WHERE DO WE STAND ON TES AND TSE VIS – A VIS NEW DUBAI REGULATIONS FOR THE DISTRICT COOLING INDUSTRY?
By George Berbari

In the early stages (1996 – 1999) of the implementation of district cooling in the UAE, the biggest hurdle and taboo was the large demand for water which as required as make up and blow-down water for cooling towers.

Water is equal to life in the collective memory of the UAE and the GCC. Water scarcity and the psychological importance of water have played a major role in deeming that air – cooled air conditioning systems would be the equipment of choice. Indeed, air cooled system contributed to 99% of the total air conditioning market in the GCC. In fact,
It would not be inaccurate to state the mindset was definitely against water-cooled systems.

To break that resistance and to start a major turnaround from air-cooled to water- cooled system in the UAE and the GCC. I conducted a feasibility study on power generation and distribution, water desalination and distribution, sewage collection and treatment, and Natural Gas distribution to assess the impact of the type of air conditioning system on the country’s infrastructure and the environment. (A major business consultant assisted me in the study.)

The study revealed that the saving in the infrastructure cost would vary from Dh4,000 to Dh9,000 for every tonne of cooling when the shift per tonne was made from air-cooled to water-cooled. The range depended on whether or not it was drinking water, sea water or treated sewage effluent (TSE) was utilize, and on whether or not thermal energy storage (TES) was utilize, and on whether or not alternative fuel, such natural gas or diesel, was utilized as a primary source of energy, in lieu of grid electricity. The result of this study is tabulated in Table 1.

Table 1: Various A/C system comparative study. Total infrastructure capital investment by GCC governments.

Moreover a large water-cooled system has a lower capital cost and operating cost than an air-cooled system. In addition, a lower CO2, emissions rate and other environmental benefits make the case for a water cooled system a compelling one, indeed. These attributes have convinced the local authority to give the green light for a massive implementation of water – cooled systems. Today, almost all large air conditioning system – 2,000 TR and above – are water- cooled.

In my first project in the UAE, I was with another company then – we faced an absence of water. As a result, we had to think out of the box and install a water transmission line that was 30 kilometers long and 400 millimeters in diameter to bring water for the seven district cooling plants which had a total capacity of around 80,000 TR. As a private sector we secured the first approval for the water transmission line, which was highly critical to offer a competitive district cooling solution. That water line’s importance to my earlier company was similar to the importance of the Nile to Egypt. In fact, it laid the foundation for the success of the first district cooling scheme in the Middle East., which in turn, has today resulted in flourishing industry that commands 10 billion dirhams in planned investment for the near future.

From the beginning we had known the importance of TES for the country’s infrastructure. After early implementation, we confirmed the economics benefits of TES – 20% of the plants chilled water production equipment can be offset by TES, simply because energy can be stored during the peak night hours and utilized during peak day hours. The benefit of TES and the daily profile are described in Chart 1

Today, the cost of stratified chilled water TES in that project is below Dh 2,000 a tonne compared to more than a Dh 5,500 a tonne for the chilled water plant. A saving of Dh 3,500 per tonne multiplied by 20% of the plants capacity has resulted in a construction cost reduction of Dh700 a tonne or 12.7% of the total plant cost. The operational data is the result of an analysis of actual daily profiles during the summer season. Furthermore; TES allowed operational flexibility, since it became possible to operate the equipment always close in the full load, which improved operational efficiencies by around three percent.

Later, while operating a district cooling scheme in Dubai, we have shifted the plant from operating with fresh water to TSE water, this has been since 2004. The shift has resulted in an annual savings of Dh 3.5 million a year, in addition to the environmental benefits that resulted from water conservation.

Recently, the Dubai Infrastructure and Environmental committee in conjunction with Dubai Municipality announced in a meeting with executives of District Cooling companies, that all district cooling companies in the Emirate have an 18-month grace period to implement TES technologies and also to use TSE as make-up for cooling towers for all new district cooling schemes.

Now, did the industry require this regulation to begin implementing system and processes that make economic and environmental sense? Surprisingly, the answer is, “yes”. And that has been because of the prevailing mindset and a lack of knowledge of these technologies which made them outside the comfort zone of most district cooling providers.

The discussion on TSE brings us in a different subject to a different line of thought. Indeed, what is the impact of utilizing TSE water on district cooling energy rate? Starting March 1, 2008, the Dubai Electricity & Water Authority ( DEWA ) introduced new utilities slab rates. With the new rates, all district cooling providers have raised their rates to as low as 45fils/tonne – hour and as high as 50fils/tonne – hour. If fresh water is utilized, the recommended rate is 46 fils/tonne-hour: on the other hand, with TSE, the recommended rate is 39 fils/tonne–hour, as seen in table 2.

The utilization of TSE can reduced the district cooling energy rate by around 15% or seven fils a tone-hour or Dh245 a tonne a year. That should improve the competitiveness of district cooling vis-a-vis traditional air conditioning system and would save the country infrastructure-related cost of Dh 2,462 tonne as compared to district cooling plants that use drinking water and no TES, as is the case with most district cooling plants in Dubai.

Since our pioneering effort in transferring district cooling technologies to the Middle East, I was committed to show the impact of TES and TSE by demonstrating their feasibility and significance over time. My team and I have so far designed more than 600,000 TR of district cooling schemes. Most of them have TES and the ability to operate on TSE water as a main source and on drinking water as a backup. Once you make the case for the district cooling companies or owners, very few would not implement the obvious.

One of the drawbacks of chilled water TES is the large footprint requirement. Every 2.7 tonne-hour of stored cooling energy requires approximately one cubic metre of tank volume. However, it is possible to optimize the design and achieve the purpose on a smaller footprint. In some places, my team and I have used either a decorative skin for the tank or concrete tanks, as part of the buildings to conceal the thermal storage tank in critical areas.

We have always managed to make a strong case for district cooling TES, and we are pleased to see regulations coming into place. It is most likely the authority has been encouraged by successful district cooling implementation over the past 10 years and by recent environmental drives that are surfacing in what is known as the energy revolution of our times.

Next month, I will address the negative impact of the utility slab rates on the district cooling industry and the recommended solution.