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Power plant instead of squanderer

Zero-energy buildings or even plus-energy buildings are today technically no longer a problem. Now comes the next level: the city as a power plant. In an interview with Steffen Klatt architect and city planner Steffen Lehmann illustrates why this requires the equal participation of policy makers, energy suppliers, universities and citizens.

Tomorrow's city needs to produce by itself at least half of its energy requirements
– Interview with Steffen Lehmann

Zero-energy buildings or even plus-energy buildings are today technically no longer a problem. Now comes the next level: the city as a power plant. This requires the equal participation of policy makers, energy suppliers, universities and citizens, says architect and city planner Steffen Lehmann.

Interview: Steffen Klatt

The world is urbanising. Are today's cities at all prepared for the future?

Steffen Lehmann: Humanity's future is in the city. Integrated urban development with a focus on energy and climate will assume a key role in collaboration with policy in order to radically reduce energy and resource consumption. It is important to expand the concept of 'city'. This means giving cities new tasks and areas of action that will significantly contribute to the so-called 'low carbon city' – a city with low carbon dioxide emissions. The resulting challenges are a part of what I call the post-industrialised condition. Today we find dwindling, non-dynamic cities together with insufficient investments and outdated infrastructure next to cities with fast-growing districts. We require comprehensive strategies to deal with such future demographic and structural changes.

You studied and worked as an architect in Germany, and now you teach in Australia. Are the challenges the same throughout the world?

The need for action for cities exists worldwide. The context may differ in Australia and the Asia-Pacific, Oceania, America and Europe, but the question of what a climate-conscious and energy-smart city should look like arises everywhere. In Asia, rapid growth and urbanisation processes and their related migration flows are front and centre. In the USA and Australia there are strategies to combat and reverse unsustainable urban sprawl and the enormous dependence on vehicles. In Germany and other European countries the emphasis is on adapting existing buildings in an energy-efficient manner and optimising material and energy flows. Cities are already built: the rate of new construction is only around one per cent.

How does the transition to a 'post-industrial city' take place?

Green urbanism is a holistic concept for the city of tomorrow, which is based on a consistent, resource-conserving treatment of energy, land, water, materials and mobility. The long-term goal of this is zero-emissions and zero-waste, which is a city without greenhouse gases and waste. This is achieved through the intermediate stage of the 'low carbon city'. This always involves promoting socially and ecologically sustainable neighbourhoods and districts. Similar principles have already been successfully implemented in the Vauban neighbourhood in Freiburg im Breisgau and in Hammarby-Sjöstad in Stockholm.

And yet cities will still need energy…

It is clear that cities will continue to be the places where most of the energy and a large portion of raw materials will be consumed and where most of the waste will be produced. But the greatest advantage of cities is that they provide us at the same time with the opportunity to make renewable energy sources profitable.


Energy demand in cities is enormous. It is therefore essential to quickly transform our energy and transport systems, so that they can be supplied from local, renewable energy sources to the greatest extent possible – not less than 50 per cent. The energy mix needs to take into account both the costs and the availability of technologies. On-site electricity production and energy storage can be transmitted and distributed through an intelligent power supply grid or 'smart grid'. In the zero-emissions city, neighbourhoods are transformed from energy consumers into energy producers. They become local power plants and make use of solar photovoltaic, solar thermal and solar cooling, wind power, biomass, geothermal energy, energy from small hydropower plants and other new technologies. This will mean changing the traditional role of the large energy suppliers from monopolist to service provider.

Even if this solves the energy problem, don't modern cities nonetheless require massive amounts of other resources?

Another important aspect here is the concept of zero-waste, which means putting an end to wasting materials and includes 100 per cent recovery of resources. Rubbish will be regarded as a valuable resource that should not be incinerated or buried in landfills, but rather completely recycled. Material consumption needs to be separated from economic growth. Zero-waste must be taken into consideration already from the beginning, while developing products and processes.

Are clean technologies enough to accomplish this?

This also requires sustainable consumption. And the need to also change our value system as well as our consumer behaviour. Unsustainable consumption in Asian cities and especially in the People's Republic of China is one of the greatest unresolved threats and one which must be urgently tackled in order to avert a supply catastrophe. But this should not be argued on moral grounds – no one wants to see their quality of life reduced. From today's perspective, China's future development is still unclear to a large extent.

Who needs to press for this change to the modern city?

It is crucial for citizens to be able to participate in the city's transformation. Without political support and leadership, change will not take place. The players in integrated urban development require the full support of administrators and policy makers in order to be able to implement their ideas, concepts and basic approaches. Policy is needed for quick action and to create the framework conditions to implement this in a suitable manner.

Should enlightened politicians keep their citizens happy?

They have to encourage participation. An important goal is to make cities once more an attractive living space for diverse and vibrant population groups, as a place for social integration. For some time now, we have seen in Australia and the USA a growing emphasis on community values and 'place-making' - creating public spaces with character. Residents are transformed from consumers into to active, engaged citizens.

What role does science play?

Science can focus on the bigger questions of urban change and the needs of the community without the interests of private investors in the foreground. Remodelling the city in an energy-efficient manner and its related new tasks call for competences to be developed on technical and political levels. Technical know-how spreads and develops competences. This intense experience matters just like the research developed in universities. In newly established research centres for sustainable urban development and with the help of best practice examples, tools and indicators should be developed to evaluate the ecological performance of cities and opportunities to improve the performance capabilities should be investigated. Universities can take on an important role as 'think factories' in the energy-efficient transformation of cities.

Steffen Lehmann, PhD (Dr.-Ing.), is a Professor at the University of South Australia in Adelaide and holds the UNESCO Chair in Sustainable Urban Development for Asia and the Pacific. He is director of the Research Centre for Sustainable Design and Behaviour (sd+b). Since 2006, he has been Editor-in-Chief of the Journal of Green Building. In the 1990s he collaborated on projects in Berlin such as the design of Potsdamer Platz and the Hackescher Markt, as well as the French Embassy, among others.
Steffen Lehmann is speaking on urban systems without waste at the Liechtenstein Congress on Sustainable Development and Responsible Investing.