Taking de-greening to the next level at Endulini Fruit

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By Ilana Koegelenberg

When the time came for Endulini Fruit in the Eastern Cape to upgrade their de-greening rooms last year, they decided to look at alternative options to provide more energy savings.

CLIENT BRIEF

Endulini Fruit is based in Patensie, Eastern Cape, and when their ‘traditional’ de-greening rooms were becoming too small in capacity (number of crates), they started looking for a new solution. The client’s main requirement was for energy savings, water savings, increasing the number of crates per room, and increasing the humidity level during operation.

San Group was tasked with finding an alternative and came up with a unique concept that offered great savings as well as an improvement on the de-greening process. The client bought into the concept and they managed to deliver a superior quality as well as functional solution.

The plans were approved and the upgrade happened speedily from March to May 2018.

“As far as we are concerned, this is the only de-greening rooms currently operating with this level of sophistication in South Africa,” says Juan-Pierre van Zyl, refrigeration general manager at San Group.

They have made use of some of the latest type of technologies for monitoring and ease of operation. Rooms are fitted with touch screen PLC operation and the entire room’s operation can be monitored as well as adjusted as required, depending on user access on site or remotely. The rooms are all connected to an alarm system that sends out an email should there be any alarm condition.

Photos by San Group

IMPROVING THE DE-GREENING PROCESS

De-greening is achieved by keeping citrus at a constant pre-set temperature at maximum set humidity, regulating CO2 level, and introducing ethylene (ripe gas). Van Zyl explains how their solution differs from more traditional methods.

Traditional de-greening methods operate using direct expansion refrigeration design to provide cooling. Electrical elements in each room provide heating. The refrigeration evaporator coil is fitted in a false ceiling area above the room. Humidity is introduced into the room via water/air nozzles or steam humidifiers creating a mist. In most cases, this function is switched on when the room starts. CO2 is extracted via extract fans operating on an on/off pulse timer. Ethylene is also introduced via an on/off pulse timer.

 DRAWBACKS

Redesigning the traditional de-greening facility allowed the design team to make use of the latest technologies available, optimising efficiency using minimal refrigerant with lower global warming potential (GWP) and reducing electrical load.

The equipment layout has been changed by moving the evaporator coil to ground level, behind the room. This allows for easy maintenance and repair work to be carried out, and less steel construction as the overhead weight is reduced.

The door size has been increased to allow fork trucks to load rooms right up to the door, as well as making use of a gas-tight door, reducing ethylene gas leakage and temperature loss.

The new system is capable of reading real-time CO2, ethylene and humidity levels and controls these levels according to set-points. The room is operated by a sophisticated PLC, allowing full control of the room operation, real-time data, as well as remote access for off-site management. Pre-set programs can be created for different scenarios and all alarms are monitored and reported via email.

Humidity water harvesting allows for a percentage of the new water to be collected, stored in a tank, filtered, and re-used in the humidity system. The ethylene system is fitted with alarm-monitored pressure gauges and will alert when bottles are close to empty. This reduces the risk of operating without ethylene. Where multiple de-greening rooms are installed, each room can operate totally independently, allowing one room to be on heating, one on cooling, and one on holding. No unnecessary equipment will be operating if not required.

BENEFITS

The ‘plus’ feature allows de-greening rooms to operate as cold rooms when de-greening is not required. This is achieved by fitting an additional direct expansion refrigeration system. This system will only function in the cold room cycle. This direct expansion refrigeration system is fitted with the latest energy-saving equipment to optimise efficiency. No electrical heaters are fitted to this equipment; defrosting is achieved by off cycle defrosting as required.

UNIQUE DESIGN

The design is based on energy saving and they currently operate six de-greening rooms on the same power supply as the original three rooms, notwithstanding the fact that the new rooms are 20% bigger in capacity as well! Each of the six rooms can handle 360 crates.

The design is also based on the fact that any one of the rooms can be operated independently, so one room can be on cooling, while a second room can be on heating. Should any component fail on one room, it will have no effect on any of the other rooms’ operation.

Maintaining the key components is made easy by eliminating the evaporator from the ceiling void. This also reduced the weight suspended from the structure in traditional de-greening rooms. Room layout is changed, and loading and unloading of the room speed is increased. This allows for quicker turnaround time.

This is one of the only designs around that measure and control ethylene levels in the room. San Group has partnered with some suppliers in South Africa to create a sensor that can withstand the conditions and has managed to successfully control ethylene concentration in the rooms. This reduced the quantity of ethylene gas used per season, which results in a saving.

They also monitor the ethylene gas bottle level, so the client will be notified when the bottle level is low so that they can change it over instead of running out during the night and only finding out the next day.

They managed to obtain 96% and above relative humidity inside the room on heating or cooling; this increased the quality of the de-greening process. This level is achieved using the latest type of humidification and the fact that the refrigeration system is designed to reduce the amount of humidity removal during cooling or heating. It can maintain a high level of humidity and cool/heat at the same time.

CO2 levels are monitored and they control the extract fans accordingly, so no unnecessary air is extracted, preventing loss of ethylene gas, humidity, and temperature. They make use of a Class 6 gas-tight fully automated door — this door de-creases the leakage accrued in traditional de-greening rooms as well as controls access during operation.

An operation platform has been created, where the manager will set de-greening parameters and the operator will select the type of fruit to be de-greened. The system will adjust all settings accordingly. This means, for instance, you can de-green oranges today and lemons tomorrow. By selecting lemons, all settings will be changed to lemons, and after that oranges can be de-greened again by selecting the oranges. The settings and the process will be exactly the same as the first oranges that were de-greened.

CHALLENGES

The biggest challenge was that most components required could not be bought off the shelf or from catalogues, and San Group had to engineer/design and manufacture most components for this project. “We were given a short project completion time by the client, and we had to import and plan all deliveries of equipment as well as coordinate services on site to ensure everything happened according to schedule,” explains Van Zyl.
Also, this type of layout was new to the construction and structural contractors and San Group had to work closely with them to avoid misunderstandings.
But in the end, everything came together and the client was very happy with the end result, which exceeded his expectations. 

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