Renewable energy comes from natural resources that are constantly replenished. These resources include rivers, oceans, wind, sunlight, geothermal heat and biomass (material from living organisms such as plants and algae). Unlike fossil fuels—coal, oil and natural gas—renewable energy resources will not be used up within humanity’s foreseeable future. Renewable energies are sometimes called alternative energies, as they are alternatives to fossil fuels. Nuclear power is not currently classified as a renewable energy because it needs a supply of uranium, which is not naturally renewed. Renewable energies are used for generating electricity, heating of buildings and water, cooking, vehicle fuel and off-grid energy for rural homes that are not connected to the electricity grid.

Updated 23rd July 2026

Why turn to renewable energy?

The burning of fossil fuels in power stations and vehicles releases carbon dioxide into the air. This is a greenhouse gas that contributes to global warming. Burning fossil fuels also releases other pollutants, leading to acid rain and smog. Many people are also concerned by the radioactive waste created by nuclear power.
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Reserves of fossil fuels are being used up faster than they are formed. They are also not spread evenly across the world. This leaves some countries unable to meet their own need for fossil fuels. They are also vulnerable to rises in the cost of importing them.

In contrast, every country has access to some renewable energy resources, giving the chance of “energy security”. Many renewable energy technologies, such as solar panels, wind turbines and hydropower, are suitable for use in rural areas in developing countries. Access to renewable energy could lift millions of people living in these regions out of poverty.

Hydropower

Hydropower, which uses the energy of falling and running water, is mainly used to generate electricity. In a hydro-electric power station, the water from a river is stored in a reservoir behind a dam. Some of the water from the reservoir is allowed to flow out through inlets below the water level and along pipes into the turbines inside the power station. Each turbine has angled blades that are spun by the force of the water. A shaft connects the turbines to generators. An electrical generator consists of a magnet surrounded by copper wire. The turbine makes the magnet spin, producing an electric current in the wire.
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Dams are also useful for supplying water to cities and farms, and for controlling flooding downstream. However, the creation of a reservoir can displace large numbers of people and wildlife. China is the world’s largest producer of hydro-electricity, meeting 18% of its electricity needs with power stations such as the Three Gorges Dam. Small dams, called micro hydro projects, are sometimes used in the developing world to supply electricity to isolated homes and villages.

Tidal power

Tidal power converts the energy of tides into other forms of energy. Although tidal power is not yet widely used, it has the potential to supply a large portion of the world’s electricity. Two forms of tidal power generation are currently in operation. Tidal stream generators are machines placed in the flow of water that use the tidal movement to turn turbines.

Wave power captures the energy of ocean waves and harnesses it to do work, such as electricity generation. Some wave power devices, such as surface attenuators, float on the water surface. The rise and fall of the waves drives pumps, which are linked to generators. Oscillating water column devices are partly underwater and make use of air trapped in one of their chambers. The movement of waves squeezes the air through a turbine.
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Overtopping devices use the power of waves to fill a reservoir to a higher level than the surrounding ocean. That higher water is released through turbines. Oscillating wave surge converters have one end fixed to the seabed while the other is free to move with the waves, using the movement to generate electricity. Wave power is not yet widely used, but further wave farms are in development. Key concerns with all wave power devices are the possible disruption and injury of sea creatures.

Wind power

Wind power currently supplies around 7.8% of the world’s electricity. Wind farms are being built across the globe, and wind power has the potential to meet all the world’s electricity needs. However, for this to happen, wind farms would need to be built over large areas, particularly on exposed hillsides and offshore, where the wind is strongest. Some people oppose wind farms because they find turbines ugly.

Floating wind turbines

Most offshore wind turbines are anchored to the ocean floor on fixed foundations, limiting them to depths of about 50 metres (165 feet). Floating turbines are tethered to the sea bed by mooring lines, allowing the turbine to generate electricity in much deeper waters, where winds are usually stronger and more consistent. Being positioned away from the coast reduces their impact on views.

Floating offshore wind is still in its early stages. But experts say the new technology could become much more significant if ways could be found to reduce costs (currently they are about double those of fixed offshore wind) and address fishing industry concerns that the turbine cables could interfere with fishing equipment. 
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Developing floating wind turbines opens up vast areas of the ocean to generate renewable wind power. The world’s first floating wind farm, Hywind Scotland, lies 24 kilometres (15 miles) offshore in the North Sea from Peterhead, Aberdeenshire, where the water is up to 120 metres (400 feet) deep. Here, five floating offshore wind turbines deliver 30 megawatts, sufficient to power approximately 20,000 households.

Solar power

Solar power converts sunlight into energy using either photovoltaics or concentrated solar power. Photovoltaic cells, also called solar cells, convert light into electric current. They do this using the photovoltaic effect, in which photons of light excite electrons in atoms in the cell, allowing them to become part of a current in an electric circuit.

​​​​​​​Today, solar panels, made up of photovoltaic cells, are increasingly installed on roofs or built into the walls of homes, often providing a renewable alternative to the grid electricity supply. A photovoltaic power station, also known as a solar park, solar farm or solar power plant, is made up of a large array of solar panels supplying electricity to the grid. The vast Gonghe Talatan Solar Park in Qinghai, China—which is close to the land area of Singapore—is the largest solar park in the world.
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Concentrated solar power is used to generate electricity in power plants in some of the world’s sunniest regions, such as the southern USA and Spain. The method uses mirrors or lenses to concentrate sunlight into a small area, creating heat. This usually heats water to drive a steam turbine, which is connected to an electrical generator.

Geothermal energy is heat generated and stored inside the Earth. Some of that heat was generated by the Earth’s formation, while the rest is continuously generated by the radioactive decay of minerals. In the past, the harnessing of geothermal heat was only possible near tectonic plate boundaries, where high temperatures are reached close to the Earth’s surface. Today, improved methods mean that geothermal energy can be harnessed in a wider range of areas.
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Twenty-six countries use geothermal energy for electricity production. Of all these countries, the USA generates the most electricity from geothermal energy, while the Philippines is number one in Asia, Italy in Europe, New Zealand in Oceania, and Kenya in Africa. The electricity is generated by using geothermal heat to boil water, creating steam to turn turbines. Geothermal heat can also be used directly for heating buildings and powering industrial processes.

Biomass

There are five main types of biomass used for fuel: wood, “energy crops” grown especially for fuel, agricultural waste, food waste and industrial waste. Raw biomass—such as wood, hay and animal manure—is often burnt as fuel for cooking and heating, particularly in the developing world.

​​​​​​​When raw biomass is inconvenient to use—as in the case of sawdust and agricultural and domestic waste—it can be processed into usable forms, such as pellets, cubes or other biofuels. Although biomass fuels release fewer pollutants than fossil fuels, they do release some carbon dioxide when burnt.

Gas biofuels can be burnt to generate electricity, used as fuel for heating and cooking, or to power vehicles. A commonly produced gas biofuel is biogas. It is a mixture of gases produced by the breakdown of organic matter such as crops, agricultural waste, domestic waste, manure and sewage. It can be produced at landfill sites or by using anaerobic digesters, which use micro-organisms to break down matter.

Waste-to-energy

Incineration is the most common method of converting waste products (such as domestic and industrial waste) into energy. After all recyclable materials have been removed, the waste is burnt in a waste-to-energy plant. This heats water to create steam, which powers turbines linked to electrical generators. Incinerators must strictly control the release of pollutants. Newer waste-to-energy methods produce liquid or gas fuels from waste: for example, anaerobic digestion produces biogas, fermentation produces the liquid fuel ethanol, and gasification can produce burnable wood gas.

Each year, using sunlight, plants turn more than 1000 billion tonnes of CO₂ into organic matter: sugars that serve as food for the plants. The technology for capturing sunlight and using it as a renewable energy source already exists in the form of photovoltaic cells, which convert it to electricity—although this energy cannot be stored. An artificial photosynthesis system that mimics what happens in plants could create an endless supply of electricity and in a storable form, too. It also puts to use the excess CO₂ in the air that acts as a greenhouse gas causing global warming.
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Hydrogen and methanol

Two renewable fuel technologies in development are hydrogen and methanol power. Hydrogen, which must first be extracted from compounds such as water or methane, is usable in fuel cells as a generator of electricity. Methanol, an alcohol, can be made from biomass or manufactured via a process using carbon dioxide and hydrogen. An alternative biofuel for internal combustion engines, as a liquid it is easier to store than gas fuels, is biodegradable and has a low toxicity. Methanol fuel is currently used by racing cars, but is not in widespread use otherwise. Burning methanol results in carbon emissions, however, whereas burning hydrogen releases only water.