Sustainable and energy-efficient approaches to heating, ventilation and air conditioning (HVAC) systems within buildings are becoming increasingly critical as they comprise a substantial proportion of operational energy.
Effective HVAC design coupled with new technologies can ensure safe and comfortable working environments, as well as help improve energy efficiency and minimise a building’s carbon footprint.
Climate change is also necessitating innovative approaches to cooling systems, with a focus on energy efficiency and sustainable practices as well as HVAC systems that can adapt dynamically to fluctuating environmental conditions and higher- frequency heatwaves/cold spells.
As businesses seek energy-efficient HVAC solutions, manufacturers are keeping pace with innovative technologies, such as intelligent monitoring through highly accurate Internet- of-Things-enabled sensors and the application of automated and AI-based control systems. Sensors are now able to measure temperature and air quality with great precision, and use algorithms that continually monitor changes in air quality.
This real-time air data is fed into the AI control, which adjusts operating parameters to ensure maximum efficiency for the cooling system; importantly, it is able to detect sudden changes and respond immediately with appropriate adjustments.
Consumer preference has also shaped the direction of innovation, with growing popularity around modular and scalable systems that offer flexibility and adaptability. Modular systems are easily installed, expanded, and reconfigured, enabling businesses to adjust their cooling capacity based on changing needs.
HVAC systems often require significant upfront investment as well as costs associated with installation, such as modifications to existing infrastructure, piping, electrical connections, and automation systems.
This is on top of the costs of running the system, making it vital for companies to implement energy efficient cooling systems to minimise operational costs, particularly with a high and fluctuating price of energy.
A report by the University of New South Wales Sydney that examined the refurbishment of HVAC systems in commercial buildings noted that this presented both a challenge and an opportunity, due to the scope for substantial energy savings.
The UNSW researchers described the role of HVAC systems improving the energy efficiency of buildings could be achieved by intervening in three major areas, with each leading into the next: reducing energy requirements, upgrading or replacing HVAC systems with smarter and more efficient systems, and utilising renewable energy sources.
They said: “These three areas are linked to each other and have to be addressed holistically to achieve the best overall results. “As this project has shown, an integrated air conditioning supply accounts for between 40 and 60 per cent of the energy used in commercial buildings.
“Development in HVAC technologies has led to doubling the efficiencies of modern chillers compared to 25 years ago, the establishment of highly efficient heat pumps, and efficient heat exchangers for waste heat recovery.
“Further, sensors, controls and software tools that allow a demand-responsive hardware operation have become widespread.
“There is now a significant potential for energy savings while improving indoor air quality and thermal comfort conditions – and this applies even to buildings constructed 20 years ago.”
Evaporative cooling is the most energy-efficient HVAC method, which works through the evaporation of water and can use up to 70 per cent less energy compared to air cooling systems.
Recent innovations in these systems include corrosion- resistant heat exchangers, which limit corrosion and further reduce energy consumption, as well as the implementation of more efficient and quieter fans.
These heat exchangers use specialised alloy materials that inhibit the corrosion of cooling fluid and provide protection against mechanical damage, extending the system’s lifespan and minimising maintenance costs.
Advances in heat transfer solutions for cooling applications have also helped create more efficient systems, with examples being the development of higher-efficiency materials for heat exchangers as well as the use of thermoelectric heat pumps.
These pumps transfer heat between different locations, helping reduce energy consumption, and are environmentally friendly and cost effective due to operating without any additional power generation.
Furthermore, new cooling fans that use DC motors have been developed, which use less energy and make less noise than conventional AC motors.
Along with being cheaper to run, evaporative cooling systems are also cheaper to build overall and can create humidity, which is beneficial for dry environments.
However, evaporative cooling requires a constant supply of water, is less efficient in areas with high humidity, and requires air circulation.
Air cooling systems, which work by cooling the air directly and dissipating heat externally, are the least energy and cost efficient, but do not need air circulation, are flexible in their application, and dehumidify the cooled area instead.
Water tower cooling systems, on the other hand, draw cold water from a nearby water source and use it to cool down the air.
This makes them more environmentally friendly than traditional cooling systems, as they reduce waste water and carbon dioxide emissions, allowing operators to reduce their overall footprint.
In a 2022 study of sustainability in HVAC systems, School of Built Environment UNSW Sydney researchers noted that the use of various heating and cooling technologies that utilised renewable energy source in HVAC systems were very important options in improving sustainability.
They said: “Recent pandemic diseases and the fact that people spend more than 80 per cent of their time inside buildings show the importance of designing sustainable HVAC systems.
“Moreover, HVAC systems are the respiratory system of a building, and the potential risk to develop various microbial contaminations that threaten occupant health and work performance shows the urgency to improve its sustainability and performance.
“Meanwhile, the high percentage of existing unsustainable HVAC systems globally shows the vital need for their retrofitting to mitigate environmental, energy, and economical issues.”
Renewable technologies used by HVAC systems in buildings include desiccant heating, cooling, and ventilation; evaporativ passive cooling; solar heating and cooling; geothermal heating and cooling; and biomass heating and cooling systems.
Other energy-saving technologies have also been developed, such as phase change materials, night-time radiative cooling, evaporative cooling, and desiccant dehumidification.
The various components within HVAC systems have also been modified with improved designs to reduce energy
consumption and optimise performance, such as dampers, filters, humidifier/dehumidifiers, heating and cooling coils, and ducts and fans.
The researchers also pointed out that waste heat and energy recovery were central for reducing HVAC energy usage, with air-to-air heat exchangers and heat pipe heat exchangers (HPHE) with different forms and designs being used as heat recovery equipment.
A separate study conducted in 2019 showed that the use of a U-shaped HPHE in a hospital could reach 7.64 per cent higher effectiveness, or heat recovery of up to 608.45 watts.
Innovations to improve heat recovery and overall sustainability include liquid-to-air membrane energy exchangers, porous metal foam heat exchangers, nanofluid as heat transfer fluid, phase change material as heat transfer media, membrane heat exchanger, and polymer heat exchangers.
