Mechanical cooling without refrigerant is possible

Natural refrigerants in commercial cooling

As early as the 18th century, the natural ice trade began in North America and later also in Europe. A large industry hung on it for almost 100 years. The "white gold" was transported via trade routes to all over the world and represented enormous progress. After all, the dismantling and various uses of this first natural refrigerant brought work, year-round supply of fresh food and continuous manufacturing processes in breweries or meat processing. It was not until industrialization in the 19th century that the mechanical production of ice and later of cold energy with refrigerants such as ethyl ether, ammonia, and CO2, or so2 location-independent and ultimately ice trading is superfluous. Then, however, leaky refrigerators and air conditioning systems led to fatal accidents, which prompted the US company General Motors to develop the first CFC refrigerant in 1928. Long believed to be safe, around 50 years later their ozone depletion potential and contribution to the greenhouse effect became apparent. Today, the HFO is the fourth generation of synthetically produced refrigerants. So far, none has been able to deliver an ideal result. In addition, the synthetic materials are becoming more and more similar to the natural ones. Commercial refrigeration has gone back to its roots and now works with the natural refrigerants CO in new systems2 and hydrocarbons.

It doesn't work without freshness

Commercial refrigeration is indispensable for our society and the global trade in goods. Because it is the only preservation method that preserves the product freshness from production to the point of sale. The focus of retail today is on sustainable and efficient cooling methods. To protect the earth's climate and for low-consumption, cost-effective and long-term plant operation.

Retail groups realized years ago that the politically expected CO2- Above all, you can get savings potential from the refrigerants. This is why composite refrigeration systems based on natural refrigerants have become standard in Switzerland and in many other European countries for medium-sized and large markets. Supermarket and hypermarket operators in particular rely on transcritical CO2-Booster systems for deep freezing and normal cooling. Ejector technology is increasingly being used to further increase energy efficiency. This means that systems work more efficiently at higher ambient temperatures.

Bitzer offers an alternative to this with the new expander, which is not only suitable for new systems, but also for retrofitting. Starting from an ambient temperature of 32 ° C, the cooling capacity of a standard booster system can be improved by over 20% in the design point. In addition to the large network systems, a number of manufacturers now also offer small condensing units for CO2 at. Cooling capacity ranges from 1 kW to 10 kW for deep freezing and for 2 to 16 kW for normal cooling are covered with just one air-cooled condenser. Similar to a split air conditioning system, the installation should be very easy. Target groups are small grocery stores, cash + carry markets, petrol station shops, butchers as well as the catering and hotel business with few cold stores and cold rooms.

As a second long-term solution, hydrocarbons are used today. In 1993 the first mass-produced isobutane refrigerators came onto the market. This was followed by plug-in chest units, beverage coolers or plug and piggyback units with propane. Supermarkets and discounters are now using this flammable refrigerant in decentralized refrigeration systems and new refrigeration units for normal refrigeration and in cold rooms. For this purpose, the primary refrigerant circuit is either located in a central location in a machine room, or in the store and in the refrigeration unit. Heat energy is transported away via the secondary circuit - also known as the water loop - to the environment by means of a heat exchanger.

“All in all, commercial cooling has contributed significantly to CO savings of 50% since 19902Emissions. "

Climate goals achieved

Industry has taken a leading role in climate protection. This is because retailers operating across Europe have been investing on their own initiative in energy-saving stores and branch renovations for years. In addition to new consumer-friendly store concepts, the focus is on reducing energy consumption for light, heat, air conditioning and refrigeration technology. In the chain grocery store, for example, the share of energy costs in net sales is 1.4%. In terms of power consumption, cooling has by far the largest share of this with 47%. The described conversion to modern refrigeration systems with natural refrigerants makes a contribution. According to a current survey by the EHI Retail Institute from Cologne, 41% of grocery retailers have each invested more than 25 million euros in energy efficiency measures in the past 5 years. The renovation rate in retail has been at a fantastic 10% for years - in contrast to the residential building stock with only 1%. All in all, commercial cooling has contributed significantly to CO savings of 50% since 19902Emissions, has already exceeded the climate protection targets set by the federal government by 2030. According to the Handelsverband Deutschland (HDE) e.V., over 500 million have been invested in this since 2013.

Energy management in commercial cooling

Energy management has also been part of the sustainability strategy and investment planning in commercial cooling for years. According to the European CSR Directive (2014/95 / EU), which has been incorporated into national law since March 2017, large German companies must give an account of their social and ecological actions. All capital market-oriented companies that employ more than 500 people and whose total assets are either more than 20 million euros or whose sales revenues exceed 40 million euros are affected. According to the EHI, 60% of the companies surveyed in the food retail sector publish a sustainability report, which of course also includes measures to reduce CO2- includes reduction.

Practical examples

Commercial cooling is therefore making headway in many European countries. It is noticeable that planning is very foresighted. Metro AG decided to phase out F-gases in mid-2013. Since then, new buildings and conversions have been equipped with natural refrigerants as far as technically possible. More than 170 stores across Europe now work with CO2 for normal and deep freezing. The latest example is Metro Cash & Carry Austria GmbH. Their pilot project in St. Pölten, Austria, includes the establishment of a zero-emissions wholesale market, in which mostly sustainable materials were used. The wholesale market works without external heat supply and air conditioning with a concrete core activation and a natural ventilation concept. In winter, the transcritical CO2-Cooling system plus ejector heated. Thanks to all the measures implemented, the energy requirement is a minimum of 115 kWh / m2 Sales area.

The REWE Group started a program in 2008 to cover all of the CO2- Halve emissions per m² of sales area compared to 2006. According to the 2017 sustainability report, 40.3% had already been achieved. In November 2009 the trading company opened its first nationwide CO2-neutral market. The refrigeration systems use CO for normal and deep freezing2 as a refrigerant, propane for plug-in chests. The heat required for heating is obtained from the CO2-Cooling process decoupled.

Migros takes a pioneering role

Migros Ostschweiz went one step further in 2017 with its first plus energy store in Zuzwil, Switzerland. The aim of this project was a branch that could cover its own energy needs. This was achieved through a bundle of measures, including the use of waste heat from the refrigeration system and with refrigeration units that raise the evaporation temperature to a constant 0 ° C without defrosting at a desired room temperature of + 2 ° C to + 4 ° C. The market is part of Migros' internal climate and energy strategy 2020, which provides for a 20% reduction in greenhouse gas emissions and a 10% reduction in electricity consumption by 2020.

As a trading group organized as a cooperative, the Edeka trading group also relies on the refrigerant CO in many markets2. The Edeka regional company Minden-Hannover was recently selected for the combined use of a modulating CO2-Ejector awarded with a refrigerant pump. The project was implemented during ongoing operations in a cash & carry store in Soltau, which further reduced energy consumption and increased energy efficiency.

In addition to large supermarket operators, discounters also work with natural refrigerants. Aldi Süd has had integrated systems with the refrigerant CO since 20062 or propane for chests in the program. Aldi Nord is testing propane in interconnected systems with a Waterloop system and market competitor Lidl started using propane in an integral system as early as 2009. The refrigeration units are either located directly in the prefabricated refrigeration units or are designed as separate evaporator units that are used in cold rooms or cold rooms.

Back to the Future

Commercial cooling has therefore found its way back to its natural origins with refrigerants. A development that is sure to be sustainable for the future and which can hardly be described more appropriately than with this final quote:

“An ideal refrigerant that meets all of the requirements mentioned has not yet been found and will probably not be found in the future either. In each case one will therefore have to be content with seeing the most important requirements fulfilled in each case and come to terms with those that cannot be fulfilled as best as possible. "

It comes from one of the most comprehensive and important series of publications entitled “Handbuch der Kältetechnik” by a pioneer in refrigeration technology: Prof. Dr.-Ing. Rudolf Plank - written over 60 years ago!

The article appeared in the 1/2019 issue of the “Compact” customer magazine from Bitzer Kühlmaschinenbau GmbH, Sindelfingen.

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