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

ntcktshtrstk

Cruising Southern New England Waters

One of the most wonderful childhood vacations I can remember was back in 1971 when my best friend invited me to his family’s summer home on Nantucket Island. For a 10-year-old kid, this was a thrilling trip for many reasons, not the least of which was the fact it was also my ...read more

IMG_8287GR16Mykonos

Cultural Charters: Mykonos

In last month’s column, I covered the amazing mix of cultures that have called the Dalmatian Coast home over the centuries. Croatia cruising is like a smorgasbord of intertwined centuries, and the islands are a movie set. A little farther south, though, you’ve also got Greece, ...read more

cookinglead

Cruising: No Oven? No Worries

Many cruising boats, especially smaller ones, don’t have a conventional oven. But that doesn’t mean that you can’t have all the baked foods you want, from bread to brownies to breakfast rolls to casseroles and even a roast chicken. All it takes is the right bit of gear and a ...read more

TOTW_PromoSite

SAIL's Tip of the Week

Presented by Vetus-Maxwell. Got a tip? Send it to sailmail@sailmagazine.com Take no chances  This is my stern with the engine running slowly in gear against the lines. We all know that when we’re charging batteries this lets the engine warm up thoroughly. However, I have a ...read more

ZK-Seaboot-900

Gear: Zhik’s Seaboot 900

A Better Sea Boot Following up on its successful ZK Seaboot 800, Zhik’s Seaboot 900 was created in partnership with team AkzoNobel and Dongfeng Race Team, the latter the overall winner of the 2017-18 Volvo Ocean Race. Designed for serious, long-distance offshore racers and ...read more

01-LEAD-FP-Astrea-42-Gilles-martin-rajet---Navigation

Switching to Solar Offshore

No sensible bluewater sailor would consider setting off on a long cruise these days without some means of generating power other than by burning fossil fuels. The good news is that solar energy is becoming less expensive by the day, making it an obvious answer for providing the ...read more

190812-Tiwal-Video-600x

Video: Tiwal Cup 2019

Who says you need a superyacht to have fun? It would be hard to imagine having a better time on the water than these sailors recently did racing aboard a fleet of Tiwal inflatable sloops. ...read more