Session: 17-02 Techno-Economic Analysis of Energy Systems

Paper Number: 128921

128921 - State-of-Charge (SoC) Management of PTES Coupled Industrial Cogeneration Systems 

Large-scale energy storage is widely regarded as an invaluable aspect of the ongoing renewable energy transition in the global energy systems. Energy storage can mitigate the inherent intermittency issues associated with most renewables. It would allow dispatchable renewable energy usage, which is a property currently lacking in the renewable energy sector. Additionally, energy storage allows for increased share of renewables in the energy grid. This field of is abundant in current research initiatives.

Most renewables are an electricity-only energy source. In contrast with fossil fuels, which are combusted for usage, and thus can be used as a heat source in addition to generating electricity, current renewable technologies mainly produce electricity directly. With increasing renewable penetration in the world’s energy grids, this lack of heating will increasingly cause compatibility issues. One solution that can be adapted from fossil fuel power plants is the use of cogeneration. [1] Cogeneration is the production of both useable heat and electricity from a single source. Conventionally, this was done to increase the overall efficiency of fossil fuel power plants. More recently, application of cogeneration in renewable have been gaining traction. This revolution will aide in covering the heating deficiency of renewable sources.

This study has identified the common ground between energy storage and cogeneration as thermal energy storage (TES). Currently, TES accounts for only 2% of global energy storage capacity. [2] Adding cogeneration technologies to energy storage technologies will increase their overall. The challenge is to design systems that can reliably provide electricity, heating, and cooling. Additionally, as with conventional powerplants, having an electricity-in, multi vector energy-out storage system will yield higher efficiencies. The study is built on a Pumped Thermal Energy Storage (PTES) system, utilizing supercritical CO₂ Brayton cycle with hot molten salt, and cold water storage.

The study proposes a state-of-charge (SoC) management protocol that can be used to manage the storage charging and discharging capacity at each storage tank. With the proposed SoC management technology, consistent and rigorous charge and discharge control can be achieved. The novelty of this study, however, is the introduction and management of cogeneration capabilities to the storage solution. The results show that cogeneration with TES systems requires very tight control and optimization of heat-to-electricity ratios, otherwise the system tends to an only electricity or only heat supply. The cogeneration capabilities increase the apparent capacity of TES systems. In scenarios without cogeneration, the system would wait in idle mode as there was no more charge capacity. Cogeneration opens a new discharge path for energy from the system so that the overall charging and discharging times increase. The study proposes further investigation of the synergy in TES systems by developing dynamic models and implementing the cogeneration technologies in case studies involving heat exchanger networks.

[1] J. Wang, S. You, Y. Zong, C. Træholt, Z. Y. Dong, and Y. Zhou, “Flexibility of combined heat and power plants: A review of technologies and operation strategies,” Applied Energy, vol. 252, p. 113445, Oct. 2019, doi: https://doi.org/10.1016/j.apenergy.2019.113445.

[2] M. C. Argyrou, P. Christodoulides, and S. A. Kalogirou, “Energy storage for electricity generation and related processes: Technologies appraisal and grid scale applications,” Renewable and Sustainable Energy Reviews, vol. 94, pp. 804–821, Oct. 2018, doi: https://doi.org/10.1016/j.rser.2018.06.044.

Presenting Author: Alp Albay Imperial College London

Presenting Author Biography: Alp Albay is a Chemical Engineering PhD student at Imperial College London, working on Grid Integration of Industrial Cogeneration Systems. He received his master’s from Imperial College London, working on Modelling of Tritium Removal from Fluoride Salt Cooled High Temperature Reactors and his bachelors from Johns Hopkins University, majoring in Chemical Engineering and Applied Mathematics. His interests are in renewable energy sector, mainly process modelling of energy storage systems and integration into the grid to aid in transition to net zero.

Authors:

Alp Albay Imperial College London
Zhennan Zhu Imperial College London
Mehmet Mercangoz Imperial College London