A modern metropolis must provide its own power

Circular systems will help cities become more self-sufficient in energy and tackle the challenges of carbon, cost and security, as Mike Scott reports

Cities produce some 80 per cent of the world’s greenhouse gas emissions so their future energy supplies will have to be much more sustainable than they are today.

This will happen through a combination of changes to infrastructure, more energy-efficient buildings and changes in behaviour of city residents.

Neil Kalita, of the Europe energy team at engineering consultancy Aecom, says: “Key energy challenges for cities in future will be carbon, cost and security of supply. Energy prices are only going one way and that’s up. And we saw the impact of being without power in New York during super storm Sandy last year, which cost the city billions of dollars.”

The pattern of energy use in cities will have to change, Mr Kalita believes, from a “linear metabolism” to a “circular metabolism” involving closed-loop systems. Currently energy flows into the city from remote power stations, but in future cities will produce much more of their own from renewable sources, such as energy from municipal waste and sewage.

Thames Water, for example, has just announced a £250-million investment in a technology called thermal hydrolysis process (THP), which will allow it to improve efficiency of the anaerobic digestion process that it already uses to meet 14 per cent of its annual energy needs – pumping and treating water is an energy-intensive business – and which last year saved £15 million in energy costs.

Lawrence Gosden, Thames Water director of capital delivery, says: “This investment is good for the environment, our business and our customers. As well as being environmentally friendly, generating energy from waste reduces running costs by protecting us from the price fluctuations of the mainstream, non-renewable energy markets.”

The most important thing is to control the energy we are already using and reduce that first

Many changes that will cut energy consumption in cities will come from buildings, which produce 40 per cent of all emissions and are under increasing pressure from policymakers to become more efficient.

Policy measures include introduction of Energy Performance Certificates and efficiency targets under the EU Energy Performance of Buildings Directive. In Tokyo, 1,300 of the largest commercial buildings are subject to a cap and trade programme, while in the United States cities including New York, Austin, San Francisco and Philadelphia, now require disclosure of energy consumption data in commercial buildings of a certain size.

“We’re going to see smarter buildings, more responsive to the demands of their occupants,” explains John Alker, director of policy and communications at the UK Green Building Council. “That means much better, real-time information about energy use through super-smart meters, but also buildings used differently to optimise energy use.”

Such information will be a vital part of creating more sustainable cities, says Mr Kalita, citing the work of companies, such as IBM and Google, in creating the concept of a smart city. “Part of closing the feedback loop is to provide more data,” he says.

This information will inform decisions about energy consumption and production at every level, from operation of national and city-wide smart grids to building management systems and smart meters.

“Energy efficiency is one of the biggest challenges for cities,” says Mikele Brack, an adviser to the World Cities Network and the C40 Climate Leadership Group. “No matter how you look at energy generation and supply, the most important thing is to control the energy we are already using and reduce that first.”

Examples of this include Burj Khalifa, the world’s tallest building, which uses solar water heating to heat 140,000 litres of water every day, saving 3.2 megawatts (MW) of energy, while One World Trade Center, one of the buildings that will replace the twin towers in New York, will have its own fuel-cell combined heat and power (CHP) plant producing up to 1.2MW of electricity, and using waste heat to provide hot water and space heating.

New technologies will in future help to turn buildings into mini-power stations; a group of UK universities is developing functional solar photovoltaic coatings on steel and glass to incorporate into existing and new buildings, enabling walls and roofs to generate, store and release energy.

This means the building can rely on a continuous sustainable energy source even when there is no sunshine. Sir David King, former government chief scientist and recently appointed to lead the Technology Strategy Board’s Future Cities Catapult initiative, says: “My hope is that in future we will all be painting the outside of our houses with paint that has plastic PV particles in so the whole house can help to generate energy.”

Future energy savings will also come from the Internet of Things, which will see transport, energy and buildings linked by a global network of sensors. Sir Richard Branson’s Carbon War Room suggests that this phenomenon could cut carbon emissions by more than nine billion tonnes by 2020.

However, all of these changes will have limited effect if building occupiers do not change their behaviour.

Esme Low, co-founder of the Climate Change Property Fund, which buys inefficient office buildings and improves their energy performance, says that one of the most effective ways to make buildings more sustainable is to tell people what you are doing.

“When we buy a property, we install an LED display in the building’s reception, linked to the automated meter reading system for energy, waste and water,” she says. “It helps measure performance and makes users aware there is a plan around energy efficiency and resource preservation that helps them buy into the whole idea and change how they behave.”

It is not just at the individual building level that there will have to be changes; developments such as Liverpool ONE are setting out to create sustainable neighbourhoods. As well as ensuring all buildings incorporated energy-saving measures, developer Grosvenor also focused on sustainable travel, creating a new bus station, cycle and walking routes, and a biodiesel plant that uses cooking oil from onsite restaurants to fuel development vehicles.

Such holistic thinking will be needed to ensure that cities live up to their potential without exhausting our energy resources.