Airflow can be used to operate wind turbines. Modern wind turbines on an industrial scale range from about 600 kW to 5 MW of rated power, although turbines with a nominal power of 1.5-3 MW have become the most common for commercial use. The largest generation capacity of a single onshore wind turbine installed reached 7.5 MW in 2015. The available wind power is a function of the cube of the wind speed, so that when the wind speed increases, the power increases. until you reach the maximum power. particular turbine. [41] Areas with stronger and more consistent winds, such as offshore sites and high altitude, are prime locations for wind farms. Loading times generally fullThe wind turbines vary between 16 and 57% per year, but could be higher in particularly favorable offshore sites. [42]

Electricity generated by wind responded to nearly 4% of global electricity demand in 2015, with nearly 63 GW of new wind capacity installed. Wind power was the main source of new capacity in Europe, the United States and Canada, and the second source in China. In Denmark, wind energy has accounted for more than 40% of electricity demand, while Ireland, Portugal and Spain have met almost 20% each.

Overall, the long-term technical potential of wind energy is estimated at five times the current global energy output, which is 40 times the current electricity demand, assuming that all the necessary practical hurdles have been overcome. This would require the installation of wind turbines over large areas, particularly in higher wind resource areas, such as offshore. Since offshore wind speeds are on average 90% higher than those of land, offshore resources can provide much more energy than onshore wind turbines. [43] In 2014, global wind generation was 706 terawatt hours, or 3% of total global electricity. [44]


In 2015, hydroelectricity generated 16.6% of total global electricity and 70% of all renewable electricity. [45]  Since water is about 800 times denser than air, even a slow stream of water, or a moderate swell, can produce considerable amounts of energy. There are several forms of water energy:

  • Historically, hydropower came from the construction of large hydroelectric dams and reservoirs, which are still popular in third world countries. The most important is the Three Gorges Dam (2003) in China and the Itaipu Dam (1984) built by Brazil and Paraguay.
  • Small hydropower systems are hydroelectric facilities that typically produce up to  50 MW  of energy. They are often used on small rivers or as a low impact development on large rivers. China is the largest producer of hydroelectricity in the world and has more than 45,000 small hydropower plants. [46]
  • Run – of – the – river hydroelectric plants derive their kinetic energy from the rivers without creating a large reservoir. This style of production can still produce a great deal of electricity, such as the Chief Joseph Dam on the Columbia River in the United States.

Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32% of global hydropower in 2010. For the countries with the highest percentage of electricity from renewable sources, the top 50 are mostly hydroelectric. China is the largest producer of hydropower, with 721 terawatt hours of production in 2010, representing about 17% of domestic electricity consumption. There are now three hydroelectric plants of more than 10 GW: the Three Gorges Dam in China, the Itaipu Dam on the border between Brazil and Paraguay and the Guri Dam in Venezuela. [47]

Wave power, which captures the energy of ocean surface waves, and tidal energy, which converts tidal energy, are two forms of future potential hydroelectric power; However, they are not yet widely used commercially. A demonstration project operated by the Ocean Renewable Power Company on the Maine Coast and connected to the grid exploits the tidal energy of the Bay of Fundy, which has the highest tidal current in the world. The conversion of thermal energy from the oceans, which uses the temperature difference between deep and cold surface waters, currently has no economic feasibility.


Solar energy, radiating light and the heat of the sun, is harnessed with a range of ever – changing technologies, such as solar heating, photovoltaics, concentrated solar energy (CSP), photovoltaic concentrator. (CPV), solar architecture and artificial photosynthesis. [48]  [49] Solar technologies are generally characterized as passive solar or solar assets, depending on how they capture, convert and distribute solar energy. Passive solar techniques include orienting a building towards the sun, selecting materials with favorable thermal mass or light scattering properties, and designing spaces that naturally circulate the air. Active solar technologies include solar thermal energy, using solar collectors for heating, and solar energy, converting sunlight into electricity either directly using photovoltaic (PV), or indirectly using solar energy concentrated (CSP).

A photovoltaic system converts light into electric DC (DC) by taking advantage of the photoelectric effect. [50]  Solar photovoltaic energy has evolved into a multi – billion dollar, fast – growing industry, continues to improve its cost – effectiveness, and has the greatest potential for all renewable technologies with the CSP. [51]  [52] Concentrated Solar Energy (CSP) systems use lenses or mirrors and tracking systems to focus much of the sunlight into a small beam. Commercial solar power plants were first developed in the 1980s. CSP-Stirling has by far the highest efficiency among all solar energy technologies.

In 2011, the International Energy Agency stated that “the development of affordable, inexhaustible and clean solar energy technologies will have huge long-term benefits and will strengthen countries’ energy security by leveraging a resource indigenous, inexhaustible and import – independent, improve sustainability, reduce pollution, reduce the costs of climate change mitigation, and keep the fossil fuel price lower than the figures These benefits are global hence the additional costs of incentives for rapid deployment should be seen as learning investments – they must be spent wisely and need to be widely shared. [48]Italy has the largest proportion of solar electricity in the world, in 2015, solar energy provided 7.8% of electricity demand in Italy. [53]  In 2016, after another year of rapid growth, solar energy generated 1.3% of global energy. [54]


High temperature geothermal energy comes from the thermal energy produced and stored in the Earth. Thermal energy is the energy that determines the temperature of the material. The geothermal energy of the Earth comes from the original formation of the planet and the radioactive decay of minerals (in proportions currently uncertain  [55]  but probably about equal  [56]  ). The geothermal gradient, which is the difference in temperature between the core of the planet and its surface, leads to a continuous conduction of thermal energy in the form of heat from the nucleus to the surface. The adjective  geothermal  comes from the Greek roots geo  , meaning earth, and  thermos , meaning heat.

The heat used for geothermal energy can come from the depths of the Earth to the heart of the Earth – 6000 km (4000 miles) deep. At the core, temperatures can reach over 9000 ° F (5000 ° C). The heat goes from the nucleus to the surrounding rock. Extremely high temperatures and pressures cause some rocks, commonly known as magma, to melt. Magma convects upward because it is lighter than solid rock. This magma then heats the rock and water in the crust, sometimes up to 700 ° F (371 ° C). [57]

Since the thermal springs, geothermal energy has been used for bathing since the Paleolithic period and for space heating since Roman times, but it is now better known for the production of electricity. [58]

Low temperature geothermal energy  [28] refers to the use of the earth’s outer crust as a thermal battery to facilitate renewable thermal energy for heating and cooling buildings, and other refrigeration and industrial uses. In this form of geothermal energy, a geothermal heat pump and a land-coupled heat exchanger are used together to move thermal energy into the earth (for cooling) and out of the ground (for heating) on ​​a seasonal basis variable. Low temperature geothermal (GHP) technology is an increasingly important renewable technology as it reduces the total annual energy loads associated with heating and cooling, and it flatten the electrical demand curve by eliminating extreme electricity needs in summer and winter. . Thus, low-temperature geothermal energy / GHP becomes a growing national priority with support for the multiple tax credit [59]  and focuses on the ongoing movement towards net zero energy. [60]  [29]  New York has just passed a law  [61] Requiring GHP at all times is economic with 20-year funding, including the social cost of carbon. [62]  [63]


Biomass is a biological material derived from living or recently living organisms. It is most often plants or plant-derived materials, specifically called lignocellulosic biomass. [64]  As a source of energy, biomass can either be used directly by combustion to produce heat, or indirectly after being converted to various forms of biofuel. The conversion of biomass into biofuel can be achieved by various methods that are generally classified into: thermal ,  chemical  and  biochemical methods   . Wood remains the largest source of biomass energy today; [65] The Examples include forest residues – such as dead trees, branches and trees – yard cuts, wood chips and even municipal solid waste. In the second sense, biomass includes plant or animal matter that can be converted into fiber or other industrial chemicals, including biofuels. Industrial biomass can be grown from many types of plants, including miscanthus, switchgrass, hemp, corn, poplar, willow, sorghum, sugarcane, bamboo,  [66]  and a variety of tree species, ranging from eucalyptus to palm oil (palm oil).

Vegetable energy is produced by crops grown specifically for use as fuel with high biomass production per hectare with low energy consumption. Some examples of these plants are wheat, which generally yields 7.5-8 tons of grain per hectare, and straw, which generally yields 3.5-5 tons per hectare in the United Kingdom. [67]  Grain can be used for liquid transportation fuels while straw can be burned to produce heat or electricity. Vegetable biomass can also be degraded from cellulose to glucose by a series of chemical treatments, and the resulting sugar can then be used as a first-generation biofuel.

Biomass can be converted into other forms of usable energy such as methane or transport fuels such as ethanol and biodiesel. Rotting garbage and agricultural and human wastes all release methane – also known as landfill gas or biogas. Crops, such as corn and sugar cane, can be fermented to produce transportation fuel, ethanol. Biodiesel, another transportation fuel, can be produced from leftover food products such as vegetable oils and animal fats. [68]  In addition, liquid biomass (BTLs) and cellulosic ethanol are still under investigation. [69]  [70] There is a lot of research involving algae fuel or biomass derived from algae because of the fact that it is a non-food resource and can be produced at rates 5 to 10 times higher than those of other types of algae. land-based agriculture, such as corn and soybeans. Once harvested, it can be fermented to produce biofuels such as ethanol, butanol and methane, as well as biodiesel and hydrogen. The biomass used for electricity generation varies by region. Forest by-products, such as wood residues, are common in the United States. Agricultural waste is common in Mauritius (sugar cane residues) and in South-East Asia (rice husks). Livestock residues, such as poultry waste, are common in the UK. [71]

Biofuels include a wide range of fuels derived from biomass. The term covers solid, liquid and gaseous fuels. [72] Liquid biofuels include bioalcohols, such as bioethanol, and oils, such as biodiesel. Gaseous biofuels include biogas, landfill gas and synthetic gas. Bioethanol is an alcohol produced by the fermentation of the sugar components of plants and is made mainly from sugar and starch. These include maize, sugar cane and, more recently, sorghum. The latter crop is particularly suited to dryland cultivation and the International Crops Research Institute for the Semi-Arid Tropics is currently studying the possibility of providing fuel and feed and feed in dry arid regions. Asia and Africa. [73]

With advanced technology under development, cellulosic biomass, such as trees and grasses, are also used as raw materials for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form, but it is generally used as a gasoline additive to increase the octane number and improve vehicle emissions. Bioethanol is widely used in the United States and Brazil. The energy costs to produce bio-ethanol are almost equal to those of bio-ethanol. However, according to the European Environment Agency, biofuels do not address the problems of global warming. [74] Biodiesel is made from vegetable oils, animal fats or recycled fats. It can be used as a fuel for vehicles in its pure form, or more commonly as a diesel additive to reduce the levels of particulate matter, carbon monoxide and hydrocarbons from diesel powered vehicles. Biodiesel is produced from oils or fats using transesterification and is the most common biofuel in Europe. Biofuels provided 2.7% of global transportation fuel in 2010.  [75]

Biomass, biogas and biofuels are burned to produce heat and electricity and, in so doing, harm the environment. Pollutants such as sulfur oxides (SO  x  ), nitrous oxides (NO  x  ) and particulate matter (PM) are produced from the combustion of biomass; The World Health Organization estimates that 7 million premature deaths are caused each year by air pollution. [76]  Burning biomass is an important factor. [76]  [77]  [78]


Energy storage is a collection of methods used to store electrical energy on an electrical grid, or off. Electric power is stored during periods when generation (particularly of intermittent power plants such as renewable electricity sources such as wind power, tidal power, solar energy) exceeds consumption, and is returned to the grid when production falls below consumption. Pumped-storage hydropower is used for more than 90% of all grid energy storage.