Energy saving maximization on combined heat and power units in different scenarios

Cogeneration takes several advantages of energy saving and economy. This study aims to evaluate and maximize the energy saving effect of cogeneration in different scenarios. Accordingly, optimization models on the cogeneration share coefficient, a dimensionless index describing the heat load ratio undertaken by cogeneration in district heating, are developed to maximize the energy saving with a reference case. The research results reveal that the off-design performance of cogeneration is an important factor affecting optimization. In the new scenario, the construction of new cogeneration units does not save energy when the share of renewable power in the replaced power generation is higher than the threshold value of 0.150. Moreover, the optimal cogeneration share coefficient for the electric heating boiler increases from 0.807 to 0.910, and the maximum primary energy saving increases from 4.450 × 10¹² kJ·year⁻¹ to 9.414 × 10¹² kJ·year⁻¹ when the share of heat supplied by the power-to-heat devices increases from 0 to 0.500. The optimal cogeneration share coefficient for the electric heat pump declines from 0.807 to 0.732, and the maximum primary energy saving reduces from 4.450 × 10¹² kJ·year⁻¹ to 2.632 × 10¹² kJ·year⁻¹. The obtained results show the effectiveness of the model in terms of analyzing the energy saving of cogeneration in different scenarios.