Going with the flow — Tidal Power

by Stuart Hampton, July 10th, 2008, 7:00 am

With oil futures prices flirting with $150 a barrel, and world demand outstripping supply, governments, scientists, and energy companies are casting about, looking for both short- and long-term solutions for future energy sources. An emerging consensus (the drill more oil in more places — ANWR, the Federal lands, and the Continental Shelf — lobby notwithstanding), is to diversify the energy supply source base beyond hydrocarbons.

Green energy technologies such as wind turbines and solar-powered batteries are being steadily integrated into the energy mix. Texas, for instance, has emerged as a leading implementer of wind-powered generating plants. Three of the five largest wind farms in the US are located there. The world’s largest wind farm, Horse Hollow Wind Energy Center, was completed by FPL Energy (a unit of the FPL Group) in late 2006. Other power companies with wind energy interests in Texas include American Electric Power, AES, Austin Energy, Catamount Energy, and Edison Mission Energy.

Solar energy also has gained a solid foothold in the worldwide energy matrix, through such companies as BP Solar International, Suntech Power, Q-Cells, and Solarworld.

A lesser known power source, and one of the oldest, is tidal power. Tide mills date back to Roman times, and operated much like windmills, but with the tide rather than the wind powering the turning a wheel that rotated a millstone that ground grain into flour. Augustinian Canons operated one in Woodbridge in the east of England in the 12^th century. By the 18^th and 19^th centuries there were as many as 750 tide mills operating on both sides of the Atlantic, with about 300 in North America, 200 in the UK and Ireland, and 100 in France.

The main advantage was in the technology. Unlike windmills or even river-powered watermills (whose effectiveness was impaired by calm weather or droughts), the tidal mills could reliably operate 365 days a year.

Fast forward to today. Recent advances in turbine technology (a byproduct of wind turbine development) hold out the promise of using large-scale turbine arrays in high-velocity areas where natural and strong tidal current flows are concentrated — such as the coasts of Canada, the Straits of Gibraltar, and the Bosporus Straits — to generate significant power.

Some examples of what those advances have brought:

• In the US, Pacific Gas & Electricity teamed up in 2007 with the City and County of San Francisco and Golden Gate Energy to study harnessing the tides in San Francisco Bay to create a new source of renewable electric power.
• In the UK, E.ON and Lunar Energy (a British tidal power company), announced plans that year to develop a tidal stream power scheme of up to 8MW in the sea off the west coast of the UK, capable of producing enough power to service about 5,000 homes.
• In March 2008, Harland and Wolff (the shipbuilder famous for building the Titanic) completed construction of the world’s first commercial tidal stream turbine, for Marine Current Turbines. The installation of the 1.2 MW SeaGen Tidal System took place in the fast flowing narrows of Strangford Lough in Northern Ireland in April.
• This year, a joint venture between Lunar Energy and Korea Midland Power Company, was formed to create a tidal power scheme in the Wando Hoenggan waterway, expected to power 200,000 homes by 2015.

With tidal power technology only a few years behind the wind power generation systems that are becoming a regular part of utilities’ operations in the US and elsewhere, generating power from fast-moving ocean currents is about to become mainstream.

It’s just a matter of going with the flow.