Friday, August 17, 2007

Tidal range - Yarmouth mill

Here are the two photos of Yarmouth Mill - taken at roughly high tide, and mid-to-low tide in a relatively springy part of the tidal cycle.

You can see that the range is about 1 - 1.5 metres at this stage in the cycle. Plenty of tidal range to be getting on with (and large volumes of water to play with)

Wednesday, August 15, 2007

Tidal, tidal everywhere (again)

Staying in Yarmouth, it's suddenly obvious that our forefathers knew all about the tides and how to use them.

For the first time in about 40 years, I've realised that the old Mill at Yarmouth must have been a tidal mill. A little research turns up this page on Yarmouth's history, which says that a tidal mill has been on the site since the 17th Century, with the current building dating from 1793.

The picture is taken at high tide, or thereabouts, and I'll try to post one at low tide so you can see the tidal range.

So, at least 300 years of tidal power use in Yarmouth!

Horizontal axis wind turbine

Visited the Bembridge windmill - the only extant windmill on the Isle of Wight.

All of the main elements are similar to most of the wind turbines currently available. The main gearbox is in the nacelle, changing the direction of rotation from horizontal to vertical, and you can just about make out the yawing gears at the top, which allow the nacelle to rotate to stay head to wind.

The blade thrust is controlled by reefing the sails, rather than by fancy feathering technologies, and you can see how the blade geometry allows for different angles of attack at different radii from the hub.

The difference is that the majority of power offtake is lower down the tower, where additional gears drive the grinding stones, rather than in the nacelles as at present. Perhaps there's something to learn from our predecessors?

Wednesday, August 08, 2007

Another Needles trip

Another trip to the Needles today, with a better picture of the tidal effects on the Shingles Bank (the dark in above the lighthouse).

Tuesday, August 07, 2007

Tidal, tidal everywhere

I was out walking on Yarmouth Pier (the oldest wooden pier still standing the UK), and came across this sign and buoy. Seems that Southampton University has recognised the potential of the tides off Yarmouth and is trying out a turbine.

I'm planning to to drop them an email ( to try to learn more.

More great tidal resources

Just took a long walk along the chalk ridge forming the backbone of the Isle of Wight, from Freshwater Bay to the Needles. A lovely day, a lovely walk and fantastic views over the approaches to the Solent, including the notorious Shingles Bank.

The difference in the water over the Shingles Bank and in the Needles Channel stood out clearly (it doesn't in this picture, sorry), with clear rough water on the Bank and flat water in the channel.

The tidal streams through here run at 6 knots or so at Spring Tide, but the amenity impact would be an important factor (it's Cowes Week this week, and the Fastnet race with a few hundred yachts streaming through the Needles Channel starts on Sunday).

If someone could find a way of exploiting the tidal streams without upsetting other users of the marine environment, this woudl be a great place to start: generally not too wavey, close to markets, close to ports - magic!