Study on a Newly Absorption Heat Pump District Heating System

Combined heat and power (CHP) has higher efficiency than other heating supply methods. However, the total heating supply capacity from CHP plants will soon be lower than the total heating demand in Beijing by 2010. Investigation showed that 10% to 20% of total energy consumption was rejected to the surroundings through cooling water in CHP plants. The cooling water temperature leaving the condenser is normally in the range of 20–35°C during the heating season. This temperature is too low to be used for heating purpose. The total quantity of rejected heat is roughly equivalent to the energy to condition (heating) 25 million m² building areas. Although circulating water in power plants has many advantages compared with other HP heat sources commonly used, it’s nearly impossible to operate a pipe network with such a small ΔT (10∼15°C) economically. A newly solution based on absorption heat pump (HP) was investigated and a smallscale demonstration project was built in Chifeng, a city of Inner Mongolia in North China. In such a newly district heating (DH) System, the primary pipe network will operate in ΔT of ≈100°C without any change in both outlet temperature of CHP sources and operating temperature of secondary pipe network. Inlet temperature of primary pipe network decreased to 20∼25°C, which makes possibility for waste heat recovery of circulating cooling water in most CHP plants. Comprehensive efficiency in CHP plants will improve 10% ∼ 20% theoretically. Operation effect during whole heating season of the demonstration project was also introduced.