Top Renewable Energy Sources

The oil supply crisis of the 1970s greatly influenced the need to diversify the forms of energy and be able to depend less on fossil fuels. At first, alternative fuels were only used in highly-specialized sectors such as space applications. However the increased focus on climate change concerns and a sharp decline in costs pushed the renewable energy sector to leap forward since the 1990s. The important decrease of costs related to alternative forms of energy makes the renewable energy sector the default choice for new projects and an essential tool to achieve climate targets. For instance, in ten years, the costs related to solar photovoltaic (PV) plants dropped by 82% (2009 to 2019).

Renewable energy, often referred to as clean energy, comes from natural sources or processes that are constantly replenished. That is to say, sunlight or wind keep shining and blowing, even if their availability depends on time and weather. 

While the pandemic affected the fossil fuel sector in a negative way; a drop of 9,8% in electricity generation between 2019-2020, it also brought a new momentum to the renewable energy sector. Consequently, the renewable energy sector was the only energy form that grew during the pandemic. In 2020, annual renewable capacity additions increased 45% to almost 280 GW – the highest year-on year increase since 1999.

The many forms of renewable energy have been evolving at different paces, with different challenges and with different costs involved. Here are a few of the top renewable energy sources:

Wind Energy

Wind Energy is one of the fastest growing sources of energy in the world. Kinetic energy formed by the moving air is converted in electricity through a wind turbine. The energy is typically used locally or added to the electrical grid. Wind energy creates no pollution and does not require fuel. The turbines come in various sizes; from small-sized turbines that can power a home, medium-sized turbines that sit on 80m towers, to large-sized turbines that stand on 240m towers with enormous blades. The largest wind farm located near the Irish sea can supply energy to nearly 600,000 houses. California’s latest wind farm project could supply energy to nearly 1,6 million homes by installing floating wind turbines offshore. The wind energy sector is one of the strongest among renewable energy forms, with a global wind capacity that almost doubled in 2020.

Hydroelectric Power

Hydroelectric Power harnesses the power of water in motion to generate electricity. Over 2,000 years ago people in Greece used water to turn the wheel of a mill to grind wheat into flower. There are four main types of hydropower: run-of-river, storage, pumped storage and offshore hydropower. Today most hydroelectric plants control the flow of water that turn the blades of a turbine into electricity. Hydroelectricity is the most used form of renewable energy. Being one of the oldest forms of renewable energy, hydroelectricity has greatly evolved and has become the single largest renewable energy source, with nearly 60% of the total of energy produced each year. 

Solar Power

Solar Power is both renewable and alternative because it will always be abundant, and it emits no greenhouse gases. Photovoltaic (PV), cells are made from silicon or other materials that transform sunlight directly into electricity. Distributed solar systems generate electricity locally, either through rooftop panels or community projects that power entire neighbourhoods. The solar energy sector has seen the biggest growth among all renewable energy forms over the 1990-2018 period, rising by an annual average rate of 37% compared with 23% growth for wind energy, IEA data shows. With a steady decrease in costs since 2010, the solar energy sector reached parity with the fossil fuel sector, yielding new investments interests from governments and companies.

Other renewable energy forms

Biomass Energy

Biomass Energy is energy produced by living or once-living organisms. Examples include wood, energy crops, and waste from forests, yards or farms. Using waste means less goes into landfill. However, this also creates carbon dioxide and methane gas which causes some air pollution. Biomass converting to energy may include direct combustion, thermochemical conversion, chemical and biological. 

Geothermal Power

Geothermal Power is heat derived from the subsurface of the earth. Water or steam carry the geothermal energy to the surface. This key energy source covers a significant amount of the electrical power required in Iceland, El Salvador, New Zealand, and Kenya. Benefits include reliability, cleanliness, low footprint, renewability and versatility. Geothermal power has untapped potential considering that we are not yet capable to reach the hottest and deepest parts of geothermal plants. Conventional geothermal plants reach up to 230 degrees Celsius through holes that go to a maximum of 2km deep. In order to untap the rest of the geothermal potential, the industry needs to develop innovative drills that can take the very high temperatures. When reaching over 375 degrees Celsius, the energy created is 5-10 times bigger. 

Hybrid Power

Hybrid Power systems combines both home wind and solar technology offering advantage over a single system.  For example, in North America, wind is low in the summer but sun shines the brightest and longest. Most of these systems are stand alone or off the grid. Battery banks of 2-3 days are usually used to store the electricity.

Tidal Energy

Tidal Energy is a form of hydropower where turbines generate electricity from tides. They typically include both paddles and turbine to harness the energy created. The first commercial application was in 2007, Strangford Lough (Ireland) where the tide can move 4 meters (13 feet) per second across the strait (narrow passage of water that connects two larger bodies of water). The tidal energy production is still at a very early stage. Construction costs are high and there is an unavoidable impact on the ocean’s ecosystem, as well as a scarcity of suitable locations. Hence the small share of renewable energy coming from tidal energy.


In 2020 renewable energy companies outperformed the fossil fuel majors. A return to increased funding is now forecasted, with the commitment to eight out of then of the world’s largest economies committing to net zero by 2050.

We may have reached the tipping point for energy transition. With the EU focusing on green recovery from COVID-19 alongside many other nations, and the US president elect’s plans for a carbon-free power sector by 2035 (and a net zero economy by 2050), the pace of transition is clear.