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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1231-A

Book of abstracts draft
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Power-to-pressure energy storage in natural gas transmission networks

Wojciech KOSTOWSKI, Silesian University of Technology, Poland
Katarzyna KOŁODZIEJ, Silesian University of Technology, Poland

The paper presents the possibility of energy storage in the existing natural gas transmission network under its normal operation. Currently, the so-called linepack management strategies are known, their idea is to switch a gas-turbine based compressor station (CS) from electricity-neutral to electricity generator mode. If the demand for electricity is low or medium, the CS operates consuming natural gas in a local gas turbine. In peak demand periods, the gas turbine switches from the CS driving mode into the electricity generation mode, providing an additional peak source of electricity. This strategy, albeit efficient, does not actually enable the electricity to be stored in the network. In the paper we propose 2 new strategies of electricity storage in a gas network. The first option includes a dedicated compressor-expander system installed at a regular pipeline section. The electric driven compressor increases gas pressure above the required level in periods of peak electricity generation, while the expander allows energy recovery. The expander is situated at some distance from the compressor, the distance is a design variable resulting from the required time distance between the charging and the discharging phase. Assuming 5-10 m/s transmission velocity, the distance required to achieve a 6 hours time-shift varies from approximately 100-200 km. The most intriguing feature of this system is a synergy effect related with pressure drop management, which allows, under certain conditions, to exceed 100% storage efficiency by reducing transmission losses. Storage efficiency obtained from the first quasi-dynamic simplified model ranges from 70 to 128% for the performed case study. The second option is related with the use of existing compressors and existing pressure letdown stations. The idea of storage is the same as in the 1st case, but the system is based on existing infrastructural objects. In the 2nd case, one can consider a deep expansion at the expander, with the target pressure defined by the distribution system. Due to the necessity of gas preheating at the expander inlet, the storage efficiency reduces to the level of about 30-40%. The 2nd option seems to be market-ready, yet this option requires a strategy to deal with multiple system exit points with energy recovery for partial gas fluxes.

Keywords: Energy storage, Gas network, Compressor station, Expander technologies, System integration
Acknowledgment: The proof-of-concept calculations were prepared in co-operation with Gaz-System S.A.