The unspoken energy guzzler
Cooling systems consume about 40-50 per cent of a building’s energy, contributing to the urban heat island effect
By Kavickumar Muruganathan
Situated near the Equator, Singapore is hot and humid throughout the year, making it necessary for Singaporeans to have an air conditioning (AC) system. Singapore has more air conditioner installations than any of its ASEAN neighbours. The number of aircon installations is expected to rise with the increase in residential and commercial building developments, growing by 73 per cent from 2010 to 2030.
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 4 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 built-up 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 air-conditioning (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% of its theoretical maximum efficiency, with the majority in the 6-8% 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 cross-sector 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.
- Kavickumar Muruganathan is a sustainability and supply chain professional in the renewable energy sector. He is also a lecturer at TUM Asia.