On March 22, World Water Day, the United Nations Secretary-General Ban Ki-moon urged the international community to be cognisant of the numerous water-related challenges the world faces. The state of the world’s water supply was underlined in the UN’s 2015 World Water Development Report that forecasts a 40% shortfall in water supply. As one of the most arid countries in the world, water security is a strategic imperative for the UAE. This is why Dubai, through its Dubai Integrated Energy Strategy (DIES) 2030 plan, has set the ambitious target of reducing water demand in Dubai by 40% by 2030. With a mix of conservation practices, innovative technological solutions and interactions with the global community, Dubai appears to be determined to tackle the water crisis.
Desalination is the most important source of the UAE’s water supply. Virtually all of the country’s drinking water is sourced through desalination. But the process is energy-intensive and dependent on the availability of precious energy resources. In response, Abu Dhabi launched the Masdar Renewable Desalination Pilot programme, which is a visionary approach to addressing the water-energy crisis through a more sustainable power and water relationship. The country is also researching into technologies that address groundwater shortfalls through the establishment of the UAE Programme for Rain Enhancement Science, which was launched in January during the Abu Dhabi Sustainability Week. The programme, an initiative managed by the National Centre for Meteorology and Seismology, provides grants of up to USD five million to encourage institutions, researchers and scientists to investigate new means of increasing rainfall, not only in the UAE, but also in arid and semi-arid areas all over the world.
Then there is the technology involving air conditioning condensate water recovery. During building cooling, air passes through the chilled cooling coils in the Air Handling Units (AHUs) prior to entering the facilities. In summer, the weather being generally hot and humid, as air passes over the cooled coils, condensate forms rapidly, dropping moisture from the air on to the cooled coils. “Condensate water is an untapped source of water,” says A Bhaskaran, Manager (Water Treatment Division) at Abu Dhabi-based Water Bird. “During summertime, there is too much of collection of water. And most of the time it just flows into the drain. Nobody is collecting this because majority of the building has no system to collect all the water and send it to a particular area.”
Masood Raza, General Manager at Jumbo Engineering, who is a veteran when it comes to condensate recovery projects, says: “The potential of condensate drain reuse was realised in the region in the 1990s of the last century. I was involved in design of standalone collection systems for air handling room condensate drains for some clients like Etisalat. But, the elaborate design for its reuse was not considered at that time.”
With the increasing awareness of energy and environment issues, condensate recovery became a priority in the UAE, he observes, and acknowledges. “DM Green Building Regulation now makes it mandatory to use condensate recovery systems for all new buildings with over 350 kW cooling load.”
How much of water are we talking about?
All this talk about recovery would make one wonder about the volume of water collected as a result of condensation. “A standard air conditioning unit will produce on average 5,475 gallons of grey water a year, meaning that an average tower block of 150 flats could recycle up to 22,500 gallons of water per month.” This statement by Serge Becker, Sales and Marketing Director at Aspen Pumps, appears in a letter sent to architects in India, on the importance of condensate water recovery. Vikash Sekhani, Director of Sales and Marketing at SAFE A&T Technology, India, who also provides marketing services to Aspen Pumps, shared this information with Climate Control Middle East, to give readers an idea of the volumes of water involved.
Talking in terms of percentages, Zafar Muhammad, Head of District Cooling at PAL Technology Services, says: “We have done a design study, basically, and our theoretical calculation says that there is eight to 10% water from condensate, which can be a part of our water usage.” Raza, too, agrees with this figure, which is as per theoretical calculations limited to Dubai peak conditions. However, he believes that much more can be recovered, and that it depends on outdoor conditions and outdoor air required for the project. “We have proven case studies from hot and humid areas in the United States of very successful condensate water tapping from Air Handling Units, especially in occupancies where outdoor air requirement is high, amounting to 16% of makeup water demand for cooling towers,” Raza claims. He adds that it can go even higher, “For high outdoor air use, it has been proved in some studies in the United States that 10% to 40% of cooling tower makeup can be tapped from the condensate recovery.”
The best possible use of condensate water, Raza says, is for cooling towers. “The water quality is suitable, and due to lack of minerals, it can greatly improve the cycles of concentration, and thus bleed can be reduced,” he claims, and elaborates that huge District Cooling plants that are being designed and constructed in the region have the greatest potential for collecting and reusing the condensate for cooling tower makeup. Other than this, Raza believes, it can also be used for irrigation, domestic purposes and swimming pools.
Muhammad, another veteran in the field, says: “I see a solid ground that all District Cooling providers should look into this [condensate]. It will basically help them to recover and manage their costs. It helps nature and reduces the carbon footprint. We being a DC provider are doing this in all our current and future projects.”
Return on investment
Despite the array of benefits, the question remains whether or not investment costs justify such ventures. Almost all HVAC players unanimously agree that the initial investment costs are negligible. Raza explains: “The collection system costs are very limited to a separate condensate riser. The only additional cost inside the building is a plastic riser and a collection tank. The rest of the requirements within the building are in any case needed, even if we do not connect the condensate to the building drain system.” He also points out that with the increasing cost of potable and TSE water, it makes better business sense to have a recovery system in place. “Actually, it is a low-hanging fruit which just needs to be plucked,” he says.
Sharing information about the recovery system at the District Cooling plant on Reem Island, Abu Dhabi, which serves its residential and commercial occupants, Raza says: “The plant has a final capacity of 90,000 TR. During the design of piping network, one additional condensate collection pressure pipe was laid with negligible cost. All building owners were asked to collect the AC drain through a separate riser and bring it to an enclosed water tank in the ETS room. A pump station was installed next to the water tank that pumped water to the pressure pipe laid along the external chilled water pipe network back to the plant. A separate water tank was planned for this collection to monitor the quality of the condensate water.” Regarding the ROI, Raza says, “In the Reem Island plant, the cost was very limited and the payback time for the operator was no more than a couple of years.”
Sekhani, on his part, believes that as long as installation of a proper collection system is done when the building is being built or refurbished, the costs could be minimal. “Saving money and conservation,” he says, “go hand-in-hand.”
Case study 1: Sheikh Zayed University, Al-ruwayyah, Dubai
The HVAC system at the university comprises water-cooled chillers and primary and secondary chilled-water distribution systems. The secondary distribution system is complete with Variable Frequency Drives (VFDs) and two port-modulating valves. The air distribution system is based on the concept of Variable Air Volume boxes with VFD-type AHUs. Outdoor air is supplied from the central fresh AHUs. The condensate drain from different AHUs are collected for reuse as cooling tower makeup water. (Information source: Masood Raza)
Here’s what Masood Raza has to say about the project: “In Sheikh Zayed University for Girls project (2004-2006), under the patronage of Dubai Municipality Project team, I was involved in the design of one of the first condensate recovery systems for use as cooling tower makeup. The system had two underground collection chambers. The condensate was collected from the air conditioning units through an independent system of gravity drains. It was pumped to the makeup water tanks from these collection chambers. The system is fully functional and is in use for cooling tower makeup and irrigation, alternately.”
Case study 2: US Environmental Protection Agency’s Science and Ecosystem Support Division
After severe droughts in the south-eastern United States, the US Environmental Protection Agency (EPA) decided to address the need for water conservation and develop a water management plan for their Science and Ecosystem Support Division (SESD). The water management plan aimed to reduce SESD’s potable water usage (more than 2.4 million gallons in fiscal year 2008) through an air handler condensate recovery project. The EPA SESD spreads across 12 acres in Athens, Georgia. A single laboratory building was constructed in 1996 consisting of 66,200 square feet configured for a mix use of laboratory and office activities. In May 2008, SESD completed an air handler condensate recovery system. The system routes condensate from rooftop air handler units to the facility’s cooling tower, reducing potable water usage and improving cooling tower water chemistry.
EPA claims to have spent USD 24,500 on the air handler condensate recovery project. The cost included installation of a flow meter to measure total gallons recovered and directed to the cooling tower. EPA informed that from May through December 2008, the project saved it more than 540,000 gallons of water, resulting in a 16% total reduction in SESD’s overall water use. The water savings is valued at USD 3,500 at a rate of USD 6.52 per thousand gallons of water. The system also improved cooling tower water chemistry, and is expected to reduce overall chemical treatment costs due to the nearly-pure recovered water. EPA estimates a simple payback of less than six years based on savings recorded in the first year of operation. Additionally, EPA claims that SESD significantly reduced water consumption from fiscal years 2007 to 2008. In 2007, the water consumption baseline reportedly measured 3.4 million gallons, whereas, in 2008, that number measured 2.4 million gallons, marking a 25% reduction in water consumption. Due to the success of the air handler condensate recovery project, EPA intends to implement the project at all facilities that fall under the same climatic conditions.
(Information source: http://energy.gov/sites/prod/files/2013/10/f3/epa-scesd_watercs.pdf)