The history of solar power

For billions of years, the power of the Sun has been harnessed by algae and plants to produce their vital building blocks glucose and cellulose. A byproduct of this process, which is called photosynthesis, is oxygen, a substance required by all multicellular life on Earth. Although by far not as long as other forms of life, humans have also been enjoying the advantages of solar energy throughout history. The ancient Egyptians used solar heat to bake mixtures of mud and straw into hard bricks for construction. The Greeks and Romans used clever architecture to make use of the Sun’s ability to provide light and heat in a building. This form of solar power is called passive solar energy and is stillused in construction today. A more active application of solar energy was used by the Greeks, who as early as 200 B.C. used bronze shields to focus the sun’s rays on Roman ships, setting them on fire. A similar, although more peaceful, approach was used by the Chinese in 20 B.C. to light torches for religious services.

In 1767, the world’s first solar collector was constructed by Swiss scientist Horace de Saussure. His collector, the so-called hot box, allowed people to cook food during desert expeditions. The true foundation for solar photovoltaic energy was however laid in 1839, when French scientist Edmond Becquerel discovered the photovoltaic effect. His work was expanded upon in 1876, when William Grylls Adams and Richard Evans Day discovered how to turn light into electricity using the metal selenium. Seven years later in 1883, the American Charles Fritts described the first working solar cell. In 1891, the first commercial solar water heater is patented by an American inventor in Baltimore.

The 1900s

In the early twentieth century, only little progress was made in the development of practical solar power. Some important theoretical work was however done in this period.

• 1908: the first modern-style solar collector was built using copper coils and an insulated box.
• 1921: Albert Einstein wins the Nobel prize for explaining the origin of the photoelectric effect, the existence of which was experimentally proven in 1916.
• 1954: the first viable silicon-based solar cell was built. Bell Telephone Laboratories is credited with producing this groundbreaking cell, which could be used for powering smalloff-the-grid equipment. The cell featured a conversion efficiency of 6%. Later on, this efficiency was boosted to 11%.

In the first years, photovoltaic technology was still prohibilitly expensive: solar power was priced at $300/watt at the time, compared to 50 cents a watt for regular power! Consequently, solar cells were only used for a limited number of novelty items, such as miniature ships and beach radios.

• 1958: Solar power finds its first real use. The Vanguard one satellite was launched, carrying a small solar array that powered its radios. Today, solar power still continues to be the power of choice for satellites and space probes. Since solar is often the only power available to a spacecraft, the solar cells employed in spaceflight are of a far more advanced nature than those commercially available.
• 1970: Elliot Berman designed a solar cell that was five times cheaper than the average solar cell of its time period. The price of solar power fell dramatically, from $100/watt to $20/watt.
• 1972: the world’s first dedicated PV research lab is established in Delaware, aimed at developing thin-film photovoltaic cells and solar thermal systems. One of their projects was a completely solar-powered home called “solar one”, which featured a thermal/PV hybrid power system.
• 1977: total photovoltaic production is estimated at 500 kilowatts per year.
• 1980: ARCO solar reports production of a full megawatts worth of PV modules in one year. At the same time, the first 10%-efficient thin-film module was developed at the university of Delaware.
• 1982: in California, the world’s first megawatt-scale PV project is completed and taken on-line. In the same year, the first solar car is driven in Australia; it traverses the distance Sydney-Perth (2,800 miles) in twenty days.
• 1982: Solar One, the world’s first concentrating solar “power tower”, is completed and taken online. Being a demonstration project, the tower was decommissioned in 1988.
• 1985: the first 20%-efficient silicon solar cell is developed at the university of South-Wales.
• 1986: the world’s first commercial thin-film module is released by ARCO solar.
• 1993: the world’s first grid-supported solar power plant is ‘fired up’ in California.
• 1994: the 30%-barrier on efficiency is broken by a solar cell based on the materials gallium indium phosphide and gallium arsenide.
• 1996: the successor to 1982’s solar one tower, inventively subbed ‘Solar Two’, is taken online.
• 1998: solar shingles are invented by Subhendu Guha.
• 1999: the world’s total solar power capacity reaches one gigawatt.

The 2000s

• 2000: solar panels are installed on the International Space Station (ISS).
• 2002: NASA tests a solar-powered aircraft called Pathfinder Plus. Tests involve applications of imagery and telecommunications.
• 2007: a total 2.3 gigawatts of solar power is added worldwide. Almost half of global PV installations is connected to the German grid.
• 2008: as environmental awareness grows, solar panel sales soar. 5.6GW is installed in 2008.
• 2009: the US company First Solar reports that it broke the $1/watt cost barrier on PV manufacturing. Spain takes over from Germany as the world’s largest solar PV market.

Note: due to the large and complex history of solar power, the above history is an excerpt. For a more complete overview, see the solar timeline by the US department of energy.