Modern voyaging yachts are increasingly evolving into what I refer to as “floating power grids,” motor-sailing craft on which skippers and their crews enjoy push-button control of everything from navigation systems and communications, to deck winches and roller furlers. With the inevitably continuing rise in fuel prices, though, most cruisers are also trying to constrain their use of fossil fuels while at the same time reducing wear and tear on their main power plants and gensets.
Alternative energy, provided by solar panels, wind generators, and towed water generators, can usually keep up with the battery charging requirements of most yachts. In becalmed conditions offshore, neither the wind turbine nor the water turbine is of any use, so we depend on the solar panels — and aye, ye olde iron jib. But when the wind is up, whether under sail or at anchor, the mechanical power available from either the air or the water can be a dauntingly powerful charging source.
Before we embark on the specifics of voltage regulators, controllers, and monitoring systems, let’s review our charging needs and power sources. The obvious rule here is, the bigger the boat, the more electrical amenities likely to be installed, and thus the bigger the battery banks and the more powerful and varied the charging systems — up to a point.
At the top of the spectrum, vessels in excess of 50 feet in length overall (LOA) typically consume upwards of 200 amp hours per day to keep up with a multi-function navigation display, radar, autopilot, watermaker, refrigerator and freezer, electric toilet, and pressurized hot and cold water. Battery storage of at least 1,000 reserve amps is not unusual on these vessels.
Most of these large vessels carry a small diesel generator to ensure a consistent source of power, not only for the highly complex array of 12 or 24-volt DC electronics, but also for appliances requiring 110 or 220 volts AC.
The bulk of the world’s voyaging fleet is comprised of vessels measuring approximately 32 to 50 feet LOA. They generally feature a refrigerator and a ham or marine SSB radio, plus an array of electronic navigation systems, which together deplete a battery bank quickly under normal voyaging conditions. Power consumption on these vessels varies anywhere from 40 to 100 amp hours per day, and reserve battery power ranges from 200 to 600 amps.
This vast middle is where we see the greatest abundance and variety of solar panels and generator turbines powered by air or water. Owners of these yachts are still mindful of their pocketbooks and fuel storage capacity, yet they still expect a comfortable lifestyle well above that found on the floating pup tents at the low end of the voyaging yacht scale. The “middle class” of the voyaging fleet are therefore the greatest users of alternative power and the target market of manufacturers of alternative charging systems.
At the bottom of the food chain are the pocket cruisers, most of which fall in the range of 25 to 31 feet. Their intrepid skippers generally keep power usage to the absolute minimum, foregoing refrigeration, a watermaker, plasma television, Jacuzzi, and so on. The engine alternator and perhaps one or two 36-watt solar panels keep up with a small GPS, a VHF radio and an HF SSB, as long as it is used sparingly. During a five-year circumnavigation aboard my 1966 Cal 30 Saltaire, I generally kept power usage below 10 amp hours per day, depending on a 55-amp alternator and a single 36-watt Siemens solar panel to keep up with my paltry demand for reserve amperage. I employed a windvane for self-steering, stored fresh water in jerry cans strapped to the cabin coaming, and rarely used the running lights. This formula continues to yield a rough, yet wonderfully simple, lifestyle on the water.
If we are to encounter but one form of alternative power on a small yacht, it is the ubiquitous solar panel, silently doing its job whenever the sun shines. A dependable way of estimating solar charge output in the tropics is to divide the rated amperage in half and then multiply by 10 hours of steady, direct sunshine. If you have a 36-watt panel, the 3-amp output becomes 1.5 amps, and multiplying that by 10 gives us 15 amp hours. Using this formula, two 50-watt panels yield roughly 42 amp hours on a good day. Again, that’s more than four times Saltaire’s diet under voyaging conditions, but shy of a typical cruising vessel’s daily power consumption. Nonetheless, the panels still contribute a healthy share of a multi-source charging system.
Siemens, now owned by Shell Solar, has been a leading manufacturer of marine solar panels for decades. The panels are still built with tough, anodized aluminum framing and can be expected to last at least a generation. With 35,000 nautical miles of ocean sailing and endless dousing in saltwater over the past 10 years, the 36-watt Siemens panel on Saltaire still looks and performs like new.
Sunsei is another prominent player in the marine solar business. Its largest panel is rated at 130 watts with a daily output of 32 to 40 amp hours. All that power within a space of 60.24 x 28 inches. A pair of these panels could easily find a home atop an arch on a vessel of more than 35 feet.
Uni-Solar and Spectra offer flexible panels, a handy alternative for affixing to cabin tops or mainsail booms. Uni-Solar’s panels may be rolled up for storage and also offer the benefit of lower prices. Spectra produces three semi-flexible panels of 5, 10, and 20 watts respectively. These panels won’t keep up with the demanding daily regimen of a cruising yacht, but are effective as trickle chargers for weekend boats. One big benefit of low-output panels is that they usually do not require a voltage regulator or controller.
The underlying theory behind wind generator output is that power increases as the cube of wind speed. For example, a 5-knot breeze produces 125 units of power; by doubling the speed to 10 knots, the wind now yields 1,000 units of power. At 20 knots, we have 8,000 units, and so on. The various units available on the market vary significantly in their ranges of power, but most of them are capable of generating so much that they need to be shut off, or reefed, when their speed becomes excessive and output is beyond what the battery banks require. A few models, such as the Air X from Southwest Windpower in Flagstaff, Ariz., are designed to feather the pitch of their rotors once a certain maximum speed is reached. This protects the built-in alternator from excess wear and the battery bank from excess power output.
Other leading wind generator manufacturers include Ampair, KISS, Red Baron, and Marlec/Rutland. At the high end of the output scale are the Red Baron and Kiss, both kicking out 18 amps at a wind speed of 20 knots. That’s a sizzling amount of power, more than many yachts will require. Of course, the units can be reefed in high winds to prevent overcharging and inflicting damage to the rotors.
At the low end of the scale is the Rutland 913, yielding only 6 amps at 20 knots. High output, though, is not the only factor to consider when shopping for a wind generator. If your battery banks and onboard systems require an aggressive charging system, then buy the bigger machine. If you are combining the wind generator with large solar panels, then the Rutland 913, or the mid-range output of the Air X or Ampair (both producing 12 amps at 20 knots), may be more appropriate.
Other features, such as controller options, durability, warranty, weight, installation gear, etc., may also influence your selection. For more information on wind generators, see “Power plucked from the air,” Ocean Navigator, May/June 2007 and “Installing a wind generator,” Ocean Voyager, 2008.
With all the daunting, untapped power of rushing water under our hulls, it is a wonder there are so few manufacturers producing water generators for sailing craft and little advertising dedicated to these machines. Their rotors, spinning underwater while connected to a generator or alternator on the taffrail, are a godsend when sailing downwind, because that’s when wind generators are least potent. And since most offshore trade wind sailing is downwind, it makes perfectly good sense to harness power from the boat’s own motion.
Ferris Waterpower manufactures the WP-200 water generator, which is convertible to an air turbine with a separately purchased kit. At 6 knots of vessel speed, Ferris claims its unit produces a whopping 12 amps of power, or approximately 200 amp hours of power per day, more than most voyaging vessels can expect to consume. The WP-200 comes packed with a 30-amp multi-source regulator, an analog ammeter, a 75-foot torque line, and “a retrieval funnel to stop the unit underway.” An 85-watt solar panel is also available to round out the go-anywhere alternative energy charging system. Other separately sold accessories include mounting poles and a rigging mount system for the wind generator configuration.
The Aqua4gen, by LVM Products, is another model easily convertible to a wind generator. LVM claims a respectable 8 amps of power at a 6-knot vessel speed, with 30 pounds of drag. Dick Verbeck of Southern California says when the Red Baron on his Bruce Roberts 34 Beatitude is configured as a water generator, it produces similar output, about 8 amps at a 6-knot boat speed.
The drag question is the most talked-about drawback of water generators. Though it is not as bad as towing a drogue, losing 1 to 1.5 knots of vessel speed does add up. On the other hand, because of the significantly greater power generated by water as compared to wind, a water propeller’s motion can fulfill most vessels’ daily charging needs in a matter of hours.
Let’s compare some numbers. Sailing downwind in the trades in a fresh breeze of 18 knots, a boat measuring 36 feet on the waterline can expect to maintain a theoretical hull speed of 9 knots, leaving 9 knots of apparent wind blowing over the transom. At 9 knots wind speed, the Air X wind generator produces less than 2 amps. At the other end of the scale, the Red Baron wind generator configuration produces about 5 amps.
Assuming the same true wind speed of 18 knots while towing a submerged water generator turbine downwind, we now have a vessel speed of about 8 knots if we subtract a knot (could be more) for drag. At this vessel speed, the Aqua4gen and the Red Baron in water generator mode crank out a respectable 11 amps. At the same velocity, the Ferris WP-200 whips out a scorching 20 amps of direct current, or 480 amp hours (5.76 kilowatts) per day.
Combining charge sources
Introducing electrical current to the same set of battery banks from a multitude of sources can easily lead to overcharging in an unregulated electrical system. Imagine a 150-amp engine alternator, a 20-amp water generator, and a 4-amp solar panel array all rushing simultaneously to nourish a 600-amp battery bank. Assuming at least a 75 percent initial battery charge, we can expect that bank to start frying in well under an hour. Hence the need for one or more battery-sensing controllers or regulators.
Something else to watch for is a powerful surge from the engine alternator running back through, say, your solar panel circuit, burning out the controller. More than one sailor has been alarmed at the sight of noxious fumes spewing from an unprotected controller when cranking up the engine. A switch, fuse, or protective diode between the battery and the controller will protect the controller from premature demise.
Pre-regulating a wind generator that uses electronic self-braking technology, such as that found in Southwest Windpower’s Air X, is another potential complication when the unit is coupled with multiple charging sources. The Air X’s internal controller dampens the turbine to a slow spin when the battery has reached its full charge, or when wind speeds reach light gale force. If the battery is receiving a charge from more than one source at the same time, the Air X may read the other input current as battery charge and prematurely drop to a slow spin, having been pre-regulated by the interfering charge. Fortunately, this causes no harm to the Air X’s alternator or controller. The company cautions the user to “test the possible interference by disconnecting the other charge sources to determine the possible interference source.” The easiest solution to pre-regulation is to run all sources, minus the engine alternator, through separate switches so that the operator may select inputs manually.
Regulators and controllers
The traditional shunt regulator, which uses heat dissipation to discard excess charging amperage, still has its place in a charging circuit. Commonly employing a flanged aluminum casing to dissipate heat from overcharging, it can handle most alternative power generating inputs without overloading itself. The one major limitation of shunt regulators is their relatively low amperage ratings, relegating these devices, in most cases, to a single charge source.
The modern “smart” controller uses a microprocessor to manage one or more charge sources, each one varying within a permissible range of voltage and a wide range of amperage. If you are considering an off-the-shelf controller that did not come as part of the installation kit with your charging source, make sure the controller is rated for the maximum output of the charging device. Some controllers, such as those from Sunsei, are designed strictly for solar panels, which generally produce less amperage than generators and alternators and do not impose the powerful surges generated by these aggressive mechanisms.
Sunsei offers off-the-rack controllers adaptable to most charging configurations. A 10-amp CC10000 Sunsei controller, which fits in the palm of your hand, controls the solar panel on Saltaire 24 hours a day, preventing overcharge during the day and discharge at night. The Sunsei CC25000 25-amp controller handles combined input from up to three solar panels. Both units employ a diode to prevent battery discharge at night.
The most logical way to manage multiple charging sources is to combine them in one controller. SES Flexcharge USA offers a robust device called the NC25A Ultra High Efficiency 25 Ampere Solar and Wind System Charging System Controller. The diminutive NC25A combines alternative energy charging systems from 0.1-amp to 25 amps and is expandable to 35, 60 or 100 amps for larger charging systems.
Flexcharge claims an incredible 99.9 percent efficiency rate for the NC25A. The controller adjusts itself commensurately with minute changes in charge demanded by the dual battery banks rather than shifting through the standard bulk, taper and float charge levels of most charging regulators.
When batteries have reached their full charge, the NC25A diverts excess charging energy to other tasks, such as refrigeration or a water heater, or back to a permanent magnet charging source, such as a wind generator, in order to dissipate energy and, in this case, to reduce turbine speed in high wind conditions.
The final step in building your alternative energy charging system is selecting a charge monitoring device. The new Xantrex Technology LinkPRO and LinkLITE indicate charge source output and battery charge for a dual battery bank, letting you “read your battery bank like a fuel gauge.” The LinkPRO, the direct replacement for the old XBM battery monitor, handles up to 10,000 amps of direct current and monitors two battery charges simultaneously. The lower-priced LinkLITE is rated at 1,000 amps.
Both monitors display voltage, amps, consumed amp hours, remaining charge, and time remaining in the battery bank. The two units also feature a 500-amp shunt, adding to their flexibility in a multi-source charging system. Unlike the larger rectangular footprint of the Xantrex Link 2000, both new monitors are encased in a round bezel.
“These battery monitors expand and improve our mobile product line,” said John Wallace, Xantrex CEO. “Versatile products like the Xantrex LinkLITE and LinkPRO are designed to give users peace of mind, knowing that they count on our reliable battery monitors to consistently deliver accurate data.”
Aside from electronic monitoring, wise sailors develop an energy plan, periodically documenting water and fuel consumption, battery usage per fixture, and daily charge output per source. This can be as simple as a handwritten list, or a full-blown spreadsheet on your laptop. Crossing oceans is a lot more fun and fulfilling if you keep close tabs on your onboard resources and take proper measures to use them judiciously.
—Bill Morris completed a circumnavigation, two-thirds single-handed, via the Suez and Panama canals aboard his 1966 Cal 30 Saltaire. He believes the main reason for the success of the voyage was his preference for manual systems wherever practical, and dependence on alternative energy to power a minimal array of essential electronics. Morris’ first book, The Windvane Self-Steering Handbook, was published by International Marine in March 2004.