Abstract
Solid oxide fuel cells (SOFC) have developed to a mature technology, able to achieve electrical efficiencies beyond 60%. This makes them particularly suitable for off-grid applications, where SOFCs can supply both electricity and heat at high efficiency. Concerns related to lifetime, particularly when operated dynamically, and the high investment cost are however still the main obstacles towards a widespread adoption of this technology. In this paper, we propose a hybrid cogeneration system that attempts to overcome these limitations, in which the SOFC mainly provides the baseload of the system. The introduction of a purification unit allows the production and storage of pure hydrogen from the SOFC anode off-gas. The hydrogen can be stored, and used in a proton exchange membrane fuel cell (PEMFC) during peak demands. The SOFC system is completed with a battery, used during periods of high electricity production. In this paper, we propose the use of a mixed integer-linear optimization framework for the sizing of the different components of the system, and particularly for identifying the optimal trade-off between round-trip efficiency and investment cost of the battery-based and hydrogen-based storage systems. The proposed system is applied and optimized to two case studies: an off-grid dwelling, and a cruise ship. The results show that, if the SOFC is used as the main energy conversion technology of the system, the use of hydrogen storage in combination with a PEMFC and a battery is more economically convenient compared to the use of the SOFC in stand-alone mode, or of pure battery storage. The results show that the proposed hybrid storage solution makes it possible to reduce the investment cost of the system, while maintaining the use of the SOFC as the main energy source of the system.
Highlights
In this paper, we present a cogeneration system meant for off-grid applications
We described the main features of the proposed cogeneration system based on a solid oxide fuel cell (SOFC) with hybrid energy storage for off-grid applications
We proposed a system made of an hybrid SOFC, able to generate both power, heat and hydrogen, coupled with a proton exchange membrane fuel cell (PEMFC), a battery, and a hydrogen storage tank
Summary
We present a cogeneration system meant for off-grid applications. The proposed system is centered around its main unit, a solid oxide fuel cell (SOFC), that generates electric power and heat. The anode-off gas of the SOFC is upgraded and purified for hydrogen production, which is stored for later use in a proton exchange membrane fuel cell (PEMFC). As concerns over anthropogenic greenhouse gas (GHG) emissions increase globally, new technical solutions are becoming available to maintain today’s life standards while moving toward a more sustainable use of natural resources. In this context, off-grid applications (i.e., users not connected to a country’s main electrical grid) are assuming an increasingly important role in the future energy systems. Among them are the cost and public opposition to new transmission lines and large power plants, the need of reducing the vulnerability of the supply chain in centralized systems, and the increased performance of small power technologies (Mandelli et al, 2016)
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