Comparative study on flexibility enhancement of combined heat and power for wind power accommodation

Flexibility enhancement of coal-fired combined heat and power units is an essential approach for improving the wind power accommodation and a significant low-carbon way to achieve clean urban heating. To consume excess wind power, this paper proposed a novel combined heat and power system integrated with the various flexible technologies. The EBSILON software was applied for modeling the proposed thermal systems and analyzing the thermal performance under different operating conditions. On this basis, the mechanism of their heating compensation and wind power consumption was revealed and the indicator, the heating compensation capacity, was presented considering from both peak shaving and coal-savings perspectives. Compared with the conventional system, the wind power accommodation rate of the novel system had a maximum increment of 31.7% and the standard coal consumption had a maximum reduction of 14.3%. Meanwhile, by adding dynamic payback period and internal rate of return, the techno-economic performances were more reasonable and precise. The results showed that the heating compensation capacities of absorption heat pumps, low-pressure cylinder of turbine removal and thermal energy storage with extracted steam from turbine are 0.29 t/MWh, 0.26 t/ MWh, and 0.25 t/MWh, respectively, which are better than that of other technologies. The net annual revenue of thermal energy storage system could reach 3.87 M$, 0.57 and 0.37 M$ higher than that of low-pressure cylinder of turbine removal and absorption heat pumps, respectively. It can be concluded that thermal energy storage can be the best to balance the peak shaving demand and techno-economic performance. In all, the proposed systems provided a promising method for the flexibilization of coal-fired combined heat and power units alongside new renewable systems.