Silicon production technologies: Historical evolution, energy and carbon footprint, and future perspectives

Silicon is the material foundation of two of the most important technological pillars of the modern energy system: photovoltaic electricity generation and the digital infrastructure that manages it. Although the global photovoltaic industry now consumes more polysilicon than the entire microelectronics sector, the energy intensity, carbon footprint and geographical concentration of silicon purification remain rarely examined together in a single framework. This review reconstructs the technological evolution of silicon purification from the early nineteenth-century syntheses of Berzelius and Deville to the hyperscale demand of the 2020 s, with explicit emphasis on the implications for the renewable-energy transition. For each historical era, the specific demand signal, energy-policy instrument or regulatory driver that shaped the dominant purification route is identified. A comparative assessment of the principal manufacturing routes in use today, modified Siemens chemical-vapor deposition, fluidised-bed reactors, upgraded metallurgical-grade silicon and Czochralski/float-zone crystal growth, is then presented in terms of attainable purity, specific energy consumption (kWh kg −1 ), greenhouse-gas intensity (kg CO 2 -eq kg −1 ), water demand and levelized cost. The review presents a forward-looking analysis of how the accelerating deployment of solar photovoltaics, silicon-dominant battery anodes for electric mobility, hyperscale artificial-intelligence infrastructure and renewed space-based programmes are likely to reshape silicon demand, energy use and supply-chain resilience to 2035 and beyond. This review identifies research priorities for reducing the embodied energy and greenhouse-gas intensity of high-purity silicon in a decarbonizing world.