Thin-film PV panels are a second generation solar power technology.
The technology itself has been around since the 1970s. Recall the solar-powered calculators from the late 70s and early 80s. Everyone wanted to own one back at school!
Well, those solar-powered calculators were the first commercial application of thin film solar cells. It was powered by a small strip of amorphous silicon.
The technology has advanced significantly since then but has always been the “ugly duckling” of the more conventional monocrystalline and polycrystalline solar panel technologies.
There was an expectation that thin film-solar power technology would make a significant impact on the market and be a viable competitive alternative to mono- and polycrystalline technologies.
Sadly that has never happened.
In 2010 thin-film solar technology accounted for 15% of the overall solar panel market, but since then has been in decline, stabilising to 7% in 2015.
It’s expected to lose half its market share by end of the decade.
What Makes Thin-Film Solar Cells Different?
For a start, as the name implies, they are a lot thinner than the more traditional silicon wafer cells.
Silicon wafer cells have light-absorbing layers that are normally 350 microns thick. Thin-film solar cells have light-absorbing layers that are just one micron thick.
Now to put a micron into perspective: 1 micron is one-millionth of a meter.
The solar cells are manufactured by depositing several layers of a light-absorbing material, a semiconductor, onto a substrate coated glass, metal or plastic.
The materials used as semiconductors don’t have to be that thick as they absorb light more efficiently.
The advantage to this is that thin-film solar cells are lightweight, durable and easy to use.
Types of Thin-Film Technologies
There are three types of thin-film technologies on the market.
Firstly Amorphous Silicon (a-Si) that in reality is a trimmed down version of the conventional silicon-wafer cell, Cadmium Telluride (CdTe) and Copper Indium Gallium Diselenide (CIGS).
a-Si thin-film cells have some drawbacks though.
Firstly, they’re not all that efficient and they suffer from degradation in power output when they're exposed to the sun.
Now isn’t that ironic? Thinner cells have assisted in overcoming this challenge but still suffer from lower efficiencies.
Conventional solar wafer cells use silicon layers sandwiched in between P-Type and N-Type layers.
These layers act as an electrical circuit and allow electricity to flow from positive to negative.
Later generation thin-film technologies use thin layers of either Cadmium Telluride (CdTe) or Copper Indium Gallium Diselenide (CIGS) instead.
Nanotechnology is now used in the manufacturing of thin-film solar cells and this has contributed to the improvement in efficiencies too.
So just how does thin-film solar technology stack up against conventional silicon wafer cells?
The theoretical maximum for silicon-wafer cells is about 50 percent efficiency, meaning that half the energy striking the cell is converted into electricity.
However, in reality, this number varies within 15-25 percent efficiency. In the lab, efficiencies as high as 20.5 percent have been achieved for CIGS thin-film solar cells and 15 per cent for CdTe. The highest efficiency in the lab for CdTe thin film technology was 17.3 percent. That’s some competition there for you in anyone's book!
A major drawback from CdTe thin-film solar cells is that Cadmium is a highly toxic substance similar to Mercury. This is a major blemish in an industry where the environment is the main focus.
Thin-film solar cells do have some advantages over the traditional silicon wafer cells. For example, they are more flexible than normal silicon wafer cells, easier to handle and believe it or not, cheaper too.
Another major advantage of thin-film solar panels is that they tend to have a lower embodied energy and lower carbon emissions due to the fact that the manufacturing process is less complex and involves less silicon.
Where Is Thin-Film Solar Technology Used?
What do art and solar power have in common?
Well, one wouldn’t think much, but scratch below the surface and think outside the box a bit!
The flexible nature of thin-film solar cells allows quite a bit of creativity when it comes to BIPV - Building Integrated Photovoltaic Panels.
Whilst PV panels are rigid and require racks for installing, thin-film solar panels are laminated to a surface. Their level profile reduces drag, load, and visibility.
Thin films typically come in rolls with a thickness of about 6.35 mm. This means they can be adhered flush to just about any surface, allowing seamless integration into architecture.
This makes thin-film solar cell technology a prime candidate for BIPV architecture and also a lot more aesthetically pleasing.
Globally buildings are responsible for 40% of energy consumption and 30% of carbon emissions.
The green building movement is aiming to reduce carbon emissions and energy consumption originating from buildings. The race is now on
to take it a step further with the implementation of the Zero Net Energy building (ZNE).
A Zero Net Energy building is a building with zero net energy consumption. This means the total amount of energy used by the building on an annual basis is roughly equal to the amount of renewable energy created on site. Zero net energy buildings emit less greenhouse gas than non-ZNE buildings.
BIPV buildings using thin-film solar technology is one solution that is being pitched to achieve a zero net energy building goal along with other renewable energy sources such as wind power.
Top Thin-Film Solar Panel Manufacturers
The Series 6 modules generate up to 8% more energy than conventional crystalline silicon solar modules, with efficiency ratios ranging from 17 to 18% depending on the panel selected.
SoloPower Systems are a world leader in CIGC technology.
SP1 solar panel sizes range from 70W to 90W and efficiency ratios of 8 to 11.9%. SP3 solar panel sizes range from 190 W to 250 W and efficiency ratios from 9.7 to 12.7%
Solar Frontier is a Japanese company and the world’s top manufacturer for CIGS thin-film.
Solar Frontier achieved the world record for thin film efficiency of 22.5% back in 2015.
Solar Frontier offers two CIGS thin-film solar panels of 180W and 185W.
Sharp is a global leader in thin-film solar panel technology. It has been in the industry for over 50 years and is a top manufacturer of a-Si technology.
Thin-film technology has come far since the late 70s and early 80s when it first made its appearance in solar powered calculators.
The original thin-film solar panels utilised the same technology as a silicon wafer, albeit a trimmed down version.
a-Si thin-film technology does suffer from efficiency and degradation issues.
With the development of CIGS and CdTe, efficiency ratios are catching up with monocrystalline and polycrystalline panels.
Thin film solar panels do have some advantages:
- Lower carbon emissions
- Embodied energy originating from the production process
- They are more affordable
- Their flexibility and versatility make the thin-film an ideal candidate for BIPV or Building Integrated Photovoltaics.
Buildings contribute a substantial amount of carbon emissions and energy consumption globally.
Thin-film solar panels have been punted as a solution for zero net energy buildings.
The top thin-film solar panel manufacturing companies include First Solar, SoloPower Systems, Solar Frontier and Sharp.
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