The concept of solar resource knowledge is as old as mankind. Why therefore do we present it here as some recently discovered novelty? Why do we propose that after millennium of study and consideration that we have not fully explored this avenue of research, and why do we feel there is a need for further development of our knowledge? For several decades (if not centuries) mankind has been developing awareness of the solar resource, not just as something which lights our sky, ripens our food and warms our backs, but as a source for generating directly our everyday energy needs. For the applications of solar thermal heating, solar thermal power generation and solar photovoltaic electricity generation we need to know with higher precision, where, when and how much energy will we generate. Today the generation of photovoltaic solar electricity is starting to contribute to our daily energy consumption in excess of terawatthours per year. If the current trend in installation and development continues, by 2010, in Europe alone, more than 1% of electricity will come from photovoltaic solar energy. This is no longer a niche market but heralds the entry of photovoltaic solar energy into the realms of bulk power generation. At such level the reliability for planning, maintenance, forecasting, and management of solar electricity need the support of dedicated tools which allow us to efficiently use and manage the energy we are harvesting. The requirements for the development of better and more reliable methods for the management of the solar resource have been catalyzed over the last years by a sequence of events, such as several crises of electricity grid generation and distribution structures, recent adoption and implementation of successful national policies for renewable energies and an increased attention in the developing countries. These initiatives have been complemented with the availability of high resolution geostationary satellites such as the European Meteosat Second Generation, and improvement of data processing techniques. All these events have triggered demand for more accurate and timely solar energy resource information to support the deployment of renewable energy systems. In the same period of time, we have been witnessing evolution of a new commercial segment where companies providing renewable-energy related services have emerged from niche markets to consolidation of revenue-generating operations and investment forecasts for financial institutions. An improved knowledge of solar radiation is a vital precondition also for large-scale deployment of solar thermal heating and cooling technologies. Energy performances of buildings, daylighting, the design of windows and shading systems have also strong requirements regarding solar radiation, and other climatic data. The concepts presented within the monograph can contribute to many other fields of research. Integration of dedicated information from solar radiation with other technical and socio-economic data opened new opportunities for providing map-based specific analyses that assist policy makers, manufacturing and deployment industry, market development, investors, as well as users of all sizes. The experience from international agencies responsible for deployment of aid demonstrates that proper resource knowledge strongly determines success of international programs focused to renewable energy. This development sharpens definition of the future position of renewable energies in the global Earth observation programmes such as the intergovernmental Group on Earth Observations (GEO) and the Global Monitoring for Environment and Security (GMES). On the highest political level of the G8 group of industrialized countries, it was recognized that the top three science and technology priorities are agriculture, energy and Earth observations. Following this recognition, the GEO was established which has prepared a draft of the 10-year Implementation Plan for establishing the Global Earth Observation System of Systems (GEOSS). The improvement of the management of energy resources has been identified within this plan as one of the nine core areas where the Earth observation should provide clear societal benefits. Further, in the GEOSS it is recognized that access to accurate, reliable, affordable real-time weather and climate data from Earth observation systems, as well as predictive information derived from the modelled data, are critical for the continued stability and growth of the energy sector that is underpinning the world economies. One of the key principles of the GEOSS in data policy is full and open access to observations, metadata and products, while respecting the different data policies of GEOSS data contributors. The development and use of flexible, open, and easy to use community interoperable standards for metadata should be promoted. It must be possible to combine seamlessly spatial information from different sources and share it between many users and applications. The GMES is the initiative of the European Commission and European Space Agency that makes an important contribution to the GEO and the resulting GEOSS process. Photovoltaics, due to its direct dependence on the solar resource, is perhaps the most appropriate technology where management systems based on geographical information systems could be directly implemented to support its successful integration into existing energy and economic structures. Solar electricity management systems, handling complex and dynamic demand and supply structures at various geographical scales, can make a key contribution to guaranteeing the competitiveness of solar electricity and to avoiding future “blackouts” in the energy supply chain. They allow the development of clear concise demonstrations to increase the awareness and to clarify the impact of the introduction of solar electricity systems into our daily lives. This book addresses the rapid developments in the new field of solar resource knowledge as a reflection of growing needs of management of renewable energy resources. We have structured the content of this work as a set of contributions from the research, international and commercial institutions. The chapters discuss the availability of new primary data, basic concepts of research trends and approaches developed for providing higher resolution data and value-added products in an operational mode. Based on the experience from commercial and aid-providing sphere, individual and more generic barriers have been identified and solutions for overcoming them are discussed. The approaches exploiting geographical information systems, integrating spatial data and methods, outline directions for decision-making and management of distributed energy systems, considering regional and time variability at various hierarchical scales. The final contributions point out that the recent developments gave an impetus for complementing the traditional applications of Earth observation data by renewable energy programs.