This study analyzed the effects of bidirectional heat trade of extra heat on the overall operational efficiency of interconnected thermal grids with empirical correlation formulation. A decision support operational simulation tool was developed to assess the technical-, and techno-economic performance of the complex and highly non-linear interconnected thermal grid system. From the techno-economic feasibility analysis for the test case of a hypothetical new thermal grid with a peak heat demand of 60 MWh, it was analyzed that the operating profit could be secured only for the gas engine, estimated to be about 8%. Moreover, the sensitivity analysis revealed that fuel price has the most dominant effect on operating profit in that the gas engine can attain 21% of operating profits as the fuel price is assumed to decrease by 20%. This study demonstrated the possibility of attaining favorable operational benefits with interconnected operation between thermal grids in terms of technological and techno-economic aspects with a newly proposed approach with empirical correlation formulation.

In this study, the actual operation status of the cogeneration model was investigated to examine the difference between the theoretical evaluation and the field operation situation. The adequacy of the installed capacity of the cogeneration system was assessed by using in-house developed diagnostic analysis simulation tool, and the effects of operational strategy on securing operational cost benefit under the progressive electricity rate system was also examined with event-based operating characteristic analysis. The installed prime mover was found to be designed excessively by an average of 47%, and the relative primary energy savings showed a large deviation in the range of 3–22% for each case. As a result of analyzing the effect of the rapid expansion of renewable energy on the operational performance, it was found that when the renewable power distribution ratio was increased to 30%, the relative primary energy savings effect fell to less than 5%. As an alternative, a hybrid cogeneration model integrated with heat pump was proposed, and it was confirmed that it could have the effect of mitigating the effect of expanding renewable energy.