Abstract
Combined heat and power (CHP), an efficient heating method with cascades use of energy, accounts for approximately 50% of the heat sources in northern China. Many researchers have made significant efforts to improve its energy efficiency and environmental effects with important achievements. Given that the system produces heat and electricity at the same time, this study focuses on the role of CHP in the holistic urban energy system and points out the mismatch between the demand and supply sides of urban energy systems by using the heat-to-power ratio as a parameter. The calculation method and characteristics of the supply side heat-to-power ratio of eight heating methods and the maximum demand side heat-to-power ratio for 19 cities in northern China are displayed. After the analysis, it is concluded that (1) the maximum demand side heat-to-power ratio in the cities varies from 1.0 to 5.9, which is affected by the location and social, economic, and industrial structures. (2) In most of the cities, with the current energy structure, the demand side heat-to-power ratios are always larger than the supply side heat-to-power ratios. (3) The reduction in heating demand, surplus heat recovery, and the use of a highly efficient electric heating method, such as the heat pump, can help solve the mismatch of the heat-to-power ratio between the demand and supply sides. These conclusions can guide the urban energy planning and system construction.
Highlights
Combined heat and power (CHP) accounts for approximately 50% of the heat sources in northernChina
The electricity-regulating ability of CHP is weak in wintertime owing to the operation of CHP systems based on heat demand
The results showed that the heat-to-power ratio of demand would affect the primary energy saving of the co-generation system, while the calculation only considered the electricity and domestic hot water demand
Summary
It can efficiently generate heat and electricity simultaneously, which is considered the most efficient heating method. Owing to the current situation that heat and most of the power are locally used, the characteristics of heat and electricity consumption in the cities sometimes do not match those of the CHP supply. Coal-fired CHPs have been gradually replaced by gas-fired ones. Gas-fired CHPs have higher generation efficiency than that of coal-fired ones. To guarantee the heating supply, more electricity has been generated, which intensifies the power excess. The power transmission capacity between regions in China is limited, which has caused huge problems in the energy system. The relative amount of heat and electricity generated in CHP can only change within a limited range.
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