Analysis of Relationship between Climatic Variables and Electricity Consumption and Estimated Demand by General Circulation Models in Western Iran

Introduction
Electricity energy has no storage capacity on a large scale. Given the importance of this energy in various programs and increasing consumption in the context of global warming, it seems necessary to forecast its future consumption with in the energy sector policy. Therefore, awareness of the variables affecting electricity consumption and the impact of each of them will enable policy makers to make more precise planning and prediction of electricity consumption in the coming years. Therefore, accurate estimation of the consumption with regard to climatic conditions can play an important role in the economic use of electrical energy. The purpose of this research is to investigate the relationship between climatic variables with electricity consumption and prediction of electricity consumption under the influence of climate change in western Iran.
Materials and methods 
The study area of this research is western Iran including provinces of Kermanshah, Kurdistan, Hamedan, Ilam and Lorestan. This region has a variety of climate conditions due to its location on the path of hot and cold air masses and mid-latitude cyclones. The data used in this study are including 1) meteorological data of 13 stations in the region over a 28-year period (1987 to 2014), including minimum temperature, maximum temperature, relative humidity, wind speed, sunshine hours and rainfall, 2) data on monthly electricity consumption during the corresponding period, 3) data simulated by CCSM4 General Circulation Model. To calculate the heating and cooling requirements, values of Heating Degree Days (HDD) and Cooling Degree Days (CDD) were calculated using the minimum and maximum temperature data. First, the relationship between climatic variables and electricity consumption at stations was modeled using multiple regression equations. In the case of significant models based on the data of the CCSM4 model, the electricity consumption at the stations during the period 2080-2080 was estimated under two scenarios RCP4.5 and RCP8.5. Future climate scenarios were then downscaled using the "change factor" method. To verify the downscaled data, we used the Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Coefficient of Determination (R2).
Results and discussion
At all stations, the CDD have a direct and significant relationship with electricity consumption, due to the high consumption of air conditioning/cooling equipment in summer. But the relationship between the HDD and electricity consumption is weaker than the CDD; because in winter, less electricity is used to heat the environment. Especially in warm stations such as Ilam, Dehloran and Sarpole-Zahab, the relationship between the HDD and electricity consumption is not substantially significant. At these stations, during the cold season due to the mildness and shortness of the cold, there is little need for electrical equipment for heating purposes. In contrast, in these three stations, humidity has a significant and inverse relationship with electricity consumption. Other climatic parameters have no significant relationship with the consumption. The mean maximum and minimum temperatures in the region in the future period (2021-2080) will increase on average under the RCP4.5 scenario by 1.95ºC and 2.01ºC, respectively, and under the RCP8.5 scenario by 3.46ºC and 3.81ºC. Therefore, electricity consumption at all stations in the upcoming period (2021-2080) will increase more than the past period. This increase will be much higher in the warm period of the year. The average increase in consumption during the warm period at the stations under the two scenarios will be 80% and 150%, respectively. Particularly warm stations in the west of the region, such as Dehloran, Sarpole-Zahab and Ilam in the warm months (6 months, from May to October) will experience the highest increase in electricity consumption under two scenarios, about 110% and 210%, respectively. The lowest increase in demand for electricity in the upcoming period is related to the relatively cold stations of Hamedan, Sanandaj, Saqez and Bijar. Because of the mountainous nature, the high altitude and the longer cold period, the main need of these stations is heating, a significant part of which is supplied by natural gas. This clearly has little dependence on electricity. During the warm period of these stations, which is shorter and lasts for 4 months (June to September), the increase in consumption is lower than that in warm stations and under the two scenarios, it would be about 60% And 110%, respectively. Other stations like Khorramabad, Kermanshah, Kangavar, Boroujerd and Islamabad will have an intermediate level of consumption. However, it should be noted that regardless of the increase, electricity supply for larger and more populous cities such as Kermanshah and Hamedan will be more important than warm cities. There is not much increase in consumption in cold-period months at any warm and cold station.
Conclusion
Since a significant part of the electricity consumption in the region is due to the use of conditioning/cooling equipment, any change in temperature during the warm period will be effective on increasing or decreasing trends using  the equipment, and consequently, increasing power consumption. Given the significant increase in the temperature of the region during the 2021-2080 period under the two scenarios, it is necessary to take appropriate strategies to deal with the drastic increase in electricity consumption in the future, especially during the warm period of the year.