A big picture of urban heat island mitigation strategies and recommendation for India

doi:10.1016/j.uclim.2021.100845

Urban Climate

Volume 37, May 2021, 100845

https://doi.org/10.1016/j.uclim.2021.100845 Get rights and content

Highlights

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Assesses various heat island mitigation strategies and their effectiveness.
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Proposes a set of recommendation based on research and analysis.
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Provide short term and long-term suggestions to mitigate the UHI effects.

Abstract

Climate change poses a great threat to humans and the ecosystem of the planet. There are many factors that trigger climate change, and there are many aftereffects. One of the after-effects is Urban Heat Island (UHI), recognized as the most evident characteristic of urban climate which occurs due to dark, non-reflective surfaces. These surfaces absorb the warmth of the Sun, radiate heat; Thus, increase the land surface temperature. Additionally, heat islands increase cooling loads in the summer, which tends to increase energy consumption and produce more greenhouse gases. There are numerous strategies to mitigate the UHI effect. This study reviews various UHI mitigation strategies and their effectiveness in cooling the urban environment and propose a set of recommendation based on research and analysis. Broadly, the mitigation strategies have been divided into (i) Roof strategies, (ii) non-roof strategies, and (iii) covered parking strategies. It has been found out that the simultaneous use of several UHI mitigation measures has a more significant impact on lowering the urban temperature and could be mitigated. The study highlights the importance of each mitigation strategy and presents a set of recommendations for India that can be directed at the government level to policies to mitigate the UHI effect.

Introduction

In the recent past, the earth's ecology has witnessed climate change. Scientists have researched that global temperature will continue to rise for decades due to greenhouse gases produced by human activities which include the use of air conditioning for thermal comfort. Global climate change due to various other reasons and one of the reasons is rapid urbanization in large cities is worsening the liveability status of the people living in the cities and their surroundings. Currently, more than 50% of the world population lives in urban areas, and it is expected to increase to 6.4 billion by 2050 (Bocquier, 2005).

It has been established that an increase in global temperature has a direct impact on the microclimate. There are many factors that trigger climate change, and consequences afterward. One of the after-effects is Urban Heat Island (UHI), recognized as the most evident characteristics of urban climate. It occurs due to dark, non-reflective surfaces used for parking, roads, roofs, walkways. As urban areas developed, open land and vegetation have been replaced by buildings, roads, landscapes and other infrastructure. These surfaces absorb the warmth of the Sun and radiate heat. The increase of land surface temperature influence material flow and energy flow in urban ecological systems, employing a series of environmental effects on urban climates and human health.

According to a study of the metropolitan area of Chicago and Salt Lake City by the LBNL, the energy-saving potential of heat island reduction measures ranges from $4 million to $15 million per year (Konopacki and Akbari, 2002).

The present paper assesses various heat island mitigation strategies and their effectiveness in cooling the urban environment. It also proposes a set of recommendations for India based on research and analysis. It includes an extensive overview with a focus on the measures-specific approach to UHI mitigation. The present paper provides policies or programs to identify and spread successful approaches as time and cost-efficiently as possible.

Section snippets

Impact of urban heat island

A community's environment and its quality of life can be affected by the increased temperatures from urban heat islands, especially during the summer. Though some heat island impacts appear positive like the expansion of the plant growing season, most impressions are negative and includes:

Benefits of urban heat island mitigation

Mitigating the urban heat island effect can produce benefits for buildings, cities, suburban areas, and globally as well. There can be a:

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Reduction in energy bills in Air-conditioned buildings and unconditioned buildings can be cooler in the summer months
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Reduced thermal expansion in roof and thus extended life
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Peak shaving of electric demand during the summer months because of reduced building cooling loads
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Adverse health and mortality impacts may reduce during extreme heat events.
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Improved air and

Strategies to mitigate UHI

There are numerous strategies to mitigate the UHI effect, leaving a positive impact on both local and global climate. The mitigation strategies have been sub-divided into three parts:

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Roof strategies (high-reflectance roof, vegetated roof),
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Non-roof strategies (shading structure with energy generation/architectural devices, high reflectance paving, plantation, and water bodies) and
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Covered parking strategies.

By using these strategies, UHI effects could be significantly reduced. It has been found

Roof strategies

Dark, non-reflective surfaces used for car parking, roads, roofs, walkway, and other hardscapes absorb the sun's warmth and radiate heat, thus creating heat islands. Urban areas can have temperatures 1 to 3 °C (Zielinski, 2014) hotter than nearby suburban and undeveloped areas. Following are the roof strategies that have been discussed to mitigate the effect of UHI.

Vegetation

The presence of vegetation in open spaces within urban areas has a relevant impact on the urban heat island phenomenon with a bulk of effects on the different terms of the surface energy balance. Vegetation in urban open areas can make many contributions to high-quality urban living. It can stop radiation, decelerate wind, and reduce air temperature and plays a key role in the urban thermal environment.

Trees efficiently decrease the thermal radiation in urban open spaces and contribute to the

Covered parking strategies

Parking lots can cover up to half of the land area in cities and offer a great opportunity to correct urban climate problems. The conversion from asphalt-covered parking areas to grass-covered parking areas is helpful to reduce the urban heat island effect. The parking area can be covered with at least one of the following methods: (a) have SRI coated roof; (b) a vegetated roof; (c) covered with energy generation systems such as thermal collectors, photovoltaics and wind turbines.

Recommendations

Urban design plays a major role in heat island formation, and smart growth development strategies provide an opportunity to reduce heat islands. Smart growth increases the community's economy and safeguards the environment through strategies that help citizens to make well-informed decisions regarding the built environment. In addition to limiting the heat island effect, smart growth provides a framework that increases regional environmental protection, enhancement in the community character,

Conclusion

Urban open spaces with a suitable thermal environment attract citizens and boost the vitality of cities. The thermal environment in outdoor spaces can be decomposed into air temperature, thermal radiation, wind speed, and humidity. The present paper reviewed a number of literature and the effectiveness of different mitigation strategies in modifying the urban thermal environment. The following conclusions can be drawn from the literature review:

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Urban geometry changes the radiative and

Declaration of Competing Interest

The authors declare that they have no objection and conflict of interest to publish this paper in your journal.

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A big picture of urban heat island mitigation strategies and recommendation for India

Highlights

Abstract

Introduction

Section snippets

Impact of urban heat island

Benefits of urban heat island mitigation

Strategies to mitigate UHI

Roof strategies

Vegetation

Covered parking strategies

Recommendations

Conclusion

Declaration of Competing Interest

Energy Build.

Energy Build.

Heliyon

Energy Build.

Energy Policy

Energy Build.

Build. Environ.

Sci. Total Environ.

J. Clean. Prod.

Urban For. Urban Green.

Renew. Sust. Energ. Rev.

Energy Build.

Renew. Sust. Energ. Rev.

Sol. Energy

Energy Build.

Sustain. Cities Soc.

Build. Environ.

Build. Environ.

Urban For. Urban Green.

Cool Roof Rating Council

Using Cool Roofs to Reduce Energy Use, Greenhouse Gas Emissions, and Urban Heat Island Effects: Findings from an India Experiment

Thermal comfort for all

Mitigating Urban Heat Island Through Green Roofs