Solar energy

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Solar energy involves collecting the radiant heat of the sun to convert into heat or electricity. The two main types of solar energy production are photovoltaic (PV) solar and concentrating solar power. PV solar uses panels containing cells that absorb photons from sunlight. This creates a field of electricity across the panel. Concentrating solar power (CSP) is used on a larger scale in industrial facilities. CSP involves the use of mirrors to reflect and concentrate sunlight onto tubes containing liquid. These tubes collect sunlight, and the heated liquid warms and transforms water into steam to generate electricity.

Background

Photovoltaic (PV) solar technology was created in 1954 when Bell Telephone Laboratories developed a silicon PV cell capable of converting sunlight into power for electrical equipment. In 1955, Western Electric began selling commercial licenses of silicon PV technology. In 1986, Kramer Junction, California, commissioned a concentrating solar power facility (also known as solar thermal). The facility contained mirrors used to concentrate sunlight onto a system of tubes (also known as receivers). This heated energy was used to produce steam to power a conventional turbine to generate electricity.

Types of solar power

The two main types of solar energy production are photovoltaic (PV) solar and concentrating solar power.

A single PV device is called a cell, which is a device made up of semiconductor materials. A cell can produce approximately 1 or 2 watts of electricity. Cells are often placed between glass and/or plastic so the cells can withstand outdoor conditions. On a solar panel, multiple PV cells are connected to increase the electrical output of the cells. The panel is then connected to the electric grid. PV systems can also have structures that allow panels to be pointed toward the sun.

Concentrating solar energy (also known as solar thermal) uses mirrors to reflect and concentrate sunlight onto a system of tubes, also known as receivers. The receivers contain fluid that is heated by the reflected sunlight. The fluid is used to boil water in a conventional turbine to generate electricity. Concentrating solar power is used generally at larger facilities rather than residential or smaller commercial buildings.

Industry

According to the U.S. Energy Information Administration (EIA), the U.S. photovoltaic industry as of 2015 included 53 companies with the equivalent of 6,937 full-time employees. As of March 2017, the EIA did not have data on the companies and employees associated with the concentrating solar energy industry.

Use in electricity generation

According to the U.S. Energy Information Administration, photovoltaic solar and utility-scale solar power (including concentrating solar power) accounted for 5.6 million kilowatt hours of electricity in 2016. In total, the United States produced 4.07 billion kilowatts of electricity in 2016 of which solar energy accounted for 1.3 percent.

The table below shows net generation of electricity from renewable sources, including solar photovoltaic and solar thermal, from 2005 to 2015.

Net generation from renewable sources, 2005-2015
Year	Wind	Solar photovoltaic	Solar thermal	Wood and wood-derived fuel	Landfill gas	Biogenic solid waste	Other biomass	Geothermal	Conventional hydroelectric	Total*
2005	17,811	16	535	38,856	5,142	8,330	1,948	14,692	270,321	357,651
2006	26,589	15	493	38,762	5,677	8,478	1,944	14,568	289,246	385,772
2007	34,450	16	596	39,014	6,158	8,304	2,063	14,637	247,510	352,747
2008	55,363	76	788	37,300	7,156	8,097	2,481	14,840	254,831	380,932
2009	73,886	157	735	36,050	7,924	8,058	2,461	15,009	273,445	417,724
2010	94,652	423	789	37,172	8,377	7,927	2,613	15,219	260,203	427,376
2011	120,177	1,012	806	37,449	9,044	7,354	2,824	15,316	319,355	513,336
2012	140,822	3,451	876	37,799	9,803	7,320	2,700	15,562	276,240	494,573
2013	167,840	8,121	915	40,028	10,658	7,186	2,986	15,775	268,565	522,073
2014	181,655	15,250	2,441	42,340	11,220	7,228	3,202	15,877	259,367	538,579
2015	190,719	21,666	3,227	41,929	11,291	7,211	3,201	15,918	249,080	544,241
*Total refers to all utility-scale renewable electricity generation. Source: U.S. Energy Information Administration, "Table 3.1.B. Net Generation from Renewable Sources: Total (All Sectors), 2005 - 2015"

Environmental impact

Solar energy generally does not produce air pollutants or water pollution, though utility-scale solar facilities may produce limited amounts of traditional air pollutants, such as sulfur dioxide, nitrogen oxides, and volatile organic compounds. In addition, solar energy is considered a renewable energy resource in that it does not rely on a finite source of energy, such as coal, oil, or natural gas, to generate heat or electricity.

Additionally, solar energy produces few to no carbon dioxide (CO₂) or other greenhouse gas emissions. Proponents of solar energy argue that greater use of solar energy could reduce CO₂ emissions that may be linked to human-caused climate change and global warming. The Solar Energy Industries Association, a solar energy advocacy group, contends that greater use of solar would help mitigate climate change, arguing, "While there may be not be one technology that can reduce all U.S. ghg [greenhouse gas] emissions to zero, solar technologies come close. Solar energy is a solution to climate change and can significantly reduce emissions in each of these sectors."

According to the Union of Concerned Scientists, a nonprofit organization that supports increased use of renewable energy, some potentially negative environmental impacts associated with solar energy can include habitat loss or increased water use. The group argues, "Depending on their location, larger utility-scale solar facilities can raise concerns about land degradation and habitat loss." Additionally, the group contended that larger solar thermal plants may require large amounts of water that may strain the use of water resources for other purposes, arguing, "CSP plants that use wet-recirculating technology with cooling towers withdraw between 600 and 650 gallons of water per megawatt-hour of electricity produced."

Economic impact

Proponents of solar energy argue that solar has become more economically viable for consumers and helps create jobs and income. In an article published in September 2015 by Sunworks, Inc., a solar energy provider, the company argued that the average U.S. household can reduce their electricity payments by using solar energy and see an average savings of between $20,000 to $60,000 over two decades. Solar Energy Industries Association, a solar energy advocacy group, argued that solar power accounted for approximately 250,000 jobs in 2016. Additionally, the association argued that the Solar Investment Tax Credit, passed in 2006, allowed for growth and stability in the solar industry.

According to SunRun, a residential solar provider, the total cost of installing solar technology in a home ranges from $15,000 to $29,000 for systems with a size from 4 kilowatts to 8 kilowatts. SunRun broke down the total cost of its solar energy products for residential customers: 47 percent of costs go toward solar equipment (such as solar panels and hardware), 35 percent of costs go toward installation and permits, and 18 percent went toward maintenance costs and repairs. Additionally, the company directed potential consumers to federal, state, and local incentive programs that could reduce the costs of solar energy.

According to the Institute for Energy Research, a nonprofit research group that supports free market energy policies, solar energy remains costly despite government policies to promote its use, according to an October 2016 study. The study's authors argued that policies such as the Solar Investment Tax Credit and Renewable Portfolio Standards at the state level have shifted costs to taxpayers and electric utility ratepayers to the benefit of solar energy companies, contending, "Current solar subsidies and net metering schemes through U.S. states continue to draw capital away from its most efficient use, often at the benefit of U.S. solar panel producers and installation companies, such as SolarCity, but at the expense of electricity consumers."

See also

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  Ethanol

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  Hydroelectric power

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  Wind energy

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  Glossary of energy terms