Renewable energy sources such as solar and wind energy offer a large untapped potential for electricity production. The exploitation of these energies requires accurate knowledge of the resources and of their availability (in space and time) as well as accurate forecasts in the different phases of an energy system life cycle. For instance, the site selection process for development of large solar systems, such as photovoltaic on open land, require data on time-averaged values of solar irradiance from which basic economic assessments of a plant concept can be made. The paper illustrates the exploitation of Earth Observation data in this context. It describes the approach of setting-up a series of Web services that implement key features in Earth Observation data exploitation and illustrate their use through a complex application in the sitting of a solar power plant. The scenario is built on GEOSS interoperability and standard guidance.