Glass melting using concentrated solar thermal energy

Glass melting using concentrated solar thermal radiation is demonstrated on the kilogramme scale using a high flux solar simulator (HFSS). The melting process involved a novel furnace design utilising a downward orientated concentrated solar beam coupled with back-up integrated electrical heating elements, which provided secondary heating to maintain a melt when the HFSS beam was unavailable (i.e. equivalent to cloudy conditions or at night). With 5·26 kW radiative power from the HFSS input to the furnace through a 6 cm diameter aperture, pelleted soda–lime–silica batches were melted. Repeated additions of ∼300 g of batch pellets were made to the melt with each ∼300 g addition requiring ∼15 min for the reactions to complete and the melt temperature to recover. This is equivalent to a glass batch melting thermal efficiency of 16% at a solar concentration ratio of 1857 suns. The areas of land required for the heliostat field and, for the electrical backup elements, photovoltaic field are shown to be significant for even moderate daily glass production tonnages.