System components
A PV system installed in a house consists of just a few components, which are explained below
Photovoltaic Panels
The panels make up by far the largest part of the system. A panel is made up of PV cells, and many panels make an array.
Light, which doesn't have to be direct sunlight, hits the panel and the linked together panels produce enough electricity to be useful to supply
the building. The electricity produced is in DC, and this needs to be converted to AC to match the supply. This process is done with a piece of
equipment called an Inverter
PV Cell
The cell usually measures around 100mm by 100mm (4" x 4"), and the connections on these are soldered together
and laminated in between different materials. The cells can be laminated under glass for systems that fit to a roof, they can be etched onto glass to make see though
PV panels for use as a window or sky lighting. There are endless ways that a PV cell can be mounted and connected together to form a 'panel' of some description.
The Cell itself is made up of two sections, a positive layer of silicon, and a negative layer, and these are connected together with metal strips.
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In the positive layer, an element called Boron is added (this is known as doping). Because there are 3 electrons on the outer shell of a Boron atom, the boron atoms attach themselves in amongst the silicon atoms but there are spare slots, as all the silicon atoms with 4 electrons are all happily attached to one another.
That's the positive layer (P-Type Silicon) sorted out, now there has to be a negative layer. The negative layer (N-Type Silicon) is doped with phosphorous, which has 5 electrons in the outer shell. Adding this to the silicon makes all the extra electrons that don't have anything to hold on to jump along to the next atom in the layer trying to find something to hold on to.
When the two layers are connected together and the cell is exposed to light, it causes electricity to flow through the silicon.
Inverter
The inverter converts the electricity that's produced from the PV system into electricity that can be used in the house, and can be sent to the grid.
The PV system produces DC (direct current, the kind that comes from batteries) and this power is not able to run in a building electrical system so it
is converted to AC (alternating current). The inverter has complex electronics inside it that will produce AC power to match the power that is on
the national grid. It synchronises the frequency, voltage and amperage to match those entering the building.
The inverter is usually
installed in the loft space, or if there is a basement that has the fuse box in for example, then it can be installed there. Some inverters can be installed
outside. One would not be installed in a living area such as a dining room or bedroom, as there is often a quiet hum made by the inverter (It can't be
heard if the inverter is in the loft).
DC fuse Box
The PV array is connected through the DC fuse box before it is connected to the inverter. The fuse box contains lightning arresters which provide safety to the inverter and the rest of the buildings' electrical system in case lightning should strike the panels. This would be installed right next to the inverter.
Isolators
AC and DC isolator switches are installed before the inverter, after the inverter, and before connection into the buildings' consumer unit (electrical fuse box).
kWh Meter
This is installed to measure the power that is being produced by the PV system itself. This is an extra meter that is installed as well
as the one that would be measuring the power coming into the house. The reading on the meter will be of interest as it tells you how many kWh's (or electrical
units) have been produced so far. The supplier of electricity will also need to take this figure along with the reading from the main meter in order to
calculate your usage of power from the grid, which will of course be less with a PV system installed.
A Frame
Last but not least, a frame will need to be fitted to the roof to provide something to mount the PV panels in or on. If the panels are roof-integrated ones, then each panel may have a special frame to turn them into roof tiles.