Reality → Energy → World energy → Electricity
| Electricity generation | ||
|---|---|---|
| PWh/a | ||
| fossil fuels | 18.0 | 61% |
| hydro | 4.2 | 14% |
| other renewable | 4.8 | 16% |
| nuclear | 2.7 | 9% |
| total | 29.8 | 100% |
About 60% of the world's 2023 electricity is based on fossil fuels (coal 35%, gas 23%, and oil 2%). Hydro, by far the largest renewable energy, contributes 14%, all other renewables combined (wind, solar, biomass, and geothermal energy) conttribute 16%, and nuclear energy provides 9% of the world's electricity. The dominating coal and gas-fired power plants convert on average about one third of the fuel's energy into electricity [1] . Replacement of coal by gas increases efficiency and reduces emissions, but the long-term prospects of gas are uncertain [2] . Hydro as well as nuclear energy may remain important sources of 'clean' and economic electricity [3] , while wind and solar energy have good prospects for further expansion [4] . In the long-run, electricity might also be generated from exotic new sources, which could include energy recovered from oceans and eventually even nuclear fusion [5] .
The average overall efficiency of existing coal-fired power plants is about 30%. Modern large boiler units (blocks) achieve significantly better conversion efficiencies, as well as cost efficiency through economies of scale. Blocks up to 1100 MW have been built and, if designed to operate with superheated steam (e.g., 600 °C and 260 bar), can achieve efficiencies of up to 45%. Natural gas (CH4) is a more potent and cleaner fuel. In a combined cycle power plant, gas is burned in a gas turbine (Brayton cycle), with the hot exhaust gas driving a conventional steam turbine (Rankine cycle). The combination yields an overall efficiency of 55%.
Gas produces roughly half the CO2 emissions of coal. In the United States, gas surpassed coal in 2016 electricity generation as a consequence of the shale gas boom, which may turn out to be a bubble. Worldwide, resistance to fracking is strong. In 2023, gas-generated electricity in the US exceeded coal-generated electricity by a factor of 2.6, while worldwide it was 35% below coal-generated electricity. Overall, long-term yield and lifetime of gas deposits remain uncertain and use of this valuable and limited energy resource may be prioritized for various industrial applications rather than for power generation.
Electricity from existing hydro dams is probably the world’s lowest-cost electric energy, but the scope for future large-scale expansion is limited because the best dam sites have already been taken. Nuclear energy is 'clean' (i.e. no carbon emissions), but highly controversial due to problems of nuclear waste disposal, risk of power plant accidents, and atomic weapons proliferation. Nevertheless, as a reliable base load provider, the industry may be indispensable during the expected transition period from fossil fuels to renewable energy. China has an ongoing construction program for new nuclear power plants. India, another large contributor to global CO2 emission, maintains ambitious plans for nuclear energy expansion. France obtained about 65 % of its electricity from nuclear power plants in 2023, the United States and Russia about 18%.
Both wind and solar energies have low capacity utilization and occupy large land areas for commercial-scale production. The intermittent output poses problems of storage, grid capacity, and power management. Still, future growth rates are likely to remain high wherever local conditions are favorable (the average annual growth rate of installed global capacity during the last 5 years (2019-2023) was 13% for wind and 24% for solar).
The long-established idea of generating electricity from marine energy has led to a variety of scientifically and technically curious but economically unsuccessful projects that have no commercial impact. Chances for successful nuclear fusion power in the foreseeable future are exceedingly slim, but the ITER project is nevertheless proceeding.