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Different types of solar panels


Poly vs Mono vs Thin Film

There are so many suppliers and manufacturers of solar panels in the Australian market, and with so many different panels on offer, it can be hard to determine the fact from the fiction. Some companies will offer you 'high efficiency, commercial grade' solar panels, using the 'latest technology', but what does this mean?

Below we have listed the most popular types of solar panel available in Australia, with the benefits and drawbacks of each technology:

 

POLYCHRYSTALLINE MODULES

Polycrystalline (or multicrystalline) modules are composed of a number of different crystals, fused together to make a single cell (hence the term 'multi'). They have long been the most popular type of solar module, due to the lower cost in manufacturing the cells. Recently, the cost of monocrystalline has come down, making them more popular in the residential market.

 

 

As you can see in the image (left), the construction of these different crystals gives the solar panel a visible crystal grain, or a 'metal flake effect'. They are slightly cheaper to produce than Mono panels, but are also less efficient (anywhere from 0.5% to 2% less efficient depending on the manufacturer). This is because the crystal grain boundaries can trap electrons, which results in lower efficiency.

The BP Solar modules that EnviroGroup installs are approximately 13.5% efficient (meaning that if 100 Watts of potential solar energy strikes the panel, it will produce approximately 13.5 Watts of solar electricity).

These panels are very popular in Australia, and offer a good balance of value vs performance.

 

Cost effective to manufacture

Not as efficient as mono

Good efficiency

 Has more silicon - high embodied energy

Commonly available - easy to replace

Takes up small area on roof

 

 

 

MONOCHRYSTALLINE MODULES

Monocrystalline, as the name suggests, is constructed using one single crystal, cut from ingots. This gives the solar panel a uniform appearance across the entire module. These large single crystals are exceedingly rare, and the process of 'recrystallising' the cell is more expensive to produce. 

 

 This technology is now the most widely available in Australia, with the cost of producing monocrystalline cells coming down every year. They are still more expensive than polycrystalline, but can be up to 2% more efficient. EnviroGroup uses SunOwe (14.5%) and Suntech (16.5%) monocrystalline solar modules for our installations.

Suntech have recently made some exciting developments in monocrystalline efficiency, with the patent pending Pluto technology. Unique texturing technology, with lower reflectivity, ensures more sunlight can be absorbed throughout the day even without direct solar radiation, and thinner metal lines on the top surface reduces shading loss. Importantly, the process was developed at the University of New South Wales, and has achieved lab efficiency of 25%, and verified efficiency of approx 19%. These panels will be more expensive, but will offer far more solar electricity for less area of solar panel.

 

 

Most efficient module available

More expensive to produce

Most popular technology on market

Has more silicon - high embodied energy 

Commonly available - easy to replace

Takes up small area on roof

 

AMPORPHOUS MODULES

Amorphous (or 'thin film') solar modules have recently become very popular in the Australian market. They offer better performance in higher temperatures, and have some benefits in shady locations. However, the benefits have been greatly exaggerated by some suppliers, and it is important to weigh that up against the negatives of thin film technology.

The manufacture of these panels is highly automated - silicon is sprayed onto the substrate as a gas (called 'vapour deposition'), which means that the silicon wafer is approx 1 micron thick (compared to approx 200 microns for mono and poly). This means that the panel uses less energy to produce, therefore will pay itself back from an energy point of view in a shorter time. However, it also means that the panels are far less efficient than mono or poly (approx 5-6% efficient).

The electrical connections are etched by a laser. Etching these as long horizontal cells across the panel makes these less susceptible from being blocked by shade, but it's important to recognise that there will still be a significant drop-off in performance when the panel is shaded.

Thin-film panels are significantly less efficient than crystalline panels, and a greater number is required for the same output. On average, a thin film solar array will need 2.5 times more roof area than mono or poly. This is critical if you intend to increase the size of your system later, as you may take up all of your north-facing roof for a relatively small system.

One of the biggest selling points of thin film is the performance in hotter temperatures. Unfortunately this has been misrepresented by some suppliers of thin film panels. As an example, if you live in Melbourne, and you are shown a graph that indicates the performance of thin film panels in Alice Springs, it's obvious that those panels won't provide the same advantage in a cooler climate.

 

 

Partially shade tolerant

Poor efficiency (6%)

More effective in hotter climate

Takes up more space for same output 

Uses less silicon - low embodied energy

New technology - less proven reliability

No aluminium frame - low embodied energy

 Less popular - harder to replace

 

 

OTHER TECHNOLOGY

There are many other types of technology which aren't so well known. Cadmium telluride panels have been used in a number of installations in Australia, and are providing a cheaper option when compared to more common technology. Due to the toxicity of cadmium telluride, there has been limited uptake of these modules within the industry. There are a number of studies underway to determine the long term effects of using this technology to produce renewable energy. Another issue is the extreme rarity of tellurium (1-5 parts per billion), which could reduce the future uptake of this technology.

 

 

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