Michel Farah, Regional Director (UAE & Gulf), Trane, introspects on utilisation level of district cooling plants and other issues, in this interview with Climate Control Middle East.
What is the utilisation level of plants that are run with Trane Chillers in Palm District Cooling?
In the case of district cooling plants, there is more capacity for production of chilled water than demand. This could be due to different reasons. The slowdown in real-estate projects could be a factor, mostly because the district cooling plants have been designed for full capacity; however, some projects are being constructed in different phases. Moreover, the demand for cooling is created by occupancy, not by selling the property, since many people buy the property but do not occupy it. So, the low cooling loads in many developments are due to low occupancy rates. Therefore, some plants are not running at full capacity. However, it is like building for infrastructure - you build for the years to come. Overall, one could say the current utilisation level of district cooling plants ranges between 40% and 60%, depending on the place.
One thing that draws attention is that when the option of using district cooling was spreading, due to increasing awareness of energy-efficiency concepts, as well as various means to reduce energy consumption, especially for bigger projects, what was not seen as a step in the same direction was the rates DEWA was charging large energy consumers. The rates especially penalised district cooling companies. Action could have been considered differently as a benefit to the larger community as a whole. The role of district cooling plants could have been acknowledged, considering the role district cooling plays in promoting energy efficiency, which could have led to the formulation of special tariffs, so that cost savings could be passed on to the end users. Some end users are not able to easily accept that district cooling is a more effective solution as compared to traditional air conditioning.
What would be your message to Palm District Cooling, in terms of operating these plants under the present circumstances? How can the energy-efficiency ratio (EER) be improved? How can total plant efficiency be improved under low-load conditions?
The aim of any production facility is to reduce production costs. This can be achieved by running a good operation, using all the service and maintenance procedures recommended by the manufacturer. To improve efficiency, procedures such as cleaning the heat exchanger, are very important with reference to improving the efficiency of a running chiller. Also, in the case of low-load conditions, opting for the use of controls installed, to have equal loads between chillers ensures minimal stress on individual chiller units. Furthermore, sequencing (lead-lag) equalises the number of operating hours, by ensuring that the chiller that starts first in the first cycle, should not be the one that starts first in the next cycle, and so on.
It is said that residents are being charged $2.25/square foot/year for chilled water. How would you compare it with your estimates?
At The Climate Control Conference (C3), held in May-June this year, we heard conflicting information on what various projects were charging. Moreover, to end users, these charges make no sense, especially since there are various additional charges, such as the connection charge. The rates need to mature to give end users visible benefits, rather than a quick way for district cooling providers to repay capital investment. Moreover, for some end users, some of the charges are included in the rent, while the BTU meter charge is separate, and some charges are paid by the owner of the apartment. There needs to be a single measuring system, just as utility providers have kW/hour or gallons/minute.
District cooling is supposed to consume relatively less power compared to the other types of systems for providing chilled water to these buildings. What is your team's estimate on this till date with the plants done in the UAE? Is it more or less equal to what you thought it would be?
Theoretically, it should be less. The machine itself, for air-cooled condensation, on an average, is 1.5 kW/tonne, while water-cooled set-up, which is more efficient, goes down to 0.5 kW/tonne. With a cooling tower, consumption does increase a bit, but it is less still by about three times. So one could say, consumption is reduced from 1 kW/tonne/hour to 0.5 kW/tonne/hour. However, the water used in this case, has to be processed at a desalination plant first. This does not take into account the power used to process the water. For large capacities, a water-cooled system is more efficient, but more maintenance and care is required to keep it at this rate.
If you were to talk to a consultant today on proposing a district cooling concept for Jumeirah Beach Residence (JBR), would you do anything differently as compared to the present way the plant is set up?
In the case of JBR, the design was done for high capacity, as it was for a large group of about 50 buildings. For this, what could have been done, was to take more diversity and reduce the total load of installed capacity by 5-10%. What is meant by 'more diversity', is to base calculations on the premise that not all loads come at all times, and not design for worse case, but rather for 80%-90% of the full-load requirement. In addition, the maintenance and operations procedures could be done better by ensuring more frequent inspections to units. Standard operating procedures need to ensure periodic checks and analysis, since these factors also affect or reduce efficiency of the plants otherwise.
© Climate Control Middle East 2009
