There are several varieties of solar cell utilised in today’s solar panels and each has its advantages and disadvantages. We will discuss a few here today.
Perhaps the most popular solar panels are constructed from monocrystalline cells. Popular because the majority of installations are along Australia’s eastern seaboard where the main population centres are located. Monocrystalline panels are efficient, suited to unshaded roofs where the temperatures are not too high. For the housing developer they are perfect as the blocks are clear of trees, they can orientate them north and they do not require too much roof space per kilowatt.
How is the efficiency of a solar panel calculated and what efficiency is considered high? If you consider a square of solar panel 1m x 1m, its area is 1m2. Now given a perfect day in which the sun is shining with an irradiance of 1000W/m2, if the solar panel were 100% efficient it would generate 1000W; if it were 20% efficient it would generate 200W. In fact 20% efficiency would be considered ’very good’ as most monocrystalline panels on the market today have efficiencies between 14 and 17%. Most panels these days are approximately 1.6m2 in area and say 16% efficient, hence they generate about 256W.
Very similar to monocrystalline cells are polycrystalline cells, sometimes called multicrystalline. Mono panels used to be more expensive, more efficient and more compact than polys. Nowadays, many companies prefer poly since their performance closely matches that of monos and there may be a small price advantage.
When you purchase a 250W panel, regardless of its cell type, the output is still nominally 250W. Improved efficiencies may see the better panel starting up earlier in the morning, switching off later and handling high temperatures without too much degradation.
A third type of solar cell is the amorphous silicon cell, or thin film. These are much less efficient than mono/poly and hence a greater number of panels is required for a given power output. However if its nominal output is 250W, that’s equivalent to 250W on any other panel type. Thin film panels suffer less temperature degradation and work better in low irradiance so they are often chosen for use in shady or very hot desert conditions.
There is a very comprehensive website at Desert Knowledge Australia in Alice Springs. They have bought a wide range of panel and inverter systems for monitoring. Each system’s performance is there for all to see, warts and all. You can compare brands and cell types.
Another type of thin film panel is the laminated glass sandwich holding a substrate of Cadmium Telluride (CdTe). Because of the threatening nature of CdTe, the manufacturers build the recycling of the panels into the original purchase price to ensure they are recycled responsibly.
Back in the mid 2000s there was considerable research and promises made about a revolutionary cell type known as the ‘sliver cell’. This started as a joint venture between ANU and Origin Energy. Monocrystalline cells were cut into thin parallel strips and rotated through 90o exposing both sides to the sun. The cells looked like mini open venetian blinds. They were then mounted on a reflective backing surface to optimise the ambient irradiance. Unfortunately, manufacturing obstacles prevented these cells from reaching the market.
About the same time as the sliver cell came the sun cube and sun ball technologies. These used solar tracking systems and multiple facets to capture the sun with claimed greater efficiencies than conventional panels. The market waited for these technologies but they never reached fruition.
Energis can quickly determine which panel type will be best for you based on your roof site, geographical location and shading. Please call them on 1300 782 217 to arrange an obligation-free appraisal.
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