Advanced Materials Research Online: 2013-06-27 ISSN: 1662-8985, Vols. 712-715, pp 1614-1618 doi:10.4028/www.scientific.net/amr.712-715.1614 2013 Trans Tech Publications, Switzerland The Energy Consumption Investigation of the Hotel Central Air-conditioning System and the Research of Energy Saving Measures Jiajia Ni, Li Tao*, Yijun Wang, Jinlei Wu College of petroleum engineering Changzhou University Changzhou, China taotaolili@126.com, lczmr@sina.cn Keywords: Central air conditioning; Energy consumption; Energy saving. Abstract. Through to investigation on present situation of the Changzhou Changrui Hotel air conditioning system energy consumption, by analysis the energy consumption, the power consumption of hotel central air-conditioning system charge 58% of the total electric, accounted for a large proportion. So we should take the necessary measures to reduce the expenses of air conditioning system energy consumption. According to the analysis of data on the survey, we put forward some particular energy-saving measures of central air-conditioning system of the hotel, including strengthening the building envelope insulation, energy saving technology of doors and windows, measures of roof energy saving, setting reasonable indoor temperature, adopting frequency control air-conditioning, reuse waste heat of the central air-conditioning, using the condensation water of central air conditioning to make-up water and reducing temperature of cooling tower, and drying the fresh air independently. Introduction With the rapid development of the productive forces, central air conditioning has become the common appliances in our daily life. It can improve quality of our life and bring us a comfortable living environment. But it also brings huge energy consumption at same time! In recent years, energy issues have become more and more seriously. In the summer, we often experience the situation of power cuts etc. So, in order to save energy and costs, the central air conditioning energy saving is particularly important. According to the data, in a modern building, central air-conditioning energy consumption accounts for about 50% of the total energy consumption of the entire building. Commercial buildings, hotels and complex may be up to 60%. And it is growing year by year. Therefore, the central air-conditioning energy saving has become a key issue in building energy efficiency. In fact, full load running time of the central air conditioning in a year is about only ten days, or even a few days. The vast majority of the rest time is running in the less than 70%. This way causes a huge waste of energy [1]. In order to save energy and costs, making a energy consumption survey on air conditioning units of refrigeration system and put forward reasonable energy-saving measures are necessary. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (#69814133, Pennsylvania State University, University Park, USA-18/09/16,13:54:06)
Advanced Materials Research Vols. 712-715 1615 Overview of hotel Changzhou Changrui hotel was the subject of study, and we make a survey on energy consumption. Central air conditioning system provides a comfortable indoor environment for clubs, accommodation and catering. Changzhou is located in the southern part of Jiangsu province. In summer, it is hot and rainy. The highest temperature is often above 36 C.In winter, the air is wet and cold. The design manual shows that the summer air conditioning outdoor dry bulb temperature is 34.6 C and wet bulb temperature is 28.6 C; winter air conditioning outdoor air dry bulb temperature is -5 C, relative humidity is 75%. Hotel central air-conditioning system opens every day and never stops. There are two cold sources for RTHD water-cooled screw chillers, and the cooling capacity is 500,000 Calories. The two units are running at the same time in the peak load. In the low load period, run the one unit. The running time is 9000 hours /year and 3000 hours / year. There are 15kW freezers, cooling water pump in the chiller plant. And there is no partition in the chilled water system. The form of hotel air conditioning system is air fan coil with fresh air system. The hotel has a temperature-controlled air conditioning end switch. It will automatically stop the end of the outlet working when the temperature is below the set value. The heating system's heat source is provided by two boiler. Investigation and analysis of energy consumption of the hotel From the beginning of January 2009, we start an investigation of this hotel energy costs. January 2009 to December 2011, energy costs is shown in Table 1 and shown in Fig. 1. From Table 1 and Fig.1, we can see the hotel average monthly electricity bill of about 40,000 Yuan. Central air-conditioning energy costs in 2009-2011 is shown in Table 1 and Fig. 2. According to the dates we collected in the research process, in 2009 to 2011, the hotel central air-conditioning system consumption costs accounts for 58% of the total costs, which is a large proportion. With the growing lack of energy, energy conservation is increasingly urgent problem. Therefore, it is necessary to take the appropriate energy-saving measures, to make the central air conditioning improve the utilization of energy which can reduce the energy costs. TABLE 1 ENERGY COSTS OF HOTEL FROM2009 TO2011 (YUAN) Time Total Energy Costs Central air conditioning system Energy Costs 2009 2010 2011 2009 2010 2011 January 49122 40844 41967 25052 20014 20479 February 50394 34951 38518 24693 17476 19682 March 41421 21769 28012 19758 10885 14282 April 24274 35397 28105 12137 17345 14018 May 22662 27389 20741 11558 13421 10402 June 39866 21747 37767 20730 10874 19929 July 55092 32710 40899 29199 17009 20955 August 65761 51770 63836 31565 26403 31825 September 72555 63586 64037 35552 31722 32502 October 40304 80181 41248 20152 40090 20569 November 14385 72879 23110 7049 36334 127333 December 52796 20610 18781 25870 10507 9365 Total 528632 503833 447021 263315 252076 341342
1616 Advances in Manufacturing Science and Engineering Fig.1Total Energy Cost of Hotel From2009 to2011 Fig.2 The pie Chart of Electric Cost for Central Air Conditioning of Hotel From2009 to2011 Energy-saving measures of hotel air conditioning system According to the research of the hotel air conditioning system energy consumption, you can put up some effective energy-saving measures. On the one hand, the design of the building envelope hotel itself, production and energy-saving building materials; On the other hand, is the design of the hotel air conditioning system, control and run to take energy-saving measures. 1) Enhanced Thermal Insulation of the Building Envelope Performance Improve building insulation performance can directly reduce building loads cooling and heating. According to the data [1], the heat transfer coefficient of the building envelope increases 1W/(m 2 K), if the other conditions under the same conditions, the air conditioning system design load will increase nearly 30%. Therefore, it s the best to improve the insulation performance of the building envelope of choices for energy-saving measures in the building design. 2) Doors and Windows, Energy-saving Technical Measures There are some measures, minimizing the area of the doors and windows, setting the shade facilities, improving the air tightness of the windows and doors, using energy-efficient doors and windows. Using new insulation thermal resistance, low energy consumption and energy-saving materials manufacturing energy-efficient windows and doors can greatly improve the thermal performance. Accounts from 20% to 30% of the maximum load of the air conditioning system, the consumption of cold exterior windows single glazed windows in winter heat consumption accounted for 10% to 20% of the heat load. It s very important to control the rate of the windows and walls in the premise of ensuring lighting and ventilation indoor. Generally north to not more than 25%, not more than 35% to the south, east to west is not greater than 30% [2]. 3) The Roof Energy-saving Technical Measures "Cold roof" has a significant energy saving effect. The so-called "cold roof" which refers to the ordinary roof coatings, coated with a high reflectance to improve rooftop solar radiation reflectance, reduce the absorption of the heat of the sun, and thus to decrease the cooling load and the air conditioning energy-saving purposes. The study shows that [3], the use of "cold roof, air-conditioning system load can be reduced by about 10% to 50%. In addition, it can be used on the roof overhead roofing, light-colored roofing and green roofs to save energy.
Advanced Materials Research Vols. 712-715 1617 4) Set Reasonable the Indoor Temperature Currently, most of the air-conditioned building set temperature from22 ~ 28 C, and some public buildings in lower air conditioning temperature, even lower than 22 C[4].In some regions, such as Guangzhou, Shanghai, summer indoor temperature lower 1 C or winter higher 1 C, which will bring an increase about 6% of investment in HVAC engineering, and energy consumption will increase by about 8%.In addition, increasing the indoor and outdoor temperature does not conform the requirements of the health, which is the main reason to "air conditioning disease. 5) Use the Frequency Conversion Air Conditioning Due to the major power equipment of central air-conditioning system is fans and pumps, so the best method of this equipment is energy saving inverter technology [5]. By using changing amount of water and variable air volume system to control central air conditioning system, can reduce the energy waste of water pumps and the fan constant speed running. Energy-saving effect is very obvious by changing amount of water and variable air volume.it obtained by pump and fan frequency conversion technology 6) Central Air Conditioning Condensate to the Cooling Tower Supplied by Water and Cooling The condensate water is made up of the dew condensed on the coil surface, whose temperature is higher than the local air dew point temperature, but lower than the tap water temperature. If it can be used to make up to cooling tower, both can improve the cooling effect of the cooling tower, also can solve the problem of losing water by evaporating [5]. According to the data [6], in order to achieve the same cooling capacity, cooling water inlet water temperature for each should add 1 C, and energy consumption should increase by 4%. If condensed water can be cooling water replenishment, which can reduce the cooling water inlet water temperature, and reduce energy consumption. 7) Independent Dehumidification of Fresh Air We make the independent dehumidification of fresh air to let loop processing unit work in dry condition. Then there is no cold surface condensation water and mildew on the surface cooler, which can improve air quality indoor. This can solve the problems of hot and cold offset reheat process thoroughly. While the temperature of the refrigerator does not need to be too low, to improve the COP of the refrigerator, which can achieve a greater degree of energy saving. Currently, this technology has been given adequate attention, and has been used in more occasions. 8) Recovery Heat of Central Air Conditioning System First, we can consider the use of heat recovery units to recover the heat in the cooling water system for heating or producing hot water for the hotel rooms, sauna, and staff bathrooms.not only reducing the heat pollution by the heat of condensation on the environment, but also reducing the running cost and the noise of the cooling tower. Second, recover the waste heat of the air exhaust system. According to the air quantity balance theory, we should supply a certain amount of fresh air to the building, and remove the indoor air of the same quantity in the hotel central air conditioning system at the same time. According to the research [7], if we set a heat exchanger in the air exhaust system. We can have the fresh air energy savings of 70% to 80%, equivalent to 10% to 20% of the air conditioning load.
1618 Advances in Manufacturing Science and Engineering Conclusion Changzhou Changrui hotel is the research object. According to the analysis shows that the energy consumption of the air conditioning system in the hotel is huge. With enhanced thermal insulation properties of the building envelope, energy-saving technical measures of the doors and windows, roof energy-saving technology measures, setting reasonable the indoor temperature, frequency conversion air conditioning, central air conditioning condensate to the cooling tower supplied by water and cooling, independent dehumidification of fresh air and recovery heat of central air conditioning system. All of them have the energy-saving effect, which can reduce the energy consumption expenditures effectively. The methods above, the building envelope to increase the insulation layer and the roof overhead roof, light-colored roof, planted roof, all of them are simple and easy to carry out. And has a fast cost recovery, energy-saving effect, which is suitable for the transformation of the hotel construction. For the non-construction of the hotel, it can use the multiple energy-saving technologies. It will bring a large number of energy cost savings for the hotel, and good economic benefits. Frequency conversion technology and independent dehumidification of fresh air can be highly energy-efficient. These energy-saving measures have been adopted in many air conditioning systems. I believe that these energy saving technologies will become the development direction of energy saving in the hotel in the future. The promotion of energy-saving technology of central air-conditioning system in the hotel, there are obvious advantages and effectiveness of social economic and environmental development, which can achieve the harmonious development of human and the environment. So it achieves the purpose of energy saving and emission reduction. References [1] Chen Wen,Yuan Lixin.. Construction Conserves Energy, vol.35(2007), p.46-50. In Chinese. [2]Wang Lilong,Liu Dan. Refrigeration Air Conditioning& Electric Power Machinery, vol.28(2007), p.41-45. In Chinese. [3] Wu Xuhui, Chen Kun, Chen Limei. Shanxi Architecture, vol.35(2009), p.213-214. In Chinese. [4] Shen Yanhui, Wang Lei, Chen Qian. Science & Technology Information, (2010), p.86-87. In Chinese. [5] Zhou Hongyu, Chen Xiaojian, Chen Zihu. Control Engineering Of China, vol.18(2011), p.474-478. In Chinese. [6] Li Longtian, Ran Hao. China Science And Technology Review, (2007), p.119. In Chinese. [7] Dong Naijin, Xu Chuanhan. Application and economic of exhaust heat recovery. the First Annual Conference Proceedings in Wuhan. Wuhan CAST First Annual Conference in Wuhan, 2004,p. 189-192. In Chinese.