Fossil fuels being the main source of climate-changing emissions are known to many. Over the first decade of the 21st century, the world has seen an exponential increase in the use of renewable energy resources, which means the era of renewables has arrived. Renewable energy refers to replenishable or inexhaustible power source, namely solar energy, wind energy, geothermal energy, biofuels, tidal and hydro-power. As science has confirmed that the increase of greenhouse gases that causes global climate change is in proportion of fossil fuel consumption, different countries have to deliver carbon-reduction promises in the international framework. Emissions reduction can be achieved through increasing energy efficiency and using more renewable energy resources. Recently, Greenpeace International has released a report on global electricity market development that shows renewables have become the world’s new favourite. In 2010, the market share of renewables was the largest in history. Since the end of 1990s, the development pace of wind and solar power has surpassed that of all the other power-generating technologies. The world has added the total installed capacity of renewables by 430 million kilowatts, equivalent of 45% of China’s current installation power capacity. Last year, globally the use of renewables grew by 87 million kilowatts, surpassing the development of coal-fired power for the first time.
In fact, unlike fossil fuels and nuclear energy, most of the renewables are not that controversial. It is only the availability of appropriate technologies which is a matter of wider discussions. The following sections will briefly introduce and evaluate major types of renewables.