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Photovoltaic supply falls short of solar power targets

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The study looks at four main PV technologies: crystalline silicon (c-Si), amorphous silicon (a-Si), cadmium tellurium (CdTe) and copper indium gallium diselenide (CIGS).

Brussels — Europe could struggle to meet the target set by the renewable energy sector of 25 percent of electricity produced by solar energy by 2040 because the supply of materials, including rare metals, needed to produce photovoltaics (PV) is unlikely to meet demand. Production rates need to be drastically improved, according to a new study. Calculations based on available appropriate land, global irradiance and conversions of solar energy to electricity demonstrate that technically, solar energy could provide 7.5 to 9 times the expected electricity demand in 2050. However, several PV technologies employ rare metals, which could limit the capacity for electricity generation.

The new study looked at whether current global production of rare metals could support the huge increase in solar panels generation required to meet ambitious energy targets for 2040 laid out by the European Renewable Energy Council. The scientists looked at the four main PV technologies: crystalline silicon (c-Si), amorphous silicon (a-Si), cadmium tellurium (CdTe) and copper indium gallium diselenide (CIGS).

CIGS demand outstrips current supply

The scientists assumed that by 2040, each technology would have an equal market share of 25 percent. This reflects the fact that although c-Si currently has the largest share (81 percent), a shift is already taking place towards the other technologies, which require a thinner layer of PV material. They simulated a ‘neutral’ future scenario, where moderate technological developments gradually improve the efficiency of electricity generation, in line with current policy expectations. The results showed that the maximum demand for gallium and indium in tonnes per year for use in CIGS technology surpasses current production (2008) by a factor of 7.3 and 2.8, respectively. Even under an ‘optimistic’ future scenario, in which more ambitious technological advances in cell efficiency require less PV material, demand still outstrips current supply by a factor of 3.9 and 1.5, respectively.

Neither cadmium nor copper were found to be seriously limiting, even when the scientists simulated a ‘pessimistic’ scenario in which technological advances do not meet current expectations. However, the predicted demand for tellurium was found to be 30-180 times higher than today’s production rate, depending on the scenario used.

Bigger shortages may result

Although silicon is the second most abundant element in the earth’s crust, only very high purity silicon is used in the solar industry and production will need to increase by 15 times to meet demand in the neutral scenario and by 10 times in the optimistic scenario. Even bigger shortages may result from competition with the electronics industry, which also uses high-purity silicon. On the other hand, amorphous silicon technology represents the only realistic option for large-scale electricity production since the cumulative demand by 2040 would equal just 20 percent of production.

Better refining techniques needed

The research shows that reaching solar power targets for 2040 will not necessarily be limited by known global reserves of silicon and rare metals, but that current production rates will be the limiting factor. Better refining techniques, increased exploitation of deposits and strategic planning of technological shifts are needed to satisfy the demand for PV materials. This poses a challenge as tellurium, indium, gallium, selenium and cadmium are by-products of other processes and are not currently mined separately. New production methods are also likely to take up to 10 years to develop and so research should be initiated soon to meet the anticipated demand.

As the growth rate of new installations decreases, recycling PV material could drastically reduce the need for new materials. While nanomaterial technologies that increase cell efficiency even further are currently in development, they are not expected to be widely used by 2040, so they are not included in these scenarios and projections.

Source: Zuser, A. & Rechberger, H. (2011). Considerations of resource availability in technology development strategies: The case of photovoltaics. Resources, Conservation and Recycling. 56: 56-65.

Source: European Commission DG

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