Photovoltaic History - Key Milestones in the 1900s (Timeline)

Bell Labs engineer testing solar battery in 1954 Credit: Bell Labs website

1904 - Albert Einstein published his paper on the photoelectric effect (along with a paper on his theory of relativity). Wilhelm Hallwachs makes a semiconductor-junction solar cell (copper and copper oxide).

1914 - The existence of a barrier layer in photovoltaic devices was noted.

1916 - Robert Millikan provided experimental proof of the photoelectric effect.

1918 - Polish scientist Jan Czochralski developed a way to grow single-crystal

silicon. 

1921 - Albert Einstein received the Nobel Prize for his theories explaining the photoelectric effect.

1932 - Audobert and Stora discover the photovoltaic effect in Cadmium selenide (CdSe), a photovoltaic material still used today.

1954 - Bell Labs announces the invention of the first modern silicon solar cell. The scientists Gerald Pearson, Daryl Chapin, and Calvin Fuller develop the silicon photovoltaic (PV) cell at Bell Labs—the first solar cell capable of converting enough of the sun’s energy into power to run everyday electrical equipment. Bell Telephone Laboratories produced a silicon solar cell with 4% efficiency and later achieved 11% efficiency. Reporting the Bell discovery, The New York Times praised it as "the beginning of a new era, leading eventually to the realization of harnessing the almost limitless energy of the sun for the uses of civilization".

1959 - Hoffman Electronics creates a 10% efficient commercial solar cell, and introduces the use of a grid contact, reducing the cell's resistance.

1962 - Bell Telephone Laboratories launches the first telecommunications satellite, the Telstar (initial power 14 watts).

1963 - Sharp Corporation succeeds in producing practical silicon PV modules. Japan installed a 242-W PV array on a lighthouse, the world's largest array at that time.

1965 - Peter Glaser conceives the idea of the satellite solar power station. 

1973 - The University of Delaware builds “Solar One,” one of the world’s first photovoltaic PV) powered residences. The system is a PV/thermal hybrid. 

1980 - At the University of Delaware, the first thin-film solar cell exceeds 10% efficiency using copper sulfide/cadmium sulfide.

1982 - The first, photovoltaic megawatt-scale power station goes on-line in Hisperia, California. It has a 1-megawatt capacity system, developed by ARCO Solar, with modules on 108 dual-axis trackers.

1983 - ARCO Solar dedicates a 6-megawatt photovoltaic substation in central

California. The 120-acre, unmanned facility supplies the Pacific Gas & Electric Company’s utility grid with enough power for 2,000-2,500 homes.

1985 - 20% efficient silicon cell are created by the Centre for Photovoltaic Engineering at the University of New South Wales.

1993 - Pacific Gas & Electric completes installation of the first grid-supported photovoltaic system in Kerman, California. The 500-kilowatt system was the first “distributed power” effort.

1998 - Subhendu Guha, a noted scientist for his pioneering work in amorphous silicon, led the invention of flexible solar shingles, a roofing material and state-of-the-art technology for converting sunlight to electricity.

1999 - Total worldwide installed photovoltaic power reached 1000 megawatts.

Photovoltaic (PV) History - the Beginning

The effect of light on the electric properties of certain materials was observed way back even before electricity became generally available.

In 1839 the nineteen-year-old French physicist Alexandre Edmond Becquerel observed the photovoltaic effect for the first time. Experimenting with metal electrodes in a weak electrolyte or conducting solution (such as salt water) exposed to sunlight, he discovered the appearance of small amounts of electric current.

However, Becquerel's discovery couldn't find any practical use and was limited being tagged as an observed phenomenon. The photo conductivity of an element, selenium, was noted by the English electrical engineer Willoughby Smith in 1873 while he was working with Selenium.

In 1876 William Grylls Adams* and his student Richard Day, discovered that illuminating a junction between selenium and platinum can have a photovoltaic effect. This effect is the basis for the modern solar cell. An electricity expert, Werner von Siemens, stated that the discovery was "scientifically of the most far-reaching importance". The selenium cells were not efficient, but it was proved that light, without heat or moving parts, could be converted into electricity.

William G. Adams published also a paper on the selenium cell 'The action of light on selenium,' in "Proceedings of the Royal Society, A25, 113.

In 1883 Charles Fritts, an American inventor, built what many regard as the first true photovoltaic cell. He developed from selenium wafers a solar cell that had less than 1-2% a conversion rate but represents the beginning of solar technology as we know it today.

In 1887 Heinrich Hertz noticed the photoelectric effect, and published his paper entitled “On an Effect of Ultraviolet Light upon the Electric Discharge.” He noticed that the spark created at a receiving electric circuit increased when ultraviolet light hit the negative terminal.

* William Grylls Adams, an English professor of Natural Philosophy at King's College, London was the brother of John Couch Adams, the astronomer who discovered Neptune.

European Solar Days

The First European Solar Days will be celebrated on the 16th and 17th May 2008 with more than 4000 events and will reach thousands of European citizens throughout Europe.

The 'Tag der Sonne' was first celebrated in Austria in 2002, and the idea has already been adopted by Germany, Switzerland and The Netherlands. In the case of Germany a whole week is dedicated to the campaign. This wonderful idea is now for the first time extended to more countries: France, Belgium, Portugal, Spain, Italy, Slovenia, and Norway. In 2009 other countries are expected to join the initiative and the event is planned to be ex-tended throughout Europe in the future.

The European Solar Days will bring together major players from the solar thermal and solar photovoltaic electricity sectors throughout Europe and will help in promoting the use of renewable energy.

The aim of the ESD is to raise awareness and promote the possibilities of solar power, Solar Thermal and Solar Photovoltaic, among both decision makers and the general public.

Comprehensive information on the European Solar Days is available at: www.solardays.eu

Photovoltaic Cells

Picture: DOE/EERE

Photovoltaic cells (PVs) (also known as "solar cells") work by transforming light that comes from the sun directly into electricity without an intermediate mechanical device or thermal process. The term photovoltaic is derived by combining the Greek word for light, "phos", with the word "voltaic". The term "volt" is a measure of electricity named for Alessandro Volta (1745-1827), a pioneer in the study of electricity. Photovoltaics literally means light-electricity.

The basic building unit of PV technology is the photovoltaic cell (PV cell). PV cells are made of a semiconductor material, typically silicon, which is treated chemically. When light hits the cell, a field of electricity is created within the layers causing the electricity to flow. This "photovoltaic effect" results in direct current (DC) electricity which is the same type of current produced by batteries.

In order to use this energy in most homes, an inverter is used to change the DC electricity to AC. Once electricity is generated, it can go to power anything in your house or be stored in batteries for later use. The greater the intensity of the light, the greater the flow across the layers and so the more electricity generated. But such a system does not necessary require direct sunlight to work.

Single PV cells are connected electrically to form PV modules, which are the building blocks of PV systems. Depending upon the application, the solar modules are typically wired together to form an array. Individual PV cells – averaging about 4 inches per side – typically converts 15% of the available solar radiation into about 1 or 2 watts of electrical power. Larger modules or arrays of modules are used to generate power for the grid.

Passive Solar Energy Designs

Here are a few video clips which show how to take maximum advantage of the sun's light and heat using passive solar energy designs: