One of the quickest ways to improve the efficiency and capacity of your refrigeration system, saving energy and money, is to reduce condensing pressures. According to the Carbon Trust, for every 1°C reduction in condensing pressure, you can lower running costs by between 2˚C and 4°C.
This does not necessarily require a big investment — you can often reduce the head pressure, and therefore the condensing pressure, by adjusting the control settings on your existing equipment. “Most systems have the capability to do that – they just need to be optimised,” says Jason Shilliday of Shilliday Refrigeration.
Once systems have been set to the optimum pressure, basic maintenance is important, such as ensuring that condensors are not located in hot spaces or in direct sunlight, and checking that condensor coils are cleaned regularly and not caked with dirt. Evaporators should also be placed carefully and kept clear of ice.
For those willing to invest, recent developments in technology can deliver even bigger energy savings. “What we can do is reduce the amount of power that the compressor uses by floating the head pressure to go up and down with ambient temperature. So if the ambient temperature goes down, the head pressure goes down,” says Shilliday.
This ‘floating’ of the head pressure is known as Liquid Pressure Amplification (LPA) and, according to refrigeration company Excalibur LPA, it is not unusual to see condensing temperatures reduced by 15-20% following the installation of an LPA system, with annual efficiency improved by 30-40%. Further cost reductions can be achieved as a result of reduced wear and tear, due to lower compressor operating pressures and temperatures, the company says.
Condensing pressures aside, plant operators should ensure they are not packing carcases into under-sized and under-capacity chillers. “If your refrigeration system is under-capacity and you are killing a significant amount in hot weather, all of a sudden you can overload the system and you will pay the price,” says Christine Walsh of MLCSL Consulting.
Chiller doors are another big consideration. It is estimated that leaving a door open for 30 minutes will increase the heat load by up to 15%, increasing risk to the produce inside. “It is extremely important to maintain temperature levels. If the temperature rises even slightly, not only can produce be easily damaged, which would be costly, but it could also damage the cold store, leading to costly repairs,” says Shaun Evers, managing director at Stonegate Instruments. Leaving a door open can also increase energy costs – MLCSL Consulting estimates that for every hour a chill room door is left open, it can add energy costs of approximately Ł250 per year.
One option for reducing energy loss, while allowing the entry and exit of product, is thermal curtains, which prevent some of the cold air from escaping. One of the most efficient of these is the Cold Stop Curtain, manufactured by Seymour Manufacturing International (SMI). Brian Seymour, chairman of Seymour Manufacturing International (SMI), says the curtains are made out of a specially developed, lightweight material called Tempro®, which is “possibly the most thermally efficient material in the world”.
According to tests carried out by SMI and confirmed by Campden BRI, Cold Stop Curtains can save 2,767kg of carbon a year on a metre-wide freezer. “In layman’s terms that means you could drive an average saloon car for 12,000 miles and that is equal in carbon,” says Seymour. “That is something like a third of their energy costs; we are saving 33-37% of their energy in a freezer. That is one hell of a lot of carbon.”
Cold Stop Curtains are now also available on refrigerated trucks, helping save considerable energy when meat is in transit. “We also noticed enormous losses from the backs of delivery vehicles, typically multi-drop vehicles,” Seymour explains. “We now have a product called Back Stop, which is like giant Cold Stop curtains on the back of a vehicle. It is very useful and user-friendly because you don’t have to worry about closing them. They are held in place by an electromagnet and released by the guy just tapping or knocking the button with his elbow, which will then close the door. It looks as if it will save enormous amounts of energy.”
Another way to optimise temperatures for energy efficiency and hygiene is by installing control products. Temperature displays and alarms can be used to monitor temperatures, with a thermistor probe raising an alarm if the temperature moves outside a preset range. ‘Door open’ alarms are also available, giving off a warning if doors are left open for a prolonged period of time. “Refrigeration control products vary rapidly and can be adapted to suit specific locations,” says Evans. “It is crucial that expert advice should be sought by cold store operators to ensure the best technology for the cold store is implemented, and the produce that will be primarily stored there, are used.”
In addition to optimising the efficiency of their refrigeration systems, plant operators can save money by using heat wasted during the refrigeration process to heat hot water. Traditionally, there have been some problems with heat recovery technology, because in order to get high temperatures, you have to run condensors at high pressures, which is inefficient.
“In the UK, heat recovery has fallen out of favour, because to recover energy at sufficient temperature, the compressors have to be operated at high head pressures, which reduces refrigeration efficiency,” says Excalibur’s managing director Gareth Holden. “Perceived wisdom has been that refrigeration should be operated at optimum efficiency and water heated from another efficient source.”
However, Excalibur has recently patented a new type of heat recovery system, developed with help from the Carbon Trust Entrepreneurs’ Fast Track Scheme. The company claims the system allows the refrigeration to operate efficiently at low condensing temperatures, while delivering water at 55°C, and says that, in many cases, the entire hot water of a site can be satisfied in this way.
Energy efficiency is not just an issue at the processing stage — it is also important during the retailing of meat. “It is reckoned that around 50% of electricity consumed in supermarkets is attributed to refrigeration, and even more in smaller shops,” says refrigeration specialist Husky’s chief executive Geoff Thomasson.
Suppliers to this sector have also made step-changes in the technology available to control refrigeration and conserve energy. “The best products are able to ‘think’ for themselves, sensing when activity eases off and switching to economy ‘night mode’,” explains Thomasson. “When the unit identifies increased frequency of cabinet doors being opened and closed, it kicks back into life, keeping temperatures at a safe and steady level.”
As with processing, one of the easiest ways to reduce refrigeration energy during retail is to shut the door. “There is a trend towards glass-fronted units, and away from the more traditional ‘open’ refrigerator displays. This means cold air is used to chill the food, rather than the whole supermarket aisle,” Thomasson says.
Whether at processing or retail level, suppliers and refrigeration experts agree that the best way to save costs in the future is to invest in the right equipment now. “Many buyers are either ignorant of this at the time of purchase, or are so seduced by the salesman’s pitch — ‘look at the price, not the running costs’ — that they become blind to the facts staring them in the face,” he says. “Money spent wisely brings financial gains on a daily basis.”
With increasing concerns over the environmental damage caused by refrigerants, the Europe Commission is introducing stringent legislation controlling their use.
Meat processors should be aware that the final deadline for the use of hydrochlorofluorocarbon (HCFC) R-22 is fast approaching. A ban on the gas has already been introduced (January 2010) and the concession on use of reclaimed product will expire in January 2015.
The most common alternative to R-22 is hydrofluorocarbons (HFCs), which are F-gases. However, these gases have a high global warming potential (GWP) and, on 4 July 2011, new legislation governing their use came into force in Europe. The regulations require all those who operate HFC-based refrigeration or air conditioning systems above a certain size to carry out regular checks and repair leaks; failure to do this could lead to prosecution and fines. “It is vital that everyone who uses this equipment gets rapidly up to speed with the new legislation. We understand the authorities are gearing up to take more concerted enforcement activity, and that prosecutions may follow,” says Iona Spencer of the Air Conditioning and Refrigeration Show.
Environmental groups such as Greenpeace are pushing for F-gases to be banned altogether, although Barry Lyons, business development manager for BOC, says this is “not realistic”. There are some alternatives to HFCs, namely natural gases, but these all have problems, he adds. “Ammonia is toxic and explosive in the right conditions, CO2 works at very high pressures compared to what the industry is used to and hydrocarbons are flammable and explosive.” For meat plants looking for ‘go natural’, Lyons recommends ammonia — used by the industry for years — but warns: “There are certain things you have to do, which you didn’t used to have to do, such as installing leakage alarms and isolating units in a plant room away from staff.”
Natural gas is also expensive to install, requiring a whole new system. Smaller plants should therefore investigate use of F-gases with lower GWP, such as R134. The latter has a GWP of 1,300, which means that every kg of R134 released into the atmosphere is equivalent to releasing 1,300kg of carbon dioxide. This is considerably lower than other F-gases, such as the more commonly used R404A, which has a GWP of 3,900.
Case study: Shilliday
Shilliday Refrigeration won the prize for ‘Industrial and Commercial Project of the Year’ at the RAC Cooling Industry Awards for its installation of an energy-saving refrigeration system at Loughall meat processor Hewitt Meats.
Shilliday’s technical director Jason Shilliday explains: “Hewitt Meats was looking to upgrade its refrigeration to a more energy-efficient system and it also had R-22 gas in some of its systems, which needed to be replaced.”
Natural gas options, such as an ammonia plant, were not suitable for a small processor like Hewitt, so Shilliday converted the system to run on R134A, a refrigerant with lower global warming potential than other F-gases, which can be put into high-efficiency compressors. “The cost of an ammonia system would just be astronomical… so a better solution for Hewitt was to use some of the existing evaporators on-site and just upgrade the plant into the most efficient F-gas system you can get, which was R134A eco line compressors.”
Shilliday installed four R134A compressors with a total capacity of 162kW. Electronic expansion valves, EC fans on condensers and evaporators and RDM controls were added to the system for improved efficiency and the team installed a Eureka PTS system, which can recover 140 litres of hot water per hour from two freezers on-site. The installation resulted in a 19% drop in Hewitt’s energy bill over the period of a year, with a carbon footprint reduction estimated to be at least 80 tonnes a year.
Speaking after the RAC awards, director of Hewitt Meats James Annett praised Shilliday, saying: “Shilliday’s new system is easily managed and has resulted in us saving money and energy.”
But Shilliday says the success of the project was down to the processor’s willingness to invest. “It is not often that you get a client who wants to invest in the equipment. A lot of clients just want the cheapest thing you have, but if you get a client who is willing to trust you and go for the high-efficiency stuff, which is more expensive, you do get payback on it.”