CONTRIBUTORS
INCORPORATING COLD CHAIN
Energy efficiency with ammonia systems
We should all be aware that energy costs in South Africa are escalating . Not only that , but with countrywide load shedding the unpredictability of electrical supply has led to the event of most cold stores and key industries now having generators fitted to ensure that services are maintained .
Sadly , this is a fact of life , and the lack of supply is throttling the expansion of the economy while another consideration is the impact of the energy efficiency of our cooling systems and their impact on power usage .
Energy efficiency is critical to the ongoing issues with climate change . We all know that ammonia is a climatically friendly refrigerant , but what about the carbon footprint from the energy consumption ? It makes sense to take a look at the installed systems to see where we can improve efficiencies . This may mean a radical look at the plant and , we will discuss this next month , even the replacement of the existing operational plant with a more modern energy efficient solution .
By Andrew Perks
Some time back , around the end of the 90s , Eskom started realising it had a problem balancing the power availability on the grid to the country ’ s expanding demand for power , and the industry was informed it should reduce power consumption by 10 %. Up till this point , power was plentiful and cheap so we put up with the inefficiencies , but those days are now gone .
I was approached by a large fruit processing company in Ceres with a view to reducing their power usage . The plant had both a chilling application and a low temperature cold store . Each of these systems had their own design considerations . Being out in the country , the site had three different electrical tariff rates depending on when the demand for electricity was required .
After careful consideration it was decided that it was beneficial to switch off the freezer plant during peak demand tariff periods in the week and run full capacity over the weekends to catch up . This solution is not viable with a chilling plant . On the chilling plant we modified the condenser ’ s piping and replaced an old condenser with a larger unit . This resulted in a reduction of the condensing pressure from 37 º C to 33 º C . At that time , due to cost considerations , variable speed drives were not considered , so the brief was to go ahead with the other modifications . It was an interesting and successful project where we met all the requirements .
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 .
26 www . coldlinkafrica . co . za COLD LINK AFRICA • October 2021