Off-design performance and operation strategy of expansion process in compressed air energy systems

Significance 

As a way of reducing environmental pollution and emission of greenhouse gases as well as enhancing sustainability, development of alternative renewable energy sources have been encouraged to reduce the overdependence on fossil fuels. This has led to the development of several renewable energy sources such as solar and wind energy. Interestingly, storage of the generated renewable energy has, however, remained the biggest challenge in the sector due to unreliable storage technologies. Therefore, the development of more efficient energy storage technologies is highly desirable.

Among the available energy storage techniques, compressed air energy storage that operates under off-design conditions is generally durable, cost-effective and flexible and thus a promising storage facility. Recent studies have shown that environmental conditions like pressure and ambient temperature can consequently result in the off-design operation of the system. Alternatively, in order to optimize the energy storage of the compressed air systems, a lot of emphasizing has been on the effects of the dynamic characteristics. Unfortunately, the effects of the performance of the components constituting the off-design systems as well as the optimizing system regulation methods have not been fully explored to date.

To this note, Chinse Academy of Sciences researchers led by Professor Haisheng Chen from the Institute of Engineering Thermophysics recently investigated the multistage expansion process involved in thermal storage-based compressed air energy storage systems. In particular, off-design performance and characteristics, as well as the optimization methods, were further explored. The work is currently published in the research journal, International Journal of Energy Research.

In brief, the research team commenced their experimental work (Fig.1) by first exploring the off-design performance of the compressed air energy storage systems. Next, an off-design model based on the multi-stage expansion of the thermal-based compressed air energy storage system was developed. Fundamentally, two main operation models, equal power ratio and optimizing variable stator vane rotation angle, were utilized. The operation of the systems under the two aforementioned conditions were analyzed and compared. Eventually, the relationship between some of the parameters including inlet pressure mass flow rate ratio and was examined.

The author observed that the thermal storage temperature and the mass flow rate ratio linearly increased with the output power ratios. This was for a particular inlet pressure for both the equal power ratio and variable inlet guide vanes operating modes. However, at larger mass flow ratios, optimizing variable stator vane rotation angle operation exhibited a significant increase in energy efficiency as compared with the equal power ratio mode. Consequently, at larger mass flow ratios, optimizing variable stator vane rotation angle operation mode exhibited remarkable variation in the expansion ratio with opposite changing trends. In addition, for variable stator vanes, a stronger linear relationship was noted between the rotation angle and the mass flow rate for a given inlet pressure.

In summary, for the first time Huan Guo and colleagues successfully presented the off-design performance and optimization strategies using two operation modes. The various relationships were obtained through a polynomial fitting form. In general, the study will advance renewable energy storage technologies for sustainability.

Off-design performance and operation strategy of expansion process in compressed air energy systems - Advances in Engineering
Fig.1 Four-stages Expander in the World’s First 10MW Advanced CAES Plant

About the author

Professor Haisheng CHEN, BEng, PhD, is currently the deputy director of Institute of Engineering Thermophysics (IET), Chinese Academy of Sciences (CAS). He joined IET-CAS in 2009 as a “100-Talents” professor after previous employments at University of Leeds, IET-CAS, Vrije University of Brussels and Beihang University. He is also the director of China National Research Centre of Physical Energy Storage.

He has been working on fluid dynamics, heat transfer and system analysis related to energy storage and power engineering. More specifically, his research includes compressed air energy storage, thermal energy storage, internal flow of turbomachinery. He has been involved with 50+ research projects with 30+ of which being the principal investigator. His research has led to 300+ papers, 13 book chapters and 160+ patents. The publications have received 5000+ citations according to the Thomson ISI Web of Science Database (SCI). He also acts as committee member/session chair of 8 international conferences and editorial board member for 7 peer reviewed journals. He is currently the deputy editor-in-chief of 3 peer reviewed Journals and president of China Energy Storage Alliance.

Contact: [email protected]

About the author

Dr. Huan Guo is an associate professor at Institute of Engineering Thermophysics, Chinese Academy of Sciences (CAS). He studied in Graduate University of Chinese Academy of Sciences majoring in Engineering Thermophysics, and obtained his PhD degree in 2016.

His research interest includes thermodynamic analysis and optimization methodology of energy system, novel compressed air energy storage technology, dynamic modelling and analysis of energy storage system as well as the utilization of renewable energy.

He leads a National Natural Science Foundation of China (NSFC) program as a principle investigator at present. He also participated in more than 10 research projects including CAS projects, sub-project of 863 project, 973 project of China. He has 18 papers published in the international journals including Energy, Applied energy, and Energy Conversion and Management, etc.

Contact: [email protected]

Reference

Guo, H., Xu, Y., Zhang, Y., Guo, C., Sun, J., Zhang, X., Li, W., & Chen, H. (2019). Off-design performance and operation strategy of expansion process in compressed air energy systemsInternational Journal of Energy Research43(1), 475-490.

Go To International Journal of Energy Research

Check Also

Effects of Slag Layer on the Multiphase Interaction in a Converter