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New paper on efficiency of Power-to-Gas (P2G) system based on SOE in Energy Conversion and Management

2019 / 08 / 29

New paper discussing efficiency of Power-to-Gas (P2G) system based on SOE was published in Energy Conversion and Management. It presents the results of joint work of IEn's HiTEP - Department of High Temperature Electrochemical Processes (Jakub Kupecki, Konrad Motyliński, Stanisław Jagielski, Michał Wierzbicki, Yevgeniy Naumovich and Marek Skrzypkiewicz) and National Fuel Cell Research Center, University of California, Irvine in the USA, NFCRC UCI, Prof. Jack Brouwer (APEP-Advanced Power and Energy Program).

This article presents a conceptual power-to-gas system based on a high temperature electrolysis unit. The solid oxide electrolyzer (SOE) delivers highly efficient conversion of intermittent electricity from wind and solar into hydrogen, which can then be directly injected into the gas grid or used to synthesize methane in a Sabatier reactor. Due to the unpredictable character of these sources, the grid experiences imbalances, which destabilize the energy system. The solution, in the form of a high temperature electrolyzer, mitigates the problem by coupling the electric and gas grids.

The advantages of solid oxide electrolysis over conventional electrolyzers are as follows: (i) SOEC offers outstanding efficiency, exceeding 70–80%, (ii) no noble metals are needed for catalytic reactions – the ceramic materials of electrodes and the high temperature substitute noble metal loading, (iii) SOEC mode can be switched to SOFC and the interchange supports the unique self-healing of the cells, (iv) modular design makes it easy to scale up the system based on the SOEC stack, (v) absence of any liquid electrolyte that has to be replaced on a regular basis. The 10 kW-class power-to-gas system is presented and the efficiency of the system assessed and discussed from an energy point of view. Accepting the current assumptions related to the performance of cells making up the electrolysis unit, the system can achieve efficiency in excess of 74%. The modeling approach is given and the performance map of the system is analyzed with respect to the variation of voltage and steam utilization in the electrolyzer.

The publication is available here: https://www.sciencedirect.com/science/article/pii/S0196890419309252

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