Abstract:

The problem of decentralized energy storage is of crucial importance for the development of renewable energy resources. In the first stage of their development, RES have relied on the possibility of connecting to the grid. However, with increased RES share, pressure is being put on the electrical grid system, resulting in the necessity of extensive load modulation of traditional plants (hydroelectric and fossil), and also on the development of large energy storage facilities (hydro-pumped, CAES, batteries,…). From the point of view of distributed energy systems, connected to smart grids, it is rather interesting to develop local energy storage systems, which can help to decrease the load on the grid infrastructure, possibly paving the way to complete off-grid operation. The case study is a Small-Size Advanced Adiabatic Compressed Air Energy Storage (SS-AA-CAES), developed from existing components (compressors, heat exchangers, vessels, expander,…) and coupled to a local PV field. The system operates trying to separate pressure energy and heat, and promoting regenerative/recuperative use of this last with low-temperature thermal storage (hot water) to cover the necessary time lag. The system also represents a CHP solution, as the hot water recovered from compressor cooling is available for heating purposes. A thermodynamic model of the system was built, used for design, and a simulation covering system operation over one year was performed. The results show that the system could be recommended (possibly with the support of battery storage) for use in applications where complete off-grid operation is preferable, or where it is important to minimize the impact of the grid infrastructure, such as in natural parks and remote areas.

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