1366 Technologies CEO Frank van Mierlo is a betting man and heâ€™s betting your humble narrator that high-efficiency tandem solar cells are the near-term commercial future of solar.
November 5, 2020
Frank van Mierlo, the CEO of 1366 Technologies, is a betting man â€” and heâ€™s wagering that â€śthe solar market will see 2 GW of tandem solar in the marketplace by the end of 2022.â€ť
I am the skeptic on the other side of this wager for one bottle of fine champagne â€” although I would accept a thimbleful of the CEOâ€™s tears in its place.
van Mierlo, chief of a kerfless silicon wafer startup, has said: â€śIâ€™ve never doubted silicon. We really believed in it. The learning curve had been holding steady for 45 years â€“ itâ€™s a pretty predicable line. Why would that stop?â€ť
So, when we heard van Mierlo at a recent talk saying that tandem modules made from a high-bandgap and a low-bandgap material are â€śthe most important innovation in solar since solar was first conceived in Bell Labs in 1954,â€ť it seemed that 1366 was pivoting to a new technology and approach.
When I asked van Mierlo about this seeming shift to tandem, and voiced my concern with this technology path, the CEO suggested we embark on a small wager about tandemâ€™s commercial future.
He believes that the solar market will see 2 GW of tandem solar in the marketplace by the end of 2022.
van Mierlo writes, â€śIn fact, not only do I believe that multiple gigawatts of tandem will be sold before the end of 2022, I am also confident that in a decadeâ€™s time, tandem will command more than 50% of our industryâ€™s market share.â€ť
He continues: â€śIs it that I no longer believe in the long-term role of silicon?â€ť
â€śNo! In fact, itâ€™s the remarkable success of silicon that now makes tandem modules the inevitable next step. With its low bandgap of 1.1 eV and its low cost, silicon is the ideal candidate for the bottom cell in a tandem configuration. In this position, a silicon bottom cell converts less than one-third the energy captured by the sun but still carries 100% of the cell cost. To make tandem work, you need the bottom cell to be extremely low cost. And, thanks to recent innovations such as the Direct Wafer furnace, we can achieve that cost target.
â€śIt is precisely because of siliconâ€™s dramatic learning curve that tandem will soon be a commercial reality. As module costs have declined and many installation costs remain fixed, weâ€™ve witnessed the increased pressure for greater efficiency. This pressure will drive tandem adoption: its dramatic efficiency boost without a significant increase in module cost-per-watt will lower the installed cost of solar by producing more power for a given area.
â€śWe know that the headroom for increasing efficiency with single-junction silicon technology is closing. It is the opportune moment for tandem modules underpinned by extremely low-cost silicon.
â€śWhich brings us to the tandem top cell, for which there are many excellent solutions. Thanks to the massive investment in thin film R&D, there are suitable materials already on the shelf. Moreover, new perovskites bring additional promise. Oxford PV and Swift Solar both vouch that it is possible to make a stable high-bandgap perovskite, but it is much harder for perovskites to match the excellent low-bandgap performance of silicon.
â€śSiliconâ€™s next contribution will be to tandem as an extremely low-cost and high-performing bottom cell.â€ť
â€śI am looking forward to drinking that champagne,â€ť taunted the CEO.
Since its founding, 1366â€™s technology has been based on forming solar wafers directly, using molten silicon, instead of silicon ingots sawn into wafers. Over the last 14 years, 1366 has raised more than $100 million from investors including Breakthrough Energy Ventures, Tokuyama, North Bridge, Polaris, VantagePoint, Energy Technology Ventures, Hanwha Chemical, Ventizz Capital and Haiyin Capital.
Tandem structures can be epitaxially grown monolithically on silicon or mechanically stacked. The tandem-junction cell architectures have potential efficiency gains because of the different wavelength ranges and bandgaps of silicon and other materials.
Tandem solar startups include:
As weâ€™ve reported, commercial crystalline silicon is forecast to reach efficiencies of 22%-24% by the end of the decade, and possibly 25% if interdigitated back-contact (IBC) heterojunction products get to market.
NREL studies find that reaching cost reductions in photovoltaics beyond the 6Â˘/kWh SunShot 2020 goal will mean that cell efficiency must be increased beyond the Shockleyâ€“Queisser limit of 29.4% for a single p-n junction. Other researchers have found that PV modules made with tandem solar cells will have to show efficiencies of 30% and offer the same lifetime and degradation rate as standard crystalline panels if manufacturers want to hit commercial production.
That said, I win this bet because:
I will toast your health with my victory champagne in Dec 2022.
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