All About Solar Panels

Solar panels are devices that convert light into electricity, they are also called photovoltaic's (pv) which means light electricity. PV cells are combined into solar modules (panels) and assembled in arrays (groups of panels).

The number of modules (or panels) used determines the amount of electricity (units – in this case watts) produced.

As already mentioned photovoltaic panels (or solar pv as they are commonly known) are made up of layers of semiconducting material (usually silicon). When light passes through these layers, the positive electrons and negative electrons collide in the transition layer and produce DC (Direct Current) electricity.

In the home and for most day to day appliances – AC (or Alternating Current) is used, so the direct current produced by solar panels needs to be converted into alternating current. To do this, you need what is known as an inverter.

An inverter is fitted between the output of the solar panel array and the consumer unit to transform the DC electricity into AC electricity. This AC electricity can now be used in your home or, exported to the national grid.

A generation meter is also installed to measure the amount of electricity produced. The meter will take a digital reading of all units you have produced in kWh (Kilowatt Hours). The larger the solar array, the more units of electricity you will produce and subsequently the more tax-free income you will receive.

Even if you have only done the very smallest amount of research into solar panels, you will have already discovered there is a significant choice available – ranging in size, price, output, manufacturer, composition, structure and so on.

It is a bit like buying a car. When you buy a car, you consider a number of factors.

For Example

• The manufacturer
• The particular model
• Engine size options
• Petrol/Diesel/Hybrid (MPG vs Performance vs Practicality)

All of which will effect your decision on which car you buy, depending on your intended usage.

Before deciding on which solar panels will suit your needs best, you should first understand panels used to generate electricity in a system that is connected to the national grid, or to a consumer unit legally - every panel, inverter and generation meter M.C.S. certified, and the installer responsible for signing off the project must be M.C.S. approved.

The MCS is an internationally recognised quality assurance scheme, which demonstrates the quality and reliability of approved products by satisfying rigorous testing and compliance with M.C.S. standards. It was designed with input from product and installer representatives to ensure quality, safety and control to protect consumers (similar to the Gas Safe Register)

Product certification involves type testing of products and an assessment of the manufacturing processes, materials, procedures and staff training to ensure consistency.

Every panel undergoes strict criteria in becoming M.C.S. approved. So, what are you looking for? and, how do you choose? Here are some key factors:

• Roof size. Panels come in different shapes, sizes and prices so practicality plays a big part.
• How much electricity you want your system to produce.
• Name brands like Sanyo and Sharp are a common request because people are familiar with their names, but does that make them better?
• The amount of watts per panel i.e. 185w, 235w, 240w etc.
• The orientation of your roof i.e. South East or West.
• Performance tolerance ratings (+/- %age)* (See more below)
• Mono-Crystalline vs. Poly-Crystalline panels** (See more below)

A common point overlooked with the panels themselves is tolerance rating.

All solar panels have a peak tolerance rating (the maximum amount a panel can possibly produce on a good day) and a negative tolerance rating (the minimum amount a panel can produce on a bad day)

For Example

A panel is listed as having 180W output, with a peak tolerance of 5%, and a negative tolerance of 10%.

• At peak output – the panel could have an output of 189 Watts
• At minimum output – the panel could have an output as low as 162 Watts

It might not sound like much on just one panel, but across an array of panels over time, the difference is significant to say the least!

When shopping for solar panels, two important factors to look for are the highest minimum warranted power rating and the lowest negative tolerance rating (or the lowest peak negative tolerance rating).

Remember: A solar panel manufacturer's claim of having a high efficiency rating is worthless if the solar panel has a poor minimum warranted power rating.

Solar panel manufacturers offer a warranty stating that their solar panel's actual power rating will not be less than a certain amount.

For example:

A 200W solar panel has a negative tolerance rating of -10%. The moment you plug the solar panel in – it is only guaranteed to produce 180W of electricity.

If you compare this against a 190W panel that has a negative tolerance rating of only -3% the 190W panel will, over time, produce more electricity because its lowest rated output will be 184.3W.

Both poly-crystalline and mono-crystalline solar panels are made from the same material, silicon.

However, there are differences in the manufacturing processes.

• A mono-crystalline panel is made using large, complete sheets of silicon sliced from one large block.
• A poly-crystalline panel is made using lots of pieces of silicon cast together to create each sheet.

(To the right is an example of a Mono-Crystalline Panel)

The differences to the end user are as follows:

• Mono-crystalline cells are more efficient in lower temperature climates with variable weather patterns (i.e. here in the UK and the Northern Hemisphere.)
• Poly-crystalline cells, although less efficient, are slightly cheaper and more effective at dispersing heat in very hot climates (i.e. on the Equator or in Australia.)

(To the right is an example of a Poly-Crystalline Panel)

Mono-crystalline panels are more efficient at converting photons to electrons for electricity; the poly-silicon is much less efficient because electrons are captured (or generated) less efficiently where the crystals of silicon touch

You can of course use poly-crystalline panels in the Northern Hemisphere; they need to be slightly larger to achieve the same efficiency.

Choosing which panels is not as straight forward as you might think, and not something that should be quoted over the telephone without all the facts being taken into consideration.

It is important that your property has first been surveyed by a competent person and all the options are assessed to ensure you are installing the most efficient system to suit your needs – and subsequently explained to your satisfaction and understanding.

At SquareDeal Solar we stock several different panel types and inverters depending on your needs. If you want to request a specific panel type and/or inverter, we can order, install and commission it for you, provided the equipment is M.C.S. approved.

I want you to gain the maximum output possible by choosing the correct panels and the correct inverter to compliment the whole system perfectly (after all it is in our best interests for you to be content with the returns we have quoted you (via Export and F.I.T.) and that the system does exactly what we said it would.)

After being in business for 25 years, we are well aware that it can only take a minute to ruin a reputation. Here at SquareDeal Solar – we pride ourselves on providing quality, honest advice and customer satisfaction. You can be assured that any system we fit will do exactly what we have said it will.