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Buildings are the dominant energy consumers in modern cities but their consumption can be largely cut back through improving efficiency, which is an effective means to lessen greenhouse gas emissions and slow down depletion of non-renewable energy resources. However, the potential energy cost saving alone is hardly a sufficient incentive to investing into improvement measures, unless the cost of using energy soars. People''s attitude will change with increasing concerns about the environment and sustainable development but the results remain insignificant. Surely, more effective means are needed to induce or compel greater efforts, especially to the signatories to the Kyoto Protocol. Whilst regulatory control is widely used, many believe that encouraging voluntary commitments is more cost effective in dealing with environmental problems. More researchers now favor the adoption of a well-articulated policy mix involving both regulatory and voluntary instruments. The paper describes a comprehensive literature review about regulatory and voluntary policy instruments related to building energy efficiency. Particular attention is given to the cost-effectiveness of these instruments, as reflected by the implementation experience of several countries, and a qualitative evaluation. The possibility and benefits of harmonizing governmental and private-sector schemes are discussed. [Copyright &y& Elsevier]

Within a given budget, selection of the optimal set of measures for enhancing the energy efficiency of a building is often based on the relative order of the feasible measures, prioritised according to either the life cycle cost saving or the economic benefit–cost ratio of the measures. A sensitivity analysis shows that, compared to the life cycle cost analysis, the benefit–cost ratio analysis is less susceptible to the influence of uncertainties in the estimates of the present value of the life cycle energy saving and cost. Where interactive measures are involved, the effects of some are dependent on the co-existence of other measures. The prioritisation determined according to the benefit–cost ratios of individual measures, each taken in the absence of all the others, can lead to the choice of a range of measures that is below optimal. Selection of the optimal set of energy efficiency enhancement measures requires a multistep approach, which is exemplified by the case study described in the paper. [Copyright &y& Elsevier]

Abstract: Water-cooled air-conditioning systems (WACS) are widely used in the commercial sector for energy efficiency, but not in the domestic sector. It has been found that there are no mathematical models and energy simulation programs to enable detailed investigation and evaluation into the energy performance of water-cooled air-conditioners. To improve the applicability of water-cooled air-conditioners in the domestic sector, the development of a prediction model for energy performance analysis is needed. This paper addresses the development of an empirical model for predicting the operational performance and energy consumption for the use of water-cooled air-conditioners. The model consists of four sub-models which has taken into account the energy consumption of the condenser water system. A prototype WACS was set up and tested in an environmental chamber to validate the resultant model. The overall COP of the WACS was found to be greater than 3 at 90% rated capacity. The predictions from the model compared well with the experimental results, with RMS error within 11%. [Copyright &y& Elsevier]

Abstract: The objective of this study is to conduct a realistic prediction of the potential energy saving for using water cooled air conditioners in residential buildings in Hong Kong. A split type air conditioner with air cooled (AAC) and water cooled (WAC) options was set up for experimental study at different indoor and outdoor conditions. The cooling output, power consumption and coefficient of performance (COP) of the two options were measured and calculated for comparison. The experimental results showed that the COP of the WAC is, on average, 17.4% higher than that of the AAC. The results were used to validate the mathematical models formulated for predicting the performance of WACs and AACs at different operating conditions and load characteristics. While the development of the mathematical models for WACs was reported in an earlier paper, this paper focuses on the experimental works for the AAC. The mathematical models were further used to predict the potential energy saving for application of WACs in residential buildings in Hong Kong. The predictions were based on actual building developments and realistic operating characteristics. The overall energy savings were estimated to be around 8.7% of the total electricity consumption for residential buildings in Hong Kong. Wider use of WACs in subtropical cities is, therefore, recommended. [Copyright &y& Elsevier]