A significant amount of energy is spent from HVAC (Heating, Ventilation and air Conditioning) Systems used in hotels globally. As per a report by Hong Kong SAR Government, approximate 17% of the total energy, which in turn signifies around one third of the total electric energy, is consumed by the HVAC Systems of hotels in Hong Kong, in 2006 (HK Gov, 2016). Hence, taking strategies to use more energy efficient HVAC systems and reengineering strategies will help in generation of maximum value from the least amount of resources spent.
The aim of this paper is to compare objectively, the Chiller system and the VRV system adopted generally by Hong Kong hotels and understand which system is more effectively especially for hotels which contain three or more towers. The comparisons would be based on a number of aspects – namely, the efficiency of the HVAC systems used, the size of the system implemented, the cost of installation, maintenance, short term and long term impacts and will also aim to understand the carbon footprint of every system utilized. Based on such criterion, the final recommendation of the ideal system would be made.
The report will be divided into four main segments – the first segment is the introduction which would present the aim and the brief background of the topic; the second is the background which will present a brief review of published literature in the field of energy consumption of HVAC systems in Hong Kong’s hotel industry, and thereby would set the rationale of this project; third segment is the Analysis segment which will present the actual comparison and help choose the right solution and lastly the Conclusion and Recommendations segment would be presented which will highlight the strategies to be followed and prove to be beneficial for hotel industries worldwide irrespective of any specific region.
The importance of energy conservation cannot be stressed upon enough in the present environment (Gossling, Garrod, Aall, Hille, & Peeters, 2011). There are five aspects which determine the energy usage of an HVAC System. These are – the layout and design of the building which impacts the internal temperature and the humidity; the indoor temperature and the air quality and the required aspect of it namely, more the extreme temperatures, higher precision and more refined systems of air quality is required which consumes more energy; the generated internal heat from lighting, people and equipments all result in the warmth generated in the internal atmosphere; efficiency and design of the HVAC plant provides optimum moisture control, cooling and heating aspects required by the building and lastly, the operating times of the HVAC and the ability to use the controls also determined the energy usage (Perez-Lombard, Otiz, & Pout, 2008). A number of efforts have been made to reduce the energy usage by HVAC systems. As per Marriott in 2006, three approaches were present to enhance energy efficiency – optimizing the air flow temperature, energy recovering from the water in the condenser and using the geothermal pump mechanism (Foucquier, Robert, Suard, Stephan, & Jay, 2013). In 2006 again, Chan proposed an optimal control feature for HVAC systems of Hong Kong buildings, which lowered the demand of the cooling load and chilled water flows (Chan & Chow, 2004). Matthews et al, in 2002, apart from machine’s energy efficiency, the strategy of control also helps in resulting significant energy conservation (Li, Yang, & Lam, 2013). Of the overall review of literature, majority of studies were conducted in office and residential buildings but very less studies have been conducted on hotels and hospitality sector. Hospitality industry also consumers huge volumes of energy in tourist cities, like Hong Kong and hence this serves as a critical sector in which energy conservation must take place.
However it is an easier said than done process as the energy performance of hotel buildings is difficult to investigate and compare, as they have different structural designs, functional facilities and requirements stemming from operations (Astrumsolar, 2013). A number of aspects impact the energy consumption in hotels namely, - star rating, number of rooms, carpet area, conference facilities, laundries and swimming pools, levels of occupancy, retail operations etc. However, for the purpose of this paper, chiller systems and VRV systems are to be compared in hotels which have the following features – three towers, restaurants, lobbies, car parks, ball rooms, gyms, lifts etc and consist of EL / ELV rooms, AHU and PAU rooms, boiler rooms irrespective of gas fire or boiler types, sprinkler water tanks, F.S, pump rooms, rooms for collection of rain waters etc.
Typically, chillers consist of reservoirs which is filled with a fluid namely, water or ethylene glycol, or a mixture of both which is continuously circulated. In a building setting, such chilled water / liquid is circulated through the air-handler equipments or the chilled beams in an attempt to transfer the heat arising from air to water or the other way, that is, cooling transferred from the water to that of building air. Chillers are of two types – absorption chillers and the compression chillers based on the specific refrigerant cycle on which work is done (Jayamaha, 2006). Absorption chillers are machines which operate based on the cycle of vapour absorption and refrigeration and consists of four key exchangers of heat – generators, condensers, evaporators and lastly absorbers with two different kinds of solutions – the refrigerant and the absorbent. In a vapour compression chiller, the refrigerant gets in its vapour state by absorbing heat from the cooled water in evaporator. This refrigerant comes out of the evaporator in the vaporous state but on the other hand, extremely chilled water in produced. Therefore, heat is added to the refrigerant at a continuous pressure but similarly is extracted from the chilled water and these two don’t get mixed and are separated by a solid separator wall in between (Fong, Hanby, & Chow, 2006).
This VRV / VRF System is one of the most exclusive system of air-conditioning and is very well developed and sophisticated based on the following aspects – presence of a single refrigerant where it serves as the coolant material in the system; presence of inverter compressors which allow lowering of the consumption of power / energy with incomplete heating/cooling loads ; presence of several air handlers which act as indoor units on the very same refrigerant circuit and lastly, it has the ability of expansion modularly and finds immense applications for larger projects and processes.
A typical VRV / VRF System consists of the following – an outdoor unit which can comprise of one or more than one processors, a number of indoor units which are often known as fan coils, the refrigerant piping which runs from the outdoor unit to that of all the indoor units consisting of copper distributers in pipes and the wiring which forms the communication channel between all the individual parts. The communication wiring in turn is made up of two cables which forms a closed network of loops and this structure is fundamental for all VRF Units. The main logic of operation for a VRF system is build inside the system and is different for different manufacturers. The user provides input to the system and as per the data, it implements its logic to reach the desired temperature using very optimal power expenditure (Pan, Yin, & Huang, 2008).
Since VRV Function was mentioned herein, the specific technology by Daikin, has four significant strengths – the inverter technology and the precise control of the individual leads to significant energy conservation and less energy expenditure; adaptable design which helps in customizations as per the structure of the building; provides individual control whereby specific zones can have their own preferred climate and is ideal for commercial usage purpose and lastly the flexible layout, helps more in the use in large commercial and institutional places. Hence, for hotel industry, VRV system is definitely a better solution apparently. Technologically, this system consists of five factors – it provides a small type of large capacity compressor of inverter; it has a very highly integrated system of heat exchange; system promotes large airflow, quiet technology and a high static pressure externally; it has efficient automatic testing operations and lastly, it helps in improving the reliability as very high ambient temperatures.
Hotel Industry of Hong Kong
Comparison between Chiller System & VRV System
Primarily, VRF Systems are easier to install in comparison to Chillers (Goetzler, 2007). Chillers often require large cranes for installation, whereas in the case of VRF, the systems and individual units are lightweight and can be transported easily and have no problem in fitting into standard sized elevators. A number of the units can be used to cool in capacities of hundreds of tons. This relatively light weight of the units often do not require the reinforcement of the structural roofs, thereby making installation cost effective and labour effective. Ductwork is only required only for ventilation and hence, it reduces the building costs and height. VRF Systems are also efficient in retrofitting traditional buildings with operable windows and do not disturb the overall architecture and since the outdoor units are placed outside the building, no requirement for machine room is there thus saving space and maintenance costs (Teke & Timur, 2014).
VRF /VRV Systems are more flexible in designs as a single unit for condensation can be linked to a number of indoor units of different capacities and configurations and this modularity aspect also helps in adapting the HVAC System to reconfigure or expand. In comparison chiller systems once established lack this kind of flexibility (Aynur, 2010).
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Comfort is a relative feature, but VRF Systems help in reaching the accurate temperature and can maintain different temperature zones within a building. This makes the system to be more comfortable than the traditional chiller systems. Also Chiller Systems involve a specific noise due to the presence of a number of fans in its operations, whereas VRV Systems have low noise levels (Bhatia, 2011).
Energy efficiency is a game changer and it helps the potential users to choose between Chiller Systems or VRF Systems. Energy efficiency of VRV comes from a number of aspects. This system effectively eliminates duct losses and enables modulation of wide capacity. This specific approach helps in yielding high efficiency in part loading and translates into energy efficiency which is seasonal (Zhou, Wu, Wang, Shiochi, & Li, 2008). However, in certain cases of large spaces and larger structures, Chiller systems are considered to be more energy efficient as it produces larger cooling / heating from moderately small amount of electricity. VRF Systems are more suitable for smaller spaces and does effective cooling /heating. However, measuring the electricity expenditure and setting up systems for it is simple and cheaper in the case of VRF Systems in comparison to Chiller Systems (Teke & Timur, 2014). When it comes to large cooling purpose, chillers have higher COP or Coefficient of Performance, meaning for every unit of electricity spent more cooling is achieved. In VRF systems however, refrigerant is directly used as both the heat transfer fluid as well as the working fluid, and this makes the system more efficient than others which use water or air as the heat transfer fluid for the heating or cooling purposes. Hence, cooling spaces through VRV systems are done in an more efficient fashion as the refrigerant coolers don’t result in heat losses, which is a regular feature of chillers. When this is combined with supplies, energy will be saved. However, subtle energy efficiencies occur when VRF Systems are installed – namely, reduction in the losses of ducts, improved partial load efficiency, submetering etc (Aynur, 2010).
Chilled systems are known to provide better air quality than VRF Systems, and this forms a significant choosing criteria. In hot and humid nations, people sweat and this results in build up of bacteria and parasites, hence, if humid air is continuously circulated, it might bring about sickness and conditions of allergy and creating the ambience unhygienic. AHU is present in chillers which result in dehumidifying the air and rendering it fresh and breathable.
Installation costs for both chiller as well as VRF Systems are highly variable as they are dependent on the projects, and are quite difficult to pinpoint. As per certain studies, the installation costs of VRF Systems are expected to be slightly higher than chillers, but the actual real costs are dependent on projects. However, replacing a chiller system of an old structure with that of a new chiller system will be less expensive than installing a new VRF and systems of ventilation. The main cost issue lies in the fact that, VRF would require new system of refrigerant piping while the water piping of chillers would already be installed in the old structures (Goetzler, 2007).
The above mentioned specifications make a separate case for Chiller and VRF Systems. VRF Systems are more sophisticated, easier to install, cheaper to maintain and though initial costs can be higher but till they will be economically viable in the long run. Accurate temperatures, maintaining multiple zone temperatures and energy efficiency can be obtained more for VRF Systems than chiller systems. Hence, depending on the situation provided, it is recommended that a VRF / VRV System be chosen for Hong Kong hotels where there are a minimum 3 towers, and a large number of facilities are in place. The rationale for such
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