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This study proposes a novel operational planning method for polymer electrolyte fuel cell cogeneration systems (PEFC-CGSs). PEFC-CGSs provide hot water by utilizing waste heat produced in the electricity generation process, and hot water is stored in an attached tank. Generating and storing hot water based on an optimal operational plan according to household demand leads to further energy saving; therefore, operational planning methods based on household demand prediction have received significant attention. However, the improvement in the demand prediction accuracy does not necessarily lead to efficient PEFC-CGS operation in terms of operational costs; in other words, the accuracy in the demand prediction does not directly indicate the resulting operational efficiency. In this study, the authors propose a novel approach based on a surrogate model for deriving an appropriate plan that minimizes the expected operational costs among the operational plan candidates. In the proposed scheme, the error between expected and actual operational costs explicitly represents the relevance of the operational plan, so that the optimal operational plan can be selected directly from the perspective of the resulting operational efficiency. The practicality of the proposed approach is evaluated with the existing demand prediction-based approach via numerical simulations using real-world measurements of multiple customers in Japan. The proposed method reveals 30% reduction of the excessive operational costs by avoiding the inefficient operation of the auxiliary gas-heater in the experiments and will further enhance the value of introducing highly efficient residential fuel cell system that contributes to a low-carbon society. INDEX TERMS Cost minimization, machine learning, operational planning, polymer electrolyte fuel cell cogeneration systems, surrogate model.

This study mainly aimed to compare operation planning schemes for polymer electrolyte fuel cell cogeneration systems (PEFC-CGSs) to analyze derived operation plans from various perspectives. PEFC-CGSs provide hot water by using waste heat produced in electricity generation. Therefore, they have considerable potential for further energy saving and can be efficient systems by generating and storing heat according to household demand. Operation planning scheme based on the prediction of household electricity and hot water demands is a promising approach to achieving further energy saving. However, operation results imply that improvement in accuracy from the viewpoint of prediction error does not always lead to efficient PEFC-CGS operation. In this study, we implemented several operation schemes and analyzed them by simulation from various perspectives, namely, operation cost breakdown, demand types and robustness required for the operation plan, to attempt further operation cost reduction.

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