What do I need and how does it work?
The heart of a Solar PV system is the PV panel which is made up of a number of individual solar cells, typically 60 for a modern panel. Panels are grouped together in strings to meet the space and power requirements. Each panel, under ideal conditions, can produce between 250 to 330watts depending on type; so between 12 and 16 panels are required for a domestic installation of 4kW.
Smaller systems are possible where the size of roof is an issue, with a 5 panel system representing a practical minimum. It is possible to have a system with just one panel, however not economical.
The panel absorbs light and uses the energy to generate DC electricity, like a battery. An inverter is needed to convert the DC to AC electricity, synchronised with the mains supply at your property. The inverter has a number of other functions in addition to the simple task of converting DC to AC.
MPPT, a system that ensures that the panels are operated at their optimum efficiency under different sunlight and temperature conditions.
Auto shut-down, in the event of a power cut, to protect those working on the mains system.
Inverters may also include Bluetooth or Wifi access for monitoring. The power from the Inverter is connected via the generation meter directly to your consumer unit. This enables you to use the power your system makes without it passing through the main electricity meter, so you are not charged for it.
There will probably be some days when you generate more electricity than you are using. This excess will be fed backwards through your meter into the grid for others to use. Most house electricity meters cannot measure this back flow, so the government has estimated that 50% of all you generate ends up back in the grid and pay you an extra payment called the Export Tariff.