Introduction to photovoltaics

Introduction to photovoltaics

Photovoltaic cells, or solar cells, are widely used today. Almost everyone has solar cells at home. Usually grey, blue or black, they don't move, don't make sound and don't cause any emissions while they run. Despite this seeming lack of activity, they power pocket calculators, watches, garden lamps - and increasingly they contribute electrical power to the grid.

The light falling onto them is their energy source.

Solar cells are the main component of photovoltaic systems. For power generation outdoors, multiple cells are packed into durable solar modules, typically about one square meter in size. In most cases, the modules have a glass front. Much like in a window, this glass layer lets the light through, but protects the cells. Modules are never opened until the end of their useful life, after some 25 or more years, when they are recycled. They can be cleaned, like windows, but usually that is not necessary.

A solar module has electrical connections. When light falls onto the cells, a voltage is created between these connections making it possible to establish a usable electrical current. In many ways, a module behaves like car battery, except that its output depends on how much light falls onto it.

Because the raw power output of solar modules varies when the illumination changes, a photovoltaic system usually has some power conditioning elements. These are standard electrical components such as inverters, transformers and batteries, depending on how the solar energy is to be used.

Photovoltaic systems generate power, on the scale of milliwatts (for pocket calculators) to ~200 watt (solar module) to many megawatts, where many modules are installed side-by-side in solar power plants.

Over time, this adds up! After over 10 years of government support, Germany now has a total installed photovoltaic capacity of more than 20 GW all connected to the grid. At midday on a sunny day, they can satisfy up to 35% of Germany's total electricity consumption.

Quietly, without emissions or a penny spent on fuel.

Introduction to photovoltaics
How do they work
Who uses them
Why photovoltaics
What can they do for you
Why now
Frequently asked questions