Thermal Control 17 July 2021
With progressive economy, new building technologies began to transform the urban landscape. The advent of air conditioning, low-wattage fluorescent lighting, structural steel, and reflective glass made possible enclosed glass-and-steel structures that could be heated and cooled with massive heating, ventilating, and air conditioning (HVAC) systems, thanks to the availability of cheap fossil fuels. The economic boom accelerated the pace of this phenomenon, to the point where the international style ‘glass box’ became the design icon of cities and rapidly growing suburbs. However, a small group of forward-thinking architects, environmentalists, and ecologists, began to question the advisability of building in this manner, said Rahul Aeron, Assistant Vice President, Sales, DRI – Pahwa Group.
Global warming and the growing awareness of the same led to the nascent ”environmental movement” capturing the attention of the public at large. As fossil fuel prices spiked upward and lines at fuel stations stretched for blocks, everyone started to wonder about the wisdom of relying so heavily on fossil fuels for transportation and buildings.
Besides the media buzz about building eco-friendly, today builders are becoming more educated on long-term cost reductions created by more efficient energy usage and the reduction or even outright elimination of toxins in building materials. ”Up until recently, however, building green usually meant building at a higher cost. But even those premiums are beginning to drop. The US Green building Council (USGBC) then came up with the concept of LEED rating system to establish a method to identify and quantify the green content of the building”, Aeron adds.
Green building could be defined as the practice of:
- Increasing the efficiency with which buildings and their sites use energy, water, and materials, and
- Reducing building impacts on human health by providing better indoor environment (IEQ).
According to Aeron, ”Green Building movement has been driving the HVAC community for now about a decade to look at innovative solutions for reducing the energy cost and better IEQ (Indoor Environment Quality). The ventilation and air conditioning system which is a key component in green building design is on the verge of a paradigm shift. This shift is providing designers opportunities to explore energy efficient designs. The new initiatives are aimed at improving health, comfort and productivity.”
HVAC systems play vital role in green buildings since many of the green building factors are affected by the performance of the HVAC systems. Talking about the role of HVAC systems in a green building, Neeraj Gupta, Senior General Manager – Living Environment Division, Mitsubishi Electric India said, ”HVAC system for green building shall be planned to reduce energy consumption while maintaining the indoor conditions at a comfortable level to keep occupant’s health and productivity. HVAC system created should not only meet the standard on energy front but beat the standard codes like Energy Conservation Building Codes (ECBC), India and other relevant standards to achieve efficient and higher level of green building rating.”
HVAC systems account for nearly 40 to 50 per cent of the energy used in commercial buildings in India, observed Sanjay Sudhakaran, Vice President – Digital Energy, Greater India Zone at Schneider Electric. Hence, in his opinion, HVAC systems have greater influence in transforming the building to green by achieving better energy efficiency, sustainability and reducing the operating cost. He said, ”The design of the HVAC system for a green building should reduce energy consumption while maintaining the indoor conditions at a comfortable level to keep occupant’s health and productivity. A comprehensive building management system, that will ensure the overall efficiency by intelligently managing the aspects of HVAC, lighting, safety and security, plays key role in making green buildings.”
Daniel Chen, HVAC APAC Marketing Manager, CAREL also observes that HVAC systems play a very important role in a green building to reduce energy consumption, deliver a comfortable and healthy work environment. He said, ”HVAC systems account for nearly 50 to 60 per cent of the energy used in green buildings in India. Consequently, any green building has the potential to realise significant savings by improving its control and efficiency of HVAC operations.”
Therefore, a shift to more energy efficient and sustainable HVAC systems will ensure that buildings can be classified as green, opines Gaurav Mathur, Business Development (Building Services), Grundfos India. ”These green buildings will be able to integrate intelligent HVAC systems to increase the overall energy savings without compromising on the performance. In the long run, an efficient HVAC system will be instrumental in ensuring that the green building continues to meet and surpass regulatory parameters associated with sustainability,” he adds.
Any commercial building has the potential to realise significant savings by improving its control of HVAC operations and improving the efficiency of the system it uses. ”An integrated and comprehensive design process beginning at a project’s planning stage is required to optimise the HVAC design and HVAC commissioning and operation for green buildings,” said Gupta.
Advanced HVAC solution trends for green buildings
According to Daniel Chen from CAREL, ”The most advanced HVAC solution trend is to deliver energy savings while providing customised comfort and health. Having a high-performance HVAC system is extremely important to the green building designer. A health and comfortable working environment has a very positive impact on productivity.”
According to Aeron from DRI – Pahwa Group, the advanced HVAC solution trends for green buildings will include:
- Using hybrid systems specially for adaptive comforts
- Using renewable sources such as Solar and geothermal systems
- Using desiccant enhanced systems.
He further adds, ”An interesting solution which is gaining a lot of interests is integration of DOAS (Dedicated Outdoor Air System) or Treated Fresh Air Units (TFAs) with parallel terminal system that offers a migratory path from the single all-air variable air volume systems.”
For example, active chilled beams combined with system design suitable for tropical climate, the DOAS becomes an excellent choice to address IAQ (indoor air quality), humidity control and help buildings become green.
The dedicated OA concept, the new OA paradigm!
DOAS in their various configurations are ideal especially in the tropical perspective, as DOAS options provide both supply air at low dew point and with minimal energy usage. The basic concept is to deliver conditioned Outdoor Air (OA) to every space and occupant of the building. Use the OA to remove the entire space latent load (primarily from occupants who receive a prescribed flow rate of OA). By decoupling the latent and sensible space loads, great flexibility in meeting the parallel sensible loads is realised.
The DOAS approach calls for dividing the load into the two components i.e. sensible and latent. This approach is often or commonly referred to as the ”Divide and Conquer”. The entire latent load brought by outside air is removed at the source & also air is supplied at a low dew point to take care of internal latent load. The parallel internal cooling devices are then limited to take care of sensible cooling load.
This is perfectly suited for spaces with high latent loads viz. areas having high occupancy like hotels, malls, BPO, IT offices, hospitals etc.
”With the green building movement strongly acquiring its foothold globally, it will be very important and critical for designers to come up with innovative solutions. The requirement today is for a single integrated intelligent, single responsibility, unitised DOAS to effectively provide the best green, fresh air system solution,”said Aeron.
Adding intelligence to HVAC solutions
Industry 4.0 technologies are being introduced to traditional HVAC solutions to augment its existing utility. Intelligent pumping solutions with smart sensors can be used to collect data such as indoor and outdoor temperature to provide actionable insights, said Mathur from Grundfos India. ”These insights can even help the HVAC system to identify temperature changes on a real time basis and make the necessary adjustments. This will ensure that energy is consumed optimally on a demand basis and that there is no waste of resources.”
The sensors can also provide information associated with potential downtime through its predictive maintenance capabilities to mitigate unexpected maintenance costs and improve the overall lifecycle of the HVAC system.
Neeraj Gupta from Mitsubishi Electric India illustrates some of the trends in HVAC design from thermal comfort strategies to decoupling ventilation from heating and cooling and indirect evaporative cooling. They are:
- Occupant-based thermal comfort strategies: Systems like radiant cooling help to reduce energy use and improve thermal comfort. Thermal comfort can be directly addressed through other systems such as using low-energy systems to provide localised heating and cooling or by controlling the HVAC system through occupant polling.
- Decoupling of ventilation and heating/cooling: With a DOAS system, the heating and cooling requirements for space are met through a hydronic system. Since water has a much higher capacity for energy transfer than air, the amount of energy required to deliver the heating and cooling is greatly reduced, while pump energy is somewhat increased. A side benefit of the reduced air quantity is smaller ductwork, which decreases the cost of the ventilation system and, potentially, the building’s required floor-to-floor height. DOAS systems are typically paired with passive chilled beams, radiant heating and cooling, or fan coils.
- Indirect evaporative cooling: When it comes to green buildings, owners and architects are striving to meet HVAC loads with optimum comfort and minimal energy. Indirect Evaporative Cooling (IEC) offers a highly efficient way to cool an indoor space without raising the humidity. This system works well when combined with radiant technology for heating and cooling and DOAS for ventilation.
Individual HVAC controls
‘Green Building’ is continually evolving concept and the industry is re-inventing buildings to be more engaging, hyper-efficient, truly sustainable and above all simple. Occupants demand more and more control over their work space driven by a ”there’s an app for that!”mantra, office environment and comfort is more important than paycheck for a majority of millennials. ”HVAC design should embrace the standard codes like ASHRAE and ECBC while meeting the modern trends of smart and autonomous buildings. IP enabled products are gaining more traction for easy integration of devices between other building syste” Sudhakaran from Schneider Electric said.
Based on a research, about 75 percent of a building’slife cycle costs are in maintenance and operations, and upto 45 percent of the energy used by HVAC systems is wasted due to faults. By being proactive versus reactive about maintenance using analytics and deep insights, we can significantly increase building’s overall efficiency. Hence, in Sudhakaran’s opinion, the latest trend is of advisory services that combine smart tools including analytics, reports, remote troubleshooting, alarm monitoring, and service bureaus manned with building controls.
HVAC systems are cornerstone of green buildings and new technologies brings new possibilities while at the same time users are demanding more to unlock untapped building value. Advances in mobile, Cloud-based and IoT technologies are creating enormous opportunities for information gathering, sharing, and analytics impacting the way buildings are run.
