Scientists in China have simulated an advanced adiabatic compressed air energy storage, to which they have added an elastic airbag with a heavy load above it. The energy, exergy and economic analysis of the system showed that the pressure level of the airbag is not attacked during the operation due to the constant weight of the heavy load.
A research group of Chinese Northeast Electric Power University has presented a new advanced adiabatic compressed Air Energy Storage (AA -CAES) system.
The proposed system uses a heavy load, an elastic airbag and an abandoned vertical mine shaft, so that the AA cheeses are transformed into an isobary system with gravity, where the pressure remains constant.
“By designing a new Isobaric Air Storage reservoir, the ISOBARIC Operation system reaches,” the researchers explained. “An abandoned vertical mineas is used as the air storage reservoir to maximize the land use. Moreover, the discharge phase can be completely deported after completion of the discharge phase, which improves the energy storage density.”
The system was simulated using MatLab software for energy, exergy and economic analysis. It uses surplus power of PV, wind or grid to drive a compressor. This in turn changes to the environment atmosphere into high -pressure air, which is then stored in an air storage reservoir (ASR). The process includes five stages of sequential compression to reduce energy consumption, accompanied by five intercoolers who capture the heat that is generated during compression. The ASR includes a deserted vertical mine shaft, a heavy load and an elastic airbag.
The elastic airbag was placed at the bottom of the mine shaft, while the heavy load was installed above the airbag. During the loading phase, the V1 valve opens and closes the V2 valve, where the high pressure air enters the airbag, which increases the volume of the airbag and the height of the airbag. Due to the constant weight of the heavy load and the constant contact surface between the heavy load and airbag, the pressure level of the airbag remains unchanged during the charging processing, which reaches an isobary air loading process.
Image: Northast Electric Power University, Case Studies in Thermal Engineering, CC by 4.0
“After completion of the charging procedure and reaching the intended peak volume, the airbag is fully charged, so that the fulfillment of the designed maximum capacity symbolizes. During the discharge phase, the valve V2 is opened and the aforementioned valve V1 from the aforementioned minimum of airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is discharged and the airbag is unloaded and the airbag is unloaded and the airbag. is, “the scientists explained.
The simulations were based on an ambient temperature of 25 ° C and an environmental pressure of 0.1 MPA. The density of the heavy load was set at 7,870 kg/m3, with the compressor consuming 5,880.82 kW. The prices for the system were based on the Chemical Engineering Plant Cost Index (CEPCI): Price of electricity for the discharge period was $ 0.18/ kWh, the price of heavy load was $ 0.1/ kg, price of hot water $ 0.018/ kWh, and the price of electricity was $ 0.04/. The system was supposed to work 350 days a year with a lifespan of 25 years.
The analysis showed that the Energy Efficiency was 87.1%, the exergy efficiency was 70.07%, the storage density of the air energy was 2.68 kWh/m³ and the occupied space on the energy storage of the room was calculated as 2.29 kWh/m³. The turbine and compressor experiences the largest exergy losses, good for 35.21% and 30.98% of the total exergy losses of the system respectively; While the intercooler and intermediate laws have a lower exergy efficiency with the lowest 63.54% and 50.60% respectively.
In addition, the results of the economic analysis revealed a level of energy costs (LCOE) of $ 0.0804/kWh. The net present value (NPV) was calculated at $ 1.6 million, with an internal return (IRR) of 17.93% and a dynamic payback time (DPP) of 8.36 years. The results have appeared in “3rd analysis and multi-objective optimization of a new isobarically compressed storage system for air energy with a gravity-reinforced air storage reservoir“Published in Case studies in thermal engineering.
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