Efficiency improvement of a fuel cell cogeneration plant linked with district heating: Construction of a water condensation latent heat recovery system and analysis of real operational data

When a large fuel cell power plant is connected to a district heating network, the cogeneration efficiency of the power plant is usually insufficient (60-79%). In this study, we focused on the latent heat of water generated from the fuel cell reaction H2 + O2 -* H2O, which is an unutilized energy source. This technique is a potential solution for enhancing the total efficiency of the system. A new system linking a large-scale fuel cell power plant to a district heating system was developed. Its primary energy efficiency significantly increased (26.6%) owing to the maximum utilization of the latent heat from the water vapor condensation. This innovative system was installed in a 10.56 MW fuel-cell power plant, and operational data for the temperature and flow rate balance were obtained and analyzed. The results indicate that this system reduces investment costs by approximately 50% using cascade heat utilization technology for district heating systems, and consequently, the estimated payback period is less than 2 y.