مدل سازی مصرف برق و شیوه های صرفه جویی در انرژی چیلرهای هتل

Hotel buildings consume a significant amount of energy, especially their chiller systems. This study aims to create a model of the power consumption of the hotel chillers, and to identify the practical means to reduce the power usage of chillers. The examined parameters include air-conditioned floor area, guest floor area, gross floor area, number of employees, room occupancy, food cover, outdoor air temperature, window velocity, service type and relative humidity. It is anticipated that the developed modeling equation may provide a reference for hotel engineers to forecast any diagnostic problems and form a benchmarking indicator for comparing chillers’ energy efficiency. A survey of hotels in Shanghai was carried out to collect energy consumption data of chillers during air-conditioned cooling months. Regression analysis indicates that number of staff was a major and statistically accepted factor in explaining the electricity consumption of chiller in hotels. In addition, the paper discusses some means and suggestions in reducing chillers’ power consumption.

The close link between environmental effect and consumption of energy is an issue that has gained attention in the past decades. Most externalities of this issue are produced during the generation of electricity and its fuel exploitation. The principal air pollutants are emissions of carbon dioxide (CO2) or the principal “greenhouse gas,” sulfur dioxide (SO2), nitrogen oxide (NOx), ozone, and particulates (Chan et al., 2008, Chan and Lam, 2002a and Chan and Lam, 2002b). Shanghai, as a metropolitan city in China, faces these environmental problems as well. The continued economic boom and the growth of tourism activities in the city bring a significant increase in the number of high-rise hotel buildings and subsequent environmental problems. In fact, the hotels are major energy consumers. The heating ventilation and air-conditioning (HVAC) system in subtropical hotels consumes about 35–50% of electricity, which ranks it as the most energy-consuming facility (Chow and Chan, 1993). In high latitude countries, like the United Kingdom and Greece, their cooling facilities account for only 4–10% of the total energy usage in hotels (Energy Efficient Office, 1994 and Santamouris et al., 1996). In subtropical areas, Yu and Chan (2010) found that the operation of chillers and cooling towers leads to the peak electricity demand, and accounts for about half of the electricity consumption for air conditioning in hotels. However, a paucity of information exists in the relationship among electricity consumption, its associated parameters, and ways to save the power consumption of chillers. The establishment of the relationship between electricity usage and variables of the power consumption of chillers could enable hoteliers to predict electricity consumption. Predicting the amount of energy consumption may help form the benchmark for monitoring the energy usage and efficiency of chillers. Shanghai is the major gateway to mainland China and acts as the major engine for regional economic developments. The number of international visitors to Shanghai reached 8.5 million in 2010 (Shanghai Statistical Bureau, 2011), and this number is expected to grow in the coming decades. Hence, hotels play a significant role in the tourism and economic development of Shanghai. In 2009, the total number of hotels reached 298, which is twice the number in 1990 (China National Tourism Administration, 2010). While Shanghai is not located in the subtropical region, its six to seven months of summer hotness require the installation of air cooling facilities in hotels. The foreseeable increase of new hotels will bring huge energy consumption and its associated emission problems. In addition, the initial literature review indicated that previous investigations were confined to the study of the overall power usage and the associated parameters of the HVAC system, and did not look into the core energy consumption of the cooling system and its related parameters. This gap necessitates conducting the present study. Thus, the present study aims to create a model of the power consumption of the hotel chillers in Shanghai, and to identify the practical means to reduce the power usage of chillers.

A survey of the electricity consumption of chillers among the full service hotels in Shanghai was conducted. The data collected were used to investigate the relationship between the electricity usage of chillers and their associated parameters. Eleven completed questionnaires were used in the analysis. The results represent 20% of the 54 four-star hotels in Shanghai (China National Tourism Administration, 2009). Among the 11 investigated parameters, the study found that the number of hotel employees and outdoor temperature are the statistically significant and strongly correlated variables that affected the energy consumption of chillers. Among the three newly tested variables, the design of unequally sized chillers is a statistically validated parameter in the study. A generic modeling equation was established to create a benchmark for comparing the electricity consumption of chillers in hotels. The input data of all these major parameters are readily available in the operational reports of hotels. This finding implies that hotels can perform the modeling easily and quickly. The results in this area could serve as references for developing predictions on the electricity consumption of chillers in full-service hotels located in the coastal temperate regions, especially in eastern China. The established regression model could be further developed as a benchmark for hotels in the Zhejiang area in China. The study identified four approaches in lowering the electricity consumption of chillers, namely, condensing temperature control, optimal loading computation, unequally sized chillers, and variable speed control. The information could serve as a reference for hotel owners in improving the existing energy efficiency of chillers and the purchasing of chillers for future projects. A review of recently studied and published designs of chillers indicated that their electricity saving potential ranges from 3% to 10%. This reported saving potential could serve as a hint for hoteliers who evaluate the economic viability of incorporating these designs into their future and retrofitted chillers. Moreover, this investigation represents the first of its kind in the hospitality academia to explore the relationship between the power consumption of hotel chillers and its relevant parameters, and to highlight the practical means to save energy in that area. Driven by the growth of international and domestic travel plus the corresponding need for more environmental-friendly hotel accommodation, the findings and discussion in this study could serve as a reference for the old and new hotel operators. Following the open door policy of China and the subsequent economic and political reforms in the past three decades, the country has become the largest CO2 emitting country with 5.6 billion tons of CO2 emission in 2006, which accounted for 20% of the global emissions (Liu and Gallagher, 2010). In face of this situation and the possible reduction of this emission in the future, the Chinese government has set targets to cut her carbon emission by 40–45% lower than that of the 2005 level by 2020 (Yuan et al., 2011 and Stern and Jotzo, 2010). To achieve this target, the quantification of carbon intensity emitted by various sectors is required. Since hotels are classified in the building sector, individual hotels may be required to estimate the energy consumption of their chillers for benchmarking. If this happens, then the modeling exercise in this study would serve as a useful reference. Prospective scholars may consider using the same approach to investigate the relationship between chiller power usage and its associated variables but with a large sample size. This recommendation may help confirm and validate the results of the present study.