Photovoltaic solar power

The principles of Photovoltaic Power (PV) were discovered in 1839 by Alexandre Becquerel (F) with the first prototype built in 1883 from Selenium and Gold by Charles Fritts (US). Today, photovoltaic cells are essentially semiconductors. PV is based on the photoelectric effect, i.e. when sunlight strikes the cell, a certain portion of its energy is absorbed which releases free electrons. PV cells are “doped” so that electrons flow in one direction only, which together with a voltage ultimately creates electric power. A complete PV system consists of modules of solar cells, power Conditioner to guarantee required voltage and optional storage devices such as batteries.

The dominant technology today is silicon wafer. It accounts for more than 86% of the solar cell market. Typical thickness of solar cells is between 200 and 300 microns. Thin-films (e.g. Amorphous Silicon, CdTe, CIGS) provide a number of advantages such as that thin-film deposits (~5 microns) of semiconductors significantly reduce the demand of raw materials required for cell design. Typically, efficiencies of thin-film solar cells are lower, but manufacturing costs are significantly reduced leading to a lower cost per watt. Less support is needed when placing panels on rooftops and it allows fitting panels on light materials or flexible materials.

Generally, the most significant improvements are expected to be in production techniques and thereby reducing the average cost per watt.

                        

Wind vs sun : financial comparison

A 2MW wind turbine can provide around 3.5m kWh in a year at an average wind speed of 6m/s for an investment of less than £2m, where 4MW fixed PV system would generate around 3.2m kWh in Southern England for an investment of around £14m. UK PV is therefore approximately 7.5 x the equivalent cost for big wind power. The same 4MW fixed PV system would generate around 5.6m kWh in Spain for £14m. So even in Spain, a fixed solar system would be > 4 x more expensive than a big wind turbine and today only massive subsidies will bring down the financial payback time below the life-expectancy of 20-25 years.