#7: The Silver Lining in a Terawatt Sustainable PV Market

In this issue we speak to Marwan Dhamrin who is also a professor at the Osaka University Graduate School of
Engineering. He waxes lyrical about a very important element in our PV industry, the precious Silver.

Hello Marwan! Could you tell us briefly about your company, Toyo Aluminium K.K., and the role it plays in the PV
industry?

Besides offering a wide range of products from aluminium powders to foils and automobile pastes, Toyo Aluminium K.K. is one of the pioneer Japanese companies in PV. Since the 80s, Toyo has been providing aluminium pastes and high quality backsheets to Japanese solar makers. We are expanding our product portfolio to low temperature pastes with Cu, Al, SiO2. core particles to decrease the heavy demand on Silver.

Lately silver has become a hot topic within the PV industry. Could you shed some light on how much silver is being
consumed by the PV industry recently?

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Over the last few years photovoltaics has become the leading renewable energy source. According to the World Silver Survey 2021 report, the PV market used 11% (2818 tons) of the total silver produced worldwide, a 1% increase from 2019 despite COVID disruptions which impacted other sectors. The PV market proved its resilience with added capacities exceeding 135GW according to the ITRPV 2021 report which also gave a rather conservative estimation of silver consumption of about 5.7% based on 12.6 t/GWp (1705 tons).

And how is this use of silver going to be a problem for the future development of PV? For Mono PERC? For N-type cell technologies?

Passivated Emitter Rear Cell (PERC) is currently the mainstream solar cell technology which uses front Ag paste with solid contents exceeding 90%. While the rear side is metalized mainly with aluminum, relatively lower solid contents of less than 60% Ag paste is printed in small pads for soldering process at the rear side of the cell (5-10mg/M6 wafer). The front side with best printability todate might consume 0.29 to 0.35 mg/cm2 (approximately 80-100mg/M6 wafer).

If the PV market reaches Terawatt production capacity with PERC and even with reducing the Ag consumption by printing narrow fingers, 0.18 mg/cm2 or 50mg/M6 wafer, and improving the conversion efficiency to 23.5%, one can estimate a demand of silver in the range of 7500-8000t/TW or 3 to 4 folds of the current consumption level.
 

However, we believe that most of the new solar cell production expansions will be based on technologies such as passivated contacts and heterojunction silicon solar cells which in comparison uses double side silver metallization, increasing the consumption per cell to at least 0.36 mg/cm2. Even with the assumption that these new technologies can deliver 26% conversion efficiency, the total demand of silver when reaching terawatt level will surpass 13700t/TW.
 

What solutions are being crafted to address this impending shortage of silver and the ensuing price hike?
 

Thinking about suitability energy production, we must find other alternatives to Ag metallization. At Toyo Aluminium K.K., we introduced new low-cost aluminium paste technologies capable of contacting both polarities of the passivated contact solar cells as high temperature alternative in addition to a lineup of low temperature metallization pastes based on low-cost fillers such as Ag-coated Cu, Al, SiO2 core particles to reduce the total cost and dependency on silver metallization for advanced solar cells allowing sustainable PV market in the years to come.

Thank you for sharing on this pressing issue in the PV industry. Which international conference or trade fair are you planning to attend in the near future?

The Silicon PV conference in Germany and SNEC in China will be top of the agenda in 2022. After that, Intersolar Europe and similar events in the Middle East as PV is quite the hot topic there.

Finally, as you have been living in Japan for more than 10 years, could you share your secret-small-town-destination-that-no-TripAdvisor-has-reviewed-yet, for our audience to visit when borders reopen in Japan?

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I would suggest Omihachiman, a relatively small town between Kyoto and Nagoya, with great scenery of traditional houses in the old town, best coffee shops across the Biwako Lake and best beef restaurants. Also, for anyone in the PV industry, they might be able to visit PV makers near the town, within 20 minutes’ drive, such as Toyo or Kyocera.