Sustainable Urban Energy: Key Ideas from Peter Newman and William Rees

Urban energy is the set of sources, networks and uses that power a city: the electricity of buildings and street lighting, the heating and cooling of homes and offices, the fuel of transport and the energy embodied in water, food and materials. Cities consume close to two thirds of the world's energy and generate around 70 percent of the associated emissions, so the energy transition is largely decided in them. Two authors have defined the framework for thinking about it: Peter Newman, co-author of Resilient Cities (2009), and William Rees, creator with Mathis Wackernagel of the concept of the ecological footprint.

William Rees and the ecological footprint of cities

Rees, a professor at the University of British Columbia, formulated the ecological footprint in the 1990s: the area of productive land and water a population needs to produce what it consumes and absorb what it discards. Applied to cities, the figure is revealing: London needs a territory more than a hundred times its own surface, and rich cities depend on distant ecosystems they neither see nor govern. Rees argues that the modern city is a thermodynamically open system that imports concentrated energy and exports disorder, and that no city is sustainable if its footprint exceeds the capacity of the biosphere.

Peter Newman: resilient cities without fossil fuels

Newman, a professor at Curtin University in Perth, wrote with Timothy Beatley and Heather Boyer Resilient Cities: Responding to Peak Oil and Climate Change (2009), revised in 2017 as Resilient Cities: Overcoming Fossil Fuel Dependence. His argument is that dependence on oil and coal is the greatest urban vulnerability, and that the resilient city is the one that produces its energy from renewables, distributes it through decentralised smart grids and reduces demand with efficient buildings and transport that does not rely on the car. Newman describes seven city models, from the renewable city to the car-free city, and shows that fragments of each already exist.

Generation, grids and demand: the three levers of urban energy

Urban energy policy works at three levels. In generation, with rooftop solar, energy communities that share production and heat networks fed by biomass, geothermal or waste heat, such as Copenhagen's, which covers almost the whole city. In distribution, with smart grids that manage the intermittency of renewables, battery storage and electric vehicle charging that stabilises the grid. In demand, with energy retrofits of buildings, which account for 40 percent of consumption in Europe, nearly zero-energy building codes and a compact urban form that shortens trips.

Energy poverty and a just transition

Energy resilience also has a social dimension. Energy poverty, households unable to heat or cool their homes, affects tens of millions of Europeans and grows with heatwaves. A just transition requires that retrofits reach the most vulnerable neighbourhoods first, that energy communities include those without a roof of their own and that tariffs protect lower-income households. Newman and Rees agree that cutting the footprint and emissions without asking who pays the bill reproduces the inequality the fossil city already produced.

Cities such as Copenhagen, which aims for climate neutrality, Freiburg with its solar districts, Adelaide with a grid fed by renewables or Medellín with its electrified transport show that the transition is possible at urban scale. The joint lesson of Rees and Newman is that energy is not one more service but the city's metabolism: deciding where it comes from, how it is distributed and how much is consumed is deciding what footprint the city leaves on the planet and how well it withstands the crises to come.