Cities are leading the way in the circular economy transition. But what does it take to become a truly circular city? This series of articles explore the key services that cities need to adapt in order to become fully circular. These include energy, construction and physical resources, water, food and mobility. This article delves in the challenging world of building renewable and resilient energy systems.

The Importance of Energy Systems in Cities

So what exactly is an energy system and why is it important to circular cities? An energy system essentially encompasses the entire energy supply chain from energy generation to use. Energy systems ensure that the streets are lit at night, that our water is clean and wastewater is treated, that our factories can produce goods and our metros can run. Yet to become circular, city energy systems face significant challenges, such as increasing demand whereby more than 70% of the worlds population are expected to live in cities by 2050. The intermittent nature of renewable sources, a lack of energy storage solutions and re-designing energy-efficient transport systems are also key challenges. Perhaps the biggest headache of all is that these issues are highly interconnected with one another and so they are better addressed as a whole rather than separately.

circular energy systemsTherefore to become circular, cities must support and align innovation at the key intervention points within the cities energy system. These intervention points include energy (i) generation; (ii) storage; (iii) infrastructure; (iv) facilities and (v) transport. Thankfully, there are countless examples of innovations that target such intervention points and making circular energy systems viable.

Energy Generation

Taking inspiration from how nature uses decentralized energy generation, a New York-based initiative is leveraging the blockchain to allow individuals (with rooftops) to buy and sell energy to each other, therefore reducing reliance on a centralized grid. Elsewhere in the United States, city governments are also tackling the energy generation issue. Last year Las Vegas became the first city government to be powered by clean energy through a combination of building a giant solar farm and utilizing existing hydro power capacity. In Germany, Munich is going one step further by aiming to ensure 100% renewable energy supply to the city by 2025 by forcing utilities to only source energy from renewable sources. Local utilities’ companies are now investing in renewable energy producers from all over Europe to meet this demand, therefore promoting a pan-European transition to renewable electricity.

Although European cities are beginning to wake up to the need to transition to low carbon and resilient energy supply systems – the phrase ‘whilst Europe thinks, Asia does’ still holds an element of truth behind it. Take, for example, the Energy-Safe Cities – East Asia Program. The aim of which is to help a mindboggling 12 mega-cities, 100 super-cities and urban regions, 450 large cities as well as 450 small and medium-sized cities from China, Korea, Taiwan, Mongolia and Japan to become powered by 100% renewable energy in less than 15 years.

Energy Storage

The intermittent nature of renewable energy supply means that cities are required to significantly increase their capacity to store energy generated from renewable sources to help maintain a steady flow of energy into the grid. Yet energy storage technologies have yet to be proven economical at scale.

However, when founder of Space X, SolarCIty, Tesla and OpenAI Elon Musk invests in the energy storage industry, it’s a clear sign that times are changing. Both Tesla and Southern California Edison were recently contracted by the Californian Government to supply 20MW of storage capacity to help the City transition from a fossil fuel-based grid to a predominantly renewable energy-powered grid. Perhaps even closer to a circular energy solution – a team at UC San Diego is now trialing a full scale energy storage system that uses old electric vehicle batteries to help integrate solar power into the campus.

circular energy systems

Energy Storage System Trial Using Old EV Batteries Source: UC San Diego

Energy Infrastructure

Once renewable energy has been generated and stored, it needs to be transmitted efficiently across the electricity grid to the end user. The concept of the ‘smart grid’ offers a number of benefits to efficient energy distribution through a myriad of innovations that leverage cutting edge communication technologies to allow real time communication between energy generators, utilities and users (i.e. households, electric vehicles and factories). In short – this leads to a much more efficient energy system.

The city of Chattanooga in Tennessee, U.S.A. may not conjure up the image of an energy pioneer– but that is exactly what it is. Chattanooga has spent USD$115 million on rolling out smart meters to every single house in the city and have installed over 1000 Intelliruptors. Intellirupters leverage the power of the Internet of Things (IoT) to automatically detect faults in the grid, reroute energy and heal the grid. They are effectively creating an internet for energy.

circular energy systems

Installing Smart Switches for Intelliruptors in Chattanooga Source:

Energy Facilities

Once the energy has been transferred through the smart grid, it needs to be used intelligently and efficiently by energy facilities, which includes everything from commercial and residential buildings to small-scale infrastructure.

What can be done to make our energy facilities more circular? Well – quite a lot in fact. Buildings may be designed in such a way that they barely require any energy, therefore significantly reducing demand on the grid. Take Växjö, in Sweden, for example, which has built two high-rise buildings based on the passive house design which requires very little energy compared to similar sized traditional buildings. But we can also build smart buildings, which also leverage IoT technologies. Smart buildings have been estimated to reduce energy demand by up to 22%.


Transport is one of the biggest consumers of energy – not to mention polluters – in cities, but thankfully, this is the area most ripe for disruptive innovation. The growth of electric vehicles in the next decade – which is predicted to be exponential – will have several consequences on the structure and performance of smart grids. Electric vehicles will be able to supply and draw energy from the grid, thus providing a significant buffer to the intermittency of supply predicted from renewable sources. Car manufacturer Nissan’s project in the UK is currently trialling vehicle-to-grid systems where electric vehicles become part of the energy grid.

Another solution is to encourage city dwellers to adopt more carbon neutral modes of transport through building more cycling infrastructure so that bikes begin to outnumber cars (such as in Copenhagen), or redesigning our entire city landscapes to be more walkable.

circular energy systems

Vehicle-to-grid systems trialled in the UK Source: Cornwall Nissan

What is clear is that there are countless solutions targeting specific intervention points in the energy systems. The question remains, however, how to integrate them all together to build a truly circular energy system for cities.