## 2 Energetic Stability and Renewable Energy Sources  
Adequate global energy consumption is one of the most important factors for achieving an adequate global average level of quality of life. However, this is not an easy goal to achieve, as the current global energy mix is 80% fossil fuel based [4]. Such massive dependence of fossil fuels rises issues which are not of newer date such as accessibility to fossil fuel and its uneven distribution, as well as altering the climate [5]. Fossil fuel is a negative solution for climate with respect to its greenhouse gases emission [6]. The extraction of fossil fuels is the biggest cause of climate change, which is furthermore not only an environmental issue, but also a social one [7]. Discussions regarding reducing CO\({}_{2}\) emissions and restraining climate change are of global significance, and one of the very important topics the society faces.  
It is also crucial to keep stable energetic supply. Renewable energy sources (RES) are considered as a suitable alternative which minimizes environmental impacts and generates minimum secondary waste [8], as well as offers efficient solution for sustainable development [9].  
Even though most of energy consumption in the world is provided by fossil fuels [10], part is still supplied from energy sources such as renewables and nuclear energy [11]. Nuclear energy is produced without CO\({}_{2}\) or methane emission, but is still not a sustainable energy source as it is not clear how to deal with the nuclear waste [12; 13]. That leaves renewable energy sources as a choice for sustainable energy future [14]. Reports show that share of renewables in a global energy production is growing every year e.g., [15]. Renewable energy mix include solar, thermal, photovoltaic, bioenergy, hydro, tidal, wind, wave and geothermal energy [16; 17].  
As it is always clearer that humans and their actions are the primary cause of climate change (There is almost unanimous consensus regarding this topic among climate scientists. More than 97 percent of them understand that humans are the primary cause of climate change [18]), renewable energy sources permanently rise the attention of general public, policy makers, as well as scientific community. Renewable energy sources provide energy in different areas. One of their most valuable contribution is in electricity generation [19; 20]. Technologies regarding storage and supply of electricity got in this way are constantly improving [21; 22; 23]. Furthermore, solutions including renewable energy and transportation are increasing [24]. Renewable energy solutions are also contributing in heating and cooling systems [25].  
According to data of REN21 [15], participation of renewables in general global energy consumption was around 18%: 7.5% is covered by traditional biomass, while 10.6% is covered by modern renewables. Further division within modern renewables shows that 4.2% of total final energy consumption comes from biomass/solar/geothermal heat, 3.6% hydropower, 2% wind/solar/biomass/geothermal/ocean power and 1% comes from biofuels for transport. The rest is covered from fossil fuels (around 80%) and nuclear energy (around 2%). The share of renewables in total final energy consumption rose in period 2006-2016 for 2.3% (Traditional biomass did not increase its share, while modern renewables increased their share for 4.5%) [15] (p. 32). Renewable energy is mostly contributing in the sector of power consumption with at around a quarter of total power consumption. Renewables participated with around 10% in total energy used for heating and cooling, as well as with around 3% in the energy used for transport [15] (pp. 32-33).