Passive Solar Passive solar systems are the simplest and least costly alternatives for direct use of solar radiation for practical purposes. Passive systems depend on natural convection for circulation. Passive solar water heating (SWH) systems, the most frequently found liquid-based passive solar applications; usually. Heat transfer fluids are also employed in solar energy generation, in concentrators such as linear Fresnel, parabolic and trough-based systems. A. Paratherm does not manufacture, support or distribute glycol-based heat transfer fluids, but can recommend suppliers. This information has been. In conclusion, high temperature heat transfer fluids are used widely in the manufacturing processes for polysilicon, the material used to create photovoltaics, in a process similar to that used in the manufacture of computer chips. Photovoltaic solar (PV.