Geothermal energy is heat within the earth. The word geothermal comes from the Greek words geo (earth) and therme (heat). Geothermal energy is a renewable energy source because heat is continuously produced inside the earth. People use geothermal heat for bathing, to heat buildings, and to generate electricity.

Pangalengan, Indonesia—In this serene corner of Java, farmworkers pick tea leaves from striped-green hills threaded with pipes. The three-foot-wide pipes carry steam from a broiling underground reservoir, a reminder of the volcano that once erupted. Here, along the volcano-rich Ring of Fire, the Wayang Windu Geothermal Power Station uses the Earth's heat to produce energy that emits few or no greenhouse gases. It aims to expand, because it's discovered what may be the world's biggest hot steam well.

Geothermal energy is heat that comes from inside Earth. In some places, such as Iceland, the heat is so close to the surface it can be easily used as an energy source. In other places holes must be drilled down through rocks to reach the heat. Geothermal energy is harnessed for cooking, bathing, space heating, electrical power generation, and other uses.

For tourists relaxing in the hot springs of Iceland's famous Blue Lagoon, just outside the capital Reykjavik, the issues of climate change and energy security are not likely to be occupying most bathers' minds. But what many visitors may be surprised to know is that the hot water they are sitting in is part of a remarkable journey by one country from oil dependence to a world leader in harnessing renewable energy.

Humans have been harnessing the energy of river currents for centuries, using water wheels spun by rivers initially to process grains and cloth. Today, hydropower provides about 16 percent of the world's electricity, generating power in all but two U.S. states.

People have a long history of using the force of water flowing in streams and rivers to produce mechanical energy. Hydropower was one of the first sources of energy used for electricity generation and is usually the largest single renewable energy source of annual electricity generation in the United States.

Hydroelectricity (also known as hydro) is a well-developed renewable energy technology that has been around for more than a century. Hydro uses flowing water to spin a turbine connected to a generator that produces electricity. The amount of electricity generated depends on the volume of water and the height of the water above the turbine.

The world’s most relied-upon renewable energy source isn’t wind or sunlight, but water. Last year, the world’s hydropower capacity reached a record 1,308 gigawatts (to put this number in perspective, just one gigawatt is equivalent to the power produced by 1.3 million race horses or 2,000 speeding Corvettes). Utilities throughout the globe rely upon hydropower to generate electricity because it is cheap, easily stored and dispatched, and produced with no fuel combustion, meaning it won’t release carbon dioxide or pollutants the way power plants burning fossil fuels such as coal or natural gas do.

Nuclear energy, also called atomic energy, energy that is released in significant amounts in processes that affect atomic nuclei, the dense cores of atoms. It is distinct from the energy of other atomic phenomena such as ordinary chemical reactions, which involve only the orbital electrons of atoms.

Nuclear power is generated by splitting atoms to release the energy held at the core, or nucleus, of those atoms. This process, nuclear fission, generates heat that is directed to a cooling agent—usually water. The resulting steam spins a turbine connected to a generator, producing electricity. About 450 nuclear reactors provide about 11 percent of the world's electricity. The countries generating the most nuclear power are, in order, the United States, France, China, Russia, and South Korea.

Periodically, as with the changing of the seasons, various individuals appear in the media extolling the virtues of nuclear energy, promising a panacea of clean and reliable electricity to solve Australia’s energy crisis. But the truth is far less rosy.

On April 25 and 26, 1986, the worst nuclear accident in history unfolded in what is now northern Ukraine as a reactor at a nuclear power plant exploded and burned. Shrouded in secrecy, the incident was a watershed moment in both the Cold War and the history of nuclear power. More than 30 years on, scientists estimate the zone around the former plant will not be habitable for up to 20,000 years.

The sun has produced energy for billions of years and is the ultimate source for all of the energy sources and fuels that we use today. People have used the sun's rays (solar radiation) for thousands of years for warmth and to dry meat, fruit, and grains. Over time, people developed technologies to collect solar energy for heat and to convert it into electricity.

What is solar energy? Solar energy is energy in the form of light, produced by the Sun. Light from the Sun comes as ultraviolet, visible and infra red rays. Visible light is the spectrum of colours we are used to seeing but ultraviolet and infrared cannot be seen.

The total amount of solar energy incident on Earth is vastly in excess of the world’s current and anticipated energy requirements. If suitably harnessed, this highly diffused source has the potential to satisfy all future energy needs. In the 21st century solar energy is expected to become increasingly attractive as an energy source because of its inexhaustible supply and its nonpolluting character, in stark contrast to the finite fossil fuels coal, petroleum, and natural gas.

In Western Australia, one of the sunniest landscapes in the world, rooftop solar power has been a runaway success. On the state's main grid, which covers Perth and the populated south-west corner of the continent, almost one in every three houses has a solar installation......But there is now so much renewable solar power being generated on the grid that those responsible for keeping the lights on warn the stability of the entire system could soon be in jeopardy.

Tidal energy is produced by the surge of ocean waters during the rise and fall of tides. Tidal energy is a renewable source of energy. During the 20th century, engineers developed ways to use tidal movement to generate electricity in areas where there is a significant tidal range—the difference in area between high tide and low tide. All methods use special generators to convert tidal energy into electricity.

Tidal energy is created using the movement of our tides and oceans, where the intensity of the water from the rise and fall of tides is a form of kinetic energy. Tidal power surrounds gravitational hydropower, which uses the movement of water to push a turbine to generate electricity. The turbines are likened to wind turbines, except they are positioned underwater.

An electric vehicle charging point which uses tidal energy has started operations, providing road users on an island north of mainland Scotland with a new, renewable option for running their cars.

Tidal energy is the energy from the bulk movement of water due to tides. This energy results from the rise and fall of the water level in large bodies of water. Tides are commonly semi-diurnal (two high waters and two low waters each day), or diurnal (one high water and one low water each day).

Western Australia's south coast city of Albany could be a showroom for wave energy technology after the deployment of a monitoring buoy in King George Sound.

Dr Tom Denniss is a man on a mission, designing Australian technology to test the potential for a commercially viable ocean wave system. His pilot project is taking place on King Island between the Australian mainland and Tasmania. “Australia probably has the best, or one of the best, wave climates in the world,” he told SBS News while walking at Sydney’s Cronulla Beach. “The whole southern part of Australia from lower Western Australia right up to New South Wales and including Tasmania is very, very, conducive to this technology.”

If the term “renewable energy” brings to mind a sea of solar panels or towering wind turbines, you’re not alone. It’s becoming more and more common to capture energy from the sun and wind. That’s because these “clean” energy sources generate electricity without polluting our air. Just as important is that they don’t release carbon dioxide into the atmosphere. That greenhouse gas traps the sun’s heat and contributes to our changing climate.

The topic of renewable energy is an evergreen subject, especially, in a world dominated by fossil fuels. Renewable energy is widely talked about in the contemporary world because it is unlimited, which means it’s sustainable and does not emit greenhouse gasses that are detrimental to the environment and human health. A classic example of renewable energy is wave energy.

Wind is a clean and inexhaustible source of energy that can be harnessed to produce power. Historically, wind power in the form of windmills has been used for centuries for such tasks as grinding grain and pumping water. Today sophisticated wind machines known as wind turbines are used in many parts of the world to convert the kinetic energy of wind to electric power.

With eight wind farms commissioned in 2019, adding 837MW of new generating capacity, for the first time in Australia wind energy overtook hydro power as the leading source of renewable energy. Over the course of the year, wind supplied 35.4 per cent of the country’s clean energy and 9.5 per cent of overall electricity – and this growth is not set to slow down anytime soon. Here, we take a look at the sector and some of the most exciting projects underway that will contribute to an expected 5,844MW boost in capacity.

Wind is caused by uneven heating of the earth's surface by the sun. Because the earth's surface is made up of different types of land and water, it absorbs the sun's heat at different rates. One example of this uneven heating is the daily wind cycle.

A project to build a giant island providing enough energy for three million households has been given the green light by Denmark's politicians. The world's first energy island will be as big as 18 football pitches (120,000sq m), but there are hopes to make it three times that size. It will serve as a hub for 200 giant offshore wind turbines.