GL 2018: CO₂-cooled supermarkets in Spain

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 13^th 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.