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The dissertation investigates the scientific and business factors that have resulted in air-conditioning being a major contributor to climate-change. With his architectural background, the author demonstrates how a design methodology, not commonly adopted in scientific studies, may actually be a suitable way of dealing with a complex problem: the 'business as usual' scenario involving building science, sociological values and consumer behavior. Using his innovations as case studies, the author shows how good ideas cannot be evaluated on scientific merit alone and demonstrates why commercialization may have a pivotal role in deployment of research-based technology. He advances the theory of personalized thermal comfort which can potentially resolve the air-conditioning conundrum.



Chapter 1. Introduction

There is general recognition that the lifestyle in developed countries, typified by high levels of consumption and emissions, is not sustainable. In this multi-faceted problem, this thesis attempts to solve one part of the problem: the demand for thermal comfort in affluent tropical cities.

Tim Law

Chapter 2. The State of the World

In the fourth assessment report of the UN Intergovernmental Panel for Climate Change (IPCC), the

robust finding

(defined as that which ‘holds under a variety of approaches, methods, models and assumptions, and is expected to be relatively unaffected by uncertainties’ (IPCC, 2007, AR4 SYR - Topic 6)) was that ‘warming of the climate system is unequivocal,’ and that ‘most of the global average warming over the past 50 years is

very likely

due to anthropogenic Green House Gases (GHG) increases’ (IPCC, 2007, AR4, 6.1). The IPCC also identified the building industry as the one with the most climate mitigation potential (Table 2.1). When Time Magazine (Kluger,


) ran a special feature called

The Global Warming Survival Guide,

buildings accounted for the largest share of U.S. emissions, noting that:

Tim Law

Chapter 3. Literature Review: Thermal Comfort and Air-Conditioning

The cost of supplying energy to the office space has historically been insignificant compared to the cost of labour. A study on a typical American office (Holz et al. 1997) found the cost of salaries to be 100 times more than that of energy. In Singapore, the electrical consumption of offices accounts for 12 % of the overall non-manufacturing sector’s usage, with an average annual energy efficiency of 231 kWh/m


(Lee 2001). In an ongoing study by the Energy Sustainability Unit in Singapore ( the median office building uses 49 % of its energy on air-conditioning and a further 14 % on mechanical ventilation.

Tim Law

Chapter 4. Brain Cooling

In Genesis, the first book of the Bible, the fall of man is recorded and the consequence of labour and death is pronounced. The insights into the facility for brain cooling from eighteenth and nineteenth century commentators is remarkable:

Tim Law

Chapter 5. Comfort Energetics: Thermal Comfort Under Energy Constraints

This chapter represents an energy-conscious approach to understanding thermal comfort. With the environmental variable of T, MRT, RH and wind v as its structure, it begins with a psychrometric analysis where the roles of temperature and humidity are denominated in PMV votes and the power needed to improve those votes. The role of humidity is critically reviewed with a case made for challenging the accepted norms an optimum RH range. Finally the efficacy of moving air is analysed in the different ways it can be employed.

Tim Law

Chapter 6. Research Methodology



serves to appraise ‘already formulated pieces of knowledge, such as theories or steps in a research program’, this chapter is, strictly speaking, not about methodology in the deductivist sense.

Tim Law

Chapter 7. The Rain Tower

Rather than tinkering with small incremental improvements in the efficiency of air conditioning systems, we need a step change to new paradigms for cooling buildings. Just as with the cars, we need super-low-consumption, dual fuel, eco-buildings that are naturally ventilated in spring, winter and autumn, and in summer are run on solar air conditioning when the sun is out topped up by small amounts of grid electricity when it is not. This is the way forward. (Roaf


, p. 233)

Tim Law

Chapter 8. Finding a Market-Oriented Solution

In the previous chapter, a design methodology had emerged for the innovation process:

Using a design brief instead of an academic research question.

Adopting an action research cycle to improve the ideas: plan → act → observe → reflect → plan…

Utilising the architectural studio model of

the critique

as reflection, which involved:

self-critique, and

supervisors’ critique.

Tim Law

Chapter 9. Personal Air-Conditioning

Majority of air-conditioned offices rely on total volume air distribution (TVAD) to attain a fairly homogenised mix of fresh and recirculated air, supplied at temperature and velocity that would satisfy most occupants.

Tim Law

Chapter 10. Field Testing DTAC, Methodology and Results

The Ductless Task Air-Conditioning (DTAC) system was developed for supplementary personal cooling to office occupants. DTAC utilised thermoelectric (peltier) modules for heat exchange into a phase change material (PCM) as heat sink, allowing workspaces to be air-conditioned with no installation. The process of prototyping and optimising this unit is covered at length and in detail in Appendix.

Tim Law

Chapter 11. Future Research

Up to the end of this thesis the DTAC has been developed solely to improve personal thermal comfort by providing a stream of air that has been chilled a few degrees below ambient conditions. As a complete personal climate control solution it will have to address indoor air quality as well. Preliminary thoughts for the future design is illustrated in Fig. 11.1 with suggested IAQ improvement in Fig. 11.2. A two-stage IAQ improvement is proposed:

Tim Law

Chapter 12. Conclusion

I have written this thesis not only as a document for examination, but as an account of a four-year long research program. Thus, even though DTAC was the culmination of this program, this thesis is not about DTAC as a technology in itself.

Tim Law

Chapter 13. Appendix: Building and Optimising the DTAC

This appendix explains how the DTAC was developed and optimised in a step-wise process. The advances have been categorised by the components (instead of chronologically) for clarity.

Tim Law


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