PhotoVoltaic Cells and Concentrating Solar Power

In Physics, Light is described by two theories: Wave theory and Particle Theory.

The Wave theory describes light as Electromagnetic waves of various frequencies; whereas Particle theory describes light as Photons traveling in a straight line.

There are two ways to generate electricity from light energy: using Photo-Voltaic (PV) cells and by concentrating the light rays onto a small surface to produce heat and use that heat to drive a turbine, which in turn drives a generator producing electricity.

PV cells, as name suggests, convert the incident light directly into electricity. This phenomenon is described using the Particle theory. Incident photons (light particles) strike on the PV cell (made of special grade Silicon - a semiconductor) and "knock off" electrons. These "free" electrons start flowing through a circuit forming an electrical current.

CSP (Concentrating Solar Power) uses the heat component of the light. This phenomenon is described using the Wave theory. When electromagnetic waves are incident on various surfaces, they are mainly absorbed or reflected or they just pass-through the surface. When the waves are absorbed in a surface, heat is produced. This heat can be utilized to heat water (or a heat transfer fluid, which in turn heats water). This principle is used in Solar Water Heaters that we see on roof-tops. Now if large amount of "concentrated" waves hit a surface then a large heat is produced. This large heat produces a "super-critical" steam and a very high pressure is developed. This "dry" steam at a high pressure drives the steam turbine, which in turn drives an electrical generator to produce electricity.

PV cells work relatively efficiently in cold conditions with ample sunlight. In India, one such place is Ladakh; whereas CSP works better in hot conditions with ample sunlight. In India, the place is Thar desert.

PV cells are very expensive to produce as one requires a sophisticated manufacturing plant to produce the high grade silicon. Furthermore, the efficiency of PV cells is still very low to produce a cheap utility scale power (at least a few hundreds of MW).

A typical CSP plant requires mirrors that are easier and cheaper to produce. CSP plant can produce utility scale power and can double-up as a water desalination plant as well. A CSP plant can have the potential to transform the local area into a developed town since it operates on a very large scale.