Cover Story

Use of Recycled Condensing Water as Make-up Water for Cooling Towers

A green initiative

In the past issues of Environmental Newsletter, many energy and resources saving measures on our campus had been reported indicating PolyU’s continuous efforts and commitment to protecting the environment. Recently our Campus Development Office (CDO) has made another big step forward in regard to save water and electrical power – the use of recycled condensing water as make-up water for cooling towers. After a long strive for approval from the authorities, PolyU succeeded in putting this green initiative into practice. The PolyU premises are the first ever buildings in Hong Kong utilizing such innovative water and energy saving system. 

Where does this idea come from?

It is a natural phenomenon that water vapor condenses to water on a cool surface with its temperature below the dew point. Condensed water, therefore, will form on the surface of different components of the air conditioning system including the chilled water tubes inside the fan coil unit and primary air handling unit, etc. More condensed water will form in the summer time compared to other seasons due to the relatively higher humidity and the large environmental temperature difference. With respect to the traditional design of air conditioning system, such condensate will be collected and drained off via the drain pipes to the communal sewage.

During the continuous review for system improvement process after construction of the Li Ka Shing Tower in 2000, CDO colleagues identified that there was a considerable amount of cool condensate being continually drained to the sewage as wastewater. They then came up to two ideas as to reuse this huge amount of water -- the first one was to irrigate greeneries on the campus and the second one was to be used in flushing.

They tried to apply these ideas to the construction of Lee Shau Kee Building in 2005. However, these two water-saving ideas seemed to be not quite feasible. As for irrigation of greeneries on campus, the amount of water required is much lower than the amount of condensate collected. As for flushing purpose, the cool condensate in the flushing pipe may cause air moisture condensed on the surface of the pipes inside pipeduct. This situation is not desirable especially in the toilets. Moreover, bleed-off water from cooling towers of the air conditioning chiller plant has already been reused for toilet flushing.

Having been aware of the stored energy in this condensate, which is cooler than the ambient environment and can be effectively used for cooling purpose, they finally devised to reuse this water in the water cooling towers. Energy will be thus saved by a shorter running time of the cooling tower fan motors to achieve the target cooling temperature in one hand and water consumption will be greatly reduced for water make-up on the other hand.

Putting the idea into practice

In PolyU, building air conditioning system works on refrigeration principles, using cooling medium to lower the indoor air temperature. The heat absorbed by the refrigerant via cool circulated water is then rejected to the outdoor environment either directly to the atmosphere (i.e. air-cooled) or by evaporation through cooling towers (i.e. water-cooled). For the water-cooled air conditioning system, water in cooling tower will be lost due to continuous evaporation, bleed-off and wind drift. The water loss will be replaced by water coming from the city water mains.

Use of air conditioning condensate to make up for fresh water from the city water mains seems to be a “golden match” of water and energy saving. During the design stage of the PolyU Teaching Hotel in 2007, CDO commissioned professional consultant to include this green initiative into the design and construction. However, approval for the system design could not be obtained from the Authority since that was a new initiative and officials from the government needed time for thorough consideration.

Nevertheless, CDO insisted on putting this new green initiative into the design for the subsequent capital projects including Student Hostel Phase 3, Innovation Tower and Phase 8 Development and seeking approval from the Authority at the same time. During this period of time, CDO liaised not only with the Electrical and Mechanical Services Department (EMSD) for applying this new energy and water saving initiatives to the “Pilot Scheme of using Fresh Water Cooling Towers for Air Conditioning Systems”, but also the Water Supplies Department (WSD) for approval of the use of reclaimed water. Due to complicated communication channels between government departments and the lack of reference, the approval application dragged on for a few years.

A breakthrough was seen at the end of 2010 when Ir Kenny Chan (current Associate Director of Campus Development) shared his experience on environmentally friendly design for campus development in an open forum. There he met a member of an advisory committee of WSD who showed much interest and concern about the said idea and offered help to follow up with the application. In August 2012, CDO received an official approval from WSD for the system on re-use of air conditioning condensate for water cooling towers in our Student Hostel Phase 3 at Homantin.

Looking ahead

With the approval of this new system at one of our capital projects, it sheds light on the approval for the remaining two capital projects. CDO is expecting that approval for Innovation Tower Project and Phase 8 Development Project will come shortly. The main restriction on wide adoption of this system on campus is that it needs advanced design and planning for dedicated condensate drain pipes to collect condensate which will then be directed to a collection tank for reuse.  Due to the limitation of space and diverse locations of the drain pipes for air conditioning condensate in existing PolyU buildings, it will be very difficult, if not impossible, to re-direct the existing drain pipes for collection of condensate even with great expense.

As a green initiative included in the application for the HK-BEAM award for our Student Hostel Phase 3, this new system will certainly be a credit for obtaining higher score to attain our target for the highest Platinum Award standard. CDO also wishes its pioneering work will be recognized and adopted by other buildings in Hong Kong. 


Activities and Development on Campus

Product Design Show at PolyU

The Department of Mechanical Engineering successfully organized a five-day product design show with the theme “Design with Impact through Innovation” from 5 to 9 November 2012 on the PolyU campus. This show was divided into four zones, namely "Houseware Products", "Kitchenware Products", "Electrical Appliances" and "Green Materials and Plastics" displaying 25 prototypes and 60 other ideas of industrial-sponsored student projects in posters. The series of industrial-sponsored projects aimed to nurture engineering students’ creativity in product design and consideration for environmental protection.

Forum on Sustainability in Construction

A forum on “Sustainability in Construction”, jointly organized by University of New South Wales (School of Civil and Environmental Engineering) and The Hong Kong Polytechnic University (Department of Building and Real Estate), was held on 19 November 2012.

This forum assembled a group of prominent speakers who are experts in their fields. They addressed emerging issues in sustainability as to the impacts on construction. Sustainability in construction does not only represent a business opportunity and potential for cost savings, but also contributes to the well-being of companies, employees, environment and public image. Its prominence will continue to rise within the coming years.

Seminar on "some Thoughts on Global warming"

A seminar on global warming organized by Department of Mechanical Engineering was successfully held on 7 November 2012. The speaker Prof. Harvey Lam is an expert in astronautics. He taught in Cornell University and Princeton University previously; was elected fellow of the American Institute of Aeronautics and Astronautics and member of the American National Academy of Engineering.

This seminar attracted lots of participants including Professor Timothy W. Tong, PolyU President. It focused on green house effects, atmospheric carbon dioxide, carbon dioxide annual emissions, Earth’s thermal inertia and policy issues, etc.; which were well received by the audience.



Dolphin Viewing Trip

A new student’s environmental group named “The Green Society” (綠行社) organized a meaningful dolphin viewing trip at Sha Chau and Lung Kwu Chau Marine Park (沙洲及龍鼓洲海岸公園) on 10 November 2012.  Around 70 participants joined the trip to view a large number of Chinese white dolphins (中華白海豚) on a sunny day. All of the participants had a memorable and enjoyable trip.

Through this trip, the participants learnt about ecotourism and its development in Hong Kong. They also had a better understanding about the impacts of running the Hong Kong International Airport’s Third Railway Project on dolphins; the current threats as well as remedies. The key purpose of this trip was to raise students’ awareness about environmental protection. 

Resources Conservation

Award for Power Smart Energy Saving Contest 2012

As reported in previous newsletter, PolyU joined the Power Smart Energy Saving Contest 2012 organized by Friends of the Earth (HK) during last year’s summer. It is our pleasure to let you know that we have succeeded in reducing the target of more than 2% of electricity consumption during the period from 1 June to 31 August 2012 (92 consecutive days) on our main campus compared to that in the corresponding period in 2011.  

With the efforts by our Facilities Management Office and the cooperation of all PolyU members, this achievement is certainly encouraging that would draw us towards a green campus.


Used-Item Collection Campaign

In view of the favourable response received from “Used-Item Collection Campaign” in past few years, this Campaign was re-run on 21 and 22 November 2012 on campus.  It was organized by Polytechnic University Staff Association (PUSA) and Industrial Relations Institute (IRI).

IRI is a charitable organization that gathers used items from the community and re-sells them at a very low price to low-income families in Sham Shui Po after proper selection and treatment. Same as previous years, the overall feedback was satisfactory. A total of 1,490 kilograms of used items were collected in the event. These collected items, all in good conditions, include clothing, shoes, bags, household items, stationery, toys, beddings, books, VCD, DVD, CD and electrical appliances, etc.       


Pollution Control

Better Air Quality Conference 2012

The Hong Kong Polytechnic University joined hands with Environmental Protection Department of the HKSAR Government and the Clean Air Initiative for Asian Cities to host “Better Air Quality (BAQ) Conference 2012” from 5 to 7 December 2012 on campus. The theme of this year was “Growing Cities, Healthy Cities”.  The three-day conference included plenary sessions, breakout sessions, country roundtables, exhibitions and social events.  It was the second time that BAQ Conference was held in Hong Kong since 2002. It is now organized biennially and has become a leading regional event on air quality management.

As the host of this conference, Prof. Timothy W. Tong, President of PolyU, mentioned that BAQ 2012 provided a timely platform for Hong Kong and regional policy makers, academics, practitioners, NGOs and technology providers to share best practices and strengthen cooperation in their common quest for better air quality in the course of a more sustainable urban development. Mr. Wong Kam-sing, the Secretary for the Environment of the HKSAR Government, and specialists from other countries also shared their views and related strategies on air pollution. Participants of this conference were called upon not to succumb to adapting to air pollution but to take action in their daily lives and by putting pressure on local and national governments to scale up action on air pollution and better enforce air quality standards.

Waiving of Campus Parking Permit Charge for Electric Vehicle

To promote sustainability, the Management, based on recommendations of the Campus Sustainability Committee, has approved concessionary charges for annual campus parking permit for staff who drives electric vehicle/hybrid vehicle with no/low exhaust emission. The annual campus parking permit charges will be waived for electric vehicle and will be reduced to HK$1,000 a year for hybrid vehicle.

Following the inclusion of Mycar in the transport fleet of the University and provision of an electric vehicle charging station inside the campus carpark, this new measure demonstrates the University's continuous commitment to green transport which contributes to sustainable development.

The Facilities Management Office will review the above arrangement annually and implement necessary measures as deemed appropriate.

Let us join hands in building a sustainable campus!


News and Tips

Update of Material Recycling on Campus

Recycling bins are placed at convenient locations on the PolyU campus for general recyclable materials such as paper, plastic and metal. In addition, new collection facilities for other recyclable items including glass bottles, plastic bottles and printer cartridges have been set up. Here is an update:

Glass bottles – large recycling bins for glass bottles have been placed at three locations on campus since September 2012. Up to mid of December 2012, collected glass bottles have filled up three recycling bins with a total volume of 720 litre (each bin of 240 litre).

Plastic bottles collected through Recycling Vending Machines (RVMs) – since these machines were put in three locations of the campus in late August 2012, around 900 bottles have been collected, i.e. an average of 10 bottles a day.

Printer cartridges – PolyU has been participating in the recycling program for used printer cartridges (including used toner cartridges from laser printers/ photocopiers/ fax machines and ink jet cartridges) organized by the Greeners Action since early 2011. Dedicated bins for recycling of printer cartridges are placed at seven convenient locations of the campus. Over the past six months, 60 pieces of cartridges have been collected.

Having these recycling facilities for different materials in place, we can make good use of them and contribute to protecting our environment.