Thursday, 27 April 2017
DLR solar researchers together with European research partners develop a novel process for CO2 free power generation based on the combustion of sulphur allowing to store solar energy in the form of sulphur. For this purpose, a CSP concentrating solar power tower plant with particle receiver technology is integrated in a sulphur cycle. The demonstration operation is planned for the last year of the project at the Juelich Solar Power Tower of DLR.
Sulphur (S) is one of the most important raw materials of the chemical industry, which is required for the production of sulphuric acid (H2SO4), one of the most important and most produced basic chemicals. Worldwide, more than 100 million tons of sulphuric acid are produced from sulphur every year. Therefore, the handling of sulphur, sulphuric acid and its decomposition products are industrial standard procedures. If solar thermal power plants can be efficiently combined with conventional sulphuric acid production plants, then sulphur could become an important storage material for solar energy in the future.
Sulphur can permanently store solar energy with low energy losses and 30 times higher energy density as conventional molten salt storage systems. The long-term storage of solar energy is an important prerequisite to completely replace fossil power plants with renewable energy sources. Furthermore, sulphur can be easily transported as solid or liquid by ship, train or truck.
Sulphur storage cycle: no energy gets lost
Sulphur can be used in flexible power plants instead of natural gas to generate on-demand electricity. Sulphur dioxide (SO2) is produced from the combustion of sulphur. In the sulphur cycle – proposed by the American company General Atomics – the SO2 is mixed with water and transformed into fresh sulphur and diluted sulfuric acid in an innovative disproportionation reactor. The storage of these products is a standard procedure in chemical industry: sulphur is simply collected on a pile and sulphuric acid is stored in suitable tanks. In a thermal splitting reactor the sulphuric acid can be converted to additional sulphur dioxide. The innovation of the project PEGASUS is the combination of the solar particle receiver developed at DLR with a sulfuric acid decomposition reactor.
When the sun is shining the sulphur storage is filled while the sulphuric acid tank is emptied. During cloud passage or at night time, sulphur is taken from the storage while the sulfuric acid tank is filled. Power generation with sulphur combustion can be continuously operated in 24/7 service. In summary, renewable baseload power is generated at constant production rate while sulphuric acid and sulphur are used as energy carriers and recycled virtually lossless.
What makes this technology particularly attractive:
Pilot operation planned at the Juelich Solar Power Tower
In the framework of the project, the solar centrifugal receiver developed by DLR with its integrated thermal storage concept will be combined with a newly developed moving bed particle reactor for sulphuric acid decomposition. The demonstration of this pilot plant is planned for the last year of the project at the DLR large-scale facility Juelich Solar Power Tower. The project PEGASUS is co-funded by the Horizon 2020 Framework Programme of the European Union with a total of 4.7 million Euros. The DLR Institute of solar research is coordinator of the project. Other project partners are the Greek research Institute APTL/CERTH (development of catalyst materials), the German research university KIT (development of combustion technology), the Polish company Baltic Ceramics (manufacture of advanced ceramic particles), the Italian company Processi Innovativi (Power plant designer/contractor) and Israeli company BrightSource (designer/contractor of solar thermal CSP plants).