Solar power
Charles Fritts installed the world's first rooftop photovoltaic solar array on a New York City roof in 1884. This early device used selenium cells that converted just 1% of incident light into electricity. The German industrialist Ernst Werner von Siemens recognized the importance of this discovery shortly after its creation. By 1931, Bruno Lange developed a photo cell using silver selenide instead of copper oxide. These prototype selenium cells still managed to convert less than 1% of incoming light into usable power. Scientists Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954 at Bell Labs. These early solar cells cost US$286 per watt and reached efficiencies between 4.5% and 6%. Mohamed M. Atalla developed the process of silicon surface passivation by thermal oxidation at Bell Labs in 1957. This surface passivation process has since been critical to improving solar cell efficiency.
Over 90% of the current market relies on crystalline silicon technology for generating electricity from sunlight. Photovoltaic systems produce direct current which fluctuates with the intensity of the sun. Inverters convert this direct current into alternating current for practical use in homes and businesses. Multiple solar cells connect inside panels and wire together to form arrays. Thin-film solar cells represent a second generation approach that deposits one or more thin layers on substrates like glass or plastic. Commercial thin-film technologies include cadmium telluride and copper indium gallium diselenide. Amorphous thin-film silicon also serves as a commercially used option today. Concentrated solar power systems use lenses or mirrors to focus sunlight onto extreme heat points. These concentrated rays drive steam turbines to generate electricity rather than using photovoltaic effects directly. The levelized cost of electricity from CSP remains over twice that of standard PV systems as of 2022. Less than 1% of total global solar power comes from these concentrated solar power installations.
China holds about half of the world's installed solar power capacity as of recent years. Almost half the solar power installed in 2022 was mounted on rooftops across various regions. Chinese manufacturers grew to become the largest producers of solar equipment globally. Utility-scale solar became the least expensive energy source in many countries despite rising material costs during the 2021-2022 global energy crisis. Residential solar costs reached approximately 2.50 dollars per watt in the US by 2025. Utility solar costs dropped to around 25 US cents per watt in the same period. Beginning in 1982, the cost per kilowatt was approximately 27,000 American dollars. By 2006 this figure had fallen to roughly 4,000 American dollars per kilowatt. In 1992 a typical system cost about 16,000 American dollars per kilowatt before dropping to 6,000 dollars by 2008. The cost of utility-scale solar PV fell by 85% between 2010 and 2020 while CSP costs only decreased by 68%. Global solar generation capacity exceeded one terawatt for the first time in 2022.
Solar power remains intermittent due to day-night cycles and variable weather conditions throughout the year. Concentrated solar power plants may use thermal storage with high-temperature molten salts to store energy effectively. These salts offer low-cost storage with high specific heat capacity compatible with conventional power systems. Lithium-ion batteries have potential to replace lead-acid batteries in home photovoltaic systems soon. Tesla Gigafactory 1 provides large production facilities expected to lower prices through economies of scale. Retired electric vehicle batteries can be repurposed for distributed photovoltaic systems as well. Sodium-sulfur and vanadium redox batteries serve as other rechargeable options for grid storage. Hydroelectric dams work very well in conjunction with solar power by holding back or releasing water from reservoirs. Pumped-storage hydroelectricity uses solar power to pump water to a high reservoir on sunny days. Electricity prices may become negative in Australia during midday when solar generation is exceptionally high. This phenomenon incentivizes new battery storage solutions across the region.
The life-cycle greenhouse-gas emissions of solar farms stay below 50 grams per kilowatt-hour without battery storage. With battery storage included these figures could rise up to 150 grams per kilowatt-hour. A combined cycle gas-fired power plant emits around 500 grams per kilowatt-hour without carbon capture measures. Coal-fired plants produce about 1,000 grams per kilowatt-hour under similar conditions. Solar panels increase local temperature significantly in large desert installations compared to urban heat islands. Obtaining 25% to 80% of electricity from solar farms by 2050 would require covering land ranging from 0.5% to 2.8% of the European Union territory. Some countries like South Korea and Japan use land for agriculture underneath photovoltaic arrays. Floating solar farms place canopies over parking lots or bodies of water to save ground space. Harmful materials used in panel production generally occur in small amounts though lead remains a concern with perovskite technology. Recycling helps manage waste as second-hand panels sometimes get reused in developing nations like Africa.
Over 40% of global polysilicon manufacturing capacity sits within Xinjiang province in China. This concentration raises concerns about human rights violations linked to internment camps in that region. The International Solar Energy Society estimates solar manufacturing cannot grow beyond 400 billion US dollars annually. Businesses may lobby governments for or against tariffs on imported solar panels depending on their interests. Fossil fuel subsidies remain political obstacles impeding the transition away from traditional energy sources. Solar generation cannot be cut off by geopolitics once installed unlike oil and gas supplies. Far right parties vary by country with some opposing utility-scale solar as part of climate change denial strategies. Acceptance of wind and solar facilities tends to be stronger among U.S. Democrats compared to Republicans who favor nuclear power plants. Green parties often support solar as part of broader climate mitigation efforts despite environmentalists opposing new power lines. Government subsidies have slowed growth of solar generation capacity in many regions globally.
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Common questions
When did Charles Fritts install the world's first rooftop photovoltaic solar array?
Charles Fritts installed the world's first rooftop photovoltaic solar array on a New York City roof in 1884. This early device used selenium cells that converted just 1% of incident light into electricity.
Who created the silicon solar cell at Bell Labs and when was it developed?
Scientists Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954 at Bell Labs. These early solar cells cost US$286 per watt and reached efficiencies between 4.5% and 6%.
What percentage of global polysilicon manufacturing capacity is located in Xinjiang province China?
Over 40% of global polysilicon manufacturing capacity sits within Xinjiang province in China. This concentration raises concerns about human rights violations linked to internment camps in that region.
How much land would be required to obtain 25% to 80% of electricity from solar farms by 2050 in the European Union?
Obtaining 25% to 80% of electricity from solar farms by 2050 would require covering land ranging from 0.5% to 2.8% of the European Union territory. Some countries like South Korea and Japan use land for agriculture underneath photovoltaic arrays.
When did global solar generation capacity exceed one terawatt for the first time?
Global solar generation capacity exceeded one terawatt for the first time in 2022. Over 90% of the current market relies on crystalline silicon technology for generating electricity from sunlight.