Week 3: Solar photovoltaics
In Week 2 you saw how solar energy can be used to generate electricity by producing high-temperature heat to power an engine, which then produces mechanical work to drive an electrical generator.
This week is concerned with a more direct method of generating electricity from solar radiation, namely solar photovoltaics: the conversion of solar energy directly into electricity, using a solid-state device.
The term ‘photovoltaic’ is derived by combining the Greek word for light, photos, with volt, the name of the unit of potential difference (i.e. voltage) in an electrical circuit.
Hello again. This week we look at ways of generating electricity from solar radiation directly using solid state electronic devices, photovoltaic or PV panels in arrays like these.
PV panels are made from a specially treated junction between two different types of electronic semiconductor, positive or P-type and negative or N-type. When photons of light fall in this junction they generate an electric current producing useful power.
Most PV panels are made of silicon but other materials can be used. And new materials are being developed that may be cheaper or more efficient or both. PV based panel systems can be used to provide electricity for various purposes such as water pumping where there’s no grid available as in many remote areas.
PV power systems are also increasingly being used in areas connected to the grid. They’re usually mounted on roofs and can supply a significant proportion of the energy demand of houses, offices and non-domestic buildings.
Larger grid connected PV arrays are also being installed on land set aside for the purpose particularly in locations with high direct solar radiation levels such as southern Europe. And as with the concentrating solar power or CSP plants we discussed in Week 2 concentration can be used with PV to reduce the number of panels required to produce a given level of power. And here to, tracking systems are required.
The cost of electricity from PV panels was very high when they were first developed from the US space programme in the 1950’s. But costs have dropped dramatically in recent years due to economies and mass production and improvements in efficiency. And although many PV systems currently receive clean energy subsidies projections show that the powerful PV will be competitive with conventional grid power by 2020 without subsidies.