The Basic Idea
Solar Photovoltaic or PV systems generate electricity from sunlight. This electricity can then be used to power appliances in your home (TV, lighting, kettle, tumble dryer…), instead of you having to draw it from the grid. In addition, any electricity you do not use yourself is ‘exported’ back to the grid.
Grid Connected & Off-Grid
There are two types of photovoltaic system that you may have heard of, “Grid Connected” and “Off-Grid”. Off-Grid systems generate electricity, which if not used immediately, is then stored in specially designed batteries on the premises. These are quite complex systems, which are rarely used in domestic properties in the UK.
It Won’t Cost The Earth only sell Grid Connected Systems which use electricity for the household appliances and then export any excess back into the national grid network.
A Bit More Detail
There are 6 major components in a Solar Photovoltaic installation:
- Solar Panels
- Solar Cabling
- AC-DC Inverter
- Safety Isolators
- Total Generation Meter
- Mounting Kit
1. Solar Panels
Solar Panels contain photovoltaic cells that are made from crystals of silicon manufactured into thin layers which act as semi-conductors. When light falls on the layers, electrical charges in the semi-conductive layers separate and produce a Direct Current (DC) voltage.
At It Won’t Cost The Earth we use both polycrystalline and monocrystalline panels manufactured by various manufacturers. We mainly use Schott and Upsolar, but also Sanyo high efficiency HIT and some other brands. Panels do vary in size, but the most popular size we sell are around 1685mm (H) x 994mm (W) x 46mm (D).
The number of panels you install will depend on two factors:
- the area of roof available, and
- the budget.
We will consider what size will fit best on your roof; whether to fit in Portrait (long side vertical) or Landscape (long side horizontal); and what size system you are interested in. For instance, a small roof, where a high generation system is required will make us consider high efficiency Sanyo panels – but the price per Watt installed will go up.
And how important to the customer is the panel manufacturer’s reputation, track record and, quite frankly, quality? We only supply high quality panels, but a decision between, for instance, Schott and Upsolar will consider these aspects.
As a simple rule the more panels that are installed, the greater the electricity generation potential.
2. Solar Cabling
The solar cabling transfers the DC electricity produced by the panels via a safety isolator to the inverter. This cabling is of a very high specification and is double insulated, reflecting the extreme caution with which DC electricity must be treated.
3. AC-DC Inverter
The Direct Current (DC) produced by the panels needs to be converted into usable Alternating Current (AC) for the home. This task is performed by the inverter. A lot of care is taken to match the inverter to the number and layout of the panels in order to optimize the efficiency of the system. The inverter will also display some data such as total amount of electricity generated since commissioning, amount being generated at that moment or over various periods (day / week/ month/year). This funcationality varies by brand and model.
4. Safety Isolators
At least 3 isolators are used on each installation. A DC isolator (as in 2 above) is positioned between the panels and the inverter in order to be able to isolate the DC current as necessary, and two AC isolators are placed between the inverter and the point of connection to the grid either side of the total generation meter. This is in order to ensure safe operation of the system during is lifetime as well as to protect those who may work on it or other parts of your electrical system.
5. Total Generation Meter
The Total Generation Meter simply measures the electricity produced by the Solar PV system. The utility meter is not an export meter or ‘smart’ meter. Different power companies supply their own export meters (they do charge you for it!) and these enable the amount of electricity exported to the grid to be measured.
6. Mounting Kit
The mounting kit for a roof installation comprises a number of components, notably: roof brackets, rails, splices and all related fixings such as nuts bolts and screws. Each kit is specified according the array layout and roof structure and materials.
What it all means
Simply, you produce electricity yourself when there is light falling on the solar panels. You can use this electricity to power your household appliances (lights, TV, washing machine, immersion heater, kettle…the list is very long these days!) and anything that you do not use – if, for example, you are out of the house or on holiday – goes back to the grid.
Of course, this also means that you need to take less power from the grid and that therefore your electricity bill will be lower. In fact, depending on the size of system you install, instead of writing out a cheque you could well be receiving one!
It also means that you will be reducing your carbon footprint because instead of energy having to be generated in a power station by burning fossil fuels and then transported inefficiently to you, it is generated in situ by the sun on your roof!
To see what this might mean financially, please go to our Financial Benefits pages.