Marine Current Turbines

Marine Current Turbines Ltd are carrying out research and development on submerged turbines which will rotate by exploiting the principle of flowing water in general and tidal streams in particular. The general principle is that an 11 m diameter water turbine is lowered into the sea down a steel column drilled in the sea bed. The tidal movement of the water then rotates the turbine and generates electricity. 

Marine current turbines derive their power from the tides, which unlike wind flow, is in two directions only. A major difference is that since water is some 800 times denser than air, the thrust on the blades is so much greater and the blades tend to be shorter and sturdier. The turbines are designed to operate in a current of 4.5 knots (2.3 ms ) but a 1 MW turbine operating at full power would have to withstand some 900 tons s of water passing through its blades, which is indeed onerous [107a]. 

SeaGen, the first tidal turbine to produce energy on a commercial scale (image courtesy of Marine Current Turbines). 

Many pre-production tidal stream devices are now in operation or are currently being installed in several locations around the British Isles. SeaGeneration (Wales) Ltd, a development company, has been set up by Marine Current Turbines (MCT) and RWE npower renewables to develop a 10.5 MW tidal energy farm in The Skerries off the coast of Anglesey it was anticipated that construction would commence in 2012. 

Douglas, C.A., Harrison, G.P. and Chick, J.P. (2008), Life cycle assessment of the Seagen marine current turbine , Proc. IMechE, Part M Journal of Engineering for the Maritime Environment, Vol. 222, Issue 1, pp. 1-13. 

Testing of the Shale-II JP-5 jet fuel, which is currently underway in four different gas turbine engines, shows good combustion performance. No problems have been encountered. Likewise, testing of ship steam boilers, marine gas turbines, and diesel engines on the Shale-II diesel fuel marine (DFM) is demonstrating highly acceptable performance. 

Marine boilers currently in operation tend to be oil-fired, packaged, D-type units. However, in many of the latest merchant marine and naval ships constructed, marine boilers have become relegated only to auxiliary and heat-recovery use because diesel engines and gas turbines have become the primary form of equipment employed for marine propulsion. 

Multiple-step variable-speed fan control, type d. is best applied with steam-turbine drives. In aplant with ac auxiliary motor drives, slip-ring motors with damper integration must be used between steps, making the installation expensive. Although dc motor drives would be less costly, few power plants other than marine propulsion plants have direct current available. And since marine units normally operate at full load 90 percent or more of the time, part-load operating economics are unimportant. If steam-turbine drive will be used for the fans, plot the power-input curve LMD, using data from the fan manufacturer. 

The U.S. Navy has been involved for some time in the development of Navy fuels from alternative sources (shale oil, tar sands and coal). As a part of this effort, the Naval Research Laboratory and the Naval Air Propulsion Center have been studying the characteristics of these fuels (.1, 2). NKL and NAPC are currently participating in a program to characterize the products from the Shale-II refining process conducted by the Standard Oil Company of Ohio (SOHIO) at their refinery in Toledo, Ohio. This paper is concerned with a part of this program and is a surrmary of the work on the physical and related properties of three military type fuels derived from shale JP-5 and JP-8 jet turbine fuels, and diesel fuel marine (DEM) (3, 5). Another paper of this symposium (6) will discuss the chemical characterization of the fuels. 

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