HYDROPOWER
Water movement in general can be utilised to produce what has been termed as 'hydropower'. This may range from ocean waves to falling water and underwater currents. The hydropower system is used to produce electricity by spinning the turbine generator or simply for mechanical purposes.
Currently, hydropower is the most common way to generate electricity worldwide, in the form of renewable energy. Manmade hydropower can help in flood control as well as in irrigation. Depending on the type of the hydro project and the state of the land before the project, the lake produced can be a positive aspect of an aquatic ecosystem.
The structures of a hydropower plant, such as canals, tunnels, dams, reservoirs, access roads, and so on, are useful in relation to the area's development. On the other hand, negative aspects can be: siltation, soil erosion, soil and water salinity, obstruction of the free passage between oceans and rivers, weed growth, floods due to dam failures, as well as possible disease spread by organisms that live in stagnant water, and the possibility of damage to natural resources, such as fish.
In many parts of the world, development within this sector of hydropower is still expanding, mostly for generating electricity.
However, in some Western countries, such as USA, the hydropower has peaked within the last two decades of the last century (ESA21).
SOLAR
Using sunlight and/or sun heat to generate energy in the form of electricity (or for heating systems) is one of the growing ways in which solar energy is used and applied. From the small calculator to the satellites orbiting the earth, solar cells can provide the energy in different ways and in different processes.
The sunlight or heat can be used directly or indirectly, as in the following examples:
Solar Cells
Solar Cells are usually referred to under the name photovoltaic or photoelectric cells. These cells convert sunlight directly into electricity. On a good sunny day, sunlight on one square meter of solar panel can produce enough power to run a 100W light bulb (MNRE, 2008).
Solar Water Heating
In some domestic settings, by pumping water through a pipe painted black the heat from the sun is used to heat water in glass panels placed on the house roof.
This heating system is mostly suitable in places where heat emanating from regular sunshine takes place.
Solar Furnaces
By collecting sun rays (e.g. by the use of mirrors) and concentrating them in a small space, a high temperature can be achieved in a specially designed furnace. Using this design, it was reported that a temperature of 3,000o C was reached at one of Odellio's laboratories in France.
The above are very brief examples of how sunlight and sun heat are currently being used as another type of renewable source of energy.
The positive aspect in using sunlight and sun heat is that there is no waste or pollution. It can be used in sunny countries to get electricity in remote places when connection from the main electricity grid is not possible. Also, it can be used for small domestic appliance (e.g. heating water) as well as for charging batteries.
However, it is costly to convert the solar energy to electricity for large power stations. Also, it can be unreliable in an area where there is no regular sunlight.
WIND
By using the energy from moving air, large blades on windmills rotate to turn the turbines in order to generate electrical, thermal or mechanical energy. Energy (such as the production of electricity) from windmills requires large open spaces with high occurrence of wind throughout the year, in order to make it commercially viable.
The positive aspect of wind energy is that the source of energy is free. It generates no air or water pollution (apart during the hardware manufacturing process when fossil fuels used for this purpose).
The cost of electricity from windmills is declining. However, noise, shades, and light fluctuation, if windmills constructed close to residential areas, can be negative aspects. Also, the limited availability of space with regular wind pattern can be a problem in some parts of the world, plus, the possibility that windmills may harm wildlife, such as birds, is also a concern.
Najib Altawell
References
ESA21 (Environmental science activities for the 21st Century) (2009) Renewable energy: Hydropower.
MNRE (Ministry of New and Renewable Energy) (2008) Solar photovoltaic programme. Government of India.
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