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The human body as an alternative energy source: human electricity

Global demand for energy is increasing all the time, but sources of natural energy are dwindling. One obvious solution is to use the human body as an alternative energy source, and the idea is attracting growing interest from researchers, not only in Germany but across the world. In Germany’s industrial heartland around the Ruhr, for example, electricity can now be generated from human waste water. Meanwhile, passengers using Stockholm’s Central Station are heating a neighbouring building and people living in Toulouse will soon be powering street lighting just by walking along.

Virtually every country in the world has waste water treatment plants, yet the idea of using them as an alternative energy source to generate electricity is very recent. Waste water contains bio-waste, which is rich in energy. Treatment plants in the north-western German city of Bottrop alone treat waste water produced by around 1.5 million people. In the past, much of this waste was simply disposed of after treatment; now, it’s used to supply energy. In 50-metre high towers, bacteria break down human bio-waste into sewage gas, which is 70 % energy-rich methane. The residual sludge is converted into bio-gas by the action of microbes.

Director of the Bottrop treatment plant Eberhard Holtmeier says‚ ‘We produce around 900 cubic metres of sewage gas an hour here, which we use to run our two combined heat and power plants – or, if you prefer, enough to supply the annual electricity needs of around 7,000 households.’

Free alternative energy source

A typical individual generates some 100 kilowatt hours of thermal and kinetic energy a year. Our daily calorie intake from food is re-released throughout the day – at any one time, we’re expending the energy equivalent of a 100 watt bulb – and this alternative energy source can be harnessed. Stations are a good example. Stockholm Central Station is the largest in Sweden, and some 400,000 people pass through it each day. Most of the physical energy they use is converted into heat and, paradoxically, this means that the station has to be artificially cooled, even in winter. Meanwhile, the underground air conditioning plant is also generating heat.

Klas Johansson, who heads the environmental affairs department at Jernhusen AB, which operates the station, says, ‘What we are trying to do is to get individual buildings to communicate with each other. We can use the excess heat from the station in one of our office blocks across the street.’ Integrated heat exchangers use the excess to heat water. That in turn heats a neighbouring office block and supplies its hot water. ‘Free excess human heat in the station is reducing energy costs by a quarter’, notes Johannsson.

The ‘electric pavement’ as an alternative energy source

The French city of Toulouse has some 70,000 streetlights - and hefty electricity bills. The city has been working with Toulouse’s Technical University on ways of cutting lighting costs without compromising safety. The aim of the Trott-Èlec  project – the name derives from the French for ‘electric pavement’ – is to harness footsteps as an alternative energy source that can, for example, be used to power lighting in pedestrian areas. One of Trott-Èlec’s biggest headaches is ‘harvesting’ the kinetic energy we produce as we walk. The solution is a micro-generator embedded in the pavement that converts the kinetic energy produced by each step directly into electricity. Eventually, each paving slab will have five micro-generators feeding into an accumulator battery, though work is still ongoing to determine how they should be arranged for maximum energy efficiency.

Alexandre Marciel, Toulouse’s Deputy Mayor, says, ‘Society has traditionally taken the view that cities consume energy. We believe that a city can also generate energy. The Trott-Èlec project means that individuals can see a direct link between what they produce and what they consume – right here on the street.’

Using the human body as an energy source won’t be enough to solve the world’s energy problems, and we need to develop a wide range of alternative energy concepts as well as save energy. However, projects focusing on developing alternative energy sources can make a substantial contribution, using underexploited resources and raising awareness of global energy issues.

Author: Andreas Förster

June 2012

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