Warehouse complex Maersk

Maersk warehouse complex on the CO2 transcritical system. An integrated approach to energy efficiency.

A large warehouse complex was put into operation in Saint Petersburg for the Danish logistics giant Maersk - the world leader in container shipping and port terminal services. The new refrigerated warehouse has a total capacity of over 40,000 pallets, 35 docks allows to receive up to 200 vehicles per day, and the maximum storage capacity can exceed 50,000 tons.

The centralized refrigeration system of the facility is based on an energy efficient natural refrigerant CO2, the total refrigeration capacity of the equipment is about 2 MW. This makes the Maersk warehouse complex in Saint Petersburg one of the largest commercial refrigerated warehouses in Russia using transcritical technology.

The full cycle of design, production, installation and commissioning of refrigeration systems was was performed by Ingenium. Three identical transcritical booster units with a capacity of 180 kW of low (T0 = -32° C) and 480 kW of medium (T0 = -6° C) cold each are responsible for cold supply of the warehouse complex. The engine room was moved outside the warehouse.

«INGENIUM is a leader in the implementation of CO2 technologies on the Russian market. Over the past few years, the company has implemented about 20 projects on carbon dioxide, and currently the team continues to prove its high level of competence in the application of this technology.»
ingenium-company.ru

"At the initial stage, for the implementation of the project, the customer considered the option of a refrigeration system based on R507A freon as a traditional solution with relatively low capital costs. R448A and R449A were also considered as alternatives with low global warming potential. However, these refrigerants are expensive, practically not available on our market and do not exceed R507A in terms of energy efficiency. We proposed and substantiated a solution based on carbon dioxide. It is an environmentally friendly and energy efficient refrigerant, and it is guaranteed not to be affected by legal restrictions during the entire life of the equipment", — said Alexander Nadeev, head of the sales department for complex projects at Ingenium LLC.

The use of three separate refrigeration stations ensures complete system redundancy. The air coolers of the refrigerating chambers are connected in such a way that when one of the units is turned off, not a single zone will be left without cold - it is overlapped by the air coolers of the adjacent system.

Each installation uses parallel compression technology, which allows you to unload the medium-temperature circuit compressors and increase the energy efficiency of the system. Parallel compressors operate at a lower compression ratio and consume less electricity.

The leading compressors of each circuit are equipped with frequency converters. They smoothly adjust the performance of the compressors so that it clearly corresponds to the required load. This makes a significant contribution to optimizing the system's power consumption. There are two compressors with frequency drives for the medium-temperature circuit.

Cold consumers:

• Luggage storage;
• Fresh vegetables and fruits storage room ventilation system;
• Dock houses for frozen food storage.

2 lockers:

• Storage room for fresh vegetables and fruits, temperature +2 ... + 4 ° C, area 4150 m2, storage capacity 15,000 tons;
• Luggage storage +25 ....- 18 ° C, area 7000 m2, storage capacity 20 000 tons.

In addition to the cooling supply of air coolers for the low-temperature and medium temperature circuits, the facility has ventilation systems for the storage room for fresh vegetables and fruits, as well as air conditioning for the engine room. They are realized through a cycle with an intermediate coolant (propylene glycol solution), which is cooled in a plate heat exchanger with boiling CO2. The pumps for supplying coolant to the heat exchanger of the supply ventilation system are also equipped with frequency converters. This allows you to reduce energy consumption while reducing the required consumption.

• Low-temperature mode of CO2, 3×180=540 kW;
• Medium temperature mode of CO2, 3×480=1440 kW;
• Medium temperature mode R448a, 6×10=60 kW.

For economic reasons, the refrigeration supply of the dock houses of the frozen food storage room (T0 = -13 ° C) was implemented using six small Danfoss Optyma SlimPack condensing units on R448A of 10 kW each.

One of the important advantages of CO2 over other refrigerants is the great potential for heat recovery. At the Maersk warehouse complex, waste heat from refrigeration units is used for ground heating and defrosting of air coolers.

The recuperation system extracts high-grade thermal energy for propylene glycol heating from two CO2 pressure levels: from the discharge line of medium temperature / parallel compressors and from the discharge line of low temperature compressors. In addition, the removal of heat from the discharge low temperature compressors further reduces the load on the medium temperature compressors.

The warmed glycol is accumulated in a buffer tank and distributed in two circuits: for defrosting air coolers and heating the ground. The heating system protects the soil under the low-temperature chamber from freezing. For redundancy purposes, it is multi-circuit. eating control is implemented on the basis of freely programmable controllers Danfoss MCX.

The pumps of the primary circuit of the recuperation system and the defrost circuit of the air coolers are also equipped with frequency converters.

At the facility, the possibility of further expansion of the recovery system is left. For example, for heating the fruit chamber in winter.

Danfoss controllers and monitoring system are used for automation of all circuits of the cooling system. This combination optimizes the parameters and increases the energy efficiency of both individual elements and the system as a whole. For example, maintaining a floating boiling and condensing pressure reduces the load on the compressors, the minimum stable overheating algorithm helps to use the entire useful area of the evaporator, and adaptive defrosting is started only when it is really necessary. Monitoring allows you to remotely monitor the operation of the system, respond to alarms in a timely manner, make changes to schedules, and much more.

"The example of the Maersk warehouse shows that well-implemented projects are always the result of teamwork and partnership. Such interaction makes it possible to comprehensively approach the solution of engineering problems. At every level of the system, Danfoss components contribute to its reliability, safety and efficiency. And these advantages are quite tangible and measurable for both our partners and the end consumer. Solutions for transcritical systems, which were previously applied with caution, are now the standard and the hallmark of quality precisely because they bring results. It is important for us to be a part of the growing market for CO2 systems and participate in its development", — said Alexander Seravin, Director for Sales of System Solutions and Regional Development at Danfoss LLC.

The main advantage of a system based on a traditional refrigerant (for example, on R507A) is its relatively low capital cost. However, when assessing the feasibility of using a particular refrigerant, it is necessary to take into account the entire life cycle and cost of ownership of the refrigeration system. The longer the life cycle and the higher the operating costs, the more urgent becomes the issue of implementing energy efficient solutions.

When developing the project, Ingenium LLC engineers compared data on the energy consumption of R507A installations and CO2 of the same capacity. The calculation took into account the coefficients of seasonal equipment utilization.

The expected energy consumption of the CO2 system will be 3,882,100 kWh per year, which is 1,480,500 kWh less than the system based on R507A using the following standard technologies: screw compressors with economizers, air-cooled condensers, defrost of air coolers with electric heating elements, heating the soil with a heat carrier.