By Turyasingura Medard
Turyasingura Medard is an HVAC Project Engineer at Thermal Solutions Limited. He is currently pursuing a Master’s in Mechanical Engineering at Makerere University. He graduated with a Bachelor of Engineering in Mechanical and Manufacturing Engineering from Kyambogo University in 2019.
A comfortable indoor environment starts with maintaining appropriate thermal comfort and indoor air quality. HVAC (Heating, Ventilation, and Air Conditioning) systems are responsible for this function. HVAC systems consume 50-60% of global energy, necessitating long-term solutions. The researcher goes over some of the approaches that can be used to achieve long-term energy sustainability in buildings. The primary goal is to adapt energy-saving technology, and provide energy-saving solutions that combine HAVC equipment and its peripherals while preserving a building’s required comfort levels.
Climate change, population increase, and changing lifestyles are all factors that contribute to the need for heating, ventilation, and air conditioning (HVAC) systems in various types of buildings. HVAC systems play a significant role in the comfort and safety of indoor air quality. The demand for improved thermal comfort and indoor air quality in buildings (both commercial and residential) has become essential. Uganda’s demand for HVAC systems is increasing at such a rapid rate that energy consumption will soar greatly in the next few decades. This raises an obvious question: How do we maintain the required thermal comfort and healthier indoor air-quality levels of buildings in a sustainable way? If this question is not answered satisfactorily, the expenses of HVAC systems will certainly outweigh the advantages.
Understanding and considering various parameters related to the sustainability of new and existing HVAC systems in buildings is vital to providing healthy, energy-efficient, and economical options for various building types. Research studies have indicated that HVAC systems account for 50–60% of the energy used in buildings (Rawat & Singh, 2021). This is due to a lack of energy-efficient designs, the usage of ineffective cooling systems, and maintenance, particularly in hot and dry climates. As per Uganda Vision 2040, hotel, construction, and real estate, among others are the key tertiary industries that are expected to expand; so will energy usage. Furthermore, the Uganda Vision 2040 expects access to the national grid to significantly increase to at least 80 per cent countrywide (NPA, 2013). The growth of the above-mentioned sectors will certainly increase the usage and penetration of air conditioning in Uganda. Better technology investment and careful design are the keys to the long-term economic, environmental, and social development of HVAC systems in Uganda. This can be accomplished through the provision of energy-saving technologies and solutions that combine HAVC equipment, their peripherals, and the buildings in which they operate.
2.0 ENERGY CERTIFIED HVAC SYSTEMS
The HVAC industry is attempting to produce environmentally friendly technology across the world. There are now Energy Star Certified HVAC units with significantly greater Seasonal Energy Efficiency Ratio (SEER) ratings on the market. The SEER rating divides the amount of electrical energy input by the amount of output to determine the efficiency of an air conditioning system. The SEER rating indicates how energy efficient your system is. Energy Star-qualified units have been independently certified to save energy while maintaining system operation and features. EER (Energy Efficiency Ratio) rating is another metric that most energy-efficient residential HVAC systems will have. EER is the ratio of an air conditioner’s rated cooling or heating capacity to its power consumption under standard ambient conditions, which are a 95°F outdoor temperature, an 80°F indoor temperature, and a 50% relative humidity. The system’s output in Btu/h per watt of electrical energy is precisely what is meant by EER. In contrast to SEER, EER rating tests under rigorous laboratory conditions rather than calculating its ratios using seasonal averages. The higher the EER number, similar to the SEER rating, the more energy-efficient the HVAC system is.
2.1 Programmable thermostats and smart air conditioner controllers
Smart controllers and programmable thermostats are two of the numerous technologies in the HVAC industry that are used to provide intelligent features to central cooling systems, ducted and ductless air conditioners that not only provide convenience to the user but also help save energy. Furthermore, smart controllers and thermostats enable remote operation of HVAC equipment via a computer, tablet, or smart phone. They also include plenty of other features that can help you save energy. Intelligent triggers like the Comfy Mode and weekly scheduling are just a few examples.
2.2 HVAC Design with the greatest efficiency in mind
In this context, efficiency refers to both the design and operation of HVAC equipment. When designing these systems, designers should use a comprehensive approach with the goal of reducing energy consumption. This can be accomplished by looking at how each component of the HVAC system utilizes energy and finding ways to enhance it. Today’s products include ductless mini-split air conditioners with inverter-driven variable-speed compressors and fans, variable frequency drives for ventilation fans, and commercial rooftop systems with micro-channel heat exchangers and advanced controls for economizers. Demand-controlled ventilation is also essential for lowering the cooling load and ensuring that buildings are not cooled regardless of the needs of their occupants. When possible, designers should use renewable energy sources. For optimal effectiveness, HVAC system designers should take advantage of natural conditions or by-products. For example, the system could be designed to pre-cool air using a cool exhaust (Bonacorda, 2022).
2.3 HVAC Equipment Utilisation
Assuming that the HVAC equipment is designed for maximum efficiency, the installation, maintenance, and use of the system have the biggest impact on its efficacy. To ensure that the greatest quantity of air is required to reach all specified sections of the building, every HVAC system equipment must be skillfully installed. The equipment should be maintained and repaired on a regular basis once it has been installed; this includes ventilation fans, air handling systems, and air conditioners, as well as auxiliary equipment like ductwork, which can waste a lot of energy.
2.4 Building Design for High Performance
While increasing HVAC systems’ efficiency reduces the amount of energy used to meet the building’s cooling loads, high-performance building designs can reduce the overall load. For example, utilisation of international performance standards such as ASHRAE 90.1 for commercial buildings, and the International Energy Conservation Code (IECC) for residential buildings can significantly reduce cooling demand and subsequent energy consumption (Goetzler et al., 2016). Standards provide for reducing cooling loads by reducing heat and improving the building envelope, which includes walls, floors, roofs, and fenestrations (i.e., windows and doors). The requirement for an air conditioning system is reduced by reducing heat transfer into the building envelope via conduction, radiation, filtration and infiltration. Several building energy efficiency studies conducted in hot, humid climates found potential annual cooling load reductions of up to 38% from improved insulation alone, and up to 12% reductions from external shading (Al-tamimi, 2010). In pilot projects, dynamic solar glazing reduced cooling loads by up to 20% (Goetzler et al., 2016). Increasing the efficiency of lighting and other appliances that give off heat has the compound benefit of reducing cooling demand as well as direct energy consumption (Litiu & Assistant, 2014). The roof structure is a critical part of any building and is always directly exposed to sunlight. Heat gained through the roof is the highest on a sunny day in low-rise buildings. Modifying roofing surfaces to increase their radiant energy reflectivity in the solar spectrum and high emissivity in the earth’s atmospheric transparent window (Mandal et al., 2019). This can reduce the cooling load and save energy.
The engineering community can help to accelerate the adoption of sustainable HVAC systems. The development of a cohesive set of solutions that are interdisciplinary and collaborative with all building functions will be necessary to achieve this sustainable future of HVAC. Embracing efficient HVAC technologies and standards throughout the design stage, as well as using efficient building codes, can help to encourage best-practices for long-term and cost-effective HVAC systems. For enhanced HVAC equipment reliability and sustainability, users must also be proactive and implement effective preventive actions.
Al-tamimi, N. A. M. (2010). Evaluation on Cooling Energy Load with varied Envelope Design for High-Rise Residential Buildings in Malaysia.
Bonacorda, P. (2022). HVAC Efficiency. https://www.ase.org/blog/hvac-efficiency-what-it-why-it-matters-and-how-get-started
Goetzler, W., Young, J., Fuhrman, J., & Abdelaziz, O. (2016). The Future of Air Conditioning for Buildings (Issue July).
Litiu, A., & Assistant, P. (2014). IEA Technology Roadmap for energy efficient building envelopes. December 2013, 33–36.
National Planing Authority (NPA). (2013). Uganda Vision 2040 |. http://www.npa.go.ug
Rawat, M., & Singh, R. N. (2021). A study on the comparative review of cool roof thermal performance in various regions. Energy and Built Environment, October 2020. https://doi.org/10.1016/j.enbenv.2021.03.001