This book is intended to provide an engineering point of view and the design tools for low temperature solar collectors, as well as their networks in large solar installations for the integration of solar energy in processing industries. To this end, the book covers the description of existing solar technology, performance enhancement techniques for single units, hydrodynamics and its influence on flow distribution inside tubes, its effect upon thermal efficiency and pressure drop profiles. A detailed graphical description of the thermo-hydraulic behavior using experimentally validated Computational Fluid Dynamics simulations are described. An important contribution is the introduction of the main concepts to design and specify the structure of solar collector networks based on the reconciliation of the thermal and hydraulic lengths. The thermal performance is analyzed as a function of the velocity of the fluid and its relation to the rate of heat transfer. Likewise, velocity is analyzed in connection to the pressure drop. This approach allows the engineer to determine the structure of a solar collector network, which is defined by two parameters: the number of parallel sets of collectors and the number of collectors per set to achieve the process thermal needs at the specified temperature within the limitations of the pressure drop. These tools are put forward within the frame of flexible plant operation.