We’ve contacted photovoltaics manufacturers for details on warranties, cell types, size and price to help you decide which solar power system is best for your home.
While incentives such as feed-in tariffs and rebates have been reduced or removed completely of late, the steadily decreasing cost of solar PV panels and the steadily increasing cost of mains electricity means that despite the reduced incentives, house-holds and businesses are still installing solar photovoltaics for electricity. Best of all is that this electricity source is clean and renewable.
Photovoltaic panels produce electricity directly from sunlight in a solid-state process—there’s no moving parts to wear out, just large inert panels that have very long lifespans. The most popular use of PVs nowadays is to supplement mains grid power and reduce electricity bills. However, solar PVs have many other uses including to power off-grid houses, water pumping systems and remote communications systems, as well as in large commercial solar power installations.
The different technologies
There are three common types of solar cells: monocrystalline, polycrystalline and thin film.
Both mono and polycrystalline cells are made from wafers cut from blocks of silicon. Monocrystalline cells start life as a single large crystal known as a boule, which is ‘grown’ in a slow and energy intensive process. An example can be seen at right. Polycrystalline cells are cut from large cast blocks of silicon rather than single large crystals.
The cells are then modified by a process known as ‘doping’. This involves heating the cells in the presence of boron and phosphorus, which changes the structure of the silicon in such a way as to make it a semiconductor. This is the same method which is used to make integrated circuits.
Once the wafers have been doped, they then have a fine array of electrically conductive current-collecting wires applied to each side of them.
Thin film technology uses a different technique and involves the deposition of layers of different materials directly onto metal, glass or even plastic. The most common thin-film panels are the amorphous silicon type, which are found everywhere from watches and calculators right through to large grid-connected PV arrays.
In recent years, other types of thin film materials have started to appear. These include CIGS (Copper Indium Gallium (di)Selenide) and CdTe (Cadmium Telluride). They tend to have higher efficiencies than amorphous silicon, with CIGS cells rivalling crystalline cells for efficiency.
Read the full article in ReNew 118This entry was posted on Monday, December 12th, 2011 at 10:56 am