World energy demand is growing tremendously. Global energy demand jumped by 2.1% in 2017--twice the 2016 rate [1]. As a result, carbon dioxide emissions also rose by 1.4% despite having held steady for almost three years prior to 2017 [1]. Consequently, the environmental issues associated with use of fossil fuels have also been exacerbated. Acid rain and global warming are examples that threaten both the earth and humanity. Exhaustion of limited fossil fuel reserves, escalating impacts of climate change, increased power consumption due to population and industrial growth, and oil politics pricing are dire challenges that have resulted in the push toward clean and renewable energy resources [2].<br />Recently collected data indicates that switching gradually to renewable energy resources and decentralizing power generation has become a major goal of all the developed and a number of emerging countries around the world [3]. However, the cost of electric power generated from renewable energy resources must be able to compete with fossil fuel-based electricity generation in order to be considered a serious alternative to conventional power plants. Consequently,<br />developing highly efficient renewable energy systems that offer a competitive price advantage over conventional generation systems is the main goal of research and development efforts toward next-generation photovoltaic (PV) systems [4].<br />Renewable energy will exceed 60% by 2045. The anticipated renewable energy growth will gradually increase to reach 920GW by 2022, whereas the total expected power under the accelerating case might increase to more than 1,150 GW by 2022. Thus, according to the U.S. Energy Information Administration (EIA), the electrical power generated from renewable resources will see a strong expansion rate of 43% in 2022, a rate that was only 12% from 2016 to 2017 [5].<br /> <br />The renewable energy record performance forms the bedrock of future growth expectations. Therefore, the forecasted renewable energy curve illustrates that generated power, Figure 1 illustrates the global renewable energy capacity growth from 2007 to 2017. This figure indicates that a significant portion of renewable energy generation is still based on hydropower, but there has been a steady growth in wind and solar generation with a slight rise in biomass energy. In 2017, the cumulative additions to worldwide renewable energy generation reached 178 GW while the same figure was 138 GW by the end of 2013. Hence, the renewable energy growth rate was around 29% in the period of four years, i.e., 10 GW per year. Moreover, it can also be clearly seen that the total renewable generation capacity more than doubled in a period of ten years thanks to capacity additions in wind and solar energy.<br />The renewable energy record performance forms the bedrock of the future growth expectation. Therefore, the forecasted renewable energy curve illustrates that generated power from renewable energy will exceed 60% by 2045. The projection also indicates that the world will no longer count on fossil fuels as a conventional resource. The anticipated renewable energy growth will gradually increase to reach 920GW by 2022, whereas the total expected power under the accelerating case might increase to more than 1,150 GW by 2022 [6]. Thus, according to the U.S. Energy Information Administration (EIA), the electrical power generated from renewable resources will see a strong expansion rate of 43% in 2022, a rate that was only 12% from 2016 to 2017 [6].Figure 2 world energy consumption by Source (1990-2045).<br />In general, as stated by eia, most generated power will come from PV solar systems and will present the highest capacity additions for the next five years starting from 2019 to 2024, mainly in China and India [7]. The following subsections introduce the various types of available renewable energy and their tradeoffs.<br /><br />م.م. علي جواد كاظم