Energy efficiency in the framework of the energy trilemma will guide to energetic policies focused on economic growth and development of the Developing Countries. Many of the International Organizations: such as the International Energy Agency (IEA) agreed to promote the rational use of the expressed sources in reducing energy intensity to mitigate accelerated climate change through the reduction of CO2 emissions as agreed at COP21 in Paris.

The transition from Oil to Natural Gas in Argentina was marked in the years 1994 - 1999, because of an intense productive activity, causing an exponential increase in consumption. Although, if the Natural Gas less pollutant than oil, currently, the change in the matrix, did not report a reduction of C02 as expected due to the lack of technology and the rational use of these sources as energy. This implied that currently, the share of fossil fuels in the energy matrix more than 84 % above dealer, with nearly 51.1 % of Natural Gas.

Therefore, the study focuses on the energy security of Argentina's growing energy demand and environmental Commitments; through, increased energy efficiency with the assumptions in reducing Energy Intensity towards a more sustainable energy trilemma to the medium and long term. It is worth mentioning that the reduction of the total demand of a country is associated with levels of energy efficiency. In our case, by 2035 an increase in energy efficiency of 19% could we reduce demand 36%; that is, a reduction in energy intensity of 29 % compared to 2015.

The scenarios with reduction in energy intensity by 2035 are 1 %, 1.5 % and 2 % annually, which will involve a reduction in the consumption of primary sources and consequently a reduction in CO2 emissions of 5.3%, 14.4% and 20.2% respectively in each case. In this way, we could diversify the energy matrix progressively, towards more sustainable developments.

To project the demand for primary sources from 2015 to 2035, it is necessary to design a macro-econometric model, based on an annual GDP growth of 2.77% and the projection of energy intensity according to 3 proposed scenarios. Then the relationship population country / world, will enable us to project the maximum allowable CO2 emissions by 2035, with a commitment not to increase the temperature more than 2 °C by 2100 and the commitment of Argentina with COP21 to reduce 15% CO2 emissions by 2030.

Finally, the overall objective of the research will be to adjust energy policies of the country in the medium and long term through of the Evolution of Energy Matrix Primary versus the Evolution of Energy Efficiency, under the precept of securing the demand and comply with COP 21 under a more sustainable energy trilemma.

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