Cooling sector should think greener

The emergence of district cooling has had a massive impact throughout the Middle East, but cooling towers are the latest breath of fresh air to hit the market, as Zoe Naylor discovers.

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By  Zoe Naylor Published  April 15, 2006

|~|AC200.jpg|~|With the growing number of offshore development projects developers are being forced to address the environmental implications of the air conditioning technology used.|~|The Gulf’s booming property market, coupled with a rapidly growing population, is placing unprecedented demands on the region’s power supply. Air conditioning in particular consumes a vast amount of power in any building. And given the recent surge in offshore mega projects such as the Palms, the World and the Durrat Al Bahrain island project, developers must consider not only energy cost implications but also the environmental impact of cooling systems. One largely untapped option is sea water cooling towers, which are of particular interest bearing in mind the GCC nations’ proximity to the waters of the Gulf. “If you look at the types of projects in this region, it’s only really in the past couple of years that projects have been developed on the shore,” says Aslan Al-Barazi, executive director of IMEC, representatives for SPX Cooling Technologies. “And since these projects are right next to the sea it only makes common sense to use seawater cooling towers because of the availability — it’s right there, so why not use it?” Last year, SPX was commissioned to provide a seawater cooling tower in Jubail, Saudi Arabia, for a petrochemical project. And while seawater cooling towers have yet to be used within the UAE on residential projects, SPX has already supplied them to residential projects in Kuwait and is in discussions to supply them to future Kuwaiti island developments. To understand the benefits of sea water cooling towers, recent changes in the local cooling sector first need to be examined. “Up to the late 1990s, nobody here would have considered using cooling towers on their projects — there were some misconceptions surrounding them,” says Al-Barazi. “Instead, air cooled systems were used. It was only when district cooling came into play in 2000 and onwards that people started to see the benefits of cooling towers.” According to Al-Barazi, there are numerous benefits of using water-cooled chillers over air-cooled systems: “Cooling towers can offer 50% energy savings over air-cooled systems,” he says. “You may need four to six times more air cooled chillers than you would need in a water-cooled system.” This means that there is more equipment to replace and maintain with air-cooled chillers, plus they use up more space, which will ultimately affect their location. When it comes to water-cooled systems, the main difference between fresh water and sea water cooling towers is that salt water vapour pressure is lower with fresh water i.e. evaporation occurs less readily in salt water. “You’re still using the same cooling tower, but you have to include design considerations such as increasing the wet bulb.” There are two main types of seawater cooling tower: circular-shaped towers and cell-shaped towers. The circular towers are larger and more suited to industrial applications, whereas the cell types are arranged next to one another in groups. “These cell types are very similar in size to the normal cooling tower shapes that are already used on residential projects,” says Al-Barazi, who believes that sea water cooling towers are set to make a real impact in this part of the world. “There are big advantages when you consider all the island projects being developed in Dubai, Abu Dhabi, Sharjah, as well as in Kuwait and Bahrain — everybody now wants to have an island.” He says the typical flow rates on these islands can range from 700,000 gallons per minute up to 1,000,000 gallons per minute. “That is high flow rate, especially given the fact that in this area, fresh water is a very precious resource. And we’re talking about projects that range from large to mega large. Fresh water should not be used for such large projects. Moreover, the seawater is there and can help to save a lot of money. This is the best time to consider seawater-cooling towers, given all the marine touristic development projects.” The towers can work up to a distance of seven to 10km from the sea shore. Any more than this and the costs will start to increase due to the length of piping needed to pump the water from the sea. Al-Barazi adds that they are only really suitable for medium-to large-scale projects above 4,000 or 5,000 tonnes of refrigeration requirement: “It’s not really worth using them on small projects because of the work involved in developing it.” In addition to being suitable for large-scale shoreline residential developments, sea water cooling towers are an environmentally friendly alternative to conventional sea water ‘once through’ cooling systems. Once-through sea water pumping stations are widely used in the Gulf for oil, gas and power industrial applications — and have raised considerable environmental concerns. “Warm water enters the pumping station and hot water is discharged on the other side. The heat exchange in the middle cools down the forces and the hot water is discharged,” explains Al-Barazi. He says that the problem is that the return temperature of the water into the sea is very high — around 450C. And marine creatures cannot survive temperatures above 410C due to the hydration of the protein in their bodies. But with seawater cooling towers, the water is pumped back into the sea at around 34 to 350C (similar to the temperature of the sea in the Gulf). “A once though pumping station pumps back 100% of the water, whereas seawater cooling towers use re-cooling technology i.e. it re-circulates and is not pumped back into the sea, except for around 6 to 7% of the flow rate that is lost due to evaporation.” Sea water cooling towers are nothing new: “We supply them a lot to Europe and the Americas,” adds Al-Barazi, “where they’re used for a range of applications such as oil and gas, power, aluminium and steel, and in HVAC [heating, ventilation and air conditioning] for district cooling.” So does he envisage them being used on projects within the Gulf region? “It’s definitely a good idea. It needs some more research to explain to developers how it can work, but I think that for the future, it’s the way to go.” But sea water cooling towers are not the only product being looked at and developed in the region. Elsewhere in the market, Trane has introduced a unique HVAC maintenance service programme across the UAE in a bid to increase energy savings in buildings. Unveiled at Abu Dhabi Construct 2006, the ‘Trane Select’ initiative is designed to help developers and owners realise the benefits of maintaining reliable HVAC systems so that they provide better levels of comfort to tenants, contribute to improving office worker productivity and help to bring more business. “We estimate that 75% of a building owner’s total cost of ownership of a building is spent on energy consumption and parts replacement,” said Didier Hardouin, Trane’s vice president and business leader. “Trane Select has been designed to minimise this. As the construction boom in Abu Dhabi moves into full swing, developers should realise the benefits of maintaining efficient HVAC systems. This is based not only on choosing the right equipment, but it also involves deciding on a proper service programme to maintain long-term efficiency.” He added: “Planned maintenance ensures that systems run at top efficiency and provide up to 12% energy savings, not to mention the impact on reducing CO2 emission.” A first of its kind for the region, Trane Select includes a four-level programme: Level one offers predictive (oil analysis) and preventive (inspection visits) maintenance. Level two offers predictive and preventive maintenance including condenser coil cleaning and maintenance. Level three provides more benefits in terms of maintenance and coverage. Level four is designed for ageing products and offers the same benefits of level three, however Trane commits to maintain performance for a period of 10 additional years. Equipment replacement within the period of the agreement is also included. Available 24/7 with a guaranteed priority of intervention and free technical support, Trane Select offers developers the option of selecting the coverage best suited to their customers’ requirements. Trane Select offers multi-year agreements with installed payment to guarantee the customer better cost control. Efficient use of energy in buildings is now essential if the Gulf region is to avoid further increasing its already large investment in power generation. The energy efficiency of air conditioning systems is doubtless one of the first areas that need to be examined. Given the number of large-scale projects that are due to come on line in the next few years, it is imperative that the region’s developers pay close attention to not just the economic advantages of various cooling options, but also to the environmental considerations.||**||

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