Solar energy is growing rapidly, but the path to the required output in terms of climate neutrality only takes technological leaps. How tandem cells help break through efficiency limits and why clever recycling is becoming the key to the raw material cycle.
Solar systems are currently transforming from a niche technology into a central pillar of global energy supply. According to a study, in order to achieve the climate goals, the installed capacity must increase to up to 80 terawatts by 2050.
The background: One terawatt roughly corresponds to the output of 1,000 nuclear power plants. However, the required growth of solar energy is fundamentally transforming the industry’s raw material and supply chains. Researchers have to think about the technology on a square kilometer scale.
Tandem Cells and Recycling: The Next Level of Solar Energy?
Progress has been exponential for decades and follows patterns of the computer industry. The learning rate for improving efficiency is statistically around eight percent after every doubling of installed power.
In addition, the industry already uses ten to 20 percent of global silver production for electrical contacts. Since indium is found as a byproduct primarily in tin ores, the industry also has to extract more tin to achieve higher yields.
But technological concepts could reduce the need for these critical substances. Among them: tandem solar cells, which theoretically perform significantly better than classic modules in terms of material costs and efficiency.
However, almost all solar cells require silicon in an extremely high purity form of 99.9999 percent. For comparison: out of around a million atoms there is probably only one wrong one. The process of producing high-purity silicon requires a lot of energy.
Classic solar modules have limitations
Silicon solar cells dominate the market with around 95 percent, but will soon reach their physical efficiency limit of around 29.4 percent. Tandem technologies, on the other hand, promise to be able to make use of a larger proportion of the solar energy irradiated in the future.
Because higher efficiencies save space, which would increase by 30 percent by the end of the century if there was a lack of innovation. The globally installed module area would then already correspond to half the area of ​​Germany.
However, sustainable expansion must respect the planetary limits. Even in a post-fossil world, miners continue to dig for necessary raw materials as energy production remains mineral.
Recycling solutions such as the extraction of lead from old batteries for new solar cells are therefore essential for a sustainable industry. Researchers are already designing cells for later recycling at the end of their life cycle.
Since solar modules only return to the cycle after 30 years, the industry is dependent on newly mined material in the first round of transformation. But only long-term material cycles ultimately ensure the habitability of the planet.
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