On hot summer days in particular, many of us appreciate a refreshing beer from our own fridge. However, even during the brewing process itself certain temperatures have to be maintained. For example, the fermentation temperature of top-fermented beer is up to 22°C, while for bottom-fermented beer it should not exceed 10°C. For the “amber nectar” to succeed, breweries need refrigeration solutions tailored to their processes and individual requirements. “Nowadays, these systems are not just energy-efficient. If they also use natural refrigerants like ammonia, they are also particularly environmentally friendly,” says Georges Hoeterickx, member of the board of eurammon, the European Initiative for Natural Refrigerants. “This is because natural refrigerants have no, or only very low, global warming potential.”
It is an accepted fact, that brewers had a mayor influence in regards to the development of refrigeration systems. Already in 1876 an ammonia system enabled a Bavarian brewery to produce beer at any time of the year. Due to the positive properties of natural refrigerants many breweries did not change over to synthetic refrigerants. In the following, some cases from recent years are introduced.
Brewery in England enjoys higher output and reduced energy costs
Since it was established in 1807, the Daniel Thwaites brewery, one of the top ten breweries in England, has been an independent, family-owned and operated company with headquarters in Blackburn. To improve its refrigeration capacity and to save energy costs, the company commissioned the cooling specialists from Star Refrigeration to optimise the existing refrigeration system. Heat exchangers and separator vessels had already been replaced in the course of previous projects. A newly installed GEA Grasso reciprocating compressor, featuring inverter drive and using the eco-friendly natural refrigerant ammonia, increases output from the previous 310 kW to 400 kW, while at the same time reducing operating costs. The improved energy efficiency is largely due to the use of the new inverter-driven reciprocating compressor instead of the original unit that ran constantly at the same speed, and to the installation of a new compressor control system. Energy measurements show that the brewery is saving around 2,000 GBP (approx. 2,500 Euros) a week in electricity costs, and that the investment will pay for itself in less than 18 months.
Eco-friendly beer cooling with heat pump option
The “Herzoglich Bayerische Brauhaus Tegernsee” in the Alps is regarded as one of the oldest remaining breweries in Bavaria and produces around 120,000 hectolitres of beer every year. In 2010, industrial refrigeration specialists Th. Witt supplied an environmentally friendly refrigeration system for chilling the brewing water. Up until the rebuild, the wort chilling (four brews a day) had been done in the traditional way using an ice bank system. Due to the brewery’s planned increase in capacity to nine brews, a new refrigeration solution was required. The brief was to design a system that could be operated at almost constant capacity throughout the day. In addition, it was to incorporate the option of subsequently connecting a heat pump to the system so as to supply heat to adjacent buildings like the "Braustüberl” pub and restaurant. During the chilling process, 190 litres of brewing water have to be cooled down from +16°C to +2°C within two and a half hours. In the new system, cooling water consumption for the condensers was to be reduced as far as possible. Th. Witt installed a gravity-type NH3 system with separator and plate evaporator. To assure the supply of cooling at all times, two reciprocating compressors were installed. While one compressor is in operation the second one is in standby.
To completely dispense with cooling water, the engineers designed the system with an air-cooled condenser for condensing the refrigerant. The system cools a secondary refrigerant loop with glycol to a temperature of -2°C. By means of a secondary plate heat exchanger operating with glycol and fitted with an outlet temperature controller, the brewing water is then cooled to the required temperature of +2°C and stored temporarily in an insulated basin. The system’s cooling capacity is 124 kW and it uses around 100 kg of ammonia as refrigerant.
Modern beer cooling using R723 – the refrigeration solution for the lower output range
The Ottenbräu Brewery from Abendsberg in Bavaria’s Hallertau region has been brewing beer since 1609, making it one of the oldest breweries in Germany. In 2011, owner and seventh-generation brewer Robert Neumaier decided to install a completely new state-of-the-art brewing plant. Although various parts of the equipment had been replaced from time to time, the last general overhaul had been carried out by his great-grandfather as far back as 1906.
The brewery commissioned HKT Huber-Kälte-Technik GmbH in Halfing to professionally implement the cooling system and equip brew house and malt store with state-of-the-art refrigeration technology. The new brewery can process two brews per day with a total of 4,000 litres, with the complete brewing cycle taking about eight hours. A plate heat exchanger performs the function of cooling the hot wort from its boiling temperature (95°C) to a yeast pitching temperature of 7°C in the fermentation tanks. The primary fermentation, where yeast is added at 7 to 9°C, lasts eight days. The beer is then matured for eight to ten weeks. About 2,000 hectolitres of beer are brewed annually using this process.
When designing the new brewery, the focus was on energy efficiency and sustainability. In view of the output range of between 3 and 15 kW with direct expansion at -8°C, the refrigeration solution opted for an ammonia and dimethylether mixture (R723) as refrigerant. Adding DME to the ammonia shows the discharge temperature to be reduced by up to 25 K and achieves oil solubility. As a result, it is possible to build reliable direct expansion refrigeration units with air-cooled condensers, even where ambient temperature is 35°C. In this specific case, due to the brewery’s close proximity to its neighbours, the company opted for a very quiet stainless steel condenser supplied by Güntner with a sound pressure level of 36 dB(A) at 10 m, mounted on a special base frame above the compressors’ suction side to avoid noise. The higher suction gas density of R723 results in a 3 per cent higher efficiency than using pure ammonia. This means that even cooling systems with an output of less than 20 kW are suitable for operation with a natu
ral refrigerant. The brewery has achieved energy savings of around 40 per cent as a result of switching from bricked-in fermentation vats to free-standing directly cooled stainless steel fermentation tanks, changing the space cooling of the storage tanks to direct jacket cooling by glycol, replacing ice bank storage systems with single-stage plate heat exchangers with pre-cooled brewing water and using the natural refrigerant R723.
“The examples show that systems using natural refrigerants can now be used energy-efficiently and with minimal environmental impact in breweries of all sizes – even in the lower output range,“ says eurammon board member Georges Hoeterickx. “It always depends on the overall concept for a system, and the choice of refrigerant is one aspect of this.”