Warewashers are one of the kitchen's biggest consumers of energy, so manufacturers are working hard to make their machines as efficient as possible. Diane Lane reports.
As far as labour-saving devices go in a commercial kitchen, the dishwasher is hard to beat. But it's also one of the most expensive in terms of running costs, which is why the Catering for a Sustainable Future Group (CSFG) cites the wash-up as an area of particular importance when considering energy efficiency.
"All dishwashers require four components to work successfully - water, energy, detergents and time - all of which are expensive so any savings which can be engineered will save money and increase the economic, environmental and social bottom line," says David Clarke, a director of design consultants CDIS-KARM and CSFG founder.
"The calculation for heating a set amount of water over a given time cannot change: the amount of energy required will always be the same," Clarke adds. "Therefore the technology required for making dishwashing more efficient is to improve the insulation on the machine to maximise the heat generated, reduce the amount of water required per cycle, and recover the wasted heat that is discharged to atmosphere and drain."
Manufacturers are working hard to incorporate such technology into the design of their machines and some of the most effective cost-saving features are now standard across the leading manufacturers, says Bob Wood of warewashing specialists DC Catering.
"Choosing a machine that includes certain design fundamentals, coupled with a sensible machine management programme, will do as much as anything to reduce costs as the result should be a good balance between performance, running costs and purchase price," he says.
WASH TANK SIZE
The size of the wash tank is one such consideration, Wood says. DC Catering started developing smaller wash tanks in the 1990s and now has an undercounter warewasher that uses just 12 litres of water on first fill and claims to save as much as 13,000 litres of water per year. Insulation is another, so all DC machines are double-skinned with the Premium Range sporting additional door and cabinet insulation to increase heat retention.
Nick Falco, business development director at Meiko, is in agreement with Wood on the wash tanks point. "Manufacturers talk a lot about how they are reducing water consumption, when in fact the simplest way of saving water is to produce dishwashers with smaller wash tanks," he says.
Meiko's small machines are all produced with smaller wash tanks, which in turn use less water per wash cycle, less energy and produce less steam.
Falco continues: "Customers should also look at heat-recovery pumps, which when used in conjunction with a waste-air heat-recovery condenser continuously extracts hot air and the air around it - incoming cold water can be heated up to 70ºC. The heat pump then transfers this water to the rinse water heater where the temperature is raised further to 85ºC for final rinse process. The installation of a heat pump can negate the need for additional waste air extraction and also makes a contribution to a better work environment. Importantly, the pump offers a speedy return on investment owing to lower running costs."
Meiko's new M-iQ flight dishwashing machine offers heat recovery as standard with no need to purchase separate heat pump. Heat recovered from the washing process is re-used by means of a three-stage energy control system, ensuring optimum energy balance. Additionally Meiko is working to only produce machines that incorporate fully recyclable components - currently its DV80 hood machine is 98% recyclable.
Winterhalter's approach to energy efficiency has been to develop a range of new technologies under its IRT (intelligent resource technology) programme. For example, its GS500 Energy+ pass-through dishwashers reduce energy consumption by using heat exchange technology to recycle the heat usually lost through waste steam and wastewater. The company estimates that an Energy+ machine can save £1,250 per year in running costs. The machines also have a new rinse system with a rinse arm design that significantly reduces water consumption and therefore uses less energy to heat the water.
On its new UC Series of undercounter warewashers, Winterhalter offers an Eco option. This lengthens the wash time but cuts energy, water and chemical consumption, saving about 11% in running costs.
The objective for Classeq, part of the Winterhalter group, is to offer the most energy-efficient warewashers in the value-for-money, mid-budget market. Its Eco, Duo and Hydro glasswashers and dishwashers have wash tanks of 10 litres, 18 litres or 39 litres and a primary filter covers the whole of the wash tank, keeping the water cleaner for longer so operators don't have to drain down so often.
The new Duo 3, Duo 750, Hydro 857 and Hydro 957 models have the option of an integral water softener protecting the machine from damaging limescale build-up that degrades the efficiency of the heating system.
At Hobart, water- and energy-saving features are numerous, ranging from the 80Degree system, which reduces the volume of final rinse water required by 50% on its CP rack-conveyor and FTP flight-type machines, to Drain Heat Recovery on AMX and AUP hood-type machines, whereby the rinse water is heated from 15°C to 45°C using waste heat from hot wash water drained through the heat-recovery coil that surrounds the incoming water inlet pipe.
However, its latest development is rather more controversial. "One of the core new developments we've been focusing on is how higher wash temperatures can deliver not only a better result and faster throughput but also a reduction in water, energy and chemical consumption," says Tim Bender, warewashing product development manager at Hobart UK. "Raising the wash temperature to above 63°C within the patented Hot-Temp system greatly enhances cleaning performance and speeds up the wash process. Higher plate temperatures are achieved during washing, which means that lower rinse temperatures can be adopted."
"While this can be controversial, because many people believe that a hygienic clean is only achieved with a high-temperature final rinse, in actual fact it is the plate core and surface temperature at the end of the whole process that is most important to sanitisation. We are able to reduce both the volume and temperature of the rinse water, which leads to a significant reduction in the consumption of water, energy, detergent and rinse aid, delivering running-cost savings of up to 40%."
Executive training chef Alan Evans says that Electrolux Professional examines the full spectrum of consumption when it comes to warewashing, covering energy, water and detergent usage, to ensure that the customer is saving both energy and money at each stage of the product's use. He says: "Energy saving is a top concern throughout the entire lifespan of our products, right through to recycling. The green&clean range, including undercounter and hood-type models, offers machines that are at least 97% recyclable by weight."
"With reduced consumption, the green&clean models deliver up to 20% savings on running costs compared with standard machines. Low water consumption is achieved with the use of three litres of fresh water per rinse cycle as opposed to standard machines that use four litres."
Another approach at Electrolux has been to offer three standard cycles so that the right level of performance can be selected, with a short, medium or long wash cycle available to avoid unnecessary washing. Additionally, washing and rinsing cycle times can be fully customised to suit individual requirements.
At Miele Professional, product manager Malcolm Martin says it's important to take into account the usage context as well as the flexibility of use of the appliance as this can have a major bearing on the efficiency of the dishwashing operation.
"Miele's G7855 and G7856 models, offer efficiency benefits through maximising the use of basket space which cuts down on the number of washing cycles required for a load" he says. "Featuring two washing levels, the dishwashers allow both crockery and glassware to be washed during the same cycle, removing the need for additional cycles for separate types of tableware."
Also addressing cycle times, water usage and temperature, the G7855 has an 11-minute cycle duration that can clean up to 402 crockery items at one time as well having the facility to adjust the wash temperature, programme duration and water quantities. The G7856 also has the capacity to run a short seven-minute cycle and can wash up to 622 items in one load.
Kurran Gadhvi, marketing manager at Valera agrees that the issue of energy saving is as much to do with how the machine is used as anything else, although the Adler range of machines the company supplies has features such as double-skinned construction for less heat loss and variable time controls to help reduce running costs.
"While many manufacturers are producing better and more energy efficient machines all the time, the correct operation of a dish or glasswasher still remains one of the best ways of saving money, and with it, the environment," he says. "For example, if the sorting system is poorly designed, this can result in partially filled racks being washed, which means that money is effectively going down the drain. Remember, it costs as much in energy, water and detergent to wash a half-full rack of crockery as it does a full one."
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