Recycling AC waste water

UAE companies are turning to reusing air conditioner condensate to reduce the energy consumed by buildings

Image Credit: Gulf News Archives
Gardening solutions: In humid climates, home air conditioners can generate up to 68 litres of condensate — enough water to maintain small gardens
GN Focus

Brad Lancaster, author of Rainwater Harvesting for Drylands reminisces about a trip to Jeddah, where he found it interesting that water was “flowing down the streets” in a country that receives only 50 millimetres of rain in a year. This water turned out to be condensate from the vast army of air conditioners in the city — drip by drip the water had become a steady stream. “But on occasion you see a wild matrix of funnels and hoses directing that condensate from coolers to courtyard plantings. Here, where rainfall is low but humidity intense, the potential for condensate and dew harvesting is very high,” Lancaster writes. He estimates that in dry climates, a home air conditioner can generate one litre of condensate daily, while a large commercial air conditioner can generate a staggering 1,900 litres daily. In humid climates the numbers are more impressive: 68 litres a day from home units and 7,500 litres a day from commercial. That’s more than enough water for fountains, to water small gardens, for evaporative cooling, laundry, washing vehicles, and flushing the toilet. If treated and filtered properly, it can also be turned potable. Bob Boulware, President of Design, Aire Engineering, writes on the website Environmental Leader, “As water shortages become more widespread, condensate from air conditioning is gaining increased attention for creative non-potable and potable applications.” Dubai Electricity and Water Authority, in an advisory, writes that hotels in Dubai have “one of the highest rates of water and electricity consumption in the world”. It emphasises cutting down on waste, recycling, and using alternative energy sources such as solar power. Dewa’s overriding hope is that “environmentally responsible practices will prove beneficial to your business as well as to our resources and environment”. Businesses are indeed listening. Among the many examples Dewa cites is the Al Maha Desert Resort & Spa in Dubai, which incorporated energy-saving construction materials that significantly reduce air conditioning needs. It also has 100 per cent water recycling programmes. Elsewhere, Ski Dubai in Mall of the Emirates uses an efficient energy-saving recycling scheme whereby each day, 30 to 40 tonnes of waste snow is used as chilled water to supply the entire mall’s air-conditioning system. The same water is also used to irrigate the gardens and green spaces around the property. These efforts have enabled the mall to operate on one of the lowest cooling loads compared to other commercial buildings of a similar size. The Holiday Inn Resort Sharjah, winner of the first Conserve Our Planet Award, has also implemented various energysaving ideas, including “using treated waste water for their waterfalls and plant beds and changing the make-up of the hotel’s cooling tower”. Air conditioning consumes massive amounts of energy — an estimated 40-50 per cent of a building’s electricity use. Any savings or recycling in this area significantly impacts the annual energy bills of households as well as businesses. No wonder it has been a focal area for interesting innovations and offbeat ideas.

Chilled ceilings

This works on the principle that warm air rises and cold air falls. In what is seen as a simple and elegant solution, beams with inbuilt cooling coils are placed at ceiling height. Warm air in the room rises and passes through these coils and the resulting cooled air drifts down. According to Ashrae, a global society dedicated to promoting sustainable technology for the built environment, chilled beams provide up to a 30 per cent reduction in energy use and save on construction costs by eliminating the need for AC duct works. Apart from the occasional cleaning, they also require almost zero maintenance.

Data furnaces

These days, everything is moving to the cloud. But keeping the cloud afloat are massive server farms and data centres, which are notorious for consuming energy. As a by-product, they generate copious amounts of heat. Reportedly 2 per cent of the energy consumed in the US goes into keeping data centres cool and running smoothly. In a research paper, Microsoft proposed an elegant solution: data furnaces. The idea is the creation of a distributed data centre where server CPUs are spread all over a neighbourhood and connect to your home’s heating, ventilation and air conditioning (HVAC) system. So instead of dealing with the heat at a centralised location, it is used to warm homes during winters and for sundry household chores that use heat. Data centre and telecom companies Telehouse in the UK and Telus in Canada are already supplying the air-conditioning systems of properties close to their offices with excess heat from their centres. A similar idea has been proposed by telecom company Bahnhof in Sweden. IBM also heats up a community swimming pool with its data facility in Switzerland.

Situational awareness

HVAC manufacturers too are thinking up ways to cut down on energy costs. Hitachi has developed its IT facility Linkage Solution for Energy Saving, which, based on load and present conditions, ensures that air conditioners automatically adjust their energy requirements, leading to a 30 per cent reduction in power consumption.

Freezing energy costs

Companies such as the renewable energy provider Ice Energy have turned to ice to freeze rising costs. Its Ice Bear system plugs into an existing AC system and delivers “an average reduction of 12 kilowatts of source-equivalent peak demand for a minimum of six hours daily, shifting 72 kilowatt hours of on-peak energy to off-peak hours,” the company says. It acts as a “battery for the air conditioning system. Only this one is cooler, because it’s made out of ice”. At the heart of the system is a large thermal storage tank that that makes ice at night when the demand for electricity is lower and then uses that ice during the day “to efficiently deliver cooling directly to the building’s existing airconditioning system”. Other energy-saving ideas include solar air conditioners such as those manufactured by Helios Green Technology. As energy costs spiral out of control, expect more technology to emerge with the promise of overhauling how we look at air conditioning — and how much we pay for it.

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