MCEG 3123 QUIZ 7 4/25/2016 Chapters 8&9 -Wave and Geothermal Energy Question 1 H
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MCEG 3123 QUIZ 7 4/25/2016 Chapters 8&9 -Wave and Geothermal Energy Question 1 How does a TAPCHAN wave device work? Why is it similar to a low head hydro scheme? Question 2 What is the energy source of normal ocean waves? Question 3 The power density of waves is specified in kilowatts per metre per metre in which direction? Question 4 The power density of a typical sea state is dependent on the significant wave height. It is proportional to what value? Question 5 An 'average' wave power density in the north Atlantic might be 60 kW per metre. Any wave power devices will have to survive storm conditions. What is the power density likely to be then? Question 6 UK total electricity production in 2010 was about 360 terawatt-hours. Roughly what proportion might be met by the average technical wave resource for the north and west of the UK in water of 20 metres depth? Question 7 Wave energy devices may harness three modes of movement of a body in the sea.Explanation / Answer
Q NO 1.
Many countries today are seeking alternative energy sources to fossil fuels for environmental, economic, and political reasons. Since the 1970s, wave power has been exploited as a carbon and emissions free method of producing energy. However, scientists and engineers are continuing to study wave power and develop new methods of harnessing it today. We wish to study one simple form of wave power, the tapered channel. The tapered channel, or TAPCHAN method of wave energy conversion is a very simple device. Waves collect into a channel which tapers into a large reservoir. According to conservation of energy, as the wave width decreases, the amplitude increases, enabling the wave travel up a ramp and pour into the reservoir.Once the water is in the reservoir, it flows through a traditional hydroelectric turbine back to the sea. Our goal for this project is to apply classroom knowledge in to the real world problem of how to best exploit the power of waves using the TAPCHAN wave energy conversion method.
Elements of a Tapered Channel Wave Power System
Tapered channel with upward sloped bottom
Waves from the ocean enter the channel and increase in height as the channel tapers.
Elevated reservoir
Water collects in the elevated basin after exiting the channel.
Return conduit with turbine
By gravity, water flows from the basin back to the ocean. On the way, the water powers a standard hydroelectric turbine.
Q NO 2.
Ocean wave energy is captured directly from surface waves or from pressure fluctuations below the surface.
Waves are caused by the wind blowing over the surface of the ocean. In many areas of the world, the wind blows with enough consistency and force to provide continuous waves along the shoreline.Ocean waves contain tremendous energy potential. Wave power devices extract energy from the surface motion of ocean waves or from pressure fluctuations below the surface
Q NO 3.
Wave power is the transport of energy by wind waves, and the capture of that energy to do useful work – for example, electricity generation, water desalination, or the pumping of water (into reservoirs). A machine able to exploit wave power is generally known as a wave energy converter (WEC).
Wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave-power generation is not currently a widely employed commercial technology, although there have been attempts to use it since at least 1890. In 2008, the first experimental wave farm was opened in Portugal, at the Aguçadoura Wave Park.
Q NO 8.
The Wells turbine is a low-pressure air turbine that rotates continuously in one direction independent of the direction of the air flow. Its blades feature a symmetrical airfoil with its plane of symmetry in the plane of rotation and perpendicular to the air stream.
It was developed for use in Oscillating Water Column wave power plants, in which a rising and falling water surface moving in an air compression chamber produces an oscillating air current. The use of this bidirectional turbine avoids the need to rectify the air stream by delicate and expensive check valve systems.
Its efficiency is lower than that of a turbine with constant air stream direction and asymmetric airfoil. One reason for the lower efficiency is that symmetric airfoils have a higher drag coefficient than asymmetric ones, even under optimal conditions. Also, in the Wells turbine, the symmetric airfoil runs partly under high angle of attack (i.e., low blade speed / air speed ratio), which occurs during the air velocity maxima of the oscillating flow. A high angle of attack causes a condition known as "stall" in which the airfoil loses lift. The efficiency of the Wells turbine in oscillating flow reaches values between 0.4 and 0.7.
Q NO 9.
Salter's Duck is just one of many concepts for a wave energy converter (WEC), which can potentially convert wave power to usable energy. But in the 1970s, when alternative energy was gaining a lot of hype, it was the most exciting possibility. Since then, some companies have successfully implemented other WECs, like the farm of Pelamis devices (consisting of a series of floating cylindrical devices that drive generators) off Portugal. The Pelamis was even designed by Salter's former students [source: Economist]. But compared to Salter's Duck, these modern devices are relatively inefficient. (For more information on wave energy devices, read How Wave Energy Works)
The Duck falls under a class of WECs known as terminators. Terminators are oriented perpendicular to the direction of the wave. And, this is appropriate, as the Duck is basically the Schwarzenegger of WECs, destroying the waves it faces, leaving a calmer sea on the other side [source: Stuart].
Q NO 10.
Wave energy is the transport of energy by ocean surface waves, and the capture of that energy to do useful work – for example, electricity generation, water desalination, or the pumping of water (into reservoirs). Machinery able to exploit wave power is generally known as a wave energy converter (WEC).
Wave power is distinct from the diurnal flux of tidal power and the steady gyre of ocean currents. Wave-power generation is not currently a widely employed commercial technology, although there have been attempts to use it since at least 1890. In 2008, the first experimental wave farm was opened in Portugal, at the Aguçadoura Wave Park. The major competitor of wave power is offshore wind power.
In fluid dynamics, wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of oceans, seas, lakes, rivers, and canals or even on small puddles and ponds. They usually result from the wind blowing over a vast enough stretch of fluid surface. Waves in the oceans can travel thousands of miles before reaching land. Wind waves range in size from small ripples to huge waves over 30 m high.
Q NO 12.
The history of Earth concerns the development of the planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to the understanding of the main events of the Earth's past. The age of Earth is approximately one-third of the age of the universe. An immense amount of geological change has occurred in that timespan, accompanied by biological change.
Earth formed around 4.54 billion years ago by accretion from the solar nebula. Volcanic outgassing probably created the primordial atmosphere and then the ocean; but the atmosphere contained almost no oxygen and so would have been toxic to most modern life including humans. Much of the Earth was molten because of frequent collisions with other bodies which led to extreme volcanism. A "giant impact" collision with a planet-sized body is thought to have been responsible for forming the Moon. Over time, the Earth cooled, causing the formation of a solid crust, and allowing liquid water to exist on the surface.
The geological time scale (GTS) clock (see graphic) depicts the larger spans of time from the beginning of the Earth as well as a chronology of some definitive events of Earth history. The Hadean Eon represents time before the reliable (fossil) record of life beginning on Earth; it began with the formation of the planet and ended at 4.0 billion years ago as defined by international convention.[6] The Archean and Proterozoic eons follow; they produced the a biogenesis of life on Earth and then the evolution of early life. The succeeding eon is the Phanerozoic, which is represented by its three component eras: the Palaeozoic; the Mesozoic, which spanned the rise, reign, and climactic extinction of the huge dinosaurs; and theCenozoic, which presented the subsequent development of dominant mammals on Earth.
Hominins, the earliest direct ancestors of the human clade, rose sometime during the latter part of the Miocene epoch; the precise time marking the first hominins is broadly debated over a current range of 13 to 4 mya. The succeeding Quaternary period is the time of recognizable humans, i.e., the genus Homo; but that period's two million-year-plus term of the recent times is too small to be visible at the scale of the GTS graphic. (Notes re the graphic: Ga means "billion years"; Ma, "million years".)
The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago,[7][8][9] during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon. There are microbial mat fossils such as stromatolites found in 3.48 billion-year-old sandstone discovered in Western Australia. Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in southwestern Greenland[13] as well as "remains of biotic life" found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, "If life arose relatively quickly on Earth … then it could be common in the universe."
Living forms derived from photosynthesis appeared between 3.2 and 2.4 billion years ago and began enriching the atmosphere with oxygen. Life remained mostly small and microscopic until about 580 million years ago, when complex multicellular life arose, developed over time, and culminated in the Cambrian Explosion about 541 million years ago. This event drove a rapid diversification of life forms on Earth that produced most of the major phyla known today; and it marked the end of the Proterozoic Eon and the beginning of the Cambrian Period of the Paleozoic Era. More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described.
Geological change has been a constant of Earth's crust since the time of its formation, and biological change since the first appearance of life. Species continue to evolve, taking on new forms, splitting into daughter species or going extinct in the process of adapting or dying in response to ever-changing physical environments. The process of plate tectonics continues to play a dominant role in the shaping of Earth's oceans and continents and the living species they harbor. Changes in the biosphere—now dominated by human activity—continue, in turn, to produce significant effects on the atmosphere and other systems of the Earth's surface, such as the integrity of the ozone layer, the proliferation of greenhouse gases, the conditions of productive soils and clean air and water, and others.
Q NO 13.
Groundwater resides in the void spaces of rock, sediment, or soil, completely filling the voids. The total volume of open space in which the groundwater can reside is porosity. Porosity determines the amount of water that a rock or sediment can contain
An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude (or aquifuge), which is a solid, impermeable area underlying or overlying an aquifer. If the impermeable area overlies the aquifer, pressure could cause it to become a confined aquifer.
Q NO 14.
Magma (from Greek "thick unguent") is a mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets and some natural satellites. Besides molten rock, magma may also contain suspended crystals, dissolved gas and sometimes gas bubbles. Magma often collects in magma chambers that may feed a volcano or solidify underground to form an intrusion. Magma is capable of intrusion into adjacent rocks (forming igneous dikes and sills), extrusion onto the surface as lava, and explosive ejection as tephra to form pyroclastic rock..
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