Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics

Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics Volume 1 photovoltaic solar energy 1 04 – history of photovoltaics

1.04 History of Photovoltaics LA Lamont, Petroleum Institute, Abu Dhabi, UAE © 2012 Elsevier Ltd All rights reserved 1.04.1 1.04.2 1.04.3 1.04.4 1.04.5 References Harnessing Solar Energy – A New Invention? What Was the Catalyst for Photovoltaic Development? A Photovoltaic Modern Historical Timeline Current Photovoltaic Technologies Photovoltaics – Where We Are Now? 31 33 37 41 43 44 1.04.1 Harnessing Solar Energy – A New Invention? Many may think that the use of solar energy is a modern time phenomenon being a repercussion of the 1970s’ oil embargo; however, this is not the case The use of solar energy in different forms to support the growth and development of civilization has been around as long as mankind existed When modern society considers energy sources, normally what would come to mind first would be traditional energy sources such as coal, oil, and gas; however, our current biomass of wood, dried animal dung, and peat has traditionally been the choice of fuel of ancient cultures Obviously, the traditional and modern biofuels, as with other renewable energy forms, are all originally created from the sun with the biofuels acting like an early storage device of solar energy which was useful only during daylight hours Early humans did not have the scientific capability and knowledge that we have today, but they had a basic understanding of the power of the sun and they understood that from this ‘bright yellow star’ different forms of energy came to enhance their standard of living This is the reason why many ancient civilizations, such as the Native Americans, both north and south, the Babylonians, the Persians, ancient Hindus, and the Egyptians, had a great respect for the sun, even going to the extent of worshipping it The Greeks, well known for their gods, were devoted to the sun gods Helios and Apollo, and with their traditions built temples to show their devotion This was also seen in the ancient Egyptian Civilization and their dedication to Ra, who was normally depicted with the sun disk of Wadjet placed on top of his falcon head However, it was really the Greeks and Romans who fully embraced the potential of the sun in the first instance as a free energy source [1] The first known invention that captured the solar rays was in 600 BC (before Christ) when fire was initiated by focusing the solar rays onto wood via a magnifying material (Figure 1) This principle was not abandoned but rather it was further used for light applications, specifically torch lighting in the third and second century BC However, as with many innovations, developments in solar energy are often not only used to improve human comfort but also developed and used by the military An ancient example of this was introduced by Archimedes in 212 BC when the Greeks used the magnifying principle of solar radiation to burn the sails on Roman ships that were attacking Syracuse (Figure 2), thus diversifying the potential of solar to include war as well as daily life [3] Very rarely does any civilization move forward with a new idea or technology unless there is a growing need for advancement: Greece experienced a fuel shortage in the fourth century BC, and therefore the need to be innovative and initiate an idea that would provide heat and light for its communities was vitally important for their survival From as early as 400 BC, the Greeks implemented passive solar designs into their accommodations, thus being the first community to fully integrate solar energy into their society for reasons other than religious worship The basic principle of passive solar design (Figure 3) was to protect the north side of the building from the elements (wind, rain, etc.) and ensure that the south was open to solar radiation in the winter but shaded in the summer This simple principle was accepted widely and was implemented not only in private homes but also in public buildings and the world famous Roman bathhouses (Figure 4) This ensured that the civilization captured the optimum amount of energy from the sun; even with a limited understanding of why this worked, the cultures constructed cities based on this principle Greeks and Romans were not the only two societies that embraced this abundant energy source, but also the Pueblo, Anasazi, and Chinese also used the idea for the same purposes of light and heat Although many societies had similar ideas, they were not generated together or the knowledge transferred, rather they were developed separately, as the sharing of knowledge was not as readily available as it is in today’s modern society Societies did however advance their designs and a good example of this was the improvement by the Romans to use glass to enclose the heat in the building, hence storing it and ensuring maximum warmth [1] The Roman Government went further by declaring the first law highlighting that it was illegal to block your neighbor’s sunlight, supporting the embracement of solar heating and lighting at both government and community level The Romans developed and embraced the greenhouse idea we depend on now to grow fruits and vegetables that they brought back from different countries as they were expanding their empire This idea is still used in much the same form today as it was in Roman times to ensure that we have sufficient supplies and varieties of food to feed the world, ensuring self-survival After the turn of history into the anno Domini (AD) period, very little changes or developments occurred with solar energy until during the Industrial Revolution In the different centuries from the beginning of this era, acts by certain people/communities to use Comprehensive Renewable Energy, Volume doi:10.1016/B978-0-08-087872-0.00102-5 31 32 Photovoltaic Solar Energy Figure Creating fire from the sun [2] Figure Archimedes mirror burning Roman military ships [4] Figure Passive solar design in Anasazi cliff [5] the heat and light of the sun were noted but no improvements or breakthroughs were highlighted or noted In 100 AD, Pliny the Younger (Figure 5), who was a lawyer, author, and Roman magistrate, was documented as having a summer house in Italy with what we would consider today a conservatory, but as mentioned before this use of the sun was common in Greek and Roman times so was not a new idea [7] Furthermore, it was recorded that the North American Pueblo people in 1200 AD discovered and embraced the benefits of passive solar By the eighteenth century, it was accepted as normal for the upper classes to have greenhouses, and this was further expanded in the nineteenth century when people with wealth constructed conservatories (Figure 6) for people to relax, walk, and enjoy warmth in very pleasant surroundings However, the next step proved to be the most complicated period with the move from the sun as the provider of light and heat to a supplier of much more The mystery of energy from the sun truly eluded societies until the nineteenth century when one discovery opened many possibilities for the sun to be a future energy-supplying giant History of Photovoltaics 33 Figure Roman bathhouses [6] Figure Pliny the Younger [8] Figure Conservatories first initiated by Romans [9] 1.04.2 What Was the Catalyst for Photovoltaic Development? As discussed previously, for centuries we have been using the power of the sun in a number of basic ways However, it was not until the 1800s that the scientific breakthrough happened to enable us to fully harness all the potential of this free, largely abundant fuel source The credit of this turnaround in the use of solar energy is due to a publication in 1839 by a physicist Edmund Becquerel (Figure 7) from France, who discussed an experiment he had undertaken with a wet cell battery [10] 34 Photovoltaic Solar Energy Figure Edmund Becquerel [11] Light Thin membrane Pt electrodes Acidic Solution Blackened box Figure Photoelectric effect [14] During his investigation, Becquerel discovered that when sunlight is made available to the silver plates, the output voltage of the battery increased (Figure 8) This discovery paved the way for other researches [12, 13]; however, it was not a priority at the time as fossil fuel was reasonably priced and in abundant supply Some other support of this original discovery was undertaken during the 1800s, but progression to prove was slow until the mid-twentieth century Adams (Figure 9) and Day discussed in a publication the effect of sunlight on selenium, and later in 1883, an electrician Charles Edgar Fritts from New York designed a very inefficient (1–2%) prototype cell that is similar to the typical cells used today [15] The efficiency of this and all other cells is calculated by measuring the electricity produced from the total of possible energy that hits the photovoltaic (PV) surface The prototype held many of the characteristics of today’s solar cells – it had a glass cover beneath which was a mass of fine gold wires sandwiched between glass and a thin layer of selenium This was the first model for scientists to improve further, but it would take many decades before an increased efficiency was achieved and a true understanding of the reasons of the earlier low output was reached Little development had occurred over the half century since the initial discovery and whether this was due to lack of knowledge, lack of interest, or the constant low price of fossil fuels is not clear The first half of the twentieth century was to follow much the same trend with the only real notable occurrences being Planck’s (Figure 10) new idea regarding his light quantum hypothesis [17] which supported Albert Einstein’s (Figure 11) 1905 paper [18] on the photoelectric effect that won him the Nobel Prize in 1921 History of Photovoltaics Figure William Grylls Adams [16] Figure 10 Max Planck [19] Figure 11 Albert Einstein [20] 35 36 Photovoltaic Solar Energy Figure 12 Bell Labs scientists Daryl Chaplin, Calvin Fuller, and Gerald Pearson Courtesy of John Perlin Bell Labs silicon solar cell [24] The second half of the twentieth century was to see faster progression, some of which was just natural scientific progression but also some historical occurrences helped to speed up the growth of PV cells Bell Labs researchers in America were responsible for one of the largest discoveries that turned the solar industry into what we see today and unbeknownst to them it was their work in semiconductors that would actually support the development of solar cells [21, 22] Semiconductors are the middle ground between conductors and insulators and are made from silicon that is doped and the researchers at Bell Labs had seen silicon reaching better results than the previously tested selenium [23] They, for the first time, foresaw the possibility for solar cells with efficiencies of more than 20% compared with current levels of 1–2% The team (Figure 12), however, realized that they could not make this significant step with only the transition to a different material and they continued to undertake research to find an optimal p–n junction Bell researchers discovered that they could achieve 6% (US$250 per watt versus approximately $3 per watt for coal) cell efficiency by mixing arsenic with silicon and placing a thin coat of boron on the cell [25] Probably unknown to the scientists they had started a revolution in energy supply that in less than 20 years would be needed worldwide even if their discovery was a spin off from their transistor technology and expertise Even with the advancement, the current product was too expensive for terrestrial use; however, for space power applications, it was the perfect solution as there was no other alternative, so despite its negative points it was still the best solution [16] The first of many solar cells for powering space machines was placed on the Vanguard I space satellite in 1958 and this worked until it was decommissioned in 1964 [26] The huge success of PV cells as an endless and nonpolluting power supply has ensured a place for these cells in the space industry (Figure 13) independent of cost and efficiency [27] As more improvements and developments have been made to cells so has the option of where they can be incorporated As the efficiency continues to improve, the efficiency of PV cells improved to 14% by Hoffman Electronics (1960) [29], so does the Figure 13 Solar-powered space satellite [28] History of Photovoltaics 37 transition between using these cells only in space and a future of installing them in terrestrial applications However, in the early 1970s, there were still limitations with only the powering of systems in remote locations with no grid excess being considered a possibility From a sustainability point of view, it is a shame that such a major source of energy as solar technology took so long to develop and expand due to the continuing popularity of fossil fuels This would probably still have been the situation if the oil crises in 1973 and 1979 with the OPEC oil embargo had not occurred [16, 30] This substantial rise in oil prices and huge shortages of oil specifically in America forced the government to realize that this dependency on foreign fossil fuel was a risky business and highlighted the volatility of the traditional energy market, especially when there was free access to the sun, the most powerful fuel source At this point, more interest was initiated in ‘alternative’ energy through research and development (R&D) as well as government incentives that helped to support the acceptance of renewable energy [31, 32] During the 15-year period from 1970 onward, PV cells saw a huge growth, which culminated in a breakthrough in the price of PV cells per watt to under one-tenth of its previous cost in this short period (1970 – $100 per watt to 1985 – $7 per watt) This could have continued if the oil price had not dropped again, which meant people quickly forgot about the issues of the decade before and went directly back to their old habits, meaning that for another extended period progress was limited and the world went back to embracing fossil fuels Even the government’s support during this period was somewhat focused in the wrong direction as it did not see the importance of supporting the PV companies to develop the systems that would have speeded the progression of solar technology; rather it directed its efforts to universities for large-scale R&D making the public’s access to this technology more difficult Another factor that played an important part in the slow development of this technology was the attitude of the fossil fuel providers which traditionally most communities and governments depend on for energy This industry did not support the development of alternative energy initially providing it with a challenging path; however, this has changed as nowadays most people widely accept the idea of renewable energy as a supporting source to the traditional source The United States very much took the lead in solar cell development after the initial nineteenth century French discovery, and until 1990 they were the leaders in the market, R&D, and implementation Nevertheless, this changed at the end of the twentieth century with this domination moving and splitting between Europe and Japan In this decade, the world reached a huge milestone with one million homes integrating some type of solar power During this period, both Japan and Europe, particularly Germany, introduced government subsidies, increased public awareness, and invested in R&D In the 1990s, Japan had seen its market increasing 10-fold with Germany floundering initially but modifications to its subsidies had seen its output rise by a multiple of 40 even topping Japan’s success Other European countries such as Spain have followed their lead and achieved much the same growth The PV market has completed an exciting part in its history with R&D still ongoing together with product development for tasks such as lighting, desalination, and pumping, and hence making it interesting not only to scientists and engineers but also to the general public (Figures 14 and 15) Solar energy is now not only a more accessible power supply to satisfy the ever-growing demands but it also has lower costs, has higher efficiency, and is a clean alternative to fossil fuels 1.04.3 A Photovoltaic Modern Historical Timeline The previous section discussed the major events that happened to develop solar energy to what it is today; however, many other smaller events played their part in the growth of this technology Table outlines the year of the event, the person/company/ country responsible, if available, together with a summary of the discovery outlining the modern history of PV technology Figure 14 PV on homes [33] 38 Photovoltaic Solar Energy Figure 15 Large-scale PV plants [34] Table Glimpse of the modern PV history Year Person/company/country Summary of discovery 1839 Alexandre Edmond Becquerel 1873 Willoughby Smith 1876 Richard Day, William Adams 1877 1883 1887 William Adams Charles Fritts Heinrich Hertz 1888 1901 1904 Edward Weston Nikola Tesla Wilhelm Hallwachs 1905 Albert Einstein 1914 1916 1918 Goldman and Brodsky Robert Milliken Jan Czochralski 1921 1932 Albert Einstein Many scientists The photoelectric effect (light to electricity conversion) which saw both the conductance and illuminance rise during an experiment he was undertaking with metal electrodes and electrolyte Selenium sensitivity to light was discovered during another experiment he was undertaking promoting branching into selenium solar cell experiments Smith’s discovery of the photoelectric effect on selenium was further verified and advanced by testing it with a platinum intersection which experiences the same phenomenon Constructed an initial solar cell from selenium Explained the selenium wafer solar cell with his version having approximately 1–2% efficiency The effect of ultraviolet light on reducing the minimum value of voltage capable of inducing sparking between a pair of metal electrodes was tested ‘Solar Cell’ obtained first US patent [35] US Patent ‘Method of Utilizing and Apparatus for the Utilization of Radiant Energy’ [36, 37] Further discoveries continued with regard to photosensitive material mixing specifically cuprous oxide and copper Published on the photoelectric effect – ‘On a Heuristic Viewpoint Concerning the Production and Transformation of Light’ [18] PV barrier layer was discovered Proved Albert Einstein’s 1904 photoelectric effect theory Discovered a method to nurture single-crystal silicon, hence supporting the development and future production of solar cells using monocrystalline silicon based material Nobel Prize for 1904 paper on photoelectric effect More material combinations were being observed to react to the photoelectric effect, specifically cadmium selenide Development of the initial monocrystalline solar cell made from silicon was completed Primary solar cells using germanium were built as advancements enabling a p–n junction of a single-crystal cell of this material to be grown Completed research on theoretical solar cell material efficiency and the wavelength of the solar spectrum [38] Published on the photoelectric effect of cadmium sulfide [39] 1941 1951 1953 Dan Trivich 1954 Reynolds, Leiess, Antes, and Marburger AT & T Pearson, Chapin, and Fuller – Bell Laboratory 1954 1954 1954 1955 1955 1955 1955 1957 1957 1958 1958 Mort Prince and team Western Electric Hoffman Electronics – semiconductor division Hoffman Electronics Chapin, Fuller, and Pearson AT & T Hoffman Electronics Solar cell operations were widely exposed to the American public Solar cells produced using silicon with 4.5% efficiency This work was developed from a discovery that researchers made on the photoelectric effect on silicon when conducting another project on semiconductors [23] Bell Labs broke its own efficiency record by 1.5%, raising the new level to 6% in a short time frame Initial research into powering satellites using solar cells commenced Silicon solar cell production commercial license Produced a PV with the following specification per cell: 14 mW peak power with 2% efficiency for US$25 In Chicago, a car powered by solar energy was unveiled Efficiency of PV improved to 8% Patent issued – ‘solar energy converting apparatus’ [40] Efficiency of PV improved to 9% Solar cell was designed to withstand the radiation in space (Continued) History of Photovoltaics Table 39 (Continued) Year Person/company/country Summary of discovery 1958 1958 1958 1959 1959 1960 1961 1961 1962 1962 1963 1963 1964 1965 US Signal Corps USA Russia Hoffman Electronics USA Hoffman Electronics United Nations Defence Studies Institute Bell Labs First space satellite which was PV powered named Vanguard I was designed and operated for years Explorer III and Vanguard II – other solar-powered satellites launched Sputnik III solar-powered satellite launched Efficiency of their PV improved to 10% Explorer VI and VII launched with the previous having 9600 cells Efficiency of their PV improved further to 14% Conference was held on solar energy applications in the developing world First PV specialist conference Telstar telecommunications commercial satellite with 14 W peak power Second PV conference First viable silicon PV module World’s largest 242 W PV array for powering a lighthouse was installed New largest 470 W PV array for powering a space project (Nimbus) was designed Designed the edge-defined film-fed growth (EFG) process Tyco Labs were the first to create crystal sapphire ribbons after the silicon version kW PV power astronomical observatory was launched and went into earthly orbit The idea of a solar power satellite system was announced [41] Another satellite (OVI-13) was launched, but this time with two cadmium selenide panels as power supplies Founding of Spire Corporation, which was a company that aimed to continue to be important in solar cell manufacturing All the historical developments to date and the high interest in research has ensured the constant reduction of PV technology to approximately 80% of the original cost, hence making it more readily available for common low-power applications Used a cadmium selenide PV to power a TV, which was used for educational purposes in Africa (Niger) Company founded Beginning of commercial operation and opening of sales division Two NASA experts with experience in PV satellites founded this company Development of initial domestic PV cells and thermal combined appliances A $30 per watt cell was developed An initiative by the Japanese to further enhance, develop, and research in this area One-inch EFG ribbon using the endless belt process Established Solar Technology International Research and development for earth-based PV systems at this lab was supported by the US Government This occurred from an industrial conference recommendation Established Solar Power Corporation Produces silicon ribbon crystal modules From 1976 to 1985 and also from 1992 to 1995, the NASA Lewis Research Centre (LeRC) worked on integrating PV cells into small power systems that could be used in many areas especially rural places with limited power Amorphous silicon cell was introduced Established Established the National Renewable Energy Lab (NREL) in Colorado initially known as the Solar Energy Research Institute (SERI) This year the sum of all the PV modules produced topped 500 kW Six strategically placed meteorological stations in the United States were introduced for recording data Placed in a Papago Indian community the first PV system which supplied the power requirements for the entire village The system was 3.5 kW and supplied power and pump water for 15 homes Established This company based in California built the largest PV production facility to date Installed a pumping station of 1.8 kW which was then upgraded to 3.6 kW in Burkina Faso 60 kW diesel–PV hybrid system for powering a radar station was installed in Mount Laguna in sun-drenched California MW per year peak power PV module produced New company BP Solar For just more than 10 years they produced 95% of the world’s solar-based electricity However, when the price of fossil fuels reduced, they closed due to lack of investor support 105.6 kW system built by a Utah company The system integrated modules produced by Spectrolab, ARCO Solar, and Motorola An interesting fact is that this system is still operational Sharp Corporation Japan USA Tyco Labs 1966 1968 1968 NASA Peter Glaser 1969 Roger Little 1970 1972 France 1972 1973 1973 1973 1973 1974 1974 1975 1975 Solar Power Corporation Solar Power Corporation Solarex Corporation Delaware University Project Sunshine Tyco Labs Bill Yerkes Jet Propulsion Laboratory 1975 1976 1976 Exxon Kyocera Corp NASA 1976 1976 1977 RCA Lab Solec International US Department of Energy 1977 1977 NASA (LeRC) 1977 NASA (LeRC) 1979 1979 1979 1979 Solenergy ARCO Solar NASA (LeRC) 1980 1980 1980 ARCO BP Luz Co 1980 Wasatch Electric (Continued) 40 Table Photovoltaic Solar Energy (Continued) Year Person/company/country Summary of discovery 1981 NASA LeRC 1981 1981 Solar Challenger USA 1981 1981 1982 1982 1982 Saudi Arabia Helios Technology 1982 1982 1983 1983 Volkswagen Solarex Production 1983 ARCO Solar 1983 1983 Solar Power Corporation NASA LeRC and Solarex 1983 1984 Solaria Corporation David Carlson and Christopher Wronski For years they worked on powering remotely located refrigerators for vaccine which was tested in 30 worldwide locations Maiden voyage of the first solar-powered plane Solar projects 90.4 kW – Square Shopping Centre, Lovington, New Mexico, powered by Solar Power Corporation modules 97.6 kW – Beverly High School, Beverly, Massachusetts, powered by Solar Power Corporation modules 10.8 kW peak power desalination system in Jeddah, Saudi Arabia, powered by Mobil Solar First European PV manufacturer was established Above 9.3 MW PV power produced worldwide MW dual tracking PV plant called Solar’s Hisperia in California was grid connected Unveiled two PV-powered systems for testing a power supply for public lighting and for terrestrial satellite reception stations A system used to start a car by placing 160 W peak power PV on the car roof top was tested Solar rooftop project of peak power 200 kW 21.3 MW peak power produced worldwide kW powered vehicle which participated in the Australia Race driving for 20 days and 4000 km with an average speed of 24 km h−1 and a maximum speed of 72 km h−1 However, later in the same year, the car outperformed itself by traveling further than 4000 km in 18 days on its journey between Long Beach and Daytona Beach MW power plant grid subsystem for Pacific Gas and Electric Company which was enough to supply 2000/2500 homes A Tunisian village was supplied with four systems with a combined power of 124 kW Built a system of 1.8 kW in Guyana to maintain power for basic hospital power requirements such as lighting, radios, and medical refrigerators Other places were also provided with similar systems such as kW in Ecuador and 1.8 kW in Zimbabwe Merged with Amoco Solar, which was owned by Standard Oil They were presented the IEEE Morris N Liebmann Award for their work in “use of amorphous silicon in low cost, high performance photovoltaic solar cells” Sacramento in California has a MW PV power plant Amorphous modules first shown Remote medical and school basic power supplies in Gabon by 17 separate systems Grid-connected 30 kW system in Southampton, UK BP Solar expanded by purchasing Monosolar thin-film division 20% solar cell efficiency obtained The Tour de Sol which ran from 1985 to 1993 based in Switzerland was another race for solar-powered vehicles As the years progressed, different classes opened providing not only direct solar-powered cars the right to participate but also other solar-powered vehicles Unveiled the first thin-film PV Provided a PV system of 50 kW in Pakistan for projects the United Nations was undertaking MW per year thin-film production possible In addition to production in California, the company expanded its production to Germany and Japan Thin-film technology patent Company created out of the amalgamation of Energy Conversion Devices Inc (ECD) and Canon Inc Bought by Siemens and renamed Siemens Solar Industries First country to launch a program that aimed to get community embracement of solar energy – $500 million ‘100 000 solar roofs’ program This program focused not only on homes but any building including churches with the Cathedral in East Germany embracing this initiative Name changed to BP Solar International as well as being a new division in the BP company New location for remote power application Patent of a 20% efficiency silicon cell Japan is the next country to follow Germany’s subsidy lead with its ‘70 000 Solar Roofs’ program Launched its website providing more access to information on renewable energy German company ASE GmbH took over Mobil Solar Energy Corporation creating ASE Americas Inc The two groups along with Siemens Solar collaborated to support renewable energy projects which enhanced system commercialization in India Expanded their business by taking over APS’s California production premises In the same year, they further expanded their product line to include the production of CIS The Icar plane, which was powered by solar cells, had a total surface area of 21 m2 covered by 3000 cells ARCO NASA LeRC Solar Trek 1984 1984 1984 1984 1984 1985 1985 ARCO NASA LeRC BP Solar Systems and EGS BP Solar University of New South Wales Urs Muntwyler 1986 1989 1989 ARCO Solar Solarex ARCO Solar 1989 1990 1990 1990 BP Solar United Solar Systems Corporation ARCO Solar Germany 1991 1992 1992 1994 1994 1994 1995 BP Solar Systems Antarctica 1996 Japan National Renewable Energy Lab ASE Americas Inc World Bank and Indian Renewable Energy Source Agency BP Solar 1996 Icar (Continued) History of Photovoltaics Table 41 (Continued) Year Person/company/country Summary of discovery 1997 General Motors Sunracer vehicle 1998 California 1999 2000 First Solar LLC Japan 2001 2002 2003 NASA and Aero Vironment Inc California Public Utilities Commission Germany 2004 Germany 2004 2004 2005 2006 GE Worldwide California Solar Initiative This vehicle won the race through Australia called the Pentax World Solar Challenge with 71 km h−1 average speed $112 million program called ‘Emerging Renewable Program’ to support residential and commercial PV systems Created through the combination of True North Partners, Solar Cells Inc., and Phoenix LLC During these years the output of Japanese products grew with Kyocera and Sharp, each producing enough peak power for a country like Germany HELIOS, another solar-powered plane, achieved a record height of 30 000 m An incentive program of $100 million for PV systems less than 30 kW was initiated Continued to expand their acceptance of PV systems by building many more projects such as the example at Hemau, which was connected to the grid and considered the largest of its time (4 MW) Solarparks of up to MWp were built in Leipzig, Geiseltalsee, Gottelborn, and other locations due to energy laws from the German Government 60% of PV market is held by BP Solar, Kyocera, Sharp, Shell Solar, and RWE SCHOTT Solar Purchased Astropower, the final American independent PV producer 55 countries have embraced solar energy A three billion dollar 10-year funded solar initiative was announced which commenced the following year with great interest and acceptance GW of PV modules installed $2.8 billion toward incentives 40% efficiency achieved on a PV cell 9.5 GW of PV modules installed Solar panel project initiated 42.8% efficiency achieved 15 MW installation Reached 40.8% efficiency 16 GW of PV modules installed 6.9 GW of PV cells are produced worldwide 20 MWp, which was at the time the world’s largest plant Initiated a requirement for utilities to have at least 33% of renewable energy portfolio 23 GW of PV installed, with annual production of 11 GW Typical commercial efficiency is now 15% Moved production from the United States to China Installed more solar panels for hot water at his home From 2006, worldwide there has been an addition of approximately 16 000 MW of solar power 40 GW of PV capacity Accounts for approximately 80% of the worldwide PV market In years, PV capacity is GW 70% of its PV systems are off-grid Current top five solar PV countries in order are Germany (17.3 GW), Spain (3.8 GW), Japan (3.5 GW), Italy (3.5 GW), and the United States (2.5 GW) Annual production of PV modules is currently at 24 GW, which is a doubling from the previous year The top three countries that added the most solar are Germany, Italy, and Czech Republic PV systems are implemented in more than 100 countries 25% of PV systems are utility-scale PV plants From the top 15 PV-manufacturing companies 10 are located in Asia Purchased more than half the PV modules produced Increased the amount of electricity produced by PV systems by 87% over the previous year 119 countries have embraced solar energy New countries that have utility-scale PV systems include Bulgaria, China, Egypt, India, Mali, Thailand, and United Arab Emirates World’s largest PV manufacturer Produces two-thirds of the PV modules manufactured 2006 2006 2006 2007 2007 2007 2007 2008 2008 2008 2008 2008 2009 2009 2010 2010 2010 2010 2010 2010 2010 2010 Worldwide California Public Utilities Commission Worldwide Google University of Delaware Nellis Solar Power Plant NREL Worldwide Worldwide Siemens California Governor Worldwide BP US President Worldwide Worldwide Europe Czech Republic Australia Worldwide 2010 2010 2010 2010 2010 2010 2011 2011 2011 Worldwide Worldwide Worldwide Worldwide Asia Germany Germany Worldwide Worldwide 2011 2011 Suntech Power Holdings – China China 1.04.4 Current Photovoltaic Technologies In the previous sections, we have discussed the history behind the development of PV technology, where it started, and why it developed quicker during certain periods of history We did not investigate how the technology has branched out with relation to the combination of material used or the production methods selected It is not only important where the technologies are now but rather how they got to this point and what are the historical steps to arrive at today’s technology 42 Photovoltaic Solar Energy The efficiency and cost of the panels have been the two major issues in the development of PV technology, and still are today There is an interlinking generally between the increase in efficiency and the cost, as normally they both rise and fall together For example, the increase in cost due to more expensive materials could lead to identical $/W when the efficiency is increased at the same rate; or scale effects in manufacturing generally lead to cost reductions provided the efficiency remains at least the same However, depending on the commercial use and market development, cost will be a major issue rather than efficiency as every manufacturer is trying to develop the ‘super cell’, which has high efficiency and low cost In reality, a variety of cells and modules in terms of cost and efficiency are needed to provide an optimal solution for varying power system requirements Currently, there are two main areas in R&D: one is in the material being used and the other is in the construction of the cells Let us first consider the latter by showing the effect of the number of junctions in a cell on cell efficiency Figure 16 shows the development of efficiency over three decades; it illustrates how much it has improved from the single-crystal single-junction gallium arsenide cell in 1980 of 22% to today’s three-junction concentrators with 42.5% efficiency [42] Within specific materials, there are advancements trying to further develop them, but sometimes the first prototype model provides the best results as with crystalline silicon cells the first developed single crystal has the highest efficiency of this family even if other attempts of improvements are ongoing (Figure 17) One of the new second-generation technologies that is proving interesting is thin-film technology, and the many material-based variations The development of this technology started in 1976 with cadmium telluride (CdTe) and amorphous silicon (a-Si), with the development of copper indium diselenide or copper indium gallium diselenide (Cu(In,Ga)Se2) starting a year later in 1976 Although CdTe started with the highest efficiency, it was not long before Cu(In,Ga)Se2 caught up and even overtook it with fast development in output efficiency However, a-Si was initially lower than the first thin-film technologies and never managed to catch up or overtake the leaders Over two decades later for about years researchers started to look at nano-, micro-, and poly-Si thin 45 40 35 30 25 20 15 10 1980 1985 1990 1995 2000 2010 2005 Single-junction single-crystal GaAs Thin-film single-crystal GaAs Two-junction concentrators Three-junction concentrators Figure 16 Effect of the number of junctions on efficiency [42] 30 25 20 15 10 1980 1985 Single crystal 1990 Multicrystalline Figure 17 Efficiency development of the silicon family [42] 1995 2000 Thick silicon film 2005 2010 Silicon heterostructures History of Photovoltaics 43 25 20 15 10 1980 1985 1990 1995 2000 2005 2010 Amorphous silicon Cadmium telluride Copper indium diselenide or copper indium gallium deselenide Figure 18 Efficiency development of some thin-film technologies [42] 8.3 2010 2011 5.5 5 2005 2006 2007 3.5 3 2001 2002 2003 2000 2004 2008 2009 Efficiency (%) Figure 19 Efficiency development of organic PV cells [42] films, and in this short period the efficiency grew by 6.7% from its 10% starting point but no further development was made after this point Figure 18 shows how the efficiency of the main thin-film players has changed from the 1980s to today As with every technology that strives to achieve the best, many inventions are tested some of which lead to a fruitful outcome whereas others not The PV market has some interesting emerging technologies that could further change the future of the power output Some such as dye-sensitized cells have been researched since the early 1990s with minimum improvement (7–11%), so it seems that progress has stopped Other developments such as organic cells are twenty-first century cells which are improving slowly but steadily (Figure 19) Probably the two newest technologies being considered are inorganic (10%) and quantum-dot cells (3%) and their future has many possibilities but as with any technology the future will tell the tale of its success or failure 1.04.5 Photovoltaics – Where We Are Now? This chapter has discussed how solar energy has benefited the world for centuries and how after no breakthrough for years one scientific discovery and a lot of issues with the previously predominate fossil fuels enabled the development of PV technology to speed up The earth has moved from a fossil fuel-dependent world to having other options such as PV solar energy The current development of PV technology can basically be divided into three generations [43] The first-generation technology focuses on silicon semiconductor devices, the second on the thin film, and the third is the further development of these two areas of interest The first generation offered a good innovative product with a reasonable future The current single-junction silicon semicon­ ductor is used in about 90% of the cells produced because of its high efficiency at unfortunately high cost which comes from the production costs of energy and labor input To date, first-generation solar cells have nearly reached their previously assumed 44 Photovoltaic Solar Energy efficiency limit of 30%; however as with any technology development is ongoing Currently for this technology the energy payback time is approximately 2–4 years, so it is a reasonable option to consider for installation and, currently even though it is nearly at cost parity with consumer electricity no further improvements can be envisaged The thin-film technology can be referred to as the second-generation technology as its development started later in the 1990s, but opposed to the crystalline silicon semiconductors thin-film solar cells have low cost which is positive but unfortunately along with this they also had low efficiency Nevertheless, as there are recent innovations there are many possible improvements that can be introduced to them Basically, the researchers in thin-film technology took the problems of the previous technology and tried to improve it, so they have concentrated on two areas, namely the material and production The initial step was to look at different materials which address some of the concerns of previous generations with the next step progressing to considering the different manufacturing techniques to lower the production energy required such as electroplating, ultrasonic nozzles, or vapor depositing A good example of this technology and why it might be an acceptable alternative is that the printed cells which have a low efficiency of 12% are fast to produce and have a very low cost, hence if the coverage area is not a limiting factor then they are definitively a good option It is noted that this second generation, such as CdTe, is bypassing the first with regard to cost and in the future possibly may also become lower in cost than fossil fuels The third generation of PV technology is aiming at achieving such things as greater than 60% efficiency in thin-film or other devices, in addition to working on combining the better factors from the previous generations while embracing the low production cost of the second In addition, from ideas now on the table, it is expected that there will be novel results from this R&D in the first quarter of this century [44] Currently, scientists are looking at multijunction devices, the use of nanotechnology, spectral modification, enhanced light management using photonics and plasmonics, and much more, and it will be interesting to see how these develop in the future The currently available PV modules that are produced in 2010 normally cost approximately $1.80 per watt, which is expected to drop to $1.50 per watt in 2011 with the economic payback period of a full system being approximately 8–12 years [45] This payback period is further effected by which country you live in and which, if any, government subsidies are available One of the major positive sides of the PV is its lifetime of 30–35 years with a (manufacturers’) warranty of 25 years, hence leaving the consumer a lot of time to earn money after the initial outlay is paid back One of the main reasons for this extended lifetime is due to the fact that many PV systems not have moving parts, hence they not wear out and there is less maintenance making it a very useful electricity supplier This estimation of lifetime is only a reserved guess as the technology is not old enough to have a guaranteed number; nevertheless, currently, the oldest PV system is still operating after almost half a century, so in the future the time frame might need to be revised [25] One of the main factors to bear in mind is that a PV cell is not what operates practically, as this is only the first step of building a fully operational system The production cost as of 2010 is approximately $1 per watt for a PV cell, which doubles when sold in a module to $2 per watt, and by the time the system is installed and fully commissioned the full cost is $5 per watt It should be noted that the numbers are rapidly changing; for example, as of September 2011, in the Netherlands market, a complete roof-mounted PV system is quoted at a price of Euro per Wp A lot of investigation is needed to improve the cost effectiveness in all areas of the PV system, including cell and module cost, but also inverter and installation In conclusion, it is vitally important that modern society aims to optimize the harnessing of this abundant free source that provides nonpollutant energy and is silent in operation and therefore easier to get the public to accept than other renewable energies Mankind should aim for this to be the primary fuel of the future and not an ‘alternative’ [44] References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] Naff CF (2007) Solar Power, 1st edn Farmington Hills, MI: Thomson Gale http://survival-guy.blogspot.com/2010/09/creating-plan-food-part-4.html Stanley T (2004) Going Solar: Understanding and Using the Warmth in Sunlight, 1st edn Christchurch, New Zealand: Stonefield Publishing Wikipedia 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USA 19 81 19 81 1982 19 82 19 82 Saudi Arabia Helios Technology 19 82 19 82 19 83 19 83 Volkswagen Solarex Production 19 83 ARCO Solar 19 83 19 83 Solar Power Corporation NASA LeRC and Solarex 19 83 19 84 Solaria... Laboratory 19 75 19 76 19 76 Exxon Kyocera Corp NASA 19 76 19 76 19 77 RCA Lab Solec International US Department of Energy 19 77 19 77 NASA (LeRC) 19 77 NASA (LeRC) 19 79 19 79 19 79 19 79 Solenergy ARCO Solar. .. Person/company/country Summary of discovery 19 58 19 58 19 58 19 59 19 59 19 60 19 61 19 61 1962 19 62 19 63 19 63 19 64 19 65 US Signal Corps USA Russia Hoffman Electronics USA Hoffman Electronics United Nations Defence