Renewable resources

DEFINITION: Natural resources that are capable of replenishing themselves for future use

Nonrenewable resources such as coal, oil, gas, and mineral deposits regenerate themselves too slowly to keep up with human demand; once consumed, they are gone. By contrast, sustainably managed renewable resources can meet current needs and still provide for generations to come. Misuse or overuse, however, can tax renewable resources beyond their ability to recover.

Renewable Resources

The term “renewable resources” is often used interchangeably with “renewable energy.” However, water, soil, wildlife, forests, plants, and are also types of renewable resources. Renewable energy sources, such as wind energy and hydroelectricity, are mainly derived from solar energy in one form or another. Direct solar is usually converted into heat, which can be used for such purposes as heating homes or water. Solar water heating has been used in the southern United States since at least the early twentieth century. In mild climates such as southern Florida, it can easily furnish all the hot water requirements of a typical home. It has also been widely used in tropical countries throughout the world. By 2008 solar photovoltaic systems and wind had become the fastest-growing renewable energy sectors in the United States.

Types of Solar Energy

Passive solar heating, at its most basic, is the heating of a building by solar radiation that enters the building through south-facing windows (north-facing in the Southern Hemisphere). A properly designed passive solar home must have enough interior heat capacity, usually in the form of concrete floors or walls, to be able to keep the house from overheating on a sunny day and to store excess heat for at night. In many parts of North America and Europe, passive solar homes have proved to be economical, because the passive system is part of the house itself (its windows, walls, and floors) and thus adds little or no extra cost. “Passive solar” can also refer to solar water-heating systems that involve no moving parts and consume no electricity. Using local water pressure, cold water flows into a collector, where solar energy heats it; the heated water, which rises to the top of the collector, then flows to a storage tank.

Active solar heating, by contrast, uses air or liquid solar collectors that convert solar radiation into thermal energy, which is stored and distributed using a mechanical system (fans or pumps). Active systems are more complex, cost more, and are more resource-intensive; however, they offer greater efficiency and can be used to retrofit an existing building. Two common types of systems are used to heat water for household use: closed loop, in which a solar collector heats an antifreeze solution which in turn heats a water tank containing potable water; and open loop, a simpler, less expensive scheme in which is routed through the solar collector to be heated before flowing into the tank.

Direct solar radiation can also be used to produce electricity. Concentrated solar power systems employ an array of mirrors that reflect sunlight onto a collector, where the solar heat is stored or converted into mechanical energy. In 2014 the capacity of concentrated solar power plants in the United States reached 1,354 megawatts, according to the Solar Energy Industries Association. Ocean thermal conversion, a concept that has been partially tested, generates electricity using the difference in temperature between the warm, solar-heated upper portions of the ocean and the colder water farther down. As of 2014, no complete ocean thermal conversion plant had yet been built.

Photovoltaic or solar cells are semiconductor devices that generate electricity directly from solar (or other electromagnetic) radiation. Originally developed for artificial satellites after World War II, photovoltaic cells work well and are used to power everything from solar calculators, radios, battery rechargers, and patio lights to electric fences, traffic signal controls, field-deployed scientific equipment, and prevention systems on metal bridges. Their price kept them from gaining widespread use for generating electricity in homes for many years; however, between 2010 and late 2014 the average cost of a photovoltaic panel fell by more than half.

Other Renewable Resources

A less direct type of renewable solar energy is hydroelectricity—electricity generated by water turbines that are turned by water flowing down a river or dropping from a dammed water reservoir. The of the moving water is derived from the gravitational potential energy of water at greater heights, and that energy is ultimately derived from solar radiation that evaporated the water from the oceans, allowing it to rain down in the mountains. An older form of water power was the waterwheel used by millers until well into the nineteenth century. Ocean energy in the form of tidal movement, wave action, and marine currents is another source of hydropower that is gaining increasing attention. Because of the great expense of harnessing tidal energy and the environmental impact on marine life, the tidal power plant that has operated at the mouth of the Rance River in France since 1966 remained the only major facility of its kind until 2011, when the 254-megawatt Sihwa Lake tidal power plant opened in South Korea. Smaller commercial tidal power plants operate in Canada, Russia, China, and Northern Ireland, however, and by 2010 several experimental facilities for producing tide- or wave-generated power were online or under construction around the globe.

Wind energy is also a renewable solar energy resource, because it is the uneven heating of the earth’s land and water areas by the sun that causes winds. Wind has long been used as an energy source: It powered the sailing ships that explored the globe, and it powered the windmills used in Asia and Europe since the Middle Ages to grind grain and pump water. Since the 1920s wind turbines have been used to generate electricity in rural areas of the United States. The Global Wind Energy Council reported that in 2013 the generation capacity of the world’s wind power facilities reached more than 318.1 gigawatts.

Geothermal energy is the heat energy produced beneath the earth’s surface by the decay of naturally occurring radioactive elements. According to a U.S. Geological Survey estimate, if only 1 percent of the thermal energy contained within the uppermost 10 kilometers (6.2 miles) of the planet’s crust could be harnessed, it would provide five hundred times the energy represented by the world’s known oil and gas reserves. While present everywhere beneath the earth’s surface, is commercially exploitable primarily in areas of active or geologically young volcanoes. The western United States accounts for most of the world’s installed geothermal electricity capacity and generation.

Biomass is often defined as the total mass of living organisms in an ecosystem, including both plants and animals, but the term is also used for nonliving biological materials, such as wood from dead trees. The energy stored in is solar energy that has been stored by photosynthesis. Biomass is an important resource not only for human life, because all human food is biomass in one form or another, but also for society in general because biomass materials can be used as a source of energy and chemical compounds, including therapeutic drugs. In 2013 biomass accounted for roughly 24 percent of the total renewable electricity generation (excluding hydropower) in the United States.

Biomass energy resources include solid, liquid, and gaseous fuels. The solid fuels include wood (the major energy resource used in the United States until about 1880) and agricultural wastes such as corn stover (the leaves and stalks left behind after a corn harvest) and sugarcane bagasse (the pulp remaining after juice extraction). These are increasingly being used for industrial electric power generation and home heating. Liquid biomass fuels include and ethanol, both of which can be used in motor vehicle engines. The major gaseous biomass fuel is methane, the main constituent of the called natural gas; methane is generated by the (oxygen-starved) of manure and other organic materials.

Bibliography

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Near-Term Projections for Demand in Renewable Resources

According to the World Economic Forum, the installation of renewable energy facilities reached an all-time high in 2021. This trend led many to predict this lead to a similar increase in 2022 with sources such as solar power expected to account for most of this increase. The Russian invasion of Ukraine in February 2022 was expected to help accelerate this upswing.

In 2022, growth in the production of renewable energy sources actually slowed due primarily to factors such as supply chain complications and inflation. Industry projections for 2023 again showed a coming increase in installations of renewable energy production sources; however, this optimism was dampened by the potential for similar complications as existed in 2022. Nonetheless, projections for near-term growth in this part of the energy sector remain encouraging as faster growth is believed possible in 2024.

By 2026 the capacity for electricity generation from renewable energy sources is expected to be eighty percent higher than it was in 2020. One estimate shows this will be 5,022 gigawatts. Wind and solar sources are expected to contribute two-thirds of this growth. This trend is predicted to continue. Sixty percent of global production of electricity is projected to be produced by renewable sources by 2035.