Ask SAIL: Create Power from Tides?

The government has, for a decade, studied the possibility of generating electric power from the tides. Because a sailboat on a mooring is subject to tidal flow, why can’t we use this method to help generate power? Sailboats sit on moorings for long periods, sometimes for weeks, and even a trickle charge would be beneficial.
Author:
Updated:
Original:

Don Howrilka of Dallas, Texas asks:

Q The government has, for a decade, studied the possibility of generating electric power from the tides. Because a sailboat on a mooring is subject to tidal flow, why can’t we use this method to help generate power? Sailboats sit on moorings for long periods, sometimes for weeks, and even a trickle charge would be beneficial.

Nigel Calder replies:

NigelCalder_3

A The core problem is water velocity.

It takes 4 to 5 knots of boat speed (or tidal current flowing past a moored boat) to get most propellers spinning fast enough to generate electricity. Even at these speeds the energy “harvest” is very limited, as the overall efficiency of the process is probably well below 20 percent. There are several outboard-motor style water generators on the market, but most require water speeds of 4 to 5 knots to get going and higher speeds to produce much power. Watt & Sea units (wattandsea.com) purportedly get going at 3 knots and produce up to 120 watts of power at 5 knots. If you moor your boat somewhere with a strong tidal current, you could try mounting one of these devices.

Related

Beneyteau-Excess12

Boat Review: Excess 12

Groupe Beneteau, builder of Lagoon catamarans, has introduced a new multihull line called Excess. The first of the boats to reach U.S. shores at the Annapolis boat show was the Excess 12, a 38ft 6in design based on the popular Lagoon 40. The thought process behind this new boat ...read more

Spindriftracing

Extreme Sailing: No Piece of Cake

It can be easy to take for granted the incredible performance of today’s most cutting-edge grand prix racing boats. The latest crop of full-foiling 75ft America’s Cup monohulls, for example, were all up on their foils and even successfully tacking within hours of their first ...read more

Solar-Dinghy-pump-photo

Gear: Solar Powered Dinghy Pump

Tired of forever finding your dinghy or open daysailer filled with water when you arrive to go sailing? For years, sailors and engineers have sought a solution to this seemingly eternal problem, and now it appears the folks at Sea Joule Marine may have finally found it in their ...read more

BestBoatPromo-03

Best Boats 2020

How’s this for a thought experiment: imagine setting a diminutive Tiwal 2 inflatable dinghy alongside a Catalina 545 cruiser? It would be hard to imagine two more different watercraft, and yet they are both still very much sailboats. They are also both winners in this year’s ...read more

Hanse-675

Video Tour: Hanse 675

This past fall at the Annapolis Sailboat show, we had a chance to catch up with Hanse’s  Maxim Neumann, who kindly provided us a tour of the company’s new flagship, the Hanse 675. An impressive, well-built production yacht that boldly ventures into maxi-yacht territory, the ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell. Got a tip? Send it to sailmail@sailmagazine.com Be thrifty with propane  If you like to cook on board, the propane tanks supplied as standard with many modern yachts won’t get you far. Whether we bake bread or not, the one thing we all do is boil ...read more