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Reiner Boehme, VP––Engineering, Inter-Continental Hotels
and Resorts
Source:
Hotels and Restaurants Network Vol.VI Issue 4
Are
you aware of your country's regulations covering ozone
depleting refrigerants and the deadlines for phasing them out?
What are the priorities, options and the most economic
alternatives? Above all, why should you be taking action?
Apart from the fact that equipment using CFCs will
ultimately reduce the value of your property the phase out of
CFCs is being driven by:
1.National
legislation following various international agreements (i.e.
the
montreal Protocol)
2.The
future availability and cost of CFCs and HCFCs
3.Operating
and maintenance costs of existing equipment
4.Sound
environmental practice
What
is the problem?
For over 60 years, CFC refrigerants have been the life
blood of refrigeration and air conditioning equipment.
However, it has been proved that CFCs
(chlorofluorocarbon), HCFCs (hydrochlorofluorocarbon)
collectively know as ODS (ozone depleting substances) are
contributing to the depleting of the ozone layer and to
warming of the earth's atmosphere.
Evidence points to these manmade chlorine and bromine
compounds as being responsible for the 'ozone holes' – areas
of reduced stratospheric ozone concentration – over the
polar regions. Recent scientific findings have shown that
significant ozone depletion is also apparent over large areas
of the northern and southern hemispheres.
The ozone layer forms a protective shield around the
globe, screening us from ultraviolet (UV) light. Too much can
cause health problems such as skin cancer and adversely
affects the growth of biological life.
These
chlorine compounds also contribute to the 'greenhouse' effect
because they absorb infra-red radiation from the earth's
surface. This leads to a higher temperature on earth which is
being blamed for more rapid melting of ice in the polar
regions and glaciers. This contributes to a rise in the sea
level which, in turn, causes further disruption to weather
patterns.
Because of their lifespan, even if we stopped releasing
CFCs into the atmosphere today, their destructive work would
continue for many decades.
International
agreements for a CFC-free future
Concern about ozone depletion led to the Montreal
Protocol and the copenhagen, Vienna and London Amendments. The
Montreal Protocol specifies the phase out of ODS manufacture
and provides a timetable for its achievement.
The latest version has been signed by 134 countries.
Developing nations have a ten year grace period under Article
5. This includes 53 countries and 35 are listed as temporarily
operating under this Article. The gradual phase out eliminates
CFCs (and HCFCs over a longer period due to their lower
environmental impact and the amount of equipment currently in
use).
Global warming was the subject of the December 1997
summit in Kyoto. No change has yet been made to the protocol's
phase out dates since then. (This story was written in 1998).
Political and economic pressures and the importance
each country places on the environment are determining factors
in the phase out process. Many developed countries have set
earlier phase out. However, between 1992 and 1996 India
tripled its CFC productions and China increased it six-fold.
Taking R-22 for example the US, Australia, India,
Japan, Brazil, Venezuela, Egypt and others are in dispute with
the European Union, which has set tighter schedules. Phase out
in the EU is currently set for 2015 compared ;with 2030, and
production ;of equipment larger than 150 kw motor size is
prohibited after 2000.
Refrigerants
are only a part of the story
When
evaluating alternative refrigerants to CFCs, it is essential
to determine the environmental impact of the equipment itself.
A major indirect contributor to global warming are the carbon
dioxide emissions from the energy used to operate the
equipment. In most case, these indirect greenhouse gas
emissions which result form refrigerant released to the
atmosphere from leaks or losses during equipment servicing.
The total combined effect of direct and indirect
contributions to global warming is known as the total
equivalent warming impact (TEWI). In new equipment, the direct
contribution of the refrigerants (through leaks) accounts for
only 2% and the indirect for 98% of the total TEWI.
By practising containment, the global warming potential
(GWP) of refrigerants is negligible. For instance, a machine
charges with R-134a but with a leak rate of only 0.1% has a
far lower TEWI than an absorption chiller using a zero GWP
refrigerant.
Refrigerants,
alternatives and future options
Unfortunately, there is no all purpose refrigerant and
there is much confusion in the market. Many alternatives are
mixtures which appear under different, often meaningless,
trade names. For example, R-407C is traded by Dupont as
AC9000, while ICI calls it Klea 66, a mixture of R-32, 125 and
134a in the ratio 23/25/52.
Some refrigerants were only intermediate solutions and
will be discontinued, such as R-123. It is not always easy to
tell which replacements are HCFCs or HFCs.
So
what is the best Choice?
Current options are limited by both the chemistry and
the application. The main criteria in selecting refrigerants
are their :
•
Chemical and physical behavior (stability, corrosivity,
performance, pressure etc.)
•
Efficiency,
•
Safety (toxicity, asphysiation, flammability)
•
Availability and costs,
•
Environmental impact-ozone depleting potential (ODP)
and global warming
potential (GWP).
Any refrigerant selected for long-term use must support and
overall system that is safe, economically and environmentally
sound. It must reflect
considerations such as new technologies, waste minimisation,
containment, energy efficiency and consumer protection R-123
and R-134 a are single compounds (R 100 series). Mixtures of
between two and four refrigerants are divided into two major
groups.
•
•
Blends which behave as a single refrigerant (assigned
the 500 series number).
•
•
The 400 series –– those which evaporate and
condense at different temperatures. For this reason they
cannot be used in flooded chillers, but are acceptable in
reciprocating and screw type chillers or other direct
equipment. The majority are blends of various refrigerants,
some of which have flammable or toxic properties. Capital
letters A,B, or C stand for different proportions of the same
blends. Standard ASHRAE 34 provides a uniform rating of
refrigerants for toxicity and flammability.
Where
is the air conditioning industry moving?
The first step is containment refrigerant. Which does
not leak does no harm.
Leak rates form low pressure negative chillers have
been improved from
15% to 1-2% against previous models.
Hermetically sealed positive pressure chillers leak
only 0.1% compared with 8% in older equipment.
The top four chiller manufactures have moved to
chlorine free R-134a, replacing R12.
R-134a requires ester-oil for lubrication, which is
more expensive and very sensitive to moisture. R-134a is also
used in refrigerators, rooftop units and refrigeration
compressors.
Despite its extensive anticipated use, it is estimated
that the contribution of R-134a is also used in refrigerators,
rooftop units and refrigeration compressors.
Despite its extensive anticipated use, it is estimated
that the contribution of R-134a to global warming will be less
than 1% by 2020. In addition to their R-134a products only
Trane and York build R-123 centrifugal chillers, replacing
R-11. Trane manufactures R-123 machines in the US, while their
European branch does not support this route.
When leaks ocur, only 10 ppm R-123 are permitted in
plant rooms versus 1000 ppm for R-134a because of R-123's
slight toxicity. This requires expensive sensors, ventilation
and containment.
R-22 is still very popular and most manufacturers offer
the entire equipment range. However, its phase out may be
accelerated (the EC, for example, is considering legislation
to prohibit use CFCs for maintaining existing systems and
HCFCs in new systems).
Blends, such as R-404A, R-410A and 410B, R-407C etc.
are most widely used. Occasional problems with oil degradation
are being addressed. Generally, the industry is waiting for
better replacements.
Hydrocarbons such as Butane, Propane, Propylene and
Isobutane are applied in small refrigeration equipment
(typically 150 grams and larger industrial applications, but
are limited in their commercial use. They are goods choice
where their is not risk due to their flammability and where
local codes permit their use. Ammonia poses a health risk and
sulphur dioxide is toxic.
New absorption chillers are more energy-efficient than
older designs. Whenever waste heat is available, such as in
co-generation, or where gas is cheaper than electricity, they
are preferable.
Implications
of the Montreal Protocol
The phase out of CFCs and HCFCs has considerable impact
on the hotel industry.
A survey conducted at 87 Inter-Continental hotels
revealed that we have over 4500 pieces of
equipment––mostly chillers, miscellaneous air conditioning
equipment, cold rooms and freezers, ice making machines,
refrigerators, fire extinguishers and the like. The most
widely used refrigerants are R011, R-12, R-22 and occasionally
R-502 except where water is used as refrigerant in absorption
chillers. In a few years' time, an entire refrigerant charge
of R-11 may cost $ 20,000 where it previously cost $ 4,000.
Chiller manufacturers have dramatically improved the
efficiency of their equipment, which justifies replacement of
economic reasons alone, especially when operated throughout
the year.
With some simple and sound management practices it will
be possible to keep future costs to a minimum.
Refrigerant
management in hotels-contain, retrofit or replace?
containment
= maintenance
The Montreal Protocol phases out production of CFC
refrigerants but (currently) allows the use of stockpiled and
recycled CFCs. Equipment can be operated for as long as
refrigerant is available (and permitted in hour country). If
you are able to reduce your losses to 2% rather than 8-15%, a
stock of 150 kg will last 15 years for a typical 500 ton
chiller.
So, the most important step is to minimise leakage from
equipment immediately.
1.
Obtain your local codes and regulations.
2.
Implement proper procedures for the handling of
refrigerants, equipment repairs, recovery techniques,
disposal, and storage. Train your refrigerant technicians.
Purchase refrigerant recovery and recycling equipment designed
for use with multiple CFC and HCFC refrigerants. Recyled
refrigerants could be stockpiled.
3.
Install high efficiency purge units on low pressure
chillers only (R11) to reduce excessive losses during normal
operation.
4.
Check for leaks or install a refrigerant leak detection
device in plant rooms.
5.
Prevent the breakdown or possible loss of an entire
chiller. Carry out occasional Eddy-current tests on chiller
condenser tubes, especially if there is a history of
corrosion, deposits or even plugged tubes. When weak tubes
fail, you not only lose the entire refrigerant charge but also
have a major repair and possibly no satisfactory air
conditioning for some time.
Retrofit
Smaller items of equipment should be retrofitted an
converted to non-chlorine based refrigerants whenever major
repairs are due. Depending on the phase out dates of your
country you may have to speed up converting R-11 and R-12
equipment––even if it is i good condition.
Large chillers can be retrofitted, but generally lose
capacity and efficiency.
Depending on their age and condition, retrofitting is
generally not recommended as the costs may be 40-100% of that
for new equipment and you are still left with the old
machine.
For chillers which are less than ten years old, the
best option is containment, and the next best is conversion.
Prior to converting, check with the original manufacturer.
Replacement
This is the most expensive alternative, but the most
economic and environmentally friendly in the long run.
Chillers manufactured today are up to 30-40% more energy
efficient than those of the past.
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