Hydro-regeneration
The ability for sailing boats to recover energy from a freewheeling propeller has met with variable success over the years, but companies such as Torqeedo, ePropulsion and Seadrive have made this hydro-regen more efficient. The main issue has been
the comparatively low rpm from a freewheeling propeller, so even the most efficient regenerators still require the yacht to be sailing quite briskly.
Advances in propellers designed specifically for electric boats, such as with models by Gori, Darglow and Bruntons have made the ‘reverse’ pitch needed more effective.
Torqeedo has long offered hydroregen on even its smaller models, while ePropulsion provides regeneration models in its portfolio of new Spirit and Navy electric outboards. The propellers have been modified to be more efficient when freewheeling, while the controllers have been designed to accept even small amounts of returning current and feed it into the batteries.
Regeneration is arguably more advanced in some of the pod drives, mainly due to their bigger motors and larger propellers.
Specially-configured props can greatly reduce the drag created, but some hydro-regen systems can still take up to a knot off the sailing speed of a yacht.
Consequently, some smart controllers take data directly from the GPS and don’t bother to engage regeneration capability until the extra drag will barely be noticed.