If we look back at the progress we’ve made in solar technology at the 3Sun Gigafactory in just ten years, it’s enough to make our heads spin. The protagonists of this exceptional story are photovoltaic cells, the basic components of solar panels. The 3Sun Gigafactory adventure in Catania began in 2010 with thin-film silicon technology: the modules at that time were around 10% efficient and had a lifespan of 25 years – both impressive figures for the time. To bring the newly-opened factory into line with the big foreign manufacturers (particularly those in Asia), we turned to one of the leaders in the industry: Japanese company Sharp, a member of the consortium that led to the launch of 3Sun Gigafactory. Right from the start, we took the Enel Group’s Open Innovation approach: we are open to innovative ideas from outside the company, creating partnerships that help us achieve our common goal of a more sustainable future. We learned fast, and right from the start of production we had a cutting-edge factory: we were ready to look ahead, like true pioneers. The last of seven million thin-film panels left our factory on October 25, 2017. We had decided by then to take a chance on the huge potential of a more innovative model: bifacial panels. They were considered a niche product at the time, and we blazed a trail for them. Other manufacturers soon followed our lead, confirming Enel’s role in setting the direction for the market. Ever the trailblazers Bifacial panels are double-sided to capture the light striking the front of the panel as well as the light that reflects off and is bounced up from the ground to the back of the panel. The main advantage is an increase of up to 20% of the energy generated while occupying the same surface area. In addition, the new models are more resistant to external factors, last longer (up to 30 years) and are built to make recycling of the materials easier. But every goal achieved is also a starting point if you think in terms of continuous innovation. So as far as we were concerned, bifacial panels were a stepping stone to an even more advanced model: bifacial heterojunction technology (HJT) panels, which are 20% more efficient and have a guaranteed lifespan of up to 35 years. In this case, our outstanding partner was CEA-INES (the French Institut National de l’Énergie Solaire), with whom we developed a technology capable of converting more light into energy. Results soon followed. At the start of 2020, our HJT solar cell achieved an efficiency level of 24.63%, a world record. That figure is even more significant if you consider that it was achieved not with an experimental prototype, but rather a cell produced using industrial processes and equipment. To give an idea of just how impressive this is, it is worth noting that silicon cells have a theoretical efficiency limit of around 28%-29%, while the maximum limit achievable in practice is actually 26%-27%. Working in Tandem To overcome these limits, it has been necessary to go back and work on the technological architecture of the cells, moving away from silicon cells to Tandem cells. As the name suggests, Tandem cells are made up of two cells that work together to deliver greater efficiency. We are focusing on a system that uses a perovskite cell as the upper cell and our silicon HJT cell as the lower one. While silicon cells use only radiation from red light, perovskite cells capture blue light. This is how Tandem cells use both components to improve their performance compared to the two individual cells used to make them, resulting in an efficiency boosts of over 30%. Once again, in this instance, we are developing the new Tandem cell in the spirit of “Open Innovation” with input from international companies and research centers of excellence. Thanks to one of these collaborations with Italian partners (ENEA, the CHOSE center at the Tor Vergata University of Rome, Italian National Research Council’s Institute of Structure of Matter [ISM], and BeDimensional, a spin-off company from the Graphene Labs at the Italian Institute of Technology in Genoa), we’ve created a Tandem cell with an efficiency level of 28%, by using our HJT cell as the bottom cell and topping it mechanically with a perovskite cell made in the laboratory. This is a very important result, especially given the fact that the HJT cell used is not a laboratory prototype but a cell produced in our industrial line. This confirms the potential of Tandem technology. We are on the right track and getting closer to moving to industrial scale production. This new step will allow us to make a leap forward in clean energy production and will lead to rapid acceleration in sustainable development. Once again, the milestone we’ve achieved is also, and most importantly, a starting point, and the journey ahead will be just as challenging as the one we’ve just completed.
