The majority of parabolic trough concentrating solar power plants consist of an indirect system where the heat transfer fluid (typically synthetic oil) exchanges energy with a secondary circuit which is connected to the power cycle. Synthetic oil has a technical limitation by the maximum operating temperature. This results in the search for new fluids. On the other hand, with the aim of having energy when there is no sun shining, it has increased the use of thermal storage. Thermal energy storage systems are composed of molten salts and presents higher operating temperatures than synthetic oil. Thus, direct systems, in which thermal storage and heat transfer fluid are unified and normally molten salts, emerge to improve the power cycle performance. To determine the future potential of direct systems, this paper evaluates the environmental damage of two types of molten salts and synthetic oil in order to decide whether the use of salts is better than synthetic oil, from an environmental point of view by using the Life Cycle Assessment (LCA) techniques. LCA results showed greater impacts in the synthetic oil case than the molten salts.