Renewable Energy
Energy has always existed naturally since the beginning of life on the earth, energy supplying and consumption is the major concern of human. Renewable energy is generally defined as energy that is collected from resources which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services. Nowadays, there are a lot of technologies in the field of renewable energy.