Cooling a large building such as an airport traditionally requires strong air conditioning, which is costly and energy inefficient. Future Airport talks to Rex Lehmann, co-founder and CEO of SkyCool, about how his company provides a simple, low-maintenance and high-tech solution to this problem.
Rex Lehmann: The sun's radiation is strongest when it is high in the sky, as it is then radiating through the least amount of atmosphere. Of all the surfaces subjected to this incoming thermal radiation, a bare metal (whether galvanised or painted) surface typically absorbs the bulk of the solar load, which will usually heat it to more than twice the local air temperature. That is to say, on a 30°C day, the outer roof surface will typically reach more than 60°C. Our applicators have actually measured roofs they have been working on at 87°C.
As airport terminal roofs are typically very large, they present huge solar heat absorbance surfaces in warmer climates. This creates such a high demand for interior cooling that the air conditioning is the largest single user of electricity within the terminal. Therefore, anything that can be done to reduce the outer roof heating can have a significant impact on the cooling load and operational costs of the building.
Prior to cool-roof coatings, there were no means of preventing roofing metal from superheating. Other measures - like insulation, roofing vents (active or passive), sloping the roof away from the direct overhead sun and standard white paint - would be employed to minimise the effects.
The primary method of rendering the interior thermally safe and usable was - and still is - very costly mechanical cooling. What many people don't realise is that cooling an interior by just 1°C takes three to five times more energy than is needed to heat it. Thus, mechanical cooling places extraordinary demands on energy usage, resulting in high costs and CO2 generation.
How are SkyCool coatings maintained, and how are they safeguarded against damage?
A key benefit of SkyCool is that it is an 'install and forget' coating with no maintenance required. Tested to world-standard UV resistance, it was found that there is no degradation from tropical-strength UV exposure for the equivalent of 25 years. Also, recent product developments have enhanced dirt-repulsion capabilities such that light rain or even just wind will cause any atmospheric dirt to wash (or blow) off. One major property-owner found that even though its large roof was in a very hot and dirty region, close to a large iron ore loading port, it retained its thermal properties despite the build-up of red dust.
In addition to copious technical data from a number of universities, actual field data from multiproperty-owning SkyCool users has established a robust expectation of savings from buildings in the hot tropics to the temperate south of Australia. All measurements taken by the users and their technicians included several key factors:
The overall result was a 42% annual decrease in air conditioning energy usage, or an average reduction of 62kWh/m² of roof space a year. In Australia, where commercial electricity supply is negotiated, this has resulted in an average return on investment within 2.2 years (much of that calculated on earlier lower prices of power).
Client feedback has been enthusiastically positive. Many have pointed out benefits beyond direct power saving. Melbourne Airport, for instance, advised us that our restoration and coating of a 40-year-old concourse roof (a small part of the expanded modern terminal) saved it capital works in excess of $1.5 million within five years. The same concourse was able to shut down some 16 auxiliary air-conditioning units that were made redundant as a result of SkyCool's innate cooling capacity.
Other clients have also saved considerable roof-repair costs in addition to energy savings. Because of its long-term resistance to airborne contaminants, SkyCool can add 25 years to the life of even an aged roof.
Also, due to the robust acrylic finish, many users have enjoyed the elimination of hard-to-find roof leaks. SkyCool being applied to a thickness of 1/3mm will block small leakage within a roof surface; larger holes have also been patched purely with SkyCool.
Airports are obviously very sensitive to rooftop spray-painting works. Melbourne Airport, for example, required testing to ensure aircraft at the gate lounges would not be affected. It then determined that due to SkyCool's water-based, fast-drying formulation and on-site testing, there would be no disruption to terminal activity.
The formulation was thoroughly examined to ensure that there was no VOC or other constituents during application that might affect users of the terminal. SkyCool is odourless and non-hazardous.
The overall benefit described by Melbourne Airport in its TV report was that SkyCool reduced peak cooling demand from four water-cooled units operating at 100% capacity to only three units operating at 80% capacity. This was in addition to shutting down the 16 auxiliary units previously mentioned. In a case study presented to Airports Council International, Melbourne Airport also reported saving the equivalent of 40,000t of greenhouse gasses in the 18 months following the SkyCool application.
SkyCool is currently working with two universities to solidify its leadership in this important global market.
Financed by a S$1-million grant, the Nanyang University of Singapore has been developing specialised nanoparticles to imbed within a SkyCool coating, which will enhance its current dirt-repulsion properties and optimise it for the wet tropics. Excellent results are starting to be deployed in South East Asia.
With 50% funding from the Australian Government, the University of Technology Sydney is researching how to incorporate the best possible science from its laboratory discoveries into SkyCool so that the technology can be used on a global commercial basis. One of its key motivations is that when widely adopted, this technology will result in substantial reductions in fossil fuel energy generation without the current high cost of alternative energy, simply by reducing the need for power in the built environment.