Leave air-con out in the cold
By Karen Charlesworth Friday, 19 September 2008
In the battle to cut energy costs and reduce environmental impact in the manufacturing sector, air-conditioning is rapidly coming to look like a big no-no. For a start, it calls for the manufacture of refrigerants, one of the world's earliest environmental issues, and the chief culprits in the - still - growing hole in the ozone layer.
Air-conditioning is expensive to run at the best of times, and in these days of soaring energy prices, ‘expensive’ has become ‘exorbitant’. And add to all that the difficult to inforce fact that, to work at its most efficient, air-conditioning requires all the windows and doors in a building to be kept firmly shut at all times. Even if it’s a blazing hot day outside, your staff must languish behind an impenetrable sheet of glass: and the solar gain causes a mini-greenhouse effect, meaning the air-con must work harder and consume more energy to keep the room cool.
So what would you say to a cooling technology that costs less to buy than air-conditioning? Has around 10% of the running costs of air-conditioning? That uses no refrigerants? And which, far from requiring windows and doors to be closed, actually functioned better if they were open? Well, dream no more, evaporative cooling is coming to the print industry.
The technology that underpins evaporative cooling is simple, inexpensive and as old as the hills – one of the earliest documented installations sits in a 16th-century Indian palace, where 400 years ago a water curtain was gently fanned by servants to disperse tiny droplets into the air. Latter-day applications of the science involve motor-driven fans and special synthetic pads saturated with water (see page 29 for more on this) but the basic physics remains exactly the same.
If the physics is simple, so is the maths. Installations of evaporative cooling in the print industry are currently few and far between, but similar-scale installations in other types of manufacturing site indicate that, dependent on the complexity of the ducting and distribution systems, the capital cost of an evaporative cooling system can be as little as 40% of a comparable air-conditioning system. Help is also at hand for would-be evaporative cooling users: the government’s Carbon Trust initiative, dedicated to reducing the carbon footprint of UK industry, has a scheme specifically targeted at SMEs giving an interest-free loan to cover up to 100% of the capital cost of a system for a specified period of ROI.
More simple maths: even complex evaporative cooling installations garner massive savings in running cost over a comparable air-conditioning system. Industry environmental technologies JS Humidifiers reckons that running costs come in at anywhere between 10% and 20% of the running costs of air-conditioning. It’s a huge benefit to users, especially when you think that the cost of energy is going through the roof at the moment. The savings get bigger every month, says JS’s director of new products Mike Verney.
Evaporative cooling has a particular synergy with heavy industry, as Alan Beresford, managing director of Ecocooling, explains: The technology is perfect for cooling large industrial plant rooms, such as pressrooms and bindery departments. These are areas that you couldn’t previously have cooled with air-conditioning: they’re too big, and the running costs would have been prohibitive.
Beresford has put his money where his mouth is: until six years ago he was St Ives Group’s general factory manager, but when he came across evaporative cooling – then in its infancy as an applied environmental cooling technology – he gave up his day job, designed his own cooler and set up a licence with a Chinese manufacturer.
Beresford has now installed hundreds of Ecocooling products in hospitals, schools and factories across the world.
Evaporative cooling has had a major hurdle to overcome in reaching its current developed state: the problem of bacteria proliferation – very specifically, the bacterium Legionella pneumophila, which causes legionnaire’s disease. The bacteria, found naturally in environmental water sources such as rivers and lakes, tend to breed in the reservoirs of air-conditioning systems, and are then efficiently distributed around a building through the air-conditioning system’s ducts. The same difficulty potentially exists for evaporative coolers too, but as Alan Beresford explains, rather than zap the bacteria with biocides – the standard approach for disinfecting air-con systems – his own Ecocooling systems have designed out the problem so it never occurs in the first place. He adds: We keep the water temperature low, we don’t have any stagnant water in tanks or reservoirs, and we don’t create droplets when we distribute the cooled air around the system.
Another benefit of installing an evaporative cooling system over air-conditioning, that also works specifically to the advantage of printers, is the fact that as a side-effect, they introduce a greater level of humidity into the local environment. Air-conditioners tend to dry out the air in a factory, and print hates that, says Beresford. The paper gets dry and brittle, and it doesn’t run well through the press. In extreme conditions it can even cause colour shift because the dimensional stability is so badly affected by dry air. But the real pot of gold with evaporative cooling’s humidification effect, he says, is with static electricity. If the relative humidity in a print factory drops below 30-40%, the static doesn’t run off the paper as it should, because there isn’t enough moisture in the air to act as a conductor. The sheets start to stick together and you have to slow machines down, and that’s particularly true with thin papers and laminates. A well-planned evaporative cooling system, as well as keeping the temperature down and the working environment pleasant and fresh, will have the effect of balancing humidity. For this reason, evaporative cooling systems can be controlled either by thermostats or by humidistats, or by both, or by either or both in conjunction with a timer, says JS’s Verney.
With all this good stuff, surely there must be a hitch? There is, but it’s a small one: with evaporative cooling, the temperature inside the factory is intimately related to the temperature outside the factory. The colder it is outside, the cooler it will be inside; likewise, on a blazing hot summer’s day, the temperature inside will be correspondingly warmer. In this, evaporative cooling differs from air-conditioning, which can maintain a constant temperature even when the differential between inside and outside is at its greatest, says JS’s Verney.
HOW IT WORKS - EVAPORATIVE COOLING
Evaporative cooling is a type of heat exchange: it uses the principle of evaporation to exchange heat in an air stream.
A typical evaporative cooling system brings water into a cooler from a mains water supply, and a circulation pump moves the water to the top of the unit. Water is then circulated over a series of filter pads in a continual motion; these become saturated with water. Air is pushed through the pads by a fan and the evaporative effect from the water’s dispersal causes the cooling effect, which gives a stream of cool air out the other side of the pad.
The cool air is then ducted around the building by fans.
In the absence of refrigerants, the system achieves a typical temperature reduction of between two and 10 degrees over the outside temperature. The UK has an advantage over hotter countries – the temperature outside, which is cool for most of the year. This means the typical evaporative cooling system can keep a building similarly cool without massive energy expenditure.
CASE STUDY - MCKENZIE CLARK
Large-format digital specialist McKenzie Clark moved into its new factory, based in Peckham, south-east London, in April 2007. Managing director Graham Clark was keen to make an environmental statement with the new factory’s design and specification, and when heating contractor Harry Taylor showed him a cooling technology that was greener, cleaner and cheaper than air-conditioning, in his own words: I was rather keen to find out more.
McKenzie Clark applied for assistance from the Carbon Trust, which gave an interest-free loan for 70% of the evaporative cooling system’s capital cost, and the system was installed throughout the Peckham site’s offices and factory spaces: two floors totalling almost 1,500m2.
Clark is very impressed with his evaporative cooling system. I think printers should be looking at this as an alternative to air-conditioning, he says. The environment it creates is much nicer to work in, especially because you can have the windows open. It’s good for the staff, it’s good for the kit, and it’s much better for the environment. If it has a downside, I’d say it’s in getting used to the fact that if you alter the thermostat, it takes 15-20 minutes to change, whereas if you’ve got air-con the change is more or less instant. But that’s a small disadvantage in the face of the overall advantages.
The installation has so far netted savings for McKenzie Clark that its MD considers impressive. Our annual energy saving over a similar air-conditioning installation equates to just over £9,000 plus VAT, and that’s at 2007 energy prices, he says. Plus, we avoid putting into the atmosphere 36 tonnes of carbon a year. It’s really a win-win situation all round.
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