Keywords

Solar energy; solar cells; solar thermal power generation; global solar capacity; history of solar power

The History of Solar Power

The exploitation of solar thermal energy can be traced back at least 29 centuries to the 7th century BC when the use of magnifying glasses was first recorded. This was followed in the 3rd century BC by the use of mirrors to concentrate the rays of the Sun, using the heat generated to light torches, often for religious ceremonies. The Greek scientist Archimedes is reputed, around 214–212 BC, to have used giant mirrors to focus light on the ships of Roman invaders who were attacking his home city of Syracuse in Sicily, apparently setting the wooden vessels on fire. There is no documented proof, but the experiment was recreated in the 1970s when a wood boat was set alight at 50 m. Meanwhile, throughout the last two millennia, architects and communities have used south-facing buildings to provide winter warmth.

A more systematic examination of solar energy was carried out by the Swiss scientist Horace de Saussure, who in the 18th century developed hot boxes in order to measure the heating effect of the Sun through glass. Hot boxes were later used for cooking.

The first successful attempt to convert solar energy into mechanical power was achieved by the French scientist Auguste Mouchout.¹ Mouchout used a reflector to concentrate the Sun’s energy and generate steam in a glass-enclosed iron cauldron, and was able to use the steam to drive a small steam engine. With the support of the French government he continued to develop his device until 1881. Inspired by Mouchout’s experiments, William Adams, an English civil servant in India, in the late 1870s developed the idea of using an array of flat mirrors arranged in a semi-circle to focus the Sun’s energy on a single spot. This forerunner of the modern solar tower was able to drive a 2.5-horsepower steam engine during daylight hours. Around the same time in the United States, the Swedish-born engineer John Ericsson developed a parabolic trough reflector system.

Commercial exploitation of solar thermal power began with the Solar Motor Co., formed in Boston, United States, in 1900 by Aubrey Eneas. Eneas’ company was not successful, but a company formed by another American entrepreneur, Frank Shuman, built the world’s first successful solar-powered plant. Using parabolic troughs designed to track the Sun across the sky, the Sun Power Co. built a pumping station just outside Cairo, Egypt, that was able to generate 55 horsepower at a cost of $150/horsepower. The plant was completed in 1912 and appeared to be a success. Unfortunately the outbreak of World War I led to the destruction of the solar pumping station and the technology was not revived after the Armistice in 1918. However, in the 1960s parabolic reflectors were used in Italy to generate electric power, and commercial solar thermal power became a reality at the end of the 20th century.

The second means of generating electricity from the Sun, the solar cell, was born from the work of the French scientist Edmond Becquerel, who discovered the photoelectric effect. Becquerel observed that when light was shone onto the electrodes of a simple electrochemical cell made from two metal electrodes immersed in an electrolyte, the amount of electricity from the cell increased. This was followed in 1783 by the publication of a scientific paper in which an English electrical engineer, Willoughby Smith, revealed his observations that the electrical conductivity of the semiconducting material selenium increased when exposed to light. This was followed by further work on selenium by William Adams and Richard Day who, in 1876, discovered that illuminating a junction between selenium and platinum produced an electric current. This led to the production of the first solar cell made from selenium by the American inventor Charles Fritts. The conversion efficiency was around 1% and costs were too high for a practical device.

There was more work on the photovoltaic effect and on semiconductors during the next 60 years, including pioneering theoretical work by Einstein, but it was not until the early 1950s that true photovoltaic technology was born. This was the result of research by Daryl Chapin, Calvin Fuller, and Gerald Pearson at Bell Labs in the United States. The team produced a silicon photovoltaic cell with an efficiency of 4%, and later increased this to 11%.

Commercialization of solar cells was slow to take off, but in 1958 they were used to provide power to early satellites such as the U.S. Vanguard 1 and the Russian Sputnik-3. The technology remains the main source of electric power in space. Development continued throughout the next six decades, with new materials and higher efficiencies leading to cost-effective commercial solar cells for both central power and domestic rooftop applications; these became available by the middle of the second decade of the 21st century.

Global Solar Power Generating Capacity

Records of solar cell capacity from the early years of their deployment are patchy, but the total global capacity appears to have been around 100 MW or less in 1990. In 1993 the installed capacity in IEA countries was 113 MW according to the IEA. Global capacity began to rise more rapidly during the 1990s, and by 2000 the total global capacity was 1288 MW, as shown in Table 1.1, while the global annual capacity addition was just over 200 MW.

The figures in Table 1.1 show both the aggregate annual capacity of solar cells and the annual capacity additions. The latter reflect the overall global manufacturing capacity. Total global aggregate capacity reached 5112 MW in 2005 and 40,336 MW in 2010, when over 17,000 MW of capacity was added during the year. Since then, annual capacity additions have been 30,000 MW or more, so that by the end of 2014 the total global installed capacity was estimated to be 178,391 MW. Market predictions put the capacity at the end of the second decade of the 21st century at between 400 and 600 GW.

While the use of solar cells is now widespread, the early growth in solar cell deployment was driven by national programs that provided incentives for rooftop installation of solar panels. The most notable of these were in Japan, Germany, and the U.S. state of California. Deployment in Germany spread to other European countries during the first decade of the 21st century, with a large rollout of cells in Spain, and then in Italy and France. All these contributions have led to Europe having the largest regional installed capacity of solar cells, 81,488 MW at the end of 2013, as shown in Table 1.2. However, in 2014 Europe only installed around 7 GW of new capacity, lower than the United States, Japan, or China. Of this, 2400 MW were installed in the United Kingdom and 1900 MW in Germany.³

The Asia Pacific region, including Japan, had the second largest regional installed capacity at the end of 2013 with 21,992 MW, while China had a further 18,600 MW. During 2014, China added 10,600 MW, pushing its total capacity to 29,200 MW. Meanwhile, an additional 9700 MW installation in Japan pushed the total in the Asia Pacific region to over 30,000 MW.

Total installed capacity in all the Americas at the end of 2013 was 13,327 MW. In 2014 6500 MW were installed in the United States, pushing the total across the Americas to above 20,000 MW. The lowest regional capacities at the end of 2013 were in the Middle East and Africa, with a combined aggregate of 953 MW. However, this increased substantially in 2014 when South Africa alone installed 800 MW. The solar photovoltaic capacity in the rest of the world at the end of 2013 was 2098 MW.

Table 1.3 contains figures for the installed solar thermal generating capacity in various regions of the world at the end of 2013, based on figures from the IEA. The total amount at the end of that year, 3500 MW, is much smaller than the solar photovoltaic capacity, reflecting the much slower market growth of this technology. Of this amount, around 1300 MW are fitted with some form of thermal energy storage. However, plants with energy storage are expected to become much more common by the end of the second decade of the 21st century.

The largest regional solar thermal capacity at the end of 2013 was based in Europe, virtually all of it in Spain. However, development there has slowed significantly. The capacity in the Americas at the end of 2013 was 900 MW, mainly concentrated in the United States. Here a further 600 MW were added in early 2014, pushing aggregate capacity to 1500 MW. Capacity elsewhere is limited, with 100 MW in each of Asia and Oceania, the Middle East, and Africa. The IEA has predicted that cumulative capacity may reach 11,000 MW by 2020.

Total electricity production from solar power plants between 2002 and 2012 is shown in Table 1.4, based on data from the Fifteenth Inventory published by Observ’ER in 2013. The figures show that total solar production increased from 1.7 TWh in 2002 to 104.5 TWh in 2012. Most of this growth is accounted for by production from solar cells, which was responsible for 100.4 TWh of production in 2012. The contribution from solar thermal plants was 4.1 TWh. Global solar capacity nearly doubled between 2012 and 2015, and it is likely electricity production has nearly doubled too.