Approaches to Energy Efficiency in Air conditioning: Innovative processes and thermodynamics

by

Kim Choon Ng,

King Abdullah University of Science & Technology,

Thuwal 23900-6900, Kingdom of Saudi Arabia

The global space cooling industry has been estimated to be about US$100 billion with nearly 100 million units of chillers/coolers being manufactured and sold annually. Air conditioning in buildings has transformed our human lives greatly with work efficiency in commercial buildings and improved lifestyle in all weather. However, these improvements are accompanied with the negative effects from the emissions of greenhouse gases (GHG), both directly via refrigerant emissions and indirectly through electricity generation by the burning of fossil fuels. In a recent report from the Building Technologies Office (BTO, EERE) of DoE, there is an imperative need for engineers, scientists and industry professionals to innovative cooling technologies that substantially improve the efficacy of chillers, reducing both the energy consumption and greenhouse gas (GHG) emissions in all buildings.

In this presentation, the author focuses on the electrical energy consumption for air conditioning in two economies; A hot and dry climate country, Saudi Arabia (KSA) and the other is a tropic Singapore island state with a high urban population density (> 7400 people per km2). Over the past 3 three decades both countries have similar electricity annual growth rates in excess of 6%, however, the KSA has recorded more than 50% of the annual electricity production (272TWh, 2014) is consumed for HVAC, amounting to 139 TWh per annum whilst the latter, the demand for electricity for air conditioning annually is 17 TWh, about 36% of the total electricity consumption (47TWh, 2015). Should these energy demand trends in cooling is not abated, the future energy and environmental sustainability in both developing countries may be untenable. The discussion emphasizes on the shares of district cooling systems (DCS) to overall cooling is presently 30±5% and how DCS could be exploited for future sustainability in cooling. Although there were significant improvements in the efficacy of chillers over time but since 2000, the kW/Ron of chillers for cooling for electrically driven DCS have reached an asymptotic level of 0.85±0.03 kW/Rton for the tropics and a 20% higher for the hot and dry arid climate. The levelling-off phenomenon of chillers’ energy efficiency is attributed the improvements limits on the development of compressor and refrigerant technologies. Thus, an out-of-box solution to improve energy efficiency by is urgently needed and an innovative cycle is highlighted which can be the cooling cycle with a quantum efficiency savings up to 60% can be achieved.