Current Situation of Renewable Energy in Saudi Arabia: Opportunities and Challenges

The Kingdom of Saudi Arabia set out the national Vision 2030 that aims to accelerate efforts toward attaining sustainable development goals. In the framework of this Vision, Renewable energy plan has been set up and aims to ensure renewable energy growth that presents a key priority for achieving sustainable development. The present paper highlights the current situation of pollution and renewable energy in the Kingdom and presents the policies and actions stipulated in the Kingdom’s Vision 2030 to develop a renewable energy sector. In addition, the barriers facing the implementation of solar and wind energy in the Kingdom of Saudi Arabia has been carried out. Also, the different challenges facing the waste management has been presented. The paper concludes with some recommendations to develop the renewable energy sector in the Kingdom.

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Solar Energy
Solar energy has long been considered as a promising resource to produce energy. Saudi Arabia is one of the most fortunate countries of the sun, it has the longest sunshine hours with an average of 8.9 hour/day of sunshine and highest solar radiation intensity in the world with an average horizontal solar radiation of 6474 Wh/m 2 /day (Rehman, Bader et al. 2007). Figure 7 presents the solar irradiation intensity across the Kingdom of Saudi Arabia between 1999 and 2013. It can be seen that the high potential of solar irradiation has been registered across most provinces, it ranges from about 6000 to over 7000 Wh/m 2 /day. The highest potential has been registered mainly in Tabuk and Asir. A study was conducted by Erica et al. (Zell, Gasim et al. 2015) to analyze the Global Horizontal Irradiance (GHI), Direct Normal Irradiance (DNI), and Diffuse Horizontal Irradiance (DHI) data, based on one-minute measurements. These measurements were recorded in thirty stations distributed across the Kingdom covering the period from October 2013 to September 2014. Results showed that the annual average daily GHI ranged from 5700 Wh/m 2 to 6700 Wh/m 2 , whereas higher values are registered inland and lower values are registered along the coasts. These results, which is of particular interest to photovoltaic installations, indicate that installation of photovoltaic would perform very well in the kingdom. Annual average daily DNI ranged from about 4400 Wh/m 2 to over 7300 Wh/m 2 , whereas the highest values and clearest skies were registered in the northwest part of the country. These results, which is of particular interest to concentrating solar thermal installations, indicate that installation of concentrating solar thermal would perform very well. A review of the photovoltaic system for 32 sites of solar resources across KSA using three modes of a sun tracking system has been done by (Almarshoud 2016). Alharthi et al, conducted a study to analyze the solar potential in four different cities in the Kingdom, Riyad, Hafar Albatin, Sharurah and Yanbou (Alharthi, Siddiki et al. 2018). The obtained results showed that the GHI values are high at all of studied sites with relatively low variability and the highest annual average daily total of GHI and DNI of solar radiation was registered in Sharurah by 6682 Wh/m 2 and 6207 Wh/m 2 , respectively. In addition, Silica, used in PV cells fabrication, is found in abundance in the white rock/sand with the highest ratio of 99.5% in the Kingdom because it is mainly a desert landscape (Elani and Bagazi 1998). Therefore, the solar energy has a brilliant future and it can be a viable source of energy generation in the Kingdom. form of volcanoes and fumaroles, hot springs and geysers. Geothermal energy can be used in many forms such as direct use, electricity generation, space heating, heat pumps, greenhouse heating, and industrial usage. Geothermal resources have been classified based on their reservoir temperatures into low, intermediate and high enthalpy resources. Electricity generation is the most important form of utilization of high-temperature geothermal resources while low to medium resources are better suited for non-electric (direct) application resources. Electricity generated through geothermal systems are cost effective compared to other renewable energy sources and the land requirement for geothermal is the least among other renewables .
The kingdom of Saudi Arabia, has a plentiful resource of geothermal energy, mainly located at the western and southern parts. Saudi Arabia is among the most geothermally active countries in the Middle East. These resources are in relation with the general tectonic activity of the red sea and associated with a series of volcanic rocks and ridges. The geothermal power plants are not yet installed in Saudi Arabia, some direct-use low-grade geothermal applications are already installed in the ten last years as well as the refreshments and swimming pools that are already constructed in Bani Malik in Jizan area .
The geothermal resources of Saudi Arabia can be categorized as the following (Hussein, Lashin et al. 2013): -Low enthalpy resources (sedimentary aquifers): the temperature is less than 125ºC. These resources are represented by deep-seated aquifers encountered in thick sedimentary basins and there are located in the eastern part of the Kingdom. Deep drilled wells are required to get access to these resources.
-Medium enthalpy resources (hot springs): the temperature lies between 125ºC and 225 ºC. These resources are located in the western and southwestern coastal parts and represented by the shallow hot springs of hot surface water. However, They are unconfined targets with direct accesses to the subsurface hot anomalies through an open network of active faults and fractures (structure control).
-High enthalpy resources (basaltic lavas, Harrats): the temperature is greater than 225ºC. These resources are represented by volcanic eruptions, mainly basaltic in composition, that extend along the coastal part of the Red Sea at the western of Saudi Arabia. The country has approximately 80,000 km 2 of lava fields, known as Harrats.
The promising geothermal energy potential in the KSA is located in the Jizan province, which includes a number of structural-related hot springs with surface temperature from 46 °C to 78 °C ( it is located at the South-Eastern part of Jizzan and it is characterized by one main hot spring of high surface temperature up to 78 ºC with a good flow rate. It has been found that the heat flow, discharge enthalpy and subsurface temperature are 144 mW/m 2 , 318 kJ/kg and 133 ºC respectively. The estimated geothermal potential is 17.847 MWt providing a reservoir area of 1.125 km 3 .  Bani Malik: it is located at the Northeast part of Jizzan and it characterized by a very complicated-topographic area. One hot spring of low-surface temperature (45 ºC) has been found. jsd.ccsenet.

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Low price of natural gas: Natural gas is considered as a cleaner energy source than coal and oil in power generation. Saudi Arabia's holds the sixth largest natural gas reserves in the world and it is considered as a large producer of natural gas. Hence, the price at which natural gas is sold domestically in Saudi Arabia is one of the lowest in the world ($ 1.25/ mm Btu) and therefore, it contributes to rapid increasing of its consumption (Alturki 2016). The natural gas could present a serious and a strong competitor of renewable energy, due to its consideration as a clean energy source, its availability and its lower price in the Kingdom.  Missing legal and regulatory framework deters investors and impedes funding.  The amount of revenue generated from renewable energy cannot be similar to that produced from oil, and this will affect the state's ability to provide for welfare distributions (Ratikainen 2017).  The rareness of providing renewable energy education and training.  Lack of a skilled workforce, knowledge, expertise and experience laborers in renewable energy.  Due to the intermittent nature of solar energy and wind generation, it cannot be easily integrated and dispatched with the grid of a utility company (Patlitzianas, Doukas et al. 2006).

Recommendations
The initiatives of the Vision's 2030, stipulated by the Saudi government, are gearing towards efforts to achieve sustainable development goals. There is an intimate relation between renewable energy and sustainable development. Development can not be achieved without energy and sustainable energy is the cornerstone in sustainable development. Based on the analysis of the available renewable energy resources in the KSA, some recommendation are presented her to overcome the above barriers in order to expand the development of renewable energy sector:  Increasing capital flows for R&D which aims to develop renewable energy in the Kingdom and to find solutions to overcome the barriers to the development of renewable energy.  Interest-free loans for purchase of renewable energy equipment.  Municipal Solid Waste (MSW) management: an effective management of MSW requires a raising of public awareness that the waste, which they throw, has an important value, it is a raw material for other processes such as recycling, treatment and energy recovery. The government should work on the development of programs that spread awareness and knowledge to a wide audience through a variety of mass media and an organization of seminars. In addition, the private sector and governmental sector can play a crucial role by providing sufficient facilities related to different waste bins for proper household segregation as well as scheduled collection systems. Also, the integration of many waste management technologies such as pyrolysis, anaerobic digestion, waste recycling, WTE and value-added product (VAP) recovery. Moreover, the implementation of EPR (extended producer responsibility) which aims to bear the producer the responsibility of taking back, recycling and final disposal of their products and therefore decreases the environmental impacts of their products.  Regulating to limit greenhouse gas emissions from power plants such an "Introducing Carbon Capture and Storage (CCS) " technology in power plants and industrial facilities in order to prevent the carbon dioxide from entering the atmosphere. The advantage of this technology is that up to 90% of the CO2 emissions produced from burning fossil fuel for transportation, electricity generation and industrial processes can be captured by it.  Raising awareness on the importance and benefits of renewable energy by introducing and developing of Academic Curricula for Renewable Energy and increasing the scope of the study, degrees as well as schools dedicated to the fields of solar, wind and other exponents of renewable energy.  Training for engineers and policy makers to plan, design, operate and maintain renewable energy technologies since skills and capabilities are fundamental to an effective development and use of renewable energy technology.  A renewable portfolio standard (RPS) which is a regulation that requires an increasing production of energy from renewable energy sources. These policies can play an integral role in state efforts to diversify the energy mix, promote economic development and reduce emissions.  Resource Mapping of Renewable Energy Sources should be undertaken by the government in order to entice the interest of entrepreneur in exploiting the potential.

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Smart grid technologies: The fluctuations in renewable energy supply cause some mismatch between supply and demand. The smart grid technologies should be developed and deployed in order to support grid connections with renewable energy and enhance the use of renewable energy.  Fossil fuel substitution by solar energy in desalination plants: The production of 1000 m 3 of freshwater per day requires 10 000 tons of oil per year (Kalogirou 2005). However the KSA is largest producer of desalinated water in the world. Therefore, the use of a solar energy in desalination plants can be critical part in reducing the consumption of fossil fuel and reducing GHG emissions.

Summary
The Kingdom of Saudi Arabia is highly rich in renewable energy resources including solar, wind, geothermal and hydropower. However, the country relies on fossil fuel to feed the energy demand and the share of renewable energy in the final consumption is very small. The transport and the industry sectors are by far the most energy-intensive in the country while the agriculture and the forestry sector is the lowest one. The country suffers from a high rate of pollution and it is among the highest polluted countries in the world due to heavily dependence on fossil fuel, climatic conditions, desalination plants, growth population and high energy demand. KSA set out the Vision' 2030 that aims to achieve sustainable development in its three dimensions, economic, social and environment. The sustainable energy presents an essential key for a successful sustainable development and therefore, the development of renewable energy can support the efforts aimed to attaining the SD Goals. However, The sector of renewable energy, in its current situation, faces many technical, economical gauntlets and challenges. The main impediments can be categorized into climate, lack of awareness of the importance and potential of renewable energy, and abundance of fossil fuels and its low price. Many actions has been taken by the Saudi government to decrease the energy consumption such as the increasing of electricity price. However, the country should take more actions such as Resource Mapping of Renewable Energy Sources, Renewable portfolio standards, developing of Academic Curricula for Renewable Energy, smart grid technologies, increasing R&D in the field of renewable energy technologies and regulating to limit greenhouse gases emissions.