18.1: Renewable Energy History and Consumption
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Renewable energy sources can be replenished within human lifespans. Although renewable energy is often classified as wind, solar, geothermal, hydropower (hydroelectric energy/hydroelectricity), and biofuels (biomass energy), all forms of renewable energy arise from only three sources: the light of the sun (wind, solar, hydropower, and biofuels), the heat of the earth’s crust (geothermal), and the gravitational attraction of the moon and sun (tidal energy; figure \(\PageIndex{a}\)). Sunlight provides by far the largest contribution to renewable energy. The sun provides the heat that drives the weather, including the formation of high- and low-pressure areas in the atmosphere that make wind. The sun also generates the heat required for vaporization of ocean water that ultimately falls over land creating rivers that drive hydropower, and the sun is the energy source for photosynthesis, which creates biomass. The sun is also responsible for the energy of fossil fuels, created from the organic remains of plants and sea organisms compressed and heated in the absence of oxygen in the earth’s crust for tens to hundreds of millions of years. The time scale for fossil fuel regeneration, however, is too long to consider them renewable in human terms.
Most renewable energy sources have a relatively small carbon footprint, meaning that they do not significantly contribute to climate change. However, building dams for hydropower (hydroelectric energy) does release methane, a potent greenhouse gas. Renewable energy sources are pollution free (except biofuels), and they typically have minimal environmental impact (except habitat loss from dams). Up to this point, however, no single source of renewable energy is sufficient. They generally are paired with other energy sources.
Strong interest in renewable energy in the modern era arose in response to the oil shocks of the 1970s, when the Organization of Petroleum Exporting Countries (OPEC) imposed oil embargos and raised prices in pursuit of geopolitical objectives. The shortages of oil, especially gasoline for transportation, and the eventual rise in the price of oil by a factor of approximately 10 from 1973 to 1981 disrupted the social and economic operation of many developed countries and emphasized their precarious dependence on foreign energy supplies. The reaction in the United States was a shift away from oil and gas to plentiful domestic coal for electricity production and the imposition of fuel economy standards for vehicles to reduce consumption of oil for transportation. Other developed countries without large fossil reserves, such as France and Japan, chose to emphasize nuclear (France to the 80% level and Japan to 30%) or to develop domestic renewable resources such as hydropower and wind (Scandinavia), geothermal (Iceland), solar, biomass and for electricity and heat. As oil prices collapsed in the late 1980s, interest in renewables, such as wind and solar that faced significant technical and cost barriers, declined in many countries. Other renewables, such as hydropower and biomass, continued to experience growth. As climate change worstens, the solar and wind energy has expanded globally in recent years.
Renewable energy accounted for 11.4% of total global energy consumption and 26.3% of global electricity generation in 2019 (figure \(\PageIndex{b}\)). In the United States, renewable energy also accounted for about 11% of total energy consumption but only 17.6% of electricity generation. Nearly half (43%) of total renewable energy use in the U.S. is from biofuels. For electricity generation in the U.S., wind was the greatest contributor (7.1%) followed by hydropower (7.0%), solar (1.7%), biomass (1.4%), and geothermal (0.4%).
Attribution
Modified by Melissa Ha from Renewable Energy and Challenges and Impacts of Energy Use from Environmental Biology by Matthew R. Fisher (licensed under CC-BY)