Reality → Energy → World energy → Renewables
The bulk of renewable energy is used for electricity generation. In 2023, about 30% of the world’s electricity was generated from renewables. The following sources are involved:
Total world installed capacity is about 1,000 GW, of which China's share is about one third. The largest dams are Three Gorges (22 GW) and Xiluodu (13.9 GW), with two additional sites that started partial operation ( Baihetan and Wudongde). Outside of China, there is only one other dam of similar size in operation (Itaipu, Brazil/Paraguay). Worldwide, the best sites for dams have already been taken and public resistance to new constructions is strong due to environmental and social issues. More benign run-of-the-river projects are generally much smaller (even down to pico size), require transmission over relatively long distances, and cannot provide reliable output at all times.
About 1,000 GW were installed worldwide at the end of 2023, of which about 45% in China. More than 90 % of installed world capacity is located onshore. Wind farms range in size from a few MW to more than 1,000 MW. Capacity factors range from 25 to 45 %. The highest factors are attributable to offshore locations, but this economic advantage is normally lost through their higher costs of installation and maintenance.
The Vestas V164 , an offshore turbine rated up to 10 MW, has a total height of 220 m and a rotor diameter
of 164 m.
Typical characteristics of common 2-3 MW onshore turbines are: 3 blades, pointed into wind by motor-control; pitch-controlled variable speed (10-20 rpm,
max. speed at blade tips about 300 km/h, operating at wind speeds 3-30 m/s); gearbox and double fed induction generator and frequency converter, or, more recently, direct drive and multi-pole synchronous generator coupled with AC/DC and DC/AC conversion for better adjustment to grid.
Offshore wind power is technically and economically challenging. About 75 GW, accounting for 7% of world's total installed wind capacity, were installed by the end of 2023. The locations are split in roughly equal proportion between Europe and China. The UK and Germany hold most European offshore wind farms.
During the last 5 years (2019 to 2023) global photovoltaic (PV) solar energy capacity has been growing at an average annual rate of 24%. The top four countries are China, the United States, India, and Japan. In addition to the growing number of commercial photovaltaic installations there have also been some (mostly experimental and subsidized) investments in concentrated solar power and solar thermal energy.
Land availability and costs pose constraints. To install 1 GW photovoltaic power, about 25 km2 of land is needed, about 10 times the area occupied by a coal-fired power plant of equal capacity but much higher utilization. In labs, efficiencies up to 40% can be achieved with rare semiconductor elements, but large-scale use poses material, price, and availability problems. Still, even with a poor energy conversion of 10 %, the recoverable energy from the Sun's irradiation theoretically could cover the world's present total electricity demand (see Sheet).
Biomass-generated electricity is often a byproduct of processing agricultural crops and/or waste for biofuel and gas production. Due to the high CO2 emissions from burning biomass, direct use for electricity generation is restricted to cogeneration in special cases (e.g., the world’s largest biomass power plant burns wood waste from a connected paper mill in a fluidized bed to produce process steam, district heat and electricity.
Drilling for geothermal energy is expensive and carries a high risk of failure. Once a subterranean heat source is discovered, the conversion into electrical energy is fundamentally inefficient due to low temperature differences. Over time, sinking temperatures of the reservoir require additional drill holes. High mineral and gas content of the water can cause corrosion and scaling. Rather than for electricity generation, the relatively low temperature water from geothermal wells is primarily used for district heating and thermal pools (present thermal use is about two times larger than electricity use).
The world's only two operating tidal power stations are at Siwah Lake, South Korea, and Rance, France, with 254 and 240 MW installed capacity, respectively. Most other tidal installations are much smaller research stations without economic output. The largest tidal project under construction is probably the MeyGen project in Scotland. Diverse wave power projects so far have been unsuccessful.