hydro generator for sailboat

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Hydrogenerators – on test

If you’re planning to go long-distance cruising you’ll most likely be looking to fit one or more forms of power generation to avoid running your propulsion engine.

Thanks to modern alternator designs that offer increased power at lower rpm, hydro-generators are becoming a worthwhile investment for yachtsmen who regularly sail long passages. Yes, they do create a slight drag on the yacht under way, but only around 0.25kt or so, which is unlikely to worry most long-distance cruisers.

How do they work?

A hydro-generator has an impeller (reverse prop) that rotates when towed behind a yacht. That rotation is applied to an alternator, which produces AC power that is rectified to produce a DC charge for your batteries, in a similar way to a shore-powered battery charger.

Early models towed an impeller on a long line behind the boat, which was attached to an alternator on board. But their trailing impellers were often bitten off by large fish and they frequently tangled up when fouled or if not retrieved correctly. Current devices have an impeller attached to a submersible leg – not unlike an outboard motor.

Modern, brushless alternators with magnets have reduced turning resistance and increased efficiency, enabling them to produce more power at lower revs. A hydro-generator is an effective way to provide constant electrical charge over a long distance. On a 40ft yacht one of these can produce around 200Ah of charge every 24 hours at 6kt, which is enough to run most electrical items on board.

They also require little maintenance, other than weed clearance and periodic checking of the electrical connections.

Swi-Tec Hydrocharger

First this HG produced a high current flow, although not stable as it fluctuated considerably between readings. Hence the charge levels in our results table are derived from a mean between lowest and highest reading for each speed. The control box is liable to overheating, as the fan appears to be prone to failure. Our test team felt the box was more complicated than necessary.

• Verdict 6/10

Watt & Sea

We tried the 600W model with the mid-range impeller as that was more compatible with the others on test. Although not as powerful as the Save Marine and Swi-TEC HGs at the lowest and highest speeds, at a typical cruising speed of between 5-6kt the output is strong and, importantly, stable.

We liked the ease of installation and straightforward operation, including the simple ‘plug-and-play’ charge controller.

• Verdict 7/10

The SailGen is easy to mount and, having the heavy alternator at the boat end, is light and easy to deploy and lift. The dive plane idea works well and, though its real-time output is less than others, being always kept at the correct depth means its charge level is far more consistent.

• Verdict 8/10

The output is a bit lower than SailGen’s, which itself is middle of the range in comparison with all the others, but having the 2-in-1 option of a wind generator could be a real bonus for those planning to make long passages then coastal cruise in windy areas such as the Trades.

Save Marine

We liked the lightness and ease of deployment of the Save device, especially the arm that kept the lines tidy and secure. We also thought the turbine design to be innovative, quiet and very efficient. Finally, we loved the idea of the remote monitoring on a smart device, especially as the charge controller is fully automatic so there are no switches to be flicked or audible alarms to listen out for.

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Everything you need to know about hydrogenerators

• Sam Fortescue
• December 13, 2023

Design developments have made hydrogenerators the most efficient form of sustainable auxiliary energy for yachts. Sam Fortescue reviews the latest innovations

The potential of hydrogeneration has been well understood for decades, but it’s only over the past 15 years that the idea has started to become properly commercialised. In essence, it’s a very simple concept: the boat’s motion through the water turns an alternator which generates electricity to recharge the onboard batteries.

‘Every yachtsman owns a sophisticated wind energy machine in the form of the yacht itself,’ explains Peter Andersen of Eclectic Energy, which manufactures the Sail-Gen and Duogen hydrogeneration systems. ‘Hydrogeneration provides a simple way of converting a small part of the power harnessed by the yacht’s sails directly into electricity.’

Because water is a much denser medium than air, a small hydrogenerator fitted to the transom of a yacht can potentially produce a great deal more energy than if a larger wind turbine was fitted to it.

‘Kinetic energy increases proportionally to the cube of the velocity,’ adds Andersen. ‘That means producing 300 amp-hours per day or more is a realistic prospect while cruising at 7-8 knots with a hydrogenerator fitted. And it’s the reason why more and more boat owners are now opting for water generation, although it’s still not as popular as it should be.’

By contrast, a tradewind run with a wind turbine might yield just 80 amp-hours per day, because the apparent wind on a run is lighter. Good performance might see 40W output from 10 knots apparent. Similarly, solar panels only produce a fraction of their rated output for most of the day, so you’d need a large array to match the return of a modern hydrogenerator.

A blend of all three will, of course, give the best outcome for different conditions at anchor and under way – but on passage, it’s hard to beat the benefits of a good hydrogenerator.

Watt&Sea’s hydrogenerator is a flexible option

Speed v drag

The speed versus drag issue has always dogged hydrogeneration technology, mainly because hydrogenerators only put out meaningful energy once a boat reaches speeds of five knots or more. However, the increasing use of hydrogenerators on the international offshore racing circuit has started putting paid to most of those concerns, with all manufacturers now agreeing that the extra drag of the impeller in the water is negligible. It also becomes non-existent once the boat reaches hull speed.

The main issue for cruising sailors is the boat speed required to obtain meaningful energy from a hydrogenerator, which is mostly a question of the diameter and pitch of the impeller. Just as you need to ensure that an auxiliary propeller is matched to both the power of the engine and the speed of the hull, so the impeller on a hydrogenerator must be correctly sized for the speed of your boat under sail and desired power output.

The pitch also needs to be set to offer the optimum angle of attack for the boat’s likely range of speed through the water. That’s why leading manufacturers offer a choice of impeller, or at least an adjustable one.

Hydrogeneration is the most efficient form of sustainable auxiliary energy for yachts

The Watt&Sea is the most flexible in this respect. Its two models (300W and 600W maximum output) can be equipped with a 240mm diameter impeller or a 280mm unit. The difference in output is striking: at five knots boat speed, the smaller one produces 100W, while the larger one can manage 120W. Over the course of a day, that amounts to an extra 40 amp-hours on a 12V system.

The smaller impeller has a maximum boat speed of 11 knots, which will be enough for most cruising monohulls. Only sporty catamarans would need to consider the smaller 200mm impeller with its 13-knot top speed. Faster than that and you’d need to look at a race model with a variable pitch.

Charging performance

Apart from price, the factors differentiating the various brands on the market are their charging performance and mounting system.

Eclectic Energy is the only manufacturer whose generators rectify the current on board to produce a DC output that can be wired directly to the batteries. This has the benefit of simplicity, but requires beefier cables running all the way from the generator to the batteries.

The Duo Gen hydrogenerator from Eclectic Energy

Watt&Sea’s hydrogenerator puts out a three-phase, low-amperage alternating current that runs through a DC converter. The converter monitors the battery voltage to determine whether it is in the higher power absorption phase or the lighter float phase of charging. After that, an electromagnetic brake stops the impeller if it’s spinning too fast and becoming dangerous.

Swi-Tec’s charge controller funnels all the power from the generator into the batteries until they reach a predetermined voltage. At this point, the MPPT (Maximum Power Point Tracking) algorithm reduces the charge to nearly nothing, a buzzer sounds to alert the skipper and the impeller brakes itself automatically. It can then be changed to ‘freewheel’, allowing the propeller to rotate freely.

The Remoran is perhaps the most ambitious of all, with a charge controller that can automatically detect the system voltage and then apply a ‘smart charging algorithm’. It also interacts with a smartphone app via Bluetooth, allowing you to keep a close eye on its performance and power output.

A Sail Gen hydrogenerator mounted on a yacht’s transom

Mounting systems

While Watt&Sea supplies a pod-based system that can be permanently fitted under the hull, a removable transom fitting is still the most popular choice, allowing the unit to be removed and stowed when not in use. Alignment, though, will have a significant impact on a hydrogenerator’s performance, with the best results coming from a clean, clear flow of water. Manufacturers therefore recommend an offset mounting outside a direct line with the rudder.

There is a balance to be struck, however, as heeling can make one tack more productive than the other. On twin-rudder boats, a central mount works well.

Swi-Tec and Watt&Sea both offer an optional pivoting mount for fitting to a raked stern, while the Remoran has in-built pivoting as standard, using a spring-loaded knob to tab between different settings and offering a rake of up to 40 degrees. Watt&Sea also offers different leg lengths to suit different installations, while the Remoran Wave 3 has a telescopic leg that can be adjusted by over 30cm.

Watt&Sea unit with an optional pivot mounting for attaching to a raked stern

The Seagen and Duo-Gen take a very different approach to mounting, with a flexible yoke providing a single point of attachment. The alternator is attached at this end, while the impeller is at the end of a 1.6m tube which can be fastened out of the water in a vertical position when not in use. ‘It means the units are not rigidly attached to the yacht but are free to pivot,’ explains Eclectic Energy’s Peter Andersen. ‘This de-couples the impeller from the hull movement, reducing stress on the mounting.’

Main propeller regeneration

While a standalone transom-mounted unit is the most common type of hydrogenerator technology, there is another approach – using your main propeller to ‘regenerate’ electricity whilst under sail.

Oceanvolt’s HighPower ServoProp

Fully electric propulsion from the likes of Oceanvolt and Bell Marine has long had this capability built in, as do systems from Torqeedo and ePropulsion. But parallel hybrid systems are also available, where an electric motor is installed alongside the engine to both generate electricity and drive the boat electrically. Lynch Motors in Devon has been supplying its permanent magnet DC motors to the Vendée Globe boats for years, purely as a re-generator, and now produces the flexible Red Snapper motor for cruising yachts.

The only problem with a regeneration system is that the pitch required for the propeller to drive the boat efficiently through the water may not always be the same as the pitch for optimum regeneration. ‘The lift surface on a propeller is on the wrong side for efficient extraction of energy from the water,’ explains Eclectic Energy’s Andersen.

Manufacturers have tackled this in different ways. Oceanvolt has developed its ServoProp for saildrives, which electronically adjusts its pitch depending on speed and function. The latest incarnation allows total 360-degree blade mobility and faces forwards, which increases efficiency, albeit at greater risk of collision damage. At six knots, it produces an astounding 1kW of power.

Bruntons has another solution with the cleverly engineered Autoprop, which automatically pitches up to match the boat speed. Its Ecostar version of the prop can generate 200W at five knots and up to 1kW at 10 knots when connected to an electric motor.

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Watt&Sea Hydrogenerator

The principle is simple: using the speed of the boat to turn an immersed propeller and produce electricity.

Explore the watt&sea website or contact us to learn more.

In 2015 we became a dealer for Watt&Sea Hydrogenerators for Canada and the USA – and our customers elsewhere in the world. A green product that is very much in line with our high standard of quality and engineering, the Watt&Sea is, like the Hydrovane, of huge value to the offshore cruiser. I can’t wait to mount one on our Hydrovane! – Will Curry

HOT SEAT WITH WILl & RICHARD

10 Reasons to choose Watt&Sea

• High electric output – 24 Amps at 7.5 knots of boat speed
• Negligible drag because of leg and blade shape
• A source of free green power
• No need to run the engine to charge: saving in fuel consumption
• Completely quiet
• Lightweight
• Easy to install, especially with the Hydrovane bracket
• Maintenance-free
• Has a sleek design and look… just like the Hydrovane!
• Designed and manufactured by top racers and engineers in France

Mount the Watt&Sea on your Hydrovane

Install your Watt&Sea in the perfect position – attached onto the Hydrovane shaft.

This unique installation, exclusive to Hydrovane owners, means no extra holes in the transom and allows easy use and removal of the Watt&Sea.

See the Galleries section for photos.

Watt&Sea Frequently Asked Questions

Which model, leg, and propeller size is best for me.

Please email Richard with your boat type, a photo of the transom, average cruising speed, and shipping location. He can provide further information, answer any questions, and send a complete quote.

How does the it integrate into my charging system?

The Watt&Sea comes standard with its own converter and MPPT charge controller to hook directly to your batteries or central bus. The system is plug-and-play and compatible with any existing infrastructure.

What type of batteries can it charge?

The system is compatible with any type of batteries including lead-acid, AGM, and Lithium. If needed, charging and float voltages can be manually set via the Bluetooth app.

What speed loss is to be expected?

Watt&Sea doesn’t have any specific data on the effective drag of the device, or about the speed loss it generates. All immersion and lifting trials at constant speed have not shown any substantial difference on the speedometer for a loaded cruising boat. Testimonials back this up.

Can I replace the propeller?

Yes, replacing the propeller is simple and only requires an allen wrench and an extractor screw.

How should I maintain the device?

Wash down the outside with fresh water from time to time.  The device does not require any specific maintenance.

What is the anti-corrosion treatment?

The aluminum parts are anodized, and coated with paint. They are also electrically insulated from the other metallic parts to prevent electrolytic corrosion.

How reliable is the system?

The Watt&Sea has been designed with the latest technology. All metal parts are made either in specially treated aluminum or in 316 stainless steel.

The generator housing is sealed with hi-tech ceramic-carbon gaskets. These gaskets have a lifetime of several thousands of hours and will painlessly support a circumnavigation.

The housing is filled with a lubricating oil and slightly pressured to prevent any water seepage.

In addition, the alternator is immersed in a resin that encapsulates electrical conductors. Should any dampness occur, the electric parts would not be damaged.

Overall, the system is impeccably designed and built – and is therefore highly reliable.

What power output can I expect?

The power generated increases exponentially as boat speed increases. At 5 knots, the output power is about 120W (or about 10A on a 12V battery) with the 280mm propeller. At 8 knots, the system produces 4 times more power, i.e. 480W (about 40A in 12V ). The output may differ depending on sea conditions.

Contact us to learn more! 

Watt&sea downloads.

Sailboat Wind Generators: The Ultimate Guide 2024

Sailboat wind generators are a way to capture the energy of the wind and use it to charge your batteries and power electronics aboard your vessel.

A large part of the appeal of living on a sailboat, for many people, is being more or less self-sufficient – using the wind for propulsion, and the elements to generate all the power you need.

Solar panels are a wonderful technology, literally magic, but the sun doesn’t shine every day. In fact, of the most popular cruising grounds in the world aren’t even that sunny. It rains three to four days a week in Barbados or Antigua, for example (don’t even get us started on the English Channel).

And what about night sailing – keeping critical loads like autopilots and instruments online after the sun goes down?

A marine wind generator fills in those vital gaps in the energy picture, and eliminates the need to generate or run the engines to keep your electronics online.

In this expert guide we take a deep dive into sailboat wind generators, covering everything you need to know – from how they work through to the very latest technological advances.

With thousands and thousands of miles under the keel, we have lived off-grid using technologies just like this for almost a decade now. We’ve rewired more boats than anyone should ever have to. We’re marine electronics nerds, basically, and specifically very passionate about renewables like wind and solar.

That’s why we couldn’t wait to write about this topic, and why you’ve got a good 4000 words on it! Sorry about that! But feel free to skip and just read the information you’re interested in, we don’t blame you!

So, let’s take a close look at sailboat wind generators, how they work, what makes a good one, the best sailboat wind generators that we think deserve a place on your next nautical expedition.

As an Amazon Associate, we earn from qualifying purchases. We also earn from other affiliate programs. This means we may receive a small commission on products purchased through our links at no extra cost to you.

Table of Contents

The best sailboat wind generators – best budget choice, the best sailboat wind generators – best overall, what is a sailboat wind generator, why install a wind generator on a sailboat, wind generators vs solar power.

• What is a dump load on a marine wind generator ?
• Marine wind generators vs hydro generators

Our top budget choice: Nature Power 500

If you are in the US, the choice for the best budget marine wind generator is easy – it’s this guy , the Nature Power 500, which West Marine have sold for donkey’s years with eternally solid reviews.

It’s a 500-watt turbine that is natively compatible with both 12V and 24VDC systems. It’s made from marine-grade aluminium that’s also coated in a thick, durable coating to help it withstand years at sea.

This wind generator is rated for winds up to 110mph – well into hurricane territory – and it comes as a complete kit including a charge controller using the latest MPPT technology. The controller even has an electronic brake, even though it’s a manual one.

Honestly, this is just a lot of value for the ~$700 they’re asking, and very easy to recommend for the best budget sailboat wind generator.

We don’t massively recommend most of the budget options on Amazon for extended cruising – they’re just not built for the task. But if it’s all your budget will stretch to, something like a Pikasola 400 would be the best bet for a sailboat wind generator under $500.

Readers in the UK or Europe could look at something like a Rutl and 914i . You’ll pay a little more, around £850, but a Rutland is a proper piece of kit – they’re been manufacturing marine wind generators since the 1970’s, long before solar panels were even seen on pleasure yachts.

The 914i will produce about 260 watts in 30 knots of breeze, or 20+ amps into a 12-volt battery. In a hurricane it’ll make over 400 watts.

This is a genuine marine wind turbine built from quality parts and specifically designed for the aggressive saltwater environment. It comes with very few compromises, from the bundled MPPT tracker to its extremely quiet operation.

The charge controller supports a small solar panel as well, which is sort of nice – but we’d highly recommend using a top-quality, stand-alone MPPT charge controller for any solar panels if you can possibly afford it.   

If you are in Europe, or can import, we think the Silentwind Pro is probably the best sailboat wind generator you can buy right now. This is with the caveat that while we’ve seen these installed on lots of different yachts, talked to multiple long-term owners, and even handled one out of the box, we’ve never actually owned one.

That’s because they start at about €2,100, which is a considerable sum for a 420w wind generator. But what you do get is an incredibly refined package – one that picks up and starts generating with as little as four knots of breeze, and remains whisper-quiet right up into the high RPMs.

The Silentwind Pro uses hand-laminated carbon blades that are rated to withstand hurricane-speed winds, but that are also highly efficient across the curve. This is definitely one of the most engineered solutions on the market today.

The polished package is rounded out by features like an automatic electronic brake that kicks in if the wind exceeds a certain speed. Cheaper options may have an electronic brake but it generally has to be tripped manually by the crew.

Models without an electronic brake of any kind are frankly dangerous, because you have to lasso them to stop them – which is how the gentleman broke his arm, and wind generator, in the earlier example.

Other than Silent Wind, there are a few slightly cheaper options that are still very good. For readers in the US, one option made locally is the Air Silent X made by Primus Wind Power. We don’t have as much experience with these, but we have met a couple of happy owners and have heard similar things to Silentwind.

Primus claim they have the bestselling wind turbines anywhere in the world; we’re not sure about that given that Marlec / Rutland have been around nearly two decades longer, but either way their site states they’ve sold more than 150,000 wind generators since ’95, into over a hundred countries.

Primus make six different models at different price points that are all potentially worthy of consideration, but the Air X Silent or Air Breeze are both solid choices.

Rutland wind generators also remain easy to recommend across the board, particularly to readers in the UK and Europe, and a premium option would be something like a Rutland 1200 .

At around £1,500, or $1900, the Rutland 1200 can produce up to 480W flat out, and will hit 300W in only 20 knots or so of breeze. It’s a proper marinized unit built to withstand the rigours of life at sea, and that should provide years of low-maintenance service.

A sailboat wind generator, also known as a marine wind turbine or wind charger, is a device for capturing wind energy and turning it into electricity.

Sailboat wind generators typically have 3 or more long, aerodynamic rotor blades attached to a central hub. The blades translate wind energy into rotational force and spin the hub, sometimes at near-supersonic speeds .

The hub is attached to an electrical generator – a lot like the alternator on an engine – that generates electricity as it spins.

A wind turbine is an electrical fan operating in reverse. The fan takes electricity and uses it to spin a motor, attached to a hub and some blades, creating wind.

A wind turbine takes wind energy and uses it to spin a hub attached to generator, creating electricity.

You can actually just spin any DC motor to generate electricity , but it helps a lot if you pick one that generates the flavour of electricity you’re after.

Brushed motors are appropriate for generating DC, whereas a brushless motor is better suited to AC voltage applications.

A handful of marine wind turbines, mostly older ones, do use a brushed motor set up to produce a voltage that can directly charge a 12 volt or 24-volt battery.

Brushed motors are called that because they literally have a core of metal brushes that drags along inside outer, magnetic stator. Those brushes wear out over time and need to be replaced. They’re in something like a starter motor that works intermittently, but putting them in wind generators was always a bad idea.

They’re also noisy – which is a major consideration in a device that is going to run overnight, above your head, while you sleep, every night.

Brushless motors have so many advantages over brushed, from their efficiency to their lifespan to their reduced mechanical noise. As such, most wind generators produce AC electricity and then rectify it to DC at the regulator in order to charge the battery bank.

This means you will normally have three wires leading from the wind generator on your sailboat to the charge controller. It also means you definitely don’t want to connect those wires, carrying AC electric, to your DC battery bank, without passing them through the charge controller first.

Wind generators offer a lot of advantages – notably the ability to work day and night, and in both sunny and stormy weather.

Solar panels are great, but they only work during the day – and on sunny days, at that. They’re also affected a lot by the seasons, because in winter there are both less hours of daylight, and the sun is lower in the sky, its rays have to travel further and they strike the panel at an oblique angle. And, it’s cloudy or rainy nearly every day.

Regardless of season, as we’ve explored earlier in this guide, some of the most popular sailing destinations don’t actually have reliable sunshine – but all of them have reliable wind.

Not so with sailboat wind turbines, which work just as well on sunny days as stormy. They often generate even more power in winter, on days when solar might be producing at 10% or less.

This effect makes wind generators a big enabling technology for grey-weather sailing, from extending your sailing on into the “shoulder season” and benefitting from empty bays and anchorages, to exploring unconventional cruising grounds such as the Scandinavian fjords.

Besides stormy and overcast days, wind generators will keep on producing at night. This is particularly helpful when night sailing with the radar, AIS and full nav suite running, maybe plus an autopilot, and then all your domestic loads like your fridge and freezer. Even if you’re just at anchor, it’s nice to wake up with topped-off batteries every morning.

This doesn’t apply if you have a modern boat with ample battery storage, but when we were just getting started in sailing, we would frequently have half-flat batteries by morning.

Not only does this shorten the life of the bank, it occasionally even meant we struggled to pick up the hook in the morning – which is a bit of a safety hazard. Again, this is mitigated by wind.

None of this is to say that you should ditch solar power for wind. Solar power has many wonderful properties, explored below, and the two technologies actually complement each other very well. If you have a large enough vessel, we fully recommend you try to integrate both into your power plan.

Wind and solar are both very useful technologies to the cruising sailor, each with its own set of advantages and disadvantages. Their pros and cons in fact offset each other and synergise quite nicely, compensating for each other’s weaknesses.

As such, we’d argue it’s less about deciding which is better, and more about figuring out whether you can incorporate both into your power plan somehow.

Nonetheless, let’s have a look at how solar power and wind generators compare and contrast, and some of the pros and cons of each technology.

Advantages of solar power vs wind power

Solar power’s major advantage over wind is that it’s “solid state”. This means it has no moving parts to wear out, and requires almost no maintenance.

In fact, solar panels will generally sit and faithfully do their thing decade after decade with almost zero human interaction. A common standard nowadays is for panels to retain 90% of their producing power after 20 years .  

There’s a 10kW solar array in Switzerland that’s been feeding directly into the grid since 1982; it’s over 40 years old and going strong.

Solar panels benefit from wiping down once or twice a year, but other than that, they’re a totally set-and-forget technology.

Many sailing destinations have ample sunshine, with long hours of direct sun throughout the sailing season.

Solar is also cheap and plentiful nowadays, and panels come in all shapes and sizes that can fit almost anywhere on a yacht – including a handful of solar panels you can walk on, although those are not cheap.

Overall, though, solar is much cheaper than wind watt-for-watt. You might pay $0.50 per watt for a good rigid polycrystalline solar panel and charge controller. A wind generator may well run to $2000 for 400w – that’s $5 per watt, up to ten times more expensive. And the wind generator has moving parts that can require replacement.

Another often overlooked advantage of solar panels is that their solid-state nature makes them very safe – there are no moving parts to catch a finger in, or spinning blades that could strike a member of the crew. They just sit and silently do their thing, year after year.

Disadvantages of solar power vs wind power

Solar only works when the sun shines. The sun, as we’ve pointed out earlier, doesn’t always shine. You might be surprised by how cloudy places like the Caribbean can be – some islands have rain up to 50% of the time.

Some popular sailing destinations, like the English Channel, average about two hours of sunshine per day, with rain or overcast skies on 75% of days annually ( no, seriously ).

There’s always night sailing, as well. If you’re night-sailing, you may well have tools like radar and AIS running for safety, plus other loads like an autopilot and anything like fridges and freezers running below.

If you only have solar power, and no wind, you may have to run the engine to make it through the night – or invest in a large battery bank that can keep up until morning.

Marine wind generators are an excellent way to bridge the gap. It can be windy at any time of the day or night, and very often the cloudy or stormy days are the windiest. It’s only sunny during the day, and only some days, so this is a major disadvantage of solar power when compared to wind.

Another disadvantage of solar panels is that they lose power quite dramatically when shaded, and sailboats unfortunately have a lot of tall, shade-casting objects. These include the mast, the boom, the sails and anything like radar or Starlink dishes .

Somewhat paradoxically, solar panels also lose power as they get hot in the sun, meaning the normal, everyday conditions in many exotic destinations can actually reduce their efficiency by double-digit percentages. They are happiest somewhere cold with lots of sun, like on top of a mountain – not in the tropics.

Advantages of wind power over solar power

The wind doesn’t rise and set like the sun – it can blow around the clock. Okay, technically, the sun rising and setting down does change the temperature and create all the wind on earth.

But the wind often continues after the sun goes down. In fact, when you’re on a boat, on the water next to land, the wind usually just reverses at night .  

It’s often windy on the water on sunny days because all wind is caused by pressure flowing from high to low, and the main source of those differing areas of pressure is heat from the sun – particularly, say, where the adjacent land and water heat up at different rates.

That’s how wind is made on sunny days. But it’s often windy on non-sunny days, too, because it’s just about air rushing between those areas of high and low pressure, hot and cold air. As such, cold fronts can bring wind too.

This makes wind somewhat more of an always-on technology than solar – especially in the places that sailing boats are found. There is usually wind offshore, and often in the anchorages too as it rolls off the hills . In some parts of the world, such as those affected by the Greek Meltemi , it blows straight 30’s weeks on end.

Overall, sailing boats are just usually found in places with abundant wind energy, so there’s a lot of synergy between sailing boats and wind generators. And we’ve pointed out, many exotic sailing destinations in the world have more wind than sun, and that’s before we get started on sailing somewhere like Scandinavia.

A wind generator has a small footprint compared to a solar panel, although it does need a large exclusion zone around it for safety. Wind generators are sometimes mounted up the mast, but we don’t generally advise putting a large, pendulum-like weight at the end of a 50-foot-long lever arm if you can avoid it as it may negatively impact the motion of your boat.

Disadvantages of wind vs solar power

Wind generators do have some drawbacks compared to solar. The obvious one is that they have moving parts, which both present a hazard to the crew and require replacement or regular maintenance.  

The worst-case scenario is a crewmember being struck by the blades. The tips of something like a Silentwind Pro can spin nearly a hundred times a second and get close to breaking the sound barrier.

Here’s an example of where someone accidentally clipped their arm on a sailboat wind generator and it both shattered their arm and sent the turbine blade flying across the cockpit. The author notes that they had also seen the wind generator explode a seagull prior to this incident.

Much of this is mitigated by putting the wind generator outboard and features like electronic brakes, so you don’t need to stop it with your right ulna as the gentleman above did. The upshot is that wind turbines are dangerous in a way that solar panels are not.

The constant motion also generates wear and tear. It used to be worse, back when we used brushed DC motors – but the bearings in brushless motors do eventually wear out too, and they benefit from regular greasing a bit like your winches. It’s just an extra thing to maintain.

It can be too windy for wind generators, too. It can’t be too sunny for solar panels (although it can be too hot). Many modern, top-end marine wind turbines have that electronic brake built in to compensate for this, but you still have to shut down and stop producing when it blows a gale.

Another disadvantage of wind is that it’s really expensive compared to solar on a watt-for-watt basis. Good polycrystalline panels paired with a brand-name MPPT controller might come to $0.50 a watt at the time of writing, while a leading wind generator works out at $5.00 per watt.

This is compounded by the fact that wind does often produce on quite a concave power curve. That is to say, you need a fair amount of wind to produce anything at all, and probably need gusts into the 30-knot range to start to see your rated wattage.

Another often-overlooked point is that if you’re sailing downwind, you are robbing the wind generator of air. If you are sailing downwind in 15kts of breeze, making 7kts, the apparent wind speed at the generator is only 8kts – which might not even be enough to start generating.

Finally, wind generators can be noisy. Again, brushless motors have helped with this significantly, but there is still the rushing of the air over the blades, and any eccentricity in the bearings or blades will send maddening, resonant tremors down the pole and directly into your sleeping quarters at all hours of the night.

The latest wind generators make use of things like acoustic decoupling, a fancy term for having a rubber dampener between the end of the pole and the deck, to mitigate this.

What is a dump load on a wind generator?

A dump load , also called a dummy load or diversion load, is something used in wind power to get rid of excess power when the batteries are fully charged.

One of the small downsides of a power source that runs night and day is the potential to oversupply electricity and overcharge the battery bank.

As an electrical generator supplies more and more power, it gets stiffer and stiffer to turn. The power has to come from somewhere, and it’s felt as resistance – producing a braking effect.

If you suddenly take that braking effect away by disconnecting the battery bank, the wind turbine will start spinning at very high speed, causing anything from rapid and excessive wear on the bearings through to a catastrophic failure where the blades shear off at supersonic speeds.

In order to prevent this from happening, the charge controller has the option to switch between charging the battery and supplying power to a dump load .

The dump load can simply be a big resistor. It will heat up as the wind generator spins on, and safely apply a brake to it by literally just wasting power as heat.

You can probably guess where this is going. Another option is to use an element specifically designed to heat up, and use it to heat water. You can easily buy DC immersion water heater elements for $20-30 , connect them in the place of the dump resistor and use them to make hot water with the excess power instead.   

We’ve often daydreamed about using it to make ice or run a teeny tiny aircon unit as well.

Some of the top-end sailboat wind generators will automatically apply an electronic brake and safely stop the blades when the bank is full, and it varies from model to model whether they simply have that as an option, or it replaces the dump load entirely (including useful ones, like making hot water).  

Do not be tempted to use the dump load to charge a second battery, such as a starter battery, when the first bank is full. If you do, you will encounter problems once the second battery is full and the turbine starts to freewheel.

If you do want to charge several banks at once, or one after the other, you want a split charger connected to the main charging output instead, and a highly resistive load that can run indefinitely on the dump load output.

Marine wind generators vs hydro generators  

Hydro generators are another way of capturing the energy of the wind and turning it into electricity. But instead of capturing the flow of air, a hydro generator is dragged through the water behind a boat under sail.  

The elephant in the room here is that a hydro generator is only going to work when the boat is in motion. A wind generator, on the other hand, keeps on producing while you swing around at anchor.

The average cruiser spends around 90% of their time either at anchor, on a mooring ball, on town quays, or in marinas. This is because the everyday business of cruising is not so much about sailing as it is about fixing the boat, going ashore for provisions or parts, waiting for a weather window, or exploring the place you sailed to, socialising with the other yachties you just met, barbecuing on the deck, and so forth.

The wind generator works through all of that, night and day; the hydro generator only a fraction.

So why does anyone use hydro generators at all, then?

The answer lies in the fact that a traditional trade-wind circumnavigation, by far the most popular way to “sail around the world”, is almost all downwind .

As a result, you are often “running away” from the wind when you sail around the world, which has the effect of subtracting your speed from the true wind speed and deducting that much power from your wind generator.

Thus, if you want to sail around the world on say, a performance catamaran, it might make sense to drag a generator behind the boat instead of in the air. That way, its performance is tied to your boat’s speed through the water rather than the apparent wind.

An adjacent use-case to this is people who “sail around the world” in the sense of not stopping, or stopping very little. Someone sailing non-stop downwind around the world, particularly on any kind of record attempt, would probably get a lot more of out of a hydro generator.

Another place hydro generators are seen is in the regenerative systems of systems like Oceanvolt . In these sophisticated systems, the propellors of the boat itself work as hydro generators by spinning and capturing energy as they’re dragged through the water under sail.

This feature is even starting to show up on electric outboards, such as the ePropulsion Navy series.

In summary, wind generators are the most practical choice for the average cruiser, multi-year circumnavigator or liveaboard sailor. Unless you love sailing so much that desperately want to go and tack around for four hours to charge your batteries – in which case, more power to you.

Wind generators can form an incredibly useful part of the renewable energy mix on board a sailboat.

While wind power on a sailboat works out many times more expensive than solar power, watt-for-watt, it makes up for this by generating power day and night – and often making even more power at times when solar falters, such as during storms.

Cruising sailboats that only have solar power will be forced to generate or motor if it’s cloudy for days on end, something that happens at least once or twice a month somewhere like the Caribbean.

Solar, naturally, doesn’t produce at night either, so if you have a lot of electrical loads running overnight your battery bank can take a beating.

A common example of where you might get caught out is night sailing with the autopilot, radar, AIS and instruments all running, in addition to your regular loads like the fridge.

Wind generators might usually be sized to produce less than a solar array because of cost, space and weight considerations, but they have the potential to run all day and night and in any kind of weather, and as such they often punch above their weight in terms of the overall energy generation picture.

Electrical loads might slow down a little overnight, as the crew sleep and lower temperatures mean fridges and freezers don’t work as hard, but it’s not uncommon for the overnight draw on a sailboat to be 8-10 amps or more. It adds up, by morning. 

Wind represents an excellent bridging technology for nights and extended cloudy spells, naturally producing the most when solar fails – such as during storms. 

A sailboat wind generator is most effective when paired with solar and a good lithium battery bank , allowing you to generate in all conditions. day and night; and to store and retrieve that energy efficiently even at high currents. 

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--> Hydrogenerator Save Marine H240 for cruising sail boat

Principle of operation of hydrogenerator save marine.

The hydrogenerator Save Marine H240 transforms the energy of water in movement into electrical energy . It works with an inexhaustible energy : the wind, and therefore the force exerted by the water during navigation and preserves the environment. The hydrogenerator Save Marine reloads the batteries of your sailboat and brings electrical autonomy in order to ensure security and comfort on board . The electricity produced by the hydrogenerator is transmitted to batteries through the regulator to get an optimized current/voltage pair for batteries.

The Save Marine H240 hydrogenerator is especially designed for cruising sailboats, to navigate between 2 and 10 knots.

Description of the hydrogenerator

The Save Marine hydrogenerator is a new generation product who encompass some technological innovations patented and leads to several advantages.

The Save Marine Offer is composed of a complete pack comprising:

-           a embedded system of tilt adjustment adaptable to the high majority of sailboats

-           an adaptable and tilting control arm (easy manipulations)

-           embedded tips and pulleys system to ease the launching and rise up of H240

-           an automatic rising system in case of choc with an OFNI

• A home plate  for a discreet fixing of H240 on the boat transom
• A  configurable regulator box
• A pass-hull, with all the cables and connectors
• A monitoring software to real time production monitoring
• A bag for transportation and storage, marine quality

Mecanical and electrical data

Mechanical data sheet

Electrical characteristics of the Save Marine H240 hydrogenerator

Voltage at the output of the regulator : 12 or 24 volts (configurable in the regulator during installation)

Type of batteries : majority of batteries technology are compatible with our solution (lead open, lead closed, lead calcium, AGM, lithium-ion).

The regulator can adapt the production and optimize the batteries charging in function of her capacity (Ah).

Examples of needs couvered by the Save Marine H24 0 Hydrogenerator

Coastal navigation 

The average daily electrical needs are equal to 1100Wh or 90 Ah (with 12V batteries)

• 5 hours of navigation at 7 knots permit at the Save Marine hydrogenerator to cover 100% of the electrical needs
• 8 hours of navigation at 5 knots permit at the Save Marine hydrogenerator to cover 80% of the needs = the totality of the power supply to the refrigerator.

Offshore navigation

The average daily electrical needs are equal to 2900Wh or 245 Ah (with 12V batteries)

• 5 hours of navigation at 7 knots permit at the Save Marine hydrogenerator to cover one third of the electrical needs , for example, more than the refrigerator and water pression post.

The Save Marine hydrogenerator is therefore an optimal solution than can be completed with others solutions of electrical production (as photovoltaic panels).

Documentation

• Hydrogenerator Save Marine H240 for cruising sail boat
• Advantages of Save Marine hydrogenerator during navigation
• Awards obtained for the hydrogenerator Save Marine
• Testimonies of our clients about hydrogenerator Save Marine H240

Where you can find the H240 ?

You want to discover the H240, to obtain additional information, talk with a pro, see specific adaptations to your sailboat, indicate us the home port of your boat ...

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Towed Water Generator

In our experiments last summer, the hamilton ferris generator did very well with a spinner in the water, less well with its optional wind blade..

Back in 1992, a friend of ours competed in the OSTAR (Observer Single-handed Transatlantic Race). Onboard electrical demands, especially from electronics, had recently grown, and he needed a charging source other than the engine. Marine wind generators were still unproven and solar panels were prohibitively expensive.

A group of us got together and bought for him a towed water-powered generator for charging his batteries. He came back with good stories of how much electricity it produced-but alas, he lost the boat and generator 500 miles from the finish, so we never got a chance to try it ourselves.

The past decade has brought only greater demand for electrical power. That demand has made wind-powered generators commonplace and solar panel technology far less costly. In addition to the engine’s alternator, these are the most common charging sources for a boat at anchor or underway. However, we rarely hear anything about towed water-powered generators. Always on the prowl for alternative energy sources, we decided to try for ourselves a towed generator on a cruise from the US East Coast to Bermuda and back last summer.

How It Works

The technology behind the towed generator is simple to understand. Its principle is very similar to the old Walker Log. As you sail, you tow behind the boat a spinning propeller on a long line that resists twisting. On the boat end of the line is a generator. As the boat moves through the water, the propeller spins, and the twist-resistant line transfers that spinning directly to the generator, which generates electricity. The faster the boat moves through the water, the more electricity is generated.

It’s worth remembering that it’s the movement of the boat through the water that turns the spinner, not the boat’s speed over the bottom. If a boat were anchored in a strong enough current with the towed generator behind, it could generate power. In this way, homesteaders living “off the grid” can make use of water-powered generators if they live next to a fast-moving stream.

Generator Basics

A generator consists of a rotating armature inside of a magnetic field. The armature contains wire windings connected to a mechanical commutator on its rotating shaft. The magnetic field surrounds the armature and the field is generally produced from permanent magnets mounted on the inside of the generator housing. As the armature rotates, the wire windings intersect the magnetic field. As the winding moves through the field, the mechanical energy of rotation gets converted to electrical energy. The generated AC voltage goes through two brushes “riding” on the commutator, which mechanically converts the generated AC voltage to DC.

The generator’s voltage output is proportional to the number of armature windings and the armature’s rotational speed. Since the towed generator can’t change its armature windings, the voltage output is proportional to the speed of the spinner through the water.

Two important parameters for generators are the electrical resistance of the windings and the number of RPM it takes to produce one volt in an open circuit (i.e. a no-load condition). The lower the resistance, the more current produced for each RPM of the armature. Some typical generator values are an armature resistance of 1.24 ohms and voltage constant of 26.5 RPM/volt. An example will help here:

If one wants to generate 5A at 12V, one needs to generate an open-circuit voltage of: 12V + (5A x 1.24) = 18.2V. The required revolution speed of the armature is: 18.2V x 26.5 RPM/V = 482.3 RPM.

This example shows that one can increase the generator’s power output by either spinning it faster or finding a generator with a lower armature resistance.

Real-World Use

Our goal on the Bermuda trip was to evaluate towed-generator technology for supplemental battery charging, not to evaluate all the different available towed generators. We chose the Ferris Waterpower 200 ($819) from Hamilton Ferris Co. as a representative offering. Other towed generator products include the Ampair Aquair 100 from Jack Rabbit Marine, the Redwing from Downwind Marine, and the LVM AquaGen.

We also brought along the Hamilton Ferris WP-200 R/S conversion kit for ($509) for mating the generator to a wind-powered propeller blade once we got to Bermuda. More on that later.

The Waterpower 200 includes a permanent magnet generator, a spinner, torque line, retrieval funnel, gimbal mount, deck connectors, cable, a Wind/Water Power Generator panel, and a diode/fuse box. The generator itself measures 4″D x 8″L, including the armature shaft. The generator mounts on the taffrail in a gimbal bracket. The bracket fits into a white nylon donut yawing movement. The 6″ x 3.5″ panel has an ammeter, a charging light, and a momentary brake switch.

The installation consists of mounting the gimbaled bracket, mounting the panel and the diode/fuse box, wiring them together with the supplied cable, and then wiring the generator into your battery system. For the purpose of our testing, and not wanting to punch too many holes in the boat, we mounted the panel and the diode/fuse box inside a cardboard box in the navigation area. We then wired this system into the boat’s main electrical panel. We were able to monitor the generator’s performance with the panel’s ammeter together with our boat’s Link 2000R.

The spinner is a 3-foot long stainless rod with a propeller on one end and a threaded receptacle on the other end. The standard prop for boatspeeds up to around 6.5 knots is a Lexan 8″ prop with 5″ pitch. Faster boats may need to change to a prop with greater pitch to slow down the spinner through the water.

The spinner rod can accommodate up to three cylindrical brass weights for keeping the spinner from rising to the water’s surface. Before purchasing any such system, check with the manufacturer for the correct setup for your boat’s size and speed.

The torque line connects the spinner to the generator. This 69′ 11mm nylon line is a very tightly woven braid. Its design is such that it acts as a flexible rod, transmitting each spinner rotation to a rotation of the generator’s armature. Each end of the torque line has a brass threaded screw firmly attached. The screw threads mate with threaded receptacles on the spinner and the generator. You must use a wrench to connect and disconnect these parts.

Deployment is very simple. First, fit the gimbal mount and generator into the white donut and tighten the restraining thumbscrew. Tie the safety line from the generator to a cleat, stanchion, or other fixed part of your boat. Assuming that the torque line was previously installed, start feeding out the torque line from the generator end while keeping the spinner onboard. Make sure that the torque line has no knots in it. Then, drop the spinner over the side. When the boat sails to the end of the torque line, the line will stiffen, and the spinner will start spinning, thereby turning the generator’s armature. The whole deployment process took us about 30 seconds.

Spinner retrieval is a little more complicated. The manufacturer’s recommended procedure is to deploy a retrieval device that consists of a large plastic funnel with the spout removed and a split up the funnel’s side. The idea is to put the split funnel over the rotating torque line with the large opening facing the spinner; then, when you want to retrieve the spinner, you “launch” the funnel down the torque line. When the funnel makes it to the spinner, it shields the spinner from water flow and stops its spinning. At that point it becomes easier to haul in the torque line with the spinner at the end. (Easier, but not easy.)

Water Generator Performance

On the trip from Cape Fear, NC to Bermuda, we tracked our electricity usage for the trip. For 98 hours of sailing, we averaged a power usage of 6.5 amps. Our main power users were the autopilot, the refrigeration unit, and navigation lights. The power usage agreed with our historical usage from previous years. On the return trip from Bermuda to Portsmouth, RI, we towed the Ferris Waterpower 200 for 58 hours of sailing time. During this trip, our average power usage was 3.1 amps. The boat’s average speed during both trips was approximately the same.

We attribute the reduction in amps used to the power generated by the towed generator. We were able to monitor the generator’s current output with the ammeter on the Ferris panel and the Link 2000R.

From this test, the towed generator supplied 52% of our energy needs.

The most common question asked by sailors regarding towed generators is, “What’s the effect on boatspeed?” It was difficult for us to determine a quantitative response, but we did try to answer it with a couple of experiments. The first experiment consisted of recording the boatspeed for one minute before dropping the torque line and spinner over the side. After the generator started spinning, we again measured boatspeed for one minute. At 5 knots of boatspeed through the water, we could only measure a drop in speed of about 0.1 knot. We repeated this test twice and got the same result. The second test involved turning on the brake switch on the Ferris panel, thereby stopping the spinner’s rotation. There was no perceptible change in boatspeed with this test.

The amps produced by the Ferris Waterpower 200 on our graph are approximately 55% lower than the graph in the Ferris Power Products catalog. We discussed this discrepancy with Hamilton Ferris, who told us that the graph in the brochure is the current going into a 50% discharged battery. If the battery is less than 50% discharged, then the current output will be lower. This information agrees with our data-our battery usage for the test went from 100% charged to 58% charged.

The Ferris Waterpower 200 was very quiet while being towed through the water. There was a little whirring noise, but it didn’t interfere with cockpit naps. As the torque line streamed from behind the boat, it “walked” to port. The instructions say to mount the generator on the port side of the taffrail so as not to tangle towed fishing lines. We did not try fishing while towing the spinner.

Retrieving the torque line and spinner was much different than deploying it. The steps involve sliding the funnel down the torque line to shield the prop, pulling in the line from the generator end, and then retrieving the spinner from the water. The crew had a good laugh watching us wrangle in the spinner and line!

The funnel has a split up the side with three lacing lines that one ties together to keep the funnel secured around the torque line. All the time that one is tying the laces, the torque line is spinning very close to the fingers, and the line yaws as the boat yaws. It’s a frustrating business. A Velcro-type fastening system, requiring less manipulation near the spinning line, would be a big improvement.

Once the funnel is laced, it gets launched down the torque line. The first time we did this, the funnel sat about three feet behind the boat, in the air, riding on the torque line. Eventually, a few seas touched the funnel, which sent it down the torque line closer to the water’s surface. Once the funnel hit the water, it quickly covered the propeller, stopping its rotation. It would be nice if there were some way to force the funnel to reach the water’s surface instead of having to rely on patience.

Retrieving the spinner, funnel, and torque line at 6 knots was a challenge requiring some strength. The slowest speed we tried retrieving it at was 1.6 knots, which wasn’t very difficult. The real issue was how to handle the stiff torque line once on deck. The first time, we tried coiling the line in a single loop, which caused twists and kinks in the line the next time we launched it. The next time we coiled the line in a figure-eight. This coiling technique was better, but it was difficult to get the line to lie down neatly and stay in place. However, deploying, from the figure-eight was easier with less kinks. We secured the coil with a piece of shock cord to a nearby stanchion. We tried once to retrieve the spinner without the funnel at a slow speed. Twists galore!

Another storage problem was that generator, torque line, and spinner have to be connected together as a single unit with hand tools. It would be more convenient if they could be easily separated with a quick, tool-free disconnect system. As it was, the assembly covered a large part of our lazarette area.

We were also careful about bending the line sharply at each end because of the hard attachment of the line to the brass fittings without strain reliefs. We did notice some fraying at each brass/rope interface after our tests. Hamilton Ferris said that this wear was normal.

As for other concerns about the line, Ferris doesn’t recommend any special precautions with regard to protection from UV light. However, the line will not “forget” any hockles that it may sustain.

Wind Power, Too

Most towed generator manufacturers sell conversion kits for using the same generator as a wind-powered generator while at anchor. The idea has appeal, so we decided to try the Ferris Waterpower 200 to convert wind power into electricity while at anchor in Bermuda.

The WP-200 R/S conversion kit includes, according to the Ferris Power Products catalog, the “wind blade [propeller] and hub, rigging mount frame, wind vane and stainless steel hoisting cable set.”

The kit is a big thing to stow. The prop is 5′ long, and the rigging mount frame just slightly shorter. For the trip to Bermuda, we lashed these two items to the mast section in the cabin, to keep them out of our way. The prop is made from wood with a white coating. It’s light and somewhat fragile.

The first time we converted the water-powered generator to wind-power, it took us about two hours. Some items made the conversion process smoother, including the fact that all bolts were 7/16″ and all set screws were 1/8″. However, some things would have made the conversion go faster:

Labels or stamps on the metal pieces indicating orientation of up or down, especially on the rigging mount frame and the wind vane frame.

The 1-1/4″ bolts in the rigging mount frame that the generator support bracket attaches to are too short. We had to compress the frame to get the bolts in.

Instructions for removing the gimbal frame from the generator.

Make the rigging mount frame one inch longer than the prop, so that the frame’s length can protect the prop from hitting things and getting damaged.

Metal clips on the rigging mount frame for attaching the generator’s wire, instead of requiring disposable nylon wire ties.

The wind-powered system is designed to be hoisted in the fore-triangle. The upper hoisting cable (pendant) from the rigging mount frame connects to a forestay. A halyard hoists the wind-powered generator up the stay, high enough to not decapitate anyone. The two lower pendants attach to stanchion bases or other tie-down points on the port and starboard side of the boat. The wind vane has a line tied to the mast to restrict twisting of the generator. The electrical cable from the generator drapes down and away from the spinning propeller. Note: we would like to see a hole in the hoisting cable shackle pin so that it can be moused with seizing wire.

We quickly realized that we had a problem when we went to raise the wind-powered generator-our roller furled headsail covered the forestay! So we had to create a new temporary stay for the upper hoisting pendant to ride. We used the main halyard, tying the bitter end to a fitting on the stemhead and extending the headboard shackle end with another piece of line so that we could take a couple of turns on a mast winch and set the halyard up tight. Then we attached a snatch block to the hoisting cable and used its sheave to ride up and down our new “stay.” This system worked fine.

Once we converted the generator over to wind power, it still took us 20 minutes to hoist the wind-powered generator. We were doing it solo, and one challenge was how to keep the blade from spinning until it was raised to the proper height. There was no one else around to hold the momentary brake switch, so we tied a loose clove hitch around the bottom blade of the prop and the rigging mount frame, with the bitter end at deck level. After raising it to the right height, a shake of the line caused the knot to collapse and fall to the deck.

This rigging-suspended generator requires that the boat be on an anchor and able to swing (i.e., point) into the wind. If there’s a strong current counter to the wind, you may spend a lot of time adjusting lines to keep the generator facing the wind.

The propeller does not have a governor. This means that if the wind starts honking, you may be spinning the blade too fast. One way to “dump” the wind is to move the wind vane line purposely so that the generator isn’t pointed directly into the wind.

Getting the wind-powered generator down also took some time. The first time we tried to stop the blade with the brake switch. It did stop, but since it’s a momentary switch, by the time we ran over to the halyard, the prop had started spinning again.

We found that throwing a light line into the spinning blade would tangle it up and stop the blade.

If we were going to use the wind-powered generator for cruising, we would replace the momentary switch with a normal toggle switch. Another idea to stop the propeller is to tie off the wind vane 90 to the wind direction.

It turned out that trying to measure how well the wind-powered conversion worked was much more difficult than with the towed-water generator. Electrical usage varied with the number of times the icebox was raided, the Lectra/San ran, music blared, and propane cutoff switch left on. (Kids!) We collected data for 247 hours without the wind-powered generator and 154 hours with the wind-powered generator. Looking at the raw data, the generator supplied, on average, 1.3 amps, or about 35% of our needs at anchor. However, we also had a tropical storm pass nearby. If we eliminate the storm time, the generator supplied only 0.4 amps, or 12% of our needs. The average wind speed during the tests was approximately 7 knots.

We get a more telling indication of how well the wind-powered generator worked for us wheb we look at wind speed versus current output. With the wind speed below 10 knots, there was hardly any power generated. Our graph is about 65% lower than the graph on page 12 in the Ferris Power Products catalog. This time, though, our batteries were more discharged-the batteries varied from 76% charged to 32% charged. We can’t explain the discrepancy in the graphs, nor could Ferris.

Conclusions

For the amount of storage space it demands, the hassle factor putting it up and down, and the small amount of electricity it generates, we would be reluctant to recommend the wind-power conversion kit. If you require power generation at anchor, a dedicated wind generator, optimized to perform its one intended function, will be a better bet.

The Ferris generator itself, however, in the guise of the Waterpower 200, does generate electricity-quietly, safely, and with few hassles-and we can easily recommend it as an electricity generating source for any offshore cruising boat. We also believe that with a little optimization for each particular boat, one can increase the generator’s efficiency by choosing the most suitable prop for the boat’s typical speed and battery discharge level. We would like to see a few changes that may or may not be specific to the Ferris product, including an ammeter with a more expanded scale at the low end, easier connectors (tool-free) for the torque line, a toggle brake switch, and an improved retrieval funnel.

These systems are not maintenance-free. Brushes and bearings do wear out and need replacing after hundreds of hours of use. “We recommend a check of bearings every 6 months,” says Hamilton Ferris. “No one ever does it. When new, they are 5/8″. When ready for replacement they are half that. We offer a Brush & Bearing Kit for $44, plus shipping.”

Downwind Marine, 619/224-2733, www.downwindmarine.com . Hamilton Ferris Co., 508/881-4602, www.hamiltonferris.com . Jack Rabbit Marine, 203/961-8133, www.jackrabbitmarine.com . LVM Ltd., 011 44 0 1462 733 336, www.lvm-ltd.com .

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For those interested in a hybrid solution, generators are a highly efficient way to extend range while at sea.

DC generators have the advantage of rapid recharging capability.

AC generators are, generally, smaller and even portable which means that the generator can be aboard only in situations where longer motoring might be required.

Battery recharging is accomplished with shore connection, hydro generation (an integrated part of all Oceanvolt systems) and/or solar panels.

In Hybrid solutions , a generator (either AC or DC) can be used to recharge batteries / extend motoring range.

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Choosing a Generator for Your Sailboat

• By Ed Sherman
• Updated: November 14, 2018

You can’t take it anymore: Your 1990s vintage cruising sailboat didn’t come equipped with a factory-­installed air-conditioning system or an alternating-current generator to power it and the other AC appliances you’ve brought aboard. Since you’ve owned the boat, though, you’ve turned into a real believer in global warming as you try to sleep through sweaty nights on board, and finally you’re ready to pull out your wallet and do something about it.

So, where do you begin? The first step is to analyze how much electrical power you are going to need. Since your boat had a basic shore-power system when you bought it, you already have some idea of your small-appliance usage, things such as hair dryers, the coffee maker and maybe even a small TV. But now you need to think in terms of running this same gear while at anchor. Additionally, if the standard-equipment shore-power option for your boat at the time of purchase was a 30-amp service, as is most often the case here in the United States, you might discover that it’s inadequate to run that new reverse-cycle air-conditioning system you’re dreaming about.

This is an area where, in my experience, a lot of boat owners go into denial as they discover that more power consumption adds considerable cost. Everything you’ve read about marine electrical systems so far tells you that air conditioning and refrigeration use a lot of power. But how much? The good news here is that these units have become more efficient in recent years and the power needs are not as great as they were when your boat was new. As an example, a modern 18,000 Btu reverse-cycle system from Dometic Corp. will need about 15 amps of AC power to get the job done. A 10,000 Btu unit is going to draw around 8 to 10 amps, depending on your location and whether you are heating or cooling.

Analyze Your Needs

The first step is to do an honest load analysis to see how much electrical power you will need. This is typically measured in thousands of watts, or kilowatts. The operative phrase here is: Don’t cheat. If you want to luxuriate in air-conditioned comfort 24-7 while cruising, it’ll cost you. Unlike powerboats, most cruising sailboats come equipped with liquefied petroleum gas stoves and ovens, so one of the major power consumers (an electric galley) is not a concern here.

All said, you are probably going to be looking at generators in the 4 to 12 kW size range. The typical owner of a 40-something-foot sailboat who wants to power up a reverse-cycle air-conditioning system, small galley appliances, a refrigeration system using either AC or DC power, a water heater and a battery charger is going to want an 8 kW generator. Larger boats that might end up having a clothes washer and dryer, larger reverse-cycle heating and cooling unit and water heater can easily end up in that 12 kW output range. The American Boat and Yacht Council offers a free trial membership with access to the relevant electrical power ­standard (E-11), including a complete load analysis worksheet for those who are so inclined and want a detailed account of their electrical needs. Simply go to abycinc.org to gain access via the consumer section of the site.

A quick way to determine your AC power needs is to look for the mandated label on each appliance. It is required to tell you either the operating voltage and amperage draw or the operating voltage and wattage.

Either way, a simple equation can be applied to get the info you need: Volts multiplied by amps equals watts; or watts divided by volts gives you an amperage value. Add the number of watts each device requires and you will get an idea of what size generator you’ll need. Remember that it takes 1,000 watts to make 1 kilowatt. Understand that this method will actually give you a result that does not take into account the fact that you might not be running all of your appliances simultaneously. The ABYC load analysis method found in the ABYC E-11 standard offers some diversity adjustments that are more conservative and reflective of the real world.

Although modern ­generators are not as sensitive to running with a light electrical load, most installers will tell you that running them at 70 to 80 percent of their maximum capacity is better for the engine. The risk here is carbon buildup in the engine’s combustion chambers if run with a light load for extended periods. So, this is a case where significant overkill is not such a good thing.

Practical Concerns

In addition to the electrical load you need to meet with your new generator, you should also be considering its weight and physical dimensions. Will the generator fit into the space you have available? The units I compared (see “Generators by the Numbers,” page 82) ranged in weight from a low of about 270 pounds for the 5 kW Fischer Panda to a high of just under 700 pounds for an 11.5 kW Kohler. This amount of weight dictates that when installing a generator on a monohull, you’re going to want to keep it on the centerline of the boat. Typically, this works out well because most sailboats built from the early ’90s on will have adequate space aft of the propulsion engine to fit in new generator. Multihulls offer more options on that front.

What might be a concern with the monohull is service access, not only for the generator itself, but for things like the propeller shaft stuffing box and shaft coupling. I’ve inspected many boats where the only way to access a leaking shaft seal was to lift the generator out of the way!

Wherever you end up installing your new generator, you need to be able to gain access to all the service points on the unit.

The physical dimensions of the generator could end up being a game changer too, so you’ll need to measure your boat’s available space carefully and compare that to the specifications for the units you are considering. You will also need to determine whether the unit will fit with a sound shield installed or not. Understand that some of the generators offer a sound shield as an option only. The presence of a sound shield, or your ability to insulate the space where you are going to have this generator mounted, could make a difference not only in size requirements but also noise issues while running.

As an example, comparing a Fischer Panda unit that comes with a standard sound shield, we get dimensions of 23 inches by 17 inches by 22 inches. A similarly rated Cummins Onan unit, which also comes with a standard sound shield, is 26 inches by 23 inches by 21 inches. A Westerbeke with a similar rating but with optional sound shield measures 36 inches by 23 inches by 25 inches. That 13-inch spread in length between the Fischer Panda and the Westerbeke could mean the difference between a doable install in the space available on your boat or not.

Finally, wherever you end up installing your new generator, you need to be able to gain access to all the service points on the unit. Can you get that oil filter off as installed? Can you access and change the water-pump impeller without needing an emergency ­chiropractic visit? These are questions that will need answers.

Power Perks

Several features related to newer generators are worth considering. One is whether the unit is equipped with digital controls that may also allow for self-diagnostics and integration to onboard networking that you or a former owner may have installed on the boat.

From a maintenance standpoint, you’ll also want to know whether the water-cooling system for the engine driving your generator is raw- or freshwater cooled. Raw water might save money initially, but will cost in the long run.

Buyers Beware

I can’t emphasize this enough: This sort of upgrade does not qualify as a do-it-yourself project unless you have ­considerable mechanical skills and experience, and labor will be a major addition to the overall cost of the installation.

Also, when you compare different units, study the supplied components carefully. Does the unit come with a remote display and control panel? What additional parts will you need? These will likely include an exhaust system, starter battery and cables, and raw-water supply hoses and a seacock. And don’t forget about wiring the generator ­into your existing, or possibly a replacement, AC ­distribution panel board. These items can add considerable cost above and beyond the generator prices shown in “Generators by the Numbers.”

If you are planning on cruising far afield with your new generator, you should also think about parts and service availability, not to mention its warranty.

Lastly, if you are planning on cruising far afield with your new generator, you should also think about parts and service availability, not to mention its warranty. As part of my ­research for this article, I looked at units from Cummins/Onan, Fischer Panda, Kohler, Northern Lights and Westerbeke. All five brands have extensive global dealer networks, so ­locating a service center that can help is just an internet search away. As for warranties, I’ve noted them in the “Generators by the Numbers” table. Keep in mind when reviewing this ­information that it is based on likely choices from the ­individual company’s offerings for a boat in the 35- to 45-foot size range. Also understand that the prices quoted are list price. Several of the dealers I spoke with suggested that discounts of $1,500 to $2,000 are quite common. That said, if you spot something you think is a deal, be certain of what you are actually getting, ­especially if it’s at a ­remarkably ­discounted price.

Ed Sherman is a frequent CW contributor, Boat of the Year judge and vice president of education for the American Boat and Yacht Council.

A green alternative

Considering the cost of installing a generator — estimated at $15,000 to $20,000, or possibly more depending on your boat and the power output selected — you might consider some alternatives.

How about essentially silent AC power via a direct-­current-to-alternating-current inverter and adequate storage capacity that relies on the latest high-capacity battery technology?

Marine electrical systems have evolved considerably over the past decade or so, and I’m at the point now where I question the need for an onboard AC generator for most cruisers, though some might still benefit from installing a DC generator to supplement solar-, wind- or water-driven charging solutions.

The current density of high-end absorbed glass mat and lithium-ion batteries has improved by 20 to 30 percent due to their inherent capacity compared to older flooded-cell batteries. They can also be discharged to deeper levels without damage and recharged much more quickly due to high absorption rates. I’m of the opinion that it might be time to look at alternative power if you are willing to spend the kind of money we are talking about with an AC generator upgrade for an older boat.

As quiet as they might claim to be, that incessant drone of an AC diesel generator, not to mention the however faint odor of diesel exhaust fumes, is going to be a reality. It’ll have to run all night if you want that AC keeping you cool.

Instead, you could run the DC generator in the morning to replenish your batteries from an overnight discharge. Or, let your solar panels and wind generator do the job. I like the concept of not having to run an engine continuously to get my AC power.

Generators By The Numbers

*All dimensions are with sound shield; **price includes sound shield; ***price does not include optional sound shield

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Comparing 6 Energy Sources For Electricity On A Sailboat

We usually have all sorts of equipment onboard our sailboats that require electricity, like navigation instruments, navigation lights, VHF Radios, refrigeration, interior lighting, and much more. We also want to be able to charge our devices, laptops, cameras, drones, and other appliances onboard.

And for that we need electricity.

Sailboats generally get their electricity from shore power in a marina or from their batteries at sea. The batteries get power from the main engine’s standard alternator, often combined with one or more of the following sources:

• Additional alternator
• Solar panels
• Wind generator

Hydrogenerator

We tend to choose our sailboat’s energy source based on how much power the equipment onboard requires. It is also important to consider what else we want to power up onboard, especially if we’re going to plug in 110V or 230V equipment. Let us take a closer look at how we get electricity onboard.

Electricity onboard a sailboat and why we need it

We need electricity on our sailboats for many reasons. The engine requires power to start, and our navigation equipment and sailing instruments need electricity to operate. We must keep our navigation lights on when it gets dark, and sometimes we want to have the interior lights on.

Another super essential and power-hungry device we ideally want to keep running is the fridge. We don’t want our food to go bad, and we certainly want to avoid having to drink warm beer. Since we live in modern times, we also want to charge all our devices and toys as well.

In the end, our sailboat has become quite power-hungry for electricity, and when we leave the shore and unplug the shore power, we have to rely on our batteries to supply the energy we need. Let us have a look at some common equipment often found onboard sailboats.

Equipment that requires electricity onboard a sailboat

If you are slightly unfamiliar with sailboats, you may wonder: What equipment do we often have that requires electricity? Check out this list I made from the top of my head. Remember that it is highly individual how much stuff we run on our boats, but these are pretty typical items:

• Engine starter
• Navigation lights
• Chart plotter
• Sailing instruments
• Sound system
• Interior lightning
• Water pumps
• Bilge pumps
• Refrigerator
• Laptop charger
• Phone and tablet chargers
• Camera chargers
• Drone chargers
• Head torch chargers
• 110V/220V inverter

This list can get endless . We definitely want a reliable way to keep us supplied with energy, and we also need a way to store this energy.

Sailboat batteries and how to charge them

The batteries on a sailboat get charged by the engine’s alternator by standard. Relying on the alternator is fine if you don’t require  too  much energy to power your equipment onboard and don’t mind running the engine often.

Modern sailboats usually carry several batteries. It is standard practice to have one or two batteries dedicated to starting the engine and a separate series of batteries, called house bank , to supply the rest of our needs. It is a good idea to separate the starter battery and the house bank to avoid draining the starter battery by mistake.

The starting battery is usually 12V (DC voltage) for most sailboats with a diesel or petrol engine. Our house bank can sometimes be either 12V or 24V, depending on your sailboat setup.

But if you are a liveaboard sailor or have lots of power-hungry stuff and equipment, it quickly gets tedious to run the engine all the time to keep the batteries charged up. Luckily, there are many excellent additional alternatives to keep your batteries charged without running the main engine.

This brings us to the next topic. Let’s look at some excellent options to keep our sailboat fed with energy.

6 energy sources for sailboats compared

It is pretty common to have a combination of two or more of the following energy sources. They all have pros and cons, but it is hard to tell which one is the best as it depends on yourself and your needs.

I am personally a huge fan of solar panels, and I get 95% of all my energy from this wonderful and sustainable source. And my list of equipment that requires electricity is way longer than the one earlier in this article…

Let us have a look at each of the six most common additional sources of power used on sailboats:

Main Engine Alternators

Most sailboats have a main engine, and the main engine has an alternator that generates electricity when running. The alternator is connected to the batteries and will keep charging them for as long as you run the machine in most cases.

Standard alternators don’t always give a high enough output to charge larger battery banks within the timeframe we have the engine running. One good option here is to add a secondary high-output alternator, which can be great in combination with another power source.

Pro’s

• Comes standard
• It gives power as long as the engine is running
• An additional high-output alternator can turn your engine into a generator

Con’s

• It requires fuel and maintenance to keep the engine running
• Usually noisy

Generators or gen-sets are typically found on larger sailboats with plenty of space to install them. It works similarly to the main engine but generally has a much higher output of 110V or 220V.

The generator then supplies your mains power the same way as if you plugged your cable into shore power at the key or marina. Generators come in various sizes with different outputs. Some are units you can move around, while others require to be permanently installed.

• High output
• It makes you able to run AC and other high-power appliances
• Great for redundancy and off-grid living
• Require fuel and maintenance
• Generators can be expensive

Solar Panels

Solar panels are great and can give you significant amounts of energy, especially when sailing in tropical and sunny climates. They require some space and careful placement to be efficient, as shading significantly reduces their output. And on a sailboat, many things can give shade, especially the mast and our rigging.

A common practice is placing solar panels on top of the sprayhood, bimini, or on a separate solar arch on the back of the boat. You can, of course, do a combination and even use flexible panels on the front deck.

I have also seen many people mounting panels on the sides of the boat with a mechanism to flip them up to face the sun when needed. You need additional solar chargers to feed electricity from the solar panels to the batteries, and the best option here is to use MPPT chargers.

• Modern panels are highly efficient
• If you have enough space for it, you can rely purely on solar in a sunny climate
• Require very little maintenance
• 100% renewable energy
• It pairs exceptionally well with lithium batteries
• Solar panels and chargers are reasonably priced compared to the other options
• Prone to shading
• Not efficient in areas with less sunlight
• They take up significant space on the boat

Wind Generator

Wind generators can be great if you sail in a windy area like the Caribbean . They can constantly run 24/7 as long as there are sufficient winds, which can be very helpful. Especially at night when solar panels won’t give you any output, and you don’t want to run the engine or generator to wake up everyone on the boat.

However, they won’t give you high power output and may not cover your needs unless you use electricity sparely. They can be great if you have the space to mount one or two in addition to another source. Just make sure not to mount them in a way that can shade the solar panels.

DuoGen makes a hybrid that can work as wind and hydro generator, which can be a good option for many, but they start at a relatively high price.

• A steady supply of power in windy areas
• Suitable for supplying electricity at night
• Reasonably priced
• Not efficient without wind
• It takes up significant space on the boat
• It may be difficult to mount in combination with solar panels when you want to avoid shading

A hydro generator generates power through its propeller when dragged through the water. Hydro generators often look like a small outboard engine mounted on the back of a sailboat, but you can also get them in variations that can be permanently installed underwater.

The hydro generator will generate electricity as long as the boat moves through the water, but not when you are at anchor. You can typically expect an output of around 10A when sailing, which can be very helpful underway.

If you spend a lot of time at anchor, as most cruisers do, your best bet is probably to combine the hydro generator with another source like solar or wind generation.

• A steady supply of power underway
• Require little maintenance
• Only work underway
• Most models take up significant space on the back of the boat
• Hydro generators are expensive

A less popular source of electricity is the methanol fuel cell. It uses a chemical process to generate energy that requires methanol as fuel. They usually come as standalone units and are simple to install, but the output is relatively low compared to some of our other alternatives.

Another thing to consider is the need to carry methanol fuel onboard, which is highly flammable. Some people like them a lot because they don’t make any noise, can be placed anywhere, and require little maintenance. There are also fuel cells that run on propane instead of methanol.

• Works in any conditions
• Easy to install
• You need highly flammable fuel to run it
• Fuel cells are expensive

Final Words

Everyone has different needs onboard their sailboats regarding how much energy they require to run their electric equipment. Especially cruisers and liveaboards have relatively high energy demands to keep the electronics alive, and relying on the standard alternator isn’t feasible.

From my experience, solar panels are the way to go if you intend to sail in sunny climates, and many cruisers seem to agree. The sun is an infinite source of green energy, and given that you can fit enough panels, they will be able to supply all the renewable power you want.

I have two 285W solar panels hooked up to a 50A MPPT charger, and I easily get 25-50A of power on a good sunny day, enough to leave my lithium batteries topped up by mid-day.

Solar panels often overperform way above their stated output, as seen in the solar charger dashboard in the picture below.

Combine solar with another source, and you have great redundancy for cloudy days. I am very skeptical about fuel cells, however. Still, technology is moving forward rapidly, and I think we will start to see hydrogen fuel cells becoming feasible in the future, which is exciting!

I am curious to know, how do you supply your sailboat with electricity? Leave a comment below!

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Skipper, Electrician and ROV Pilot

Robin is the founder and owner of Sailing Ellidah and has been living on his sailboat since 2019. He is currently on a journey to sail around the world and is passionate about writing his story and helpful content to inspire others who share his interest in sailing.

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