Variations of Winds

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The speed and direction of measured winds can be indicated on a chart by the symbols in Figure 14.4. Repeated measurements can be summarised by a 'wind-rose', which indicates the frequency with which the wind has a n

Figure 14.3 A 'Dwyer wind meter', which is used to measure the wind speed by means of a lightweight ball made of pith, inside a slightly conical tube, whose wider end is at the top, and whose lower end is connected to an opening which is faced into the wind. The stronger the wind, the greater the lifting force on the pith ball, and so the higher up the tube it can be lifted, despite the wider diameter there.

Figure 14.3 A 'Dwyer wind meter', which is used to measure the wind speed by means of a lightweight ball made of pith, inside a slightly conical tube, whose wider end is at the top, and whose lower end is connected to an opening which is faced into the wind. The stronger the wind, the greater the lifting force on the pith ball, and so the higher up the tube it can be lifted, despite the wider diameter there.

particular strength and direction (Figure 14.5).

Surface winds vary annually and daily, and Figure 14.6 shows the outcome in the form of hodographs for Sydney, for instance. This diagram shows a south-easterly breeze on January afternoons, but winds are more westerly in July. In both months the wind backs during the day, i.e. it changes direction anticlockwise (Section 12.2). Figure 14.6 also shows that the wind at Sydney is generally stronger during the daytime than at night, though 9 p.m. winds in January are stronger than those at 9 a.m. Hodographs like those in Figure 14.6 are especially useful in considering which areas are vulnerable to air pollutants after they have been emitted into the boundary layer (Section 14.7)

There is a clear variation of windiness latitudinally about Australia and out to sea. The 'annual mean daily wind run' (i.e. the distance that a balloon floating in the wind would be carried in a day) is greater offshore than on the mainland (Figure 14.7), whilst the wind run inland is lower in the north and east. On the coast, it is greatest along the west and in Tasmania, so these would be the best places for wind turbines to generate electricity (Section 14.5). Table 14.2 shows that once-in-five-years extreme winds in Australian cities are similar, but once-in-a-century winds are strongest in Darwin and Brisbane, which are vulnerable to tropical cyclones.

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Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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