In 2020, the western breeders’ association Growers United has moved into new premises with a logistics center in Maasdijk. Here, gigantic amounts of fruit vegetables must be conditioned. This is done with an ammonia / CO₂ installation with a capacity of 1,050 kW. The order for this went to Hamelink Koeling. Director Eelco Hamelink explains the project, which has caused a turnaround for the installer.
Text: Uko Reinders
Growers United is a cooperative of more than forty family businesses with a total greenhouse area of approximately 600 acres. The cultivation consists of tomato, eggplant, pepper and cucumber. Once harvested, they are brought to the packing hall in boxes. There they are conditioned, packed, sold, distributed among the customers and finally loaded into trucks to take them to the customers. With more than 70 million kilos a year, this is a huge daily flow of products.
Design made in 3D
In 2020, the cooperative moved into new premises in Maasdijk, which was officially opened in October 2021. A new building also meant that a new cooling installation had to be installed. In addition, a tender round was set up, where the choice fell on the offer from Hamelink Koeling. The cutlery with which the contract was won was a rough draft. This was first further elaborated in 3D in BIM software for a concrete design. “It was our first experience with BOS; we are now preparing 80 percent of the projects with this software, ”says Eelco Hamelink. When the design was ready, the installations were built. This happened, among other things, at the installation company’s own workshop.
Conditioning at different temperatures
The new Growers United building consists of different rooms that need to be conditioned at different temperatures. There are two shipping areas: one where the products arrive and one where they are ready to depart for customers. These areas must be kept at a maximum temperature of 16 C. This is also the maximum temperature in the processing area where the fruit vegetables are packed. The six cold stores, which are equipped with a fully automatic pallet system, have a temperature of 12 ˚C.
The ammonia refrigeration system with a total cooling capacity of 1,050 kW works with three compressors. Two of them are 460 kW screw compressors (OSKA 8581 from Bitzer), equipped with capacity control. The third compressor is a smaller reciprocating compressor with a capacity of 130 kW (Bitzer W6FA), equipped with frequency control. If cooling is required, the small reciprocating compressor first goes to work. As soon as it is at its maximum partial load, the first screw compressor is added. When running at its maximum, the second screw compressor starts.
Considerations for choosing a compressor
In summer all three compressors usually run, in winter only the reciprocating compressor. “It has the highest efficiency at part load, which is why we chose this in the design,” says Hamelink. Why not choose three reciprocating compressors? Hamelink: “They are smaller than screw compressors. If we had only used reciprocating compressors, we would have had to install more, which would not be beneficial in terms of investment and return. We could also have chosen one large screw compressor, but if it were to fail, the problems would obviously be unmanageable. So that was not an option. “
Pump system with CO₂ as coolant
The evaporation temperature of the ammonia plant is 1 ° C. That temperature is transferred via a heat exchanger to a pump system with CO₂. Hamelink: “We chose CO₂ as a refrigerant because of its high efficiency, that is, good energy transfer.” CO₂ is pumped through the building under a pressure of 45 bar through all air coolers in the various rooms. The CO₂ then returns to the CO₂ separator in the engine room, which is cooled back to approx. 4 ˚C of the ammonia.
Higher capacity CO compressors
According to Hamelink, the choice for ammonia in the primary circuit was quite logical at the time: “This is due to the large cooling capacity. If we had chosen the CO₂ alternative, we would have had to install a lot of compressors, which would be less favorable in terms of return and investment. ” That theory is now obsolete; there are now higher capacity CO compressors on the market. For installation at Growers United, a setup with several CO₂ compressors can meet. Hamelink: “Had we now designed the installation, I would definitely have investigated the possibility of a complete CO₂ system. Such a system is cheaper and you avoid the safety precautions that apply to ammonia. This allows you to save extra costs on the construction of the engine room. ”
PLC system measures temperatures
CO₂ is of course not harmless either. Therefore, CO₂ sensors are installed in all cooling areas at the cooperative. The concentration values are monitored by Growers United’s technical service and at Hamelink. This is done using a PLC system developed by Hamelink itself. In addition to the CO₂ values, the temperatures in the rooms are also monitored by the PLC system; more specifically the intake and outlet temperatures of the air coolers. If something is not right, an alarm is triggered. In the program, a graphical image shows exactly where the measurements are made and what the measured values are.
Variation in CO₂ values
Hamelink sees variation in the measured CO₂ values due to the emissions from the fruit vegetables. CO₂ production differs from product to product, and the number of people working on the premises also has an impact. The concentration values remain below the threshold of 5,000 ppm. Monitoring the climate on the premises is also the responsibility of Growers United. During the first months after commissioning, Hamelink Koeling controlled and remotely monitored the installation. The task was then handed over to Growers United’s technical department (TD), which is now responsible for it. Hamelink has trained people in TD at Growers United for this. Control and registration of climatic conditions is also part of the quality assurance of the products. Especially supermarket customers want to know exactly how these conditions are.
Heat recovery for box washers
In addition to the compressors, the evaporators are of course also an important part of the refrigeration installation. These are from Thermofin and equipped with speed-controlled EC fans, which are also controlled from the PLC program. Heat recovery is also an important aspect of the design. A heat exchanger is located in the central pressure pipes of the ammonia compressors, which can transfer the full heat capacity from the cooling system to a hot water system. The hot water from here is used for the laundry system. The remaining, unused heat is dissipated by an air-cooled condenser on the roof.
‘May-have’ ensures energy savings
The installation has been running for over a year now, and according to Hamelink, it works exactly as desired. “We have gained a lot of knowledge to ensure that the installation runs as stably as possible.” The ‘must-have regulation’ that is included in the internally developed PLC software is of great importance in this regard. The control sometimes starts to cool earlier, to let the compressor run. “The reciprocating compressor must always run. But when the minimum temperatures have been reached in all rooms, cooling is no longer necessary. But if we experience that a room almost has to be cooled again, the compressor does not switch off.” ‘May-have’ has already resulted in the ammonia refrigeration system not being cooled to 1 C, but to 2 or 3 ˚C. “It saves energy.”
Switch to central installations
The project at Growers United is the largest that Hamelink has completed to date. Previously, the installer mainly dealt with smaller refrigeration installations for growers. But the nurseries are getting bigger, and so are the cold stores and systems. “Due to the growth of the companies, we see a shift from several separate systems to central installations. For new construction or replacement, we recommend switching to a central installation with CO₂ or ammonia in combination with CO₂. Hamelink is now working on projects with even greater cooling capacity than at Growers United, and the employees have been trained to work with natural refrigerants, so the project at Growers United has led to a significant turnaround for the installation company.