With the world economy growing at a fast pace, energy demand too has been witnessing a sharp rise in the past few decades, with demand mainly originating from the big developing economies of Asia, namely, India and China. Factors such as high population growth, growing urbanization and changing lifestyles in these developing nations are behind the increase in demand for energy. According to International Energy Agency (IEA) estimates, during 1990-2008, while world population increased by around 27%, energy use increased by around 39%. Consequently, average per person consumption of energy has seen a rise of 10% for the same period. The year 2010 has seen a further increase of around 5% in the world energy consumption levels.
Most of the countries in the world use coal, oil and natural gas as their primary sources of energy. Around 90% of the total global energy requirement is met through these non-renewable energy sources. This heavy reliance on fossil fuels poses certain major concerns. Most importantly, these sources are limited. So, it is only a matter of time before these resources are exhausted completely. Another important factor that works against the heavy use of fossil fuels is that they are detrimental to the environment. The use of fossil fuels leads to emission of greenhouse gases which causes global warming. Also, these fuels are a major source of air, water and soil pollution.
All these factors have created a need for alternative energy sources such as wind, solar and hydropower. .
These renewable sources of energy are infinite and produce almost negligible pollution. Across the world, several countries have taken various initiatives to increase the usage of alternative sources of energy. According to the US Energy Information Administration's (EIA) Annual Energy Review data, in 2010, consumption of renewable sources in the US was about 8 quadrillion Btu (1 quadrillion is the number 1 followed by 15 zeros) which contributed about 8% of all energy used nationally.