INCORPORATING COLD CHAIN
FEATURE
Bitzer refrigerant report: Part 2
Published with permission of Bitzer
Stratospheric ozone depletion as well as atmospheric greenhouse effect due to refrigerant emissions have
led to drastic changes in refrigeration and air conditioning technologies since the beginning of the 1990s.
For reference to earlier information, please see Part 1 published in the previous issue of Cold Link Africa.
A
method of calculation has been
developed to judge the influence
upon the global warming effect
for the operation of individual
refrigeration plants (TEWI = Total
Equivalent Warming Impact).
ENVIRONMENTAL IMPACT: GLOBAL
WARMING AND TEWI FACTOR
All halocarbon refrigerants (including
the non-chlorinated HFCs) belong to the
category of greenhouse gases.
An emission of these substances
contributes to the global warming effect.
The influence is however much greater
in comparison to CO 2
, which is the main
greenhouse gas in the atmosphere (in
addition to water vapour). Based on a time
horizon of 100 years, the emission from 1kg
R134a is, for example, roughly equivalent to
1430 kg of CO 2
(GWP = 1430).
Thus, the reduction of refrigerant losses
must be one of the main tasks for the
future. On the other hand, the major
contributor to a refrigeration plant’s
Great effort is taken worldwide to reduce
greenhouse gas emissions, and legal
regulations have partly been developed
already. Since 2007, the "Regulation on
certain fluorinated greenhouse gases" –
which also defines stringent requirements
for refrigeration and air conditioning systems
– has become valid for the EU. Meanwhile,
the revised Regulation No. 517/2014 entered
into force and has to be applied since
January 2015.
ECO-EFFICIENCY
An assessment based on the specific TEWI
value takes into account the effects of
global warming during the operating period
of a refrigeration, air conditioning or heat
pump installation. However, not the entire
ecological and economical aspects are
considered. But apart from ecological
aspects, economical aspects are highly
significant when evaluating technologies
and making investment decisions.
With technical systems, the reduction
of environmental impact frequently
involves high costs, whereas low costs
often have increased ecological
consequences. For most companies, the
investment costs are decisive, whereas
they are often neglected during
discussions about minimising ecological
problems. For the purpose of a more
objective assessment, studies were
presented in 2005 and 2010, using the
example of supermarket refrigeration
plants to describe a concept for
evaluating Eco-Efficiency.
It is based on the relationship between
added value (a product's economic value)
global warming effect is the (indirect) CO 2
emission caused by energy generation.
Based on the high percentage of fossil
fuels used in power stations, the average
European CO 2
release is around 0.45kg
per kWh of electrical energy. This results in
a significant greenhouse effect over the
lifetime of the plant.
Due to a deciding proportion of the
total balance, there is not only a need for
alternative refrigerants with a favourable
(thermodynamic) energy balance, but
an increase in demand for highly efficient
compressors and associated equipment as
well as optimised system components and
system control.
When various compressor designs are
compared, the difference of indirect CO 2
emission (due to the energy requirement)
can have a larger influence upon the total
effect than the refrigerant losses. A usual
formula is shown in Figure 1. The TEWI factor
can be calculated and the various areas of
influence are correspondingly separated.
An additional example is shown in
Figure 2 (medium temperature with
R134a) shows TEWI values with various
refrigerant charges, leakage losses and
energy consumptions. This example is
simplified based on an overall leak rate as
a percentage of the refrigerant charge.
The actual values vary strongly, so that the
potential risk of individually constructed
systems and extensively branched plants is
especially high.
COLD LINK AFRICA • September 2020 www.coldlinkafrica.co.za 29