HVAC technology in hotels has not only made great strides, but has also achieved environmentally sustainable designs, leading to better efficiencies, finds Sapna Kulshreshtha.
Heating, ventilation and air conditioning (HVAC) technology nowadays has become increasingly sophisticated and capable of meeting not only the needs of the most discriminating traveller, but also in achieving an environmentally sustainable design.
For example, Daikin has introduced technology that is ideal for buildings designed with large glass facades that instantly react to conditions outside, causing extreme fluctuations of temperature and, combined with increased thermal loads of lighting systems and other equipments in hotels, poses a huge challenge to the building’s cooling system.
Says Amitesh Poddar, sales manager for Daikin India, Maharashtra region: “We have introduced the Variable Refrigerant Volume (VRV) system which is a highly intelligent inverter-driven compressor. It is designed to deliver maximum efficiency during partial load conditions, and provide precise temperature control in all zones. It can also adapt to load variations such as changes in room occupancy or other impacts on temperature.”
Issues like user discomfort, improper ventilation, and sick building syndrome due to build up of pollutants in stale indoor air, are all linked to HVAC system design and operation, that can be improved by better mechanical and ventilation systems.
NC Malhotra, assistant vice president – projects and engineering services, The Lemon Tree Hotel Company, concurs: “The location and size of fresh air inlets and exhaust outlets, and keeping them apart at a safe distance, is an important factor while designing an HVAC system. Fresh air intakes should be so located as to avoid bringing in kitchen and toilet exhaust, and humid air around cooling towers.”
The type of filtration for fresh air is also important in terms of surroundings. It can range from simple HDP filters to carbon filters, depending on the quality of surrounding air. Ketaki Narain, director, corporate communications, The Oberoi Group, says: “Wet scrubbers have been installed in the generator and boiler exhaust systems in our hotels, to reduce the emission levels of sulphur dioxide, nitrogen oxide, and particulate matter in the surrounding air.”
Indoor air quality is also influenced by humidity, especially in areas where adding humidity-control can eliminate the potential for mould, mildew formation and bacteria growth. Humidity management can also play a huge part in the longevity of the room furnishings and ambience.
Most hotels install rotary desiccant dehumidifiers by which the fresh air is pre-cooled partially to the required level, and then passed over a heat exchanger coil fed with a cooling tower, to bring down the temperature to the desired level.
Such treatment units are cost effective, hygienic, and have an additional advantage of eliminating usage of chlorofluorocarbon (CFC) based systems to a large extent. Says Kundan Attarde, deputy chief engineer, Rodas ECOTEL Hotel, Mumbai:“We use R22 instead of CFC refrigerants for air conditioning, which is considered a more eco-friendly alternative.”
The HVAC system in hospitality tends to fall into two categories – that of independent air conditioning units, or centralised systems. Says Lavinder Duggal, proprietor, Magnum Air Cons: “Packaged Terminal Air Conditioners (PTACs) often seen in low budget hotels, provide complete climate control on the guests’ fingertips, and ensure low initial investment for the property owner. Unitised systems on the other hand, characterised by wall-mounted thermostats and separate HVAC unit, find favour in full-service hotels as they allow placement between a suite of rooms, thus providing better air distribution across a given space.”
Centralised air-conditioning remains the most adopted system for large hotels. It operates at a building-wide level and relies on one or more cooling towers, typically mounted on the roof of the property. Stating the advantages of central air-conditioning, Parish Kapse, director, Team One Architects, says: “In a centralised system, the chilled water is produced at a central space and distributed to the various rooms and spaces for cooling through appropriate air handling and fan coil units. This presents considerable scope for hotel design and innovation.”
Additionally, hotels are increasingly installing Building Automation System (BAS) where all equipment including pumps, air handling units (AHU) and cooling towers, are connected to the centralised system.
The BAS not only helps operate the AHUs but also automatically maintains the proper temperature, humidity, air flow, cooling tower, and water temperature and pressures. Says Vinayak Sane, director, Elmark Engineers:“In an intelligent cold water chiller, the power required to attain the desired set point would be less, as compared to a non-automated one.”
Moreover, the integration of the guest rooms with the hotel property management system enables staff to monitor and control HVAC based on occupancy, thus reducing energy costs.
In hotels like Taj Mahal Palace Hotel Mumbai, the fan coil units in guest rooms are operated by a stand-alone key switch, and temperature control is by means of a dual temperature setting thermostat. One setting is for occupied rooms at approximately 22oC, and the second at a slightly higher temperature of 24oC when the room is unoccupied, according to a company source.
Adds Pramoda Karkal, vice president and managing director, Johnson Controls India: “We provide the BAS which monitors and controls building utilities, and manufacture and install air conditioning systems with among the best input KW per ton of cooling. While monitoring provides information and control enables energy management, however, technological innovation in both BAS and AC systems are on-going.”
Further, the latest ‘intelligent thermostats’ for guestroom can detect a guest’s presence through body heat, and, when none is found, return to a pre-set temperature with a fixed setback system, returning quickly to the occupant’s desired setting within recovery time.
Likewise, the energy-saving PTACs from GE offers a heat sentinel, which kicks the cooling unit on once a certain high temperature is reached in the room, thereby cooling the room slowly rather than using maximum power to cool an overheated space.
As a matter of fact, nearly 60% of the air conditioning in a hotel goes to guest rooms that need to provide comfortable room temperature, humidity, and adequate ventilation for the occupants, with personalised controls and most importantly, equipment of low noise level.
Says Kapse: “AHUs on all floors are made of double skin construction with centrifugal fans mounted on vibration isolators, so that the noise level does not exceed 45-dbs.” As a good practice, ducted return air systems are now standard for most hotels, which not only helps to reduce the cooling load on the AHU but also avoids mixing of return air with other air, dust, and moisture, through openings in partitions above false ceilings.
Further, both supply and return air ducts of the air distribution system are insulated to reduce heat pick up from the surrounding air. Says Masih Siddiqui, chief engineer, Le Royal Meridien, Mumbai:“All our guest rooms and public areas are fed with cool, dehumidified fresh air, which is passed through treated fresh air (TFA) AHUs with an eight-row deep cooling coil, reheat coil, and high quality air filters. Toilets attached to guest rooms are exhausted at the rate of 60-cfm per toilet, thus maintaining a slight negative pressure in each room.”
For 24-hour spaces like lobbies – characterised by varying occupancy and outside air ingress – variation of the ventilation air according to the occupancy through modulation of the ventilation air damper, an Indoor Air Quality (IAQ) sensor, or a small packaged heat recovery device, could result in substantial energy savings.
In contrast, hotel restaurants have typically high lighting loads and strong food odours from display kitchens, all of which demand large amounts of ventilation air. Thus, hotels employ 100% outside air circulation with the supply-and-return fan, and an air-to-air heat recovery system that presents a viable and economic alternative.
For instance, Taj Mahal Palace Hotel, Mumbai has ozonisers installed in all bars where smoking is permitted as well as in restaurants with open kitchens, to eliminate odours. This maintains fresh air quantities at the recommended levels for proper health.
Says Varun Pahwa, executive vice president, Desiccant Rotors International: “TFAs and heat recovery wheels are being used by hotels like The Grand Hyatt, The Oberoi, Abott Hotel, and the Trident, among many others.
Heat recovery ventilators can recover large amounts of energy from the stale but conditioned air being exhausted out of the building, and focus on optimising the energy performance, resulting in considerable reduction in installed tonnage enhanced IAQ and productivity.”
Other areas like banquet halls and board rooms have design characteristics such as heavy and varying occupancy, very high lighting loads, and relative humidity management. Says Siddiqui: “The standard design for these spaces includes a system of variable speed drive to cope with varying occupancy, and an IAQ sensor to monitor and control the ventilation air quantity.
Alternatively, for health clubs that are very low occupancy areas, a variable volume system optimises the plant utilisation, while for gymnasiums it is preferable to have a separate air handling unit.”
Other challenges for HVAC designing include the grease in the kitchen and lint in the laundry. Says Attarde: “Our kitchen areas have independent supply and exhaust systems for the kitchen hoods, and are ventilated with 45–50 air changes per hour to maintain slightly negative pressure.
This prevents kitchen odours from polluting the dining areas, banquet halls, and the lobby, while the room service, vegetable, fish, and meat preparation, pastry and confectionery making areas are air conditioned using fan coil units with chilled water circulation.”
Likewise, in the laundry area, hotels install independent supply and exhaust systems for exhaust air from tumble dryers and flat work ironers, while a recirculation system maintains an ambient temperature.
The type of usable spaces in hotels too has drastically changed over the years, and hence, the most optimum solution is required to minimise the plant and equipment floor spaces.
Says Malhotra: “Most hotels locate plant rooms in the lowest basement as extended areas of other plant rooms such as electric substation, LT panel rooms, boilers, and water treatment plant, while making use of double heights available in the basement and other back-of-house areas to situate fans, AHUs and electrical panels, by creating accessible lofts.
Use of service floors for AHUs and fans, besides being used as transfer floors for services and location of cooling towers on the podium terrace to reduce pipe length and pumping energy, are also prevalent.”
Significant advances have been made in HVAC energy management and hotel operators approach HVAC efficiency in a number of different ways by reconsidering heating, cooling, and the air delivery systems, in their facilities. For instance, water cooled chilling units are most economical in terms of compact installation, longer life, and kilowatt per tonne refrigeration (kW/TR).
Having said that, the direct gas fired absorption chilling units in combination with screw or centrifugal chilling units, have become a strong candidate for very large hotels.
Says Narain: “Our hotels prefer the use of vapour absorption chillers instead of vapour compression chillers, as the refrigerant used in the former does not cause ozone depletion.”
Manufacturers too are becoming more environmentally conscious. Krishan Sachdev, director, marketing & strategy, Carrier Air conditioning & Refrigeration Ltd, explains that Carrier offers a wide range of environmentally responsible heating, AC and refrigeration products such as commercial chillers, that use a non-ozone depleting refrigerant and Bureau of Energy efficiency (BEE) star rated air-conditioning products.
Blue Star, which offers a complete range of R134A eco-friendly refrigerant chillers, is also the first company in the country to manufacture variable refrigerant flow (VRF) systems with digital scroll technology, indigenously.
Says Nitin Tiwari, sales head, Bluestar India – Mumbai & Goa: “These systems incorporate the eco-friendly R410A refrigerant and save substantial power, apart from their ability to handle harsh Indian summers.” He goes on to add that the VRF system is suitable for smaller hotels due to the cost factor, while water chillers are a more economical system for large properties.
Rajiv Puri, senior director, design management, Asia Pacific, Marriott International, says that there are very advanced water treatment/recycling systems also available now in the market.
“For urban hotels, commonly electrical driven central chiller plants are used, however, absorption chillers will be used when natural gas is available and cheap. For resort hotels, the use of individual DX system/units is common. Energy management innovations such as solar power, and natural energy like geothermal, and suchlike can be practically adopted as well.”
Similarly, installing variable-frequency drives on chillers, pumps, and cooling towers, improves cooling system efficiency. Adds Attarde: “Instead of using the boiler for hot water, we collect it through the air conditioning plant at heat recovery point at 50-degrees centigrade; heat pumps are used only during winters.”
Hotels are also using energy recovery devices for conditioning large quantities of fresh air. The advantage also includes the energy conservation equipment installed to recover 80% of energy required to condition such large quantities of fresh air. Says Niranjan Khatri, general manager, Welcomenviron Initiatives, ITC Hotels: “Waste heat recovery boiler equipment is connected to the exhaust of the generator, which is at around 500-degrees Celsius, so that heat can be recovered by this boiler and utilised in the HVAC system to produce hot water, or used in air conditioning.”
An effective tool in energy conservation is the double skin AHU with variable frequency drive and heat recovery wheels, particularly in high occupancy areas like banquet halls and meeting rooms that are instrumental in large energy savings. Additionally, a well-designed water distribution system with variable speed drive on all secondary pumps maintains comfortable temperature conditions in all areas and conserves energy.
Water-cooled chilling units require a large quantity of make-up water for cooling towers. Hence, water treated from a sewage treatment plant (STP) is the answer to achieve water conservation in hotels.
Moreover, the quantity and quality of water generated through STP for most hotels, is large enough to meet the needs of make-up water for the HVAC system cooling towers as well for horticulture. Khatri agrees: “Our STP plant treats all the waste water into good quality recycled water, that is used in the hotel for gardening and air-conditioning purposes.”
Undeniably, HVAC planning plays an important role in the overall hospitality design, as energy alone consumes about 8-12% of the revenue. An efficient HVAC system in a hotel can have the dual impact of cutting energy costs, as well as significantly improving guest comfort.
