Harnessing Nature: Sailboat Wind & Water Turbine Generators

In a Nutshell...

If you're a sailor looking to generate power on board, you've got two great options to tap into nature's power: a wind generator or a towed water turbine. A wind generator is a fantastic choice for generating consistent amps when you're at anchor or sailing in beam winds, thanks to its ability to harness the apparent wind. However, for those long downwind passages, a water turbine towed behind the boat will really come into its own, providing a steady charge when the apparent wind is low. The best choice for your boat will come down to your sailing style, your typical cruising grounds, and whether you prioritise power output, noise levels, or a combination of the two.

The Appeal of Wind Generators
Types of Wind Generators & How They Perform
The Drawbacks & Challenges of Wind Generators
Towed Water Turbine Generators
Combined Wind & Water Generators
Comparing Wind & Water with Other Power Sources
Summing Up
Frequently Asked Questions

As an experienced ocean sailor, I can tell you that keeping the battery bank topped up is a constant consideration, whether you're at anchor or on passage. While solar panels have become incredibly popular, they're not always the best solution. When the sun goes down or the weather turns grey, you need an alternative.

This is where sailboat wind generators and water turbines come in. They provide a reliable, sustainable way to generate the amps you need to run essential systems like your autopilot, fridge, and lights, without having to fire up the engine.

The Appeal of Wind Generators

A sailboat wind generator, also known as a wind turbine or wind charger, is a brilliant way to add power to your battery bank. The more wind you have—up to a point—the more amps you'll generate. The key thing to remember is that these units respond to the apparent wind, not the true wind.

This is a crucial distinction. For example, on a long downwind tradewind crossing, with the wind astern, your wind generator's performance will likely be disappointing. With a 15-knot following wind and a boat speed of 6 knots, the resulting 9 knots of apparent wind blowing through the blades simply won't be enough for it to earn its keep.

However, once you've made your Caribbean landfall and are cruising in the West Indies, it's a completely different story. With consistent beam winds and breezy anchorages, your wind generator will provide a generous and consistent charge.

Types of Wind Generators & How They Perform

The power from these turbines is created by spinning a DC generator or, more commonly, a 3-phase AC alternator that uses an internal rectifier to convert AC to DC. The most common types are classified by their blade configuration.

Blade Type	Performance	Noise & Vibration	Ideal For
2-Bladed	Excels in lower wind speeds; uses a DC generator.	Produces a low-frequency 'whump whump' sound.	Sailors in light-wind areas.
3-Bladed	High-performance in stronger wind conditions; lower starting torque.	Can produce a penetrating, high-pitched howl.	Cruisers in areas with consistent, strong winds.
5-Bladed	Designed for efficiency in lower wind speeds; higher starting torque.	Significantly quieter due to lower tip speed.	Sailors prioritising a tranquil onboard experience.

When choosing between a 3-bladed and a 5-bladed turbine, you'll need to think about your sailing habits. If your sailing grounds are known for consistently strong winds, a 3-bladed turbine might be the more efficient choice. However, if you spend most of your time in areas with lighter, more variable winds, a 5-bladed turbine will likely prove more effective.

The noise factor is a huge consideration, particularly on extended voyages or when anchored. While manufacturers are constantly improving blade design and using lightweight materials to combat this, the higher tip speed of 3-bladed turbines still makes them noisier than their 5-bladed counterparts.

3 blades, high power and no shortage of noise

5 blades, less power but quieter

On the Water...

We invested in a 3-bladed wind turbine so that we could keep the batteries topped up (and the fridge working) after the solar panels retired for the day. The turbine produced a prodigous quantity of amps, but if we wanted any sleep at night we had to turn it off. Oh well...

The Drawbacks & Challenges of Wind Generators

While the idea of harnessing the wind for power is appealing, wind turbines on sailboats come with a set of challenges that are important to consider before buying one.

Noise & Vibration: As the blades spin to generate electricity, they create sounds that can range from a gentle hum to an intrusive whirring, particularly at higher wind speeds. This noise can be a significant nuisance in a quiet anchorage and can even affect neighbouring vessels. In addition, the turbine's rotation introduces vibrations that resonate through the boat, leading to mechanical wear over time.

Variable Energy Production: Wind is an inherently unpredictable resource. In light winds or during periods of calm weather, the turbine's output diminishes significantly, meaning you can't rely on it as a sole power source. This inconsistency necessitates a backup or supplementary charging method, such as solar panels or your engine.

Installation & Safety: Installing a wind turbine is not a simple task. It must be mounted high enough to get clear wind flow without interfering with rigging, and the spinning blades pose a physical hazard to anyone on deck. Proper placement and a secure mounting are crucial to prevent injury or damage.

Maintenance & Durability: Unlike passive energy solutions like solar panels, wind turbines have numerous moving parts that are subject to wear and tear. Bearings, blades, and electrical components all require regular inspection and maintenance, especially in the corrosive marine environment.

Weight & Aesthetics: A wind generator mounted on a pole or mast can alter the boat's weight distribution, affecting stability and handling. From an aesthetic point of view, it changes the visual profile of your vessel, which may be a concern for those who prefer the traditional, uncluttered look of a sailing yacht.

On the Water...

It was in the article about Solar Panels that I first introduced you to "Bird", the Brown Booby that shared most of an Atlantic crossing with us. Not content with spraying the panels with shame and derision, he turned his attention to the wind turbine. We had to tie it off (the wind turbine, not Bird) if a colourful accident were to be avoided. Perhaps he didn't like the noise, but he was entirely responsible for the engine having to run an hour each day.

"Bird", the Brown Booby the uninvited guest that styed with us most of the way across the Atlantic

Yelling " Duck, Bird!" only confused him...

Incidentally, if you'd like to hear more of Bird's exploits, take a look at Mary's eBook "First Time Atlantic Crossing".

Towed Water Turbine Generators

A towed generator, also called a water turbine, is a brilliant alternative, or even a complement, to a wind generator. The system consists of an impeller towed behind the boat on a 20-30m rotating towline, which connects to a generator mounted on the pulpit. A cable then delivers the charge to the batteries.

Their major advantage is that they really score over their wind-driven brethren in light wind conditions or on long downwind passages. In these situations, where a wind generator would be struggling with low apparent wind, a towed generator will continue to churn out a consistent charge, typically producing around 5 amps at 6 knots of boat speed.

However, towed generators have their own set of challenges:

Drag: A towed generator will typically take between a third and half a knot off your boat speed.

Speed Limitations: At speeds much above 7 knots, the impeller tends to skip along the surface, generating nothing but frustration. You can compensate for this by adding sinker weights or using a longer towline.

Heavy Seas: In a big sea, the impeller can leap out of the water, and the spinning towline is likely to snarl into an impressive mess of kinks and twists.

Safety & Interference: Be aware of sharks! They have been known to consider the spinning impeller a potential meal. And don't even think about trolling a fishing line when you're towing one of these; the resulting tangle has to be seen to be believed.

Combined Wind & Water Generators

Towed generators aren't much use at anchor. Some clever manufacturers have addressed this by making units that can be converted from water to wind mode and vice-versa. The Aquair 100 is a classic example of this type of unit, once favoured by many long-distance sailors.

Eclectic Energy took this concept a step further with the DuoGen combined wind/water generator. Unlike a towed unit, this is a one-piece design that is permanently attached to the transom. You simply swing it down into your stern wave to use it as a water turbine, or swing it up to use it as a wind charger when at anchor. It's a really neat and innovative idea that provides the best of both worlds.

Comparing Wind & Water with Other Power Sources

While wind and water generators are fantastic for certain situations, it's essential to understand how they stack up against the other common methods of generating power on board as part of a complete Marine Electrical Systems: A Sailor's Guide to 12V Electrics strategy.

Solar Power: Solar panels are a sailor's best friend in sunny climes. They're completely silent, require virtually no maintenance, and are highly efficient on deck or a hard bimini. However, they need direct sunlight to produce power and are useless at night or on overcast days. A large array can also take up a lot of valuable deck space.

Engine Alternators: Every boat has a main engine alternator, making it the default option. While it provides a high output, it's an incredibly inefficient and noisy way to charge batteries. You're running a powerful engine just to spin a small alternator, which is a massive waste of fuel and a source of unnecessary noise and vibration. It's best reserved for emergencies or short bursts of charging.

Fuel Generators: For yachts with high power demands, a dedicated diesel or petrol generator is a common solution. These units provide a massive and reliable power output, capable of running everything from air conditioning to water makers. Their primary drawbacks are the noise, ongoing maintenance, and the need to carry and burn fossil fuels, which goes against the ethos of green cruising.

Hybrid Systems: The most effective and reliable solution for a cruising sailboat is a hybrid power system. By combining different technologies, you can overcome the individual weaknesses of each. For example, a solar panel array paired with a wind generator gives you power in both sunny and windy conditions, day or night. Adding a towed water turbine to the mix ensures you have a consistent charge on long passages when the wind might be light.

Summing Up

When you get right down to it, the choice of power generation—or the combination of them—is a personal one that depends entirely on your sailing style and where you plan to sail. While wind generators are fantastic for anchoring and cruising in areas with strong, consistent breezes, they can be inefficient on downwind passages. This is where a towed water turbine or a combined unit like the DuoGen really shines, providing a steady stream of power while underway. Ultimately, the best solution for most sailors is a hybrid approach that leverages the strengths of multiple systems, allowing you to achieve true energy independence on board without the constant worry of a flat battery.

This article was written by Dick McClary, RYA Yachtmaster and author of 'Offshore Sailing' published by the Royal Yachting Association ( RYA) and member of The Yachting Journalists Association (YJA).

Frequently Asked Questions

Q1: How do I know if a wind generator is right for my boat?

A wind generator is a great fit if you spend a lot of time on anchor or sail in areas with consistent wind. If your sailing is primarily downwind or in light-air regions like the Mediterranean, a water turbine or solar panels might be a more effective option.

Q2: What's the main disadvantage of a wind generator?

Noise is the most common complaint from sailors. While modern designs have improved, the high tip speed of the blades can produce an audible howl or hum, which can be a real nuisance, especially at anchor.

Q3: Do water turbines significantly slow down the boat?

A well-designed water turbine, like the Watt&Sea or a similar unit, causes minimal drag. For most cruising yachts, the speed reduction is typically less than half a knot, which is a small price to pay for a constant, reliable charge on passage.

Q4: Are combined wind/water generators more expensive?

Yes, combined units like the DuoGen are generally more expensive due to their complex design and dual functionality. However, for a long-distance cruising sailor, the ability to generate power in almost any condition makes them a worthwhile investment.

Q5: Can I run a wind generator and a solar panel at the same time?

Absolutely. Many sailors combine wind and solar power with a hybrid charge controller to create a highly efficient, redundant charging system. Solar works best in bright sunlight, while a wind generator can be active day and night.