Photovoltaic panels produce electricity from sunlight by making use of the photovoltaic effect, the phenomenon that certain materials produce electric current when exposed to light.
Photovoltaic cells themselves produce only small amounts of electric current, and so to produce a useful output for domestic or commercial use, cells or modules are connected together to form an array.
Output from solar cells and modules is measured in Watts peak (Wp), with a typical module producing around 75 to 120 Wp. With a typical domestic system requiring 1 to 2 kWp, between 9 and 26 modules are required to produce the load in an array, covering anywhere between 10 to 40 square metres of roof space, depending on technology and orientation. As PV arrays generate DC electricity an inverter is required to convert to AC, and allow for connection to the grid.
Different types of PV cells exist, with differing costs and efficiencies, and so it is important to ensure that the correct array is chosen for the particular application.
We have recently been involved in the specification and installation of a 10kWp system in the Wear Valley, on a start up business facility. This system is rated at 10kWp, and can produce between 8 and 11,000kWh of green electricity per year. Although currently expensive to install, costs for PV systems are falling, and coupled with rising utility costs, available grants, and the newly proposed feed in tariffs, cost effectiveness of these systems will continue to improve rapidly.