In a recent paper published in Solar Energy, researchers said they collected data from a solar cell factory to develop and evaluate water recycling strategies in the manufacture of solar Passivated Emitter and Rear Cells (PERC).

A team of researchers from Fraunhofer Institute for Solar Energy Systems ISE, Technische Universität Berlin, RENA Technologies, and the University of Freiburg have, for the first time, developed a comprehensive water model of a solar cell factory to reduce water consumption and minimize wastewater production.

Given that water use, and wastewater discharge are particularly relevant for the sustainable and reliable production of silicon-based solar cells, the team acknowledged how periods of droughts or reduced water availability can compromise the operation of water and energy-intensive industrial processes.

The research work was started by setting up a specific material flow analysis and a total cost of ownership for manufacturing PERC solar cells with a factory capacity of 5 GW. Facilities and wastewater treatment requirements were included. The factory is located in Germany.

After setting up the reference material flow analysis and total cost of ownership, circular water and resources strategies were identified and proposed as scenarios. The technical and economic feasibility of the strategies and their environmental performance were then evaluated by employing wastewater treatment simulations, cost-benefit analysis, and a life cycle assessment.

The team investigated two circular strategies in the current state of PV cell manufacturing – low contaminated wastewater and minimal liquid discharge.

With low contaminated wastewater, the focus was on the reclamation of rinsing waters with low salt concentration while still being able to discharge the combined wastewater indirectly. In the minimal liquid discharge approach, the researchers focused on reducing the amount of wastewater leaving the factory as much as possible while identifying and retrieving possible valuables from the wastewater.

They found that for 38% and 79% of the water consumption scenarios, 40% and 84% of the wastewater indirect discharge at the cell factory can be saved by the low contaminated wastewater and minimal liquid discharge approaches, respectively. The environmental impact single score of the cells’ production decreased by 0.4% when applying the low contaminated wastewater strategy and 3.2% with minimal liquid discharge.

The minimal liquid discharge strategy proved more effective, achieving a 79% reduction in water use and an 84% reduction in wastewater production. This strategy focused on minimizing liquid waste output from the factory, utilizing advanced treatment processes to recover and recycle water and other valuable byproducts from wastewater.

Despite this, the researchers found the minimal liquid discharge approach to be capital intensive due to high operational costs caused by the energy requirements of advanced wastewater treatment technologies like evaporation and crystallization.

The implementation of the low contaminated wastewater strategy offers economic and ecological advantages for the production of PERC solar cells. The team gained 38% of the water and 40% of the wastewater discharge from the reference cell factory requirements through low contaminated wastewater.

The research holds promise in regions with high water scarcity and where stringent environmental regulations pose challenges to industrial operations.

PERC cell technology is widely used in the industry. Therefore, a wide application of the results of this work is also likely in facilities producing higher efficiency cell technologies like TOPCon (tunnel oxide passivated contact) and HJT (heterojunction) since many of the studied wastewater streams analyzed are similar.

At a webinar hosted by Mercom, experts discussed the dominance of Mono PERC modules over bifacial and other technologies because of their price advantage.