Cooling Energy Solutions for Buildings and Cities

Mat Santamouris

• Publisher: WSPC
• ISBN:
  9789813236981
• Topic: Architektur
• Subtopic: Nachhaltigkeit in der Architektur

In the first book of its kind, this volume addresses the problem of the future cooling energy demand, the global frame defining the actual and future cooling energy consumption in the building sector. Based on the explored inputs and forecasts, a model

Chapter 1

Cooling of Buildings: The New Energy Challenge

M. Santamouris

1.1.The Need for Cooling

Solar gain through the non-fully-shaded transparent parts of the building envelope, heat gain through the opaque and transparent parts of the building skin due to the major temperature difference between the outdoor and indoor environments, infiltration and ventilation losses and gains, as well as the major internal generation of heat may be the main sources of overheating in buildings. Indoor temperatures may exceed comfort levels, creating major discomfort and serious health problems to the vulnerable population while possibly reducing the productivity and the well-being of the inhabitants.

The increase in the ambient temperature caused by local and global climate change, along with the potentially poor design of buildings and lack of resources to use mechanical cooling systems, has forced a major portion of the world population, exceeding a billion of people worldwide, to live under very uncomfortable indoor temperatures.

Several experimental studies have shown that, during the occurrence of a heat wave, the indoor temperature in low-income households may exceed 32–35°C, causing serious discomfort and health problems (Figure 1.1).

Figure 1.1.Evolution of indoor temperature levels in low-income households in Athens during a heat wave.

Source: Sakka et al. (2012).

It is well known that high indoor temperatures lead to an increase in the mortality and morbidity rates in the global population, mainly in the vulnerable and low-income groups. As shown by Baccini et al. (2008), the threshold temperature beyond which heat-related mortality increases significantly varies from place to place as a function of the local adaptation processes (Figure 1.2). Heating-dominated areas present a much higher threshold temperature than the cooling-dominated zones, where people are not adapted to high ambient temperatures.

To decrease the indoor temperature in buildings, passive and hybrid cooling techniques may be used. Passive cooling techniques are based on the use of solar and heat control systems, amortization of the heat surplus using additional thermal mass in the buildings, and the dissipation of the excess heat into a low-temperature natural sink like the air, ground, and water (Santamouris and Kolokotsa, 2013; Santamouris et al., 2007). Passive cooling techniques and systems have proven to be very efficient and, based on the numerous large- and real-scale applications, may cover a very significant part, if not the whole cooling load of buildings (Santamouris, 2006).

Figure 1.2.Relation between apparent temperature and heat-related mortality in several European cities. The red band corresponds to the threshold ambient temperatures in cooling-dominated cities while the yellow one corresponds to heating-dominated cities.

Source: Baccini et al. (2008).

Extensive research has been carried out in the recent years to optimize the performance and the global efficiency of passive cooling technologies and systems. Apart from the important energy contribution of passive cooling techniques, they provide very good indoor comfort and maintain excellent indoor air quality (Lloyd, 1992). Many new materials, systems, and techniques have been developed and are now commercially available. The newly developed systems and technologies have been extensively tested in several demonstration and real-scale building projects. In most of the cases, and when the design was properly done, the employed techniques contributed significantly to reduce the cooling energy consumption and improve the indoor environmental quality. Monitoring data show that passive cooling techniques can cover, in a very satisfactory way and with a very low cost, almost 70% of the cooling load and demand of buildings.

However, passive cooling techniques face some serious climatic limitations, as their cooling potential has been seriously decreased because of the increase of the ambient temperature caused by local and global climate change. Thus, it not always possible to satisfy the complete cooling requirements. Under these conditions, the use of mechanical cooling is necessary to provide the rest of the load and guarantee proper indoor comfort conditions even under extreme climatic conditions.

1.2.The Air Conditioning Industry: Past, Present, and Future

Mechanically driven air conditioning systems were developed and commercialized in the U.S. in the second decade of the previous century. However, until 1955, air conditioning was considered a luxury item, and only 2% of the residential buildings in the country were equipped with a mechanical cooling system. The widespread penetration of the mechanical cooling systems began in 1950, mainly because of the significant economic growth, the relatively low-energy prices, and the increasing affordability of the air conditioning systems. As mentioned by Biddle (2008), in the 1980s, almost half of the American homes were equipped with air conditioners.

Currently, the air conditioning industry is a giant business sector, presenting a total annual turnover of around US$100 billion (BSRIA, 2015), with very serious prospects for further expansion. Air conditioning saturation is very high in some countries like the U.S. and Japan and is quite close to the maximum possible penetration levels. However, the world average penetration of the mechanical cooling systems is quite low, although the actual penetration rates are faster than income growth. Most of the sales are mainly in the cooling-dominated zones of the planet and in the developing and the newly developed countries. According to McNeil and Letschert (2008), the annual sales of air conditioners in India grow at a rate close to 20% per year, while according to the same authors and Zhou et al. (2012), in China, the penetration of air conditioning in urban residences has increased from 1% in 1990 to about 63% in 2003 and almost 100% in 2010. It is evident that the future evolution of the air conditioning industry will be highly affected by future climatic conditions, especially the ambient temperature increase induced by global and local climate change, the increase in the world population, and the possible rise in family income. Other parameters, such as future energy prices, technological efficiency, and affordability of air conditioning will also have a major influence on the cooling market.

Increase in the ambient temperature caused by climate change reduces the cooling potential of passive cooling techniques significantly and increases the necessity for air conditioning (Santamouris et al., 2010). According to Santamouris et al. (2015), when the ambient temperature increases by 1°C, the corresponding rise in the peak electricity demand may vary between 0.45% and 4.6%. This is equivalent to an additional electricity penalty of about 21 (±10.4) W per degree of temperature increase and per person (Figure 1.3). In India, the necessary additional electricity consumption to satisfy the cooling demand in the year 2030 is estimated at close to 239 TWh/y, which is equivalent to an additional power installation of 143 GW (Phadke et al., 2014), or 300 new coalfired electricity power plants of 500 MW each. According to Downing et al. (1995, 1996) a potential increase in the average ambient temperature by 1 K may result in an additional energy consumption for cooling purposes costing around US$75 billion.

Studies aiming to estimate the additional electricity to be spent in Europe for cooling purposes, just to compensate for the impact of climate change by 2015, showed that it will range between 22 and 89 billion Euros per year (Mima et al., 2011). In parallel, it is estimated that the required cost of investments to purchase the additional air conditioning equipment will be close to 8 billion and 20 billion Euros by 2050 and 2100, respectively. The impact of global warming is accentuated by the tremendous increase in the population expected in the future. In fact, as foreseen by the United Nations, almost 52% and 34% of the world population will live in Asia and Africa, respectively, in 2050. To understand the combined impact of climatic change and overpopulation on the energy demand for cooling purposes, it is mentioned that the foreseen potential cooling energy consumption of the city of Mumbai, India, will be equal to 24% of the total actual cooling demand in the U.S. (Sivak, 2009).

Figure 1.3.Increase in the peak electricity demand (%) per degree of ambient temperature rise.

Source: Santamouris (2015).

Given the extreme values of the forecasts concerning the future cooling energy consumption, the role of energy efficiency becomes very crucial. The energy performance of the buildings as well as the efficiency of the air conditioners will impact future demand. Significant improvements in the energy efficiency of air conditioners has been achieved during the recent years; however, whether it is enough to counterbalance the impact of climate change and overpopulation is yet to be determined (Shah et al., 2013). It is evident that the development and use of more efficient air conditioners will greatly contribute to a decrease in the expected energy consumption and the need for additional power plants. According to Phadke et al. (2014), the use of highly efficient air conditioners in India could reduce the cooling consumption by 118 TWh by 2030, decrease the peak electricity demand by 60 GW, and avoid the installation of about 120 new power plants of 500 MW each.

The role of efficient and strict energy performance regulations for the building sector is very significant. According to different studies (Kapsalaki et al., 2012; Papanikolas et al., 2015), the implementation of efficient legislation along with the use of high-performance energy equipment and management may result in a very substantial decrease in the cooling demand of buildings.

1.3.The Actual Global Penetration of Air Conditioning

As already mentioned, the average penetration of the air conditioning systems in the world is quite low, despite the impressive saturation levels in the U.S. and Japan. In Europe, the penetration of air conditioning in the residential sector is close to 8% but is increasing rapidly (Santamouris, 2016). In urban China, there are almost 1.07 air conditioners per household, and while in the rural areas, it is close to 0.12. However, the use of air conditioners in rural China is showing a rapidly increasing trend.

The total value of the world air conditioning market in 2014 exceeded US$997 billion and presented a relative increase close to 7%, compared to the previous year (BSRIA, 2015). According to statistics, almost 128.5 million air conditioners have been sold worldwide. About 58% of the sales are in the Asia-Pacific region, where China and Japan present about 83% of the specific market. A rapidly burgeoning air conditioning market is also observed in the rest of the countries in the region, such as Malaysia and Vietnam.

In Europe, despite the dynamic increase in the sales in U.K.’s commercial sector, which comprises 22% of the market share in the region, the total number of sales in 2014 significantly decreased mainly because of the serious economic crisis in the European South and Russia. The drop was close to 5%, while the total market figure was around US$11.2 billion.

A major increase in air conditioning penetration has been observed in South America, mainly because of the significant climate problems caused by El Nino. In Brazil, the annual increase rate reached 29%. In parallel, the air conditioning market in the U.S. in 2014 presented a considerable increase, ...

Table of contents

• Cover
• Halftitle
• Title
• Copyright
• List of Contributors
• Contents
• Chapter 1. Cooling of Buildings: The New Energy Challenge
• Chapter 2. The Impact of Local and Global Climate Change on the Future Energy Cooling Consumption
• Chapter 3. Economic and Demographic Parameters Affecting the Future Cooling Energy Consumption
• Chapter 4. Predicting the Future Cooling Energy Consumption of Buildings
• Chapter 5. Future Energy Efficiency of Air Conditioning in Urban Environments
• Chapter 6. Renewable-energy-based Air Conditioning Systems
• Chapter 7. Smart Envelope Components to Decrease the Cooling Needs of Buildings
• Chapter 8. Recent Advances in Passive Cooling Techniques
• Chapter 9. Thermal Storage Cooling Technologies
• Chapter 10. How Urban Mitigation Technologies Can Contribute to Decrease the Cooling Demand of Buildings
• Index