The production of energy from RES is one of the most dynamic and fastest growing sectors worldwide, due to:

• the urgent need for substantial increase in RES capacity, in accordance with the Kyoto Protocol
• the high RES potential (wind, hydroelectric, solar, biomass, etc.), which can be utilized under viable techno-economic terms
• the gradual exhaustion of conventional energy resources ( ie oil, natural gas)
• the availability of reliable technological solutions for the commercial utilization of the inexhaustible domestic RES resources, in an environmentally friendly manner.

The obvious benefits from the steadily growing activity in the RES sector are:

• the substantial reduction of air pollutant emissions (CO₂, NO_x, SO₂, etc) and, subsequently, the reduction of the large adverse effects on the environment.
• the reduction of the very high dependence on conventional fuels
• the creation of a decentralised system of energy production units (production close to consumption), with beneficial effects on the safety of energy supply and on energy efficiency
• the creation of a substantial number of new employment positions, during construction, operation and maintenance of the RES units, both at the regional and the local level.

The above benefits also constituted the basis for the gradual formulation and application of a legal and financial support framework for RES, aiming at the activation of public and private initiatives in this sector. The RES framework takes into account the environmental cost (externalities) of conventional fuel technologies, as well as the established, at the national and European level, principal that the “polluter pays”.

Wind Energy: the kinetic energy which is produced by the power of the wind and is converted, by wind turbines, into usable mechanical energy and/or electricity.

Hydraulic Energy: the energy of waterfalls, which is exploited by small hydroelectric plants (up to 15 MW in installed capacity), to generate electricity or to convert it into usable mechanical energy.

Biomas: the biodegradable fraction of products, wastes and residues from agriculture, including vegetal and animal matter, forestry and related industrial activities, as well as the biodegradable fraction of industrial wastes, municipal sewage and municipal solid wastes.

Biogas: the fuel gas produced from biomass and/or from the biodegradable fraction of industrial and domestic waste matter (landfills, wastewater treatment plants, etc.), that can be purified and upgraded to natural gas quality, to be used as a biofuel.

Solar Energy, which encompasses the following:

• Active Solar Systems: convert solar radiation into heat.
• Bioclimatic Design and Passive Solar Systems: Concern architectural solutions and the use of suitable construction materials for the maximisation of the direct use of solar energy for heating, air conditioning or lightning of interior spaces.
• Photovoltaic Solar Systems: convert solar energy directly into electricity.

Geothermal Energy: the thermal energy which comes from the earth’s interior and manifests itself in natural steam releases, in surface or underground hot waters

• They are practically inexhaustible sources of energy (sun, wind, rivers, organic matter, etc.) and contribute to reducing the dependence on depletable conventional energy resources, such as oil, natural gas, coal, etc.
• Their exploitation/utilisation is widely accepted by the general public, due to their environment- and human-friendly nature.
• They constitute (together with energy conservation) the most ecologically sound solution for the effective reduction of carbon dioxide emissions and the combating of the greenhouse effect. In addition, by replacing energy generation plants which use conventional fuel resources, they lead to a reduction in the emissions of other pollutants as well, such as sulphur oxides which cause acid rain, nitrogen oxides which cause photochemical smog, airborne particulates, etc.
• They are domestic sources of energy and contribute to strengthening the energy independence and security of supply at the national level.
• They are geographically dispersed, leading to the decentralisation of the energy system, making it possible for energy needs to be met at the regional and local level, thus relieving the pressure on infrastructure systems (electricity grids, roads, etc.) and reducing the losses from energy transmission.
• They provide opportunities for the rational use of energy sources, because they cover a wide range of users’ energy needs (i.e. solar energy for low temperature heat, wind energy for electricity production, etc.).
• They usually have low operating costs, which are not influenced by fluctuations in the international markets and especially in the prices of conventional fuels (crude oil, natural gas, coal).
• RES installations are usually designed to meet the specific energy needs of users/consumers, both at the large or at the small scale, and they have relatively short materialisation times, thus allowing quick response of energy supply to energy demand.
• RES investments create a significant number of new jobs, especially at the local level.
• In many cases, they can become a catalyst for the regeneration of economically and socially depressed areas and a focal point for local development, through the promotion of relevant investments (for example, greenhouses using geothermal energy, district heating of local communities and towns via hot water/steam produced by the energy exploitation of agricultural and forestry biomas, etc.).