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EXCLUSIVE Energy saving tips for food manufacturers

04 January 2013

This is the article that every food manufacturer MUST read: Tips from refrigeration and other energy experts about what food processors should be doing to cut costs and save energy.

Cutting energy is a priority for many food manufacturers. But what should you be doing to maximise your savings? David Strydom asked the experts for their opinions.

Energy efficiency is increasingly important as a way for food manufacturers to cut costs and save energy. As a result, many processors turn to those who can help in this endeavour - a recent example being a brewing company based in rural Herefordshire.

The brewer required cooling over the summer for its new storage facility in the South West so it contacted ICS Industrial Cooling for assistance. The brewer's beer kegs are stored in a converted barn that had reached maximum capacity so a 3,500 x 4,000 square foot store was built to cater for the increased stock.

The new store was set up with a water chiller and gravity coolers but lacked air circulation and the ability to provide stable temperatures in summer and winter. The temperature inside the warehouse was continually fluctuating and with summer approaching, it proved difficult to keep the temperature down. Further fluctuation could have resulted in an inferior product and potential losses for the brewery and its client.

With a required temperature of 10°C and no airflow, cooling equipment was desperately needed.

ICS sales engineer, Ben Newman recommended and supplied three units; a 71kW TAEevo351 chiller and two 25kW fan coils. Owing to limited space within the storage facility, the chiller was externally sited and connected to the fan coils that were fitted within the roof void.

The cooling system starts with the chiller which cools the water to the required 10°C which is then fed through to the coil and air from the fan is blown over it; circulating air throughout the store. The cold water is then fed back to the chiller from the fan coil, creating a water circuit. The TAE 351 is able to provide a range of temperatures between +20 and -20°C which manages changeable weather.

The chiller contains a large 350 litre buffer tank and circulation pump which draws from the tank to supply the incumbent cooling system. Only a small amount of space was required for the lightweight unit, which is built to a width of less than 1m to reduce the space required on site. The low temperature fan coils are flexible twin fan units, capable of offering 11,200m³/hr airflow. They were also supported with a condensate hose, real timer and defrost panel.

Owing to the site's rural location, a limited electrical supply to the new storage unit was problematic. To overcome this ICS fitted a softstart facility to the chiller which allows the unit to use staggered amounts of electricity as it starts up. This limits the amount of amps from being drawn on start up.

A simple remote control box, built by ICS's manufacturing company Tricool Thermal was installed allowing the customer to turn the units on or off by remote control. "The units have given us peace of mind, particularly during the summer months,'' said the brewery director. "We can easily maintain the required temperature throughout the year with full circulation. With the fan coil installed in the roof and a lightweight chiller, we had no issues with space," said the director of the UK-based brewery.

When asked what one energy saving tip he has for food processors, MD of ICS Cool Energy, Russell Wilson, says temperature control is an essential requirement for food manufacturers and one where a vast range of energy savings can be made. Heat recovery on cooling equipment such as chillers can be added as an option, which captures waste process heat and can be redirected to an additional source such as heating water for a secondary process.

"Thermo-regulators are a much more energy conscious alternative to boiler and steam systems in process heating applications,'' says Russell. "Their compact size and flexibility to be located close to the process element they're heating along with minimal pipes and valves, high insulation and usually only a small reservoir tank required - all contribute to the lower energy needs of the thermo-regulators to reach and maintain the temperatures required. They also cost considerably less to maintain and repair too.''

However, Russell points out, the top energy saving system for food manufacturers is 'Free Cooling' supplied by integral free-cooling chillers or through air-blast coolers. "Free Cooling reduces the energy inputs to cooling systems by allowing a process to use the naturally low UK winter ambient conditions to cool your process significantly reducing the power used to run a chiller compressor and prolonging the life of your chiller.''

Star Refrigeration recently launched a 'Don't Waste Your Waste' web campaign for food firms throwing away 'invisible energy'.

The heating and cooling specialist claims most food firms with refrigeration or air conditioning plants could be saving up to 40% on their annual energy bills. Star is launching a free online assessment through its website to help food processors identify where cost savings could be achieved by recycling 'invisible' heat energy.

"Heat energy is invisible, so understandably it's out of sight, out of mind for most businesses," says Star Refrigeration's director of sales - Food Market, James Ward. "Our key message is that when it comes to heating and cooling; 'don't waste your waste'. In most cases investing in heat recovery will significantly reduce energy consumption, cut costs and decrease carbon emissions."

He adds: "Cooling systems extract heat from food and buildings then reject the heat into the atmosphere as waste. Food firms can now recover, boost and recycle this waste energy and enjoy massive long term financial benefits, thanks to the latest industrial heat pump technology."

Neil Winney, Starfrost MD says: "Refrigeration is said to be one of the highest energy consumers in food processing factories. About 3% energy can be saved for every one degree rise in the refrigeration plant's compressor evaporating temperature. My top tip for food manufacturers is therefore to assess whether their refrigeration plant can operate at higher temperatures without any detrimental affect on the product.

"This may not be so easy where a common cooling plant is used for several outlets around the factory, but if the unit is dedicated to one piece of freezing or chilling equipment, it is often possible. For example if a spiral or tunnel freezer is fed from a dedicated refrigeration plant, an adjustment to the freezer itself could allow the plant to operate at elevated temperatures and thus save energy.

"The energy saving adjustments that can be made to an existing continuous freezing system include changing belt speeds to prolong freezing time, improving airflow efficiencies and changing product loading on the conveyor belt. All of these adjustments could allow an increase in the refrigeration plant's evaporating temperature and yet still freeze the product adequately.

"When a new freezing system is being installed, food manufacturers should select a refrigeration plant that will operate with a higher evaporating temperature in order to achieve a quick payback on investment. Operating efficiency can be improved by selecting a freezer with a slightly larger evaporator, more belt area to allow longer freeze times and inverters on fans. Food manufacturers should also choose a flexible system designed to operate with optimum energy efficiency, even if the production line is running at less than full capacity in the future."

With respect to energy saving tips, Robert Unsworth, director of product development for GEA Refrigeration, says food processors should use floating condensing pressure control in their refrigeration plants.

"On a refrigeration system, heat transfers to cold,'' he explains. ''So you take the heat out the product and the room, into the refrigeration plant. Now let's say you've taken 1,000kw of heat out the building through the refrigeration plant. That heat travels through the refrigeration compressor and energy is put into the compressor to drive it.

"You'll stick 250kw of energy into that so what goes into the refrigeration system on the discharge side is both amounts, which equals 1,250kw of heat. That is the heat we can recover via a heat pump. If you want heat, we can recover that and return it to your system as - for example - 60 or 80 degree hot water, which means you don't have to run your boiler generating 1,250kw.

"If you don't use that system, you'll discharge 1,250kw at your condenser, a large radiator on the roof that blows the heat into the air (and on larger systems using water and chemicals to boot). Because the refrigeration system is designed for summer, it will transfer the heat when the air temperature outside is, say, 30°C, so the 'condensing temperature' (the temperature at which the heat is ejected from the system) is, for example, 40°C - a 10°C temperature difference over the condenser.

"The way the refrigeration plant is controlled is via a pressure switch that tells the condenser fans to switch on and off based on that condensing pressure of 40°C. But this is regardless of the temperature outside, which may be 10°C, for instance. That pressure switch is still set to condense at 40°C so what happens is all the condenser fans slow down or switch off, so you save power on the condenser.

"But the refrigeration compressor with the 250kw motor on is still compressing the gas up to 40 degrees. Every one degree you lower that temperature, you save 3% power so if it's 10 degrees outside and you can condense at 20°C, you've saved 20°C, multiplied by 3% per degree, gives you a 60% energy saving on a 250kw motor."

Stephen Takhar, MD of Vacon Drives says, while it may not be a new suggestion, the best way to save energy is to carry out a factory inspection to see whether pumps and fans are fitted with variable speed drives (VSDs). ''If they're not," says Stephen, ''you could be missing out on significant energy savings.

"Pumps and fans have to be sized for worst-case conditions so, if they run at fixed speed, most of the time they're doing a lot more work than is necessary, which gobbles up energy. Remember if you reduce the speed of a fan by just 10%, the potential energy saving is well over 25%. Don't be tempted to wimp out by saying VSDs are too expensive or that there's no space to accommodate them.

"In many cases, a VSD will pay for itself and in just a few months - after that, it's savings all the way. And if you really think you haven't got space for VSDs, you probably haven't seen the latest tiny compact drives or the convenient motor-mount units that, as their name implies, mount directly on your motor. So don't delay, start fitting VSDs today and watch those savings grow!''

Lester Young from Siemens Industry says water usage accounts for a significant proportion of food manufacturing costs, as it forms an integral part of operations for the industry. "In today's challenging marketplace, optimising water usage is something plants cannot afford to overlook,'' says Lester.

"Through simple measures that smarten up operations such as reducing leakage and cutting workplace wastage through to water recycling, there are significant gains to be made in terms of environmental performance and impacting positively on the bottom line.

"Before considering water recycling options, plants should first look to reduce a site's water usage. Up to 70% of the world's fresh water usage is used for agriculture and it takes more than 10 gallons of water to produce just one slice of bread, so there's vast savings to be made. Start by simply looking at where wastage may be occurring by analysing overuse, such as staff wastage and checking for leakage through damaged or ageing infrastructure.

"Plants that are in control of their usage can then consider options for water recycling. If there is a suitable use for recycled water, the next step is to assess which technologies will enable this usage and will ensure the plant is as operationally efficient as possible.

"It is vital to choose a system that meets each plant's specific operational needs and one that guarantees every drop of water is in compliance with legal, corporate and consumer demands - for today and tomorrow. For all stages of the process it is advisable to engage with a water treatment expert who can ensure solutions meet the plant's exact needs."

Paul Mayoh, Spirax Sarco's UK product marketing manager says steam is the most energy efficient, reliable and flexible way to transfer heat for many food and beverage operations. However, a lack of in-house expertise and resources to undertake boiler house and steam distribution system maintenance may mean food and beverage companies are losing up to a fifth of their production process energy.

"Advances in modern steam system energy recovery processes means that with little investment, food and beverage manufacturers can significantly cut these losses, reducing carbon emissions and utility bills,'' says Paul.

Many applications can benefit, including treating contaminated condensate so it can be returned to the boiler; recovering exhaust heat, flash steam and process hot water; CIP heat recovery; cooling tower heat recovery; and effluent heat recovery.

"A recent example of this is Heinz, which is saving 6% of its average steam load per year at its baked bean factory in Wigan by recovering energy from effluent. Blanched water was purged regularly to maintain the necessary quality. However, instead of being disposed to drain, an effluent recovery system now intercepts it and uses it to help heat the blanching process, recovering around 1,500 kW and saving around 473 tonnes of carbon emissions a year.''

Paul O'Neill of Atlas Copco Compressors says the use of oil-free variable speed drive (VSD) compressors is highly recommended as a way for food manufacturers to save energy, reduce the risk of contamination and improve compressor performance.

"In 80% of installations, air demand shows fluctuations, meaning there is a large potential for energy savings if VSD compressors are used. VSD compressors use an integrated frequency inverter that varies the speed of the compressor motor to match its output to the air demand.

''This can provide energy savings averaging 35% as the supply meets the demand. The use of oil-free VSD compressors also ensures a guaranteed, quality supply of compressed air in food and beverage production environments where product end quality is a crucial consideration.

"In addition, oil-free VSD compressors can deliver air at a lower pressure compared to oil-lubricated compressors, which have to overcome pressure drops in the oil separators and inline filters. An oil-free system can typically run at 1 to 1.5 bar lower than an oil-lubricated system and reducing pressure in a compressed air system by 0.5 Bar can reduce energy consumption by up to 3%, so potential savings for food manufacturers can be significant.''

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