Modelling and operation optimization of an integrated energy based direct district water-heating system

This paper proposes a model of an integrated energy based direct district water-heating system, which makes joint use of wind energy, solar energy, natural gas and electric energy. The model includes a stand-alone wind turbine generator, heat producers, a water supply network and heating load. This research also investigates an optimal operating strategy in which the fossil fuel consumption of the system in daily operation is optimized. Based on the model, an objective function used to obtain the optimal control strategy is constructed with complex operating constraints. GSO (Group Search Optimizer) is used to trace the optimal set-point temperature of boilers and the optimal water flow of pumps to minimize fuels consumption while satisfying variable constraints. In order to verify the model and optimal operating strategy, simulation studies have been undertaken. The optimal operating strategy is evaluated in comparison with an unoptimized control strategy. The simulation results prove the validity of the model and show that the optimal operating strategy is able to make the system operation more energy efficient. The proposed system is also evaluated in comparison with a conventional natural gas heating system. The comparative results demonstrate the investment feasibility, the significant energy saving and cost reduction achieved in daily operation. (C) 2013 Elsevier Ltd. All rights reserved.