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Choosing The Right HVAC

The surge in industrial growth and technological advancements has resulted in a widespread move into cities and the expansion of city limits. By 2050, the number of urban residents is expected to increase exponentially (6.3 billion). Cities account for 60-80 per cent of global energy consumption and 75 per cent of carbon emissions, and this alarming growth will inevitably increase the pressure on the climate.

Heating, Ventilation & Air Conditioning (HVAC) infrastructure in today’s buildings are a critical piece of the puzzle that goes into making buildings green and eco-friendly. Selecting the right HVAC design for this can make all the difference to the carbon emissions levels of the buildings.

Importance of HVAC
HVAC has become integral to the modern idea of buildings. Be it heat dissipation or cost of implementation of systems; a lot has to be considered while designing a building. Most of these aspects fall under HVAC selection for the building as it is directly related to human health and level of comfort.

“Mostly people limit this aspect to measurement of gases, particles and temperature but also moisture, humidity and radiant heat are very crucial parameters that must be considered. It is very necessary to ensure that the energy consumption is very optimal in the buildings in order to save the cost,” informs Vimal Chavda, Manager – Distribution Sales, Testo India.

Today, people spend about 90 per cent of their lives in buildings – not just their own residence, but also offices, production facilities, schools and universities etc. HVAC products and solutions one needs to make these buildings habitable with safe, reliable and a comfortable atmosphere.

With large scale proliferation of computers in daily life, increasing level of particulate pollution and upgraded lifestyles, air conditioning systems (HVAC systems) are no longer luxury commodities.

Amit Bhardwaj, Business Head – Building Products, Siemens Ltd, informs, “Of the many critical solutions required for any building installation, HVAC is a key focus as it consumes more than half the energy cost. Our customers need to optimise their energy consumption, maintain a healthy and productive environment, update aging facilities and have anytime or anywhere access to their building systems.”

Anuraaga Chandra, Head- Cooling Sales, India Region, Danfoss Industries, emphasises on careful scrutiny of each feature and equipment within the HVAC system during selection process. He further adds that each equipment of the system works in coordination to achieve the desired energy efficiency and long-term profitability goals of the building.

The right chillers must be selected based on their full load and part load efficiencies; variable speed solutions for fans, compressors and pumps must be used that can operate at varying loads; a dedicated outdoor air system can help reduce the energy consumption as compared to a mixed air system; close control systems are helpful to achieve higher reliability, better temperature and humidity control etc. Additionally, smart chillers with oil-free compressor technology and in-built diagnostics are available which helps in getting consistent energy performance over the years when compared to conventional technologies, he further adds.

Considerations for Selection of HVAC System
Tejwant Navalkar, MEP Design Head, Godrej – Green Building Consultancy Services states that the process of selection of an appropriate system, today remains largely rule of thumb and influenced by the AC vendors. This is true, especially, in residential and small and medium offices or shops. The selection, therefore, is oversized, to ensure that the user is never feeling hot and the result is that the user gets high electricity bills.

He briefs the following factors that affect the sizing of an air-conditioning system:

• Use of the conditioned space, whether comfort residential or office, process requirement or data centre or restaurant, banquet hall or theatre,
• Orientation of conditioned space with respect to the sun path.
• Extent of exposed walls, windows and ceilings.
• Expected population, lighting loads, equipment loads and the area and height of the space.
• Fresh air requirements in the conditioned space.
• Usage pattern of the conditioned space is it uniformly occupied or is there a likelihood of sudden peak loads, eg a foyer in a hotel, a banquet hall, a theatre.

After selecting the size of the HVAC system, Navalkar, states the following options for choosing the type of air conditioning system that would be ideally suited for the application.
• Window air conditioners or Split Unit – ideally suited for small shops and residential flats.
Today, special purpose air conditioners are available to cater to high sensible heat applications like data centres, computer rooms, equipment room etc.
• Variable Refrigerant Flow or Volume (VRF/ VRV) systems which provide for connecting multiple indoor units to a single outdoor unit. These are ideally suited for small and medium offices.
• Ductable Package Units – generally used to provide air conditioning to large areas like shopping malls, restaurants where air conditioning load is uniform for majority of the operating periods.
• Precision Air Conditioning Systems (CRAC – Computer Room Air Conditioners) are also available, specifically, for server rooms, where the humidity and temperature arecontrolled in a very precise manner to meet the stringent requirements of these spaces.
• Centralised Chilled Water systems, where chilled water is used to chill the air which is circulated in the space to be conditioned. The centralised chilled water system could be either air cooled or water cooled. The choice would depend on the availability of water in the area.
• In Radiant Cooling system, the sensible heat from the space is removed by chilled water flowing in pipes embedded either in ceiling slabs or floor slabs. However, this option is the best implemented at the stage of slab casting, and this cooling has to be supplemented by the conventional systems to remove the latent heat in the room.
• One more recent trend is use of chilled beams, where chilled water flowing in pipes, passes through heat exchangers which cools the air causing convective movement of hot and cold air causing cooling in the space. The major difference in this type of approach is lack of use of fans whereby, fan energy is reduced. Chilled beam systems are ideally suited for high sensible heat applications or to supplement the conventional cooling systems.
• One of older techniques of incorporating cold wells in the entralised chilled water-based air conditioning system is being forgotten and hardly used in any of the new HVAC installations. In this approach, a large insulated tank is introduced which acts like a thermal storage, which is maintained at the desired chiller supply temperature. By introducing the thermal storage, we ensure that the chillers operate at full loads at majority of the times. The cold well, also acts like a short duration buffer in case of power outage and provides cooling during the transition from grid supply to DG supply.

He further mentions that the choice of a compressor decides the amount of energy that will be consumed in its operation. The choices for compressors are:
Reciprocating: The earliest and oldest in the family of compressors, these are the most inefficient and have been virtually phased out and can be seen only in window air conditioners and smaller split units.
Scroll: These are rotary type and are used in small AC systems upto 25TR. Most window air conditioners and split units use scroll compressors.
Screw: These are also rotary type and are very efficient even at part loads. These types of compressors are mainly used in the centralised chilled water systems upto around 350-400 TR.
Centrifugal: These are the most efficient compressors in the market and are ideally suited for very large sized compressors, generally above 500 TR. Traditional Centrifugal compressors are not suited for part loads and were used mainly to meet the base loads in large hotels, hospitals, airports etc. However, today the centrifugal compressors are coupled with variable frequency drives so that these compressors are efficient even at part loads.
• Compressors based on magneticlevitation (maglev) are now available, whereby, the performance efficiencies have increased, reduce use of oil lubricants, and also lowered frequent wear and tear due to virtually zero friction.
• Inverter based systems have also penetrated the market and provide a more uniform cooling experience to the user due to the fine control of the compressor as opposed to the frequent start stop operations in the conventional compressors.

Energy Efficiency Key Criterion
Energy efficiency is the key criterion for selection of HVAC equipment in today’s buildings. HVAC being an energy guzzler, customers are looking for energy efficient products and solutions to bring down the energy cost thereby reducing the operating cost in the buildings. Building owners are investing on green and net zero energy buildings to reduce the operating costs. Conventional HVAC systems can beretrofitted with latest energy efficient products to reduce the overall energy consumption in the buildings.

In today’s scenario buildings are complex installations systems consolidated into networked products, cloud solutions and smart data. With digitalisation, building HVAC can communicate data such as energy consumption and maintenance requirement.

Vimal Chavda from Testo India informs that Testo provides a wide range of instruments that assist you in maintaining efficient HVAC system in the building and also ensure the desired IEQ level. The testo 160 wireless LAN data logger measures, monitors and documents temperature, humidity, light intensity, UV radiation and CO2 concentration in rooms, offices and malls – automatically and without interruption – hence all indoor climate monitoring parameters are covered in one. An individually designable cover is also available for each data logger which allows the logger to blend into almost any environment.

Elaborating, Asokdas M D, Managing Director, Systemair India states, “IoT enabled products are getting smarter with inbuilt controls and cloud connectivity. This is paving ways for smart products and solutions which can be easily connected to the building management systems for monitoring and control.” Smart control enabled ancillary products are used efficiently to monitor and control the overall performance of the HVAC system. The focus of control is getting shifted to the products level wherein manufacturers are offering smart control enabled products to compliment the product performance with marginal increase in the cost. Smart products with an IoT enabled building management system will further enhance the overall HVAC and building performance. The future belongs to smart products with built in intelligence which will complement the overall building performance.

Amit Bhardwaj from Siemens informs, “The flow of data begins with networked products, sensors and actuators deliver a continuous stream of data and send it to the cloud for analytics, to turn the ‘big data’ that is being collected into ‘smart data.’ This makes it possible to identify consumption patterns and initiate corrective measures.”

He further adds that the solution should efficiently reduce energy usage in your building, react flexibly to changes in utilisation with future upgrades, and protect your investments in the long term. It needs to provide an energy management platform to consolidate data from different disciplines (HVAC, Lighting Control, security, fire safety, etc.) in a single user interface. This makes it possible to manage, control and analyse the entire building from a central location that it can be operated economically, safely and in an energy-efficient manner. Integration of all disciplines is important to provide comfortable environment and not just HVAC alone. Building Information Modeling (BIM) is now available for use in the ‘digital twin.’ This digital model is used to design the building with all its disciplines and perform ongoing simulation, testing and error correction during the design phase. The benefits of this approach include optimised energy efficiency, higher cost savings and better sustainability.

HVAC systems and products from Siemens can effectively reduce your operating costs thanks to their extremely efficient use of energy. This means you can achieve up to 30 per cent savings, while still maintaining a comfortable room climate.

It is when architects, engineers, and contractors bring knowledge of the best HVAC systems to owners and developers, collaboration serves as the cornerstone of a successful building project. The right HVAC solution focuses on energy savings and achieving long-term profitability, which saves time, trouble, and money.