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A Chinese research group has combined compressed CO2 with cogeneration units to store renewable energy.
Researchers at the Southeast University of China have studied the possibility of coupling compressed carbon dioxide (CO2) to a cogeneration unit to store solar and renewable energy.
The proposed solution is a closed-loop system with a 600 MW cogeneration unit and a carbon dioxide energy storage (CCES) facility. It uses the heat from the backwater of the heat network and works through two stages of compression and expansion using water and carbon dioxide as working fluids, without exchanging mass with the external environment.
“During off-peak periods, the s-CO2 released from the low-pressure tank (LPT) is compressed in the compressor driven by the excess generation capacity of the CHP,” the scientists explain.
The compressed CO2 is then passed through an intercooler to store the heat of compression in the water leaving the cold water tank (CWT).
“After the two stages of compression, the s-CO2 is stored in the high pressure tank (HPT), and the cooling water is pressurized by the pump to be stored in the hot water tank (HWT),” they said. the scientists. “Cooling water from the upgraded system absorbs additional heat from the mid-extraction steam before entering the HWT.”
During peak periods, the HPT releases sCO2, which is transported through the superboiler to recover heat from the HWT. It then goes to the turbine to generate electricity. The sCO2 is then stored in the LPT, passing through the heat exchanger, while the water returns to the CWT.
The Chinese group used thermodynamic modeling to perform a thermodynamic and parametric analysis of the system and found that a system configuration adopting an uneven distribution of compression and expansion ratio gave the best system performance. According to the researchers, the best system configuration achieved a total exergetic efficiency (TEE) of 35.96% and an energy storage density (ESD) of 1.54 kWh/m3.
The scientists presented the system in “ Thermodynamic analysis and optimization of a compressed carbon dioxide energy storage system coupled with a combined heating and power unit. ” heating and electricity), recently published in Energy Conversion and Management .
“The performance and thermoelectric coupling characteristics of the proposed combined system under variable operating conditions need to be analyzed in the future to investigate its ability to consume renewable energy,” they noted. |
