This month, summer arrived in Taiwan. Together with the urban heat island effect, its arrival has resulted in temperatures rising to 37oC or 38oC over the past week. For the public this means simply dealing with the scorching heat, but Taiwan Power Co (Taipower) has to worry about the national power supply as power consumption peaks at about noon, when air conditioners everywhere start up. Having been involved in urban heat environment research for several years, I would like to introduce a few different methods for reducing temperatures in urban environments.
First, greenery. Planting greenery is a very important part of reducing urban temperatures thanks to the evaporation and evapotranspiration properties of green plants. This makes planting greenery the primary choice for reducing the urban heat island effect. Not only does it help to adjust urban microclimates, it also cleans the air, aids water and soil preservation, prevents fires, provides habitats and looks good. By creating more urban green corridors by, for example, coordinating plans with the construction of subway systems, cities could achieve several advantages in one fell swoop.
Second, increasing urban water bodies. As water evaporates, it absorbs heat from the surrounding environment and helps lower the temperature. Maintaining or creating suitable bodies of water in the city environment, such as ponds or rivers, or preserving water that seeps into and is stored in the soil, are all ways of how we can take advantage of evaporation from urban water bodies to lower temperatures.
Third, urban wind corridors and using air circulation to remove the heat from an urban area. Urban topography, geographical location or clusters of buildings will create long-term predominant winds, but since air circulation is rarely taken into consideration during initial urban planning, such wind corridors are not included among the main considerations in urban planning. In the vast majority of cities, wind speeds are lower in city centers than in the suburban areas because of the urban fabric and building obstacles. This means that wind fields in cities, with their chaotic air circulation corridors, cannot effectively disperse polluted air and excess heat. The result is that air pollution, high temperatures and the heat island effect problems continue to intensify. If water or green corridors or main roads are properly used to direct the wind, they would effectively help lower urban temperatures.
Fourth, “green” architecture. To reduce high urban temperatures and the heat island effect, cities should make a greater effort to promote “green” architecture. The appropriate control of shade and open windows to prevent buildings from absorbing and storing excessive heat will also help lower urban temperatures. In practice, using highly reflective surface materials on building facades, using as much greenery as possible on buildings — on rooftops and facades — and choosing the best fronting direction for a building and incorporating natural air circulation during the design stage will have a clear effect on lowering urban temperatures.
Fifth, a “green” lifestyle that focuses on energy efficiency in our daily lives. Artificial methods for dispelling heat are one of the main factors behind the urban heat island effect and high urban temperatures, and most of these methods have a direct relationship to our daily energy usage. Part of the energy generated by the electricity, gas and gasoline used by residents on a daily basis will be released into the urban environment as unproductive heat. Add to this the air conditioners that work hard in the summer heat and are a main culprit behind the urban heat effect and high urban temperatures. The question of how to create a “green” lifestyle therefore becomes an important policy as we try to change the global environment and lower high urban temperatures.