Analysis of Turkey's Solar Energy Potential in Different Regions

Makale Tarihçesi: Geliş tarihi: 08.12.2021 Kabul tarihi: 05.02.2022 Online Yayınlanma: 23.02.2022 Günümüzde küresel enerji krizi ve artan çevre kirliliği ile birlikte enerjinin ülkelerin gelişmişlik düzeylerini belirlemede en temel faktörlerden biri olduğunu göstermektedir. Özellikle pandemi döneminde günlük hayatın her alanında enerjiye duyulan ihtiyaç ve teknolojik araçların kullanımının artması, enerji kaynaklarının ve enerji üretim sürecinin önemini bir kez daha göstermiştir. Son zamanlarda yapılan araştırmalar, enerji ihtiyacı ve çevre kirliliğinin giderek daha fazla ön plana çıkmasıyla, yenilenebilir enerji kaynaklarının tüm dünyada geleneksel enerji kaynaklarının (fosil yakıtlar) yerini aldığını göstermektedir. Yenilenebilir enerji kaynakları kullanılarak fosil yakıtların kullanımı sonucu açığa çıkan CO2 gazının çevreye verdiği zararı en aza indirmek mümkündür. Güneş ve rüzgâr gibi doğal kaynaklardan elde edilen enerji, çevreye verilen zararı en aza indirmesi, tükenmez bir enerji fırsatı sağlaması ve temiz bir enerji kaynağı olması nedeniyle fosil yakıtlara kıyasla önemli bir yere sahiptir. Yenilenebilir enerji kaynaklarından biri olan güneş enerjisi, herhangi bir yakıt veya hareketli parça gerektirmemesi, kullanım sırasında atık madde üretmemesi, çevre dostu olması, bol ve ücretsiz olması nedeniyle oldukça tercih edilen bir enerji kaynağıdır. Türkiye'nin coğrafi konumu güneş enerjisi kuşağında yer almaktadır. Bu nedenle hemen her bölgede kurulabilecek bir güneş enerjisi santralinin bölgesel enerjiye veya ülke ekonomisine katkı sağlayabileceği öngörülebilir. Bu çalışmada Türkiye'nin yedi farklı bölgesinden seçilen Siirt, Adana, Erzincan, Kırşehir, Kütahya, Balıkesir ve Amasya illeri için güneş enerjisi potansiyelleri araştırılmıştır. Araştırma sonuçlarına göre, farklı iklim koşullarında (kar, yağmur, bulut vb.) iller olsalar da benzer güneş radyasyon yoğunluklarının olduğu tespit edilmiştir. Bu da Türkiye'nin güneş enerjisi potansiyeli açısından ne kadar önemli olduğunu göstermektedir. Anahtar Kelimeler: Güneş enerjisi Güneş enerji potansiyeli Güneş ışınımı


Introduction
Nowadays, energy is one of the important factors which determine the level of developing countries (Taşkın and Korucu, 2014). The need for energy is increasing day by day due to reasons such as increasing population, industrialization, and pandemic (Şendemir, 2021). Many researches show that not only energy consumption is very important but also energy production is very important because of the use of energy in almost every aspect of our lives such as electronic vehicles, factories, electric cars, and street lighting in daily life (Kaya et al., 2018;Bilhan and Emikönel, 2021). Turkey which is one of the developing countries, the need for energy is increasing day by day (İzgeç, 2020). For this reason, many new renewable energy sources are developed and landed in many different areas.
As it is known, fossil fuels are widely used in energy production (Kaya et al., 2018). However, it also brings many negative consequences such as global warming, air pollution, formation of acid rain, and climate change caused by the CO 2 gas released by the use of fossil fuels (Dinçer, 2011;Atakul et al., 2015;Kılıç, 2015). However, it also brings back many negative outcomes such as global warming, air pollution, formation of acid rain, and climate change by the use of fossil fuels (Dinçer, 2011;Atakul et al., 2015;Kılıç, 2015). According to the prediction of many researchers and the World Energy Form, the limited reserves of fossil fuels will be exhausted in the next century due to the usage of coal, oil, natural gas, etc. in many areas (Kumar et al., 2010;Dinçer, 2011). In order to prevent the damage of fossil fuels to the environment and due to the limited fossil fuel resources, renewable energy sources have been more attractive in the last 50 years (Eltas, 2020;Bilhan and Emikönel, 2021).
The biggest advantage of renewable energy, it consists of natural processes and is available the next day (Kocakuşak, 2018;http://yegmweb.yegm.gov.tr/genc_cocuk/Yenilenebilir_Enerji_Nedir.aspx, 2021). The most popular renewable energy sources are hydro, sunlight, wind, biomass, geothermal, and hydrogen. Also, it is focused on the energy which is produced by the wave in recent studies (Yaman et al., 2019;Albayrak Karadağ, 2020). Solar energy, which is one of the popular renewable energy sources, has an important place in energy production all over the world (Bilhan and Emikönel, 2021). Sun is an energy resource that basically consists of 92 % hydrogen and 8 % helium and some other elements. The fusion reaction occurs as a result of the conversion of hydrogen gas in the core of the Sun into helium gas. The radiant energy released by the formation of the fusion reaction is solar energy (İnan et al., 2018; https://enerji.gov.tr/bilgi-merkezi-enerji-gunes, 2021). In other words, the energy reflected from the sun on the 1 m 2 surface of the Earth in watts is solar energy (Bilhan and Emikönel, 2021). The intensity of solar energy outside the atmosphere is approximately 1370 W/m 2 , but the amount reaching the earth varies between 0-1100 W/m 2 due to the atmosphere (Yolcan and Köse, 2020; https://enerji.gov.tr/bilgi-merkezi-enerji-gunes, 2021). According to the International Energy Agency (IEA), the solar energy which comes from the sun to earth in 90 minutes is enough to meet the energy need of the whole world for a year (Kılıç, 2015). This type of energy, which is obtained naturally during the hours of the sun, has started to be preferred in almost every field due to its unlimited nature and being an inexhaustible resource for centuries (Bulut et al., 2018;Eltas, 2020). The solar energy source has an important place in world energy demand. The International Energy Agency estimates that approximately 11% of global electrical energy production will be provided by solar energy in 2050 (Dinçer, 2011;Kırbaş et al., 2013).
In this study, the sunshine duration and solar radiation intensities of the provinces of Siirt, Adana, Erzincan, Kırşehir, Kütahya, Balıkesir, and Amasya, which we selected from seven different regions, were examined in accordance with the data obtained from the Ministry of Energy and Natural Resources to give information about the solar energy potential of our country. There are many studies on solar energy potential in the literature such as Çakmak and Altaş examined the solar energy data obtained from four different sources for the province of Erzincan in their study. Also in their study, the solar energy potentials of Erzincan and Germany were compared. As a result of the study, it was concluded that the province of Erzincan has a higher solar energy potential than Germany and that much more energy can be produced if the PV plants established in Germany are installed in Erzincan (Çakmak and Altaş, 2016). Aksungur et al. investigated the solar energy potential in Turkey and the world in their study and examined and compared the radiation intensities of the provinces of Isparta, Ankara, Erzincan, Birecik, Balıkesir, Yozgat, Yalova, which they selected from different regions of our country in the sunbelt. As a result of their research, they determined that there is not a big difference between the radiation values (Aksungur et al., 2013).

Solar Energy Potential in Turkey
Turkey is located between 26 0 -45 0 east meridians with 36 0 -42 0 northern parallels and has a surface area of 783,562 km 2 . Turkey has a high solar energy potential because of its geographical location.  is observed that the global radiation value reaches its highest value in June with 6.57 KWh/m 2 -day.
The average daily radiation intensity of Turkey on a monthly basis is 4.18 KWh/m 2 -day and the annual average total is 1524.18 kWh/m 2 -year (4.18x365) global radiation values. In Fig. 2 (b), it can be observed as while the highest sunshine duration was 11.31 hours in July, the lowest sunshine duration was 3.75 hours in December. Turkey's average daily sunshine duration on a monthly basis is 7.49 hours-days and it has an annual average total of 2736.89 hours-years (7.49x365) sunshine duration.
Considering all these data, it is seen that Turkey has high solar energy potential.

Siirt Province
The highest solar energy potential among the Regions of Turkey is the South-eastern Anatolia Region.
The solar energy obtained from this region, where the sunbeam comes at a right angle most of the year, is 1460 KWh/m 2 -year. The annual sunshine duration of the South-eastern Anatolia Region is 2993 hours (https://www.incitas.com.tr/bilgi-merkezi/blog/turkiyede-gunes-enerjisi-potansiyeli, 2021).
The average global radiation values and sunshine durations on a monthly basis for the province of Siirt where is located in the Southeastern Anatolia Region are given in Figure 3 (a) and (b), respectively (YEGM, 2020). Fig. 3 (a) shows the highest radiation intensity is 6.78 KWh/m 2 -day in June and the lowest radiation intensity is 1.79 KWh/m 2 -day in December. Also, the monthly average sunshine duration of Siirt have been shown in Fig. 3 (b), too. As it can be seen from it, the highest value is 11.78 hours in July and the lowest value is 3.84 hours in January. these values, Siirt is in an important position among the places where its solar energy potential will benefit from solar energy (Bulut et al., 2018).

Adana Province
The Mediterranean Region is the second region with the highest radiation intensity in Turkey. In this region where the number of sunny days is high, the solar energy obtained is 1390 KWh/m 2 -year and the total sunshine duration in a year is 2956 hours (https://www.incitas.com.tr/bilgimerkezi/blog/turkiyede-gunes-enerjisi-potansiyeli, 2021) The average global radiation values and sunshine durations on a monthly basis for the province of Adana where is located in the Mediterranean Region are given in Figure 4 (a) and (b), respectively (YEGM, 2020). Fig. 4 (a) shows the highest radiation intensity is 6.68 KWh/m 2 -day in June and the lowest radiation intensity is 1.81 KWh/m 2 -day in December. Also, the monthly average sunshine duration of Adana have been shown in Fig. 4 (b), too. In figure 4 (b), the sunshine duration of Adana province has the lowest sunshine duration with 4.21 hours in December, it reaches the highest value with 11.77 hours in July. respectively (YEGM, 2020). Fig. 5 (a) shows the highest radiation intensity is 6.37 KWh/m 2 -day in June and the lowest radiation intensity is 1.55 KWh/m 2 -day in December. As it is seen in Fig. 2 (b), the sunshine duration has a minimum of 3.27 hours in December, it reaches a maximum value of 10.67 hours in July. hotter summer season compared to the surrounding provinces (Çakmak and Altaş, 2016). This means that Erzincan can benefit from more sun during the summer months.

Kırşehir Province
The Central Anatolia Region is the fourth region with high solar energy potential  Balıkesir has an annual average total of 2690 hours of sunshine and an annual average total of 1421 KWh/m 2 -year radiation intensity.

Amasya Province
The Black Sea Region has the lowest monthly average global radiation values. The Black Sea Region has an average annual radiation intensity of 1120 KWh/m 2 -year. The total sunshine duration in one year is 1971 hours. Due to its geographical location, the number of sunny days is low in this region where the amount of precipitation is high (Bulut et al., 2018;Doğanay, 2021).Therefore, the region where we can benefit least from solar energy is the Black Sea Region (Bulut et al., 2018).  Fig. 9 (a) is examined, it is observed that the radiation intensity of Amasya is the highest in June with a value of 6.14 KWh/m 2 -day, and the lowest in December with a value of 1.36. In the Fig. 9 (b), it is seen that while Amasya has the minimum sunshine duration in December with 3.19 hours, it reaches the maximum sunshine duration in June with 10.14 hours.
It is observed that Amasya has an annual average total of 2431 hours of sunbathing time and an annual average total of 1396 KWh/m2-year global radiation value. According to these values, Amasya is more fortunate than many other provinces in the region due to its geographical location (Kaynar, 2020). Ranking fourth in the region in terms of sunshine duration, Amasya reveals that it is the most suitable place to benefit from solar energy in the region (Kaynar, 2020). The radiation intensities and sunshine durations of the regions are summarized in Table 1 (https://www.powerenerji.com/turkiye-gunes-enerjisi-potansiyel-haritasi-bolge-il-guneslenmesureleri.html, 2021). In Turkey, which is located in the sun belt, the solar energy potential decreases as we go from south to north (Doğanay, 2021).

As it is seen from all Figures, the Southeast Anatolia
Region has the highest solar energy potential and the Black Sea region has the least solar energy potential. This is because the Southeastern Anatolia Region is closer to the equatorial region and the Black Sea Region is the farthest from the equatorial region (Taşova, 2018).  The Mediterranean Region 1390 2956 The Eastern Anatolia Region 1365 2664 The Central Anatolia Region 1314 2628 The Aegean Region 1304 2738 The Marmara Region 1168 2409 The Black Sea Region 1120 1971 In This shows how important Turkey is in terms of solar energy potential. It can be predicted that a solar power plant that can be established in every region can contribute to regional energy or the national economy.

Result and Discussion
Turkey's solar energy potential is quite high due to its geographical location and location in the sunbelt. In this study, it is aimed to reveal the importance of solar energy and to give detailed information about the solar energy potential of Turkey. For this purpose, provinces (Siirt, Adana, Erzincan, Kırşehir, Kütahya, Balıkesir and Amasya) were randomly selected from seven different regions of Turkey.
In Table 3, the monthly global radiation values (KWh/m 2 -day) and monthly sunshine duration (hours) of Siirt, Adana, Erzincan, Kırşehir, Kütahya, Balıkesir and Amasya are listed. All monthly values are shown in Figure 10 and Figure 11, respectively. In Figure 10 and 11, the x-axis shows the months as a number such as 1 is for January, 2 is for February, 12 is for December. In Figure 10, the y-axis shows global radiation values. In Figure 11, the y-axis shows monthly sunbathing durations by hours.

Conclusion
The increasing air pollution and fewness of fossil fuel sources have increased the interest in new environmentally friendly sources such as renewable energy sources. Solar energy is a type of energy obtained from natural sources and also it is ecofriendly. It is important to get best benefit with use of this type of energy, which provides unlimited energy. Turkey is located in the sun belt due to its geographical location. So, it has a very high solar energy potential according to many other countries.
Turkey has an average daily radiation intensity of 4.18 KWh/m 2 -day on a monthly basis and an annual average total of 1524.18 KWh/m 2 -year (4.18x365) global radiation value. The average daily sunshine duration of Turkey on a monthly basis is 7.49 hours-days and has an annual average total of 2736.89 hours-years (7.49x365). Also, the solar energy potential increases as from north to south. The Southeastern Anatolia Region, where the sun's rays are the most, is in the first place among the regions that will benefit most from solar energy. Then Mediterranean Region where the number of sunny days is high comes in second place. Then Eastern Anatolia Region, Central Anatolia Region, Aegean Region, Marmara Region and Black Sea Region come, respectively.
In this study, not only has given more detailed information about the solar energy potential of Turkey, but also solar energy potentials of Siirt, Adana, Erzincan, Kırşehir, Kütahya, Balıkesir and Amasya were investigated and compared. Datas which were selected for seven different regions obtained from the Ministry of Energy and Natural Resources were used in this study. According to the result of the research, radiation intensities in all provinces are close to each other. However climatic conditions (such as snow, rain, etc.), landforms, floras are different from each other. These features indicate Turkey's unique structure. Although Turkey has a high solar energy potential, other factors are effective in utilizing solar energy, too. Considering Turkey's radiation potential along with all these factors, it can be predicted how a solar power plant that can be established in every region can contribute to regional energy or the economy of the country. In future studies, it is planned to examine the establishment of a solar power plant and grid connection in a suitable region with using the information in this article.

Statement of Conflict of Interest
Authors have declared no conflict of interest.

Author's Contributions
The contribution of the authors is equal.
*This study was presented as a summary paper at the International Conference on Engineering, Natural and Applied Sciences (ICENAS'21) held online on 24-26 November 2021.