The use of GIS in renewable energy that began in the 90s decade went through considerable progress and as a result various decision support tools were developed [1]. The GIS applications that were developed can be classified in three groups: GIS as a decision support tool for integration of renewable energies on a large scale and at a regional level, GIS for assessment of distributed energy generation and that connected to the electric network and GIS for decentralized production systems and autonomous production of electricity.

The GIS decision support tool for integration of renewable energies on a large scale and at a regional level (European Community) propose to analyze: evaluation of renewable energy potential (solar, aeolic, biomass and minihydraulic), its participation in relation to primary regional energy and the potential reduction of CO2 emissions [2]; evaluation of economic and potential renewable energies to identify regions of the European Community where the renewable sources were competitive at a determined risk [3]; evaluation of renewable energy potential, calculate the final use in the region and according to the scenario the insertion of a given renewable energy, makes its dimensioning and evaluates the economic impacts [4].

The GIS for evaluation of distributed generation, connected to the electric network considers the following renewable energy sources: aeolic, biomass and solar. The majority of GIS applications for aeolic energy deal with the optimum localization of the aeolic plants, consider the potential of the resource, the infrastructure for access and transmission lines and environmental restrictions and land use [5, 6, 7] , also Matthies [8]considers petroleum platforms, shipping routes and submarine lines for study of optimum localization of offshore aeolic farms. Marnay [9] developed a study of the use of photovoltaic solar energy installed on roofs of residences in the USA using GIS. The project included a municipality level resolution and considered the following variables: solar irradiation, average price of electricity and spatial distribution of the population.

A peculiar characteristic of biomass utilization is the necessity of transport from the local of cutting to a central transformer which makes the geographic proximity of the offer a determining factor for the final cost of the generated electric energy. Noon [10] developed a GIS for the Tennesy Valley, USA which considered the following variables: the characteristics of places of biomass offer, places of demand and transport costs, technical characteristics of the plants, forestry residues or cultivated forests, road networks and administrative limits. Voivontas [11] developed a work on the Island of Crete about the biomass potential for generation of electric energy. It deals with the combination of evaluation of the resources (theoric and/or available), the transport cost, the identification of optimum locals for biomass cultivation and the definition of the size of the plant for determining its economic competitiveness in the presence of conventional sources. Similarly in Spain one was developed IBERINCO [12].

SOLARGIS [13] is a GIS for rural electrification with renewable sources of energy. It is a paradigm of a GIS tool for this purpose as much for its completeness, relatively ample diffusion of its use as also for the periodic up-dating and improvements. The principal objectives of its development were: the demonstration of value of the GIS methodology for the development of the implantation of renewable sources for rural electrification, demonstration of its applicability in some target regions and proper construction of a GIS tool for analysis of the potential renewable sources [13]. The SOLARGIS methodology intends to obtain the best option for rural electrification, in isolated locals using renewable systems or not, being individual user or users connected to a local mini-network. The isolated residence could be electrified by PV systems, aeolic, gas generator, diesel group or interconnected to a network. A mini-network could be supplied by group diesel or hybrid aeolic-diesel system. The high potential regions are determined through comparison of equivalent costs of electrification of the energy systems considered. For this calculation, with a resolution of 1 km2, the following information is used: habitation density, mean annual global irradiation on the collector plane, mean annual wind velocity and distance of residence to electric energy network. SOLARGIS was applied in Tunis (Tunisia), Kairouan (Tunisia), Marrocos, Sicilia (Italia), Andaluzia (Spain), Murcia (Spain), Crete (Greece), Island of Santiago( Cape Green), Para (Brazil) and Karnataka (India).

NREL [14] is a GIS tool that is accessible via web that permits visualization of monthly mean solar irradiation with a spatial resolution of 40 km x 40 km (low) and in high resolution 10 km x 10 km for a collector plane facing the south, with the tilt in relation to the horizontal equal to latitude or the direct normal solar irradiation. In the same way it produces estimates of aeolic energy on an annual base, for low resolution (1/3 or 1/4 degrees) and high resolution cell size of 20-1000 m. Also the tool includes an estimation of the biomass potential derived from the different sources (agricultural residues, waste, forestry residues, among others).

RENEWABLE ENERGY ATLAS OF THE WEST [15] is a GIS tool that is accessible via web which synthesizes the data and maps on renewable energies for eleven American states that are situated in the West of America: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming. At a regional level (West American) the atlas shows, solar, aeolic, biomass and geothermic resources, the present mix of electricity supply, the renewable energy systems installed and information on public policies for stimulating the use of renewable energies. Also the present capacity of transmission lines, an estimation of charge growth in the region, aspects of soil use and environmental impacts are presented. In other sections the Atlas makes an in detail account of this information at state level.

PV-GIS [16] is a GIS application that is available in real time in web for calculating the photovoltaic solar energy potential in Europe. The user can navigate over solar irradiation maps and obtain the solar irradiance incident on a photovoltaic module positioned at different inclinations. A second application permits the obtention of the monthly mean daily profile for a given month and different positions and inclinations of the module. Finally a third application calculates the photovoltaic electric energy for a given configuration of PV systems that are localized in a given place.