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Types of Solar Panels

Solar panels can be generally divided into 3 distinct variations. These are the traditional silicon, wafer based PV and Thermal panels and the relatively new Thin Film solar cells.

PV (Photovoltaic) Panels

These are generally the most widespread, and popular, due predominately to the Feed in Tariff, whereby Homeowners can install panels up to 50KW/Hr, and sell excess electricity at a higher than market rate. This has consequently reduced the payback significantly, and many can now expect a typical installation to redeem its capital outlay within a few years.

There are, however differences in PV panels, these include:

Mono-cyrstalline

Mono- crystalline cells have been widely used for many years, and are amongst the oldest, most efficient and reliable of solar panel types, and each module is made from a single silicon crystal. They are readily available, and as such, the majority of solar PV panels on the market are Mono crystalline. Although being relatively efficient, they remain expensive to produce.

Poly-crystalline

These solar panels consist of a number of small crystals. They are typically cheaper and are used in smaller units. Conventional multi crystalline solar cells traditionally have lower efficiencies, and as such tend to be produced in larger modules.  This continues to change though, with the advent of new products, such as silicon nitride multicrystaline cells, which are rated higher then mono crystalline cells.

PV panels can be installed to a variety of different roofs, which dictates their installation type.  Generally, for most pitched roofs they are rack mounted and integrated onto the roof. On flat roofs, they are fixed on ballasted penetrative units.

PV panels have a service life of approximately 25 years, but may last anything up to 40 years, if kept in good condition. There are a number of installation, maintenance and reliability issues.

Solar Thermal

There are generally, three main types of solar thermal panels. These are:

Glazed flat plate collectors

Flat plate collectors are generally the most commonly seen thermal panels. They consist of an insulated glass box with a glazed cover often with an aluminium oxide coating, and dark absorber plate, which transfers heat to circulating fluid, which may be water or air based. These systems rely on radiation to provide direct heating for users needs, however they do lose energy in the form of conduction, which occurs across the glazing.

Evacuated tubes

Evacuated tubes tend to be more advanced in design and therefore expensive than flate plate collectors. They consist of an array of glass tubes, coated with an absorbent coating, and contained within a vacuum is housed a copper pipe that transmits heat via radiation along its length.

This is a sealed system, and as such requires minimal maintenance over its lifetime. It also works in freezing conditions, as the heat pipe contains anti freeze, which allows heat to be produced from very low temperatures.

Unglazed plastic or low temperature collectors

These are similar to the glazed flat plate collectors, with the exception of a glass covering. As they are not insulated, a large proportion of heat is lost; this makes them most suitable for low temperature applications. They are usually made of black plastic, designed to withstand UV light and are generally used to heat swimming pools.

These have a number of system design, installation, and maintenance issues.

Thin Film (Amorphous) Solar panels

Thin film technology is still relatively new, and consists of photovoltaic material deposited on a substrate, which are a few millimetres in thickness.

There are a number of variations, all of which depends on the type of photovoltaic material used.  These include Amorphous Silicon, Cadmium Telluride to DSSS (Dye Sensitised solar cell) and Organic solar cells. Currently however, due to the higher costs associated, these do not have a significant market share.