Boosting solar module efficiency
Focus is now shifting towards increasing the efficiency of solar conversion to electricity and cost reduction
If you were to walk into a solar store and purchase some of their best-selling PV panels, it is likely that their solar irradiance-to-electricity conversion efficiency would be around 17%. This is the typical efficiency of the top-selling PV product, a multicrystalline silicon panel. This means that for a typical panel, 17% of all incident solar energy is converted directly to usable electricity.
This is quite impressive for a device that has no moving parts and can generate power at the location where the electricity is required and no transmission losses. It is no wonder that PV is already one of the cheapest power technologies available.
However, the question arises: more than 60 years after the first demonstration of a practical solar cell by Bell Labs, have PV researchers already reached the practical efficiency limit for the technology? According to predictions made in a recent publication the answer seems to be very much a resounding “No.”
Various manufacturing trends that will lead to further major improvements in efficiency over the next decade are already being implemented by industry.
Currently, multi- and mono-crystalline silicon account for more than 90% of the world market. Both multi- and mono- panels are constructed with individual silicon wafer cells. The primary distinction is the crystal structure of the silicon wafers themselves, with mono-crystalline having a higher quality crystal structure than multi-crystalline. The typical efficiency of the most commonly installed panels (multi-crystalline silicon) is around 17%. For the high end of the market (premium mono-crystalline), the value is around 21%.
Boosting solar panel efficiency is very much on the minds of photovoltaic manufacturers. Improving the efficiency of photovoltaic modules helps increase sales and boosts the bottom line. For instance, China headquartered JinkoSolar, which is our Knowledge Partner in this Special Report (p36), recently released its Cheetah module, a commercially mass-produced monofacial module, bringing the industry into the new age of PV 4.0.
JinkoSolar Cheetah series has created a new benchmark for ultra-high performing modules with its industry leading performance in metrics such as output, limited degradation, shade tolerance, and durability.
As manufacturers continually work on bettering their products, consumers win, as their PV systems produce more free energy by harnessing the sun’s power. Photovoltaic modules are made of several components, each of which gives manufacturers more opportunity to improve efficiency.
Photovoltaic manufacturers are working to refine the manufacturing process to improve production efficiency. They are also working to identify better materials for use in panel fabrication.
Specifically, manufacturers are improving the anti-reflective coatings and texture layers, with the goal of improving panel efficiency.
You may have also noticed that most photovoltaic panels feature distinctive grid lines. These are actually tiny metal wires called busbars, and they help with electricity flow from the module. Because the busbars reflect some sunlight, manufacturers are researching ways to eliminate the wires, or to make them thinner to reduce the energy lost due to this reflection.
Photovoltaic modules also have small white spaces between the solar cells, as well as along their edges. By getting rid of these gaps, or finding a way to overlap the cells, manufacturers believe they can boost PV panel efficiency even further.
Most photovoltaic panel designs have solar cells attached to a sturdy backsheet, which means only one side of the module can capture energy from the sun. Manufacturers are exploring the use of bifacial technology, creating clear panels that can absorb light from both sides.
Although this efficiency improvement may not be useful for all photovoltaic applications, it could significantly improve the efficiency of some PV system installations.
But can we expect further innovations to emerge, which will raise the record efficiencies and drag the typical values along with them? According to the International Technology Roadmap for Photovoltaics, there are already some key developments that will do exactly that.