SOLAR POWER AS AN ALTERNATIVE ENERGY SOURCE

Solar power is the technology of obtaining usable energy from the light of the Sun. Solar energy has been used in many traditional technologies for centuries and has come into widespread use where other power supplies are absent, such as in remote locations and in space. It is a renewable energy source and produces no greenhouse emissions so it is seen by many as an ideal energy source to combat climate change. Its application is spreading as the environmental costs and limited supply of other power sources such as fossil fuels are realized.

Solar energy is currently used in a number of applications:

• Heat (hot water, building heat, cooking)
• Electricity generation (photovoltaics, heat engines)
• Desalination of seawater.

Advantages and disadvantages of solar power

Advantages

The amount of solar energy intercepted by the Earth every minute is greater than the amount of energy the world uses in fossil fuels each year. Solar electric generation has the highest power density among renewable energy sources.

Solar power is also pollution free during use. Production end wastes and emissions are manageable using existing pollution controls. Production end wastes and emissions are manageable using existing pollution controls. Enhanced decommissioning and recycling technologies are under development.

Facilities can operate with little maintenance or intervention after initial setup. Solar electric generation is economically competitive where grid connection or fuel transport is difficult, costly or impossible. Examples include satellites, island communities, remote locations and ocean vessels. Once the initial capital cost of building a solar power plant has been spent, operating costs are low when compared to existing power technologies. The cost is also falling as technology develops and becomes more efficient.

When grid connected, solar electric generation can displace the highest cost electricity during times of peak demand (in most climatic regions), can reduce grid loading, and can eliminate the need for local battery power for use in times of darkness and high local demand; such application is encouraged by net metering. Time-of-use net metering can be highly favorable to small photovoltaic systems. Also, grid connected solar electricity can be used locally thus minimizing transmission/distribution losses.

Disadvantages

To date, the main problems using solar energy are that solar cells are costly, requiring a large initial capital investment, and the lack of efficiency in turning solar power into electricity. Solar panels currently have an efficiency of 7 to 17.7% which has worked well for hot water systems. To get enough energy for larger applications, a large number of photovoltaic cells is needed. This increases the cost of the technology and requires a large plot of land.

Like electricity from nuclear or fossil fuel plants, solar power can only realistically be used to power transport vehicles by converting light energy into another form of stored energy (e.g. battery stored electricity or by electrolyzing water to produce hydrogen) suitable for transport. Also, solar cells produce DC which must be converted to AC when used in currently existing distribution grids. This incurs an energy loss of 4-12%.

Solar power at the Earth's surface has a number of disadvantages which limit its ability to provide large amounts of energy effectively. It is most available in certain areas of favorable climate and latitude. That is, areas near the tropics and which are relatively cloud free. It is obviously not available at night.

Types of technologies

Many technologies have been developed to make use of solar radiation. Some of these technologies make direct use of the solar energy (e.g. to provide light, heat, etc.), while others produce electricity.

Solar heating systems

Solar hot water systems use sunlight to heat water. They may be used to heat domestic hot water or for space heating. These systems are basically composed of solar thermal collectors and a storage tank.

Solar cooking

Solar Cookers use sunshine as an alternative to fire for cooking . A solar box cooker traps the sun’s energy in an insulated box; such boxes have been successfully used for cooking, pasteurization and fruit canning. Solar cooking is helping many developing countries, both reducing the demands for local firewood and maintaining a cleaner breathing environment for the cooks.

Solar lighting

Solar lighting or day lighting is the use of natural light to provide illumination. Day lighting features include building orientation, window orientation, exterior shading, sawtooth roofs, clerestory windows, light shelves, skylights and light tubes. These features may be incorporated in existing structures but are most effective when integrated in a solar design package which accounts for factors such as glare, heat gain, heat loss and time-of-use.

Photovoltaics

Solar cells, also referred to as photovoltaic cells, are devices or banks of devices that use the photovoltaic effect of semiconductors to generate electricity directly from sunlight. Until recently, their use has been limited because of high manufacturing costs. Cost-effective use has been in remote applications such as roadside emergency telephones, remote sensing, cathodic protection of pipe lines, and limited “off grid” home power applications. A third use has been in powering orbiting satellites and other spacecraft.

Solar thermal electric power plants

Solar thermal energy can be focused on a heat exchanger, and converted in a heat engine to produce electric power or applied to other industrial processes. Power towers use an array of flat, movable mirrors to focus the sun’s rays upon a collector tower (the target). The high energy at this point of concentrated sunlight is transferred to a working fluid for conversion to electrical energy.

A solar updraft tower is a relatively low-tech solar thermal power plant where air passes under a very large agricultural glass house (between 2 and 8 km in diameter), is heated by the sun and channeled upwards towards a convection tower. It then rises naturally and is used to drive turbines, which generate electricity.

An energy tower is an alternative proposal to the solar updraft tower. It is driven by spraying water at the top of the tower, evaporation of water causes a downdraft by cooling the air thereby increasing its density, driving wind turbines at the bottom of the tower. It requires a hot arid climate and large quantities of water.
Solar pond
A solar pond is simply a pool of water which collects and stores solar energy. It contains layers of salt solutions with increasing concentration (and therefore density) to a certain depth, below which the solution has a uniform high salt concentration. It is a relatively low-tech, low-cost approach to harvesting solar energy. The heat trapped in the salty bottom layer can be used for heating of buildings, industrial processes, generating electricity or other purposes.

Solar chemical

Solar chemical is any process that harnesses solar energy by absorbing sunlight in a chemical reaction in a way similar to photosynthesis in plants but without using living organisms. No practical process has yet emerged. A promising approach is to use focused sunlight to provide the energy needed to split water into its constituent hydrogen and oxygen in the presence of a metallic catalyst such as zinc. While metals, such as zinc, have been shown to drive photoelectrolysis of water, more research has focused on semiconductors. Further research has examined transition metal compounds, in particular titanium, niobium and tantalum oxides.

Click here to go to the home page www.climatechange.110mb.com

This information is licensed under the GNU Free Documentation. It is derivative of articles on Climate Change, Global Warming and related environmental issues at http://en.wikipedia.org