Solar collectors versus lamps—a comparison of the energy demand of industrial photochemical processes as exemplified by the production of var epsilon-caprolactam

The energy demand of photochemical synthesis of var epsilon-caprolactam was compared for two plant concepts. The conventional lamp-driven concept followed the process as realized on an industrial scale by Toray Ltd, Japan and a solar concept was designed at identical yearly output. The aim of the comparison was to determine the savings of fossil fuels that could be achieved if photochemistry could make use of solar radiation instead of artificial light. The use of solar radiation for the photochemical production of var epsilon-caprolactam has a 4-fold lower demand for electric current and an 8-fold lower demand for cooling energy as compared to an equivalent conventionally operated route. Furthermore, due to avoided conversion of fossil fuel to electric current, a solar process would allow specific emissions of 1.5–2.5 tons of CO2 per ton var epsilon-caprolactam to be avoided, depending on the primary energy carrier used.