power.
Solar energy Solar power produced around 1.3 terrawatt-hours (TWh) worldwide in 2022, Solar energy can be harnessed anywhere that receives sunlight; however, the amount of solar energy that can be harnessed for electricity generation is influenced by
weather conditions, geographic location and time of day. There are two mainstream ways of harnessing solar energy:
solar thermal, which converts solar energy into heat; and
photovoltaics (PV), which converts it into electricity. It is also growing at a much faster rate, with 170 GW newly installed capacity in 2021, compared to 25 GW of solar thermal. From 2020 to 2022, solar technology investments almost doubled from USD 162 billion to USD 308 billion, driven by the sector's increasing maturity and cost reductions, particularly in solar photovoltaic (PV), which accounted for 90% of total investments. China and the United States were the main recipients, collectively making up about half of all solar investments since 2013. Despite reductions in Japan and India due to policy changes and
COVID-19, growth in China, the United States, and a significant increase from Vietnam's feed-in tariff program offset these declines. Globally, the solar sector added 714 gigawatts (GW) of solar PV and
concentrated solar power (CSP) capacity between 2013 and 2021, with a notable rise in large-scale solar heating installations in 2021, especially in China, Europe, Turkey, and Mexico.
Photovoltaics –stating that solar module prices have dropped about 20% for each doubling of installed capacity—defines the "
learning rate" of
solar photovoltaics. A
photovoltaic system, consisting of
solar cells assembled into
panels, converts light into electrical
direct current via the
photoelectric effect. PV systems range from small, residential and commercial
rooftop or
building integrated installations, to large utility-scale
photovoltaic power station. A household's solar panels can either be used for just that household or, if connected to an electrical grid, can be aggregated with millions of others. The first utility-scale solar power plant was built in 1982 in
Hesperia, California by
ARCO. The plant was not profitable and was sold eight years later. However, over the following decades, PV cells became significantly more efficient and cheaper. As a result, PV adoption has grown exponentially since 2010. Global capacity increased from 230 GW at the end of 2015 to 890 GW in 2021. PV grew fastest in China between 2016 and 2021, adding 560 GW, more than all advanced economies combined.
Solar panels are recycled to reduce
electronic waste and create a source for materials that would otherwise need to be mined, but such business is still small and work is ongoing to improve and scale-up the process.
Solar thermal Unlike photovoltaic cells that convert sunlight directly into electricity,
solar thermal systems convert it into heat. They use mirrors or lenses to concentrate sunlight onto a receiver, which in turn heats a water reservoir. The heated water can then be used in homes. The advantage of solar thermal is that the heated water can be stored until it is needed, eliminating the need for a separate energy storage system. Solar thermal power can also be converted to electricity by using the steam generated from the heated water to drive a
turbine connected to a generator. However, because generating electricity this way is much more expensive than photovoltaic power plants, there are very few in use today.
Floatovoltaics Floatovoltiacs, or floating solar panels, are solar panels floating on bodies of water. There are both positive and negative points to this. Some positive points are increased efficiency and price decrease of water space compared to land space. A negative point is that making floating solar panels could be more expensive.
Agrivoltaics Agrivoltaics is where there is simultaneous use of land for energy production and agriculture. There are again both positive and negative points. A positive viewpoint is there is a better use of land, which leads to lower land costs. A negative viewpoint is it the plants grown underneath would have to be plants that can grow well under shade, such as
Polka Dot Plant,
Pineapple Sage, and
Begonia. Agrivoltaics not only optimizes land use and reduces costs by enabling dual revenue streams from both energy production and agriculture, but it can also help moderate temperatures beneath the panels, potentially reducing water loss and improving
microclimates for crop growth. However, careful design and crop selection are crucial, as the shading effect may limit the types of plants that can thrive, necessitating the use of shade-tolerant species and innovative management practices.
Wind power ,
NW-England in Minnesota, United States Humans have harnessed wind energy since at least 3500 BC. Until the 20th century, it was primarily used to power ships, windmills and water pumps. Today, the vast majority of wind power is used to generate electricity using wind turbines. Areas where winds are stronger and more constant, such as
offshore and high-altitude sites, are preferred locations for wind farms. Wind-generated electricity met nearly 4% of global electricity demand in 2015, with nearly 63 GW of new wind power capacity installed. Wind energy was the leading source of new capacity in Europe, the US and Canada, and the second largest in China. In Denmark, wind energy met more than 40% of its electricity demand while Ireland, Portugal and
Spain each met nearly 20%. Globally, the long-term technical potential of wind energy is believed to be five times total current global energy production, or 40 times current electricity demand, assuming all practical barriers needed were overcome. This would require wind turbines to be installed over large areas, particularly in areas of higher wind resources, such as offshore, and likely also industrial use of new types of
VAWT turbines in addition to the horizontal axis units currently in use. As offshore wind speeds average ~90% greater than that of land, offshore resources can contribute substantially more energy than land-stationed turbines. Investments in wind technologies reached USD 161 billion in 2020, with onshore wind dominating at 80% of total investments from 2013 to 2022. Offshore wind investments nearly doubled to USD 41 billion between 2019 and 2020, primarily due to policy incentives in China and expansion in Europe. Global wind capacity increased by 557 GW between 2013 and 2021, with capacity additions increasing by an average of 19% each year. There are many forms of water energy: • Historically, hydroelectric power came from constructing large hydroelectric dams and reservoirs, which are still popular in
developing countries. The
largest of them are the
Three Gorges Dam (2003) in
China and the
Itaipu Dam (1984) built by Brazil and Paraguay. •
Small hydro systems are hydroelectric power installations that typically produce up to of power. They are often used on small rivers or as a low-impact development on larger rivers. China is the largest producer of hydroelectricity in the world and has more than 45,000 small hydro installations. •
Run-of-the-river hydroelectricity plants derive energy from rivers without the creation of a large
reservoir. The water is typically conveyed along the side of the river valley (using channels, pipes or tunnels) until it is high above the valley floor, whereupon it can be allowed to fall through a penstock to drive a turbine. A run-of-river plant may still produce a large amount of electricity, such as the
Chief Joseph Dam on the
Columbia River in the United States. However many run-of-the-river hydro power plants are
micro hydro or
pico hydro plants. Much hydropower is flexible, thus complementing wind and solar, as it not intermittent. In 2021, the world renewable hydropower capacity was 1,360 GW. New hydropower projects face opposition from local communities due to their large impact, including relocation of communities and flooding of wildlife habitats and farming land. High cost and lead times from permission process, including environmental and risk assessments, with lack of environmental and social acceptance are therefore the primary challenges for new developments. It is popular to repower old dams thereby increasing their efficiency and capacity as well as quicker responsiveness on the grid. Where circumstances permit existing dams such as the
Russell Dam built in 1985 may be updated with "pump back" facilities for
pumped-storage which is useful for peak loads or to support intermittent wind and solar power. Because
dispatchable power is more valuable than VRE countries with large hydroelectric developments such as Canada and Norway are spending billions to expand their grids to trade with neighboring countries having limited hydro.
Bioenergy Biomass is biological material derived from living, or recently living organisms. Most commonly, it refers to plants or plant-derived materials. As an energy source, biomass can either be used directly via
combustion to produce heat, or converted to a more energy-dense
biofuel like ethanol. Wood is the most significant biomass energy source as of 2012 and is usually sourced from a trees cleared for
silvicultural reasons or
fire prevention. Municipal wood waste – for instance, construction materials or sawdust – is also often burned for energy. The biggest per-capita producers of wood-based bioenergy are heavily forested countries like Finland, Sweden, Estonia, Austria, and Denmark. Bioenergy can be environmentally destructive if old-growth forests are cleared to make way for crop production. In particular, demand for palm oil to produce biodiesel has contributed to the deforestation of tropical rainforests in Brazil and Indonesia. Some
biomass sources are unsustainable at current rates of exploitation (as of 2017).
Biofuel using wood to supply 30,000 households in France
Biofuels are primarily used in transportation, providing 3.5% of the world's transport energy demand in 2022, up from 2.7% in 2010.
Biojet is expected to be important for short-term reduction of carbon dioxide emissions from long-haul flights. Aside from wood, the major sources of bioenergy are
bioethanol and
biodiesel. Most of the crops used to produce bioethanol and biodiesel are grown specifically for this purpose, although used
cooking oil accounted for 14% of the oil used to produce biodiesel as of 2015. In the European Union, where biodiesel is more common than bioethanol,
rapeseed oil and
palm oil are the main feedstocks. China, although it produces comparatively much less biofuel, uses mostly corn and wheat. In many countries, biofuels are either subsidized or mandated to be
included in fuel mixtures. to produce
ethanol in Brazil There are many other sources of bioenergy that are more niche, or not yet viable at large scales. For instance, bioethanol could be
produced from the cellulosic parts of crops, rather than only the seed as is common today.
Sweet sorghum may be a promising alternative source of bioethanol, due to its tolerance of a wide range of climates.
Cow dung can be converted into methane. There is also a great deal of research involving
algal fuel, which is attractive because algae is a non-food resource, grows around 20 times faster than most food crops, and can be grown almost anywhere.
Geothermal energy in Iceland , California, US , a
geothermal power station in Iceland Geothermal energy is
thermal energy (heat) extracted from the
Earth's crust. It originates from several different
sources, of which the most significant is slow
radioactive decay of minerals contained in the
Earth's interior, Some of the heat is generated near the Earth's surface in the crust, but some also flows from deep within the Earth from the
mantle and
core. As of 2023, the United States has by far the most geothermal capacity (2.7 GW, or less than 0.2% of the country's total energy capacity), followed by Indonesia and the Philippines. Global capacity in 2022 was 15 GW. At smaller scales, geothermal power can be generated with
geothermal heat pumps, which can extract heat from ground temperatures of under , allowing them to be used at relatively shallow depths of a few meters. Technical advances may eventually make geothermal power more widely available. For example,
enhanced geothermal systems involve drilling around into the Earth, breaking apart hot rocks and extracting the heat using water. In theory, this type of geothermal energy extraction could be done anywhere on Earth. == Emerging technologies ==