BKCHAP09-2011 - Chapter 9 PHOTOVOLTAIC SYSTEMS 9.1...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
9-1 Chapter 9 PHOTOVOLTAIC SYSTEMS 9.1 Introduction Photovoltaic (PV) systems directly convert sunlight into electricity with no intervening heat engine.Basic conversion device used is known as solar photovoltaic cell or a solar cell . Functionally a solar cell is an electrical current source, driven by a flux of solar radiation. PV systems are solid state; therefore, they are rugged, simple in design and require very little maintenance.Perhaps the biggest advantage of solar PV systems is that they can be constructed as stand-alone systems to give outputs in the ranges from milliwatts to megawatts. That is why they have a vast array of applications, such as, calculators, watches, water pumping, remote buildings, communications, satellites, space vehicles and even megawatt scale power plants. In today's energy and environment-conscious society the clean and seemingly inexhaustible source of energy from PV provides an attractive option. Once a very high priced technology, used exclusively for space applications, photovoltaics is now well-known around the world and is finding rapidly expanding energy markets even in the remote parts of the world. Millions of PV systems have been installed around the globe. For remote lightingand communications, PV systems with battery storage have provided the most cost-effective source of electricity for many years. Now electric utilities are using PV systems to provide power to sectionalizing switches area and warning lights, and for cathodic protection. French physicist Edmond Becquerel first discovered the photovoltaic effect in 1839. He noted a voltage appeared when one of two identical electrodes in a weak conducting solution was illuminated. This effect was, however, first studied in solids, such as selenium, by Heinrich Hertz in the 1870's. Selenium was quickly adopted in the emerging field of photography for use in light measuring devices. Selenium cells have never become practical energy conversion devices due to their high cost relative to the small amount of electricity they produce at 1% efficiency. In the 1920's and 1930's quantum mechanics laid the theoretical foundation for our present understanding of PV. Major steps towards the commercialization of PV were taken in the 1940s and 1950s when a method (called the Czochralski process) was developed for producing highly pure crystalline silicon. In 1954, scientists at Bell Laboratories used the Czochralski process to develop a silicon solar cell at 4% efficiency. Conversion efficiencies were soon improved to 6% and then 11% at Bell Laboratories. In 2011 these efficiency numbers are more like 25% at the cell level. A few attempts were made in the 1950's to use silicon PV cells commercially, but were met with little success. The major boost for PV cell technology came from the space program. In 1958, the U.S.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/16/2012 for the course ECE 5374G taught by Professor Srahman during the Spring '12 term at Virginia Tech.

Page1 / 58

BKCHAP09-2011 - Chapter 9 PHOTOVOLTAIC SYSTEMS 9.1...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online