Fluidized Bed Reactor Technology Claims A Place In Solar Polysilicon Manufacturing


Despite challenges related to purity and efficiency, low-cost fluidized bed reactor (FBR) manufacturing technology is expected to make significant gains in the market for solar polysilicon during the next few years, according to a new report from IHS Technology.

This year, the FBR process will account for nearly 10% of the production of global photovoltaic polysilicon, which represents the first step in PV module manufacturing leading to the creation of solar panels. However, the IHS report says the next few years will see FBR gradually take share away from the Siemens process technology that now dominates the market.

By 2020, FBR will account for 16.7% of the market, compared to 77.9% for the Siemens process, with the remaining 5.4% of the market represented by upgraded metallurgical grade (UMG), the report forecasts.

‘The PV market is optimistic about demand in the foreseeable future, and starting with polysilicon production, major manufacturers are increasing capital spending and expanding production operations to position themselves to capitalize on the growth,’ says Jon-Frederick Campos, analyst for solar research at IHS.Â

To this end, polysilicon producer REC Silicon recently announced a 19,000-metric-ton expansion in capacity, of which 18,000 MT will utilize FBR technology, along with 1,000 MT of Siemens-based capacity.

Chinese-based GCL-Poly and SunEdison have also gone on record to announce that they are also building polysilicon plants using FBR technology.

‘FBR takes less energy, shortens crucible fill times and produces more silicon per cubic meter of reactor space, as the crystals have a larger total surface area than the rods used in the Siemens process,’ Campos says. ‘FBR presents many benefits of high interest for polysilicon producers, with advocates for the technology saying that FBR can produce output at a cash cost of $10 per kilogram in the foreseeable future – a sizable decrease in cost versus the $14 per kilogram promised by its best-in-class Siemens counterparts.’Â

However, IHS points out two fundamental inhibitors to the promise of FBR.

First, there are questions on whether the technology can reach the industry demand for silicon purity close to electronic-grade level, given costs of less than $10 per kilogram.

A second concern relates to scalability. The deposition in a fluidized bed reactor is not easy to control as dynamics change with size, and reactors cannot simply be scaled up from pilot to industrial scale, IHS says.

FBR is a third-generation solar technology that is able to effectively control granules that might cause pollution during the purification process. In FBR, monosilane is injected into the bottom of the reactor to form a fluidized bed that carries silicon seed particles fed from above. Silicon deposits from the monosilane on the seed particles until they have grown to larger granules, which can then be withdrawn from the reactor continuously.

Contrary to a batch process, fewer resources are wasted in FBR, and less setup and downtime is required. FBR needs only 10% of the electricity consumed by a conventional rod reactor in the established Siemens process, as it does not waste energy by placing heated gas and silicon in contact with cold surfaces.

According to IHS, it will be a challenge for FBR to make a stronger business case than the Siemens process – even if cost is important to polysilicon manufacturers. This is because the purity of silicon is becoming a larger factor in the improvement of PV energy outputs.

‘Cell manufacturers are requiring higher-quality polysilicon to meet their efficiency road maps,’ Campos says. ‘The lower material costs and potential for improved margins presented by FBR along with other polysilicon technologies are overshadowed by industry standards having shifted toward higher-purity polysilicon – namely 9N and above – because higher-purity polysilicon can boost solar cell efficiencies.’

The Siemens technology is capable of meeting these needs by producing polysilicon at purity levels at or above 9N to 11N, Campos says. In comparison, FBR outputs at 6N to 9N, while UMG produces at approximately 5N to 6N.

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