POWER GENERATION
Source: Hydrostor.
Recuperated cycle
The recuperated cycle is the conventional CAES thermal cycle with the addition of a recuperator which recovers the low pressure turbine waste heat to preheat the stored air before it goes to the high pressure combustor. This allows a reduction of fuel consumption by about 25 per cent compared to a conventional cycle plant. This cycle was designed for primary operation as a source of peak power and as a load management storage plant. The main components of a recuperated cycle plant are: • Compressor train with intercooler and aftercooler • High and low pressure expansion turbines • Generator/motor • A fuel/gas combustion system to preheat the released air • Recuperator
Combined cycle
The combined cycle includes the addition of a heat recovery steam generator (HRSG) and a steam turbine. The HRSG recovers the exhaust heat from the low pressure expander to produce steam, which is used to drive a steam turbine and provide extra power. The additional power generated reaches full capacity around one hour after plant start up due to the thermodynamic inertia of the bottoming cycle equipment, therefore making this cycle appropriate for applications that need additional peak power for continuous long-term operations. This cycle has a reduced specific storage volume per kWh produced than the conventional cycle. The main components of a combined cycle plant are: • Compressors with intercooler and aftercooler • Steam turbine • Generator/motor • A fuel/gas combustion system to preheat the released air • Expansion turbine • HRSG • Boiler feed pump • Condenser
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pump industry | Summer 2022 | Issue 38
Steam injection cycle
The steam injection cycle is a conventional CAES cycle that has been adapted to use the HRSG to recover waste heat for steam production. The steam is added to the airflow from the storage cavern to increase mass air flow through the expansion turbine, increasing the plant’s output power level. The mass of air to be stored per unit of power output is greatly reduced due to steam injection with the corresponding reduction of the storage volume and costs. Like combined cycle plants, the additional power from the steam injection lags the power almost instantly produced by the air expansion turbine. The main components of a steam injection cycle plant are: • Compressors with intercooler and aftercooler • Turbines • Generator/motor • A fuel/gas combustion system to preheat the released air • Expansion turbine • HRSG • Boiler feed pump
Compressed air storage with humidification
The compressed air storage with humidification (CASH) cycle involves the stored air being humidified in an air saturator before being injected into the combustion turbine. Due to the humidification, the mass of air needed to be stored per unit of power output is reduced, therefore the storage cavern can be smaller than for other CAES cycle designs. The main components of a CASH cycle plant are: • Compressors with intercooler and aftercooler • Turbines • Generator/motor • A fuel/gas combustion system to preheat the released air • Expansion turbine • HRSG • Boiler feed pump
Adiabatic cycle
Plants using the adiabatic cycle are still conceptual, with major experimental projects and commercial ventures so
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