Quantification of realistic performance expectations from trigeneration CAES-ORC energy storage system in real operating conditions

Trigeneration compressed air energy storage (TCAES) is one of the emerging solutions that will most likely find its market as a popular energy storage technology for sector coupling. The combination of a TCAES with an organic Rankine cycle (ORC) for waste heat recovery has also been found much effective for enhanced round trip efficiency and is thus to be preferred over conventional TCAES designs. The combined configuration is claimed to offer a very high coefficient of performance (COP) exceeding 1.5. This work aims to quantify realistic performance expectations from a combined TCAES-ORC subject to real operating conditions accompanied for instance by a wind turbine. The system is dynamically modeled, and its performance is analyzed regarding energetic/ exergetic efficiency, environment, and economy. To make the investigations close to real-life conditions, a medium-sized 5 MW capacity TCAES-ORC unit is considered integrated with a wind farm for off-peak electricity utilization for storage and tri-generation of heat, cooling, and electricity when charging or discharging. The location of the use case is considered West Denmark, for which wind power production and pricing profiles are available. The results show that there is a considerable collapse in the cooling and power production when the system comes to low operating loads, while heat production potential is not significantly affected. The COP factor decreases from 1.5 in nominal mode to 1.26 in the off-design mode for a sample dynamic load, where the exergetic efficiency is reduced from 64% to 58%. With such a technical operation degradation, the levelized cost of storage (LCOS) is weakened from 141 euro/MWh to 153.7 euro/MWh, and the potential emission reduction will fall from 4163 to 3640 tonnes of equivalent CO2 per year.

Automated summary

The combination of Trigeneration compressed air energy storage (TCAES) with an organic Rankine cycle (ORC) has been found to be effective in enhancing round trip efficiency, with a high coefficient of performance (COP) exceeding 1.5. However, there is a significant decrease in cooling and power production at low operating loads, while heat production remains relatively unaffected.