## 1 Introduction  
In recent decades there has been a renaissance in renewable energies due to the proximity of the exhaustion of fossil energy sources, the progressive increase in their cost, the environmental problems derived from their exploitation, transport and consumption, and, of course, due to the great external dependence of many countries on this type of energy sources, which also implies that energy supply and the economy are directly linked to the geopolitical instabilities that may exist between different countries. Renewable energies, through their different technologies, are playing a fundamental role in achieving sustainable development from the energy point of view and in meeting objectives against climate change and environmental degradation, objectives expressed by different international organisations and institutions in recent years, such as the United Nations and its Sustainable Development Goals [1], specifically Goal 7, which aims to ensure access to affordable, reliable, sustainable and modern energy for all. The InternationalRenewable Energy Agency (IRENA) has set a target of 57% of the world's energy to be produced from renewable energy sources by 2030, compared to 26% at present [2]. This increase in the share of renewable generation, which the European Union, through the European Green Deal and Green Recovery, is taking to an even greater extreme with the proposal for zero greenhouse gas emissions by 2050, means that this decade will be seen as the one in which a major global energy transformation will take place [3]. A pathway to net zero emissions (PNZ) is therefore proposed, which requires the electrification of systems that are currently based on fossil fuels, such as air conditioning, the transport sector, and the mechanisation and activities of the secondary and primary sectors. Thus, the challenge at the energy level is not only to generate the electricity currently required in a cleaner way, eliminating polluting energy sources from the generation mix, but also to further increase electricity generation capacity in order to accommodate within the electricity system sectors that require a high demand for energy and which are currently based on other polluting energy sources. Renewable energies will therefore have to provide the energy supply required for all current activity. These renewable energies experienced an increase of 9.1% in installed capacity in 2021, which grew by 257 GW according to IRENA, a growth trend that was also experienced in 2020, which has shown its resilience in an adverse context such as the pandemic experienced due to Covid-19 [4; 5]. Solar energy is, within the framework of renewable energies, one of those that can stand out for having greater technological development and greater possibilities of competing in the market. Specifically, in 2021, solar PV energy was the leading renewable energy technology and the most installed worldwide. New PV capacity in 2021 was 175 GW, an increase of 21% compared to 2020, exceeding 100 GW for the fourth consecutive year and reaching a cumulative 942 GW [4; 5; 6]. This technology is driving the largest increase in renewable energy, overtaking wind in absolute terms [2; 4]. It is an inexhaustible source of energy, it is distributed all over the world and it is one of the main technologies on which users are focused in order to meet the objectives of reducing polluting emissions [7; 8]. In recent years, the technological development of this type of installation, together with the reduction in prices that has taken place (although the current crisis has reversed this trend in recent months), has meant that its use has become increasingly widespread [4; 7; 9; 10; 11; 12; 13].