‘What are renewables?’ defines renewable energy and provides a brief history of its use. It focuses on energy generated by solar, wind, and hydropower. These energy sources are renewable, in the sense that they are naturally replenished within days to decades. Only a few years ago, giving up our reliance on fossil fuels to tackle global warming would have been very difficult, as they are so enmeshed in our society and any alternative was very expensive. Nearly all of the sources of energy up to the 18th century were from renewables, after which time the world increasingly used fossil fuels. They powered the industrial revolution around the globe, and now provide most of our energy. But this dependence is unsustainable, because their use causes global warming, climate change, and pollution. Other than hydropower, which grew steadily during the 20th century and now provides almost a sixth of the world’s electricity demand, renewable energy was a neglected resource for power production for most of this period, being economically uncompetitive. But now, renewables are competitive, particularly through the support of feed-in tariffs and mass production, and governments are starting to pay more attention to clean energy, as the threat of climate change draws closer. Moving away from fossil fuels to renewables to supply both heat and electricity sustainably has become essential.
Special Issue on Wind Turbine Aerodynamics II
