Development of a 10/40 Kw Rsoc Demonstration System
Authors: Peters Roland , Kunz Felix , Kruse Nicolas , Eichel Rüdiger-A. 
Published: November 2022

Scientific Approach
In the last decade, work on the development of a reversible Solid Oxide Cell (rSOC) technology has been greatly intensified because it can contribute to the storage and the reconversion of electricity from regenerative energy sources.
In this context, Forschungszentrum Jülich GmbH first examined the feasibility in a thermodynamic analysis. Here, Frank et al. [1] show that electrical efficiencies of 67% in fuel cell mode and 76% in electrolysis mode can be achieved when such a system is operated with a 70 bar hydrogen storage. This corresponds to a round-trip efficiency of more than 50%.
Based on these results, an rSOC system demonstrator with a nominal power of 10 kWel in fuel cell mode and 40 kWel in electrolysis mode was developed. The attached figure shows the simplified system flow diagram.
The Integrated Module (IM) is the main component of the rSOC system and consists of four Jülich 20-layer sub stacks in combination with an air and a fuel heat exchanger. Also, five electrically operated heating plates are located within the module to heat up the system from ambient temperature to operating temperature and to support endothermal electrolysis operation. The supporting balance of plant components (BoP) are arranged in the direct vicinity of the IM in order to achieve the most compact layout possible.
To be able to classify the efficiency results listed below, the calculation method for the fuel cell efficiency is shown in equation (1), for the electrolysis efficiency in equation (2) and for the power consumption of the BoP in equation (3).
𝜼_(𝐹𝐶, 𝑆𝑦𝑠, 𝐴𝐶) = (𝑈_𝑆𝑡𝑎𝑐𝑘 ∙ 𝐼_𝑆𝑡𝑎𝑐𝑘 ∙ 𝜂_𝐼𝑛𝑣𝑒𝑟𝑡𝑒𝑟 − ∑𝑃_(𝐵𝑜𝑃, 𝐴𝐶))/(𝑛_(𝐻2, 𝑠𝑦𝑠𝑡𝑒𝑚 𝑖𝑛) ∙ [𝐿𝐻𝑉]_𝐻2 ) (1)
𝞰_(𝐸𝐿, 𝑆𝑦𝑠, 𝐴𝐶) = (𝑛_(𝐻2, 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑) ∙ [𝐿𝐻𝑉]_𝐻2)/((𝑈_𝑆𝑡𝑎𝑐𝑘 ∙ 𝐼_𝑆𝑡𝑎𝑐𝑘)/𝞰_𝑅𝑒𝑐𝑡𝑖𝑓𝑖𝑒𝑟 + ∑𝑃_(𝐵𝑜𝑃, 𝐴𝐶)) (2)
∑𝑃_(𝐵𝑜𝑃, 𝐴𝐶) = 𝑃_(𝑎𝑖𝑟 𝑐𝑜𝑚𝑝.) + 𝑃_(𝑑𝑖𝑎𝑝ℎ𝑟. 𝑐𝑜𝑚𝑝.) + 𝑃_(ℎ𝑒𝑎𝑡𝑖𝑛𝑔 𝑝𝑙𝑎𝑡𝑒𝑠) + 𝑃_(𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑠𝑦𝑠.) + 𝑃_(𝑠𝑡𝑒𝑎𝑚 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑜𝑟) (3)
System operation was started on 06/01/2021. After a short commissioning phase, stationary power points were approached for both operating modes, fuel cell and electrolysis. In fuel cell mode, a power range from 1.7 kWel to 13 kWel could be shown. At the operating point of 500 mA cm-2 with a system fuel gas utilization of 98%, a system output of 10.3 kWel with a maximum efficiency of 63.3% could be achieved. In the case of electrolysis, a system output of - 49.6 kWel with a system efficiency of 71.1% was measured with a steam utilization of 80%.
Outlook
In the future it is planned to implement new methods of the stack temperature control based on artificial neural networks. After a successful implementation, realistic load profiles are developed and examined during the system operation.
As further development work in the area of SOC system technology, it is planned to investigate combinations with storage on the electrical and gas side, heat recuperation for district heating application as well as further demonstration projects in the area of co-electrolysis with corresponding upstream integration of different CO2 sources and downstream integration of synthesis technologies for the generation of chemicals and e-fuels.
Acknowledgement
The authors would like to thank their colleagues at Forschungszentrum Jülich GmbH for their great support and the Helmholtz Society, the German Federal Ministry of Education and Research as well as the Ministry of Culture and Science of the Federal State of North Rhine-Westphalia for financing these activities as part of the Living Lab Energy Campus.
References

Frank M, Deja R, Peters R, Blum L, Stolten D. Bypassing renewable variability with a reversible solid oxide cell plant. Applied Energy. 2018; 217:101-12.

Figure 1