(124a) A Holistic Approach to Urban Design and Urban Heat Island Effect Mitigation Strategies to Improve Energy Efficiency in Urban Environments | AIChE

(124a) A Holistic Approach to Urban Design and Urban Heat Island Effect Mitigation Strategies to Improve Energy Efficiency in Urban Environments

Authors 

Watson, C. - Presenter, University of Alabama at Birmingham
Peters, R. W. - Presenter, University of Alabama at Birmingham


The relationship between anthropogenic activities and climate change has been investigated by several researchers in various fields of study. Research indicates at the global level, human beings daily activities consume large quantities of the earth's natural, finite resources (mainly fossil fuels), thus resulting in adverse environmental impacts from the extraction and production of these finite reserves. In 2008, the U.S. Energy Information Administration (EIA) announced that approximately 83.44% of the energy consumed was produced from fossil fuels (U.S. EIA, 2009). Global use of fossil fuels and coal for energy production and other industrial needs has led to an increase in the amount of heat-absorbing gases released into the atmosphere. Several factors contribute to the increased consumption of such resources, including declining household size, population aging and urbanization, but the problem primarily stems from population growth (PBR, 2009). According to the Census Bureau, the majority of the world's population will be living in urban areas, predominantly in under developed countries. In 2007, approximately 50% of the world's population was living in an urban area. In 2015, approximately 53% of the world's population will be living in an urban area, and by the year 2030, approximately 60% of the world's population is predicted to be living in an urban area. This increase in population has the potential to have significant impacts on resource use and energy consumption. As energy is a high priority on many of our leaders' agendas at the present time, we have to concentrate our energy reducing efforts on areas where people are expected to be in future years. Population growth patterns vary across the globe, but have significant impacts on how we produce and consume these resources to meet energy demands. As population trends change in regions and countries over the next fifty years, it is imperative for the developed countries to educate and train the underdeveloped countries on lessons learned from previous production and consumption methods. According to the Population Reference Bureau (PBR), 90% of population growth was recorded in underdeveloped countries during the 20th century (PRB, 2009). Population growth in these countries is mainly due to the widespread availability of health care and disease prevention, thus prolonging life expectancy in human beings in these regions. It is estimated that between 2009 and 2050, nearly all population growth will take place in underdeveloped countries and population growth recorded for more developed countries will take place primarily in the United States and Canada, most likely attributed to immigration from Under developed countries (PRB, 2009). The Under developed countries are expected to see population increases from 5.6 billion in 2009 to 8.1 billion in 2050. On the other hand, more developed countries are expected to see an increase from 1.2 billion to 1.3 billion during that time (PRB, 2009). Managing urban population growth in under developed countries is one the world's most important challenges over the next several decades, for two reason, under developed countries do not have access to the same innovative technologies that their developed counterparts have, thus creating a mediocre attempt for accommodating this unprecedented growth, and secondly, 80% of the world's population resides in underdeveloped urban areas (Brockerhoff, 2000). Developed countries should recognize that it is their responsibility to share the ?best practices? of urban management with under developed countries, to inform them on sustainable methods for accommodating this expected growth with intelligent decisions that support the idea of ?sustainable? design. The United Nations (UN) anticipates that the world population will increase from 6.1 billion people to 7.8 billion people between the years of 2000 and 2025-with 90% of this growth projected to occur in urban areas of under developed countries (Brockerhoff, 2000). The PRB and information cited by Brockerhoff from the UN appear to be presenting two different opinions about population growth, but the PRB organizations defines more developed countries as countries who have been slowly advancing over time, and Brockerhoff considers countries that are not the United States and Canada to be underdeveloped, therefore the information presented is saying virtually the same information. Population growth presents several challenges for land planners, with the main challenge of how do we make room for the additional people and do we have enough resources to supply food and energy requirements to support this growth? Energy consumption from 1980 to 2006 increased approximately 66.8% and an increase in world energy consumption from 2010 to 2030 is projected to increase by approximately 33.5% (EIA, 2009). According to the U.S. Department of Energy (U.S. DOE) in 2005 energy consumption per capita in the U.S was 339 million Btu (DOE, 2008), and Canada with consumption of 439.5 million Btu per capita, compared to the world energy consumption per capita of 71.7 million Btu in 2005 (EIA, 2006). The U.S. consumes 372.8% and Canada 513.0% more energy per capita than the global average. According to Brockerhoff, under developed countries will be using the U.S. and Canada as models for managing and accommodating anticipated population growth, it is clear that there is a need to investigate how countries can improve efficient energy use methods. Modern trends in architecture and design have turned the efficient model of urban living into an inefficient one. Material selection and use of buildings and paved surfaces, replacing vegetation and trees with hard, impermeable surfaces, and building tall buildings and narrow streets, has resulted in cities experiencing increased ambient air temperatures than their surrounding rural or suburban neighbors and increased runoff during rainfall events. This theory is referred to as the Urban Heat Island (UHI) effect. The U.S. Environmental Protection Agency (EPA) defines the UHI ?as built up areas that are hotter than nearby rural areas.? Research conducted by the EPA indicates that cities with 1 million people or more people can have increased temperatures 1.8-5.4°F (1-3°C) warmer than surrounding areas. During evening hours, this difference can be as high as 22°F (12°C) (EPA, 2009b). Some of the adverse affects that UHI has on cities are increased peak energy demands during summer months, increased air conditioning costs, increase air pollution and greenhouse gas emissions, heat-related illness and mortality, and impacts on water quality. How cities are designed and planned can support or counteract energy efficiency. Urban design involves the integration of architectural design, landscape architecture and city planning to create a functional and attractive urban area, at the block neighborhood, and regional scales. Simply put, it is the arrangement and coordination of buildings, public spaces, transport systems, services and amenities. The process of urban design gives form, shape and character to groups of buildings, to whole neighborhoods, and most importantly, the city. Successful cities are able to achieve the goals of sustainability by one word, connection. Connections between people and places, movement and urban form, nature and built fabric, and nature and man-made, are the necessary connections for a successful, sustainable city (Urban Design, 2009). Each urban city is made up of five elements, which are as follows: buildings, public space, streets, transport, and landscape. It is within these elements where efforts can be concentrated to reduce the overall energy consumption in urban environments. According to the EPA, the four most common UHI mitigation methods are increased tree and vegetation square footage, green roof implementation, cool roofs and cool pavements (EPA, 2009a). These mitigation strategies are basically applied in two locations within the city, on street level or at higher elevations (rooftop level). These mitigation techniques have the potential to decrease differences of ambient air temperature at street level and at higher elevations. One area these methods over look is the in-between, between street and atmospheric levels. As with any technology, it is clear that this will only take us so far. Building facades account for the majority of the hard, heat-absorbing surfaces in urban environments, but there are not well-known technologies that can be implemented to take advantage of this valuable space to aide in achieving the goals of reducing heat absorbing and energy consumption. This research project focuses on the impacts of urban design on energy use, and how we can improve these designs with innovative technologies and design strategies to reduce energy consumption, for entire cities. Fifty-percent of annual building energy costs are for occupant thermal comfort. In addition to absorbing heat during the day, these surfaces can also transfer heat into the building and affect occupant comfort, which results in the consumption of more energy to compensate for increased temperatures. The overall objective of this project is to evaluate cities for energy performance and provide suggestions and recommendations to city planners and designer to improve energy consumption patterns. This project will focus on cities as a whole and not one an individual building approach. It is anticipated that the results from this project will provide a foundation to create a simulation software program that can evaluate energy performance on a city-scale.

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