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Energy-effi­cient fans for refrig­er­a­tion tech­nology

Sample calcu­la­tions for refrig­er­a­tion and air condi­tioning equip­ment found in super­mar­kets

From 2013 onwards, the ERP (eco-design) direc­tive will enter into force for fans, This direc­tive pursues in partic­ular the objec­tive of improving the energy effi­ciency of prod­ucts and thus to realise Euro­pean climate protec­tion targets. For many elec­tri­cally powered fans in use in refrig­er­a­tion and air-condi­tioning tech­nology, this means that they will have to satisfy the statu­tory limits stip­u­lated in this direc­tive. The result is a twin benefit: Impact on the envi­ron­ment is reduced and poten­tial energy savings are felt in the pocket of the consumer. The sample calcu­la­tions described below apply to refrig­er­a­tion and air condi­tioning equip­ment typi­cally found in super­mar­kets and they supply the neces­sary proof.

Since air-condi­tioning and refrig­er­a­tion systems are oper­ated with high duty cycles, energy savings are partic­u­larly notice­able in this area. However, there are consid­er­able differ­ences between appli­ca­tions. For example, the large condensers that are usually attached to the outsides of super­mar­kets have different require­ments to the fans that are used in refrig­er­a­tion coun­ters and refrig­er­a­tors. For each of these fields of appli­ca­tion, “customised” energy-effi­cient EC fans now exist that feature outstanding reli­a­bility, maximum effi­ciency and low-noise perfor­mance.

Better than what is “required”

The broad product port­folio of the motor and fan specialist ebm-papst includes energy-effi­cient fans for prac­ti­cally every power range that could be used in refrig­er­a­tion and air-condi­tioning tech­nology. Even today they already exceed by far the effi­ciency values stip­u­lated in the ERP (eco-design) direc­tive. Thanks to the successful inter­ac­tion of motor tech­nology, elec­tronics and aero­dy­namics, EC fans do not just convince with respect to their energy effi­ciency. They also work extremely quietly thanks to their opti­mised commu­ta­tion tech­niques and the aero­dy­namic config­u­ra­tion of the impellers. And on top of every­thing, they also convince with their dura­bility and reli­a­bility.

In refrig­er­a­tion and air-condi­tioning tech­nology, the change to modern EC tech­nology is worth­while on many accounts, espe­cially as the stip­u­la­tions of the direc­tive are not only ecolog­i­cally rational, they are also econom­i­cally highly inter­esting for the user. Even on compar­a­tively small refrig­er­a­tion units, the low energy consump­tion can bring about substan­tial savings compared to conven­tional fans that usually work with shaded-pole motors. One example is the so-called bottle coolers that can be found every­where where chilled drinks or snacks are sold, from kiosks or filling stations to super­mar­kets.

Energy-saving motors for refrig­er­a­tion units and coun­ters

Compar­ison of ESM/shaded-pole motor curves

If, for example, there are two fans fitted in a refrig­er­a­tion unit that are powered by conven­tional 30W shaded-pole motors, and if these are in oper­a­tion 12 hours a day, they will consume around 262 kWh in a year. However, if the fans were to be oper­ated with energy-effi­cient 10W EC motors from the energy-effi­cient ESM motor line from the ebm-papst product range, which boast the same air perfor­mance, this consump­tion would fall to about 88 kWh. There are two reasons for this: Firstly, the effi­ciency of the EC motor is vastly supe­rior. At the oper­ating point with a typical speed of 1300 rpm, the energy-saving motor has a maximum effi­ciency of more than 65%, allowing power input to be reduced by around 1/3 compared to a conven­tional shaded-pole motor. Secondly, less energy needs to be consumed from the very outset for the cooling process because less heat is lost to the envi­ron­ment during oper­a­tion.

From the resulting differ­ence in energy consump­tion of 174 kWh and assuming a price for elec­trical power of 11.69 euro cent/kWh (average elec­tricity price for industry in Germany, status January 2010 / Source: VEA, BDEW), there is an imme­diate annual saving of about 20 euro for each refrig­er­a­tion unit. The energy-saving solu­tion thus enables payback periods of less than 12 months. That makes this invest­ment worth­while not just for the envi­ron­ment, but also for the wallet of the user, espe­cially when the compa­rably long service life of the EC fans (approx. 40,000 oper­ating hours) is taken into account.

Savings poten­tial by the metre and straight­for­ward conver­sion

Energy-effi­cient tech­nology for refrig­er­a­tion coun­ters: energy-saving fans as a system solu­tion for refrig­er­a­tion coun­ters (left), IQ motors allow a straight­for­ward 1:1 exchange of the conven­tional shaded-pole motors for effi­cient cooling (right)

The more fans there are in oper­a­tion, the greater the savings poten­tial. Refrig­er­a­tion coun­ters are a good example. There are usually two fans for every metre in length. In a typical super­market, there are some 100 m of refrig­er­a­tion coun­ters, making 200 EC energy-saving fans of size 200. The energy saving compared to conven­tional shaded-pole motors is 70%, equating to 38 MWh per year. For the envi­ron­ment, this means more than 22 tonnes less CO2 being produced on the basis of today’s energy mix. At the same time, the user will save more than 4,400 euro at an elec­tricity price of 11.69 euro cent/kWh.

By no means are users only able to benefit with new instal­la­tions. A conver­sion of existing instal­la­tions is possible and straight­for­ward. In this case, ebm-papst offers energy-effi­cient iQ motors, which are mechan­i­cally compat­ible with existing shaded-pole motors, and which have a high effi­ciency of up to 65% and the same instal­la­tion dimen­sions, allowing a straight­for­ward 1:1 exchange. Axial impellers with a diam­eter of 154 to 254 mm can be fitted in the same way on the iQ motor to create an energy-effi­cient solu­tion. The intel­li­gent elec­tronics regu­late voltage fluc­tu­a­tions so that the speed remains constant. Today, count­less well-known super­market chains are making use of this ecolog­i­cally and econom­i­cally rational 1:1 exchange option.

High-perfor­mance energy-saving fans for condensers and evap­o­ra­tors

The indi­vidual curves illus­trate the power input of controlled AC/EC motors in compar­ison

Compa­rable energy savings can be achieved in many other appli­ca­tions. For example, ebm-papst has set stan­dards with its energy-effi­cient HyBlade® fans for condensers and evap­o­ra­tors. Thanks to modern EC tech­nology and aero­dy­nam­i­cally opti­mised vane geom­etry, the EC fans, which are avail­able in sizes 172 to 990 mm diam­eter, convince with energy savings of up to 50% compared to AC fans. This applies not only in full-load oper­a­tion, but also and espe­cially in partial-load oper­a­tion. In addi­tion, the speed can be controlled for EC tech­nology. In other words, it can be adjusted to the respec­tive cooling require­ments, which provides further poten­tial savings. The result is substan­tially lower energy costs which are quickly felt in prac­tical oper­a­tion. The different curves illus­trate the power input of controlled AC/EC motors in compar­ison. In all speed ranges, energy costs are vastly lower with EC motors than with voltage-regu­lated or frequency-inverter-fed asyn­chro­nous motors. Depending on require­ments, between two and twelve of these fans are typi­cally used in such condensers.

Example of a schematic illus­tra­tion of compo­nents on a condenser

If you take a condenser with six HyBlade® axial fans of size 800 with EC tech­nology and compare these with six AC axial fans in the same power cate­gory, each with an air perfor­mance of 11,000 m³/h at 85 Pa, the six AC fans will need a total of 5,400 W, while the EC fans will have a power input of just 3,900 W. In this instance, the EC fans consume a total of 1,500 W less energy, repre­senting a saving of 28%. Further savings can be achieved by simply networking the EC fans via a BUS system, linking them to the higher-order manage­ment systems (see Fig. 7). Low noise levels, dura­bility and the low weight resulting from the robust plas­tics used are further bene­fits of these axial fans. In addi­tion, the inte­grated power elec­tronics are config­ured for country-specific mains volt­ages, allowing world­wide use, regard­less of whether the power frequency is 50 or 60 Hz.

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