Historically ocean going yachts making ocean transits have found that there
is insufficient wind over deck for a wind turbine to provide a useful amount of power when making a trade wind transit.
It is for this reason that the Aquair hybrid wind and water powered generator was developed by Ampair. The generator section
can either be mounted at the stern in “water mode” and a water turbine towed behind the yacht, or the generator
can be converted into “wind mode” and hoisted in the rigging or fitted on a pole mount. The water mode is good
for those deep water passages where wind over deck is low and the sails of the yacht are already acting as a very efficient
machine for capturing wind energy. In water mode the turbine is towed behind the vessel on about 30 metres of tow rope which
twists up just enough to turn the stern mounted generator section. Generating approximately one amp per knot of boat speed
this simple solution has been adopted by thousands of ocean sailing enthusiasts and copied by a number of other manufacturers
! The drag on the boat is small, typically no more than a quarter of a knot. The generator section is supplied in a circular
gimbal ring which is best mounted between stern rails using rope or tape lashings. The reason that this apparently crude
mounting solution is preferred is that the stern of a small boat moves around on the water more than is apparent to the
crew (primarily in heave and sway) whilst the turbine is a relatively fixed point in the water. Therefore if the mounting
is too rigid the turbine will exert quite abrupt and undesirable load changes on the mounting and alternator. For those
vessels with no convenient stern rail or equivalent stern structure a fully gimballed deck mount is available: this is especially
useful for multihull vessels with no structures on the sponson decks.
It is not recommended that the Aquair is used in water mode for
shallow water coastal sailing. Even if the water depth is greater than 30 metres there is the ever present risk of fishing
for lobster pots (no need to worry, the tow rope is secured to the generator by a weak link) and it is simply too great
a hassle to stream and recover the towed turbine for day cruising. The lower the speed through the water the deeper the
turbine will sink in the water. In a man overboard situation the turbine speed drops to zero as the boat goes about to recover
the crew, and the turbine will sink to 30 metres. In water depths of 30 metres or less there is a risk that the turbine
will snag on the bottom, and whilst the weak link would break, this is an extra and avoidable excitement at a dangerous
moment and so it should not be used in water mode in these locations.
To
convert an Aquair into wind mode all that is necessary is to unpin it from the stern mount; fit the turbine blades and tail;
and then either hoist it into the rigging or place it on a stern pole. Most yachts do not have a spare slot in the rigging
unless the sails are down (although some ketches, especially junk rigged ketches do) and so hoisting into the rigging is
normally reserved for when moored or anchored. In contrast a stern pole is more frequently accessible. However easy the
conversion to wind mode is (it takes about 15 minutes) it should be borne in mind that it typically needs to be done at the
end of a long days sailing at a time when most folk are concentrating pretty hard on food and drink. For this reason we
suggest that unless you are unusually self-disciplined the use of the Aquair in wind mode is best thought of as something
that is most suited to yachts that will be moored in a single location for several days – such as is common for many
round the world sailors who do tend to spend several months in the classic cruising grounds between transits. The Aquair
pole conversion kit is an under used option that deserves wider use than it gets.
The introduction of the Ampair Pacific 300 micro turbine may change the attractiveness of
the Aquair 100 hybrid turbine for deep water sailors. This is because the new larger 300 watt turbine has both increased
power and a very good low wind speed performance. Therefore it will still produce useful amounts of power during the deep
water transits when wind over deck is low, thereby making the Aquair 100 less necessary. However we thought similar things
when we replaced the Ampair 25 with the Ampair 50, and then the Ampair 75, and then the Ampair 100. On each occasion we
found that we were racing to keep up with the increased power needs on yachts and so the Aquair has retained its place in
the inventory of the long distance sailor.
Ampair have so far not introduced a rapid conversion hybrid wind/water generator
but we have watched with interest the introduction of the hybrid Duogen manufactured by our competitors at Eclectic Energy,
a good company who we respect. Quite apart from the expense the disadvantages associated with this class of device are that
they present increased drag when in water mode compared to a towed turbine; weigh more and take up increased deck and transom
space; have reduced “pointing” authority when in wind mode; suffer from drive-train transmission losses and
drive-train reliability/maintenance issues. However they do have the advantages of a more rapid conversion from wind to water
mode; and increased utility in water mode in shallow water locations. Maybe one day we will develop one.
The UW (underwater)
is a microhydro generator that is designed for operation in zero head “run of the river” circumstances. It is
not intended for use on yachts as the submerged generator presents a far greater drag than would be acceptable to most sailors.
However we do have clients who regularly moor in fast tidal streams, and who choose to lower an Aquair UW on a pole to generate
power in these circumstances. This is very similar to its intended use and it is a very reliable power source when such
favourable conditions exist.
