Steam Turbines
The process is simple:
In a steam turbine, regardless of the heat source, the typical fluid used is high-pressure and high-temperature steam produced outside the turbine is transformed into mechanical energy. This mechanical energy is further converted into electricity through a generator. After passing the steam turbine, the lower temperature and pressure steam is cooled down in a condenser and the resulting water used again for the generation of new steam.
Its main components:
- Rotor: This part extracts energy from the steam using an impeller with mounted blades and transfers it to the shaft.
- Turbine blades: These blades, either stationary or moving, are connected to the rotor shaft or the casing. Steam passing through them turns the blades, which then drives a generator to produce electrical energy.
- Casing: Its role is to disperse the steam and maintain proper sealing within the turbine system.
The power generation operation:
Once the steam is generated, it is used to propel the steam turbine.
Main configurations:
Turbine manufacturers continuously innovate, exploring new working fluids to enhance technology’s range and maximise heat utilisation.
Depending on site conditions, power range, and heat parameters, various cycles can be considered to optimise performance.
- Rankine Cycles: employ water steam as working fluid, typical for steam turbine-based systems with temperatures exceeding 300°C.
- Organic Rankine Cycles (ORC): utilise organic liquids with lower boiling points as working fluid, enabling the use of low-temperature heat (down to 150°C), like industrial waste or geothermal heat.
- Supercritical CO2 cycles: employ CO2 in a supercritical state (i.e. in fluid form), offering a temperature range like steam (225°C to 650°C), but with superior performance and efficient utilisation of high-temperature heat, such as industrial waste or concentrated solar heat.
Combined Cycle Power Plants – The combination for increased energy efficiency
To achieve optimal efficiency, gas and steam turbines can be integrated in a Combined Cycle Power Plant (CCGT).
Here’s how it works:
- The gas turbine generates electricity similar to an open cycle gas turbine.
- The waste heat from the gas turbine is captured and in a Heat Recovery Steam Generator heats up water to generate steam like in a boiler.
- The steam drives a steam turbine, generating additional electricity.
- Both turbines can be connected to separate generators or combined on a “single shaft” linked to one generator.
- Steam is reused in a closed cycle, enhancing efficiency.
All in all, steam turbine technologies offer unique capabilities crucial for the future EU energy system. With their operational and fuel flexibility, they are future proof and well-equipped to support the transition to a decarbonised energy system and economy.
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