Power from renewable energy
[edit]
Power stations can generate electrical energy from renewable
energy sources.
Hydroelectric power station
[edit]
Main article: Hydroelectricity
Hydroelectric power station at Glen Canyon
Dam, Page, Arizona
In a hydroelectric power station water flows through turbines
using hydropower to generate hydroelectricity. Power is captured from the
gravitational force of water falling through penstocks to water
turbines connected to generators. The amount of power available is a
combination of height and water flow. A wide range of Dams may be built to
raise the water level, and create a lake for storing water. Hydropower is
produced in 150 countries, with the Asia-Pacific region generating 32 percent
of global hydropower in 2010. China is the largest hydroelectricity producer,
with 721 terawatt-hours of production in 2010, representing around 17
percent of domestic electricity use.[citation needed]
Solar
[edit]
Main article: Solar power
Nellis Solar Power Plant in Nevada, United States
Solar energy can be turned into electricity either directly in solar cells, or in
a concentrating solar power plant by focusing the light to run a heat engine.
[20]
A solar photovoltaic power plant converts sunlight into direct current
electricity using the photoelectric effect. Inverters change the direct current
into alternating current for connection to the electrical grid. This type of plant
does not use rotating machines for energy conversion. [21]
Solar thermal power plants use either parabolic troughs or heliostats to
direct sunlight onto a pipe containing a heat transfer fluid, such as oil. The
heated oil is then used to boil water into steam, which turns a turbine that
drives an electrical generator. The central tower type of solar thermal power
plant uses hundreds or thousands of mirrors, depending on size, to direct
sunlight onto a receiver on top of a tower. The heat is used to produce steam
to turn turbines that drive electrical generators. [citation needed]
Wind
[edit]
Main article: Wind power
Wind turbines in Texas, United States
Wind turbines can be used to generate electricity in areas with strong,
steady winds, sometimes offshore. Many different designs have been used in
the past, but almost all modern turbines being produced today use a three-
bladed, upwind design.[22] Grid-connected wind turbines now being built are
much larger than the units installed during the 1970s. They thus produce
power more cheaply and reliably than earlier models. [23] With larger turbines
(on the order of one megawatt), the blades move more slowly than older,
smaller, units, which makes them less visually distracting and safer for birds.
[24]
Marine
[edit]
Main article: Marine energy
Marine energy or marine power (also sometimes referred to as ocean
energy or ocean power) refers to the energy carried by ocean
waves, tides, salinity, and ocean temperature differences. The movement of
water in the world's oceans creates a vast store of kinetic energy, or energy
in motion. This energy can be harnessed to generate electricity to power
homes, transport and industries.
The term marine energy encompasses both wave power—power from
surface waves, and tidal power—obtained from the kinetic energy of large
bodies of moving water. Offshore wind power is not a form of marine energy,
as wind power is derived from the wind, even if the wind turbines are placed
over water.
The oceans have a tremendous amount of energy and are close to many if
not most concentrated populations. Ocean energy has the potential of
providing a substantial amount of new renewable energy around the world.[25]
Osmosis
[edit]
Osmotic Power Prototype at Tofte (Hurum),
Norway
Main article: Osmotic power
Salinity gradient energy is called pressure-retarded osmosis. In this method,
seawater is pumped into a pressure chamber that is at a pressure lower than
the difference between the pressures of saline water and fresh water.
Freshwater is also pumped into the pressure chamber through a membrane,
which increases both the volume and pressure of the chamber. As the
pressure differences are compensated, a turbine is spun creating energy.
This method is being specifically studied by the Norwegian utility Statkraft,
which has calculated that up to 25 TWh/yr would be available from this
process in Norway. Statkraft has built the world's first prototype osmotic
power plant on the Oslo fjord which was opened on 24 November 2009. In
January 2014, however, Statkraft announced not to continue this pilot. [26]
Biomass
[edit]
Metz biomass power station
Biomass energy can be produced from combustion of waste green material
to heat water into steam and drive a steam turbine. Bioenergy can also be
processed through a range of temperatures and pressures
in gasification, pyrolysis or torrefaction reactions. Depending on the desired
end product, these reactions create more energy-dense products
(syngas, wood pellets, biocoal) that can then be fed into an accompanying
engine to produce electricity at a much lower emission rate when compared
with open burning.[citation needed]
