Hydro & Wind
A hydroelectric power plant, often located near a dam, converts the kinetic energy of water flowing downstream into electricity by forcing the water through a hydraulic turbine that is connected to a generator. The water then exits the turbine and is returned to a stream or riverbed below the dam.
The primary advantage of hydroelectric dams is their ability to handle seasonal (as well as daily) high-peak loads. When the electricity demands drop, the dam simply stores more water, which then provides more flow when it releases, thereby producing more electricity.
Some electricity generators use water dams to store excess energy, often during the night, by using the electricity to pump water up into a basin. Electricity can be generated when demand increases.
A wind turbine is a rotating machine that converts the kinetic energy present in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is typically called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aerogenerator.
A wind farm is a group of wind turbines in the same location used for production of electric power. In a wind farm, individual turbines are interconnected with a medium voltage (usually 34.5 kV) power collection system and communications network. At a substation, this medium-voltage electrical current is increased in voltage with a transformer for connection to the high-voltage transmission system.
A large wind farm may have from a few dozen to up to 100 individual wind turbines, and cover an extended area of hundreds of square miles. The land between the turbines may be used for agricultural or other purposes. A wind farm may also be located offshore to take advantage of the winds present on the surface of an ocean or lake.
Similar to solar energy, wind energy is favored by environmentalists as an alternative to fossil fuels, because it is plentiful, renewable, widely distributed, clean and produces no greenhouse gas emissions. However, wind farms are not universally welcomed due to their visual impact and other effects on the environment.
With wind energy, all of the available output must be used immediately. To match supply with demand, other renewable energy resources, such as hydropower, can be used.