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Shrouded Tidal Turbine
The shrouded tidal turbine is an emerging tidal stream technology that has a turbine enclosed in a venturi shaped shroud or duct (ventuduct), producing a sub atmosphere of low pressure behind the turbine. The venturi shrouded turbine is not subject to the Betz limit Betz's law indicates the maximum power that can be extracted from the wind, independent of the design of a wind turbine in open flow. It was published in 1919 by the German physicist Albert Betz. The law is derived from the principles of conserva ... and allows the turbine to operate at higher efficiencies than the turbine alone by increasing the volume of the flow over the turbine. Claimed improvements vary, from 1.15 to 4 times higher power output than the same turbine minus the shroud. The Betz limit of 59.3% conversion efficiency for a turbine in an open flow still applies, but is applied to the much larger shroud cross-section rather than the small turbine cross-section. Principles Considerable commercial int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tidal Stream Generator
A tidal stream generator, often referred to as a tidal energy converter (TEC), is a machine that extracts energy from moving masses of water, in particular tides, although the term is often used in reference to machines designed to extract energy from run of river or tidal estuarine sites. Certain types of these machines function very much like underwater wind turbines, and are thus often referred to as tidal turbines. They were first conceived in the 1970s during the oil crisis.Jones, Anthony T., and Adam Westwood. "Power from the oceans: wind energy industries are growing, and as we look for alternative power sources, the growth potential is through the roof. Two industry watchers take a look at generating energy from wind and wave action and the potential to alter." The Futurist 39.1 (2005): 37(5). GALE Expanded Academic ASAP. Web. 8 October 2009. Tidal stream generators are the cheapest and the least ecologically damaging among the four main forms of tidal power generation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Venturi Effect
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section (or choke) of a pipe. The Venturi effect is named after its discoverer, the 18th century Italian physicist, Giovanni Battista Venturi. Background In inviscid fluid dynamics, an incompressible fluid's velocity must ''increase'' as it passes through a constriction in accord with the principle of mass continuity, while its static pressure must ''decrease'' in accord with the principle of conservation of mechanical energy (Bernoulli's principle). Thus, any gain in kinetic energy a fluid may attain by its increased velocity through a constriction is balanced by a drop in pressure. By measuring pressure, the flow rate can be determined, as in various flow measurement devices such as Venturi meters, Venturi nozzles and orifice plates. Referring to the adjacent diagram, using Bernoulli's equation in the special case of steady, incompressible, inviscid flows (such as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shroud
Shroud usually refers to an item, such as a cloth, that covers or protects some other object. The term is most often used in reference to ''burial sheets'', mound shroud, grave clothes, winding-cloths or winding-sheets, such as the famous Shroud of Turin, ''tachrichim'' (burial shrouds) that Jews are dressed in for burial, or the white cotton ''kaffan'' sheets Muslims are wrapped in for burial. A traditional Orthodox Jewish shroud consists of a tunic; a hood; pants that are extra-long and sewn shut at the bottom, so that separate foot coverings are not required; and a belt, which is tied in a knot shaped like the Hebrew letter ''shin'', mnemonic of one of God's names, Shaddai. Traditionally, mound shrouds are made of white cotton, wool or linen, though any material can be used so long as it is made of natural fibre. Intermixture of two or more such fibres is forbidden, a proscription that ultimately derives from the Torah, ''viz.'', Deut. 22:11. An especially pious Jewish ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Betz Limit
Betz's law indicates the maximum power that can be extracted from the wind, independent of the design of a wind turbine in open flow. It was published in 1919 by the German physicist Albert Betz. The law is derived from the principles of conservation of mass and momentum of the air stream flowing through an idealized "actuator disk" that extracts energy from the wind stream. According to Betz's law, no turbine can capture more than 16/27 (59.3%) of the kinetic energy in wind. The factor 16/27 (0.593) is known as Betz's coefficient. Practical utility-scale wind turbines achieve at peak 75–80% of the Betz limit. The Betz limit is based on an open-disk actuator. If a diffuser is used to collect additional wind flow and direct it through the turbine, more energy can be extracted, but the limit still applies to the cross-section of the entire structure. Concepts Betz's law applies to all Newtonian fluids, including wind. If all of the energy coming from wind movement through a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
