CO2-based technology can provide efficient heating and cooling in Spanish supermarkets despite the country’s warm climate, according to a paper presented by experts from the NTNU and SINTEF at Gustav Lorentzen this week. Estimations based on six representative cities show how HFC-free solutions lead to remarkable energy savings.

The EU F-Gas Regulation bans the use of certain HFCs with GWPs above 150 in new centralised and plug-in commercial refrigeration equipment from 2022. This presents opportunities, therefore, for natural refrigerants to replace HFCs, the researchers point out.

Yet in Spain, a number of national legislative barriers complicate the scenario: for example, Royal Decree 138/2011 prohibits the use of hydrocarbons in medium to large-sized stores for safety reasons. The researchers suggest that carbon dioxide (R744) may be a viable natural-refrigerant solution.

A paper presented at the recent Gustav Lorentzen conference in Valencia investigates the energy-efficiency performance of two alternative systems serving the refrigeration, air conditioning and space heating needs of a supermarket. One uses R134a in the high-temperature circuit and CO2 in the low-temperature circuit, together with an HFO R1234ze reversible heat pump. The other one is a CO2 transcritical system.

To take into account the peculiarities of the Spanish warm climate, researchers collected data for six major cities. Average outdoor temperature in the sample ranges between 9.9°C in Burgos and 21.1°C in Tenerife (other cities included in the analysis are Madrid, Barcelona, Valencia and Seville).

In heating mode (between -5°C and +15°C), the CO2-only solution proved to have a COP 83% higher than the R1234ze-based system. In air-conditioning mode (between +25°C and +40°C), the results are not as positive, given the substantial cooling demands.

Saving energy with CO2

As for annual energy consumption, the R744-based solution offers energy savings between 1% (Tenerife) and 33.2% (Burgos) compared to systems using HFCs.

The research therefore suggests that natural refrigerants-based solutions exist and can outperform HFC-based systems. CO2 is described as a “future proof” refrigerant in the Spanish context, given its compliance with all regulations and its energy efficiency performance.

The paper was presented at the 13th IIR Gustav Lorentzen Conference on Natural Refrigerants by Paride Gullo (NTNU), Armin Hafner (NTNU) and Krzysztof Banasiak (SINTEF). The event took place on 18-20 June in Valencia and gathered more than 250 experts from all over the world.

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