A green choice for De Groene Agri

This typically Dutch story dates back to 1937, when the Dutch government decided to build a dike between the cities of Lemmer and Urk to claim extra land for agriculture. In 1940, the dike was closed, and the land subsequently pumped dry. This new land, called Noordoostpolder, officially became dry on September 9, 1942.

The soil in this part of the land, actually the old sea bed of sludge and shells, was very fertile and full of calcium and minerals. Such soil is perfect for the cultivation of potatoes, carrots, onions and corn; and a lot of farmers started new businesses in the Noor doostpolder.

All these new agricultural activities required cold stores to preserve the products for a long time. De Groene Agri, situated just outside the village of Rutten, is specialised in refrigerated storage of agricultural products like potatoes, onions, chicory pens and carrots. They offer a wide range of cooling conditions and temperatures, even the ability for freezing products, and are perfectly placed to support the needs of the area. The total storage capacity covers 85,000 m3 with space for 7,000 pallets. In addition to the storage of products, De Groene Agri has the capability of washing, sorting and packaging products, added to the fact they are certified for the storage of biologically grown products.

In the winter of 2017, De Groene Agri started planning the necessary expansion of the cooling capacity. Due to the fact that the stored and chilled products represent a high economic value, the reliability of the system was a key factor in the design of the new cold stores.

The demands were that the new cold store must be:

  • Reliable
  • Sustainable with natural refrigerants
  • Provide perfect conditions for the products
  • Be food and environmentally safe
  • Have low energy consumption
  • A compact design

The Dutch company, Dijksma Koudetechniek, initially a small company founded in the seventies, working in cooling and refrigeration, has now grown into an all-round high quality refrigeration contractor, under the supervision of their current director Henk Dijksma. The knowledge and experience passed from father to son, has allowed them to expand into a modern and progressive business. With their professional team, all national and international customers are served from their office in Emmeloord.

Dijksma Koudetechniek has many years of experience in the refrigeration and freezing of products in agricultural and fruit farming. Due to the many types of products that can be stored at De Groene Agri, there was a lot of consultation between Dijksma Koudetechniek and De Groene Agri. One year ago, the first discussions began in making the right choices for the refrigeration system, mainly concerning the storage of chicory pens. The stored pens are the "raw materials" for the actual chicory, which is eventually consumed.

Firstly, the type of cooling installation was to be decided, and this is essentially determined by the product. A chicory pen is a product that must remain hydrated, produces a lot of heat and is stored in a thin layer of ice. Because this product is kept year-round, power consumption is also an important part of the system choice. After considering all demands and specifications, the choice was made for an ammonia / CO2 pumped system.

Together with Wijbenga B.V. and Cool Green Solutions, both long term partners and suppliers of the contractor Dijksma Koudetechniek, the specifications for the new cold store were transformed into a state of the art industrial cascade system using CO2 and ammonia. Both are natural refrig- erants which fitted perfectly into the desired sustainable and energy efficient design concept. Defrost of the evaporators will be done with CO2 hot gas from a generator and the CO2 generator is working with a glycol system connected to the heat recovery system.

Typically these kind of industrial cascade installations are characterized as large constructions composed of cascade condensers, separators and liquid vessels with pumps. However, the customer's wish was to build a system as compact as possible, and preferably in containers.

Dijksma B.V. created a concept out of two stacked 40 ft. high cube containers. The first container contains the CO2 liquid vessel, CO2 pumps and a CO2 hot gas generator. The second container was placed on top of the first one and accommodates the compressors and cascade condensers. An air-cooled V-shape condenser is placed on top of the two containers.

It soon became clear that the Vahterus combined, a heat exchanger/evaporator with integrated separator, was perfect for this job. This eliminated the need for additional ammonia pumps, provided no risk of ammonia leakage due to gaskets, is compact, easy to insulate and offers a long and maintenance free lifetime.

In the ammonia / CO2 cascade system, the cascade condenser is a crucial component that separates the ammonia and the CO2 refrigeration cycles. Even if the risk of a leakage is very small, some have experienced that the consequences of a leakage can be very severe. A shutdown of the plant, even if it is only for a short time, must be avoided at all times. The Vahterus separator system inside the Combined, has the unique ability to detect the salts formed during an ammonia - CO2 leakage and works as a big filter that protects the compressors. After detection, further contamination of the ammonia system can be avoided by closing the valves and isolating the affected component.

In the De Groene Agri installation, the total cascade condenser capacity of 1 MW is divided between two 500 kW Vahterus Combined PSHE cascade condensers, running at 4K temperature difference. An open flash economiser provides ammonia to the combined cascades and improves the overall performance of the plant.

In the unlikely case that one of the cascades is shut down, the other cascade condenser will still be available. The capacity can be temporarily increased by increasing the temperature difference over the cascade condenser. Additional capacity within the internal Vahterus separator system is enough to run the full compressor capacity with one cascade condenser, and can still keep all rooms at the desired temperatures.

Wijbenga engineered and supplied the Vahterus combined cascade condensers, economiser, CO2 vessel and CO2 pumps. The containers were assembled in the factory of Cool Green Solutions. Based on the close and effective cooperation of the customer, contractor and manufacturer, it was possible to fulfil the ambitious wishes of the customer.

One final point of note was that De Groene Agri also installed 2.7 acres of solar panels. In doing so, the company also contributes to the preservation of our planet and hopes this serve as an example to others in their business sector. This plant is ready for the future!