both are capable of pulling the boat upwind. So far, so new. But outside the novel energy and propulsion system, the Silent 55 aims to do what many other cruising catamarans are trying to achieve. “Most of our clients order for circumnavigation and long-term cruising,” Köhler says. So the boat is aimed to be as comfortable and capable as possible with watermakers, TVs and an induction hob that all capitalise on the boat’s abundant energy. A flexible configuration allows owners the choice 
of between three and six cabins – the latter designed for charter. The owner’s cabin lies forward of the saloon, under the windows of the coachroof, which provide magnificent views and abundant natural light. There’s a walk-around bed and steps down into the starboard hull give access to an en-suite shower room and heads.

In my view, the best cabin lies aft of this, accessed in the traditional manner down steps out of the saloon. The king-sized bed lies athwartships and the shower is larger than that of the master cabin. There’s more space down here, better headroom and still plenty of light courtesy of the many hull lights.

When I had the chance to sea trial the Silent 55, albeit in motorboat format, I jumped at it. It was a contrary autumn day on Mallorca with 15 knots breeze – just a shame, then, that this wasn’t one of the sailing configured versions.

To start with, getting on board is made really easy courtesy of deep boarding platforms on the skirts. She feels rather square because of that vast, glazed saloon with its deep overhang, and perhaps because of the utilitarian nature of the hard top, which is really about supporting more solar panels. Nevertheless, the side decks are broad and uncluttered. The space up top is designed to concertina down flat, hence the hydraulic rams, fold-down seat back and lowering console. It makes a great sailing position, though, with all round visibility, and is also perfect for sundowners at anchor. When the rain comes down, this feels quite exposed, but there is a fully sheltered helm at the front of the saloon, and it is also possible to drive the boat from anywhere using a tablet thanks to smart electronics. Under power, the handling is superb. The quietness of the motors is astonishing, and I gather they’ll be inaudible on the next boat, which will do away with the gearbox. Even in the aft cabins, directly above the motors, there is no more than a distant hum. The boat responds instantly to the power and the wind seemed to have no impact at all. As with any propulsion system, the power consumption jumps as you pile on the speed – it was sobering to see. At 6 knots, both motors drew 10kW but at 8 knots it was closer to 30kW. I liked the huge saloon with its raised table for 360º views. And the sliding door and window gives great access aft, connecting the saloon and cockpit in fine conditions. The finish was smart and in muted tones, feeling more Scandinavian than German.

Intriguingly, at least it seems to me, Köhler has tapped into something with the concept behind Silent Yachts – but not entirely for the reasons that he expected. Buyers are opting for the sail or kite versions of the boat because they want a comfortable wind-powered craft with abundant, quiet energy on tap. It brings a whole new meaning to the 
term ‘powercat’

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True ecotourism

no more fuel

The SoelCat 12 is an energy autonomous solar electric boat, designed from the ground up as a fully sustainable excursion vessel to enjoy the sea. The solar catamaran brings  true eco-tourism  to water-bound operators, communities, resorts, lagoons and nature reserves. With no CO2 or noise emissions involved, we can save the ocean and offer a better experience to our guests! The heart of the concept is  silence : being on board without any distractions lets the journey become the destination!

“Being on the solar catamaran gives you a feeling of total relaxation and freedom. The energy autonomous boat is powered by clean energies and we don’t have to worry about harming the environment with dirty exhaust fumes, fossil fuels or complicated maintenance! Our guests love the quietness and the openness of the vessel, which make every sunset cruise a very special moment!”

S. Dekeunynck, French Polynesia

electric from the start

The SoelCat 12 solar electric catamaran is integrally designed for electric propulsion right from the first line drawing to the matched propeller. Every aspect of this vessel contributes towards its highly efficiency for solar electric sailing. The lightweight yet durable fibreglass construction, the large solar roof and the super slender hulls are the major key factors for the solar vessel’s high performance when it comes to speed and range. The electric propulsion system for the SoelCat 12 is superior when it comest to volume and weight.

MOBILE POWER STATION

During downtime, the SoelCat 12 can utilise its large solar array to provide energy for your land based electricity grid. The solar electric catamaran then turns into a mobile power station and is able to feed 8.6kWp into the AC grid or provide power at remote places where no grid is available. The 120kWh  lithium battery  system supplies all the energy required for save operations during day and night.

SPECIFICATIONS

• Running Time (battery only)
• Running Time (with solar)

“Every detail on the boat is perfect – gorgeous spaces to relax, great spots to view the sunset or the marine life, and even a bar! My favorite moment of all was after sunset, when an incredible manta ray came to say hello, drawn by the underwater lights of the solar catamaran.”

S. Lee, New Zealand

fully customizable

The deck space of the solar electric boat can be customised to your wishes and host a variety of seating arrangements and layouts. Choose classic yacht fittings, luxurious and comfortable. Or practical and economical deck wear and simple bench setup for water taxi services. Furthermore, the electric catamaran can be equipped with a day head in the port side hull.  Get in contact with us now  to learn more about the different options and to discuss your personal requirements with your Soel Yachts contact partner.

The solar electric catamaran can be equipped with removable roll down screens on every side for flexibility in every situation. Screens for sun shading can be applied on good days, while transparent rain screens protect your guests in bad weather conditions. When the screens are not in use, the comfortable SoelCat 12 lounge layout offers spacious space options in the hulls and underneath the furniture.

SUSTAINABLE SEA TRANSPORT

With both the Okeanos Foundation and Soel Yachts sharing a vision of sustainable sea transport and striving for a healthier planet, we are honoured that our partner, the Okeanos Foundation has funded and supported the development of the SoelCat 12. The first SoelCat 12, named the ‘Okeanos Pearl’ is the first energy autonomous vessel for the ecotourism industry and will pave the way for more sustainable coastal water vessels in many different sectors. The Bora Bora Pearl Beach Resort is proving a pioneering spirit by operating the solar electric Okeanos Pearl. As the first resort, they are offering truly sustainable, noise and emission-free excursions in the pristine lagoon of Bora Bora to their guests.

Demountable

The SoelCat 12 can be delivered as a demountable solar electric boat, which fits into two 40ft high cube containers. Such compact dimensions enable ease transport of the catamaran at affordable rates to destinations all over the world. Neither lamination processes or specialized tools are required for the SoelCat 12’s quick assembly on location. For more details, please feel free to follow the link below and discuss your project requirements with your Soel Yachts partner!

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Solar Powered Yachts

Solar panels are a fundamental element of today’s quest for responsible energy generation. Used in households, commercial facilities, and power stations across the globe, they are also a vital source of energy for solar powered yachts. With significant progress made over the last years, photovoltaic technology has emerged as the natural energy source with the most exciting growth potential.

Thanks to photovoltaic cells, solar panels absorb sun radiation to generate direct current (DC). When sunlight reaches a solar cell, it causes silicon electrons to move. This motion will start the flow of electricity that is captured by wires and directed to an inverter. Inverter technology is then used to convert it to alternating current (AC) ready to power household appliances.

The solar power systems on solar powered yachts usually consist of solar panels, batteries, charge controllers and inverters. While batteries store the energy obtained from the solar panels, charge controllers prevent batteries from overcharging. Solar catamarans with house appliances on board will usually need to convert the DC energy into AC with the help of an inverter.

Sunreef Yachts produces solar panels in-house and uses a new (patent-pending) technology to integrate them within structural components. The panels are made of the industry’s most efficient cells with a peak performance of 24%.

Thanks to the solar cells’ outstanding flexibility, Sunreef Yachts’ solar panels can be mounted on any surface of the solar powered yacht. As a result, they are integrated with various areas on board, such as hull sides, mast, superstructure, bimini roof or bow terrace to maximize energy generation.

With a thickness below 1mm and weighing around 1,8 kg per square meter (average solar panels will weigh between 8 and 15 kg per square meter), they are one of the lightest solar power systems in the world. In addition, tests have proven that thanks to their advanced integration technique, Sunreef Yachts solar panels have a very high resistance to shock and abrasion. This allows them to be used on any surface, including hull sides.

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Timeless design meets state-of-the-art technology

More spacious, bolder with premium levels of elegance and comfort. The 80 Series combines our state-of-the-art solar electric drivetrain with unmatched refinement. Her timeless exterior and modern interior features bespoke design by none other than renown Italian yacht designer Marco Casali. Highly advanced hydrodynamics make for an incredibly smooth cruising experience. She can be either configured with a flybridge or as a 3-deck version and can easily accomodate additional crew.

Specification

Deck options, silent 8o 3-deck open.

A complete third deck instead of the flybridge provides a total 84 m² of sky lounge space. The open sides create an outdoor ambience which offers a perfect mixture of sun and shade for relaxing owners and guests. Of course, the open third deck can be customized towards the owner´s needs.

Silent 8O 3-Deck Closed

The closed 3-deck version features an owner’s suite with a private 41 m² aft terrace. Those who value sharing their experiences on board can opt for an indoor lounge instead. It is comprised of a 39 m² dining area, fully equipped with a bar and galley, while still maintaining the same terrace in the aft.

Silent 8O Flybridge

Just as the 60 Series, the 80 Series can also be configured with a retractable flybridge. With 53 m² of space, the flybridge version already offers plenty of room and is equipped with a dedicated helm station to steer the yacht while enjoying the 360° view.

3-Deck Open

3-Deck Closed

Version 1 (4+2 Cabins)

Version 2 (4+2 Cabins)

Solar-electric yachting advantages

Unlimited range, noiseless cruising, zero emission, minimal maintenance, powertrains, 8o series highlights.

Tender garage

In the aft of the portside hull, the staircase can be raised to reveal a fully enclosed tender garage. It fits tenders with a maximum length of up to 5.20 m, such as the Silent Tender 520, and has a direct charging point to recharge electric tenders with energy produced by the yacht.

Largest salon area

When compared to other catamarans of similar size, the 52 m² salon of the 80 Series leads with the largest amount of interior space. This creates a lounge like ambiance which offers all the necessities such as a fully equipped galley to enjoy your stay on board.

Aft storages

Inside the bridgedeck there is a large storage for water toys. Additionally, in the starboard side there is another storage compartment for diving gear, bicycles and motorbikes which can be accessed through hydraulically liftable stairs from the aft.

Owner'suite

The choice of an owner’s suite on the 3rd deck adds to the exclusive appeal of the Silent 80. With the entire deck measuring 80 m², it comes with an en-suite bathroom and a private terrace in the aft offering direct access to the sunbed.

If you would like to enquire about this electric yacht and get in touch with a member of our team, please click on the button below.

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New Silent Yachts For Sale

Silent yachts are the industry leader in ocean-going production yachts that are completely solar sustainable and powered by solar energy. seaworthy, luxurious, and built to impeccable standards, silent yachts are already desirable without its solar capabilities. with the abundance of solar panels on board each boat, every silent yachts model is able to cruise for 100 nautical miles in complete silence. even while at anchor, the solar-powered generators keep the yacht powered quietly for an unprecedented boating experience. enjoy all the benefits of a power catamaran with the addition of solar energy..

Silent Yachts

Silent Yachts 80

Silent Yachts 55

Speak To A Silent Yachts Sales Professional

Silent Yachts offer an environmentally conscious choice when it comes to owning a yacht. Silent Yachts currently offers three solar-powered power catamaran models including the Silent 55, Silent 64, and Silent 80. United Yacht Sales is proud to be the U.S. distributor for Silent Yachts and can assist you in your search for the world's first solar-powered yacht. For more information, please contact United Yacht broker Darren Sell at (561) 351-7333 or by email at [email protected] . 

Where are Silent Yachts built?

Silent Yachts are built through two different shipyards depending on the model. The Silent 55 is built at the world-class shipyard of Mazarin German Yachts which also has a production site located in China. For over 70 years, Mazarin has been a leader in quality yacht construction with over 400 yachts delivered. Mazarin are experts in innovative construction processes that are able to produce light weight yachts.

The Silent 64 and Silent 80 are produced at the Italian-based shipyard Consorzio Navale which is a prestigous consoritum of builders and sub-contractors in the industry. The group has serviced many of the major Italian yacht brands such as Ferretti Yachts and Riva Yachts . Additionally, the Silent Yachts 80 features styling and design by Marco Casali and naval architecture by Insenaval.

Are Silent Yachts really completely solar-powered?

The short answer is yes. Owners can choose to go 100% solar-powered or install diesel engines should higher speeds want to be achieved over longer distances. Silent Yachts can cruise up to 100 miles per day by power acquired through its solar panels. Every day the solar panels are able to generate more power than the total consumption needed for propulsion at cruising speeds plus powering all of the appliances on board. 

How does the solar power work? 

The Silent Yachts power system feeds the electric propulsion of the power cat and all of the energy it needs to run the A/C, refrigerators, and other household appliances. Light-weight lithium batteries provide an ample amount of energy for everything on board. The lithium batteries used in Silent Yachts are the most expensive ones on the market, but also the most reliable, safe, and have the longest life span.

Solar panels are integrated to the roof of the flybridge hardtop sections instead of just being bolted on top, resulting in no wind load or resistance againest them. Below is a video explaining how the system functions and operates back when Silent Yachts were originally called "Solar Wave":

Who is the team behind Silent Yachts?

Heike and Michael Kohler have sent almost their entire lives on a boat. After more than two decades of using various boats, cruisers, and sailboats on multiple oceans, they became dedicated to finding a better energy source for the propulsion of yachts. Between the years of 2005 and 2009, Heike and Michael tested a number of a multitude of various alternative energy sources. In 2009, SolarWave 46 was launched as a proof of concept for their design. While there are many boats and yachts built that use solar power in some fashion, the Solarwave 46 was the first ocean-going yacht to use solar energy to power everything on board from engines to appliances.

What else is different about how Silent Yachts are built?

Certainly the solar-powered engines and generators are the distinguishing characteristic, but there are a lot of other features that make each Silent Yacht unique. For example, the molds were created using a CNC-milling machine that is able to contruct particular shapes for an optimized design. The materials used in the hull include a carbon compositie that is then resin-infused for a light-weight, but very strong platform. Every hull is fully insulated and the long-term durability is exceptional thanks to the high-quality resin used in the infusion process.

What propulsion systems are recommended by Silent Yachts?

Silent Yachts recommends the 2 x 135 engines as the best solution. If the owner is making frequest trips from Point A to B (Say Miami to the Bahamas for example) the faster hybrid is recommended. The main differentiator here is cruising speed. If the owner is living on the yacht for an extended period of time, rarely pushes the engines to top speeds, and stays below 12 knots, then the E-Power is recommended.

When the generator is running, does the 100Kw go to charging the batteries (which run the 250 Kw e-Motors) or directly to the e-Motors?

All of the enery consumers and producers are connected to the bus bar. If there happens to be more power produced than consumed, the excess power goes to re-charge the batteries. If for some reason more power is required than what is produced, the needed power comes from the lithium batteries.

What is the sustained speed if both 100 Kw generators are running?

This answer really depends upon sea condition and the weight of the boat (for example components, additional equipment, water toys, etc.). The sustained speed on average though is between 12 and 14 knots, 10 knots with one generator running. It is possible to cruise at 10 knots without a generator running when using the Solar E-Power.

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Recharge at Sea: Solar Catamarans Harness Sun-Powered Serenity

Just as a residential solar system makes a house independent of an electricity grid, a marine solar panel makes a yacht independent of a fossil fuel powered generator. Catamarans boosted by solar power systems are increasingly in demand in today’s day and age for their increased energy efficiency and reduced environmental impact.

Here is everything you should know about solar catamarans from Sunreef Yachts Eco :

An Introduction to Solar Catamarans

Derived from natural sources, renewable energy is replenished at a far higher rate than consumed. Of these, solar energy is the most abundant renewable energy resource on Earth that may even be harnessed during cloudy weathers. Additionally, because sunlight remains omnipresent, powering a watercraft with solar energy is a fitting concept.

Before we continue exploring the subject of solar catamarans, let us focus on the architecture. The twin hull structure of catamarans translates into a large beam, which provides ample space for solar panels installation. To top it off, catamarans have a fairly shallow draft that produces little to no drag, making them exceptionally energy efficient .

Marine solar panels are currently gaining substantial popularity amongst catamaran designers and manufacturers as a medium of supplying clean energy via a reliable source. Sunreef Yachts Eco is a pioneer in solar catamarans as we believe that the incorporation of a solar power system into yachts births an environmentally friendly yachting solution with a significantly reduced carbon footprint.

The Benefits of Solar Catamarans

The ocean is home to the largest continuous ecosystems; unfortunately, it also remains the most sensitive. Millions of people across the globe indulge in recreational marina and boating activities leaving behind pollution in their wake.

Here are three ways in which solar catamarans rectify commonly occurring hazards for the greater good of the environment:

1. Fuel (oil or gasoline) spills and the discharge of combusted fuels from engines readily contaminates water surrounding the marinas. This aggravates toxicity levels in water, resulting in increased pollutant concentrations in aquatic organisms and sediments.

For illustration, coral reefs, which are a vital source of nitrogen and nutrients for marine food chains and provide shelter for over one million aquatic species, are nearing extinction due to water pollution. Installing solar panels would, without a doubt, decrease the dependency of all types of watercrafts on non-renewable energy sources, i.e., fossil fuels, for operations and increase energy efficiency.

2. Noise from moving gas-powered ships cuts straight to the sea floor and back. These acoustic vibrations transmitting end-to-end affect marine animals to a great extent. Research suggests that human-caused noises result in disrupted behaviours, increased stress, and impaired feeding in marine life, leading to injury and death. Solar catamarans are far quieter than their combustion-driven counterparts; thus, they maintain the oceanic silence vital for the marine life as it enables communication and continuous growth.

3. The elimination of fuels also makes solar yachts more affordable to run and maintain in the long haul. In comparison to fuel powered generators, solar catamarans produce electricity at a lower cost since solar panels obtain power via the sunlight, a renewable source of energy that is present in abundance. But even if your catamaran utilizes both fuel and solar power, you are still to enjoy significant savings on fuel.   

Why Power A Boat with Solar Panels   

Apart from the obvious environmental factors, solar panels fulfil an important criterion for the oceangoing voyagers who do not wish to be left stranded far from land with a dead battery: unlimited backup power.   

On a typical sailing day, there is ample sunlight to ensure the backup battery restores enough power to generate electricity that keeps motors, electrical systems, and onboard appliances running. An added benefit of solar panels is that they continue to generate power even when the catamaran is at a standstill. This energy is stored in batteries for later use.   

Furthermore, unlike gas powered generators, solar catamarans do not produce excessive heat, are quieter, and experience little to no vibrations. This allows boat trips to remain pleasant for sailors and vacationers.   

Sunreef Yachts combines luxury with sustainability to offer noiseless, vibration-free, and fume-free cruising experiences. Launched under the Sunreef Yachts Eco flag, our sailing and motor yachts are powered using inhouse engineered solar panels that are fully integrated within their composite structure for optimal results. However, an additional asset for sailing solar catamarans remains the ability to combine eco motoring with wind propulsion with the use of high-performance kites.   

The Mechanism of the Solar Power System   

Classification of solar panels   .

There are various kinds of solar panels available for marine boats: adjustable panels, standard panels, and high-energy thin-film panels. While some may argue that having a portable solar panel makes it easier to relocate to where the sun shines the brightest, permanently mounted panels remain ready to go throughout the day.

Despite their long life, standard panels often fail to find a place in the marine industry as they compromise the space availability onboard. Hence, high-energy thin-film panels emerge as winners due to their ability of being permanently embedded on the solar catamaran’s bodywork without restricting living space.

The research and development team at Sunreef Yachts Eco developed the industry’s first composite integrated photovoltaic technology to produce highly efficient, shock resistant, flexible, and ultra-thin solar panels. This in-house engineered solar power system was recognized as a winner of the German Design Award 2022 in the category of Excellent Product Design: Eco Design .

Each solar panel consists of photovoltaic cells, compromising of a positive and negative layer for creating an electrical field. These are made of singly-crystal silicon, a semiconductor that absorbs the radiations of the sun to produce electrical power via the photovoltaic effect. For better understanding: the photovoltaic effect is the process of converting photons (a particle of light) to voltage.

Technical Specifications of Solar Panels

While the average solar panels’ weight lies between 8 to 15 kilograms per square meter, Sunreef Yachts Eco’s solar cells have a thickness below one millimetre and weigh only 1.8 kilograms per square meter. This makes Sunreef Yachts Eco the lightest marine solar power system producer in the solar catamaran market.

Each of the solar cells administered into the Sunreef solar catamarans are ISO 9001:2015 certified and offer a peak performance of ±24 percent, this is 25 to 30 percent more power compared to conventional cells. Despite this, these solar cells do not heat up excessively when receiving sunlight.

Integration Into the Solar Catamarans Structure

The orientation of the sun should be as such as that it hits the solar panels at a 90° angle for best performance. However, with the Earth rotating around its axis to produce a 24-hour day, it is non-viable to ensure the perfect angle throughout the day.

What is more is that the amount of energy produced may also differ depending on external factors, such as a building preventing direct sunlight from hitting the solar panels or light experiencing diffraction from the waterbody before contact. For this reason, it is best to invest in high-efficiency solar cells that generate maximum energy even from limited number of active panels.

Sunreef Yachts Eco makes the most of its solar catamarans’ space availability by spreading its “solar skin” across the hulls, mast, superstructure, bow terrace and bimini roof. Due to this arrangement, the solar panels receive ample sunlight at desired angles from early morning to late afternoon.

At the same time, light rays bouncing off the surface of water to the solar panels, in a process called reflection, also helps generate electricity. These superior performance solar panels possess great strength and durability to survive adverse conditions, year after year.

Generation of Electricity on Solar Catamarans

The crystals in marine solar cells are treated to enable the movement of electrons to generate an electric current. These silicon electrons activate only when in direct contact with sunrays. Instantaneously they start producing direct current (or DC) charges, which is captured by wires and stored in the batteries as energy.

At this point, a charge controller is employed as a regulator for the energy to transfer from the solar panels to the battery. It not only manages the energy load received by the battery, but also prolongs the battery life and performance by ensuring the battery is not overcharged or overloaded. Solar catamarans deploy multiple charge controllers depending on the energy produced.

While the current may be supplied directly to support the electrical demands of the catamaran, if the appliances demand alternating current (or AC), an inverter is added to the cycle to convert the DC to AC first.

Solar Catamarans in Action

But how much energy is enough energy? Working out a catamarans’ energy requirements requires summing up the energy consumed by each device onboard in watt-hours. For better understanding: energy is power accumulated over time, so if power is calculated in watts, energy is watt-hours.

Hence, the first step of installing solar panels dictates an extensive energy assessment of the watercraft. This requires checking the labels of every individual appliance onboard for its typical amp hours and volts used, be it the fridge, fan, or lightbulb. A battery monitor can also help measure energy consumed more accurately.

Depending on the size of the catamaran and the energy consumed, the solar panels size and wattage of power can be precisely determined. Multiple solar panels may be wired together to form a solar array for maximum energy generation. Aiming to fulfil the power needs of your catamaran with solar panels allows you to enjoy a quiet, peaceful anchorage.

Overcoming The Challenges of Solar Catamarans

While yacht solar panels resolve the problem for keeping the batteries topped up without running the generator, solar power systems are faced with challenges of their own. For starters, the harsh weather incurred at sea and saltwater splashing on or immersing the panels accounts for much damage.

However, technological advancements have enabled solar panels to withstand most of these environmental adversities. To illustrate, the installation and electronics linked with solar power systems have now become more resistant to short circuits and corrosion.

Sunreef Yachts Eco employs a unique photovoltaic integration technique in solar catamarans to give the panels extreme resistance to shock and abrasion. Even if the cell eventually cracks, the solid metal foundation remains intact to maintain a high-power output. Furthermore, these solar panels experience no light-induced degradation, no temperature coefficient, and favourable low-light and broad spectral response.

Likewise, the constrains of surface area for marine solar PVs have been addressed with the ability to manufacture customized solar panels. For instance, Sunreef Yachts Eco uses the lightest solar cells in the industry which offer unparalleled flexibility for placement on rounded surfaces of the solar catamaran while others break under pressure. Here solar panels are integrated vertically (on hull sides, flybridge sides, and mast) and horizontally (on front flybridge and bimini) to maximize energy generation.

While the Sunreef Yachts Eco’s solar panel system has a protracted life expectancy, any panels sustaining damage, due to adverse conditions at sea or other geographical circumstances, can easily be replaced. However, it is proven repeatedly that their performance remains unaltered over extended periods of time.

Efficiency of Solar Catamarans Vs. Diesel Yachts

Solar panels make for an ideal energy provider as they ensure the batteries always have power. This makes solar catamarans more self-sustainable and cost efficient to run in comparison to gas-powered ones. Additionally, fewer moving parts in solar catamarans call for significantly lesser maintenance in comparison to diesel yachts.

Boats of all shapes, sizes, and types (sail or motor) can be powered via solar energy to run all onboard appliances on battery. Apart from fulfilling the watercrafts’ day to day electrical usage, utilizing a renewable source of energy extends the durability and reliability of the catamaran.

But most importantly, a solar powered yacht compared to a standard diesel yacht has a significantly reduced carbon footprint. Ideally, with the use of solar power generation on catamarans, you would save 108.5kg of CO2 emissions per day or 39.6 metric tonnes annually.

Why Invest in A Solar Catamaran?

The wind in your hair, the sun on your face, and the sweet smell of the sea are one of the many joys of sailing. However, as an ocean enthusiast, it is crucial to calculate your impact on the environment. On average, the Sunreef Yachts Eco’s solar catamarans account for substantial electricity generation of up to 30 kWh, promoting a positive green footprint.

Today, solar catamarans are trending among yacht owners and shipbuilders as a clean medium to increase energy efficiency and reduce carbon emissions. Additionally, staying true to its legacy of yacht innovation and evolution, Sunreef Yachts Eco continues to work on advancements to its solar panels for improved performance, efficiency, and durability.

Evaluating the Sunreef Yachts Eco Solar Catamarans

Using advanced technology, Sunreef Yachts Eco has engineered ultra-thin, flexible solar panels with the best performance on the market. They are seven times lighter than the average solar power system, enabling them to be fully integrated into the composite structures, including curved surfaces.

The more surface area covered, the more electricity generated. The 80 Sunreef Power incorporates 200 square meters of solar panels (weighing about 360 kilograms) that deliver an astounding 40 kilowatts peak per hour. This setup alone produces solar energy equalling to two generators weighing 800 kilograms altogether.

Hence proven that Sunreef Yachts Eco optimized marine solar panel system outperforms a diesel generator both by weight and performance. Additionally, at reduced speeds, the Sunreef 80 Eco remains fully autonomous, running solely on solar power.

In light of sustainable yachting, Sunreef Yachts Eco has committed to launch over 40 models of its solar catamarans by the end of 2024; this includes a wide selection of sailing yachts, power yachts, and superyachts. Furthermore, Sunreef Yachts has begun commissioning a new range of technologically advanced hybrid ecospeeders, called the Sunreef ULTIMA , that would further extend their solar catamarans line up.

Future Innovations in Solar Catamarans

Despite the distinctive competency of Sunreef Yachts Eco in solar catamarans, the journey of innovation does not come to a halt. To further reduce our carbon footprint, we are undergoing ground-breaking research to redirect excess heat secured from direct sunlight on solar panels to the boilers of our solar catamarans.

Furthermore, Sunreef Yachts Eco is currently developing a concept of an all-new 90 feet sustainable sailing superyacht , called ‘The Zero Cat’ . Apart from sporting a solar power system, this catamaran will use a zero-emission generator to convert methanol to clean hydrogen for unlimited autonomy and greater self-sufficiency.

Frequently Asked Questions

• Why are solar catamarans favorable?  Because sunlight remains omnipresent, solar catamarans discern as a greener, cost efficient, and self-sustaining yachting solution . The environmentally friendly passenger conveyance from Sunreef Yachts Eco is consciously built to counter air, water, and sound pollution.
• What is a solar catamaran? A solar catamaran is a twin-hulled vessel powered by solar panels, harnessing sunlight to drive its propulsion and onboard systems, offering an eco-friendly alternative to traditional fossil fuel-powered boats. Powered using inhouse engineered solar panels, solar catamarans designed and manufactured by Sunreef Yachts Eco encourage a positive green footprint at sea. 
• Do solar catamarans exist? Launched under the Sunreef Yachts Eco flag, our sailing and motor yachts are powered using inhouse engineered solar panels that are fully integrated within their composite structure for optimal results. The Polish designer and manufacturer has also committed to launch 40 additional models of its solar catamarans in 2024.
• Are there any solar powered yachts? With an increasing demand for solar catamarans with increased energy efficiency and reduced environmental impact, Sunreef Yachts Eco has put to sea several variants of its sailing and power catamarans such as the Sunreef 60 Eco , Sunreef 70 Eco , Sunreef 80 Eco , and 80 Sunreef Power Eco
• What are the advantages of solar catamarans? The installation of solar panels reduces a watercrafts sole dependency on non-renewable energy sources for operations. In comparison to their combustion-driven counterparts, solar catamarans offer noiseless, vibration-free, and fume-free cruising experiences.
• How much is a solar-powered catamaran? With Sunreef Yachts Eco’s philosophy of promoting clean green yachting, the company has released a new range of solar catamarans , the Sunreef ULTIMA , with prices starting as low as €2M* for the 44 ULTIMA ECO . *Please note that all prices listed are subject to change at any time without prior notice.

ULTIMA RANGE

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Solar-Powered Yachts Are Taking Over. Here’s Why That’s a Good Thing.

Diesel-powered engines are getting some healthy competition., michael verdon, michael verdon's most recent stories.

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In 2005, Michael Köhler turned away from the diesel engines that had been powering his boats for 23 years and went instead with solar power, an idea that seemed laughable, given the technology’s limitations at the time. But after five years of testing and development, Köhler’s Solarwave 46 became the world’s first solar-powered yacht.

Since then, his Silent Yachts brand has become larger and ever-more luxurious, running bow-to-bow with traditional motoryachts. The new 80-foot tri-deck has a spacious salon and six staterooms, six-and-a-half-foot ceilings and unlimited cruising potential, since the lithium-ion batteries powering the 250 kw electric motors recharge on the go (and for free) courtesy of the yacht’s 1,227 square feet of solar panels. And the benefits extend beyond minimal emissions and engine vibration. “We have more living space than competitors,” Köhler says, “since electric motors require less space than diesel engines.”

Very different vessels are using electric propulsion to minimize noise and lower emissions, like Super Air’s Nautique GS22E.  Super Air

The solar niche is small but growing, with new entrants like Serenity Yachts and the BYD Group. These power yachts have cruising speeds of 8 knots and top speeds of up to 20 knots, though they’ll burn through battery packs quickly at that rate. Therein lies the design dilemma of battery-powered boats: Do builders prioritize range or velocity?

Correct Craft ’s new GS22E wakesurf boat found a way to twist battery limitations to its advantage. “We’ve designed the most energy-dense battery system for where a combustion engine typically goes,” says Sean Marrero, president of Watershed Innovation, which developed the GS22E’s Ingenity electric propulsion system. Tailored for hour-long sessions, owners can wakesurf in the morning, then recharge the battery so it’s ready after work. “It doesn’t run like a Tesla,” says Marrero, “but rather it mirrors the wakesurf experience with its stern dug into the water—minus the noise and emissions.” Other builders are rumored to have electric towboats in the works.

Feadship ‘s 273-foot Savannah.  Feadship

In the superyacht segment, Feadship director Henk de Vries would like to see every new yacht leaving his Dutch yard equipped with hybrid propulsion by 2025. De Vries is so serious about this mission that Feadship will absorb the extra cost over conventional propulsion, currently amounting to several million dollars, of those electric drives. So far, two boats have chosen hybrid power: the 273-foot Savannah , launched in 2015, and Feadship’s largest build, the 361-foot Anna, delivered two years ago. A third yacht launched that same year, the 287-foot Lonian , is also “heavily hybrid,” de Vries says.

“When we built Savannah , a hybrid with the [battery] equivalent of many Teslas in the engine room, we also invented the classification rules for these yachts,” says de Vries. “Even though the project was successful, the superyacht world was slow to adapt. I want to get to the point where one owner says to another, ‘Oh, your boat still burns fossil fuel?’ That will help create the mindset.”

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Aquanima 40 series

Azura marine, this $500,000 electric yacht can cross oceans on just battery and solar power.

Singapore-based Azura Marine unveiled a new $500,000 electric yacht that they claim can complete “non-stop ocean voyages powered only by sunlight.”

The electrification of transport is slowly spreading into maritime transport.

While the focus has been commercial vehicles like ferries, it is also reaching leisure and personal vessels.

Azura Marine is the latest to enter the space with its first solar-powered catamaran yacht, the Aquanima 40 series, unveiled earlier this month in Bali, Indonesia.

The company describes the electric vessel:

“She is a unique 4 cabin, 8 guest yacht designed for extended cruising without any need for fossil fuels or refuelling stops of any nature. The Aquanima 40 solar-powered catamarans are also equipped with a 56 m2 rain catchment system, water maker and air conditioning water recovery – rendering water supply stops unnecessary too.”

Here are a few pictures of the Aquanima 40 series solar yacht:

Azura Marine claims that the vessel can continuously cruise thanks to its large 10 kW solar power system and 60 kWh battery pack.

Here are some of the specs of the Aquanima 40 series:

• LOA 13,25 m
• Draft 65 cm
• Propulsion Power: 2 x 10 kW
• Solar Power: 10 kW
• Main Battery Bank Capacity: 60 kWh

The company writes about the capacity of the electric vessel:

“For the owner, this means limitless cruising with no fuel costs, no noise or vibration, no smells, no polluting emissions and no disturbance of marine life.  The electric motors are virtually maintenance-free with only a couple of low-cost bearings to be replaced at 20,000 hours (more than a typical lifetime usage of a yacht).”

Here are some pictures from inside the electric yacht:

The company lists several amenities available onboard its new electric vessel:

“The yacht offers all the comfort to be expected of a modern cruiser with air conditioning, fully equipped galley including ice maker, hob and sink.  On this version, the bathroom and toilet is on main deck for greater ease of access as this vessel is strongly oriented towards enjoying the outdoors, exploring hidden bays with the electric dinghy or diving on pristine reefs. Onboard Solar Eclipse, all water is self-produced, including fresh and drinking water, thanks to the yacht’s water-maker, air conditioning water recovery system and gigantic rain water collecting solar roof.  She features a high quality marine sound system and all round WIFI connectivity.”

Azura Marine Co-Founder and CEO Julien Mélot commented on the launch of the new electric vessel:

“it was an enormous thrill to launch the yacht last week and undertake her first few miles at sea.  The yacht met all our expectations and while the design makes for near silent operation with exceptional responsiveness, it was incredible to actually experience it  – and all in the knowledge that we were not producing any harmful pollution or emissions.  With some strong winds and a very tight to enter marina berth, we were delighted by how easy the yacht was to manoeuvre.  We simply cannot wait to take her out on her maiden voyage.”

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Yachting Monthly

• Digital edition

Sailing with solar power: A practical guide

• Duncan Kent
• November 13, 2020

The latest solar technology makes self-sufficient cruising much more achievable. Duncan Kent gives the lowdown on everything you need to get your boat sorted

SOLAR POWER ON BOARD

Solar power is fast becoming the most popular and economic method of keeping the batteries charged on a boat.

Particularly now that the efficiency of photovoltaic (PV) panels, charge controllers and batteries is improving every day.

Furthermore, the latest technology in regulators and charge controllers has brought about a noticeable increase in useable power output, so the problems of shading and non-alignment can be compensated for more easily.

Not only has PV equipment become more efficient and cost-effective, but many of the modern devices we want to use on a boat have become less power hungry.

This means it is now far easier to provide your entire yacht’s electrical needs, both 220Vac and 12/24Vdc, from natural energy resources – particularly solar power, even if you are planning on a fully electric boat .

Thinking carefully about how much power you need and how much your boat can accommodate is key to planning a solar array. Credit: Graham Snook

WHAT DO YOU NEED?

For instance, a boat with two new, good quality, deep-cycle house batteries of 100Ah each would supply 100Ah of energy to consume between charges, if you only use the recommended 50% of available charge between each charge cycle to protect the batteries.

From this you could run:

• a modern 12Vdc fridge (approx. 1.5Ah, or 36Ah over 24hrs),
• all LED lighting (say 20Ah per day),
• various small device chargers (20Ah)
• and a number of other items such as water pumps, TVs and stereos (25Ah/day)
• Totalling around 100Ah.
• For this you’d need 400W of solar capacity.

Of course, if you like to run a lot of AC devices off-grid such as hair dryers, microwaves, toasters and the like, then you’re going to need a DC/ AC inverter, which will take you to another level in power consumption terms.

But even then, with careful planning, solar could provide a large portion of the power you need before resorting to engine charging or a generator.

THE AVAILABLE SPACE

In practical terms, a modern 40ft monohull would have the space for around 1,200W of PV panels (cockpit arch, sprayhood top, deck), maybe 1,500W with the addition of a few portable panels for use at anchor.

The 1,200W of fixed position solar array could produce around 360Ah on a sunny summer’s day (zero shading) or more likely 250Ah on the average UK summer’s day.

So that’s enough for your 100Ah general DC consumption plus another 150Ah of AC consumption via the inverter.

Of course, to do this you’ll most likely need to increase your battery capacity to around 400-500Ah for maximum flexibility (you’ll need to store as much as possible during daylight hours), a typical figure for a 40-50ft offshore cruising yacht these days.

Get your solar charging right and you may never need to hook up to shore power

Typical daily inverter loads for a cruising yacht off grid might be:

• induction cooking plate (20min) 60Ah
• microwave (15min) 30Ah
• coffee maker (20mins) 25Ah
• hair dryer (5min) 15Ah
• laptop charger (2h) 10Ah
• or around 140Ah in total.

The trick is to monitor the batteries’ state of charge (SOC) at all times and vary your use of the inverter to suit.

For example, you might want to cook supper mid-afternoon, when solar is in abundance, and then reheat it in the evening when you want to eat it.

In some cases, when you’re cruising in warm climates such as the Med, you might end up with excess charge from your solar panels .

In this situation, many long-term cruisers devise a method of ‘dumping’ the extra energy by heating water for showers.

Do bear in mind if you’re planning to live aboard full time , then it’ll be a whole different story on cloudy days and during the winter, when inverter use might need to be knocked on the head entirely.

Continues below…

Eco friendly sailing: Best practice for green yachting

How easy is it to go eco friendly sailing? We look at the steps cruisers can take to minimise their…

How and where to go wild cruising in the UK

Planning to spend the night away from crowded waters can 
be truly rewarding but preparation is essential before you go…

Solar-powered boat crosses Atlantic

Then heads to UN climate conference

POWER DISCREPANCIES

There’s often confusion as to how much power you can harvest from a solar installation.

A PV panel is nearly always advertised stating its theoretical peak output power (Pw).

But in reality, on a yacht where there are limited areas in which to mount them, they will more likely produce a maximum of 60% of their peak output if mounted horizontally, increasing to 80% if tilted towards the sun and regularly adjusted.

The latter is rarely achievable on a boat, however, as even at anchor it can swing through an arc of 180° in wind or tidal shifts .

Flexible panels can be mounted on sprayhoods or awnings to add power when it’s needed at anchor or in harbour

INSTALLATION

Having trawled through hundreds of ‘deals’ to get the best price on the most efficient panels you can afford you now need to know how to install them to best fulfill your energy generation needs.

The output, even from the highest quality photo-voltaic array, will only be as good as the installation itself.

So following our guidelines should ensure you extract every last drop of energy from your investment.

PANEL MOUNTING

Sailing boats are not the ideal structure on which to mount wide, flat PV panels.

So before you go ahead and purchase what looks like the biggest and best, take a few minutes to decide on exactly where you can mount them, as this will affect what size and type of panels you should buy.

In many cases the first choice would be on an arch, davits or gantry aft, especially if you already have, or plan to fit one.

Dinghy davits, particularly on multihulls, can support a huge solar capacity

These allow a solid metal framework to be constructed that will be strong enough to take the heavier, more productive rigid PV panels.

You can also build in some form of adjuster to the framework that will allow the panels to be orientated towards the sun for the best performance.

With luck (or careful planning) a gantry will also keep them aft of the boom, thereby eliminating loss of output caused by boom shading.

The next most popular position for mounting the panels is on a cockpit sprayhood or bimini, although this will often mean using the flexible or semi-flexible panels, which are generally less efficient than the rigid ones for the same area.

ELEVATED MOUNTING

Alternatively, there are kits available for mounting panels onto lifelines, which can allow their elevation to be manually adjusted to a certain degree.

Pole-mounted panels can be used for maximum adjustability

Finally, panels can be fitted directly onto the deck by either gluing them down using mastic or attaching them onto a rigid support frame.

Once again you will probably need to use semi-flexible panels – especially if the deck surface is curved.

Rigid, glass-coated panels will obviously not be suitable for deck mounting in an area that is frequently walked over.

Don’t be tempted to drill through the panels, even along the edges, as this will invalidate the warranty and possibly damage the panel.

With solid panels, the ability to adjust the angle can add significantly to output

It might seem obvious, but the key to an efficient system is to avoid shading wherever possible.

It’s no good fitting expensive, high-efficiency PVs right under the boom as they’ll perform little better than the cheaper types.

Saying that, in good quality panels each cell will be isolated from the next by a series of diodes (one-way electrical valves), so that if one cell is shaded at least it won’t drag down the other cells within the same panel.

Older panels often didn’t have these, so the slightest partial shading caused the output of the entire panel to cease.

OVERHEATING

Another important factor that is often ignored when installing the panels is that of overheating.

If a PV panel gets too hot, which is quite likely if mounted directly onto a flat surface without an air gap behind, its output will drop quite noticeably.

To allow for some air circulation behind the panels it’s best to apply mastic adhesive in numerous large dabs.

This is best achieved by placing wooden spacer strips between the dabs until the mastic has completely cured, after which the spacers can be removed.

You might need some form of trim around one or more of the outside edges, though, if they are positioned where sheets and other lines might get caught under them.

Raising the panels up will also help water to drain off and thereby helping to avoid possible delamination from sitting in water for too long.

CHARGE CONTROL

A PV module cannot supply an electrical device directly due to the changeability of the sunlight, which in turns varies the current it can produce.

Therefore, it has to be connected to a battery, which stores and smooths its output.

Whatever the size of your solar array you will need to fit a regulator, or charge controller as they are now more commonly known, to the system in order to control the output and to help extract as much power from the panels as possible.

There are two types of PV charge controller.

The older designs, called Pulse Width Modulation (PWM) types, were fairly basic voltage regulators and simply output volts at just above battery level.

The latest controllers use Multi Power Point Tracking (MPPT) technology and can accept much higher input voltages (up to 240Vdc).

MPPT controllers can be up to 30% more efficient as they use the peak output of the panels to charge the batteries, even compensating for partial shading.

BEWARE FAKE GEAR

If you buy online do be careful to ensure you’re getting what you pay for.

There are a huge number of fake MPPTs out there, which are simply the much cheaper PWM dressed up with fake labels.

It’s hard to tell which is which, but the old adage of ‘if it looks too good to be true, it usually is’ makes good sense.

MPPT controllers are usually bigger and heavier than PWMs, but if in doubt call or email the supplier to discuss the pros and cons of their kit before buying.

If they’re not happy to chat and advise you then I would steer clear of their gear.

Some good MPPTs are made in China, but unless they have a UK supplier, I wouldn’t bother with them as you’ll have no follow-up advice.

To calculate what size controller you need simply divide the panel’s peak power in Watts (Wp) by the battery voltage, which will give you the maximum current (Amps) they could theoretically supply.

For example 240W/12V = 20A. Although it’s unlikely you’ll ever get near the peak output from any PV panel, it’s best to go for the maximum possible.

Induction cooking is now a reality on board, even without shore power

PV panels come with a short length of cable, usually around 1m long.

Some are supplied with MC4 connectors already attached but most only provide bare wires.

The latter can be easily extended using proper waterproof connections but thought must be given as to the current rating and voltage drop (usually max 3%) for the size of cable you intend to use.

If in doubt, bigger is better!

Panels can sometimes be ordered with the wiring on the back so that the cable can go straight below deck through a hole under the panel.

You may need to fit extra battery capacity if you want to run an inverter from solar charging

SERIES OR PARALLEL?

A commonly asked question is ‘should I wire my PV panels in series or in parallel?’

The simple answer is, if there’s any danger of frequent shading to one or more of the panels then install them in parallel.

If wired in series the shading of a single panel will drag down the output from all of the others in the same series.

PARALLEL IS PREFERRED

Most commonly, multiple panels are wired together in parallel to a single charge controller, with diodes protecting each panel from discharging the others should one become partially shaded.

With the advent of MPPT controllers, however, there can sometimes be a benefit to wiring two or more identical panels into a series bank, thereby presenting a higher voltage to the controller.

It’s worth noting that, like batteries, wiring PV panels in series increases the voltage only – the current capacity of the array remains the same as for a single panel.

‘Where’s the benefit of wiring them in series then?’ you might ask.

Well, the higher the voltage fed into the MPPT, the more consistent it will be with its output, which could, in some cases, prove more efficient than a parallel installation with PWM controllers.

It’s also likely to be necessary if you have a 24V domestic system.

SERIES WIRING

Series wiring is usually only done when the cable runs are long, as it helps negate the voltage drop caused by the resistance of the cable.

While a decent controller will have no problem handling the output from four or even five panels wired in series, it is often inappropriate for sailing yachts as shading just one of the panels will reduce the output of the entire series array.

If you need to do so in order to reduce cable runs then it’s best to split the panels between each side of the boat – a series bank on each side.

If you do this, then you would ideally fit a separate controller to each series PV bank and then connect their outputs together in parallel to the battery bank.

Note, however, that panels wired in series must all be the same types with an equal number of cells per panel.

Furthermore, the charge controller needs to be sized for the total of all panel voltages added together and the current rating of one individual panel.

Differently rated panels can be connected together in parallel but only if each panel has its own controller.

The outputs of the individual controllers can then be joined together to go to the battery bank.

BATTERY BANK QUESTION

Another frequently asked question is ‘Can I connect another charging source to the battery bank while the solar array is charging?’

The answer is yes.

Any decent PV controller will be protected against feedback from other charging sources.

Think carefully about where shade from mast, boom and rigging will fall. Credit: Graham Snook Photography

CABLE SIZE AND CONNECTORS

A frequent cause of reduced output from PV arrays is wiring that is too small.

The resistance of a wire conductor increases in direct proportion to its cross-sectional area, so go as big as is practicable for the least cable loss.

Each panel should be supplied with the correctly sized cables for its own maximum output.

But if you’re combining panels, either in parallel or in series, you will clearly need to rate the single feed cable to suit the maximum current available at theoretical peak solar output and to minimise voltage drop.

Likewise, the cable from the controller to the batteries should be sized to suit the controller’s maximum output current and protected with a fuse.

For outside it’s important to use exterior grade cable, which is double- insulated and UV-proof.

WEATHERPROOF CONNECTORS

And wherever possible use compatible weatherproof connectors (usually MC4) to those found on the panels rather than cutting off the plugs and hard-wiring them.

Field- assembly MC4 plugs are available, so you don’t have to drill large holes in the decks or bulkheads when feeding the cables through.

When joining more than one panel together try to use the approved multiway connectors; not only do they keep the wiring neat and tidy, but they also offer a greater contact area than budget terminal blocks.

If you have to use screw-type connectors make sure to fit proper ferrules to the wire first to avoid any stray wires in the multistrand shorting across the terminals.

When feeding a cable from above to below deck, try to go through an upright bulkhead where possible to minimise ‘pooling’ of water around the access hole.

Also, use a proper watertight deck seal that matches the cable you’re using.

If drilling through a cored deck you need to drill a larger hole first, fill it with epoxy resin and then drill the required size hole through the epoxy to ensure no water gets into the deck core.

Ideally, the charge controller should be mounted no further than 2m from the battery bank.

If you need to go further, you’ll require larger cabling to reduce the voltage drop.

A generous solar array will keep you self- sufficient indefinitely. Credit: Graham Snook Photography

CONTROLLER LOAD TERMINALS

There is often confusion over the ‘load’ output of a charge controller (often depicted by a light bulb) and what can safely be connected to these terminals.

Rarely explained in the manual, the load terminals should be pretty much ignored in a marine installation as the output on these terminals is usually very limited (10A max).

Some attach an LED light to them to indicate the controller is operating, but all your usual electrical loads should remain connected to the batteries with the battery terminals on the controller connected directly to that battery bank via a fuse.

It is possible, though, to control a high-current switching relay in certain conditions.

Parallel installation is more resilient to shading, but a series installation will increase peak charging outputs. A combination of the two offers some of the benefit of both

CIRCUIT MONITORING

Unlike most cheap PWMs, the majority of good quality MPPT charge controllers come with an alphanumeric LCD screen to let you know what is going on.

This can either be a remote display or simply one on the front of the box.

It’s obviously a lot better to have a proper numerical display than to rely on a few flashing LEDs to tell you when something’s not right.

So if your chosen controller doesn’t have one be sure to fit a battery monitor (the shunt type) into your solar circuit between the controller and the batteries.

It doesn’t have to be a very ‘smart’ monitor, just one that can display the voltage and current being supplied by the panels.

For smartphone addicts there are several wifi apps that will do the job remotely on your phone or tablet.

DEVICE PROTECTION

All good quality PV panels feature built-in diode protection between each cell to prevent a shaded cell from dragging down the productive ones.

In addition, there will be internal blocking diodes on the final output to protect the panel from polarity reversal and to ensure that the batteries can’t discharge back into the panel during the night.

The latter can be added externally, the former can’t, so check before you buy.

A fuse, rated just above the maximum current available, should be fitted between each panel and the charge controller.

Another fuse should then be installed between the charge controller’s output and the batteries.

In the case of multiple arrays, this second fuse will be rated higher than the individual panel fuses and should match the maximum current rating of the cable.

With this protection installed other charging devices can be connected in parallel at the battery, meaning the solar can be left connected even when you are hooked up to shore power and the battery charger is operating.

In some circumstances, however, this arrangement can affect the sensing of the battery by the charger, causing it to fall back into float mode.

If this becomes apparent it can be overcome by installing a manual/auto switch to disconnect the solar array when on shore power.

Check the flex of the solar panel is sufficient for your deck

EXCESS POWER DUMPING

A solar charge controller works by disconnecting the supply from the PV panels when the batteries are fully charged.

But for some full-time liveaboards in sunny climates that can be considered a waste, when the excess power could be put to good use – heating water, say.

This is commonly done using an inverter to supply AC power to the heating element.

Alternatively, you can now buy a 12Vdc element for your calorifier (hot water tank) and supply this directly from your battery bank.

Both of these methods would require a voltage sensitive relay (VSR) to disconnect the element should the battery voltage drop below a pre-set level.

Don’t expect boiling hot water, as there will probably only be enough spare power to take the chill off it before your battery bank reaches its lower threshold voltage.

A 600W/12V element will draw some 50A, from the batteries, whereas a 1kW AC element run through an inverter will need close to 100A.

A small, semi-flexible panel will be sufficient for keeping batteries trickle charged, but not for heavy use

RIGID, FLEXIBLE, OR SEMI FLEXIBLE?

Despite massive recent improvements in semi-flexible panels in recent years, the solid glass panels still offer a higher power density.

That said, they are heavier, more awkward to mount and can’t be walked on, so unless you have a dedicated gantry aft, you’re better off choosing the more rugged semi-flexibles.

Modules incorporating monocrystalline cells also have a better output than those with polycrystalline cells (that’s cells made from a single slice of silicon as opposed to layers of smaller pieces).

Output voltage also depends on the number of cells on the panel.

In the past this has commonly been 32, but now some 36 and even 40 cell panels are available.

That said, they’re larger, of course, so an array of interconnected smaller panels might be a better solution.

Module efficiency is now more often around the 20% mark, as opposed to 12-15% for older models and semi- flexible (up to 20° bend) are usually better than flexible (up to 180° bend).

A rigid panel is more efficient, but less robust

There are a huge number of panels on the market, but many use the same cells.

Sunpower Maxeon cells are exceptionally good, as are the Panasonic HIT range and LG, but they are pricey.

If the maker is offering a 25-year guarantee instead of a 3-5 year one, you can be pretty confident they’re good.

When it comes to charge controllers it’s definitely worth paying a little more for a decent MPPT.

A cheap PWM might be okay just to keep a small starter battery charged with a 30W panel, but the MPPT will give you much more when it comes to heavy service.

Victron are probably top of the range, while cheaper brands like MakeSkyBlue and EPever are also good value – but treat imports of unclear origin with care.

ABOUT THE AUTHOR

Duncan Kent has been evaluating and reviewing yachts and marine equipment for the past 30 years

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What You Need To Know About Boat Solar Panels

Advertisement

Sunshine and boats are a natural together, so why not use all that free energy? Here’s the lowdown on solar panel selection and installation

I first embraced the idea of solar power while up a pole (literally) in the Atlantic Intracoastal Waterway replacing dead batteries. It was the early 1980s, and I was maintaining buoys, beacons, and other such Aids To Navigation (ATON) for the U.S. Coast Guard, replacing massive, nonrechargeable batteries with rechargeable solar-powered ones. The higher-ups said the solar rechargeables would last six years – twice as long as the one-shot batteries. As the deck-ape in charge of lugging all those batteries up and down the ladders, my back and I immediately appreciated the whole “free power from the sun” thing, a concept I continue to embrace.

The strategy behind s olar energy onboard is simple: A solar panel converts sunlight into electricity, after which wiring conducts it to your batteries for storage until needed. Solar panels are used to keep batteries or banks charged rather than to power equipment directly. This arrangement allows the panels to store generated power whenever produced, while providing a steady source of power to a piece of equipment even when the panel is producing no power.

While they do require an initial outlay, solar panels can easily pay for themselves in money saved and independence gained over their service life. They’re noiseless, have no moving parts, and they provide free electricity for years with minimal maintenance. Solar panels also have the benefit of being modular, letting you start small and add more as your power requirements increase.

The benefits of solar

Almost any boat can benefit from solar power. Whether at a slip, mooring, or on a trailer, boats can keep their batteries topped off without the need for external power. You can also use solar power to supplement or even replace other onboard charging sources, reducing or eliminating the need to run engines or generators to keep batteries topped off (a wasteful practice that burns fuel while wearing down the costliest pieces of equipment onboard).

While underway, it’s a plus to be able to recharge a dead battery in an emergency – say, to operate a VHF radio or navigation gear. While dockside, solar panels keep batteries charged and vital systems (such as bilge pumps) up and running without the need for shore power.

Just about any boat can benefit from solar power, whether it’s to keep batteries topped off or supplement other onboard charging sources.

Mount solar panels where they are exposed to maximum sunlight but do not interfere with operation of the vessel. 

Bottom: Something as simple as the shadow of a line or shroud can reduce or halt output.

Types of panels

Solar panels contain photovoltaic cells – small silicon semiconductor devices that convert sunlight into electricity. Each cell generates between 0.45 and 0.5 volts, depending on exposure to direct sunlight. Cell size determines amperage, with a 3-inch cell producing roughly 2 amps, a 4-inch cell a little over 3 amps, and a 5-inch cell around 5 amps.

Construction-wise, the three main types of solar panels are monocrystalline, polycrystalline, and amorphous (or thin-film) technology.

Monocrystalline panels have been around the longest and remain the most popular. The panels are constructed of thin slices of crystal silicon (each cell is cut from a single crystal) housed in a rigid, aluminum frame and covered with tempered shatterproof glass. The panels have a uniform black, blue, or gray appearance and are generally quite rugged, although they can be cracked or broken if subjected to extreme abuse.

Monocrystalline panels have the longest service life of the three types. With a conversion efficiency of around 17%, they’re also the most efficient and have the highest electrical output per area, but they are also the most expensive.

Polycrystalline cells are sliced from a cast silicon block and have a shattered glass appearance. Built in much the same way as monocrystalline panels, they’re rectangular, giving the panel itself a tiled look. Their life span is similar to monocrystalline panels, and while their conversion efficiency is lower (by 14%), they’re also a bit less expensive.

Amorphous panels are made by placing a thin film of active silicon on a solid or flexible backing (such as stainless or aluminum sheeting) depending on whether the panel is to be rigid-framed and glass-fronted or flexible. Flexible amorphous panels, in which cells are sandwiched between rubber and polymer covers, are light and tough enough that you can walk on them and, in some cases, even roll them up for storage.

This type of solar panel is also better if shade is an issue. With crystalline panels, even the thin shadow of a rope or shroud across one cell can reduce or halt output of an entire module. Amorphous panels have “bypass” diodes that essentially turn off shaded cells and provide a current path around them. Some monocrystalline panels also have bypass diodes, but this feature comes at an increase in cost.

Amorphous panels are the least expensive of the three types, but their efficiency is also lower – around 8%, or roughly half that of a monocrystalline type. This lower output is somewhat mitigated in newer panels, however, which use three-layer construction. Each layer absorbs different colors of the solar spectrum, so the panel will deliver more power longer each day and during lower light conditions than the other two types.

The charge controller should be mounted below decks and as close to the battery as possible. 

Follow manufacturer instructions for wire connections.

Planning the system

While factors such as cost, mounting options, and output are important, a successful installation depends on knowing what you want the system to accomplish. Is the goal to float-charge a single battery or supplement an overall vessel energy plan? Answering these questions up front will help determine the type, size, and number of panels required.

To understand the process better, let’s walk through the basic steps to determine power requirements and installation considerations for a single solar panel installation. While the example itself is simple, the steps are the same used to plan more complicated installations.

For our example, the goal is to install a solar panel to provide charging for a single 12-volt, 100-amp-hour wet-cell battery used to power an automatic anchor light on a moored vessel.

The first step is compiling a daily power consumption estimate to determine how much solar power is needed.

The daily self-discharge rate for a wet-cell battery is roughly 1%, meaning our 100-amp-hour battery requires one amp every 24 hours just to maintain the status quo. The anchor light draws 50 milliamps per hour of operation, and we’ll assume it operates 10 hours each night. Multiplying current draw (50 milliamps) by hours of daily operation (10) generates a daily energy expense of 500 milliamps or .5 amps.

This means our solar panel must meet a minimum daily energy tab of 1.5 amps – one amp of battery self-discharge rate plus .5 amps of power draw for the anchor light.

Next up is figuring out panel size and the best mounting location. For our example, let’s assume the panel will be a horizontal, fixed-mount installation. A 10-watt horizontally mounted panel should generate between 3- and 5-amp hours per day.

We’ll need at least 13 volts to fully charge our 12-volt battery. As most solar cells generate at least 0.45 volts, you’ll want a panel with a minimum of 33 cells, which should provide around 14.85 volts.

Keep in mind that’s the minimum needed, which may not be enough once you factor in a few cloudy days. Most panels are designed to generate between 15 and 20 volts to overcome problems like cloudy days or inherent electrical resistance within the panel or installation components. While this higher voltage lets you make up for less electrically productive days, it also means you’ll want to install a solar charge controller (voltage regulator) to avoid battery damage due to overcharging.

Attempts to plan a system that tries to use the output of the panel and capacity of the battery to prevent overcharging (and avoid the installation of a charge controller) is false economy and should not be done. The system will never meet its full output potential and, worst case, can damage the battery due to overcharging.

A word on ‘charge controller confliction’

If your vessel has multiple charging sources, such as solar panels and a wind turbine, a crucial but often overlooked consideration is “charge controller confliction.” In short, this is an issue where the charge controller for your solar panel and the charge controller for your wind turbine are internally adjusted to the same maximum charge voltage set point. This means they are constantly fighting each other to be the dominant power source, which results in diminished overall charging output and performance. An in-depth article on this issue can be found at ­missioncriticalenergy.com (in the website footer, click “Superwind Turbine Manuals & Technical Bulletins.” Under the header “Charge Controllers,” select the document “Resolving Charge Controller Confliction”).

While this article addresses charge controller confliction at remote, off-grid sites, the information provided is also applicable to vessel installations. — F.L.

Location and mounting

Solar panels should be mounted in a location where they are exposed to the maximum amount of sunlight but do not interfere with operation of the vessel or the movement of passengers and crew. Solar panels will typically be either fixed or mounted on some type of movable bracket that allows you to actively point the panel toward the sun for maximum output. Both methods have their pros and cons. Fixed panels (which are normally mounted horizontally) don’t produce as much power as a panel that can be adjusted to face the sun. The downside is that adjustable panels must be aimed throughout the day to maximize their output.

Use good quality, marine-grade heat shrink connectors (top) and liquid electrical tape (right) to create airtight, waterproof seals and reduce corrosion.

Installation

After choosing and mounting your panel, it’s time to connect it. The first thing you need to determine is the size (gauge) of the wiring to be used. Multiply your panel’s rated amp output by 1.25 (which adds a 25% safety factor). Then measure the length of the entire wiring run, panel to battery, and multiply by 2. Once you have these two numbers, refer to the American Boat and Yacht Council’s (ABYC) 3% voltage-drop table for wire size. Ancor Products offers a handy wire calculator on its website ( ancorproducts.com/resources ).

Always use good quality marine grade connectors  and tinned, multi-stranded copper wire with vinyl sheathing. The wire will run from the solar panel to the charge controller first, then to the battery. Try to keep the wire run as short as possible, and if it transits an external deck or cabin house (it likely will), be sure to use an appropriate weatherproof deck fitting.

The charge controller should be mounted below decks and as close to the battery as possible. You’ll always want to follow the manufacturer’s instructions for connections, but in a typical installation you’ll connect the solar panel’s positive (red wire) lead to the charge controller’s positive input wire or terminal and the negative (black wire) lead to the charge controller’s negative input wire or terminal.

Next, connect the charge controller’s negative output to the battery negative terminal and the controller’s positive output to the battery’s positive terminal via an appropriately sized in-line fuse (or circuit breaker). ABYC recommends these be installed within 7 inches of connection to the battery or other point in the DC system. To reiterate, the installation of the charge controller can vary among models, so follow the manufacturer’s installation instructions.

Finally, ensure all connections are waterproof and secure any loose wire runs with wire ties and cable clamps for a neat installation. Then get ready to lean back and soak up some free sun.

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Frank Lanier

Contributing Editor, BoatUS Magazine

Capt. Frank Lanier is a SAMS-accredited marine surveyor with over 40 years of experience in the marine and diving industries. He’s an author, public speaker, and multiple award-winning journalist whose articles on boat maintenance, repair, and seamanship appear regularly in numerous marine publications worldwide. Contact him via his YouTube channel “Everything Boats with Capt. Frank Lanier” or at captfklanier.com.

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