Test bench for above ground compressed air energy storage systems – pv magazine International

28 October 2024
Lior Kahana

Canadian researchers analyzed the performance of an above-ground compressed air energy storage system (CAES) with both an experimental setup and a numerical model. The quasi-steady-state approach to system modeling was able to predict different parameters of the experimental setup with a mean absolute percentage error (MAPE) of less than 4%.

“This study hypothesizes that the development of a fully equipped test bench and an advanced numerical model that integrates real air properties and takes heat transfer dynamics into account will significantly improve the model ability to represent the real behavior of CAES systems by minimizing errors.” explained. “It is also assumed that this improved model will enable a detailed parametric analysis that will help identify specific opportunities for system improvement.”

CAES can help take advantage of the intermittent nature of solar energy as it can store compressed air when there is excess production and release it when there is shortage. While underground CAES can be used at a grid scale, the aboveground system is more flexible, but research on it is less mature.

“The CAES system works like this: During periods of energy surplus, electricity is used to power the motor that drives the compressor. This compressor then compresses the ambient air into a storage reservoir,” the academics explained. “When there is a demand for electricity, the compressed air in the reservoir is released and directed to a turbine. “The turbine converts the pressure energy of the air into rotational motion, which is then used to drive a generator to produce electricity.”

The experimental setup created by the scientists consisted of a 45 kW compressor, a control unit, an adsorption dryer and 20 reservoirs with a total volume of 5.86 m3. Based on the results obtained from the operation of this system and the reviewed literature, the scientist created a model for predicting the operation of the system using the quasi-steady state approach.

“The quasi-steady-state approach models the transient dynamics of the system by dividing the calculations into smaller intervals characterized by steady-state conditions,” the group explained. “This method allows us to consider changes in environmental conditions over time and provides a dynamic simulation of the response of the system, which is an improvement over the steady-state assumptions used in other studies reviewed.”

The model was further calibrated and a MAPE ranging from 0.21% to 3.58% was obtained across 13 parameters. “With MAPE values ​​consistently below 4.0%, confidence in the model’s capacity to accurately simulate system dynamics emerges, thus establishing a solid basis for subsequent parametric analyses,” the researchers said, noting that the proposed model facilitates deliberate manipulation of parameters. thus allowing a systematic evaluation of round-trip efficiency (RTE).

Based on parametric analysis, the research group found that compressing air at lower temperatures reduces the compressor’s workload and extends charging time, leading to a 1% increase in RTE. They also found that decreasing the polytropic index towards an isothermal process resulted in a 7.5% increase in RTE with preheating. Finally, the team also found that “increasing the number of expansion stages from one to three significantly improved the RTE from 5.5% to 16%.”

The results were presented as follows:Aboveground compressed air energy storage systems: Experimental and numerical approachpublished in Energy Conversion and Management. The research was conducted by a Canadian organization. Ecole de technologie supérieure (ÉTS) and the Hydro-Québec Research Institute (IREQ).

Popular content