A Novel “Wireless On-Off Control” Technique for Household Heat Adjusting and Metering in District Heating System

A large-scale survey and on-site measurements on space heating systems in Beijing has been carried out since 2005. Detailed analysis shows that the improvement of system regulation to adjust the heating demand and to avoid over-heating in building space is the key to reduce the heating energy consumption. It also indicates that combined heat and power (CHP) based district heating network is the most suitable solution for the space heating in Chinese northern cities. Thus, the priority should be in the research and development of new techniques to improve heating system regulation and control. In China, there are three reasons for poor heating system regulation: • the lack of control devices in space heating system, • the complex and inconvenient operation, and • the insufficient motivation because the charging policy is based on the heating areas. Field test results show that 20% to 30% of thermal energy is wasted because of the poor heating system regulation. In order to solve these problems, a novel “wireless on-off control” system for household heat adjusting and metering has been proposed. This technology works in the following way: 1) a calorimeter is installed at each building to measure the total heat consumption of the whole building; 2) an on-off valve is installed for each household and an indoor temperature controller is provided for the occupants. The operation procedure is as follows. First, the desired indoor temperature is set by the users through the indoor temperature controller and wireless signals are sent to the on-off valve. Then the on-off valve detects the real indoor temperature and determines the difference between the real temperature and the set value. After this, the valve calculates the proportion of on-time to off-time in the next step according to the thermal strategies programmed in the valve’ CPU. Then the valve is controlled according to the proportion to maintain the desired indoor temperature; and 3) the heating cost of each household can be allocated according to its heating area and the accumulative open time of the valve. The proposed technique has been applied in fifteen residential communities with the total areas of 1,200,000 m². The testing results show that: 1) indoor temperatures were accurately controlled within +/− 0.5 °C around the set point, so that the problem of overheating can be avoided; 2) the difference of temperature in different room is less than 1 °C. Therefore, if radiators in each room are designed reasonably, to control the temperature of one room can meet the requirements of the entire user’s apartment; 3) energy consumption in the controlled household was approximately 30% lower than the uncontrolled household with the same building type.