At the world level, the 20th century saw an increase from 220 million urbanites in 1900 to 2.84 billion in year 2000. The present century will match this absolute increase in about four decades. Developing regions, as a whole, will account for 93% of this growth [1]. Until now humankind has lived and worked primarily in rural areas. But the world is about to leave its rural past behind. Today we are witness, for the first time, that more than half of the globe’s population is living in towns and cities. The number and proportion of urban dwellers will continue to rise quickly. Urban population will grow to 4.9 billion by 2030. At the global level, all of future population growth will be in towns and cities [1]. Two centuries ago there was only one city on the planet that could say it had a million inhabitants - that was London. Today more than 400 cities can boast that - 408 to be precise, according to the Earth Policy Institute. But today a population of 1 million people means nothing; we are moving into the era of megacities of 10 million (and more) people. Today, there are 20 so-called megacities, whose population, and therefore energy needs, easily exceed some countries population, according to Earth Policy Institute. More people now live in Tokyo than Canada, for example [2]. Despite only occupying 2% of the world's surface area, they are responsible for 75% of the world's energy consumption.