Master´s thesis presents a comparison of the standard solar thermal power plant technology which uses oil as a working fluid, these systems are commercially applicable, have single-phase flows and are easily scaled; and the new technologies of solar thermal power plants i.e. Direct Steam Generators (DSG). Standard solar thermal power plant systems, due to oil instability, cannot be operated at higher temperatures of 400 °C and that has implications for reducing their efficiency while using oil as an operating fluid has adverse environmental impacts. In order to minimize the fore mentioned disadvantages of using oil as a working fluid DSG technology has been developed. The DSG technology uses demineralized water instead of oil as a working fluid. This fact shows that DSG technology has the following advantages: achieving high temperatures (over 500 °C) and greater efficiency, the system is environmentally friendly, no heat exchanger is needed and a simpler configuration. However, the disadvantages of DSG technology refer to a necessary use a two-phase fluid which requires the use of high-pressure separators and a more complex system control by changing the intensity of solar radiation. To summarize, the key components of DSG technology are solar thermal parabolic collectors through which flows the two-phase fluid and a high-pressure separator which separates the working fluid phase (steam phase) from the working fluid. Master´s thesis analyzes the application of DSG technology for solar thermal power plants on the example of island Vis in Croatia, and the results show that this technology has more advantages than the technology of the standard solar thermal power plant.