Solar energy offers a great potential for integration with industrial processes, which conventionally rely on fossil fuels to provide energy. The seasonal, daily, and regional dependence of solar energy alongside the scarcity of space or financial resources in many territories constitute great challenges. These may be overcome by efficient solar energy use through optimal integration methods. Such methods should address multiple aspects including accurate solar technology models and identification of the "true" process requirements. Beyond that, optimal design of the integrated systems and quantification of the added value of solar integration, particularly with regard to competing technologies, is crucial. This thesis explores this multi-dimensional problem formulation through elaboration ofmethodologies tailored to the low-temperature processing industries. The intricacies behind this goal are addressed in four main chapters. (a) The first chapter examines options for solar technology modeling in view of industrial integration. A design approach is developed which allows estimation of solar system performance at sufficient precision and constrained computational effort. (b) In the second chapter, a comprehensive method is proposed which addresses simultaneous optimization of the process heat recovery, the conventional utilities, and the renewable utility system (including thermal storage) using e-constrained parametric optimization. (c) The promising results from the third chapter motivate a more thorough analysis of industrial heat pump systems, which is addressed the following chapter presenting a novel generic heat pump superstructure-based synthesis method for industrial applications based on mathematical programming. (d) The subsequent two chapters address generalization of the derived methods to estimate potentials of relevant technologies at national and international scale from the perspective of multiple stakeholders. The derived method generates a database of solutions by applying generalized optimization techniques. The proposed methods are applied to the dairy industry and results reveal that solar energy should be considered as part of a series of efficiency measures. It is shown that in many cases heat pumping or mechanical vapor re-compression lead to more efficient and less costly solutions, which may be extended with solar thermal energy or complimented with solar electricity.