Solar photovoltaic energy

Solar photovoltaic energy deals with the conversion of the sun‘s rays directly to electricity, and is related to the technology and the research it involves. Because renewable sources of energy are in high demand now, solar photovoltaic energy is increasing in importance. In recent years, research in the field of solar photovoltaics has been accelerating to levels unseen before. This is on par with the global use of solar photovoltaic energy, which has been doubling every two years since 2002. Since 2001, worldwide solar power capacity has grown from 1.3 GW to a staggering 15.2 GW in 2008. Solar photovoltaics can therefore safely be labeled as the world’s fastest growing energy technology. Note that in 2008, almost 50% of the world’s new solar photovoltaic installations were built in Spain alone! Although 2009 will see a global market contraction due to the economic crisis, the resulting market consolidation will see the emergence of industry-leading giants. These companies will likely be able to supply massive economies of scale.

At the heart of solar photovoltaic energy is a physical process called the photoelectric effect. It is the phenomenon in which electrons are excited to a higher state after absorption of incident electromagnetic radiation. Photovoltaic cells utilize this principle in order to produce electricity from sunlight. They do this by allowing photons to interact with a thin layer of semiconductive material. This material is usually a very pure form of mono- or polycrystalline silicon. It consists of two separate layers; one p-type layer (electron acceptor) and one n-type layer (electron donor). The interaction between sunlight and the n-type material produces electrons in an excited state, which break free from their host atoms and adhere to the top side of the panel. This adherence is explained by the presence of an electric field at the boundary layer between the n-type and p-type semiconductors. The result is a small (~0.5V) difference in potential between the top and bottom of the cell. When connected, an electric current will flow. In order to obtain higher voltages (and currents), solar cells are often interconnected in a serial configuration.

The kind of electricity produced in solar photovoltaics is direct current (DC), which is the same type of current given off by a battery. DC is commonly used to power portable equipment or recharge a battery. Off-grid DC power is commonly used in roadside telephone booths, remote sensing and remote off-grid homes. Initially, photovoltaic energy was only used to power satellites and interplanetary probes. However, due to the recent sharp price drop in solar panels, it is now also commonly used in grid-tied solar power generation. For grid connection, the DC power needs to be converted to AC (Alternating Current) power. To facilitate this conversion, you will need a solar inverter.

It is estimated that by the year 2030, solar photovoltaic systems will probably be generating 1,864 GW of electricity worldwide. This means that almost 14% of the population of the world will be satisfied by the solar power produced globally in about 25-26 years’ time. Note however that this is not enough: with 89 petawatts of sunlight reaching the surface of Earth at any given moment, we need to only convert about 0,0002% of the sun’s power to electricity to fully power humanity. That is, assuming a non-growing global power consumption of 15 terawatts.

Besides the manufacturing process, photovoltaic energy is almost completely pollution-free. Solar power plants require no expensive fuel transports, are completely silent and are emission-free. Once built and operating, a solar power plant requires little additional investment. All it takes is regular cleaning of the panels and the occasional replacement of defective modules.

Video: introduction to solar photovoltaic energy