Design of Integrated Solar Thermal Energy System for Multi- Period Process Heat Demand

Abstract

This paper presents a new methodology for integrating renewable energy sources such as solar with chemical process utility demand. In chemical plant operations, the demand for utilities, as well as available process heat loads, are sometimes seasonal or multi-period in nature. Also, the availability of renewable energy such as solar, is time of day dependent as well as seasonal, i.e. time of year dependent. Therefore, in order to fully harness the economic and environmental benefits associated with the use of solar thermal energy, an approach which systematically integrates solar thermal radiation with process heat demand and other sources of utilities in chemical plants, while considering the multi-period profile of both the utility sources and the process streams need to be developed. The approach adopted in this paper, entails the use of the multi-period version of the stage-wise superstructure with an objective function involving a simultaneous minimisation of the annualised investment costs and annual operating cost of the network. The utility sources considered include solar and fossil fuel. The fossil fuel is included as a back-up depending on how much of the process heat demand is satisfied by solar energy. For the solar energy source, concentrated solar thermal collector is considered for both direct and indirect Heat Integration including thermal energy storage. In the example considered, a reasonable amount of cost savings was obtained when compared to the case without solar thermal integration.