Towards optimal design of solar assisted industrial processes: Case study of a dairy

Pinch analysis is a valuable tool for industrial process integration and optimization. Based on heat cascading and Mixed Integer Linear Programming (MILP) the optimal utility system can be found, includ- ing traditional heat sources (burners, boilers) and more innovative components, such as compression and absorption heat pumps. Investigation of the potential and design of renewable sources, such as solar thermal or photovoltaics, imposes several additional elements: time-dependence of the source, storage inertia and losses, and the system intrinsic non-linearity are difficult to represent by linearized time-invariant equations. In this work, a set of multi-period MILP equations for solar components are presented as well as a superstructure for optimization of heat pump cycles. The presented approach offers a comprehensive methodology that allows simultaneous optimization of the process’ refrigeration and renewable utility system. The proposed methodology is illustrated on the basis of a dairy plant where the different solar components are compared and evaluated based on cost and emissions.