Cooling Singapore 2.0: Researchers build nation's 'digital twin' to assess urban heat and find ways to cool city

SINGAPORE — Could power plants on Jurong Island influence temperatures on the mainland? To what extent will electric vehicles and tree cover reduce urban heat in a neighbourhood like Tengah?

These are some questions urban planners may have as they aim to cool down cramped, urban areas that can be up to 7 deg C hotter than less built-up areas — due to the urban heat island effect.

Instead of doing time-consuming experiments or projects to get their answers, the authorities can soon test them through the virtual world, much like playing a video game.

Over the last four years, more than 20 researchers have built a "digital twin" of Singapore that allows users to simulate scenarios to figure out how to make living spaces more thermally comfortable for people.

This virtual system, known as the Digital Urban Climate Twin, is one of the flagship projects under the multi-institute Cooling Singapore 2.0 research initiative, which is developing solutions to address the urban heat problem in Singapore.

The project is led by the Singapore-​ETH Centre, in partnership with other institutions including the Singapore Management University, National University of Singapore and the Singapore-​MIT Alliance for Research and Technology.

At the core of the virtual system - which has an interactive map of Singapore to create various scenarios — are heaps of computational models and data sets, including some that the researchers had to build from scratch.

The data sets include islandwide vegetation cover, traffic patterns, heat emitted from industries, and weather-related data such as wind flow. The digital twin also taps information from complex climate models that run in the National Supercomputing Centre Singapore, said Ander Zozaya, project manager of Cooling Singapore 2.0 at the Singapore-ETH Centre.

On May 30, the team behind the digital twin presented its prototype version of the system to other researchers, corporations and some government agencies at the Campus for Research Excellence and Technological Enterprise located in the National University of Singapore.

It is now looking to get these external parties to test the system, carry out simulations and provide feedback on how to enhance the digital tool into an operational one.

Dr Kristina Orehounig, who leads Cooling Singapore 2.0, also presented the digital twin at the World Cities Summit at the Suntec Singapore Convention and Exhibition Centre on June 2.

To show the digital twin's capabilities, the team on May 30 conducted a demonstration to predict how temperatures islandwide will change if three forested areas were to be converted to industrial parks or residential complexes in 2030.

Buildings and air-conditioning are key contributors of urban heat, while urban parks — depending on their size and tree cover — may provide cooling.

After replacing patches of vegetation with buildings on the virtual map, the climate modeller illustrated how the Republic would look like in 2030, based on some targets under the Singapore Green Plan.

For example, more electric vehicles on the road would translate into less exhaust heat coming from peak-hour traffic.

And a future energy mix comprising some low-carbon electricity imports and more renewables could translate into a slight drop in electricity produced and heat released by local power plants.

The modeller then ran the 2030 scenario in the digital twin and simulated heatwave conditions to predict how the three built-up areas would fare under gruelling heat.

The results were as expected — temperatures rose in the newly built-up areas, especially at night, when the urban heat island effect is stronger.

There are also features in the virtual tool to help developers experiment with and find out how to optimise district cooling systems in their building projects.

District cooling technology involves generating chilled water in a centralised location and sending the chilled water through a network to multiple buildings, where it is used for air-conditioning. By sharing the load of cooling, buildings lower carbon emissions and save costs.

One crucial data set the digital twin team had to build from scratch — a daunting task, said Zozaya — was the amount of heat released by the power and industrial sectors of Jurong Island. The researchers wanted to find out if heat coming from the energy and chemicals hub influences temperatures islandwide.

The industrial and power sectors also happen to be the top two greenhouse gas emitters in Singapore.

What made the data-gathering challenging was that most companies and agencies do not report on their heat emissions, said Zozaya. The team had to get creative, which meant scouring satellite data and individual company reports. It also had to painstakingly crunch numbers and estimate Jurong Island's heat emissions by using the firms'data on energy usage and carbon emission.

Eventually, the researchers built a data set based on 119 companies on Jurong Island, and their 568 heat and carbon dioxide emission points.

Through simulations, the digital twin showed that heat from Jurong Island has a minor effect on the rest of the country as the effects are more localised and pronounced in the Tuas region.

As a prototype, the Digital Urban Climate Twin has not reached its fullest potential yet, noted Dr Orehounig.

"We can only learn to improve it and solve good problems if people test it; they break into it, basically," she added.

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