Evaporative Cooling: The Status Quo

Introduction | Status Quo | Alternatives | Requirements | Load Minimisation | Conclusions | Bibliography

Bureau of Meteorology climate data for Alice Springs indicates that the town has an annual cooling season of approximately six months (October to March), or 185 days (see Alice Springs Climate Data). The Arid Lands Environment Centre rated the annual evaporative cooler operating hours for a typical Alice Springs household at 2400 hours (ALEC 2007). This figure divided by 185 days produces an average figure of approximately 13 operating hours daily. This figure also concurs with the author's personal experience of average evaporative cooler use in Alice Springs during the hotter months.

Data published by a range of manufacturers indicates that the maximum power rating of residential evaporative coolers is in the range of 500W to 1500W, delivering a cooling capacity in the range of 8kW to 16kW. Most coolers have at least three speed settings, however, so that under normal operating conditions power consumption is often considerably lower, in the range of 350W. This figure is consistent with data published by the Centre for Sustainable Arid Towns (CSAT 2004) which estimated the average hourly running cost of evaporative cooler in Alice Springs to be $0.05 ($0.05 / $0.1438 per kW = 0.348kW).

ALEC rated the average hourly water consumption of a typical evaporative air-conditioner in Alice Springs at 29 L/hr (23 L/hr evaporated, 6 L/hr bleed-off) (ALEC 2007). Multiplying this rate by the average daily and annual operating hours produces average daily and annual water consumption figures of 377L and 69.6 kL respectively. Average cooling capacity can then be estimated by multiplying the average hourly water evaporation rate (23 L/hr = 23kg/hr) by the latent heat of vapourisation of water (2257 kJ/kg), with the product then being multiplied by the efficiency factor of 0.75 suggested by Parlour (1998), to produce a final average cooling capacity of 10.8kW per hour.

The following table summarises estimates of the status quo in relation to the resource consumption and cooling capacity of the average Alice Springs residential evaporative cooler, on the basis of available data:

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