Mueller Azmoos

SUSTAINABLE AND REGIONAL VEGETABLE CULTIVATION

Mueller Azmoos corporation is a vegetable grower’s organisation and stands for quality and reliability. The company operates in the regional vegetable cultivation and produces in collaboration with over 120 farmers carrots, potatoes, chicory roots, spinach and onions for retailers, restaurants and processing. The producers of Mueller Azmoos merged in 1994 and founded the VPG corporation (Contract Producers Association). Since the foundation, VPG built several warehouses. Now, the refrigeration systems with synthetic refrigerant have been replaced and were replaced with the natural refrigerant CO2.

USAGE OF NATURAL RESOURCES

Mueller Azmoos and VPG are marked by innovative spirit and responsibility taking in sustainable matters. With the photovoltaic system on the rooftop, they contribute to the economic use of natural resources and produce electricity for approx. 444 households. Last year, VPG decided to replace its refrigeration systems, which were built in 2002 and 2006 and operated with the synthetical refrigerant R404A. This in cooperation with the foundation KliK. The old systems with flooded transfer systems and accordingly high refrigeration charge were replaced by new transcritical CO2-systems. The new systems have several advantages as higher flexibility concerning performance in the various halls and a significant higher energy efficiency, among others. Thanks to the support of the foundation KliK, the changeover to the new system with natural refrigerant leads to a reduction of the global warming potential (GWP) by approx. 390%.

THE LARGEST TRANSCRITICAL CO2-REFRIGERATION SYSTEM IN SWIZTERLAND?

The new system is one of the largest, if not the biggest transcritical CO2-refrigeration system which has been built in Switzerland so far. The halls, refrigerated by the new systems, store 12’000 tons of carrots and 8’000 tons of potatoes. The refrigeration capacity in the transcritical operation is 1.3 MW. During the storage phase in fall, the system can reach up to 1.6 MW in the subcritical operation. The very high refrigeration capacity led to special challenges in engineering and installation. One of the challenges was for example to ensure the availability of all major components.

INCREASED ENERGY EFFICENCY

The four halls were split into separate sections whereby each one covers an evaporator capacity of 400kW. Defrosting takes place by means of hot gas. For reducing material stress during defrosting, the hot gas is cooled to a material compatible temperature via an air-cooled desuperheater. For the refrigeration of the potato storage a plate heat exchanger, which supplies the compact cooler with a refrigeration rack, has been installed. The energy efficiency is increased significantly by using gas- and liquid ejectors. The waste heat is used for the workshop-, office- and residential buildings whereby non-usable waste heat is emitted by the air-refrigerated gas coolers to the environment. In total a refrigerant charge of 4000 kg has been taken from the old systems and disposed environmentally friendly. This corresponds to a CO2- equivalent of almost 16’000 tons. This complies approx. to a car ride of 300 times around the equator.

With the change to a transcritical CO2-system, VPG makes another step towards sustainability, thus contributing to the reduction of the environmental impact.