An American colleague recently described evaporative cooling as “swamp technology”, a quaint term which, according to Wikipedia, was coined as a reaction to the odour of algae in early units.
This got us thinking about whether there were any other issues or myths that put people off the technology. In this country we’re blessed with a temperate climate so for many applications and for much of the year the cost and complexity of a full air conditioning system is not necessary and a simple, low cost evaporative cooling system may be a better solution.
Why is evaporative cooling not more popular? Could it be the “swamp technology” attitude and concerns that it may not be up to today’s expectations?
5 common concerns that shouldn’t keep you away from evaporative cooling:
1) Humidity
Yes, the air leaving an evaporative cooler has a higher humidity than the incoming air, but once this air reaches the room it quickly mixes and absorbs heat, normally bringing the relative humidity back down to acceptable levels. As long as the room humidity is not marginal prior to cooling and the incoming air is fresh, not recirculated, the increase in humidity is unimportant compared to the benefit of the cooling.
2) Legionella
In this day and age any system storing and circulating water is questioned. Evaporative coolers like the Colt Coolstream are carefully designed to avoid legionella risk. Water is kept at ambient temperature, not the elevated temperatures that lead to fast colonisation, and regular automatic drain, dry and refill cycles limit available colonisation time. A version of Coolstream has been independently certified by VDI to VDI 6022 to guarantee safety.
3) Algae
The constant circulation of the stored water and the drain, dry, and refill cycles ensure algae are not a problem.
4) Lime scale
Formation of lime scale depends on local water hardness, but there are easy solutions. For example, Coolstream uses generously sized openings to minimise the effect of lime scale, the controls ensure that the pump is kept going most of the time, and the system has much more water in circulation than what is needed for evaporation. In very hard water areas, water softening may be beneficial. Lime scale may eventually clog the paper heat transfer elements, but these should be subject to planned replacement well before this becomes a problem.
5) Maintenance
On Coolstream, all controls, including water hygiene, is automatic. The only planned maintenance required is a bi-annual (spring and autumn) check over and paper element replacement at typically 2-4 year intervals.
Nothing too nasty there then, compared to the advantages of having cooled fresh air circulating through a building, keeping it fresh and healthy and aiding productivity.
For a more detailed analysis of these concerns, you can download and read our free white paper, 'The facts about evaporative cooling'.
We also have a new white paper discussing the ventilation solutions for overheated corridors in residential buildings, which explores the use of evaporative cooling as part of a smoke control system.
Paul Compton is Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.
