10-11-2012, 02:28 PM
HYBRID POWER SYSTEM
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INTRODUCTION
Energy is a requirement that is endlessly and exhaustingly utilized the world over. With the increase in the rate of various developmental activities around the world the energy being consumed is also increasing with the result that conventional energy resources are fast getting depleted and even hydrel reserves are proving less than sufficient to satisfy the growing energy demand. As a result consumers around the world have to bear the brunt of increasing power cuts and power costs. Hence for the future power independence is fast becoming a vital requirement. The concept design therefore formulates a system which provides internally generated energy for homes and also integrates a sub system into the household such that the dependence on the electricity board is eliminated.
When thinking about nonconventional source of energy what usually comes to our mind are the existing and extensively used nonconventional sources of energy like solar, tidal, wind, geo thermal heat, biomass .But in countries where we have so fluctuant weather and temperature, to depend on these resources are highly unreliable .That made think out of the box and find a new method of generating energy which should be highly reliable and cost effective, which is a hybrid power system.
A hybrid power system has more than one type of generator-usually a gasoline or diesel-powered engine generator and a renewable energy source such as PV, wind, or hydropower system. For explanation, a solar-wind hybrid system is mainly considered in this report.
A hybrid system is most often used for larger applications such as village power; residential systems where generators already exist; and in applications like telecommunications where availability requirements are near 100 percent. Almost all PV generator hybrid systems include batteries for storage. The most common configuration for a W-generator system is one in which the PV array and the generator each charge the batteries.
NEED OF HYBRID POWER PLANT
Conventional combustion type power generation methods include the combustion of primary fuels like gasoline, natural gas, coal etc where mechanical power is produced by a heat engine that transforms thermal energy, from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics. Therefore, there is always heat lost to the environment. On the other hand, we have nuclear power stations, in which the mechanical energy required for rotating a turbine is obtained from converting water into high energy (KE or PE) steam. For the heating purpose, we use nuclear reaction. The heat emitted from nuclear reactors is used to heat up the water stored in a container. But this method has the main disadvantage of a nuclear power station is the risk factor. If leakages of these nuclear plants occur, it will cause high damage to both biotic and abiotic factors in the surrounding. Also both of these have a disadvantage of atmospheric pollution.
SOLUTION
Usage of clean energy sources is the most acceptable solution. A clean energy source means one which produces energy without making much disturbance to the environment. The examples of such sources are solar energy, wind energy, wave energy, fuel cells etc. But electricity should be produced exactly at the time it is needed. Sun and wind do not meet this requirement. So a special type of power plant should be built to avoid shortage of power and to utilize all available sun and wind power.
HYBRID POWER SYSTEMS
A hybrid power system is nothing but a system that uses more than one source to produces electrical energy. Apart of the existing system in which tying up of outputs of different generating stations, here the different sources of energy are tied up at the point of production that is using two or more fuels for the same device, that when integrated, overcome limitations inherent in either
INTRODUCTION TO WIND ENERGY
Wind result from air in motion. Air in motion arises from a pressure gradient. On a global basis one primary forcing function causing surface winds from the poles toward the equator is convective circulation. Solar radiation heats the air near the equator, and this low density heated air is buoyed up. At the surface it is displaced by cooler more dense higher pressure air flowing from the poles. In the upper atmosphere near the equator the air thus tend to flow back toward the poles and away from the equator. The net result is a global convective circulation with surface wins from north to south in the northern hemisphere.
There is the further complication of boundary layer frictional effects between the moving air and the earth’s rough surface. Mountains, trees, buildings, and similar obstructions impair stream line air flow. Turbulence results and the wind velocity in a horizontal direction markedly increase with altitude near the surface.
Local winds are caused by two mechanisms. The first is differential heating of land and water. Solar isolation during the day is readily converted to sensible energy of the land surface but is partly absorbed in layers below the water surface and partly consume in evaporating some of that water. The land mass becomes hotter than the water, which causes the air above the land to heat up and become warmer than the air above water. The warmer lighter air above the land rises and the cooler heavier air above the water moves into replace it. This is the mechanism of shore breezes. At night, the direction of the breezes is reversed because the land mass cools to the sky more rapidly than the water, assuming a sky. The second mechanism of local winds is caused by hills and mountain sides. The air above the slopes heats up during the day and cools down at night, more rapidly than the air above the low lands. This causes heated air the day to rise along the slopes and relatively cool heavy air to flow down at night.
WIND ENERGY CONVERSION
Traditional windmills were used extensively in the middle Ages to mill grain and lift water for land drainage and watering cattle. Wind energy converters are still used for these purposes today in some parts of the world, but the main focus of attention now lies with their use to generate electricity. There is also growing interest in generating heat from the wind for space and water heating and for glass-houses but the potential market is much smaller than for electricity generation.
The term “wind mill” is still widely used to describe wind energy conversion systems, however it is hardly adopt. Modern wind energy conversion systems are more correctly referred to as ‘WECS’, aero generations’, ‘wind turbine generators’, or simply ‘wind turbines’.
The fact that the wind is variable and intermittent source of energy is immaterial of some applications such as pumping water for land drainage – provided, of course, that there is a broad match between the energy supplied over any critical period and the energy required. If the wind blows, the job gets done; if it does not, the job waits.
PHOTOVOLTAIC PRINCIPLES
The photo-voltaic effect can be observed in nature in a variety of materials that have shown that the best performance in sunlight is the semiconductors as stated above. When photons from the sun are absorbed in a semiconductor, that create free electrons with higher energies than the created there must be an electric field to induce these higher energy electrons to flow out of the semi-conductor to do useful work. A junction of materials, which have different electrical properties, provides the electric field in most solar cells.