55 High medium
storage air y
PT UR CA 2
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Compressed energ
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FU E AT IV
AT ER I
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AL TE RN
Green Wealth
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Global diversity
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G TE AS CH TU NO RB LO INE G Y
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EL S
Low
Local First Fuelled by Carbon
Technology uptake in each scenario
ALTERNATIVE FUELS Fluidized bed combustion and Integrated Gasification Combined Cycle (IGCC) are two interesting future technology options that allow the use of alternative fuels, such as biomass. They also permit wider use of poor quality coal or heavy oil with higher sulphur content, allowing for reduced emissions. For fluidized bed combustion, the conventional GT combustor is replaced by a fluidized bed combustor. Challenges in development are related to corrosion and erosion.
COMPRESSED AIR ENERGY STORAGE (CAES) The IGCC gasification process removes impurities that would otherwise cause corrosion in the turbine and also removes sulphur, which would produce polluting oxides in the flue gases. IGCC has been under development for several decades, and it has been predicted that its efficiency could be increased up to 48 %. IGCC is more complicated and has more components than conventional gas turbines, and therefore reliability is a key challenge.
CO2 CAPTURE The application of CO2 capture and storage (CCS) to Gas Turbine Combined Cycle (GTCC) will probably not occur on a commercial scale before 2020. The indisputable challenge of this technology is the lower energy efficiency due to unfavourable thermodynamics. Adding CCS to a CC plant also considerably increases cycle complexity. The most likely technology option is capture of CO2 after combustion, whereas pre-combustion with hydrogen
turbines or oxy-combustion need more research and are anticipated as being longer-term options. Some R&D on these two latter alternatives is in progress and will continue in the period up to 2020. Although the most promising option up to 2020 and beyond is postcombustion CCS, there are several integration uncertainties that must be addressed, such as flexibility and how it might affect ability to cycle might be affected.
CO2 capture process
Post-combustion CO2 capture process based on Amines. Source: Gassnova
CAES will emerge as a viable alternative to pumped hydro for bulk energy storage. CAES is, essentially, a gas turbine in which the compression and expansion train have been decoupled. The compressor is driven by an electric motor during periods of low electricity cost, and the compressed air is stored in an underground cavern. During high price periods, the air, together with fuel, is released to a combustion chamber, which then drives the expansion turbine. CAES uses less than half the fuel of an open cycle gas turbine, and has a much higher part load efficiency. However, only two CAES plants have been built to date. Further development of turbo-machinery and plant design is necessary to improve efficiency and lower capital costs. Ultimately, the storage of waste heat from the compression cycle could remove the need to burn fuel, thereby reducing CO2 emissions to zero.
Uptake of CO2 capture technologies is policy-driven.
Compressed air Energy storage
A CAES facility is in principle a gas turbine where the compression and expansion train have been deccoupled.