Surely, among all the digital technologies in smart cities, we can find some ways to help alleviate urban heat…
In the last few months, if you live in an Asian city, you’d probably experienced higher temperatures than before.
In densely built-up cities, ambient temperatures can go up to 7oC higher than in rural areas in the same location. As economies develop, this heating effect will only get worse, unless mitigating action is taken.
To control urban heat – which can trigger other environmental issues such as air pollution and more intense storms, which can sometimes lead to flooding – urban planning and city infrastructure must be improved, and new infrastructure optimized to reduce heat retention.
Considering how massive – and expensive – city infrastructures are, how can digital technology help? DigiconAsia gained some key insights from Mahel Abaab-Fournial, Head of Business Strategy, Dassault Systèmes.
What are the key impacts of urban heating on city planning and smart cities?
Mahel Abaab-Fournial (MAF): Cities are experiencing a boom. Worldwide, more than half (about 56%) of the global population calls a city their home, and this trend is only set to increase, to about 70% by 2050, according to forecasts by the World Bank.
With more people comes the need for more buildings, more transportation and more air conditioning. This means more heat will be created.
Cities are usually warmer than the rural areas that surround them. This phenomenon, which is known as the “urban heat island” (UHI) effect, occurs because cities consume huge amounts of energy in electricity and fuel; are built from materials that absorb and radiate, or reflect, energy from the sun; and have less vegetation to provide shade and cooling.
The UHI effect over cities can average about 4°C, but it can exceed 7°C at certain times of the day. This warming creates a real public health issue for vulnerable people, and generates social inequalities among the population. It also reduces thermal comfort, discouraging people from walking or cycling, and increasing the energy used for air conditioning and driving.
As economies grow, cities’ UHI effect will continue to increase if nothing is done.
City planners should take steps to minimize the UHI effect when designing cities. Mitigating this effect also cuts cooling needs, which aids environmental sustainability. The key areas urban planners should look into include urban geometry, vegetation, water bodies and features, materials and surfaces, shading and transport.
City design factors that can be manipulated include building height, features and orientation; materials and surfaces; road direction and width; transportation arrangements, and vegetation and water body placement. How do these factors interact with one another, and what are the correlations between them and heat build-up?
MAF: Several factors influence the intensity of the UHI effect:
- Urban geometry, which includes factors like building height, features and orientation, have significant impact on the UHI effect. The arrangement of urban elements affects the spatial coverage of the shadowed areas as well as the wind environment. It is important to develop suitable air paths that enter the urban area and remove the accumulated urban heat. Though virtual twin simulation, wind flow characteristics can be accurately predicted without the actual structures being built. For example, using this technology, Stuttgart has converted a number of streets into ventilation corridors by creating wide, tree-flanked arterial roads that help air flow down from the hills to cool the city.
- Vegetation is widely used as a form of UHI mitigation. Thanks to their high solar reflection and low heat admittance characteristics, plants keep their surroundings like sidewalks, parking lots, and streets cool. The ambient air temperature reduction and building shading by vegetation also lower indoor air conditioning requirements. Removing waterproofed coatings on streets to revegetate them is a strategy cities can consider.
- Beyond vegetation, shading is a key measure to mitigate UHI, especially around noon when the sun angles are at the highest. Creating artificial shade works two-fold: it encourages residents to leave their homes (thereby reducing air conditioning use), and it makes community spaces heat-safe.
- Water bodies and features can also act as countermeasures to improve overheated building environments. Evaporation cools down the surroundings. Rivers or bodies of water serve as thermal regulators, they can be moved up from the underground to benefit from their cooling impact.
- Urban surfaces and materialsaffect the UHI effect through their heat absorption/reflection characteristics. Singapore, for instance, has been encouraging green walls on buildings. New York, on the other hand, has encouraged roofs to be painted white to increase buildings’ reflectivity.
- Transportation: Internal combustion engine vehicles typically operate at low efficiencies of 16-20 percent only, with almost all of the rest of the energy from the burnt fuel transformed into heat and dissipated. Besides switching to electric vehicles, reducing congestion ̶ which cuts down on running engines in the cities ̶ will reduce UHI. Setting up car-lite and car-free zones, building bicycle lanes and increasing public transport options will also help.
The interaction of the multiple factors above is complex, and can only be meaningfully linked and studied through 3D modelling and simulation technologies like virtual twinning.
How are changing demographics transforming city infrastructure?
MAF: Demographic changes are one of the main drivers transforming cities, affecting transportation demand, housing requirements, and public service needs. The birth of new children, arrival of new immigrants, or the aging of the existing population, all call for urban planners to make adjustments to the current cityscape to ensure inclusivity and enhance safety.
Specific measures include air quality improvement, greater pedestrianization, improvement of walkability comfort, and removal of barriers to ease the movement of wheelchairs and strollers.
Beyond changes in the size of specific segments of the population in cities, the overall size of the city dwelling population is increasing, as mentioned in our response to Q1.
This calls for actions like better mobility mix and infrastructure; more efficient energy solutions in buildings; sustainable power grids that incorporate renewables and grid-scale battery storage; and comprehensive connectivity that can usher in next-generation digital services.
With many cities already overcrowded and polluted, a perennial focus for urban planners will be to improve sustainability while offering citizens a better quality of life.
City infrastructures are costly and massive projects that once built are difficult to change. How does design, simulation and digital twin technologies help?
MAF: Before the advent of simulation technologies, structures were designed and built based on imperfect knowledge of their surrounding conditions. This leads to certain margins of errors. If these errors are significant enough, substantial amounts of manpower, time and cost would have been wasted, and rectification measures may be needed.
Virtual twin technology also enables data to be accessed and aggregated from a wide range of sources in a “single source of truth”. This data can be shared with multiple stakeholders (architects, designers, urban planners, health specialists, businesses, local authorities, etc.), allowing for unified analysis by all parties in real time, reconciling different interests and enabling true collaboration.
This leads to fewer inaccuracies and costly mistakes, better planning, better responses, and more effective implementation. By simulating issues as diverse as climate, health, safety and security, cities can plan and adjust their responses to meet and even exceed citizen expectations.
Advanced virtual twinning technology supports the whole life cycle of the building construction ̶ from the design phase to construction to operation and maintenance ̶ to reduce the total cost of ownership.
In addition, public authorities can now simulate future public decisions in the virtual twin prior to implementing them in real life. That’s “testing in the virtual world to improve the real world”.
For instance, it is now possible to compare various mobility scenarios (add a car sharing lane, reduce speed, allocate a lane to EVs, etc.) and analyze their impact on noise and air pollution with precise KPIs. The heat island impact of future infrastructures can also be simulated in virtual twins to quantify them.
Virtual twinning technology is also a way to engage with citizens to present new urban projects in a common 3D language to facilitate buy-in to policy decisions, and improve government-citizen communications and relations.
Virtual twin technology is now accessible by any city whatever its size and resources. For cities having skills and resources available, they can develop their own twin and analytics in-house. For cities with limited resources, they can benefit from this high-end technology as a service. Such a service model, operated by experts, gives cities faster access to their city twin, and provides them with the analysis they need. It is a shortcut to value.
