Configuration optimization and energy management of a novel PEMFC/DCMD cogeneration system with PV and energy storage

The move towards achieving energy conservation and emission reduction has sparked interest in cogeneration system to promote renewable penetration. This paper proposes a novel power/freshwater cogeneration system to achieve power generation, energy storage and fresh water production based on proton exchange membrane fuel cell (PEMFC), direct contact membrane distillation (DCMD), PV and Vanadium Redox Flow Battery (VRFB). In order to meet the load variation requirements of users, a two-layer interactive optimization model is developed to explore the optimal configuration and operating strategy of the cogeneration system considering the factors of time-of-use power price, fuel price, carbon tax, and environmental change. A comprehensive evaluation of the cogeneration system in terms of technical, economic, and environmental performances is carried out utilizing the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) decision method based on entropy weight and Analytic Hierarchy Process (AHP). The case study results show that the proposed cogeneration system increase the annual total cost (ATC) by 19.40 %, reduce the annual carbon emissions (ACE) by 42432.97 tons/year, and increase the primary energy ratio (PER) by 21.32 %, respectively, demonstrating that the cogeneration system can effectively improve the energy efficiency and reduce the greenhouse gas emissions in comparison with grid-only power (reference system). The sensitivity analysis results indicate that the initial capital investment cost and methanol price are important factors affecting the ATC of the cogeneration system. In addition, the increase in the carbon tax price results in an increase of power purchase cost, which provides the reference basis for the formulation of carbon tax price.