Introduction

Modern society is undergoing the rapid process of urbanisation. Currently, about 4.4 billion people live in cities, and over 80% of GDP is generated in urban areas. It is predicted that by 2050, 6.5 billion of the predicted 9.8 billion population will live in cities.
 
With this growth, however, will come the exacerbation of an already pressing issue: air pollution. It has been considered the greatest environmental health problem in some countries, such as the UK and it can be attributed to 7.4 million deaths annually. Furthermore, it also poses a threat to the environment, causing eutrophication, acid rain, damage to wildlife, crop failure and, most importantly, global warming. Globally, cities emit 80% of air pollutant emissions and around 99% of the world’s population may live in places where air pollution levels are dangerous, according to the WHO. These are disturbing statistics, illustrating the scale of the air pollution problem in urban areas. How can this situation be ameliorated, allowing for urban inhabitants to live healthily in a sustainable environment? Can smart technology help?
 
Smart cities are a framework, predominantly composed of advanced information and communication technologies, to design and deploy sustainable development practices to address growing urbanization challenges. This article will lay out cities’ contributions to air pollution, and then delineate the role of smart technologies (features of smart cities) in solving and mitigating them.
 

Air Pollution

Air pollution is composed of a few main components: greenhouse gases (GHG); some toxic gases such as nitrogen oxides (NO_x), sulphur dioxide (SO₂) and carbon monoxide (CO); and particulate matter (PM), which is separated into three main groups: coarse particles - PM10, fine particles - PM2.5, and ultrafine particles - PM0.1. The main source of GHG emissions is energy production, making up over 70% of the total. NO_x is released in the exhausts of cars, as is CO. Moreover, CO and SO₂ are produced in fossil fuel powerplants. The sources of PM are similar to the sources above: PM0.1 and PM2.5 are released in vehicle exhausts and domestic combustion activities (e.g., gas stoves and barbecues) and all three groups of PM are released in powerplant emissions. In all, three main sources of air pollution, relating to cities, can be identified: high energy consumption, congestion of vehicles, and domestic uses of fossil fuels.

 

High Energy Consumption

Cities consume a huge amount of energy. Globally, urban areas consume around 75% of primary energy. However, a large proportion of this energy is wasted due to poorly optimised, inefficient energy systems. Illustrated in Figure 1, energy is responsible for most of GHG emissions and energy generation from fossil fuels also emits many harmful air pollutants such as SO₂, CO and many particulates.
 

 

Traffic Congestion

Many harmful and toxic air pollutants, such as NO_x and CO are released in the exhausts of cars. This is exacerbated in highly congested areas where the essential journeys of city inhabitants are prolonged in frequent gridlocks and traffic jams in the middle of city. According to a study by Harvard School of Public Health, emissions from traffic congestion in 83 of the United States' major cities cause over 2,200 deaths annually.

 

Domestic Use of Fossil Fuels

The domestic combustion of fossil fuels and biomass (gas boilers, wood stoves etc.) are still highly pollu
 tant, emitting all three of GHG, toxic gases, and PM. Wood-burning stoves emit around 44kg of PM2.5 annually.

 

 

Solutions and Mitigations

 

High Energy Consumption

They ways in which smart cities solve this problem are twofold. Firstly, a smart energy system, such as a smart grid, can reduce energy consumption by 30% by increasing energy efficiency and minimising energy wastage. Lights which turn off when no one is in the room are an extremely rudimentary example of how this happens. A reduction in energy wastage corresponds to a decrease in energy consumption, which will result in less demand for energy generation, ultimately leading to less air pollutant emissions from energy.

 

Secondly, smart grids can greatly improve a cities capacity for grid-connected renewable energy, using technologies such as active and reactive power flow control, advanced fault management techniques and virtual power plant control technology, thus allowing more renewable energy to be used in place of non-renewables resulting in less powerplant emissions.

 

Not only will the increased energy efficiency result in less energy consumption, but the remaining demand for energy can also be filled by more renewables, doubly reducing pollutant emissions from energy generation.

 

Congestion

Urban Traffic Management Control (UTMC) systems maximise capacity and minimise congestion. UTMC systems vary traffic light timings to better fit the consumption of road capacity in real time. When all the traffic lights are co-ordinated to adjust their timings responsively to demand, incidences of gridlock are minimised. The traffic light system can be modified to deal with specific scenarios (e.g., an accident on an arterial road) and these modifications can be implemented as soon as such an incident is detected. Furthermore, the rising number of electric vehicles on the road will reduce air pollution significantly as they not only produce no emissions, but the electricity which supplies their power can benefit from the green efficiency of a smart grid system.

 

Domestic Use of Fossil Fuels

Electricity-based appliances, which are significantly more efficient and less polluting, lead to a decrease in total energy consumption and pollutant emissions from homes and energy generation. Figures 2 and 3 show the differences between electricity-based home appliances and traditional home appliances in terms of efficiency and emissions. This relates to smart cities because electric appliances can be integrated into smart energy systems, further increasing their energy efficiency and allowing them to run on more clean energy - in all reducing pollutant emissions considerably.

 

Mitigation through Smart Planning

Poor air quality can be improved in cities through smart planning - specifically, architecture designed around windflow. Windflow modelling uses a 3D model of a certain planned or existing urban area and simulates the flow of wind in that area. Urban architects can utilise this model to design buildings which ameliorate wind flow, e.g., by making their shapes more aerodynamic. This has happened in the Punggol Northshore district in Singapore, where, by adjusting specific buildings’ designs, architects were able to improve windflow, particularly in the town centre, resulting in better air quality. Dr. Cheong Koon, the head of the Housing and Development Board of Singapore, affirmed this, stating that “[improved wind flow] means you get a cooler and better air quality”.

 

Benefits and Challenges

The potential benefit of smart technologies on air quality is promising. There will be better air quality in cities, resulting in better public health, less strain on local hospitals and fewer deaths due to air pollution related ailments. Improved global air quality will help to solve global warming and result in a reduction in climate change related issues. Furthermore, these smart solutions will also have many desirable biproducts such as: less traffic - small reductions in traffic flow (say 10-15%) can result in very large reductions in congestion; and increased domestic energy efficiency means a lower monthly energy bill.

 

Smart cities will still face lots of challenges, such as the erosion of privacy by dataveillance (through surveillance, identification, secondary use, blackmail and many more), cybersecurity, the corporatisation of governance (where large corporations use the promise of smart cities to capture government functions as new market opportunities), insufficient infrastructure, and socioeconomic inequality, to name a few. These challenges must be addressed before the benefits of smart city can be fully unleashed.

 

Conclusion

Air pollution is an unfortunate biproduct of urbanisation. As cities evolve, they must turn to face this problem. While smart cities still have many issues, they are outweighed by its ability to ameliorate the effects of air pollution and ultimately global warming and climate change, a far more pressing and existential crisis – the former problems can be addressed with the continuous development of technology and the implementation of relevant legal policies. Although not a silver bullet solution to air pollution and the climate crisis, it will doubtlessly play a huge role in its reversal.