Bristol 27

Generators

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Research

• Evaluate your sailing patterns, consider the geographical regions through which you’ll be sailing and then assess the different products.  (Upgrading the Cruising Sailboat, p. 242)
• Power tools...can make life aboard easier, but almost all require 100V alternating current (AC). If these are required items on your boat, you have essentially four choices: 1) carry an auxiliary or portable AC generator that is run by gasoline or diesel fuel 2) Install an inverter to make AC out of your DC engine battery 3) Install an engine driven AC alternator 4) install an AC electric generator that runs off battery or DC power source.  (Upgrading the Cruising Sailboat, p. 244)
• Solar, wind and water generators are no more difficult to install than a car stereo; only basic tools and attention to instructions are required. On the other hand, auxiliary generators and high powered AC alternators may require custom metal mounting brackets. And the wiring of a 100V system should adhere to ABYC specifications.  (Upgrading the Cruising Sailboat, p. 253)
• The type of cruising you do is a major factor in choosing your power-generating equipment. For many cruisers, the majority of time is spent at anchor, with intermittent passages ranging from one day to several weeks….The key to your decision will in part be affected by possible mounting sites for each of the three types. If you’ve got no place to mount a solar panel or wind generator, consider something else. Achieving independence afloat is one of the true joys of the cruising life, and making your own electrical power is at the very heart of this independence.  (Upgrading the Cruising Sailboat, p. 256 – 7)
• Engine-running time for battery charging alone can be significantly reduced – and sometimes eliminated altogether – through the judicious use of solar panels and or a wind generator…sometimes enough to sustain the dc system for extended periods. However, with this type of regimen, the batteries almost certainly will never be fully recharged – they are, in effect, cycled daily from about 80% of full charge to 50% and back to 80% again. This situation carries with it the risk of long-term battery damage through a process known as sulfation. To prevent sulfation, the batteries periodically need to be brought to a state of full charge, either by running the engine for several hours (ideally, when motor sailing so the engine does not have to run solely for battery charging) or by plugging a battery charger into shore power when it is available.  (Cruising Handbook, p. 166)
• The batteries also must be fully charged periodically when a boat is not in use because all batteries slowly discharge when left idle; if left alone, they eventually suffer irreparable damage through sulfation. Wet cells discharge considerably faster than gel cells or AGMs and, therefore, are at greater risk.  (Cruising Handbook, p. 167)
• I don’t like to leave our boat plugged in [to shore power] for extended periods because there is a risk of corrosion that comes with a shore-power connection….after fully charging our batteries…we use solar panels to keep the batteries in a state of full charge when we are not on the boat.  (Cruising Handbook, p. 167)

Alternator

Fuel Generator

• As you compare data on generator output, keep in mind that resistance (level of battery charge) affects generator output. As a battery charges, generator output decreases. So, if an advertisement claims that Brand X puts out 6 amps, try to determine if this measurement was obtained with a dead battery, half-charged battery, etc. There is no standard for such measurements that I’m aware of….You may keep your batteries charged higher than the level used during testing, or the manufacturer may have taken statistical liberties that distorted the unit’s performance.  (Upgrading the Cruising Sailboat, p. 242)
• Danny Greene carries a portable Honda generator with him on his 26’ cutter. When the impulse strikes him, in the cockpit or on the beach, he can knock together a new dinghy design with the aid of a power drill and saber saw powered by his hand-carried generator.  (Upgrading the Cruising Sailboat, p. 244)

Inverter

• An inverter, while small compared to a fuel powered generator, can do some of the same things, but not all. hooked up to the batteries it can convert their DC voltage to 110V AC – the net result is the same as the AC fuel-powered generator – it’s simply a different means to the same end. However, an inverter won’t recharge your battery, and at least 20% of the available power is lost between the source and appliance.  (Upgrading the Cruising Sailboat, p. 244 – 5)
• Some household tools and appliances are not designed for operation with the square wave generated by inverters. Check appliances to determine whether they will work on square waves as well as conventional sine waves. The Heath Company advises customers that incandescent lamps, electric shavers, soldering irons and “other devices that present a resistive or small inductive load” work well with inverters. Problems may be experienced with radios, TV’s (which may hum or buzz), C.B’s, tape recorders and electric drills (which may fail to start).   (Upgrading the Cruising Sailboat, p. 245)
• An inverter must be sized for both the highest AC load it is to carry and for the DC system that is to power it. On the AC side, load calculations are simple….[see page 159 table to calculate]…Now determine which appliances are likely to be used simultaneously to discover the maximum AC demand at any given time. The inverter must be sized to match or exceed this demand. Although many appliances momentarily draw several times their running load when they first kick on, if the inverter is sized…it should have an adequate surge capability to meet any temporary demand…On the DC side, the interest is not so much in the peak demand as in the total drain on batteries between full charges…limiting factor…not the ability of the inverter to power the AC appliances, but rather the ability of the DC system to power the inverter.  (Cruising Handbook, p. 171)
• Some inverters produce AC output as what is called a modified sine wave, others as a pure sine wave. The former is generally cheaper and with a lower idle drain (the power consumed when an inverter is turned “on” but not in use), but is also heavier and bulkier. It works well on most loads, but [may not work well with heavier loads].  (Cruising Handbook, p. 171)
• When it comes to installing an inverter, one of the more difficult decisions is where to put it, with three potentially contradictory factors at work:  (Cruising Handbook, p. 172)

1. The inverter should be as close as possible to its batteries (to minimize the lengths of the DC cables)
2. It needs to be in a cool area with a good airflow over the unit (i.e., not in the engine compartment). Keeping it cool is necessary because an inverter’s overall performance is linked to its temperature; elevated temperatures lead to accelerated electronic-component failure.
3. It must be kept dry and protected from spray or condensation because an inverter is a complex electronic device, incorporating different metals. If moisture is added, we have all the ingredients – water, DC electricity and dissmilar metals – for destructive galvanic and stray-current corrosion.

• To assist in the cooling process, an inverter should have a temperature activated fan…if the chosen location is not readily accessible, it is well worth investing in a remote monitoring and control panel (an option with most inverters). With the remote panel, it is easy to turn the inverter off when it is not needed.  (Cruising Handbook, p. 172)
• Because of the very high loads that an inverter can impose on a DC system, its DC cables have to be large and short to minimize power robbing voltage drops in them. In typical circumstances, inverter cables should not exceed 10’ in length, even with this short distance, a 2,500 watt inverter needs cables of approximately 2/0 gauge or larger (about as big as your thumb).  (Cruising Handbook, 173)
• It is essential to fit a fuse or circuit breaker as close as possible to the positive terminal of the battery. A 2,500-watt inverter needs a fuse or circuit breaker on the order of 250 amps; as a general rule on a 12V system, the fuse should have a rating in amps approximately 10% of the rating in watts of the inverter.  (Cruising Handbook, p. 173)
• …many inverters have a sleep mode, in which the inverter’s AC output is reduced to a very low level when there is no load on it….if the AC circuit is bridge, the inverter jumps to full output – quite possibly electrocuting [a] troubleshooter. To deal with this problem – although it is rarely done – I consider it essential to fit an isolation switch or breaker in the DC positive feed to all inverters so that the inverter can be fully disabled before any circuits are worked on. A 2,500-watt, 12 inverter needs a switch or circuit breaker with a continuous current rating of 250 amps or more.  (Cruising Handbook, p. 173)
• AC power can be lethal…under no circumstances must it be possible to bring an inverter and another source of AC power online at the same time. Instant catastrophic damage is likely to occur to the inverter. To avoid such a possibility, a couple of different wiring options are commonly used. The first routes all the boat’s AC inputs (the shore-power supply, any AC generator, and the inverter) through a selector switch that only allows one AC source at a time to be connected to the boat’s circuits. The second uses an automatic transfer switch inside the inverter; the shore-power input (and any AC generator output) is routed through the inverter, which senses whenever another source of AC power comes online, automatically switching itself off.  (Cruising Handbook, p. 173)
• Sometimes boats with an inverter have loads that are too heavy for the inverter to handle or should not be fed from the inverter (e.g., a battery charger; if a battery charger is powered by an inverter, we get into a loop in which the inverter is feeding the battery charger, which is charging the batteries supplying the inverter, with power losses at every stage of the process). In this case, a subsidiary AC distribution panel is needed for the inverter-based loads, with the non-inverter loads tied into the main panel in such a way that they cannot be fed by the inverter.  (Cruising Handbook, p. 173)
• …for safety reasons….when an inverter is supplying AC power to the boat’s circuits, the neutral and ground sides of the inverter’s AC output should be internally connected – but when the inverter is switched out of the C circuits, this connection should be broken. Inverters designed for the marine market do this automatically; some designed for other markets do not.  (Cruising Handbook, p. 173)

Manual Generator

• For those who want to recharge their 12V batteries and get a little exercise at the same time, there is a Wesson Pedal Power generator. It only measures 10” x 15” x 17”, weights 22 lbs. and is modestly priced…the inventor says he can get 6 hours of light from one hour of pedaling…the device can be stored inside and doesn’t rely on any other power source than his own legs, it’s a nifty way to keep the batteries topped off.  (Upgrading the Cruising Sailboat, p. 246 – 7)

Solar Generator

• A solar panel advertised as producing, say 30 – 35 amp-hours per week, is only producing about 60 milliamps (8 hours of sunshine x 7 days = 56 sunlit hour; 56 x 600 ma = 36,000 ma, or 33.6 amp hours each week). Also, panels are usually rated at peak efficiency, 90 degrees to a bright sun, and obviously such a condition is likely the exception rather than the rule…The percentage of clear days can help you determine the practicality of solar panels, and this, of course, varies around the world.  (Upgrading the Cruising Sailboat, p. 242)
• The solar cell is a semi-conductor device that converts light energy directly into electrical energy. Silicon solar cells are made by doping silicon crystals with other chemicals. When phosphorus is added during the growth of the crystal, the silicon develops negatively charged electrons; when boron is added, positively charged carries appear. The crystals are then sliced into wafers. Incoming light particles called photons are absorbed by the electrons within the silicon wafer and create both positive and negative charges. A photocurrent flows, voltage develops and electricity is produced. All silicon solar cells produce the same amount of voltage – about 0.5V – so many of them are used in series to produce an amount of electricity sufficient to be used in charging batteries. The more solar cells, the bigger the panel, the more output obtained.  (Upgrading the Cruising Sailboat, p. 250)
• Panel temperature affects output, both extreme heat and cold. Providing ventilation space behind the panel to keep it cool in hot weather is a good idea…Mounting the panels so they can be adjusted to face the sun directly will increase output, though this is not always feasible, especially on a narrow monohull.  (Upgrading the Cruising Sailboat, p. 251)
• …most panels have blocking diodes that prevent discharge of the battery at night. John Campbell, Caribbean cruiser/boating journalist, says, however, that tests show the amount of current lost by the diode when charging exceeds the amount lost at night when the diode is removed. The main reason diodes are used to prevent current flowing out at night is to save the skipper the trouble of switching off the circuit. So, if one is willing to wire in a switch and merely flip it off at dusk, the diode can be eliminated altogether with no trade-off in current loses.  (Upgrading the Cruising Sailboat, p. 251 – 2)
• Common causes of solar panel failure are breaking or crazing of the glass cover and corrosion of the wires at the solar panel terminals….Corrosion can be partially prevented by using a good quality bedding compound where the wires enter the panel housing, and around the terminals inside the housing. Silicone rubber is okay, but doesn’t adhere well to surrounding surfaces.  (Upgrading the Cruising Sailboat, p. 252, 254)
• See the output tables of fixed versus tilted solar panels in Upgrading the Cruising Sailboat, p. 251, Fig. 12-21.
• The orientation of of the solar panel to the sun directly affects the amount of charge to the battery…solar panels must be rotated..to follow the path of the sun in order to deliver maximum charge. Leaving them flat on deck, as so many cruisers do, means about 35% less charging power.  (Upgrading the Cruising Sailboat, p. 254)
• Because each solar cell is connected in series to the rest, a shadow across only a small part of the panel can reduce output of the array by a significant amount – 80% or more. Therefore, it is necessary to locate the panels where rigging, sails and lifelines aren’t likely to cast their shadows across the panels If mounting in an exposed area, some sort of detachable mount is a good idea for removal when the wind picks up. Once a suitable mounting site is found, the panel can be wired to the battery.  (Upgrading the Cruising Sailboat, p. 254)
• The closer the battery the better, because the longer the connecting wires, the greater the loss of current flowing through them. Insulated wire of at least #18 AG should be used; the farther the distance, the thicker the wire.  (Upgrading the Cruising Sailboat, p. 254)
• If one wire is marked red, or marked with a “+”, it should be taken to the positive terminal on the battery; the other wire is led to negative. If some wires aren’t fitted with terminals, pick up some crimp lug eyes….They are crimped on, and a drop of solder on each ensures a good connection. A plastic heat-drink sleeve protects the joint….Beside a blocking diode on the positive wire, some solar panel manufacturers also advise placing a fuse on the positive side to prevent damage to the panel in the event of shorts. Small in-line fuses are available.  (Upgrading the Cruising Sailboat, p. 255)
• See Upgrading the Cruising Sailboat, p. 255, Fig. 12-27 and 12-28 for solar panel wiring,
• About the only maintenance solar panels require is an occasional washing with a mild detergent and fresh water.  (Upgrading the Cruising Sailboat, p. 255)
• The attractive feature of solar panels is that they are passive – meaning there are no moving parts.  (Upgrading the Cruising Sailboat, p. 257)
• If larger panels are installed…these will do nicely [to keep the battery topped off at 100% when away from the boat] but need their own voltage regulator to avoid overcharging the batteries when there is no load on the system…[a multistep regulator for solar panels]  (Cruising Handbook, p. 167)
• Nontracking solar arrays reach their peak output when the sun is directly overhead. Output drops lightly at first, then dramatically as the sun arcs downward toward the horizon. Total daily output varies with latitude, season, and weather, but even in the best circumstances daily output will rarely exceed five times the rated peak output. In other words we should expect a panel rated at 50 watts to deliver no more than 250 watt-hours of power daily, even during a summer cruise along the Baja, California, coast.  (This Old Boat, p. 295)
• The amount of solar energy available per square meter of surface area is about 1,000 watts. A 12% efficient module 1 square meter in size would yield 120 watt-hours at peak periods, so five times peak gives us a best possible daily output of not more than 600 watt-hours. We convert this to daily amp-hours with our now-familiar power formula (I = P/V). In this case the voltage is rated voltage for the pane, normally around 17 volts. So if we divide 600 watt-hours by 17 volts, we find that under perfect conditions daily output per square meter will not exceed around 35 Ah. To replace 100 Ah of consumption plus 20% battery inefficiency will require more than 3 square meters of solar cells, meaning that you will need to find horizontal space for an array larger than a full 4 x 8 sheet of plywood. Array size is the first problem. The second problem is cost…The current cost of around $ per peak watt makes the panel cost per daily amp-hour capacity around $20. The cost of a solar array capable of handling 100 Ah daily load will exceed $2,000. Old-boat owners (that hyphen is essential) operating on a budget like my own will be hard-pressed to meet all onboard power requirements with solar energy….  (This Old Boat, p. 295)
• In general, stern arches offend my aesthetic sense, spoiling the lines of even the loveliest boats, but for those who are less sensitive, stern arches (and their even uglier and more lubberly cousins, stern davits) do provide an our of the way mounting location for a substantial solar array.  (This Old Boat, p. 296)
• Battery Maintenance – A perfect application for solar power is maintaining the batteries aboard a boat stored on a mooring. A relatively small panel can provide a constant float charge, avoiding harmful self-discharge and prolonging the life of expensive batteries. Surprisingly to some, solar power is also the best way to float the batteries of an idle boat in a marina because it eliminates the risk of stray-current corrosion associated with the constant shore-power connection a battery charger necessitates. You need solar output of around 0.3% of your total battery capacity to float fully charged flooded batteries. That works out to around 5 watts per 100 Ah of battery capacity. Solar charging at a flow level is so healthful that it grants the favored battery seeming immortality…failure to outfit an idle boat with solar charging is just throwing away money.  (This Old Boat, p. 295)
• Solar Cell Types – Of the three types of silicon-based solar cells on the market, single-crystal cells produce the most power in optimum conditions, having an efficiency of around 12%. Multi-crystal cells, which look like shattered blue glass, are less costly and slightly less efficient, but better performance at low sun angles can make their daily output equal to or better than single crystal versions. Amorphous silicon [from calculators] is the cheapest to produce but only about 1/2 as efficient, making the per-watt cost of these panels sometimes higher. Thin film silicon has the admirable characteristic of not being brittle like crystalline cells, so thin film panels can be flexible rather than rigid.
• Solar panels give maximum output when they are perpendicular to the sun’s rays, but since boat movement can make including the panel toward the sun less than a sure thing, fixed mounting should be horizontal. An articulating mount can improve daily output dramatically if you are willing to reorient the panels every hour or so as the sun and boat move. It is also essential to mount solar panels where they will be clear of all shadows. This can be a tall order on a sailboat. Even the seemingly inconsequential shadow cast by a line or wire can have a detrimental effect completely out of proportion to area shaded. This occurs because cells are connected in series, and when one or two cells feel the effect of shade, they quit producing and resist the flow from other cells in the train, effecting a precipitous decline in output. “Shade protection” diodes found in most thin-film solar panels bypass non-producing cells, making the output decline more or less consistent with the relative amount of shadow. This can make thin-film panels a better choice when shadows cannot be avoided. Thin film panels also suffer less from shade caused by cloud cover; in overcast conditions they more outperform the more efficient crystalline modules in total daily output. If you do your boating where daily sunshine is by no means a given, a thin-film panel is likely to be the better choice for battery maintenance duty. Sailors trying to maximize their solar power output will need sunnier climes and should stick to crystal-line panels.  (This Old Boat, p. 297)
• …it is essential to keep solar panels cool. How essential? For every 10F (6C) increase in temperature of the silicon, the cell voltage declines by around 3%. Panel ratings are usually….at 77F (25C) so in the tropics you should expect the true output voltage to be about 15% less than the rating. You cannot prevent the silicon from heating in direct sunlight, but you can avoid a greater voltage decline from heat buildup by providing plenty of air space beneath the panel. Never mount solar panels flat on the deck or any other solid surface….it is particularly important for tropical use to select higher-voltage panels (more cells) to compensate for the inevitable higher operating temperature.  (This Old Boat, p. 297)
• ….panels sold for 12-volt use can have from 30 – 36 cells in them. The voltage of an individual cell is just under 0.5V, so panel voltage varies from around 14.5 to 17.5 volts. Manufacturers are fond of calling modules with 33 cells or fewer “self-regulating.”….With the loss of output voltage due to elevated temperatures, a 33-cell panel on a hot day will have sufficient potential to fully charge your batteries. Count the number of cells, and don’t buy a panel that has fewer than 36.  (This Old Boat, p. 297)
• Solar panel connections are basic. If the output of the panel is less than 0.5% of your battery capacity, it can be connected directly to the battery without regulation. This is precisely how you should connect a solar panel sized to provide a float charge. If you are floating more than one bank, separate panels for each bank are preferable to a single panel with its output fed through isolating diodes, because the diodes introduce voltage drop that’s particularly unwelcome for expensive solar power. Similarly, solar panel input is often fed through a blocking diode to prevent discharge back through the panel at night, but the loss in daily output this diode causes will likely be greater than any nighttime discharge it avoids. It is usually best to omit it. Better solar regulators disconnect the panels from the batteries when they sense any reversal of current.  (This Old Boat, p. 297)
• …be sure you size the wires connecting to solar panels generously. Like batteries, the panels should be wired in parallel to increase their capacity.  (This Old Boat, p. 297)
• …do not forget to include a fuse in the positive cable as near the battery as possible.  (This Old Boat, p. 297)
• Isolation Diode – A diode which prevents one segment of a solar array from interacting with another array segment. Usually used to prevent array energy from flowing backwards through a sub-voltage series string. It may also serve the function of blocking diode. (http://www.daviddarling.info/encyclopedia/B/AE_blocking_diode.html)
• Blocking Diode – A diode used to restrict or block reverse current from flowing backward through a solar module. Alternatively, a diode connected in series to a photovoltaic string; it protects its modules from a reverse power flow and, thus, against the risk of thermal destruction of solar cells. (http://www.daviddarling.info/encyclopedia/I/AE_isolation_diode.html)

Water Generator

• The amps produced by a water driven generator can be accurately calculated if you know how much time you’ll spend sailing and at what speed. But since speed is predicated on the wind available, water-driven generators, too, offer no guaranteed amount of energy.  (Upgrading the Cruising Sailboat, p. 242 – 3)
• Water driven generators only produce electricity when moving. Tapping the ocean for power is, however, a natural solution.  (Upgrading the Cruising Sailboat, p. 247)
• On the face of it, alternators designed to be pulley-driven by the freewheeling propeller sound nearly ideal, because the shaft is there anyway, doing nothing while you sail. Its potential energy might as well be harnessed…the cutlass bearing usually makes some noise if the prop is left to freewheel with the engine off. Also, it causes much more wear and tear on the transmission, which is a costly piece of equipment. Sailing…miles with the prop freewheeling is adding unnecessary hours of wear to your transmission.  (Upgrading the Cruising Sailboat, p. 247)
• Drag is a factor in deciding to use a water driven generator. At 6 knots, the Power Log has 35 pounds of drag. And, because drag squares with velocity, it is not difficult to see that a thigh speeds, it would be advisable to hand the generator and stow it below.  (Upgrading the Cruising Sailboat, p. 247)
• Most water generators are designed to mount on the stern pulpit and assuming the stern pulpit isn’t about to fall off, this should be sufficiently strong place for the installation.  (Upgrading the Cruising Sailboat, p. 256)
• Under way, water generators are hard to beat for power output. There is some drag caused by towing a water generator, but for the cruising man with a boat 35’or larger, it shouldn’t be a great concern. At anchor, water generators are useless, so another system is necessary.  (Upgrading the Cruising Sailboat, p. 256 – 7)

Wind Generator

• The wind, of course, is more fickle than the predictable fall of night, but no less than the possibility of cloud cover. While a wind generator may produce more amps when it’s blowing 15 mph, there will be occasions of no wind at all.  (Upgrading the Cruising Sailboat, p. 242)
• Wind driven generators have been favored by some single handed ocean cruisers…because they produce less drag than water-driven generators. But any unit that produces just a few hundred milliamps is really only trickle charging the battery, and probably won’t be power enough to keep the icebox cold – the goal of many cruisers.  (Upgrading the Cruising Sailboat, p. 247)
• A major decision in choosing a wind-driven generator is selecting between a permanent and portable mount. The former can be left to run all the time while the later is used only at anchor. However, the large portable type has greater output. Handle this unit carefully when demounting, as a rap on the arm or skull could be lethal.  (Upgrading the Cruising Sailboat, p. 248)
• …it is important to consider how much time will be spent sailing and how much time will be spent at anchor. While some wind-driven generators will work when the boat is either in motion or at rest…  (Upgrading the Cruising Sailboat, p. 247)
• The electrical hook ups of wind and water generators generally will follow those just given for solar panels. Permanently mounted wind generators can be fitted high up and in the forward size side of mizzen masts, at the masthead, or on a pedestal attached to the stern pulpit….The only other word of caution is that objects this size are subject to considerable stress from the wind, and so should be securely mounted with thru-bolts. The vibration caused by many units is substantial and will loosen bolts and wear out bearing if not properly installed and inspected regularly.  (Upgrading the Cruising Sailboat, p. 255)
• They are mounted in the air, thus occupying no deck space; they have potential for much higher output than solar panels, and in the right conditions they deliver a charge 24 hours a day. In cruising areas flavored with a relatively constant breeze, wind power can meet all of the boat’s electrical requirements. There are a lot of different wind generators on the market, but it is most instructive to separate them into two categories – small diameter and large diameter. Small diameter alternators typically have a 3′ diameter turbine turning a self-exciting alternator. Large-diameter alternators have a blade-sweep diameter of up to 5′ and spin a permanent-magnet DC motor converted to a generator. The bigger the generator, the more powerful it will be, but output differences are more a function of physics than of technology.  (This Old Boat, p. 297)
• Wind generator output is related to blade-sweep diameter squred and wind speed cubed. Let’s consider wind speed first. If wind speed doubles, output goes up about eightfold (2 x 2 x 2). A more useful view of this relationship is that halving the wind speed reduces output eightfold. Be aware – or maybe beware – of rated output at high wind speeds.  (This Old Boat, p. 297)
• It is output at 10 knots that will be most meaningful, both for comparing wind generators and for calculating expected daily output.
• Increase blade-sweep diameter by a third – from 3 to 4 feet – and generator output should almost double (1.33 x 1.33 = 1.77). Increasing the sweep diameter to 5′ nearly triples output (1.67 x 1.67 = 2.79). So in a breeze wavering around 10 knots, where a 3′ generator may be putting out 1 – 2 amps, the output from a 5′ generator should be between 3 – 6 amps.
• Wind generators cannot be regulated in the same manner as engine alternator output because the magnetic field is created by permanent magnets, rather than passing a variable current through a field winding. Suppose you have a 400 Ah house bank connected to a large-diameter wind generator capable of putting out, say 15 amps in 20 knots of wind. When the wind blows at 20 knots, this generator is going to be pumping 15 amps into the batteries, regardless of their charge level. This is good when the batteries are discharged, but bad when they are nearly full. And nearly full is what you expect them to be if you are feeding them a more or less constant charge from solar or wind power. Since you cannot lower the generator’s output, by the time the charge of the battery bank reaches 85%, your choice becomes overcharge or no charge. The consequences of overcharging are more immediate and pernicious, so you have to stop the charge. Unfortunately even this is complicated. You cannot simply disconnect the charging circuit because that unloads the generator, allowing it to spin freely – like a pinwheel. Burnout is likely as output through the windings climbs beyond capacity, and the long blades are at risk of self destruction as their tip speed increases to perilous levels. For this reason, charge-circuit-opening solar panel regulators must never be used to regulate a wind generator….Strong winds will put a large diameer wind generator at risk of overspeed destruction, even under load, unless it has some form of speed control.  (This Old Boat, p. 298)
• Small-blade – Braking) – …some method of automatic braking. There are three primary methods in use: feathering, centrifugal braking, and electrical braking. Feathering can be hinged mount that cants the generator away from vertical in stronger winds, or it can simply be flexible blades that stall at higher speeds. Centrifugal braking can be inside the generator housing, or it can be cetrifugal air brake on the blades. Electric braking is typically effected by shorting out the generator windings. All of these methods are effective in ordinary winds, but onl the relatively rare tilt-back method can handle really strong winds. As a result, the most powerful wind generators are less in evidence than they once were, and those in use are almost invariably tied off when the boat will be unattended for any significant length of time.  (This Old Boat, p. 298 – 9)
• Small-blade – Regulator) – will survive any winds that most sailors are likely to encounter, especially if the stator coils have iron cores (as opposed to “air-filled” cores). This feature makes the alternator self-limiting, meaning that it cannot produce more than the rated output, which virtually eliminates the possibility of the unit’s burning out in high winds. Small-blade generators can also be regulated after a fashion with a simple device called a shunt regulator. Instead of reducing the output when it senses increasing voltage (like a regular voltage regulator), the shunt regulator diverts – shunts – some of the output into a “dummy” load, where it is dissipated as heat. Shunt regulators do not work well on the more powerful motor-type generators because current levels can rise too high. High-wind capabilities and a means of regulating the charge mean that a small-blade alternator-type wind generator can be mounted permanently and more or less ignored.  (This Old Boat, p. 299)
• Average daily output can be estimated at 24 times the rated output. If that rated output is 1 amp at 10 knots, such a generator may not satisfy the needs of a boat with high power consumption even if it can be allowed to run 24 hours a day. There are two equally popular responses. One is twin small-diameter generators. The other is a generator with a larger blade-sweep diameter, but not so large that it challenges overspeed protection. That typically means a diameter of around 4 feet. Either of these options will approximately double wind generator output. It has become more common to see twin 4′ generators. This option provides output comparable to that of a single large-dimeter generator, but the smaller units can be left unattended with greater confidence. And their smaller individual outputs allow for either shunt regulator or short-circuit regulation – a pulsing kind of short that slows down the alternator and thus reduces its output.  (This Old Boat, p. 299)
• One other factor that is often overlooked is the noise a wind generator can make. Small alternator types are typically powered by a six-blade turbine and should be virtually silent in normal wind conditions. Five-foot generators, particularly those with two blades, can make you think you are on an airboat in the everglades instead of in a previously quiet anchorage. Three blades have mostly replaced two, and these tend to be quieter….The number of blades…has no real impact on output, but all things being equal, more blades will result in quieter operation. In any case, you should endeavor to hear the generator you are considering in operation in high wind before you make your choice.  (This Old Boat, p. 299)
• Dump Regulation – Eclectic Energy Limited can supply a dump regulator which is installed close to the batteries. The regulator is adjustable between 11.5 and 17V. You set the voltage in accordance with the battery manufacturer’s recommendations and as this voltage is reached, the regulator progressively diverts DuoGen’s output to a pair of large wire wound resisters where the excess power is lost as heat. However it is important to be aware of their limitations. As they work by sensing battery terminal voltage, anything that raises that voltage, such as a solar panel, can cause the regulator to dump power prematurely…Note that where a bypass switch is fitted, the charge splitting function of the regulator is also bypassed when the switch is activated. We recommend that the bypassed output is fed to the largest bank(usually the serviced batteries)  (http://www.duogen.co.uk/)

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