@ green | July-August , 2021

Cooling systems consume about 40-50 per cent of a building ’ s energy , contributing to the urban heat island effect

BY KAVICKUMAR MURUGANATHAN

A residential building with many air-conditioners is dwarfed by the Singapore ’ s modern high-rise blocks

The buildings and household sectors constitute 19 per cent of Singapore ’ s carbon emissions , making it the second-highest source of emissions in Singapore after the industrial sector . Of the 19 per cent , a sizeable portion is said to be generated from air conditioning . Air-conditioning accounts for up to 40 per cent of the electricity bill for an average Singaporean household .

Huge Carbon Footprint of Air-conditioning

A standard 2kW AC unit can comfortably cool a room of 200 square feet area . It produces about 1.4 tonnes of carbon emissions per annum assuming it is turned on 20 days a month on average .

If there are 4 such AC units in an HDB household , they will generate about 5.6 tonnes of carbon emissions annually . In comparison , a 35-inch flatscreen plasma television generates 0.25 tonnes of carbon emissions yearly , assuming it is switched on for about six hours a day .

The carbon footprint of using a washing machine is much lower at 0.051 tonnes of carbon emissions , assuming about 180 washes are done yearly .

The carbon emissions arising from AC use in a typical HDB household clearly outstrip emissions from other household appliances . In fact , annual missions generated from AC use in an HDB flat with four AC units are more significant than yearly emissions generated from driving a passenger car . To offset and sequester these emissions , about 22 trees need to be planted annually .

The carbon emissions from Singapore ’ s residential units pale in comparison to those arising from commercial buildings . Cooling systems consume about 40-50 per cent of a building ’ s energy , contributing to the urban heat island effect . The air is builtup areas in the Central Business District ( CDBs ), where AC systems run non-stop is about 7 degrees Celsius hotter than in greener pastures .

Singapore ’ s business , as usual , approach to cooling is expected to contribute about 4.89 megatonnes of carbon emissions by 2030 . Among buildings , computer data centres are energy guzzlers , as they have a higher cooling demand . With plans for Google to open its 3rd data centre and

Facebook to locate its 11-storey data centre here soon , Singapore ’ s cooling demand will increase .

Reducing Dependency on Air-conditioning

A survey in 2017 highlighted 68 per cent of respondents from Singapore encountering excessive cooling of public places such as offices , shopping malls and cinemas . This begs the question as to why building owners maintain indoor air-con temperatures at artic-cold levels . Aircon settings in a building should be dependent on the outside temperature and humidity . Yet , they remain unchanged during the event of heavy rainfall or cooler weather . Commercial buildings are kept about 40 per cent cooler than they should because building owners tend to plan for the hottest days and don ’ t power the air-con down during cooler days .

If Singapore is to realise its climate pledge of reducing emissions intensity by 36 per cent from 2005 levels by 2030 and stabilising emissions to peak around 2030 . In that case , it has to wean off its addiction to air-con . This can be achieved by adopting passive building designs , more efficient technologies and supporting a culture change in cooling consumption .

For a start , commercial buildings can turn down their air-conditioning when the temperatures drop as technologies to adjust temperatures are already available . Most building operators in Singapore directly manage their own cooling systems . Still , they do not prioritise fine-tuning the settings for maximum efficiency , even though it results in obvious energy and cost savings . Regulatory and social pressure can drive developers and shopping mall operators to adjust commercial buildings ’ cooling settings . Building operators must be made to disclose their respective cooling energy loads publicly .

Singaporeans have a part to play at home as well . They need to tweak their AC usage to reduce carbon emissions . A responsive temperature setting is required . This means that an AC unit should work according to both indoor and outdoor temperatures . The latest AC units can auto-adjust , but older models need to have temperatures manually adjusted according to surrounding temperatures .

Passive Design & Better Technology

The most cost-effective way for Singapore to meet its energy targets is to design buildings that don ’ t need to be cooled much in the first place . This requires a mindset shift among building owners and occupants . While architects are ready to offer passive design solutions , there must be strong acceptance and demand for such designs from occupants . Passive design helps buildings keep cool without air-conditioning .

Passive cooling systems include industrial fans , blinds , natural ventilation & airflow systems , chilled beams , shading and cool roofs . Integrative building design , which involves designing energy-using systems not as isolated components but also makes building efficiency improvements economically viable by eliminating or reducing heating , ventilation , and airconditioning ( HVAC ) equipment .

According to data from the United Nations ’ United for Efficiency project , if Singapore switched to the best available cooling technology , it could cut energy consumption by 30 per cent by 2030 . The resulting emissions reduction would be equivalent to taking 233,400 cars off the road . Installing more efficient cooling systems is crucial .

Traditional air-con units can be replaced by chillers that use water instead of harmful refrigerants and consume lesser electricity . The use of membranes and district cooling systems which save energy by pumping chilled water from a centralised plant to multiple buildings can be implemented and scaled up . Replacing data centre air chillers with liquid cooling systems is a more efficient way to prevent data centres from overheating .

The compressor technology in AC units has barely reached 14 per cent of its theoretical maximum efficiency , with the majority in the 6-8 per cent range . The AC industry , dominated by a handful of large manufacturers , is simply responding to current regulatory and market signals at present . Consumers still tend to focus on price , brand and aesthesis . Consequently , the manufacturers focus more on advertising and aesthetics than research and development on best-in-class compressor technology . This has to change .

Robust Regulatory Framework in Place

Singapore has a solid legislative approach for standards in air-condition manufacturing and ensuring public awareness of cost and energy savings to be enjoyed from energy-efficient models . The Mandatory Energy Labelling Scheme ( MELS ) encourages consumers to purchase more energy-efficient household air-cons . Under this scheme , five-tick air cons are the most efficient . The National Environment Agency ( NEA ) has also introduced the Minimum Energy Performance Standards ( MEPS ) to phase out less efficient appliances from the market .

The Building and Construction Authority ’ s ( BCA ) Green Mark Scheme has components within its certification criteria when it comes to the built environment . It requires building owners and developers to achieve higher energy efficiency by reducing a building ’ s cooling demand and adopting more efficient cooling systems . To cap it off , the implementation of a carbon tax pushes developers towards low-energy buildings . But more needs to be done to foster more significant crosssector research and collaboration between industry and academia into cutting-edge cooling technologies given its existential need for Singapore .

Everyone Has a Part to Play

We are already feeling the effects of climate change . We are experiencing higher temperatures and greater humidity like never before . It is crucial that Singapore slowly weans off its air condition addiction to prevent further exacerbation in rising global temperatures . Till the day we can use alternative forms of energy on a broader scale , turning on the air conditioner will always affect our environment . On our part , the only way to limit the damage is to use high energy-efficient air conditioners and to keep their use to a minimum level possible . — @ green

Kavickumar Muruganathan is a sustainability and supply chain professional in the renewable energy sector . He is also a lecturer at TUM Asia .