The potential of renewable energy sources is enormous as they can in principle meet many times the world’s energy demand. Renewable energy sources such as biomass, wind, solar, hydropower, and geothermal can provide sustainable energy services, based on the use of routinely available, indigenous resources. A transition to renewables-based energy systems is looking increasingly likely as their costs decline while the price of oil and gas continue to fluctuate.In the past 30 years solar and wind power systems have experienced rapid sales growth, declining capital costs and costs of electricity generated, and have continued to improve their performance characteristics. In fact, fossil fuel and renewable energy prices, and social and environmental costs are heading in opposite directions and the economic and policy mechanisms needed to support the widespread dissemination and sustainable markets for renewable energy systems are rapidly evolving.

It is becoming clear that future growth in the energy sector will be primarily in the new regime of renewable energy, and to some extent natural gas-based systems, not in conventional oil and coal sources.Because of these developments market opportunity now exists to both innovate and to take advantage of emerging markets to promote renewable energy technologies, with the additional assistance of governmental and popular sentiment. The development and use of renewable energy sources can enhance diversity in energy supply markets, contribute to securing long term sustainable energy supplies, help reduce local and global atmospheric emissions, and provide commercially attractive options to meet specific energy service needs, particularly in developing countries and rural areas helping to create new employment opportunities there.Introduction Over the last 200 years, people have become more and more dependent on energy that they dig out of the ground.In the 1700’s, almost all our energy came from wind, water, firewood, or muscle power. The wind powered our windmills and sailing ships.

Water powered our water wheels. Firewood did our cooking and heated our homes. Muscle power (human or animal) did just about everything else. All these energy sources came from the sun, since solar energy drove wind and rain, grew trees, and grew crops to nourish our animals and ourselves.

All these energy sources were also renewable, since wind kept blowing, rivers kept flowing, and trees and crops kept growing.About 1800, we began to get much of our energy from coal dug out of the ground. About 1900 we began to drill for oil and natural gas. By 1950 these “fossil fuels” had mainly displaced the older energy sources except for water power.

Fossil fuels come from the decayed remains of prehistoric plants and animals, so their energy also comes, originally, from the sun. In some parts of the world new fossil fuels are being formed even today. But we are using fossil fuels at a far greater rate than they are being created, using up energy stored over hundreds of millions of years in a few hundred years.After 1950, we began to use atomic energy from uranium dug from the ground. Uranium is not a fossil fuel, and its energy does not originate from the sun.

But uranium, like fossil fuels, is non-renewable: once it’s used up, it’s gone forever.Over the past 25 years, use of older renewable energy sources has increased and we have begun to use new renewable energy sources as well. We have realized that our fossil and atomic fuels will not last forever, and that their use contributes to environmental pollution.Renewable energy – which basically comes from the sun in one way or another – provides opportunities for an unlimited, sustainable energy supply with low environmental impact. And renewable energy is not just something for the future, but something we can use in our homes today.

What are Renewable Sources of Energy?True renewable energy sources are energy supplies that are refilled by natural processes at least as fast as we use them. All renewable energy comes, ultimately, from the sun. We can use the sun directly (as in solar heating systems) or indirectly (as in hydroelectric power, wind power, and power from biomass fuels). Renewable energy supplies can become exhausted if we use them faster than they become replenished. If used wisely, however, renewable energy supplies can last forever.

The use of renewable energy sources can save us money, assure that our grandchildren and great grandchildren will have enough energy, and free us from the uncertainties of depending on other energy supplies.Types of Renewable Energy Sources There are several renewable energy sources that are in use today. Listed below are brief descriptions of these resources:Hydropower Water also, is a renewable energy source since it is recharged through the cycle of evaporation and precipitation. Its power was known since ancient years and was exploited through dams, water mills and irrigation systems. The energy of the falling or moving water can be harnessed by various technologies. Water wheels can transform it directly into mechanical energy (i.

e. water mills), turbines and electrical generators can transform it into electricity. Hydropower plants convert the energy of flowing water into electricity.This is primarily done by damming rivers to create large reservoirs and then releasing water through turbines to produce electricity. Hydropower results in no emissions into the atmosphere but the process of damming a river can create significant ecological problems for water quality and for fish and wildlife habitat.

Biomass Biomass is second to hydropower as a leader in renewable energy production. Biomass as a fuel consists of organic matter such as industrial waste, agricultural waste, wood, and bark. Biomass can be burned directly in specially designed power plants, or used to replace up to15% of coal as a fuel in ordinary power plants. Biomass burns cleaner than coal because it has less sulfur, which means less sulfur dioxide will be emitted into the atmosphere.Biomass can also be used indirectly, since it produces methane gas as it decays or through a modern process called gasification. Methane can produce power by burning in a boiler to create steam to drive steam turbines or through internal combustion in gas turbines and reciprocating engines.

The largest use of biomass energy in Virginia is the forest products industry. Furniture plants, sawmills, and paper mills usually burn their wood waste to produce heat and electricity. Many homeowners use firewood or pellets for winter heat.Geothermal Geothermal energy refers to the energy stored and created inside the earth in the form of thermal energy.

At times this energy is released to the surface through volcanoes and geysers, or is available constantly e.g. through hot springs. Geothermal energy can be harnessed to produce electricity or for heating and cooling purposes.

It can be acquired from deep underground reservoirs through drilling, or from other geothermal reservoirs closer to the surface. Geothermal energy can be used in residential applications. Geothermal power plants use high temperatures deep underground to produce steam, which then powers turbines that produce electricity.Geothermal power plants can draw from underground reservoirs of hot water or can heat water by pumping it into hot, dry rock. High underground high temperatures are accessed by drilling wells, sometimes more than a mile deep. In one sense, this geothermal energy is not renewable, since sometime in the future the core of the earth will cool.

That time is so far off (hundreds of millions of years) that that we think of it as renewable. Geothermal heat pumps use compressors to pump heat out of the earth (for winter heating) or into the earth (when running as air conditioners in summer). The energy they pump into and out of the earth is renewable, since it is replaced by the cycle of the seasons. The energy that runs the compressor can either be renewable or conventional.

Solar Energy With this term we refer to the energy provided by the sun through radiation. The sun is the most powerful source of energy and this energy is free, as long as we exploit it! Solar energy comes directly from the power of the sun and is used to produce electricity, to produce heat, and for light. Technologies are categorized as either active or passive. Active technologies convert solar energy into a form we can use directly either electrical or thermal. Such are photovoltaic cells that convert sunlight directly into electrical energy, like the picture over right, the solar collectors for domestic hot water heating or even solar space heating and cooling, the solar concentrators that use mirrors to focus solar irradiation and generate intense heat, turning water to steam and generating electricity using certain machines and even solar ovens.

Wind Power The energy of wind has been known and exploited for millenniums, either in windmills or in sailing. Nowadays, we can exploit wind energy using special blades to capture wind and machines to transform it to electrical energy. Wind turbines are installed both onshore and offshore in places where wind speed is generally high and constant. Wind power is produced by the energy of the wind turning aerodynamic blades mounted to a hub. The hub is connected to a shaft that turns a generator. Large utility-scale wind turbines range in size from 50 kilowatts to over four megawatts.

Smaller wind towers (under 50 kW) are suitable for residential and agricultural use.Ocean or Marine Energy This is a renewable energy that is underexploited so far. It refers to the mechanical energy carried by ocean waves and tides or to the thermal energy of the ocean coming from the sun. Covering almost 70% of earth surface, oceans may prove to be the renewable energy of the future, however harnessing ocean energy to produce electricity is not cost-effective currently.Conclusions In conclusion, we believe that the promise of renewable energy has now become a reality.

Because of these developments, market opportunity exists now to both innovate and to take advantage of emerging markets, with the additional assistance of governmental and popular sentiment. The development and use of these sources can enhance diversity in energy supply markets, contribute to securing long term sustainable energy supplies, and make a contribution to the reduction of local and global atmospheric emissions.Finally, we conclude that current energy producers are in the best position to capture new renewable energy markets. These producers have the capital needed to make forays into these markets, and the most to lose if they do not invest and renewable energy technologies continue to flourish.

We believe that artful introduction and integration of renewable energy technologies into energy production systems, along with encouragement from the public sector where appropriate, can provide a path that eventually leads to heavy reliance on renewable energy systems in the future. This future would be more environmentally and socially sustainable than one we would achieve by following a more “conservative” path based on continued reliance on fossil fuels. This latter path in many ways implies higher risks to human and ecological health and welfare over time, and it is a path that is increasingly difficult to justify based on the performance that renewables are now achieving.