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Evaporative vs hybrid condensers

  • marimac 

By Lizelle van der Berg, director – GCCA South Africa

With the unreliable water supply in South Africa, cold storage facilities can sometimes find themselves without sufficient water supply for days and everyone knows that condensers need water to keep the cold chain going.

Water supply is not the only concern. The high cost and unreliable supply of electricity have a severe impact on our industry running on diesel generators for hours per day. That brings us to the high price of diesel and the unreliable supply of diesel in certain parts of South Africa. Our industry is facing major challenges and are looking at innovative ways to mitigate the risks they are facing.

I spoke to Garid Glenn, applications manager of Baltimore Aircoil International and requested information on evaporative vs hybrid condensers to find out if this might be one option to consider. Glenn did a great job in proving the information so that we can see the impact of evaporative vs hybrid condensers by referring to a case study in Cape Town.

Overall Efficiency

It’s important to note that in a refrigeration system, the compressor consumes a significant amount of energy, and this energy consumption is related to the condensing temperature.

Evaporative saves up to 30% on compressor power compared to dry. Image supplied
Evaporative saves up to 30% on compressor power compared to dry. Image supplied

The lower the condensing temperature, the lower the energy consumption.

When a dry condenser or hybrid condenser is used in a refrigeration system, the condensing temperature needs to be higher to allow the unit to switch over and run dry for as long as possible. This will allow for a water saving but creates a significant impact on the energy consumption.

Consumption simulation

In this case, for a project based in Cape Town, we can assess which is the better solution when comparing hybrid coolers and evaporative coolers. The evaporative units can target a lower condensing temperature throughout the year, which allows for significant energy savings on the compressor, this would however require water to be consumed, but the water cost will only be approximately 18% compared to the overall operation cost of the system.

When looking at the graph below: based on the Cape Town electricity tariffs, summer has an average tariff of R1.06/kWh and winter an average tariff of R2.19/kWh (low voltage time of use – large user). Based on this data you will notice that in winter there is a significant increase in energy cost.

Typical water-cooled plant. Make-up: 34,8 R/m³, Sewage: 31,2 R/m³, Electricity (25% of year): 2,19 R/kWh, Electricity (75% of year): 1,06 R/kWh. Weather data: Ashrae – South Africa – Cape Town int Airport. Image supplied

The only time that a hybrid unit will be able to run dry would be during winter, in order to run dry, the condensing temperature has to be higher and therefore the compressor energy consumption is higher which leads to an even higher cost due to the increased tariffs.

A typical evaporative condenser. Image credit: Baltimore Aircoil Company
A typical evaporative condenser. Image credit: Baltimore Aircoil Company

Peak demand

Another significant advantage of a lower peak condensing temperature would be a much lower peak energy demand. The energy problems in South Africa currently are not necessarily the consumption of energy, but actually, the generation capacity available. The peak energy demand of a water cooled installation is as much as 30% lower than an air-cooled system, which reduces the strain on the energy grid.

GCCA Risk & Insurance Seminar – March 2023

Electricity and water supply are not the only challenges faced by our industry. Join us for a full day GCCA Risk & Insurance Seminar on 2 March 2023 in Johannesburg where we will be discussing the various risks faced by the cold storage industry as well as possible solutions.

This full day risk & insurance seminar will bring together the temperature-controlled warehousing and logistics industry executives, cold store operators, controlled-environment builders, equipment suppliers and service providers. Learn from industry peers and also gain insights on crisis management.