Energy transition combined cycle licensed by Energy Dome

Based on the innovative technology patented by Energy Dome™, the Energy Transition Combined Cycle (ETCC) is a hybrid plant that integrates dispatchable power generation with long-duration and large-scale energy storage capabilities.
An ETCC plant, licensed by Energy Dome is composed by a peaker gas turbine coupled with a CO2-based bottoming cycle, which can be alternatively used to store energy from the grid – when the gas turbine is not running – or to recovery heat from the exhaust of the gas turbine, upgrading its perfomance both in terms of peak load and efficiency.

The ETCC configuration allows the plant to operate in three different modes: Charging, Superboost and Boost .

The CO2 bottoming cycle is an innovative concept that integrates well-proven components: 

  • the Dome is a plastic inflatable membrane where the CO2 is stored at ambient temperature when the battery is ready for charging;
  • CO2 inter-cooled compressors are activated by an electric motor during the charging phase, to take the CO2 from the Dome and compress it;
  • the condenser/evaporator liquifies the CO2 compressed during the charging phase and stored into the vessels with elevated energy density; during the Superboost mode the process is reversed and the CO2 is evaporated before entering the heat exchanger;
  • the CO2 is heated in the heat exchanger recovering the heat in the exhaust of the peaker gas turbine; this allows a very fast start-up of the bottoming cycle;
  • the CO2 turbine is an expander designed by Ansaldo Energia. It uses CO2 as a working fluid, and is connected with the same generator used as electric motor during the charge.

ETTC licensed Energy Domeis also retrofittable: existing Simple cycle facilities can be upgraded as Energy Transition Combined Cycle plants– so achieving efficiency increase, reduction of CO2/kWh emissions, grid support during instabilities and additional revenues from the energy arbitrage. All this while the start-up time remains fast and compliant with the peaker operating mode. 
The ETCC concept has been engineered by Ansaldo Energia with its AE64.3A gas turbine, with outstanding achievements:

  • -100% gas turbine base load in Charging mode;
  • +200% gas turbine base load in Superboost mode;
  • up to 75% efficiency in Superboost mode.


The Ansaldo Energia ETCC is a hybrid solution that supports the grid in three ways:

  • when operated in Charging mode, it helps solve congestion issues during renewable sources’ overproduction hours;
  • when operated in Superboost mode, it allows extra-fast load ramps;

when operated in Boost mode, it plays the role of a dispatchable power generation plant.



When the gas turbine is not running, the CO2-based bottoming cycle can be operated as a storage facility – charged with energy absorbed from the grid, or from a renewable source during its overproduction period. The CO2 is taken from an atmospheric tank, the Dome, compressed and then stored under pressure in liquid state at ambient temperature. This working condition is ideal for storing power when the energy from the grid is available at low cost.



When the gas turbine is running, the exhaust heat is used to heat the CO2 flow discharging the stored energy. The CO2 stored in the vessels during the charging phase is now evaporated and subsequently expanded in a turbine – then returned to the Dome at ambient temperature without any emissions into the atmosphere. This operation mode can achieve efficiency up to 75% and double the peak load of the gas turbine in the open cycle.



Boost mode is always available, regardless of the state of charge of the energy storage. In Boost mode the gas turbine is running and the CO2 cycle is operated as bottoming cycle to recover the heat in the exhaust. This mode increases both peak load and efficiency of the peaker gas turbine without affecting its start-up time. Thanks to the Boost option, the ETCC can be considered a dispatchable power generation plant.

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