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A parametric study was conducted for the cost reduction of polysilicon by decreasing the electrical energy loss of an existing Siemens reactor. In this work, a quartz ceramic lining was applied onto a reactor vessel, and the hot emitter mechanism was adopted to enhance the energy efficiency for the production of polycrystalline silicon. The effects of the geometrical and heat transfer parameters on the energy efficiency and productivity of the Siemens reactor were examined. Our results indicate that the ceramic lining behaved similarly to thermal insulators by restricting the heat transfer through the ceramic lining, causing the lining surface facing the heated polysilicon rod to emit thermal radiation, thus contributing to reactor’s energy efficiency. The results further demonstrated that the impact of the ceramic lining emissivity on the total radiated heat loss was very small. Furthermore, by addition of a quartz ceramic lining, there is a noteworthy reduction in the total electrical current, resulting in a smoother radial-dependent temperature and thermal stress distribution; thus, a higher deposition radius for the rods can be achieved. According to the energy efficiency analysis, the average energy consumption for the existing 24-rod Siemens reactor can be decreased from 55 kWh per kilograms polysilicon to approximately 36 kWh per kilograms polysilicon.

The Maxwell’s field equations and Ohm’s Law were added to energy equation to account for the electromagnetic contributions to heat transfer phenomena within silicon rod arranged in an industrial Siemens reactor. Based on the combined effect of the heat dissipation (radiation, convection and reaction energy), a Joule heating model using alternating current (AC) has been developed. The analysis accounts for the rod radius, location, skin depth, as well as the properties of the polysilicon. The results indicate that high frequency current sources can generate an even temperature profile, and a higher deposition radius can be obtained. Alternating current, having a fixed or variable high frequency in the range of about 2.4 kHz to 500 kHz, is provided to concentrate at least 70% of the current in an annular region that is the outer 15% of a growing rod due to the skin effect. The voltage-current curves have been predicted based on the present model. Finally, a novel Joule heating method useful for producing the larger high-purity polycrystalline silicon rods by considering the low frequency power and the high frequency power is proposed. It is interesting that the average energy consumption ( AE ) can be decreased from 55 kWh/kg to about 44 kWh/kg as extending the maximum deposition radius from 7 cm to 10 cm by using a high-frequency current source.