|Fig. 1: Moscow Metro ornaments. (Source: Wikimedia Commons)|
The Moscow Metro was opened on May 15th 1935 with one 11-kilometre line and 13 stations. It was the first underground railway system in the Soviet Union. As of 2016, the Moscow Metro excluding the Moscow Central Circle has 203 stations and its route length is 339.1 km making it the fifth longest in the world. Today the metro system transports over 56% of the people who use public transport within the city. According to the official Moscow Metro website the system on average is used by 7 million people per day and this number exceeds 9 million people daily on weekdays. This is the highest number of people using a subway system in the world. The Moscow metro is known for its ornaments which as you can imagine requires a lot of energy (Fig. 1). In our modern society energy efficiency is becoming increasingly more important as the energy prices are very high and the Moscow Metro is no exception.
Moscow metro uses up extremely large amounts of energy every year. In 2007 the total length of the routes equaled to 305 km and the total energy consumption from outside resources was already 1.6 billion kWh per year. Specific energy consumption was 5.245 mln kWh per km of railway. The current plans are to expand the metro to 467 km of routes by 2020 which means that the total energy consumption will be 2.5 billion kWh (467 × 5.246=2,447). If we assume that the energy price is going to be around 3 rubles/kWh it means that the expenses of keeping the metro going are going to be around 8 billion rubles which with the current exchange rate would equal approximately $123 million. Therefore under the current predictions we can say that each wagon is going to be consuming 2.5 million kWh costing 7.5 mln rubles. This shows that the most pertinent issue is decreasing the specific energy consumption of each unit. The main way to do so is increasing the energy efficiency of the trains themselves as 75% of the energy goes towards pulling them, 20-22% for the maintenance of the rails and around 3-5% for repairing base.
The Moscow Metro is moving towards a more sustainable energy future. The Moscow underground system is not unique in its high energy consumption and just like any other city need to take advantage of clean technology To achieve its goals. There a number of ways to improve the efficiency. Ultracapacitors, train automation, and kinetic energy harvesting are just three technologies that can augment the Moscow Metro's energy paradigm. More initiatives to reduce energy consumption can be split into 4 main categories - Infrastructure (eg. Intellegent ventilation), rolling stock (eg. Aluminium bodies), stations (eg.PSD installations) and operational strategies (eg.vary speeds of the trains). 
The current energy expenditures of the Moscow metro are far too high to be sustainable. There are plenty of technologies around to improve the efficiency and the question is how much time and investment the government is willing to put in. The situation is however no different from any other major city and the problem exists everywhere.
© Evgeny Moshkovich. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 R. Andeson, R. Maxwell, and N. G. Harris, "Maximizing the Potential For Metros to Reduce Energy Consumption and Deliver Low-Carbon Transportation in Cities," Imperial College London, September 2009.