Energy measurement and monitoring for solar water heating system

Abstract: A large number of non-pressure solar water heating systems have been installed in China, the majority of them possess storage tank which the effective volume are greater than 0.6 m3, and their influent and effluent are non-simultaneity, then directly using a calorimeter to calculate heat is inappropriate by measure the temperature difference between the inlet and outlet. Considering the operability of actual system, this paper presents a method for calculating the heat load of the solar water heating system by measurement parameters, such as inlet water temperature and flow, outlet water temperature and flow, storage tanks water temperature and water level. A variety of energy measurement methods and theoretical derivation are introduced in this paper, which including solar energy for heating, electricity consumption, auxiliary heat source energy, piping loop heat loss and heat load. And the sensors accuracy, installation requirements and remote monitoring technology are introduced exhaustively in this paper. The energy measurement and monitoring methods have been used successfully in the BHL solar water heating engineering control systems. A calorimeter has been developed for measuring the solar heat load which uses the heat load calculation formula, and another calorimeter for measuring the solar heat energy and piping heat loss which uses the simultaneity heat calculation formula. The calorimeter can get the amount of hot water used and calculate the cost for each user, which supports ModBus communication protocol. The system uses a three-phase auxiliary heating to provide energy when solar energy is insufficient. And the remote three-phase energy meter supports Modbus communication protocol too. Actually it shows that this method can accurately and effectively measure all kinds of energy of the solar water heating system, and it is suitable for energy measurement and monitoring of the solar water heating system in China. The experiment can provide technical reserves for developing the energy measurement and monitoring national standards of solar water heating system.