The Pros and Cons of air-conditioning

Monday, August 27, 2007

Owner of one car, working from home, producing less that 400 kilograms of carbon dioxide, during his live confessions on global warming.

Madonna, owner of 6 cars producing 440,000 kilograms of carbon dioxide, during her Confessions tour, performs at Live Earth in London. Ain't she cute?

Are air-conditioners a necessary evil today?

Air-conditioning systems are used for both comfort and industrial applications. To that extent they are necessary, and not really per se, evil! In hot and humid climates such as India, it is really a boon. All of them increase the efficiency of living. Air-conditioning is essential for hospitals, and also a necessity for industrial processes. Having said that, these devices of comfort consume energy, and do have the potential to deplete the ozone layer and cause global warming.

However, I would like to make one thing clear. The refrigerant gases which circulate in the air-conditioning system, are in a closed system, and have the potential to cause environmental problems only if released into the atmosphere. I think people are now conscious of this, and ensure that these gases are recovered and not leaked out to the atmosphere.

Could you tell us the pros and cons of air-conditioning?

Well, the positive effects of air-conditioning are really very easy to define. Simply put, they provide they keep the human body comfortable, by providing uniform and controlled temperature and relative humidity levels in a closed space, apart from the diverse industrial, critical healthcare, and cold store applications which cannot be achieved by without air-conditioning or refrigeration, as the case may be.

In a non-air-conditioned building, you always have the option to keep the windows open. This option is not possible in an air-conditioned space, since it is a closed space. So, apart from catering to the physical comfort of the human being, air-conditioning systems also need to overcome the limitations of the closed space, as far as fresh air is concerned.

(We cannot really call it fresh air now-a-days! Rather, I think the right term would be outside air!). This controlled amount of fresh air is necessary to dilute the levels of CO2 build-up in the room, and also dilute and exhaust out other gaseous pollutants from the space.

The problem is that window-type room air-conditioners, and non-ducted type split air conditioners really do not have any facility to provide fresh air. Around 60% of the installations in India are split and room air conditioners, so it becomes important to address the issues concerning them.

In earlier models of window type room air conditioners, there used to be a facility of providing around 5 to 6 cubic feet per minute of fresh air which really is just about adequate for a couple sleeping in a bedroom at night, but is as it is totally inadequate for an office. So, it is this prime concern, that the smaller units do not have this facility to provide fresh air.

I do think that it is time that the industry paid some attention to this issue. The concept that the opening and closing of the main door provides adequate fresh really does not hold water in each and every case.

So, really, while there is no apparent current solution to this problem, unless one is ready to do a lot of customisation, its necessary to make sure that the windows of the room and office are opened every morning for at least 1/2 an hour to provide larger ductable type units, though, do have the capability of providing fresh air.

Look, fresh air is required; otherwise you are going to have a feeling of general malaise throughout the day.

Here again, there is every possibility that the fresh air damper is kept closed by the user so as to save power and energy costs. After all, every 1000 cubic feet per minute of fresh air requires around 7 tons of refrigeration to cool it down from the outside conditions to the room conditions.

An International team of researchers have recently announced that hospitals constructed in the 1950's which did not have air-conditioning but had large windows and high ceilings, had a lower rate of infection than modern hospitals, which had mechanized methods of pressurisation. This has been reported in the PLOS Medicine Journal

It not difficult to guess why all of a sudden there is so much interest in the infection issues in hospitals. It's because of the potential HN51 bird flu pandemic.

The next issue I would like to speak of is about keeping the cooling coil and the filter of the air-conditioner clean. In most cases, the filters are choked with filth, and the moist and dirty condition of the cooling coil, coupled with a clogged filter is a prime cause of all sorts of infections.

And then we have the problem of other pollutants in the air-conditioned space which we inadvertently generate, usually without our knowledge. Most offices keep volatile compounds such as disinfectants and other cleaning liquids in the pantry of an office, and the bottle containing these liquids are not usually properly corked or capped. These compounds constantly leak into the air, and their concentrations increase due to the absence of fresh air to dilute them and flush them away. I think that this, apart from the lack of fresh air, is possibly the main cause of absenteeism in Indian offices! Basically, we are speaking of a feeling of illness and a lack of energy, or even watering eyes, without being able to specifically pin-point the cause. And we then seek solutions by visiting the doctor who really may not be able to identify the actual cause, since the symptoms are so generic!

The last issue, I think which deserves attention, is that air conditioners provide air to the room in a chilled state. This chilled air should never be directed directly to an exposed part of the body, especially, and I emphasise this, to the back of the nape of the neck. Prolonged exposure of the nape of the neck to chilled air, can lead to paralysis!

I think if we are able to take care of the points that I have mentioned, we would have really eliminated those so-called "evils" of air-conditioning which are in our control.

As far as the use of safe refrigerants is concerned, there is legislation in place now, to phase out refrigerants which can potentially damage the environment.

What are the effects of refrigerants used in air-conditioners on our environment?

The effects of leaked or released refrigerants on the environment are really three-fold. (These are the known effects, by the way. there may be more about which we have no idea as yet or are unable to pinpoint).

Firstly, there is issue that CFCs, and HCFCs to a lesser extent, damage the Ozone layer. Chlorofluorocarbons and hydrochlorofluorocarbons have atoms of chlorine. This chlorine atom strips away an atom of oxygen from ozone which is a tri-atomic molecule of oxygen, turning ozone into ordinary oxygen. It's the ozone which prevents excessive amounts of ultra-violet rays to reach the earth. Excessive ultraviolet rays are damaging to all living things, and can cause melanoma, a type of skin cancer in humans, eye cataracts, weakened immune systems, reduced plant yields, damage to ocean eco systems and reduced fishing yields, adverse effects on animals and so on. So you see why it's so important to prevent the depletion of the ozone layer.

Secondly, we have the problem of global warming, which is not only linked to excessive energy usage and the production of high levels of carbon dioxide, but also to the fact that many of the newer refrigerants that are replacing the older ones, have the potential to increase global warming if released into the atmosphere. It’s really ironical, that a depleting ozone layer may actually bring about global cooling!!

Or is it that the phenomenon of global warming is merely a cyclical event?

"Do rising atmospheric CO2 concentrations cause increasing global temperatures, or could it be the other way around? This is one of the questions being debated today. One thing is certain-- earth's climate has been warming and cooling on it's own for at least the last 400,000 years, as the data below show".

So, you see that merely substituting new refrigerants may not be necessarily the only path to tread. We must look at more radical ideas, or combine modern thinking, with the retro concepts that we threw away long back. Some of these are, of course that of using ammonia as a refrigerant, and the incorporation of natural cooling techniques.

We have a global energy crisis on our hands and soon we will not have a choice about what we do. Government legislation is now in place and the heat transfer coefficients of building construction is now defined by ECBC, The Energy Code Building Council.

Thirdly, while the CFCs and HCFCs were really harmless to human health, (and that's why they have been extensively used in propellants and aerosols. Till the 1980s, aerosols really contributed to over 40% of the release of these gases in the environment), the newer refrigerants, especially the transient refrigerant R-123, have the potential to cause liver cancer under prolonged exposure, as documented by The Lancet.

(The earlier refrigerants used in AC's (e.g. CFC's & HCFCs) were not toxic at any dilution but had a molecule of chlorine, which had an affinity to radical oxygen and when leaked this was not good for the environment & ozone layer. Hence newer refrigerants were created like R123, R134, R-22, R-13, R-11 which have no chlorine in them but which had other side effects. According to the Lancet Journal R 123 is found to have caused cirrhosis of the liver in plant operators. R 134 is also found to have some level of toxicity if leaked. R 22 is used in medium & small AC's, R 11in car AC's & R11 & R13 are also used in aerosols and are responsible in some in some way for the increase in global warming. However as per the Montreal protocol R 22 can be used by the developing countries upto 2030. (The effects if any, of newer refrigerants like R407C will be known only after a certain period of years.)

These new complications have lead to a worldwide debate whether or not to start re-using ammonia a very effective refrigerant, which was also completely safe for the environment and which though toxic if leaked could easily be sensed by the olfactory system of the nose.

The phenomenon of "Sick Building Syndrome" is usually caused by gaseous elements that exist in an office environment which are let out by various materials, paints & furnishings used in modern offices. Melamine, Pesticides & phenyl bottles with loosely fitted caps are some of the harmful materials used in modern offices, coupled with the fact that inadequate or even nonexistent fresh air levels are maintained in the space.

How can we run our air-conditioners most effectively thus causing least damage to the environment?

Of course, a prime factor would be to ensure that the air-conditioning system is sized correctly. The unfortunate situation is that 30-40% of all installations are oversized, due to current methods of load calculation, and because of not taking into account factors such as external window shading.

Newer methods of load calculation, such as hourly load calculations are now being developed indigenously, and are on the verge of being available at reasonable cost.

Really, using an air-conditioning system, per se, does not damage the environment! It does consume energy, and so in that way it does have an indirect effect on the environment, since the production of energy may have been through a non-renewable source, such as nuclear power, or by the burning of coal.

So having understood that, it’s pretty easy to figure out that we must promote the use of renewable energy sources such as hydronic, wind, and solar energy. Once again, this is not a choice available to the general user.

What can be done, however, is to ensure that building construction is carried out in such a manner, so as to make it "green". See, "green" is a colour that happens to reflect a natural environment. So, by constructing buildings, which make maximum use of any sort of free-cooling, and are constructed using materials and constructions which have low heat transfer conductance values, and say, by ensuring some sort of treatment to the roof, and yes, making sure that glass and glazing areas are not only kept to the minimum, but are adequately shaded externally to provide substantial shading to the window to reduce the heat gains, and by planting a lot of trees, for the same purpose, to provide the building with a shade, and maybe, by using some high-tech paints on walls and roofs, paints which have a high emissivity to prevent absorption of heat, then we would have achieved low values of building fabric conductance and therefore reduced the air-conditioning load.

As far as the internal loads are considered, the use of high efficiency low energy Compact Fluorescent Lamps and energy efficient computer monitors and CPUs will also bring down the air-conditioning loads. (Looks like we are supposed to ignore the effect of mercury, which is present in CFL lamps, on the environment when the lamps are disposed!)

In larger installations, metering the right amount of fresh air, depending on the level of carbon dioxide in the space, would help reduce fresh air loads, when peak occupancy does not exist. The use of daylighting and maybe, if the possibility exists, of pre-cooling the fresh air naturally, as has been done in the CII-_Godrej Green Business Centre in Hyderabad, would also bring down the air-conditioning loads.

As far as the temperature is concerned, maintain room temperatures between 24 and 25 deg C, and even higher temperatures are comfortable, in very hot exterior environments, such as the interiors.

Of course, perception of comfort varies from culture to culture and also depend on the clothing that the person is wearing and the metabolic rate. In our quest for comfort we should not set the air conditioner at a temperature lower than required as for every one degree that we lower the temperature we are using 15 to 20% more energy. Running ceiling fans at slow speed while maintaining temperatures at even as high as 27 degrees C, is comfortable! I can say that from first hand experience, as I conduct training in HVAC, and there seems to be consensus amongst the trainees, that this is indeed so!

A very good energy-saving solution, apart from switching off the air-conditioners during lunchtime, and say, ½ an hour before office closure. This simple action over an 8 hour period, can itself bring about a reduction of energy consumption of 10%!

Can you tell us some alternate cooling techniques?

India has a heritage of naturally cooled buildings, from the sheetal Minar to the Taj Mahal. These naturally cooled buildings make use of some natural principles of cooling. A few of the common ones are, evaporative cooling, which is the phenomenon that the dry bulb temperature of the air, the one you measure by a thermometer, is lowered without using any energy, but merely by passing the air through a spray of water. We have all seen this concept used in desert coolers which use this evaporative cooling technique to cool the air. The same principle should be applied to buildings, wherever and whenever possible, especially in the arid and hot parts of the country.

The other natural principle that has been used for thousands of years to keep buildings naturally cooled is the fact that if we remove the heat from the building structure itself, the air within will remain cool. This is how the Taj Mahal is cooled, as it is built over a huge block of basaltic rock, which is cooled all throughout winter by the chilled waters of the Yamuna, and during summer, the heat from the structure of the Taj flows into this chilled rock, thereby keeping the Taj cool!! I think its is due to this particular reason that the Taj should figure in the Top Ten Wonders of the world, and it foretells and shows the way to energy conservation!

The CII Godrej Green Business Centre makes use the principal of pre-cooling large cavity walls with fresh air at night, and then, during the day, the warm ambient air which is sucked though the cooled mass, is pre-cooled, before entering the space or the air handler. The CII Green building Centre has been given the prestigious "Platinum" rating by LEED, the "Leadership in Energy and Environmental Design", which provides guidelines based on a point system for evaluating the "greenness" of a building.

An Indian chapter of LEED has also been incorporated recently, so that practical standards for Green Buildings could be set as is suitable for the warm and humid climate of India, and taking into account local building techniques and materials.

Recently, on 27th May, the ECBC, that is the Energy Conservation Building Code has been released by BEE, the Bureau of energy Efficiency, which provides guidelines to states, for all aspects of building construction to reduce the energy usage of large buildings.

The ICICI Bank Towers located in Bandra - Kurla complex, has also incorporated green building concepts.

What according to you is the future of the Air conditioning systems?

I think that the future of air-conditioning lies in an integration of everything that I have spoken on, from the construction of Green buildings, to using renewable energy sources, the use of refrigerants which do not damage the environment, and the integration of natural cooling methods. If we do not do something radical, I'm afraid that we are leaving a terrible legacy for our children to deal with. What’s more so, mere legislation cannot be a solution to all the problems that we face today. It is the action by the individual, by his inner sense of responsibility that can bring about a sustainable infrastructure, and in balance with the natural environment. We will need to sacrifice some of our pleasures and comforts, and if we do that voluntarily, well and good, otherwise the laws of nature will ensure it at some time or the other.

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