NOVELTY - The system (3) has an aperture (15) allowing energy transfer from solar radiation to fluid (5). The aperture includes a first material layer (9) on a part of a process equipment i.e. pipe (7). The first material layer is transparent to solar radiation and formed as a thermal insulator to minimize heat loss from the fluid via first material at all times. A second material layer (11) provided on a part of the process equipment is not transparent to solar radiation and formed as the thermal insulator to minimize heat loss from the fluid via second material at all times.    USE - System for heating fluid e.g. crude oil, fuel oil and palm oil, conveyed or contained in a process equipment i.e. pipe (claimed), by solar energy. Can also be used for heating the fluid conveyed or contained in a tank, valve and a pump.    ADVANTAGE - The system maximizes ratio of heat gain in the fluid in the pipe or another process equipment as a result of exposure to solar radiation, and minimizes thermal heat loss from the fluid as consequence of heat transfer from the fluid, thus enhancing temperature increase. The solar heat gain for given thickness of the first material layer can be increased by changing effective aperture size by providing a reflective surface on sides of the aperture to reflect solar radiation from the reflective surface into the aperture. The solar heat gain can be increased by providing the system with an optical element such as reflector, that increases an amount of the solar radiation that is incident on the aperture. The system provides minimal variations in temperature for longer time period, thus controlling temperature. The system minimizes thermal heat loss by providing the aperture with an emissivity control unit that reduces emissivity of the aperture to minimize loss of heat from the pipe.    DETAILED DESCRIPTION - The first material layer is an aerogel (RTM: synthetic porous material) layer. An INDEPENDENT CLAIM is also included for a method for manufacturing a pipe.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic sectional view of a system for heating fluid.    System for heating fluid conveyed or contained in process equipment (3)    Fluid (5)    Pipe (7)    Material layers (9, 11)    Aperture (15)    Reflector (17)