Smart watering drops temps to cool costs

An innovative world-first trial conducted by SA Water and Adelaide Airport has found the smart use of water to maintain soil moisture and cultivate green space, can reduce average ambient temperatures by 3ºC on warm days and potentially lower heat-influenced costs like air conditioning, and aircraft take-off.

The study is in its third year and focusses on sustainable outcomes, with recycled water irrigating four hectares of Lucerne 600 metres south of the airport’s runway, to also demonstrate the space can produce revenue-generating food crops.

Between 12 and 15 millimetres of water is applied to the area up to three evenings a week, with more than 40 temperature and humidity sensors monitoring conditions in the irrigation area, and the persistence of cool air outside of the test zone.

In a preview of his presentation to the Ozwater’18 conference in Brisbane, the concept’s creator, SA Water’s Manager of Environmental Opportunities Greg Ingleton, said the promising findings could help improve the liveability of cities around the world – especially hot and dry places like Australia.

"By supporting green infrastructure and the intelligent use of water, we can cool urban areas and reduce the impact of heatwaves and climate change," Greg said.

"The extensive hard surfaces and cleared land around airports means they can often become heatsinks, which has impacts on both terminal and airside operations that need to be managed.

"Jet engines work better in cooler, denser air, using less fuel during take-off and being better able to carry their optimal passenger and cargo loads."

In warmer, less dense air, planes must travel faster down the runway to produce the lift needed for take-off. When a runway lacks the distance required to reach these speeds, a plane’s weight must be lowered by removing passengers, luggage and cargo; reducing profit, or payload, for the airline.

There is also a threshold temperature above which some smaller domestic aircraft like the Airbus A330 and Boeing 737 simply cannot take-off.

"Last year in Arizona in the United States, 50 flights were cancelled in one day due to it being too hot for the planes to take off," Greg said.

"We can reduce the risk of this happening at many airports in Australia and around the world, by employing irrigation to green buffer land around the runways."

Greg said a relatively small amount of water could replicate the cooling effect at a domestic level.

"Cooling occurs due to the evaporation of moisture from the soil profile, along with the transpiration of moist air from the vegetation.

"Watering around a window – or even the area around an air conditioning unit – can reduce the temperature of the air flowing into the house, which is the same principle as evaporative air conditioners.

"We can further incorporate the effect into house and garden design by positioning windows on the south side of a house and growing a lawn or plants below them, reducing the energy required to power an air conditioner, and benefiting from growing a vegetable patch or fruit trees.

"But it’s still important to be smart with your water use, by being strategic in where and when you use it for cooling.

"An established green lawn or garden only needs enough water to maintain moisture levels, so that the cooling effect of the watering is felt for up to three days afterwards."

Greg Ingleton presents ‘Adelaide Airport Heat Reduction’ at Ozwater’18 on Wednesday 9 May 2018 at the Brisbane Convention and Exhibition Centre.

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