10th October 2019
PV module market around the world have been cost driven and it is no wonder that the crystalline technology has been the chalk horse of the industry. Further, with the levelized cost of electricity (LCOE) from solar plants have started breaching grid parity, the focus now is to extract maximum kWh from the plant in order to ensure the investors have maximized returns. The technology upgradation in conjunction with module design upgradation has played a significant role in such shift. Utilization of bifacial module which are capable of generating power from both sides has been gaining traction, given the fact that enhanced energy output could be expected under right designing considerations. However, the currently available bifacial module utilizes PERC/PERT crystalline solar cells which have limited bifaciality coupledwith other inherent issues like LID, PID, LeTID, etc. It was hence necessary to bank upon a pragmatic solution.
Silicon heterojunction (HJT) solar cell which has been introduced in the mid-19th century, utilizes both crystalline and thin film technology. The cell has a crystalline silicon (n-type) sandwiched between amorphous (thin film) layers of silicon on both the sides, giving the cell its bifacial nature. The mono crystalline technology in the cell has better absorption of light whereas the amorphous has superior passivation (which enables high electron collection) characteristics. The cells are thinner (~120 μm) compared to crystalline silicon cell making it slightly flexible and further also making them highly resistant to micro-cracks. The n-type silicon present in HJT does not have Boron, which makes these cells LID free. Further the mitigation of electron from solar cell which are responsible for PID are also reduced to zero in HJT cells, thanks to the presence of highly conductive oxide layer (ITO) which protects the cell electrically. Additionally the cell has a lower temperature coefficient (almost half of the crystalline technology based cells). All the above factors when coupled together enables HJT based module to have lower degradation rates throughout its lifetime.
Figure 1: SUPER HJT module from Waaree energies (on left) and (on right)cross sectional view of a Heterojunction cell (Source: Meyer Burger)
Since these cells have high bifaciality, micro-crack resistance, no LID, PID & LeTID and lower temperature coefficient it is a perfect technology for Indian conditions. Waaree Energies recently in REI-2019 launched their SUPER HJT module which utilizes HJT solar cells. Available next year, this module have already started gaining popularity among the local and international markets. Further with the detailed scrutiny happening for each and every module we manufacture, the end customer can be rest assured that their plant would be up and running for 25+ years ensuring more than desired return.
Figure 2: Comparison of superior technologies existing in PV market