Improving Energy Efficiency and Indoor Air Quality with Smart Air-Conditioning

Inefficient air-conditioning systems in public buildings. Air-conditioning in many developing member countries (DMCs) accounts for up to 50% of energy consumption in public buildings. Advanced air-conditioning systems with energy-saving technology, combined with demand-side management, can achieve energy savings of 25%–45%. Low energy efficiency is mainly due to the use of old equipment and a lack of proper operation and maintenance. 

Transmission of airborne diseases. The risk of transmission of airborne diseases through air-conditioning systems in public buildings became a major concern during the COVID-19 pandemic. Studies show the virus can survive in the air for several hours in aerosols, with droplet transmission prompted by air-conditioned ventilation. Moreover, air-conditioning systems typically use recirculated air (70%) mixed with fresh air (30%) in public buildings. Standard air filtration components are not effective in filtering viruses and pathogens, creating a high risk of spreading COVID-19 and other airborne diseases. In many DMCs, this risk is higher due to poor hygiene practices, old equipment, lack of adequate operation and maintenance, and overcrowding. 

Additionally, air-conditioning systems rely heavily on hydrofluorocarbons, a greenhouse gas potentially thousands of times more potent than carbon dioxide, for cooling. Proper management of hydrofluorocarbons through restriction and prohibition; development of climate-friendly substitutes; and harmless treatment is critical to addressing greenhouse gas emissions from air-conditioning systems.

Government institutions and public building operators often lack the awareness and capacity to address these risks. 

Optimize energy efficiency. This requires thorough knowledge of the building’s architecture and climate considerations suited to the local context. Consulting professionals and considering local regulations and incentives can aid in making informed decisions. The most effective approach considers the climate, building design, and specific cooling needs.

To optimize energy efficiency:

• Select, design, and size air-conditioning system components appropriately for the building and climate zone.
• Implement variable speed components, like pumps and compressors, that adjust cooling delivery based on demand, operating at lower speeds when demand is lower, resulting in better energy efficiency and precise temperature control.
• Introduce zoned cooling within the building, using independent thermostats for precise control and preventing overcooling of unused spaces.
• Choose high-efficiency systems that provide the same cooling output, measured by energy efficiency ratio, seasonal energy efficiency ratio, and coefficient of performance.
• Adopt energy recovery systems that maintain good indoor air quality by exchanging heat and moisture between incoming and outgoing air, ensuring fresh air while retaining temperature and humidity levels.

Improve indoor air quality and disease resilience. This requires a multidisciplinary approach involving engineers, architects, building owners, and health experts. This involves proper design, building practices, ventilation strategies, and ongoing maintenance to prioritize the health and well-being of occupants, especially during disease outbreaks.

To maintain indoor air quality and prevent transmission of airborne diseases:

• Minimize or eliminate indoor pollutants, such as tobacco smoke, volatile organic compounds from cleaning products and furnishings, and emissions from building materials.
• Adopt high-efficiency air filtration systems to capture particles like dust, pollen, and allergens, with regular filter maintenance.
• Ensure proper ventilation to bring in fresh outdoor air and remove indoor pollutants. Mechanical ventilation systems can help maintain adequate air exchange rates.
• Ensure sufficient clean outdoor air supply and minimize air recirculation to limit disease transmission.
• Maintain appropriate indoor humidity levels (30%–60%) to prevent mold growth and dust mites, contributing to occupant comfort and preventing respiratory issues.
• Maintain air-conditioning systems, including cleaning ducts and changing filters. Regular inspections are necessary to address issues affecting air quality and energy use.

Use climate-friendly refrigerants. Opting for refrigerants that minimize greenhouse gas emissions and ozone depletion will not only mitigate climate change but also ensure a healthier, more sustainable future. 

• Improve the design of cooling systems to minimize the use of refrigerants. 
• Use eco-friendly refrigerants with lower environmental impacts, zero ozone depletion potential, and very low global warming potential, compared to traditional options like chlorofluorocarbons and hydrochlorofluorocarbons.  
• Reduce leaks in air-conditioning systems. 
• Recover, recycle, reclaim, and properly dispose of refrigerants to minimize environmental impact.

Leverage advanced digital technology. Smart air-conditioning systems use advanced technologies and connectivity to enhance efficiency, comfort, and control of indoor climate management. These systems utilize sensors, automation, and remote-control capabilities for precise and user-friendly cooling solutions.

• Adopt programmable thermostats that optimize energy usage based on occupancy patterns.
• Install air quality monitoring systems to track pollutant levels.
• Use building automation and sensors to make air-conditioning systems adaptive to various conditions.

Indoor air quality sensor (left); live display of building indoor air quality and energy data (right). Photo credit: ADB.

ADB collaborated with the Sri Lanka Ministry of Power and Energy and Sri Lanka Sustainable Energy Authority to deploy smart air-conditioning in three public buildings in Colombo. This effort is projected to deliver a 30%–40% reduction in energy consumption with a return on investment within five years.

Sri Lanka Postal Headquarters. For the past five years, the building had no properly functioning air-conditioning, causing significant discomfort, especially during summer. The new system included a high ventilation flow rate filtration system to maintain indoor air quality and thermal comfort, even in the building's open double-height space. The system adjusts the quantity of clean outdoor air based on occupancy levels, maintaining indoor air quality with minimal energy use. Large, high-volume, low-speed fans enhance air circulation and alleviate discomfort during peak occupancy. Occupants reported substantial improvements in thermal comfort, marking a positive shift in their experience.

Sri Lanka Standards Institution. The top floor, experiencing high heat levels, was chosen to pilot the smart air-conditioning. Previously, the space relied solely on wall-mounted recirculation units without ventilation, causing discomfort from direct cold air drafts. The new system combined a dedicated outdoor air system with a recirculated air-conditioning system, featuring a filtration system and a heat recovery wheel to reclaim heat from exhaust air. High-efficiency ceiling fans improved air circulation and mitigated discomfort during hot summers. Occupants reported significant enhancements in thermal comfort, and facility managers found the real-time dashboards helped reduce energy consumption.

Sri Lanka State Pharmaceuticals Manufacturing Corporation. The laboratory area, where many chemical experiments take place, was chosen due to poor air quality concerns, particularly from volatile organic compounds. Previously relying on ceiling-mounted exhaust fans, the new system introduced appropriate filtration and ventilation in the laboratory spaces. Individual air delivery systems were implemented to adjust air quantity based on the diverse nature of chemical experiments. Portable filtration systems with chemical filtration capabilities were provided to absorb different types of gases. Occupants reported significant improvements in indoor air quality, and facility managers found the monitoring tools effective in tracking temperature and humidity levels, supporting the laboratory's efforts toward international certification.

Asian Development Bank (ADB). Regional Support to Build Disease Resilient and Energy Efficient Centralized Air-conditioning Systems.

ADB Knowledge Events. Strengthening Disease Resilience and Indoor Air Quality in Buildings.

Disease-Resilient and Energy-Efficient Smart Centralized Air-Conditioning Systems.

How to Build a Smart and Efficient Air-Conditioning System. 

Piloting Disease-Resilient and Energy-Efficient Smart Air-Conditioning Systems in Public Buildings.