Posted by: PARTHA DAS SHARMA | September 8, 2008

Renewable Energy – to be promoted extensively to save environment:

Renewable Energy – to be promoted extensively to save environment:

Renewable energy is the energy which is made from resources that Mother Nature replaces, such as wind, water and sunshine. Renewable energy is also called “clean energy” or “green power” because it doesn’t pollute the air or the water. In fact, wind, water and sunshine are the cleanest and most abundant sources of energy we have.

However, these abundant and natural sources of renewable energy have few shortcomings, such as unlike natural gas and coal, we can’t store up wind and sunshine to use whenever we need to make more electricity. If the wind doesn’t blow or the sun hides behind clouds, there wouldn’t be enough power for everyone. Another reason why we prefer fossil fuels like coal and natural gas over natural sources of energy is because they’re cheaper. It costs more money to make electricity from wind, and most people aren’t willing to pay more on their monthly utility bills. The prominent sources of renewable energy are:

(i) Wind Power, (ii) Biomass energy, (iii) Hydro power, (iv) Solar power, (v) Geothermal energy.

(i) Wind Power – Wind power is a clean, renewable source of energy which produces no greenhouse gas emissions or waste products. Using the wind to create electricity has been around for a long time. When the wind turns the blades of a windmill, it spins a turbine inside a small generator to produce electricity, just like a big coal power plant. To make enough electricity to serve lots of people, power companies build “wind farms” with dozens of huge wind turbines. Wind farms are built in flat, open areas where the wind blows at least 14 miles per hour. We need to switch to forms of energy that do not produce CO2. Just one modern wind turbine will save over 4,000 tones of CO2 emissions annually (For further details refer Wind Energy).

(ii) Biomass Energy – Biomass means “natural material.” The term bio-energy or biomass, refers to all the Earth’s vegetation and many products and co-products that come from it. Biomass is the oldest known source of renewable energy—humans have been using it since we discovered fire—and it has high energy content. Biomass energy uses natural materials like trees and plants to make electricity. It can also mean waste products like trash. The energy content of dry biomass ranges from 7,000 Btus/lb for straws to 8,500 Btus/lb for wood. Domestic biomass resources include agricultural and forestry wastes, municipal solid wastes, industrial wastes, and terrestrial and aquatic crops grown solely for energy purposes, known as energy crops. When biomass energy is burned, it releases heat – just like the wood logs in your campfire. Some of the common material used includes: (a) Leftover wood from sawmills. (b) Leftover paper and wood waste from paper mills. (c) Corn stalks, corn cobs and seed corn from farms. (d) Paper and cardboard that can’t be recycled in other ways. (e) Fast-growing crops and trees etc.

Some salient points about bio-gas:

* Anaerobic fermentation or digestion is the most promising process for converting organic materials to methane and other gases.

* A simple apparatus can be constructed to produce bio-gas.

* Bio-gas usually contains about 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and other gases.

* The heat value of raw bio-gas is approximately half that of natural gas.

* Take precautions when processing and handling the gas. It is highly explosive and difficult to detect.

The philosophy behind biomass energy includes:

* Growing energy crops,

* Turning garbage into energy,

* Cow power or power from animal waste.

Biomass is an attractive energy source for a number of reasons. First, it is a renewable energy source as long as we manage vegetation appropriately. Biomass is also more evenly distributed over the earth’s surface than finite energy sources, and may be exploited using less capital-intensive technologies. It provides the opportunity for local, regional, and national energy self-sufficiency across the globe. And energy derived from biomass does not have the negative environmental impact associated with non-renewable energy sources. (For further details refer

Energy from Sewage ).

(iii) Hydro Power – A hydro power plant uses river water to make electricity. Hydropower converts the energy in flowing water into electricity. In fact, people have used water power for more than 2,000 years. In modern day, people built dams to control the power of the big mountain rivers. The quantity of electricity generated is determined by the volume of water flow and the amount of “head” (the height from turbines in the power plant to the water surface) created by the dam. The greater the flow and head, the more electricity produced.

A typical hydropower plant includes a dam, reservoir, penstocks (pipes), a powerhouse and an electrical power substation. The dam stores water and creates the head; penstocks carry water from the reservoir to turbines inside the powerhouse; the water rotates the turbines, which drive generators that produce electricity. The electricity is then transmitted to a substation where transformers increase voltage to allow transmission to homes, businesses and factories.

Types of Hydropower Plants – They are of two types (a) Conventional, (b) Pumped storage:

Conventional – Most hydropower plants are conventional in design, meaning they use one-way water flow to generate electricity. There are two categories of conventional plants, run-of-river and storage plants.

Run-of-river plants – These plants use little, if any, stored water to provide water flow through the turbines. Although some plants store a day or week’s worth of water, weather changes—especially seasonal changes—cause run-of-river plants to experience significant fluctuations in power output.

Storage plants – These plants have enough storage capacity to off-set seasonal fluctuations in water flow and provide a constant supply of electricity throughout the year. Large dams can store several years worth of water.

Pumped Storage – In contrast to conventional hydropower plants, pumped storage plants reuse water. After water initially produces electricity, it flows from the turbines into a lower reservoir located below the dam. During off-peak hours (periods of low energy demand), some of the water is pumped into an upper reservoir and reused during periods of peak-demand.

(iv) Solar Power – “Solar” is the Latin word for “sun” – and it’s a powerful source of energy. In fact, the sunlight that shines on the Earth in just one hour could meet world energy demand for an entire year. We can use solar power in two different ways: (a) as a heat source, and (b) as an energy source.

Today we use solar collectors for heating water and air in our homes. We can also use solar energy to make electricity. The process is called photovoltaics. It’s difficult and expensive to make a lot of electricity using photovoltaics – the panels cost a lot, and a lot of open land is needed.

A recent renewed interest in alternative energy technologies has revitalized interest in solar thermal technology, a type of solar power that uses the sun’s heat rather than its light to produce electricity. Although the technology for solar thermal has existed for more than two decades, projects have languished while fossil fuels remained cheap. But solar thermal’s time may now have come — and mirrored arrays of solar thermal power plants, hopefully, will soon bloom in many of the world’s deserts (For further details refer Solar Power – Sustainable Energy ).

(v) Geothermal Energy – The hot lava from a volcano and the hot steam from a geyser both come from underground heat – and we can use that same type of heat in our homes. The system pumps a liquid through the pipes to absorb the heat and brings it back indoors. A device called a “heat exchanger” takes the heat from the liquid and uses it to heat the air inside the home. A geothermal system can cool your house during the summer, too! It just works in reverse, absorbing the heat from the air inside your home and moves it back into the earth. A geothermal heater is also very energy-efficient. Almost none of the energy used is wasted, so it helps keep heating bills very low during the winter.

Development of efficient ‘Energy Storage Technology’ is Need-Of-The-Hour for optimal utilization of renewable energy sources –

* As there is continuous thrust on optimal utilization of the renewable energy sources due to various environmental issues, it has become a challenge to us to deliver proper power quality, keeping reliability of power with stability and efficiency to the industry from these energy sources. The power generation, transmission & distribution system must be able to supply the power reliably while maintaining the power quality through out the year.

* The renewable energy sources like Photo Voltaic Solar Cell, Wind energy system the power production depends upon availability of sunlight & wind respectively so the nature of power available to loads is intermittent, thus making them non-dispatchable sources. With the help of reliable energy storage system the non-dispatchable energy can be made into the dispatchable energy source.

* Therefore, there is urgent need to study different energy storage technology available and to enhance the system performance by properly designing energy storage technology for application in the power system at different stages.

Renewables Global Status Report 2009 Update:


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