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A major advantage of renewable energy is that it can be regenerated, therefore it is sutainable and will never run out. More importantly, renewable energy is environment friendly and produces little or no waste products that may pollute or have harmful effects on the environment.

Some countries using renewable energy as an alternative source of energy are also showing increased economic benefits, especially in various regional areas. Most of these projects are location far away from metropolitan cities. They have been able to increase the use of local services as well as increase tourism.

One of the general disadvantages of using renewable energy is that it is difficult to generate huge quantities of electricity similar to that using conventional fossil fuel (as it case of PV). Another problem is with the reliability of its energy supply. Since it is naturally generated, renewable energy are dependent on the weather conditions at the time and in the region of use.

It also has another drawback. It is relatively more expensive to acquire and set up the equipments necessary for the generating electricity. However,  initial cost is generally offset by the long term benefit.

Negative consequences of renewable technology

To combat global warming and the other problems associated with fossil fuels, the all nations must switch to renewable energy sources like sunlight, wind, and biomass. However, all renewable energy technologies are not appropriate to all applications or locations. As with conventional energy production, there are environmental issues to be considered. Some of the key environmental impacts associated with renewable technologies especially hydropower is given below.

The development of hydropower has become increasingly problematic in the United States and other developed nations. And small-scale hydro development has not met expectations either.

Environmental regulations affect existing projects as well as new ones. For example, a series of large facilities on the Columbia River in Washington will probably be forced to reduce their peak output by 1,000 MW to save an endangered species of salmon. Salmon numbers have declined rapidly because the young are forced to make a long and arduous trip downstream through several power plants, risking death from turbine blades at each stage. To ease this trip, hydropower plants may be required to divert water around their turbines at those times of the year when the fish attempt the trip. And in New England and the Northwest, there is a growing popular movement to dismantle small hydropower plants in an attempt to restore native trout and salmon populations.

That environmental concerns would constrain hydropower development in Nepal is perhaps ironic, since these plants produce no air pollution or greenhouse gases. Yet, as the salmon example makes clear, they affect the environment. The impact of very large dams is so great that there is almost no chance that any more will be built in the United States, although large projects continue to be build in many developing countries. The reservoirs created by such projects frequently inundate/submerge large areas of forest, farmland, wildlife habitats, scenic areas, and even towns. In addition, the dams can cause radical changes in river ecosystems both upstream and downstream.

Small hydropower plants using reservoirs can cause similar types of damage, but on a smaller scale. Some of the impacts on fish can be mitigated by installing “ladders” or other devices to allow fish to migrate over dams, and by maintaining minimum river-flow rates; screens can also be installed to keep fish away from turbine blades. In one case, flashing underwater lights placed in the Susquehanna River in Pennsylvania direct night-migrating American shad around turbines at a hydroelectric station. As environmental regulations have become more stringent, developing cost-effective mitigation measures such as these is essential.

Despite these efforts, however, hydropower is almost certainly approaching the limit of its potential in the United States. Although existing hydro facilities can be upgraded with more efficient turbines, other plants can be refurbished, and some new small plants can be added, the total capacity and annual generation from hydro will probably not increase by more than 10 to 20 percent and may decline over the long term because of increased demand on water resources for agriculture and drinking water, declining rainfall (perhaps caused by global warming), and efforts to protect or restore endangered fish and wildlife.

In most of the developed countries like US , hydropower may decline over the long term because of increased demand on water resources for agriculture and drinking water, declining rainfall (perhaps caused by global warming), and efforts to protect or restore endangered fish and wildlife.

Fundamental of Solar Energy

September 2, 2009

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Wind Energy Lecture II

June 26, 2009

Lecture by Prof. S. Banerjee from Indian Institute of Technology (IIT) Kharagpur

Wind Energy Lecture I

June 26, 2009

Wind Energy

June 14, 2009

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What are the conventional and non-conventional sources of renewable energy?

Conventional : Energy that has been used from ancient times is known as conventional energy. Coal, natural gas, oil, and firewood are examples of conventional energy sources. (or usual) sources of energy (electricity) are coal, oil, wood, peat, uranium.

Non-conventional (or unusual) sources of energy include:
• Solar power
• Hydro-electric power (dams in rivers)
• Wind power
• Tidal power
• Ocean wave power
• Geothermal power (heat from deep under the ground)
• Ocean thermal power (the difference in heat between shallow and deep water)
• Biomass (burning of vegetation to stop it producing methane)
• Biofuel (producing ethanol (petroleum) from plants

We hope that all the conventional sources will become rare, endangered and extinct, as they produce lots of carbon dioxide that adds to the greenhouse effect in the atmosphere (uranium leaves different dangerous byproducts).

And we similarly hope that all the non-conventional sources will become conventional, common, and every day, as they are all free, green and emit no carbon dioxide (well, biomass does, but it prevents the production of methane which is a greenhouse gas 21 times more dangerous that CO2).

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