A multi-period design method for the steam and power systems coupling solar thermal energy and waste heat recovery in refineries

Abstract

It is imperative to reduce carbon emissions by comprehensively utilizing renewable energies and waste heat in refineries. However, the intermittent supply of solar thermal energy, the periodic changes of waste heat, and the variable demands of steam and electricity in refineries hinder optimal design and stable operation of the steam and power systems. In this work, an optimal design method for coordination of solar thermal energy and waste heat to produce steam and electricity in refineries was proposed, which features a multi-period mathematical programming model to synchronously determine the economy, the optimal capacity configuration, and the power scheduling scheme for the steam and power system. The influence of the serial and parallel structures of solar thermal energy supply, the model processing method for continuity of energy storage among different subperiods, and parametric analysis on the results were analyzed and discussed in detail. The results show that the cost of the solar thermal collectors and the energy storage system accounts for the significant proportion of the investment cost of the system. The cost of solar thermal collectors accounts for the largest proportion of the investment cost of the system, which is about 60% in the case study. The parallel structure of solar thermal energy supply can significantly reduce the total cost of the system. The coordination of solar thermal energy and waste heat recovery can jointly meet the steam demand to ensure the stability of the energy supply of the system. The comprehensive interactions and coordination between the solar steam generation systems, waste heat systems, energy storage systems, and demands are analyzed. The battery is necessary for short-time energy storage, whereas thermal energy storage should be used for either long-term or short-term energy storage. These results provide fundamental support for the optimal design of the steam and power systems in refineries by the comprehensive utilization of solar thermal energy and waste heat.