Winds are often associated with storms. Storms, in turn, are produced when high-pressure and low-pressure air masses collide. High and low pressure zones move across the continents.
Low-pressure air masses originate in the tropics. They are created by the huge influx of solar energy in these regions. Huge masses of low-pressure air frequently break away and migrate northward, sweeping across the North American continent.
High-pressure air masses originate in the North and South poles, regions of more or less permanent cold, high-pressure air. Like warm tropical air, huge masses of cold Arctic air also break loose and drift southward, sweeping across the Northern Hemisphere.
High-pressure and low-pressure air masses, often measuring 500 to 1,000 miles in diameter, move across continents. The movement of high- and low-pressure air masses across continents is steered by prevailing winds and by the jet stream (high altitude winds). As these air masses collide, they produce an assortment of weather, often accompanied by winds. As with all other forms of wind, storm winds are created by differences in pressure between high- and lowpressure air masses. The greater the difference in pressure between a high-pressure air mass and a “neighboring” low-pressure air mass, the stronger the winds. In some cases, these winds contain an enormous amount of energy.
Showing posts with label wind. Show all posts
Showing posts with label wind. Show all posts
Sunday, May 20, 2012
Wind and Wind Energy
As you learned in the last chapter, wind is a clean, abundant, and renewable energy resource that can be tapped to produce electricity. This chapter explores how wind is generated and introduces
you to two types of wind — local and global. We’ll also explore ways local topography affects wind, introducing you to two key concepts: ground drag and turbulence. This information provides the
practical knowledge you will need to select the best site for a wind turbine and the optimum tower height.
What is Wind?
Wind is air in horizontal motion across the Earth’s surface. All winds are produced by differences in air pressure between two regions. Differences in pressure result from differential heating of the surface of the Earth. Heating, of course, is caused by sunlight striking the Earth’s surface.
Like most other forms of energy in use today, even coal, oil and natural gas, wind is a product of sunlight — solar energy. Some wind advocates, refer to wind as “the other solar energy” or “secondhand solar energy.” Let’s begin by looking at two types of local winds: (1) offshore and onshore winds and (2) mountain-valley breezes.
Offshore and Onshore Winds
Offshore and onshore winds are generated along the shores of large lakes, such as the Great Lakes of North America, and along the coastlines of the world’s oceans. Offshore and onshore winds blow regularly, nearly every day of the year. They are produced by the differential heating of land and water, caused by solar energy.
Here’s how this happens: As shown in Figure 2.1a, sunlight shining on the Earth’s surface heats the land and water simultaneously. As the water and adjoining land begin to warm, they radiate
some of the heat (infrared radiation) into the atmosphere. This heat, in turn, warms the air above them. When air is heated it expands, and as it expands it becomes less dense and rises. The upward movement of air is called a thermal or updraft.
Although water and land both heat up when warmed by the sun, land masses warm more rapidly than neighboring bodies of water. Because air over land heats up more quickly than air over water, air pressure over land is lower than over neighboring surface waters. As warm air rises over land, cooler, high pressure air moves in to fill the void, resulting in a steady breeze known as onshore wind.
the void, resulting in a steady breeze known as onshore wind. At night, the winds blow in the opposite direction — from land to water — as illustrated in Figure 2.1b. These are known as offshore breezes or offshore winds.
Like onshore winds that occur during the day, offshore winds are created by differences in air pressure between the air over land and neighboring water bodies. Here’s what happens: after sunset, the land and the ocean both begin to cool. Land, however, cools more rapidly than water. Because the water cools more slowly, air above it is warmer. Warm air expands and rises. Cooler high pressure air
Fig. 2.1a and 2.1b: Onshore and offshore breezes. Onshore (a) and offshore (b) breezes occur along the coastlines of major lakes and oceans.
flows from the land to the water at night (Figure 2.1b). The result is an offshore breeze: steady winds that flow from land to water.
Offshore and onshore breezes operate day in and day out on sunny days, providing a steady supply of wind energy. Because offshore and onshore winds are fairly reliable, coastal regions of the world are often ideal locations for small (and large) wind turbines.
Coastal winds are more consistent than winds over the interior of continents and also tend to be more powerful because of the relatively smooth and unobstructed surface of open waters. That is to say, wind moves rapidly over water because lakes and coastal waters provide very little resistance to its flow, unlike forests or cities and suburbs, which dramatically lower surface wind speeds.
Mountain-Valley Breezes
Like coastal winds, mountain-valley breezes arise from the differential heating of the Earth’s surface. To understand how these winds are formed, let’s begin in the morning.
As the Sun rises on clear days, sunrays strike the valley floor and begin heating the ground, valley walls and mountains. As the ground and valley walls begin to warm, the air above them warms. It then expands and begins to flow upward. This process is known as convection. (Convection is the transfer of heat in a fluid or a gas that is caused by the movement of the heated air or fluid itself.) While some of this warm air rises vertically, mountain valleys also tend to channel the solar-heated air through the valley toward the mountains (Figure 2.2). As the warmed air moves up a valley, cooler air from surrounding areas flows in to replace it. This wind is known as a valley breeze.
Throughout the morning and well into the afternoon, breezes flow up-valley — from the valley floor into the mountains. These breezes tend to reach a crescendo in the afternoon. When the Sun sets, however, the winds reverse direction, flowing down valley.
Winds flow in reverse at night because the mountains cool more quickly than the valley floor. Cool, dense air (high-pressure air) from the mountains sinks and flows down through the valleys like
Fig. 2.2a and 2.2b: Mountain-Valley Breezes. Mountain-valley winds can provide a reliable source of wind power if conditions are just right. (a) Up-valley winds. (b) Down-valley winds.
the water in a mountain stream, creating steady and often predictable down-valley or mountain breezes.
Together, valley and mountain winds are known as mountainvalley breezes. As a rule, mountain breezes (down-flowing winds) tend to be stronger than daytime valley breezes.
Mountain-valley breezes typically occur in the summer, a time when solar radiation is greatest. They also typically occur on calm days when the prevailing winds (larger regional winds, which will be discussed shortly) are weak or nonexistent.
Mountain-valley winds also form in the presence of prevailing winds — for example, when a storm moves through an area. In such instances, mountain or valley winds may “piggy back” on the prevailing winds, creating even more powerful (and hence higher energy) winds. When consistently flowing in the same direction, such winds can provide a great deal of power that can be tapped to produce an abundance of electricity.
you to two types of wind — local and global. We’ll also explore ways local topography affects wind, introducing you to two key concepts: ground drag and turbulence. This information provides the
practical knowledge you will need to select the best site for a wind turbine and the optimum tower height.
What is Wind?
Wind is air in horizontal motion across the Earth’s surface. All winds are produced by differences in air pressure between two regions. Differences in pressure result from differential heating of the surface of the Earth. Heating, of course, is caused by sunlight striking the Earth’s surface.
Like most other forms of energy in use today, even coal, oil and natural gas, wind is a product of sunlight — solar energy. Some wind advocates, refer to wind as “the other solar energy” or “secondhand solar energy.” Let’s begin by looking at two types of local winds: (1) offshore and onshore winds and (2) mountain-valley breezes.
Offshore and Onshore Winds
Offshore and onshore winds are generated along the shores of large lakes, such as the Great Lakes of North America, and along the coastlines of the world’s oceans. Offshore and onshore winds blow regularly, nearly every day of the year. They are produced by the differential heating of land and water, caused by solar energy.
Here’s how this happens: As shown in Figure 2.1a, sunlight shining on the Earth’s surface heats the land and water simultaneously. As the water and adjoining land begin to warm, they radiate
some of the heat (infrared radiation) into the atmosphere. This heat, in turn, warms the air above them. When air is heated it expands, and as it expands it becomes less dense and rises. The upward movement of air is called a thermal or updraft.
Although water and land both heat up when warmed by the sun, land masses warm more rapidly than neighboring bodies of water. Because air over land heats up more quickly than air over water, air pressure over land is lower than over neighboring surface waters. As warm air rises over land, cooler, high pressure air moves in to fill the void, resulting in a steady breeze known as onshore wind.
the void, resulting in a steady breeze known as onshore wind. At night, the winds blow in the opposite direction — from land to water — as illustrated in Figure 2.1b. These are known as offshore breezes or offshore winds.
Like onshore winds that occur during the day, offshore winds are created by differences in air pressure between the air over land and neighboring water bodies. Here’s what happens: after sunset, the land and the ocean both begin to cool. Land, however, cools more rapidly than water. Because the water cools more slowly, air above it is warmer. Warm air expands and rises. Cooler high pressure air
Fig. 2.1a and 2.1b: Onshore and offshore breezes. Onshore (a) and offshore (b) breezes occur along the coastlines of major lakes and oceans.flows from the land to the water at night (Figure 2.1b). The result is an offshore breeze: steady winds that flow from land to water.
Offshore and onshore breezes operate day in and day out on sunny days, providing a steady supply of wind energy. Because offshore and onshore winds are fairly reliable, coastal regions of the world are often ideal locations for small (and large) wind turbines.
Coastal winds are more consistent than winds over the interior of continents and also tend to be more powerful because of the relatively smooth and unobstructed surface of open waters. That is to say, wind moves rapidly over water because lakes and coastal waters provide very little resistance to its flow, unlike forests or cities and suburbs, which dramatically lower surface wind speeds.
Mountain-Valley Breezes
Like coastal winds, mountain-valley breezes arise from the differential heating of the Earth’s surface. To understand how these winds are formed, let’s begin in the morning.
As the Sun rises on clear days, sunrays strike the valley floor and begin heating the ground, valley walls and mountains. As the ground and valley walls begin to warm, the air above them warms. It then expands and begins to flow upward. This process is known as convection. (Convection is the transfer of heat in a fluid or a gas that is caused by the movement of the heated air or fluid itself.) While some of this warm air rises vertically, mountain valleys also tend to channel the solar-heated air through the valley toward the mountains (Figure 2.2). As the warmed air moves up a valley, cooler air from surrounding areas flows in to replace it. This wind is known as a valley breeze.
Throughout the morning and well into the afternoon, breezes flow up-valley — from the valley floor into the mountains. These breezes tend to reach a crescendo in the afternoon. When the Sun sets, however, the winds reverse direction, flowing down valley.
Winds flow in reverse at night because the mountains cool more quickly than the valley floor. Cool, dense air (high-pressure air) from the mountains sinks and flows down through the valleys like
Fig. 2.2a and 2.2b: Mountain-Valley Breezes. Mountain-valley winds can provide a reliable source of wind power if conditions are just right. (a) Up-valley winds. (b) Down-valley winds.the water in a mountain stream, creating steady and often predictable down-valley or mountain breezes.
Together, valley and mountain winds are known as mountainvalley breezes. As a rule, mountain breezes (down-flowing winds) tend to be stronger than daytime valley breezes.
Mountain-valley breezes typically occur in the summer, a time when solar radiation is greatest. They also typically occur on calm days when the prevailing winds (larger regional winds, which will be discussed shortly) are weak or nonexistent.
Mountain-valley winds also form in the presence of prevailing winds — for example, when a storm moves through an area. In such instances, mountain or valley winds may “piggy back” on the prevailing winds, creating even more powerful (and hence higher energy) winds. When consistently flowing in the same direction, such winds can provide a great deal of power that can be tapped to produce an abundance of electricity.
Sunday, October 30, 2011
Green Business 101
Environmental conservation has recently become the latest buzzword among major countries in the world. As governments of developed countries realize the importance and inevitability of working towards environmental conservation, major business houses are trying to comply with eco friendly operations. All leading companies around the globe have realized an importance for sustainable trade for their long-term survival.Most business has realized that suitable conservation of non-renewable energy resources was the ultimate way to attain lasting existence of businesses and mankind. Utilizing oil resources continuously without concern for future has already raised eyebrows and caused havoc in U.S. auto industry. Demand for alternate biodiesel is in constant rise. People are opting for new opportunities of any alternate energy source. Solar energy long promised to develop as a major energy supply but lately there has been no significant achievement as regards to solar power satisfying the human demand for energy.Also different industries that depend on nature for their raw material requirements are under pressure. They need to shift to eco-friendly production ways that would enable sustained business on a long-term scenario. U.S. paper industry has come forward for the protection of forests and agreed to work towards forests conservation. Increasing global demand for paper has led to an erosion of numerous trees of Cumberland hardwoods - thus threatening the ecological system of the place. Unless immediate preventive steps were exercised the region would not be left with any forest resource to further facilitate human survival and growing industrial needs. Ways to conserve forests include using recycled paper waste and also managing forest resources in a more sustainable way. Major paper industry giants have recently come forward as a positive step for working towards environmental conservation and minimizing uncontrolled use of trees for paper manufacturing.Many government organizations, business companies and also non-profit-concerns are operating worldwide to enhance commerce and techniques that promote environment conservation. Ways to promote research work for alternate fuels and encouraging business to practice recycling of products are becoming increasingly popular among in U.S. and other concerned countries.Emphasis to find different sources of energy apart for oil reserves is always being researched. Wind energy, solar energy, bio-fuels, wave energy and many others have been tried and tested for efficient replacement of non-renewable power resource. Many options have also achieved significant amount of success in helping conservation of oil sources that is fast disappearing from earth surface.Hybrid automobiles have been invented that run on bio-diesel as a measure to find a way for reducing large amounts of oil consumption in U.S. Governments in many countries have introduced certain measures upon corporates to work towards responsible environmental protection. Ways to find new energy efficient methods for production are sought, that not only promotes healthy living conditions but also reduce manufacturing costs for industries. Many industries are actively taking part in a race for achieving eco-friendly manufacturing techniques and using recycled wastes. Realization for proper disposal of industrial wastes only after their proper treatment is essential for nature conservation. Recently a new approach for green building materials has gained a lot of popularity among building constructors to encourage ecological protection.
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