Passage 3
Tidal Power on the Cheap?　　A  The startup, located on the Orkney Islands, way north of Scotland, has raised ￡6.2 million to build a working prototype of a floating tidal turbine that it says will be cheaper to install and maintain than others being tested now. The 8-meter-long prototype, ideally, will go into the water at the European Marine Energy Centre (EMEC) Tidal Test Site that sits just down the road from ScotRenewables in 2010. Commercial versions of the turbine will measure up to 40 meters long and weigh 250 tons, but generate 1.2 megawatts of power.
　　B  “That’s quite impressive when you compare it to others,” said CEO Barry Johnston. “We want to be competitive with offshore wind.” Rather than anchor a permanent turbine on the ocean floor, ScotRenewables will build a floating turbine that is slack moored with chains to an anchor on the sea floor. The body of the turbine-a long 40-meter tube of metal with a point at the end-will face directly into the tide. Below, two turbines attached to fins will convert the power of the tides into electricity. Johnston explained “A 1-meter prototype ScotRenewables is experimenting with in the wave tank is built. It looks like a model rocket with two fins with propellers attached to the ends of the fins.”
　　C  Tidal is the potentially most predictable, reliable form of renewable energy. With a tide table and computer, ScotRenewables can calculate the power output of a turbine decades in advance. You can’t do that with intermittent, variable sources like wind, solar or wave. Unfortunately, harnessing tidal power is quite difficult. Some of the prototypes that have been tested in the decades are quickly destroyed by rushing tides. Pulling those turbines up from the sea bed and taking them into the shop consumes time and money. Taking the ScotRenewables turbine in for repairs should be easy: maintenance workers would just have to tak