A beginners guide

PV = Photovoltaic. Photovoltaic comes from Photo meaning light and Voltaic meaning Electricity. A Photovoltaic system is a system that can convert “radiant” energy, in this case sunlight, in to electricity.

How Does It Work?

A solar panel is made up from solar cells. Each cell is connected to the next cell in series. As the light hits the cells it excites the electrons thus creating electricity that is then passed along the wires from one cell to the next.

Solar Panels

Solar panels are made from an aluminium frame. The cells are placed on a backing and wired together in series. The voltage depends on the cells and the current on the number of cells. The larger the current required the more cells are put into the panel. Each panel comes complete with wires that can be connected to the next panel or directly in to the inverter or controller. The panel is then put in to a laminating machine. The panels are guaranteed for 20 years although tests are implying they will last a lot longer.

Inverter/Controller

The panels produce electricity in DC, as used by batteries. A common example of an Inverter is the box on the power cable that connects a laptop computer to the power supply. Here the laptop works on DC (battery) but the electricity in the house is AC, the box inverts the power.

Where panels are connected to batteries then a controller is needed to stop the batteries from being over charged. Where they are connected to the power supply then an inverter is needed to convert the DC electricity into AC.

Inverters come in various sizes and their maximum power should exceed the maximum power output of the panel array. For example Use The Sun inverters are able to deal with 20% more power than the panels can produce (Our 1kw system uses a 1.2kw inverter).

The panels are wired in a single series to the inverter. The Use The Sun 3.68kw system, for example, is 16 panels with a voltage of (36 x 16) = 576 volts DC. The inverter accepts the electricity and then swaps it to UK mains standard of 230 volts AC.

Will The System Produce All The Electricity I Need?

The simple answer is NO. The panels will produce between zero and their maximum output dependant on the pitch and direction of your roof (the more south facing the better), and, most importantly, on the weather. As a rule of thumb a 1kw system will produce between 750 and 850kw a year but this will vary.

So when it is sunny you may produce more electricity than you need, when it is dark you will produce less than you need. It will also depend on the amount of electricity you are using. The simple answer is to stay connected to the grid. When you over produce (maybe during the day whilst at work) you sell to the grid and when you need more (at night when you are cooking, watching TV, using your computer etc) you buy from the grid.

The beauty is the system takes the power as and when needed and you, the home owner, will never notice any difference or loss of power.

Should I Have Battery Back Up

The opinion of Use The Sun is NO, batteries are expensive and need maintenance, it is easier to use the grid. However there is a lot of time and effort going in to battery research at the moment and our opinion is likely to change in the next few years.

When the new smaller and more powerful batteries are available we will offer our customers the option to add them to their system.

What Sort Of Meter Should I Have

There are 2 types, one meters just the electricity you are producing the other meters how much you produce and how much you export to the grid. If you have the first type it is assumed, for payment purposes, that you will export 50% to the grid.

If you are regularly at home during the day, using electricity, then the first option is better. If you are regularly out during the day then it might be better to splash out on a more expensive meter to increase income from exporting.

How Much Will I Earn

That is difficult to say as it depends on the amount you generate but as a rule of thumb if you have a 1kw system generating say 800kw a year then you will receive

For generation 800 x 41.3p = £330.40

50% Exported 400 x 3p = £12

The 3p per kw exported is the minimum set by the government and that is likely to increase over time.

Plus the electricity that you generate and use yourself is FREE. This avoids purchasing electricity, current purchase price is upwards of 12p per kw.

The 41.3p per kw produced is guaranteed for 25 years and, best of all, it is tax free!