Back to basics
ANDREW PERKS
Andrew Perks is a subject expert in ammonia refrigeration. Since undertaking his apprenticeship in
Glasgow in the 1960s he has held positions of contracts engineer, project engineer, refrigeration design
engineer, company director for a refrigeration contracting company and eventually owning his own
contracting company and low temperature cold store. He is now involved in adding skills to the ammonia
industry, is merSETA accredited and has written a variety of unit standards for SAQA that define the
levels to be achieved in training in our industry.
HOW TO COPE
IN THESE DIFFICULT TIMES
CONTINUED
By Andrew Perks
Not too long ago it really was all doom and gloom, but suddenly
we had no more power cuts and everything was surging ahead.
But don’t get too comfortable…
T
he outcome of this year’s election will have a significant
impact on the future of South Africa; let’s all work
together to make a difference.
However, let’s not fool ourselves: power and water
problems are here to stay.
I was at a South African Institute of Refrigeration and Air
Conditioning (SAIRAC) meeting during March, presented by
Bitzer, where some significant statistics were tabled. I have
mentioned before that the cooling industry accounts for a
large proportion of the power usage in the world – a figure
of some 17% was spoken of. That is a large portion when you
think that the requirement for cooling is increasing rapidly as
we have an increase in the global population.
India is set to overtake China as the most populated country
in the world but they have a largely ineffective cold chain
with thousands of kilograms of food being regularly wasted
and dumped due to a lack of cooling facilities. The estimated
increase in power demand to keep pace with rising world
population is between five and eight percent. We are seeing the
same trends in South Africa. However, some projects are being
put on hold due to the lack of services availability.
So, the industry needs to look at power savings
and increasing efficiencies. To get back to the Bitzer
presentation, it was all about how we can go about
increasing efficiency and operating more effectively. It is in
our interests that we reduce the power usage not only to
conserve our natural resources, but also to save operating
expenses. Eskom is currently looking at tariff increases of
9.41%, a bit more respectable than the 15% they wanted.
Think about how that affects the cost of cooling, which will
eventually be passed on to consumers.
www.hvacronline.co.za
So, now we need to look at what we as an industry do about it.
I know you will all say, “There he goes again about his precious
ammonia,” but it is a fact that you get more cooling for your
operational costs using ammonia than the other current
refrigerants. Ammonia as a common refrigerant is the cheapest
around, but not the cheapest to install. That is a given.
Ammonia plants are expected to last conservatively for
30 years, and if properly designed and maintained, 50 years
is attainable. Normally new trends and improved efficiencies
are the current major reason why plants are upgraded or
replaced. Not so with the “Freon” (synthetic refrigerant)
industry. It is generally accepted that a 10-year period is the
norm. Maintenance and proper operational consideration
will improve on this but over the long term, where initial
costs are not the prime concern, ammonia is by far the most
cost-effective overall.
Better energy efficiency with ammonia is an accepted
fact but even that can be improved. The Bitzer chat was all
about a way to increase operating efficiencies by looking
at cascading capacity control systems to give the most
operational efficiency of the compressors.
The Bitzer argument revolves around the installation of
three identically sized capacity compressors to suit the total
designed cooling demand. Now we all know that we mostly
over-design a system to cope with the 20% additional peak
load. We have to, as it is not acceptable to lose temperatures
during the peak period through from January to March – our
warmest period. Consider that for the rest of the year the
plant is oversized.
Continued on page 69
RACA Journal I June 2019
67