Preface to special issue on "Renewable Energy"

The world is faced with twin threats, (1) inadequate and insecure supplies of energy at affordable prices, and (2) environmental damage due to overconsumption of energy (IEA 2006)[1]. Global demand for energy keeps growing. Society’s growing requirements for energy are resulting in significant changes in those same ecosystems, both in the search for energy sources, and as a result of energy use patterns. Given that energy is a fundamental requirement for supporting development in all economies, the challenge is to sustainably provide it without driving further loss of biodiversity. It is necessary to define the trade-offs required, and to develop appropriate mitigation and adaptation strategies. There is an intimate connection between energy, the environment and sustainable development. Clearly, a strong relation exists between energy efficiency and environmental impact. One of solutions to current environmental issues in terms of energy conservation is an effective utilization of renewable energy. “Renewable energy” is the energy that comes from solar radiation, astronomical tide and geothermal heat which are naturally replenished. Solar radiation is the source of wind, wave and biomass. About 19% of global final energy consumption is shared by renewable energy in 2008 coming from traditional biomass with 13% and 3% from hydropower. New renewable energy such as, small hydropower, modern biomass, wind, solar, geothermal, and biofuels, account for 2.7% that are growing very rapidly (see Figure 1). Wind power is growing at the rate of 30% annually, with a worldwide installed capacity of 157,900 (MW) in 2009, and is widely used in Europe, Asia, and the United States. At the end of 2009, cumulative global photovoltaic (PV) installations surpassed 21,000 MW and PV power stations are popular in Germany and Spain. Solar thermal power stations operate in the USA and Spain. Brazil has one of the largest renewable energy programs in the world, involving production of ethanol fuel from sugar cane, and ethanol now provides 18% of the country’s automotive fuel. Ethanol fuel is also widely available in the USA. During the five years from the end of 2004 through 2009, worldwide renewable energy capacity grew at rates of 10-60 %t annually for many technologies. For wind power and many other renewable technologies, growth accelerated in 2009 relative to the previous four years. More wind power capacity was added during 2009 than any other renewable technology. However, “grid-connected PV” increased the fastest of all renewables technologies, with a 60% annual average growth rate for the five years period. All forms of energy are expensive, but as time progresses, renewable energy generally gets cheaper, while fossil fuels generally get more expensive. 1 【Review】