Figure 1. Solar Radiation Map of Turkey
In this study, the comparative analyzes of solar Photovoltaic (PV) energy production potential between Van which is situated in the far east of Turkey, and Antalya which is situated in the south of Turkey, using dynamic PVSOL Expert 6.0 simulation tool regarding annual temperatures and solar radiation capacity was performed. The objective of this paper is to explain and help in better understanding of which part of the country should be invested regarding solar energy generation. Ignoring the average annual temperatures, Antalya seems to be advantageous since, the solar radiation capacity is high, but considering the temperature’s negative effects on the solar panels, the advantages of Antalya decreases. Since, the average annual temperatures in Antalya are higher than Van, the payback period of the investment increases by 3.44%, although the solar radiation capacity is much more than in Van. Under the same conditions, the solar energy production potential difference between the two cities is only 6.25%. As can be clearly seen from the simulation results performed in this study, there are not too much differences regarding solar energy production potential between Antalya and Van. Related to the cost of an investment for a solar power plant investment, both the cities can be selected.
Today the costs of the energy sources are increasing directly proportional with the growing population in the world. The term of the energy sustainability has become very popular around the world due to the running out of the fossil fuels in the near future. It is a fact that the usage possibility of the fossil fuels will be no more available for the next decades. Besides, the fossil fuels have many harmful effects on the environment such as CO2 emissions into atmosphere that contribute to the global warming and climate changing. Instead of the use of the traditional fuels, the renewable energy sources such as wind or solar energy should be supported and promoted by the governments for the growing energy demands [1-2].
Renewable energy sources are unlimited, inexpensive and very clean compared to the fossil fuels. One of the main advantages of the renewable energy sources is that there is tremendous economic opportunities for the countries that invent, manufacture and export clean energy technologies. Therefore, the importance of the renewable energy sources has increased remarkable in last decades. The solar energy which has an important place among the other renewable energy resources is the most abundant and infinite energy source in the world and it is usable in its direct and indirect forms. The first and foremost advantage of solar energy is that, except panel production processes, it does not emit any greenhouse gases into the atmosphere and thus it does not contribute to the climate changing around the world [3]. Turkey is one of the countries with the highest solar energy potential in Europe, but it fails to convert such a big potential capacity into electricity generation. Since the country's energy demand rises year by year, and will continue to rise in order to achieve the 2023 targets, solar energy investments will be indispensable. The investment in renewable energy sources in Turkey is increasing rapidly in recent years, since the country has poor reserves regarding fossil fuels. One of the main renewable energy sources for investment is solar PV energy. Turkey is an ideal country for solar energy harnessing due to their geographical position. The annual solar radiation of Turkey is 1400 kWh/m²-year (4kWh/m²-day) and the annual average total insolation duration is as 2640 hours (7,2 hours/day) based on the data measured by the State Meteorological Services. Figure 1 shows the solar radiation map of Turkey as of 2011. Table 1 shows the regional distribution of solar energy potential of Turkey. As it can be seen clearly, Turkey has an abundant solar energy potential especially in southern regions [4-6].
Figure 1. Solar Radiation Map of Turkey
Table 1. Regional Distribution of Solar Energy Potential of Turkey
There are some factors considering the solar investments. Mostly, the investors are selecting the southern regions of the Anatolia for the solar energy investments. Therefore, the investments for other regions of Turkey are considered insignificant and unprofitable. But this information does not reflect the truth. The main reason is that, as an example although Germany is far behind the Turkey regarding to the solar radiation, in terms of installed power it is the leading country in the world. The number of the sunny days in Germany is very low, but the solar electricity generation is much more than any other country in Europe. Therefore, the solar electricity generation does not depend very closely on the solar radiation of the related region. Especially, Antalya region is very popular for solar energy installation since it has very high solar radiation compared to the other regions of Turkey. On the other hand, Van region which is situated in East Anatolia has remarkably lower solar radiation than Antalya region, and also has an outstanding solar energy potential. The reason of this, Antalya region has higher temperature than Van region and solar cells are sensitive to temperature. As the solar panels get hotter, they will produce less power from the same amount of sunlight. In a solar cell, the parameter most affected by an increase in temperature is the open-circuit voltage. Figure 2 shows the effect of increasing temperature. It is known that around 4.5% efficiency reduction occurs for every 10 °C temperature increase [6-9].
Figure 2. The Effect of Temperature on the IV Characteristics of a Solar Cell
With the improving of the technology, it has been simple to calculate the efficiency, production values, and payback period using related simulation tools. For this purpose, in this paper PVSOL Expert 6.0 which is a dynamic simulation tool with 3D visualization of roof-integrated or mounted grid connected photovoltaic systems resulting in graphical form was used regarding the cost of a possible investment for a solar power plant [10-11]. With the help of this simulation tool, the comparative analyzes related to the solar radiation and the temperature effect on the PV electricity generation between the two cities were performed in this study. Using this tool, it is possible to calculate the stand-alone and grid connected PV systems optimization.
For the simulation of the system, 18 units Wingli polycyristall solar panels with 250 W output power has been used. As an inverter which is an electric device that converts Direct Current (DC) into Alternating Current (AC) [12-14], 5 kW Fronius Symo 5.0-3-M grid connected power inverter was selected. Cable length is 4 meter on the DC side. Table 2 and Table 3 show the technical parameters of the selected solar panels and inverters.
Table 2. Technical Parameters of the Solar Panels used in Simulation
Table 3. Technical Parameters of the Inverters used in Simulation
PVSOL Expert 6.0 is getting the required solar radiation values for their calculations from the database program called Meteonorm which contains worldwide weather data that can be used for manual analysis or for photovoltaic, solar thermal or building simulation software. The database of the Meteonorm is fed by 8325 weather stations worldwide as well as by five geostationary satellites with global coverage.
These parameters include the number of vertical panels, gaps between the panels in horizontal and vertical, spacing, height from the ground of the bottom panel, the panel angle and orientation angle respectively. Simulation parameters entered at the beginning of the program is shown in Figure 3. 3-D visual system built in the PVSOL Expert 6.0 simulation is shown in Figure 4.
Figure 3. Simulation Parameters
Figure 4. 3-D Visual System of the Simulation
Some losses in the installation of the simulation are ignored and the required cable sizes are selected. The assumptions are shown in Figure 5.
Figure 5. Acceptable Losses and Cable Lengths
As it can be seen in Figure 6 and Figure 7, the solar panel temperature difference between the two cities is about 13,4 °C. Since the high temperatures affect the solar panel efficiency in a negative way, the efficiency could reduce remarkably in Antalya compared to Van. The wind speed is a little bit more in Antalya than in Van, but this does not affect significantly on the production efficiency of the solar panels.
Figure 6. Temperature and Wind Speed Values for Antalya
Figure 7. Temperature and Wind Speed Values for Van
From Figure 8 and Figure 9, it can be easily said that in terms of solar radiation, Antalya is much more advantageous than Van, because of the geographical location.
Figure 8. Solar Radiation and Energy Production Values in Antalya
Figure 9. Solar Radiation and Energy Production Values in Van
Table 4 shows the annual solar energy capacity, efficiency of the whole system and subsystems, and electricity production values according to the existing solar power with reference to the PVSOL Expert 6.0. It seems that the efficiency of the possible solar power plant installation would be much more due to the temperature effect on the solar energy production in Van.
Table 4. Annual Solar Energy Capacity, Efficiency and Electricity Production Values for Two Cities
In Table 5, the financial analysis of the solar power plant for two cities was performed. The unit price for the 4,5 kW solar power plant has been taken as 1,5 €/kW. This is the estimated cost of the solar power plant installation in Turkey. The unit price of the electricity for the selling was taken as 133 cent/$ [2].
Table 5. Financial Analysis of the Solar Power Plant for Two Cities
The temperature effect has not been considered for the performed calculation, as the temperature of Van was taken as the same reference for both cities. For the calculation of the payback period due to the annual solar radiation were 1 taken as 1€=3,17 TL and 1$= 2,93 TL as of December 2015.
As can be seen in this paper, the electrical efficiency and the output power of the solar panels depend linearly on the operating temperature since the solar cell performance decreases with the increasing temperature like in Antalya case. Therefore, the payback period which is the time in which the initial cost of investment is expected to be recovered from the cash inflows obtained by the investment, takes much more time. While the payback period in Van takes about 8 years, this period in Antalya is about 723 years. But considering the temperature effects in Antalya this time extends to 756 years. The temperature effect on the payback period is about 3.44% according to the financial analyses. From the results obtained in this study, it can be said that Antalya is not attractive as it can be believed for the attention of investors in this sector. Regarding to the solar radiation for a solar power plant installation scenerio in Antalya, the efficiency is only 6.25% much more than Van. Related to the cost of an investment for a solar power plant investment both cities can be selected consequently.
In this paper, the authors have investigated and discussed the comparative analyzes of solar energy production potential between Van and Antalya using PVSOL Expert 6.0 simulation tool for better understanding in which part of the country should be invested regarding solar energy generation. Antalya has one of the most sunny days in Turkey. Therefore, it is considered as one of the main cities for solar energy investments in the country. However, when considering the negative effects of the temperature on the solar panel efficiency, the solar radiation is not so effective as thought. For further studies and researches besides temperature and solar radiation effects, humidity effect on the solar electricity generation should be examined and taken into consideration, since the humidity is another factor for the solar power efficiency and a payback period for the initial cost of investment.
This study was supported by Karabük University Scientific Research Projects Office.