Abstract: A system for heating a fluid conveyed or contained in a pipe or other process equipment by solar energy is disclosed. The system includes passive and active control methods to control the temperature of the fluid within a selected temperature range. The passive methods use the natural properties of selected materials for the system and the geometry and the orientation of the materials to control the temperature range. The active methods uses one or more than one control mechanism for changing the ratio of energy gain and heat loss at any point in time during a day and between days and across seasons, with these mechanisms including mechanisms to control energy transfer in and heat transfer out of the fluid.

Abstract: A system for heating a fluid conveyed or contained in a pipe or other process equipment by solar energy is disclosed. The system includes passive and active control methods to control the temperature of the fluid within a selected temperature range. The passive methods use the natural properties of selected materials for the system and the geometry and the orientation of the materials to control the temperature range. The active methods uses one or more than one control mechanism for changing the ratio of energy gain and heat loss at any point in time during a day and between days and across seasons, with these mechanisms including mechanisms to control energy transfer in and heat transfer out of the fluid.

Abstract: A system for heating a fluid (5) conveyed or contained in process equipment (7) comprises a layer of transparent thermal insulation (9) which partly covers the process equipment so that a section (13) is exposed to solar radiation and thus is heated by the solar radiation and thereby heats the fluid (5). The "window" defines a form of thermal diode concentrator in that the surface area of the "window" is great than that of the exposed section (13) of the process equipment (7) and thus the "window" in effect concentrates the solar radiation onto the exposed section (13) of the process equipment, and the transparent thermal insulation (9), albeit transparent, minimises heat loss from the fluid (5).