Power Generation

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Power Generation

Electrical power generation on a sailing yacht is used for two purposes:

  • Charging the batteries which are used to power the on-board equipment (lighting, autopilot, refrigerator, freezer, etc).
  • Providing AC current to power on board AC systems such as refrigeration, air conditioning, water makers, power tools, etc.

Battery Charging

Charging a battery is much like pumping air into a tyre. The voltage in the battery equates to the air pressure in the tyre, and the voltage at the charging source equates to the air pressure in the pump. When the voltage in the battery is low, a high voltage at the charging source causes a significant amount of charge, or current measured in Amps, to flow into the battery. As the battery voltage increases (like increasing the air pressure in the tyre), the amount of current flowing into the battery reduces.

This continues until the difference between the voltage in the charging source and the voltage in the battery is too small to allow any more current to flow into the battery. The only way to continue charging the battery at that point is to increase the voltage at the charging source.

Engine Alternators

Alternator -- click for larger view

The theory behind an engine alternator is that a current flowing in a wire generates a magnetic field around the wire, and conversely, a wire moving inside a magnetic field has a current generated inside it.

An engine alternator works by having a rotating electromagnet (rotor) spun by a belt driven by the engine. The rotor creates a magnetic field, around which are placed some fixed outer windings made of wire (stator). The electromagnet in the rotor is powered by a small field current which creates a rotating magnetic field. This creates an alternating current in the stator by the magnetic field. A solid state rectifier mounted on the outer case of the alternator converts the AC into DC and a charge controller (or regulator) converts that DC into a current useful for charging the battery.

Regulators

Alternators are fitted with regulators that adjust the output voltage of the alternator by adjusting the input voltage to the field coil in the alternator rotor. If a higher voltage is applied to the rotor then the stator will produce a higher output voltage.

Because an inbuilt alternator reduces the output voltage of the alternator, as the battery becomes more fully charged the regulator will quickly reduce the output of the alternator to a fraction of the alternator's capacity, and the motor will be spinning for a long time to recharge the battery. This problem can be overcome by fitting an external regulator to the existing alternator. These are stand-alone electronic units that can drive the alternator as hard as possible to fully charge house batteries in the shortest possible time.

Companies such as http://www.amplepower.com/ Ample Power], Mastervolt and Sterling produce external alternator regulators, these usually require some form of modification to the existing alternator such as unscrewing the existing standard alternator regulator and brush holder assembly, which can be done by an auto electrician.

Generators (Gensets)

Diesel Gensets

Petrol Generators

Solar Panels

Flat solar panel mounted on a doghouse roof -- click for larger view

Typically when we say "solar panel" on a boat we mean a photovoltaic module (PV module). A PV module is a packaged, connected assembly of solar cells in an array which can provide an output voltage (typically in the 12 - 24 volt range).

The main types of PV modules in use on boats include:

  • Polycrystalline modules packaged under glass
  • Monocrystalline modules packaged under glass
  • Thin film modules on a steel or flexible substrate, without a glass coating

Wind Generators

Tow Generators

Tow Generator -- click for larger view

There are few manufacturers of dedicated tow generators (water turbines) around, which is a pity because a properly set up tow generator can produce a lot of power on a passage -- frequently more than a wind generator.

The main ones are:

  • Aquair 100 by Ampair. This is a generator that can be rigged either way -- as a wind generator or as a tow generator. The unit can have a water turbine attached on a long line in tow generator mode, or can have a tail and blades added to operate as a wind turbine. The unit is rated at 100W which means around 8A at 12V. Delatbabel -- I successfully used one of these for 5000+ miles of sailing in the South Pacific, including deep in the southern ocean where there was little or no power coming in via the solar panels. I got a steady 4-6A out of it at cruising speed.
  • Ferris Waterpower 200 from the USA is sold as a tow generator but can also be converted to a wind generator. This one claims to generate 200Ah per day which means approximately 8A at 12V, also approximately 100W.
  • Eclectic Energy in the UK make 2 types of tow generator, one being the DuoGen 3 which is a convertible wind/water generator and the other being the Sail-Gen which uses the same components but is a dedicated tow generator.

Charge Controllers

MPPT Controllers

See MPPT on wikipedia.

PWM Controllers

Forum Discussions

List links to discussion threads on partnering forums. (see link for requirements)

References

Publications, etc.

External Links

Also See

Personal Notes

  • Delatbabel -- I have 4 solar panels aboard my boat:
    • 2 x flat 80W panels, "Lensun" brand, on top of the doghouse roof. I purchased these via eBay. These run in parallel into a 15A MPPT controller.
    • 1 x monocrystalline panel, 75W Kyocera, This runs in parallel with a wind generator and a tow generator and goes into a 15A MPPT controller.
    • 1 x polycrystalline panel, 200W Solraiser. This runs into a into a "Morningstar" brand PWM controller.
The panels generally give pretty good output. I'm impressed by the Lensun panels, I walk on these a lot because I need to get up on the doghouse roof to set and unset the main sail, and they still produce quite a lot of power. I'm less happy with the Solraiser panel, the peak output from it appears to be about 4A and it is a lower voltage panel (peak output at 12V compared to say 15V for some other panels) meaning that it's less easy to run its full output via an MPPT controller into a 12V system. 2 of these in series might have been a better option. IT seems to do much better running into a PWM controller but really only gets up to full power when the battery voltage is quite low.


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Names: Delatbabel


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