Energy Optimization in Metro Line by Using Regenerative Energy

The share of rail transportation in urban transportation systems in metropolitan cities is increasing due to its punctual, comfortable and environmentally friendly nature. As a result of increasing energy costs worldwide, the importance of energy efficiency is increasing. A more efficient passenger transportation can be achieved by increasing the rate of regenerative energy use in rail transportation systems. In this study, energy optimization method was performed for whole train fleet. So that total energy consumption of trains was reduced. The traction power for the first train was set to minimum by adjusting speed profile and by considering metro line’s constraints and 100 % of the regenerative energy released during braking was used in the second train. Compared to one subway trip where regenerative energy was not used at all, 43% energy saving was achieved when regenerative energy was fully utilized. Istanbul subways make approximately 250 trips a day. In other words, savings of 195 kWh x Energy Unit Price per trip will be achieved. By applying this method to a subway line, will provide a great energy saving daily, monthly and yearly. Less energy consumption will also lead to less carbon (CO2) emissions. This method was simulated for the Istanbul M5 Üsküdar – Çekmeköy - Samandıra subway line and the results were compared with the actual data.