Cities are often described in terms that evoke the idea of energy. People talk about tem as ‘engines of growth’, as the ‘motors’ of modern life. While cites have certainly been the site for many developments in human society that have benefitted the population, whether the energy of the city that has been a central part in transforming many modern societies into urban rather than a rural one, and from a manufacturing –based to a service-based model, has helped people as much as is often claimed (typically by the richest and most powerful) is open for discussion. Where the energy of cities becomes more tangible is in the amount that they use.
Metropolitan areas use a lot of energy – from the resources and mechanical power required t construct them to the energy needed to provide the inhabitants with light, heat and water. The sheer density of the population of a city – in terms of both living space and also the attendant aspects that come with it, such as increased numbers of vehicles on the roads – makes them the most energy-demanding of all forms of habitation. Some city authorities are slowly realizing that the drain on unsustainable resources that cities represent is not feasible – and arguably morel I terms of our responsibilities to future generations – and have taken steps to reduce the reliance on non-renewable forms of energy, or at least to ameliorate the effects of such energy use. Such steps have ranged from instituting charges to drive a car into certain parts of a city in an attempt to limit car emissions to investing in public transport, as well as making buildings “greener” by, for instance, installing solar panels and rainwater harvesting systems, and using vegetation to moderate building temperatures.
However, there is a lot of useful energy that is generated by various aspects of city life that is more often than not going to waste, when it could, often with the implementation of a simply mechanism, be captured and put to use – allowing the city to meet some of its energy requirements via self-sufficient, sustainable means. Here are some of the innovative ways of capturing energy in cities.
Piezoelectric technology generates electricity when special materials are put under pressure. A nightclub in Rotterdam hit the headlines when it revealed that it had installed piezoelectric materials under its dance floor, so that the pressure from the patrons’ feet as they danced powered the lights of the club. The owners claimed that 60 percent of their energy needs were met by the technology. This method potentially has a lot of applications, particularly in cities where large numbers of people could traverse a specific area. Indeed, piezoelectric technology was installed at one of the main transport hubs for the 2012 Olympic Games in London, to harness the energy of spectators arriving at the site. And it is not just footfall that can be utilized; using the technology underneath cars can also generate a significant amount of energy. On a small scale, a piezoelectric panel at the entrance to a garage could provide the energy needed to light the garage, while on a larger scale, such energy capture on a major thoroughfare or bridge, say, could add a lot of electricity to the city’s grid.
Kinetic energy recovery
It is not just when vehicles are moving that they generate energy that can potentially be captured – they kinetic-71763_640do so when kinetic-71763_640they are braking too. In Formula 1 cars they already take advantage of this form of energy reuse (known as kinetic energy recovery systems) by harnessing the energy created when braking from high speeds. In Philadelphia, the technology has been appropriated for the subway system, capturing the energy released when the trains brake as they come into stations, and diverting it to a battery for reuse elsewhere in the metro system. (Speaking of trains, technology is currently being tested in Japan to harness the power of the wind generated by subway trains moving through tunnels to drive turbines and create power.)
Heat capture
The density of human beings in cities also gives rise to a tremendous amount of heat, simply from the heat we naturally give off as we convert food into energy within our bodies. Innovative techniques seek to use this radiated heat rather than let it simply dissipate. The central train station in Stockholm, Sweden, for instance, introduced heat exchange devices that channeled the heat created by the vast numbers of passengers transiting the atrium every day to an office building next door. The rail authorities now claim that this technique provides around 25 percent of the office’s energy needs. This reduces the use of energy from non-renewable sources both in terms of heating the office building and cooling the train station.
Exercise energy
City inhabitants also generate energy when they are exercising, and capturing this energy and converting it to power is a very tangible way of contributing to the generation of renewable energy. At present, prices for equipment such as energy-capture treadmills and stationary bicycles is very high, but with some consumer pressure and political will (by offering tax rebates or similar to gyms who install such equipment) hopefully the price will come down and they will be more common. They simply work by converting the exercise machinery into a turbine, using the movement of the treadmill or wheel to drive a dynamo. The resulting power can be used to provide some of the energy needs of a gymnasium, could feed into a household’s power grid, or be diverted into the municipal system.
While many of these energy-capture techniques can seem strange or even like quirky experiments, such innovative methods of supplying cities with the energy they need may well, as a matter of necessity become much more widespread. Given that almost all estimates point to cities continuing to grow exponentially in the future, with increasing numbers of inhabitants and therefore energy demands, the ability to come up with new and efficient ways of generating power without using non-renewable resources – which are, in contrast, diminishing – is likely to be among the most in-demand skills in future societies. So get your thinking caps on!

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