11-08-2012, 11:58 AM
SOLAR HYBRID CHIMNEY
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ABSTRACT
Solar thermal hybrid chimney is a new method for producing electric power from a solar-wind hybrid system. It combines three old and proven technologies: the chimney effect, the greenhouse effect, and the wind turbine. Energy from sunlight is converted to heat by a large solar collector. The collector is a transparent membrane suspended several meters off the ground, which can be made of glass or a strong transparent polymer. Sunlight penetrates this membrane, and the solar radiation is converted to heat upon hitting the ground. The air underneath the membrane quickly increases in temperature due to the greenhouse effect and flows towards the chimney, which, through the stack effect, becomes the lowest point of pressure in the system. This continuous airflow spins a turbine located at the base of the chimney. Inside the chimney wind turbines convert the wind’s energy into electricity. This method can also be useful during night time. The project work requires a significant area of land. A small-scale solar updraft tower may be an attractive option for remote regions in developing countries.
Need Of Solar Thermal Power:
The future of this earth and mankind substantially depends on our ability to slow down the population increase in the “Third World” by civilized means. The key is to increase the standard of living, to overcome the inhumane poverty and deprivation.
To achieve this traditional means will not suffice any longer as exemplified by a "paradox on”. Those countries where agriculture provides more than 20 % of the gross national product are those also stricken by starvation!
Development requires mechanization and energy. Energy consumption increases proportionally to the gross national product or prosperity while simultaneously the population growth will decrease exponentially.
Many developing countries possess hardly any energy sources and their population doubles every 15 to 30 years! The results are commonly known: Civil wars and fundamentalism. If these developing countries are provided with only a humane and viable minimum of energy the global energy consumption will drastically increase!
India’s Power Scenario:
India’s current electricity installed capacity is 135 401.63MW. Currently there is peak power shortage of about 10 % and overall power shortage of 7.5 %.
The 11th plan target is to add 1,00,000 MW by 2012 and MNRE has set up target to add 14,500 MW by 2012 from new and renewable energy resources out of which 50 MW would be from solar energy. The Integrated Energy Policy of India envisages electricity generation installed capacity of 800 000 MW by 2030 and a substantial contribution would be from renewable energy. This indicates that India’s future energy requirements are going to be very high and solar energy can be one of the efficient and eco-friendly ways to meet the same.
Solar Energy potential:
India is located in the equatorial sun belt of the earth, thereby receiving abundant radiant energy
from the sun. The India Meteorological Department maintains a nationwide network of radiation
stations, which measure solar radiation, and also the daily duration of sunshine. In most parts of
India, clear sunny weather is experienced 250 to 300 days a year. The annual global radiation
varies from 1600 to 2200 kWh/m
, which is comparable with radiation received in the tropical
and sub-tropical regions. The equivalent energy potential is about 6,000 million GWh of energy
per year. Figure 1 shows map of India with solar radiation levels in different parts of the country.
It can be observed that although the highest annual global radiation is received in Rajasthan,
northern Gujarat and parts of Ladakh region, the parts of Andhra Pradesh, Maharashtra, Madhya
Pradesh also receive fairly large amount of radiation as compared to many parts of the world
especially Japan, Europe and the US where development and deployment of solar technologies is
maximum.
Solar thermal power generation technologies:
Solar Thermal Power systems, also known as Concentrating Solar Power systems, use concentrated solar radiation as a high temperature energy source to produce electricity using thermal route. Since the average operating temperature of stationary non-concentrating collectors is low (max up to 1200C) as compared to the desirable input temperatures of heat engines (above 3000C), the concentrating collectors are used for such applications. These technologies are appropriate for applications where direct solar radiation is high. The mechanism of conversion of solar to electricity is fundamentally similar to the traditional thermal power plants except use of solar energy as source of heat.
In the basic process of conversion of solar into heat energy, an incident solar irradiance is collected and concentrated by concentrating solar collectors or mirrors, and generated heat is used to heat the thermic fluids such as heat transfer oils, air or water/steam, depending on the plant design, acts as heat carrier and/or as storage media. The hot thermic fluid is used to generated steam or hot gases, which are then used to operate a heat engine. In these systems, the efficiency of the collector reduces marginally as its operating temperature increases, whereas the efficiency of the heat engine increases with the increase in its operating temperature.
Introduction To Solar Hybrid Chimney:
A wide range of existing power technologies can make use of the solar energy reaching Earth. Basically, all those ways can be divided into two basic categories: transformed for use elsewhere or utilized directly – direct – and involving more than one transformation to reach a usable form – indirect. The Solar Chimney Power Plant (SCPP) is part of the solar thermal group of indirect solar conversion technologies. More specifically, a natural phenomenon concerning the utilization of the thermal solar energy involves the earth surface heating and consequently the adjacent air heating by the sun light. This warm air expands causing an upward buoyancy force promoting the flow of air that composes the earth atmosphere. The amount of energy available due to the upward buoyancy force associated with the planet revolution is so vast that can generate catastrophic tropical cyclones with disastrous consequences.
History Of Solar Hybrid Chimney:
One of the earliest descriptions of a solar chimney power station was written in 1903 by Isidoro
Cabanyes, a Spanish artillery colonel. He made public the proposition “Proyecto de motor solar”
(solar engine project) introducing an apparatus consisting of an air heater attached to a house
with a chimney. In the house interior, a kind of wind propeller was placed with the purpose of
electricity production. In 1926 Prof Engineer Bernard Dubos proposed to the French Academy of
Sciences the construction of a Solar Aero-Electric Power Plant in North Africa with its solar
chimney on the slope of the high height mountain. The author claims that an ascending air speed
of 50 m/s can be reached in the chimney, whose enormous amount of energy can be extracted by
wind turbines.