Integration options for solar thermal with low temperature industrial heat recovery loops

Abstract

This paper investigates three general methods for integrating industrial solar heating into an HRL (Heat Recovery Loop) using an industrial case study. Integration of solar thermal energy into low temperature pinch processes, like dairy and food and beverage processes, is more economic when combined with an HRL to form a combined inter-plant heat recovery and renewable energy utility system. The combined system shares common infrastructure such as piping, pumping and storage, and improves solar heat utilisation through direct solar boosting of the HRL intermediate fluid's temperature and enthalpy either through parallel or series integration relative to the other sources and sinks in the HRL system. Three options for integrating solar thermal directly into HRLs are dynamically modelled using historical plant data from a large multi-plant dairy case study to demonstrate the hot utility savings potential of the solar-HRL system. For the dairy case study, results show the best location for integrating solar heating into an HRL is in series with the heat sources as the hot fluid returns to the storage tank. This configuration maximises the effectiveness of collecting solar heat as a meaningful replacement of non-renewable process heat.