ABSTRACT
This chapter concentrates on hybrid indirect cooling systems: to be precise, ground cooling using buried pipes, direct and indirect evaporative systems and radiative cooling through lightweight radiators. The chapter discusses the concepts, the physical principles, and the applicability in different climates, the more relevant technologies and the ways to improve its efficiency. It also includes direct cooling systems such as earth sheltering and roof solutions. The performance of a certain application depends on the efficiency of the technology used to transfer heat from the working fluid to the environmental sink. To improve the efficiency of the system, a flat-plate radiative cooler which looks like a flat-plate solar collector is used; the main difference is that there is no glazing, since ordinary glazing absorbs long-wavelength radiation. There are two types of flat plate radiators: air radiators, liquid radiators. Finally, there should be further development of passive cooling techniques, primarily those that improve indoor climatic conditions and the microclimate around buildings.
