5.1. Status quo
It has been mentioned earlier that Turkey is in the GMT+2 hour time zone in winter months and the clock is shifted an hour forward from April to October when the daylight saving time is in effect. Time changes are made on the same dates as in other European Union countries. In Istanbul, average sunrise time in January is 7:21. Taking 7:00 as waking time, there will be 21 minutes of darkness in the mornings on average. In other words, an average of 21 minutes of electricity will be consumed for lighting every morning in January. Similarly, 12 minutes of electricity consumption will be needed in October and 17 minutes in December. As DST starts in November and the sun rises at 6:47 on average, there is no darkness in the mornings. Relative error with respect to existing daylight is 4.99%.
On the other hand, in Erzurum, the sun rises at 6:25 and 6:29 on average in December and January, respectively, when daylight is at its minimum. Taking 7:00 as waking time, there is 30 minutes of less daylight use on shortest days. In other months, there is even less use of daylight. Particularly in February, when winter time is practiced, daylight is used for 56 minutes less, in March for 1 hour and 40 minutes less, and in November for 1 hour and 4 minutes less. Relative error with respect to existing daylight is 10.25%.
The status quo causes less use of daylight. Even though there is daylight in the morning, life officially starts in Turkey 1 hour after other countries on the same longitude and ends 1 hour later in the evening, thus leading to increased electricity consumption.
Various scenarios are considered in this study to find the best alternative. Shifting the time forward is the practice chosen in some of the scenarios while keeping the current time changes on various different dates is the practice in others.
5.2. Scenario 1 – continuous DST observance
In this option, it is assumed that winter time is abandoned and clocks are not moved backwards between November-March. In other words, the current DST is used all year long and the clocks are not shifted at all. This means Turkey stays in the GMT+3 time zone throughout the year.
As the Sun rises at 8:17 and 8:21 on average in Istanbul in December and January, respectively, and waking time is 7:00, there will be approximately 1 hour and 20 minutes of darkness and thus increased electricity consumption in the morning during these two months. In the evening hours, though, lighting expenses will be compensated for 1 hour. However, adverse effects of an extended 1 hour and 20 minutes of morning darkness should not be ignored. For example, the increased risk of traffic accidents should be taken into account. During the new DST application in 1974–1975 in the USA, morning traffic accidents increased and concerned parents claimed that it puts schoolchildren in danger [15]. Coren [33] indicated that small changes in the amount of sleep that people get can have major consequences in their everyday activities. The loss of merely one hour of sleep can increase the risk of traffic accidents. In February and November, on the other hand, morning darkness will create a need for electrical lighting for 50 minutes on average. Different from the status quo, there will be only 10 minutes of darkness on average in the morning in March, thus making this option useful for this month. From April to October, the status quo will be practiced. Relative error will be 7.39% which is larger than that of the status quo.
As the Sun rises in Erzurum at 7:25 and 7:29 on average in December and January, 25 and 29 minutes of darkness will occur in the mornings, respectively. Despite a consumption of 25 and 29 minutes of morning electricity, the sun will set 1 hour later in the evening, thus compensating for this loss and saving approximately 30 minutes of electrical lighting. As the Sun rises approximately at 7:00 in February and November, no problems will occur and 1 more hour of daylight will be used in these two months. One more hour of daylight will also be available during March. Overall, relative error for Erzurum is 7.94%.