Achieving energy efficiency in a hotel through implementation of intelligent fan coil unit and an extra bedside temperature control

Transcription

1 Achieving energy efficiency in a hotel through implementation of intelligent fan coil unit and an extra bedside temperature control Antonio C. M. Chan (1), Carmen Y. S. Wong (2), Vincent Lau (3), Ken H. K. Pong (4) 1. antoniochan@rec-eng.com 2. carmenwong@rec-eng.com 3. vincentlau@rec-eng.com 4. ken.pong@goldenmile.com (1) REC Engineering Co., Ltd., Hong Kong. (2), (3) REC Green Technologies Co., Ltd., Hong Kong. (4) Holiday Inn Golden Mile, Hong Kong. Abstract This Paper presents the engineering essence and energy saving performance of Intelligent Fan Coil Unit (also known as ifcu ) with an extra bedside temperature control implemented in an existing hotel in Hong Kong. In a typical air-conditioning system of a commercial or a hotel building in Hong Kong, the quantity of fan coil units (hereafter FCU) normally exceeds 200 nos. For such a FCU powered by a traditional AC motor, the energy consumption is about 85W at low speed. Throughout 7/24 operation, the annual energy consumption for 200 FCU could reach up to 148,920 kwh. During the design stage of renovation project for 3-floor guestroom, the building owner initiated the enhanced energy efficiency design concept, by using ifcu and provision of an extra bedside temperature controller in each guestroom. With the application of ifcu, energy saving can achieve 55-61% of fan coil unit system in the guestroom. The result was proven by a trial test for a 1-month energy consumption comparison under normal guestroom occupancy practice. In addition to the energy saving feature of ifcu TM, another highlighted feature was the provision of bedside temperature controller. In a typical design, the temperature controller will be installed on the corridor side of an interior wall in the guestroom. The purpose of the extra bedside controller is to provide a handy way for altering the room temperature set point during bedtime. Another trial test was conducted to summarize the temperature set point alteration frequency between the midnight to morning (i.e.00:00-06:00). During 178

2 the test, the room temperature set point alteration frequency in night time was averaging to 7.25 times in the 1-month trial period. It is indicated that the temperature set point changed from high to low, which can help to lower the cooling load at night time if the extra provision is existed. Upon the implementation of ifcu TM and extra bedside temperature controller, the energy consumption can be achieved 52-66% of its system is recorded. The presented case provides solid evidence of the energy savings of such implementation; it can help the building owner and engineering team to make decision to apply the same design concept to other floor to improving energy efficiency in the building at a short payback period. Keywords Energy efficiency; intelligent fan coil unit; ifcu TM ; hotel. 1 Introduction The project was introduced upon the planned renovation of three floors guest rooms in Holiday Inn Golden Mile (HIGM), which is located in 50 Nathan Road, Tsim Sha Tsui, Hong Kong. It was the top management of HIGM, headed by Ir Martin Wan of Director of Engineering, that is highly admires in energy efficient products/systems application in the hotel daily operation and it was considered the guest room renovation project is a golden opportunity to revamp the guest room energy consumption performance as well as the overall system energy efficient operation. The HVAC system undoubtedly is the major energy consumer in the HIGM operation, which is among 55.8% of the total energy consumption. Among the HVAC system energy consumption, about 4% is consumed by the guest room FCU. During the guest room renovation project, there were numerous items planned for renovation and the aged AC motor driven FCU is definitely a major renovation item in the project. The HIGM management considers applying ifcu TM for energy saving operation while the human comfort can also be elevated due to enhanced temperature control ability in variable speed driven ifcu TM. 2 ifcu TM characteristics ifcu TM is a intelligent fan coil unit which is equipped with the permanent magnet (PM) motor, power electronic drive and micro processor control that can adjust its operation level with reference to daily activities of occupants, with a view to achieve maximized energy efficiency over 80% and provide better comfort to occupants. The efficiency of the conventional alternating current motor is around 40% at high speed range 179

3 while that of the PM motor could be around 80%. Furthermore, the efficiency of a conventional alternating current motor at mid and low speed ranges can only be around 35% while the PM motor will maintain 80% efficiency. Hence, the saving rate at mid and low speed ranges could be over 50%. In addition, the ifcu TM concept could improve the air-conditioning comfort level to a desired standard with variable motor speed control. ifcu TM is capable to solve the problem encountered of conventional AC fan coil unit such as temperature control inaccuracy, noisy, shorter life span etc. Comparison of energy consumption and other parameters between conventional AC fan coil unit and ifcu TM are shown in Figure 1 and Figure 2. Temperature control comparison between ifcu TM and AC FCU. Figure 1 - Power consumption comparison of ifcu TM vs AC FCU Figure 2 - Temperature control comparison of ifcu TM and AC FCU 3 Initial trial on site In order to verify the claimed saving of ifcu TM, a on-site trial was set up during initial stage of the renovation project. The trial was scheduled in November 2014, which the renovation project was partially completed. The general trial set up is illustrated as the 180

4 following: - i. 2 rooms are selected at 6 th floor, which the guest room FCU is driven by AC FCU. ii. 2 rooms are selected at 18 th floor, which the guest room FCU is driven by ifcu TM. iii. The following parameters are collected in the selected 8 rooms for further analyses: i) Energy consumption of FCU ii) Set temperature of FCU (for 18 th floor only) iii) Return air temperature measured at FCU return air plenum iv) Relative humidity measured at FCU return air plenum iv. The test shall be conducted between 7~14 days and the specified parameters within the period shall be measured. There were two guest rooms selected at 6 th floor selected, namely 622 and 625 respectively. In order to minimize the variance between the lower and upper floor guest room, the same room no. of 1822 and 1825 at 18 th floor were selected for the trial. The following are the graphs showing the trending of the collected data in various guest room:- Figure 3 - Room 622 logged data Figure 4 - Room 625 logged data Figure 5 - Room 1822 logged Figure 6 - Room 1825 logged 181

5 3.1 Result analysis The logged data is summarized as the following: - Table 1 - Logged data summary of initial trial Data logged from 6 Nov to 19 Nov 14 Room Unit Average Temperature C Average Relative Humidity % Initial Meter Reading kwh Ending Meter Reading kwh Net Consumption kwh Total Run Hour hr Hourly Energy Consumption kwh/hr Energy Saving Compare to Average % 70.17% 60.77% Unoccupied Hour Unoccupied Hour Proportion 37% 35% "Auto" Mode Active Hour "Auto" Mode Proportion 44% 87% Average Consumption of AC FCU kwh/hr Average Consumption of ifcu kwh/hr Hourly Energy Saving Proportion % 65.47% According to the trial result, the average energy saving proportion of ifcu TM was about 65%, which is matching with the ifcu TM claimed saving rate of 40-80% among high speed to low speed setting. The trial also indicated the unoccupied proportion of each FCU was about 35% of its total operation hour. Another interesting finding is the Auto mode active time was highly varied ranging from 44% to 87%. With such observation, we can conclude that there is room for improvement on user s anticipation level of Auto mode operation, which will further enhance in energy consumption of ifcu TM operation. While the energy saving results are matching with the expectation, the human comfort factors are evenly important among the FCU operation as it is directly affecting the user s experience in the guest room. As observed in the logged data, the average temperature and RH among ifcu TM conditioned rooms are evenly matched with those AC FCU conditioned room. In such manner, the indoor environment of ifcu TM conditioned room didn t sacrifice for the sake of energy saving operation as observed in the trial. 182

6 4 2 nd trial after 1 year operation With the completion of three floors guest room renovation in Dec 2014, 109 sets of ifcu TM have put in full operation upon re-opening of renovated guest floors. There was a post-occupied trial arranged in April to May 2015, which is about 6 months after full operation of ifcu TM s in the renovated floors. In view to enhance the reliability of the trial results, the trial sample was expanded to eight units, which four guest rooms were selected in 6 th and 18 th floors respectively. The trial period was also extended to 1 month that the log data consistency and reliability will further enhanced. Table 2 - Logged data summary of post-occupied trial Data logged from 4 Apr to 6 May 15 Room Unit Initial Meter Reading kwh Ending Meter kwh Reading Net Consumption kwh Total Run Hour hr Hourly Energy kwh/hr Consumption Energy Saving Compare to Average % Average Consumption of AC FCU kwh/hr <- (corrected by ignored 622 and 625) Average Consumption of ifcu TM kwh/hr Hourly Energy Saving % Corrected figure According to the logged data, the hourly energy saving recorded about 7% reductions from the first trial result. There is a critical factor leading to such reduction as the occupancy of room 622 and 625 were significantly below average during the trial period. Such finding was substantiate by the logged hourly energy consumption of about 0.03kWH/hr, which is 40% lower than the result in first trial as well as the other AC FCU conditioned rooms of 620 & 621 in the same trial. By ignoring the energy consumption of room 622 and 625, the ifcu TM energy saving will be corrected to 67%. In this connection, it is concluded that the ifcu TM energy saving performance is maintained after 6 months full-operation. 183

7 Figure 7 - Room 1820 logged data Figure 8 - Room 1821 logged data Figure 9 - Room 1822 logged data Figure 10 - Room 1825 logged data From the observation of the above graphs, the room temperature is generally followed the user s temperature setting, which accounted to 52.5% of time the room temperature is within 0.5 C of the user s setting temperature (i.e. setting temperature between C). There is another unique feature focusing in the 2 nd trial. Unlike typical FCU installation for hotel guest room that one wall mounted thermostat/control console is installed for controlling the room FCU, there is a second bed side room temperature controller installed for the guest s ease of altering the room temperature setting during the bed time. The changes of temperature set point during the sleeping time that is from 00:00 to 06:00 daily, is considered changes thru the use of bedside temperature controller, for the evaluation of the effectiveness of the bedside room temperature controller at each ifcu TM conditioned guest rooms. The setting temperature change within 00:00-06:00 daily is summarized as below: - 184

8 Figure 11 Bedside temperature controller Table 3 - Bedside temperature controller adjustment in post-occupied trial Bedside temperature controller adjustment from 4 Apr to 6 May 15 Temperature set point changes during 00:00-06:00 Room Unit times Setting upward times Setting downward times Setting adjustment proportion % As observed in the trial logging, the application proportion of bedside temperature controller is about 23.5% in average. Among those temperature setting changes between 00:00-06:00, the number of upward changes and downward changes are evenly matched with the proportion of downward changes is about 11% more than upward changes. In such observation, the bedside temperature controller can offer substantial user s convenient for night time temperature setting changes while effective energy use for elimination of excessive cooling load demand. 5 Conclusions The PM motor driven ifcu TM, its actual energy saving potential for real life application has been demonstrated through the trails in the HIGM. The energy saving for guestroom ifcu TM application was about 65.47% upon the 1-week trial held on the partial completion of the guest room renovation project. While the system put in full operation for half a year, the energy saving was raised to 67.13% (after corrected by ignoring abnormal figures from low occupancy rooms). According to the level of saving of the latest trial, the HIGM can save about 188,000 kwh of the FCU energy consumption recorded in 2015 figure for full replacement of 621 sets of guestroom 185

9 FCU. The unique feature of bedside temperature controller in the renovated rooms provide a convenient user control in room setting temperature during bedtime, that hugely enhance the user s experience in the guest room. More importantly, such feature facilitates quick reflection of system loading towards the users oriented room temperature setting at each renovated rooms, which leading to accurate system loading control for ensure energy efficient central chiller plant operation. The highly efficient ifcu TM consumed less than 0.3W per l/s Ref 2, which is far below the requirement stated in latest edition of Code of Practices for Energy Efficiency of Building Services Installation 2015 (BEC 2015) Ref 1 stated requirement of 2.1W per l/s for system fan motor power of VAV system. More importantly, this is ensuring the ifcu TM will fulfill the BEC requirement in fan motor power to a more stringent level in the future. 6 Acknowledgement Ir Martin Wan- Area Director of Engineering/Director of Engineering- Intercontinental Hotel Group/Holiday Inn Golden Mile, Hong Kong. 7 References 1. EMSD, Code of Practices for Energy Efficiency of Building Services Installation REC Green Technologies Co., Ltd., Intelligent Fan Coil Unit (ifcu TM ) product catalogue