The SULPHURREAL project demonstrates an innovative approach to the direct storage of concentrated solar energy in solid elemental sulphur. The basic idea is to use concentrated solar energy to cyclically drive a series of chemical reactions that interconvert sulphuric acid and sulphur. The cycle can also be operated using sulphuric acid and sulphur feedstocks from existing large-scale industrial processes.  

Sulphuric acid (H2SO4) is first evaporated and then sequentially decomposed into sulphur dioxide and oxygen using heat from a concentrated solar irradiation source. The sulphur dioxide then reacts with water to produce sulphuric acid and elemental sulphur. The sulphur stores a significant proportion of the solar energy that was used to decompose the sulphuric acid. It can be combusted on demand to release this stored solar energy.  

All intermediate products such as sulphur dioxide and sulphur trioxide are recirculated internally without being emitted into the atmosphere.