What is photovoltaic energy?

The word ‘photovoltaic’ carries its own meaning:  ‘photo’ mean light, and ‘voltaic’ comes from the word voltage—which is one of the units used to measure electricity.

Often written in short form as PV, a solar or PV panel is made up of many small solar cells all connected together.  Each solar cell, when exposed to sunlight, produces a small electrical charge.  This is the photovoltaic effect.

The  physics of the photovoltaic effect was finally brought to life when the first silicon photovoltaic (PV) cell was developed at Bell Labs in the USA in 1954. Bell Labs produced a silicon solar cell with only 4% efficiency–but later managed to raised this to 11%.

Silicon is the most common material used in solar cells, representing approximately 90% of the modules sold today. Crystalline silicon cells are made of silicon atoms connected to one another to form a crystal lattice. This lattice provides an organized structure that makes conversion of light into electricity more efficient.

Solar cells made out of silicon currently provide a combination of high efficiency, low cost, and long lifetime. Modules should last for 25 years or more–still producing more than 80% of their original power after this time.

More sophisticated are the thin-film solar cells.

These cells are made by depositing one or more thin layers of PV material on a supporting material such as glass, plastic, or metal. There are two main types of thin-film PV semiconductors on the market : cadmium telluride (CdTe), and copper indium gallium diselenide (CIGS). Both materials can be deposited directly onto either the front or back of the module surface.

The efficiency of the cells has also improved.  The first solar cells only converted about 10 % of the sun’s energy to electricity. The efficiency of commercially-available solar cells now is closer to 20%.  In the lab, efficiencies can reach closer to 50%.

A large PV installation in China

The technology, at first very expensive, started to become commercialized in the 1960s–mainly for satellites that needed low levels of power for long periods of time. In 1958, Vanguard I & II, Explorer III, and Sputnik-3 satellites were launched–each powered by solar PV arrays. In 1959, Explorer VI was launched with an array of 9600 cells.

PV powers up

In 1978 a 3.5 kilowatt solar array was installed on the Papago Indian Reserve in southern Arizona—the world’s first village PV system.  A few years later, in 1982, the first megawatt-scale solar photovoltaic power plant started up in Hesperia, California.  The PV panels with a peak output of 1000 kilowatts, were installed on 108 tracking structures that kept the panels facing the sun over the course of the day.

But what has shaken up the energy world over the last 20 years is the way that the cost of generating electricity from this reliable, clean, and renewable source of energy has dropped so far and so fast. Photovoltaic power is now one of the least cost options—cheaper than all the fossil fuels.

Not surpringly, the development of huge megawatt-scale PV power plants is now underway.

In early 2018 it was reported that Saudi Arabia and SoftBank Group Corp. had signed a memorandum of understanding to build a $200 billion photovoltaic power plant that would be exponentially larger than any other project worldwide.

The deal is the latest in a number of record-breaking announcements from Saudi Arabia—a country that is promising to massively scale up its access to renewable energy.

PV array in Chile

At 200 Gigawatts (that’s 200 billion Watts), the photovoltaic power plant planned for the Saudi desert would be about 100 times larger than the next largest proposed utility-scale PV development, and more than double the level of power that the global photovoltaic industry installed in 2017.

Two hundred billion dollars for two hundred billion Watts—that’s one dollar USD per Watt.  No fossil fuel alternative can match that price.

There’s also a key point to bear in mind.  As solar cells and PV panels become cheaper, they start to become the most cost-effective option even in regions with lower levels of sunlight.  An installation will require more panels to get the same output as an installation in a sunnier region. But if the panels are cheap—it’s not necessarily a serious problem. And the ‘balance of system’ costs–which represent the major component of the capital cost, don’t change, because even though the array is larger the power output is the same.

This means that even in areas not generally thought of as good for solar energy–like Canada, photovoltaic power can still be a cost-effective and viable option. And let’s not forget: there are no moving parts, no emissions of harmful greenhouse gases, and no noise. This is the cleanest of the clean technologies.

For more on the modern technology and its huge potential go to //www.climatezone.org/renewable-energy/photovoltaic-energy/