Imagine a city where the buildings chat to each other and message the grid. A city where hydrogen-powered fuel-cell plants blend seamlessly into the urban landscape while supplying fresh water. Movement happens via multimodal smart transport systems powered by low-carbon fuels, allowing travelers to minimise their environmental impact and travel time. Imagine a zero-emission city!
This city is much closer than you think, but achieving it at scale requires a new vision of how cities operate, underpinned by technology and an integrated approach.
Cities occupy 2pc of the world’s landmass, accommodate more than 55pc of the global population and account for more than 70pc of global CO2 emissions. New research from the Norwegian University of Science and Technology shows that 20pc of those emissions come from just 100 cities. And with 90pc of the world’s urban areas situated on coastlines, these same cities are at higher risk from the impacts of climate change. Scientists at non-profit organisation Climate Central estimate that 275mn people worldwide live in areas that will eventually be flooded at 3°C of global warming, with cities including Osaka, Shanghai, Miami and Rio De Janeiro among the worst affected.
So what are the critical pillars and technologies in the transformation journey to more sustainable cities?
1. Firstly, the highest abatement potential comes from decarbonising, decentralising and digitising electricity grids. Generating more renewable electricity from distributed power sources that are closer to where the demand is enhances overall energy efficiency. Rooftop solar is widely available and building integrated photovoltaic (PV) is about to enter commercial viability. Large-scale renewable plants—solar or offshore wind—are also essential to cover the remaining demand. The digitalisation of the grid through technology, such as sensors and smart meters, will also enhance cities’ grid flexibility and overall resilience through automation and real-time information.
2. Next is tackling building carbon emissions, which means looking at both the energy efficiency and the choice of materials and construction methods (see Fig.1) . Poorly insulated existing housing stock remains a big challenge and needs to be addressed by lowering energy demand and through innovative heating/cooling systems. The electrification of heating and cooling through technologies such as heat pumps is one promising option, but various others exist—such as biomass or hydrogen cogeneration, industrial surplus heat and energy storage.
Historically, heating temperatures have decreased while system efficiency has increased through innovative energy systems. Supporting the market with minimum efficiency standards on newbuilds is essential, and the digitisation of the grid becomes even more important to balance a higher proportion of all-electric homes. For existing buildings, it is a bit more complicated and incentives will be required to overcome financial barriers and consumer inertia e.g. California regulators recently approved $45mn for heat pump water heater incentives through 2025.
3. Alongside buildings, the decarbonisation of private and public transport plays a key role in reducing emissions and improving urban quality of life. For private transport, current technological development trends indicate that electric vehicle (EV) battery costs will go down and range will go up eventually, but faster-charging infrastructure build is required to make EVs a major market segment in the immediate term. It is also important to shift the ratio of transport modes towards cycling and shared/public, which also requires widespread infrastructure implementation. Again, technology such as AI, data and end-to-end payment business models have a role to play here in supporting transport systems for easy door-to-door journey planning, experience and payment.
Public transport needs to be expanded and made cost-competitive to attract higher use. In an ideal world trains, buses and commercial transport are electrified with renewables. To maximise local power production, station roofs and railway tracks could be used for solar PV. Applications that are not possible or hard to electrify—such as long-haul road transport, aviation and shipping—transition from fossil-fuels to biofuels or hydrogen. The first hydrogen trains are already in operation in Germany and the UK.
4. With urban building and infrastructure construction worldwide expected to increase dramatically, the emissions caused by the extraction, manufacturing (of carbon-intensive materials such as steel and cement), processing and transportation of construction materials, known as ‘embodied carbon’, are another key facet of the sustainable city. The share of lifecycle emissions attributable to embodied carbon is also expected to increase further with reductions in operational emissions and the electrification of buildings. The construction sector will need to adopt innovative low-carbon technologies. There are three key developments in this area:
- H2 in industrial processes, carbon-sequestering cement, or the employment of carbon capture and usage to deliver ultra-low carbon cement and steel production
- Lowering the climate impact of buildings by reducing the need for concrete through better design and increasing the use of other options such as wood and alternative concrete
- With the sector also representing 33.5pc of the total waste generated by all economic activities, according to Eurostat, the design of more recyclable materials and closed material flows in the refurbishment and demolition phases (circularity of building materials) will also play an important role.
5. Finally, cities can use digital technologies—such as smart meters and mobility apps—to integrate and connect all these individual assets to improve overall efficiency and flexibility in urban areas.
Integrated planning
Integrated planning of industrial and urban energy demand can maximise overall system efficiency and lower the overall energy demand, and hence operational costs. There is a growing number of examples of this linkage between industrial operations, either with city needs—for example, using waste heat from industries for district heating/cooling—or with industries connecting to other industries by using a byproduct—such as oxygen from hydrogen production being used to improve wastewater treatment. Lighthouse examples are the Kalundborg symbiosis project in Denmark (interconnecting 12 different companies), the Hochst industrial park in Germany (which couples chemical production with transport), the Ori Martin steel project in Italy (waste heat to district heating and power), the Aurubis copper plant in Germany (providing excess heat to district heating), or a Swedish data centre project (providing waste heat to district heat).
This same innovative thinking must be applied when enhancing liveability in our cities through additional recreational areas and giving infrastructure various purposes. In the past, the purpose of a power plant was to provide power. That of a flood wall was flood protection. Now we are seeing dual purpose planning being applied more often. One great example from the power sector is the Copenhill plant in Denmark—a power plant combining waste disposal, electricity and heat supply and a recreational park. Similarly the Dryline project in New York combines flood protection and recreational areas.
Achieving this vision will require many things, but one factor to highlight is cooperation across various public and private stakeholders—local and national governments; infrastructure stakeholders; construction and real estate developers; mobility, equipment and technology providers; utilities; and financiers. Certainly, that is not an easy task, but remember to imagine a net-zero city for you and your family—it is a goal worth going out of one's comfort zone for.
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