The world's energy mix is changing. Across the world, major companies and countries are turning to renewable sources such as wind, solar and geothermal to green their operations and become more sustainable.
But what do all these terms mean? Here, CNBC's "Sustainable Energy" takes a look at some of the most important words and phrases in the renewable energy lexicon.
Biomass
The International Energy Agency (IEA) defines biomass as being "any organic matter" that is "available on a renewable basis."
This could include organic waste from industrial sources, or feedstock from plants or animals.
Bioenergy is energy produced from "products derived from biomass," according to the IEA. It represents around 9% of the planet's primary energy supply, the agency says.
Geothermal
Described by the U.S. Department of Energy (DOE) as a "vital, clean energy resource," geothermal energy refers to heat from below the Earth's surface which can be used to produce renewable energy.
The DOE adds that geothermal energy "supplies renewable power around the clock" but emits little or no greenhouse gases.
Hydropower
Energy that comes from the flow of water. Turbines are crucial components of hydropower systems — it's the powerful flow of water that "drives" them, producing electricity.
The IEA describes hydropower as the world's largest source of renewable electricity.
Renewable energy
A phrase that encompasses a vast amount of other words, terms and energy production methods.
The U.S. Energy Information Administration describes it as "energy from sources that are naturally replenishing but flow-limited."
These sources are "virtually inexhaustible in duration." Examples of renewable energy include solar, wind, geothermal and wave power.
Solar power
Energy from the sun. Can be harnessed in several ways, including through photovoltaic and concentrated solar power systems (CSP).
Photovoltaic refers to a way of directly converting light from the sun into electricity.
For CSP systems, the Solar Energy Industries Association describes them as using mirrors "to concentrate the Sun's energy to drive traditional steam turbines or engines that create electricity."
Tidal power
Energy that's produced from the tides of the sea.
According to the major utility EDF, tidal power makes use of "the differential between low and high tides to generate electricity." Tidal power is predictable, carbon-free and inexhaustible.
In August 2018, it was announced that a tidal stream turbine had generated record levels of production in its initial year of testing at the European Marine Energy Centre in Orkney, Scotland.
The 2-megawatt SR2000 turbine produced more than 3 gigawatt hours of renewable electricity in 12 months.
Wave power
Wave power is described by the IEA as being the "kinetic and potential energy associated with ocean waves."
The European Commission has described "ocean energy" as being both abundant and renewable. Ocean energy could potentially contribute around 10% of the European Union's power demand by 2050, according to the Commission.
Wind energy
Perhaps counter-intuitively, wind is actually a form of solar energy.
As the U.S. Department of Energy explains, it's caused by three simultaneous events, namely: the atmosphere being unevenly heated by the sun; irregularities of the Earth's surface; and the Earth's rotation.
Wind turbines — which can vary in size and be located onshore and offshore — are used to take the wind's kinetic energy and turn it into mechanical power.
