UPDATE: Swedish supermarket receives new compSUPER Sigma by Advansor

By Janet Thompson, Feb 05, 2014, 11:59 4 minute reading

Advansor has developed a new concept, the compSUPER Sigma system, which combines cooling, frost, heat recovery and air conditioning into one single plant. A system has been delivered to a Coop supermarket in Sweden. Update: Early results show very good performance and favourable energy savings of up to 6% of the total yearly energy consumption. The case study is featured in the 2nd “GUIDE Europe” launched last month.

The newly-launched and freely available “GUIDE 2014: Natural Refrigerants -Continued Growth and Innovation in Europe” presents a selection of outstanding examples of natural refrigerants in Europe, covering commercial and industrial heating, air-conditioning and refrigeration solutions. Advansor’s transcritical CO2 booster system - compSUPER Sigma –installed for retailer Coop is incorporated in the GUIDE as one of the real-life examples of successful natural refrigerant technology.

In February 2013, Advansor delivered its newly developed compSUPER Sigma system to a Coop supermarket in Sweden, which chose the system as part of its plan to become climate neutral by 2020. The Coop supermarket had the following baseline requirements:

  • To keep products displayed and stored at medium and low temperatures, requiring cooling capacities of 56kW at -7°C and 154kW at -38°C, respectively.
  • Hot water production and air conditioning needed to be covered, requiring production of +60°C and +7°C water, respectively.

Benefits of parallel compression

To meet these needs, Advansor delivered two identical transcritical CO2 booster systems rather than a single plant solution. The two full packs, including a condenser/gas cooler for each plant were based on a single rack design fully fitted with compressors, oil management system, receivers, safety equipment and electrical board including a controller system for reliable operation.

The traditional booster design consisting of a MT and LT suction group was modified by adding compressors in connection with the intermediate stage (parallel compressors). Each system included a compressor configuration that consisted of 3 LT compressors, 3 MT compressors and 2 parallel compressors. The MT and parallel compressors were equipped with frequency inverters for optimum control according to the load.

The addition of parallel compression to the intermediate stage contributes to an overall higher energy efficiency of the entire plant. This is due to the possibility of closing the receiver gas bypass (-line) and maintaining the compressors’ receiver pressure, rather than having to throttle it by a standard gas-by-pass valve, in which the intermediate pressure is lowered to a common suction pressure before compression by the MT compressors. Having both operating/control options allows the system to ensure the lowest possible power consumption during summer operation with AC and winter operation with heat recovery.

Heat recovery and air conditioning

For heat recovery and air conditioning purposes, Advansor integrated plate heat exchangers into the system. Heat recovery was applied on the high stage discharge side, enabling the store to use the high discharge gas temperature for hot water production, before the discharge gas entered the condenser/gas cooler. Through optimum heat exchanger design, Advansor was able to achieve a heat recovery capacity of 134kW and 60°C water production.

The systems were also equipped with a “false load” evaporator, which was integrated into the externally supplied gas cooler. Through this, it is possible to utilize the same rejected heat from the gas cooler to create a false load on the system for hot water production when the evaporator loads on the medium and low temperature shop cabinets are insufficient.

In addition, a secondary heat exchanger was added for production of 7°C (7/12°C) water for air conditioning. This is based on a unique design, which is currently being patented by Advansor.

Our feedback on the delivered compSUPER Sigma system has been very positive regarding the performance so far. We are very pleased to see that this delivery is being followed by an increasing number of inquiries for integrated properties provided by the compSUPER Sigma,” says Advansor Sales Director Torben M. Hansen.
6% yearly energy savings achieved by the compSUPER Sigma

Simulated calculations of a comparison between a standard CO2 transcritical booster system and the delivered system design with integrated parallel compression shows favorable energy savings of up to 6% of the total yearly energy consumption. This is mainly achieved by enabling operation with a lower compression pressure ratio by the parallel compressors versus throttling between the receiver and the system’s common suction pressure determined by the medium temperature stage. Favorable for heat recovery, the integration of parallel compression enables improvements to the COPHEAT by up to 40% in a comparison between the load on the MT compressors versus the load on the parallel compressors.

The system has been performing very well, accommodating the demands from the customer. While experiencing reliable operation so far, the systems are monitored for maintaining continuous optimized performance.
 

About Advansor

With more than 750 operating systems using CO2 as the refrigerant, Advansor is a leader in the development, production and sale of sustainable refrigeration and heat pump systems employing natural refrigerants. Based in Denmark, Advansor, which was acquired by Hillphoenix in 2011, delivers products and expertise aimed at reducing operating costs for customers and helping global companies meet the restrictions related to greenhouse gas emissions.
 

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By Janet Thompson

Feb 05, 2014, 11:59




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