Fullscreen HTML5Med Res (??MB)HTML4

Can you really reduce your electricity bill? By JOHN CAMERON* With recent large increases to commercial and domestic electricity tariffs and promises of more to come, everyone wants to know how to reduce their electricity consumption. This can be done but it is neither simple nor easy. In this article we will review some strategies for saving power – and debunk some of the scams around! T he review of the FutureWave Energy Saver for swimming pool pumps in the June 2011 issue of SILICON CHIP has created a lot of interest. It really does work, unlike most energy saving gadgets promoted to an uninformed public. There are two main types of energy ‘saving’ devices sold over the Internet, at flea markets and unfortunately, by some retailers who should know better. Most are so-called power factor correction devices or devices which are claimed to “clean up” or otherwise fix your “dirty” or “unusable” power. These provide no benefit to domestic consumers and have been frequently discredited. (See the November 2007 and May 2008 issues of SILICON CHIP). Less common power saving products are voltage reduction devices for electrical motors. They vary the voltage to the motor, depending on the load. More on these devices later. Possibly some readers may have suspected that the FutureWave device reviewed in the June 2011 issue was just another device varying the voltage fed to the motor. But the review gave a different picture. It is intended for controlling swimming pool pumps which are driven by 22  Silicon Chip induction motors. The FutureWave reduces the supply frequency fed to the motor, as well as manipulating the voltage and waveform. The end result is reduced motor power consumption while still providing adequate torque and power output. This is the real advantage of the FutureWave compared to anything else on the market. It was determined by the developers of the FutureWave Energy Saver, after studying pump curves and graphs of pool pumps and much testing, that dropping pump speed below 1700 RPM, the resulting flow rate drops is not adequate for effective filtering. Hence the lowest flow setting on the FutureWave is 31.5Hz, giving a pump speed of around 1800 RPM (for a 2-pole induction motor with a nominal speed of 2850 RPM) and allowing flow rates to be maintained to adequately maintain filtering and cleaning performance. On average. this will provide a power saving of about 70%, Where do the savings come from? The savings come about because swimming pool pumps are over-specified for normal water filtering. The FutureWave provides large savings by reducing the flow rate through the pool’s plumbing to a rate better suited for efficient pumping and filtering. So why is the pump not the ideal size for normal water filtering? It is basically because a larger pump with enough power output is required to prime the pool’s plumbing system, run The FutureWave Energy Saver was reviewed back in the June 2011 issue. It’s one device which really can cut your electricity bill if you have a pool! siliconchip.com.au a pool cleaner and provide adequate flow to perform backwashing. The FutureWave allows the pump to prime the pools plumbing system before its energy saving mode kicks in. It will then reduce the power consumption whilst providing adequate flow rates to operate the pool cleaner (eg, Kreepy Krauly). A pump has to be able to pump 120-180 litres/minute against a reasonably high ‘head’ (eg, the depth of the pool plus height of pump above the pool) to keep the cleaner operating. When the cleaner is not in use, ie, when the pool water is simply being filtered, the pump does not slow down. It continues to pump hard, forcing lots of water though the system. This is not efficient because the friction loss in the PVC pipes of the typical swimming pool rises as roughly the square of the water flow. So when you double the flow rate the friction loss of a system increases by a factor of four. In other words, you need four times the power to pump 240 litres/minute around a pool system compared to 120 l/min. This was seen with figures given in the June FutureWave article. A 40% reduction in motor power frequency and thus water flow gave over a 60% reduction in power consumption. Halving the water flow rate would give a 75% reduction in pump energy needs. In effect, the FutureWave Energy Saver converts a normal swimming pool pump into a variable speed pump that can be scaled to better meet water pumping requirements, giving energy savings when high water flow rates or pressures are not needed. Variable speed pumps So why not simply use a variable speed pump? In fact, they are available, from most swimming pool shops. A typical example is the Hydrostorm ECO which has three speed settings (2850 RPM, 2410 RPM and 1900 RPM) and which according to waterco.com.au can slash its energy use by up to 67%. It costs about $1,200. See: www.waterco. com.au/pool-spa/11-hydrostorm-ecothree-speed-pumpThere are a range of other variable speed pumps including the Zodiac FloPro ePump which has up to eight different speeds (www.zodiac.com.au/ products/pool-pumps/flopro-epump) siliconchip.com.au The all new ‘Dual’ Future Wave Energy Saver We looked at this “Electicity Saving Box” back in November 2007 and proved it wasn’t even worth the box it came in . . . nothing has changed, except now there are lots more of them around. Don’t believe the claims: they’re a con! and the HurlconViron P300. See www.rodepools.com.au/content. php?pageid=1276835758 These variable speed pumps all use brushless permanent magnet motors which are driven by switchmode controllers. Not only do they have the advantage of lower power usage, they are also substantially quieter than typical pumps driven by induction motors. That gives a further advantage in that they can be run from off-peak power at night without disturbing neighbours. We should note that the developers of the FutureWave Energy Saver have pointed out that “while variable speed brushless DC motor driven pumps may claim over 70% savings, they also mention that at the reduced pump speed (600-800 RPM) the flow rate is reduced to 80-100 litres/minute, well below the required flow rate for a filter and cleaner to perform adequately.” From talking to people in the pool industry it appears that customers are reluctant to spend more on variable speed pumps or on water filters, above the minimum required. The initial cost is an issue. A regular 750W (1 HP) pump typically costs about $400-500 and a 1.5HP unit only slightly more. Compare that to a new variable speed pump which costs $500 to $1000 more to install. In the past the running costs have not been a major concern to customers at the time of the pool or pump purchase. Following on from the highly successful single connection Future Wave Energy Saver a dual unit has now been developed and released. Feedback from pool owners was highlighting the growing concern that a lot of pool owners are running more than one pump to maintain and run their pools. Along with the main filter pump, pools are running extra pumps for such tasks as solar water heating or to run their pool cleaning systems. Running extra pumps of course means more energy usage and higher costs. The Dual Future Wave has been developed with this in mind. The option prior to the Dual unit was to either have a separate Single Future Wave on each pump or maybe only run one Future Wave on the main filter pump as it typically runs longer and subsequently higher electricity costs. The Dual Future Wave now offers a costeffective way to address this concern. The Dual unit allows the filter pump to be connected to the ‘Pump 1’ side with the second pump connected to ‘Pump 2’ and can provide control over ‘Pump 2’, not allowing it to start unless ‘Pump 1’ is running and also a time delay. This is critical for solar pumps or cleaner system pumps where they rely on the main filter pump be running to operate. The Future Wave Energy Saver (Dual & Single) with its ‘Flow Adjustment’ setting allows the pool owner to perfectly match and achieve the maximum energy savings to the required output or flow rate of each pump that it runs. Please refer to the advertisement at the end of this article for pricing and contact details. September 2011  23 Hydrostorm’s ECO pool pump and filter – it looks similar to most standard pumps but features a variable speed motor. But with skyrocketing electricity costs, that is now changing rapidly and people are likely to be far more sensitive to electricity bills. In practice many pools would be better cleaned if they had a larger filter and a smaller pump. Filtering works best at lower flow rates. We understand that Sydney pools typically use 1HP pump motors with 1.5HP motors being mainly limited to 80,000 litre and larger pools. It is also possible to separate pool filtering and cleaning. Pool water filtering can be done with a smaller pump, typically 0.5HP, with the automatic pool cleaner running off a booster pump when required. Finally, for the lowest energy consumption, swimming pool shops sell a number of electrically-driven pool cleaners (often described as pool cleaning “robots”). These are powered by 24V DC motors and are very energy efficient. They typically draw about 100-150W when running. A low-voltage (24V DC)swimming pool “robot” cleaner. They’re claimed to save money because they are not reliant on a large pool pump working hard to control them. They are suitable for all sized pools including large commercials. 24  Silicon Chip Similary, the Hurlcon Viron P300 also sports a variable speed motor. At about $965 it’s not cheap but claims power savings (at 2010 prices) of up to $700 per year over conventional (ie, constant speed) pumps. Overseas experience Oversized pool pumps are not just an Australian problem. In a study of 120 pools by the USA Center for Energy Conservation at Florida Atlantic University, some pool owners saved as much as 75% of their original pumping bill by replacing large pumps with smaller pumps and by simply reducing running time. The study showed that a 0.75 horsepower (600 watts) or smaller pump is generally sufficient for residential pools. By the end of this year Florida will ban the sale and professional installation of single-speed pumps of one horsepower or greater for domestic swimming pools. Also, California has, as you would expect, a large number of swimming pools and has studied pool energy requirements in detail. See www.energy. ca.gov/title24/2008standards/prerulemaking/documents/2007-02-26-27_ workshop/supporting/PGE-DRAFT_ REPORT_RESIDENTIAL_SWIMMING_POOL.PDF In summary, the most economical pool system is one designed for efficient water flow and fitted with a variable speed motor. The simplest option for most people would be to reduce the filtering run time for their existing pump as far as possible and when the pump motor is next replaced install a multi-speed motor. er electrical consumption, frequently with impressive university reports setting out the electricity savings. But whether these devices actually save money is another matter. They are intended for use with AC induction motors. They work by monitoring the motor and lowering the voltage when the motor is lightly loaded. The monitoring technique was developed by NASA engineer Frank Nola to lower energy consumption in motors and fans on NASA-built vehicles. NASA still lists it as a NASA technology spin-off. Details can be found on the NASA web site www.nasa.gov This concept generated a lot of interest during the 1990s and there were many manufacturers of these devices, claiming spectacular savings. In simple terms, the device monitors the motor’s load by measuring the power factor and then uses some sophisticated electronics to control the voltage to keep the power factor constant even as the load changes. This reduces the losses in the motor when the motor is lightly loaded. Lowering the voltage of a synchronous motor does not change the motor speed but does reduce its torque. The cleverness in Nola’s work was how he used power factor changes to automatically determine the required The Blue Diamond robotic pool cleaner is claimed to clean the average pool in about three hours. It operates from 24V DC and consumes about 120W – a fraction of the power of pool pumps. Energy saving devices As already noted, simple capacitorbased power factor correction boxes do nothing in a domestic environment as far as power saving is concerned. But other devices can appear to lowsiliconchip.com.au voltage adjustment so that power increased when more torque was needed. Microprocessor-based integrated circuits are available to handle the device smarts, for example the Microchip MTE1122. A typical device sold to the public for domestic appliances is the Reegen uPlug power saver, marketed widely around Australia in 2009. Results on unloaded motors using this device can be impressive. For example, tested it with a 0.3 HP drill press motor, readings fell from consuming 190W to 145W, an apparent 25% reduction. But operated under heavy load – in other words, working as intended– it showed NO power saving. In a domestic environment they do not save money. Tested on a wide range of devices such as refrigerators and washing machines, there are minimal electrical savings on most devices because their motors are already running at close to full load. In fact, the claimed savings all seem to be on motors running with no load. Details of some studies of these devices with a range of motor sizes can be found at http://home. clear.net.nz/pages/lmphotonics/es090698.pdf Refrigerators are an interesting case and show that simply measuring the power consumption (ie, watts) can be misleading. I have tested refrigerators that show a 5-10% power saving on a commercial wattmeter. But when total energy used over 24 hours is measured there is no saving. This is because the refrigerator simply ran for longer times when on the energy savings device. It still had the same amount of work to do to cool the contents. In summary, these devices provide no benefit in the normal home, especially as they typically cost $200 to 36 days of free electricity per year!* Eliminates 100% standby energy of all connected appliances Easy access – ecoswitch® can be placed within easy reach: no bending, straining or forgetting Easy to use and install – even for the elderly and disabled Pay-back period for the average household is less than 26 weeks* Save over $120 per year off your electricity bills* Save over 800kg of carbon dioxide per year* Reduces fire risk Longer life for appliances Control your appliances from a new easy location of your choice No electronics inside to fail or emit nasty electronic noise Safer than an ordinary extension cord Double sided tape and clips keep cords tidy Works with all 240V appliances (full 10 amps capacity) 12 month warranty Unlike other energy saving devices, the ecoswitch®: Doesn’t require programming, a remote control, or batteries Can be used with your existing powerboard/s Has a special flat plug that lets furniture sit closer to the wall *estimated using 3 units per household Visit www.ecoswitch.com.au for more information, or contact us at sales<at>ecoswitch.com.au Factory is ISO9001 certified. Approved to Aust/NZ standards . Patents Pending. Carbon Reduction Industries Pty Ltd ACN 128 270 388 ECO004 FastFacts.indd 1 7/10/2010 5:11:44 PM The Micro Plug Power Saver: first released a couple of years ago, these were supposed to connect to electric motors and save you money. Did they work? On motors with no load, yes. But how many motors run with no load? At $198.00 each, your grandkids (or theirs) might see a payback . . . but we doubt it! siliconchip.com.au September 2011  25 $500. For an overview, see http://www. bar-fridges-australia.com.au/pdf/reegenmicroplugpresentation1.pdf Voltage optimisers “Voltage Optimiser” devices are another recent development. They have appeared across Australia with marketing targeted at clubs and small businesses wishing to lower their electricity bills. The promoters claim to “reduce electricity cost by up to 20%” by better controlling the voltage. The optimiser is frequently a transformer that reduces the supply voltage to the area or site. It is difficult to see how installing these voltage adjustment devices can save money by themselves. If simply lowering the mains voltage to a device made a major difference to energy consumption you would presumably have larger electricity bills if you lived in an area with higher voltages. In Australia our electricity supplies run at a nominal 230VAC but can be anywhere between 216 and 253VAC. Until 2000 the nominal voltage was 240VAC and there were a number of studies done during the 1990s on what impact a change of voltage would have on typical domestic appliances. In practice it was found that voltage changes have minimal effect, particularly for motor-driven devices. One particular study, that in the 1990s by the University of Ballarat, which included substation monitoring, concluded that voltage variation has minimal effect on energy usage. For further information see http:// itee.uq.edu.au/~aupec/aupec04/papers/PaperID77.pdf It stands to reason: simply lower- ing the voltage to an air conditioning unit does lower its power reading in Watts – therefore you apparently use less power – but to maintain the same temperature, the unit now cycles so that it is on for longer. Total energy consumption and cost will be unchanged. In reality, it would be very difficult for customers to tell if voltage optimisers really are giving a cost saving. In particular, refrigeration or air conditioning unit energy consumption depends heavily on ambient air temperature. There are any number of websites where enthusiastic suppliers show actual energy bills to “prove” their point. But showing energy savings by comparing electricity bills can be simply showing different average air temperatures. For example, a colleague remarked the other day that this past winter (2011) is as cold as he can remember, having used his air conditioner on all but about ten nights. Compare this with the mild winter of 2010, where he recalled using the air conditioner for ONLY about ten nights! To my way of thinking the best way to make a real saving is to adjust the thermostat on the air conditioning to be closer to the ambient temperature and to turn devices off when they are not needed. The only case where these energy devices are cost effective is where motors run at well under their design load for long periods, for example escalators or conveyor belts that are only intermittently loaded. Escalators must be designed to allow for two people on every tread – yet they work day in, day out often with virtually no-one on them. (Modern This intelligent power meter from Jaycar Electronics simply plugs into a normal power point (GPO) and turns it into a real-time power monitoring outlet. You can enter the local price of your electricity and the meter will tell you exactly how much the appliance is costing to run. buildings often have escalators that either stop or slow right down until someone steps on them). Similarly, conveyor belts need to cater for worst-case scenarios but often have significantly less than maximum usage.So be very wary of any company who claims that their device substantially lowers power consumption and costs by modifying the mains voltage. A reduction in power (Watts) will almost certainly be offset by longer running time. Total energy use (kWh) and cost will be unaltered. Lighting? Tiny savings are possible If reaching behind cupboards to turn things on and off isn’t to your liking (or maybe the floor is too far away!) this Ecoswitch allows you to put the on/off switch wherever you find convenient. It’s great for home theatre systems. 26  Silicon Chip The only area where voltage does have a more than minimal effect is lighting, where power consumption and light output are roughly proportional to voltage. The newer fluorescent lights (both compact fluorescent and those with electronic ballasts) draw a constant current and are much less sensitive to voltage than incandescent lamps. But the same saving can be obtained by using lower wattage light bulbs. What’s more, some bargain CFLs siliconchip.com.au can be responsible for a higher power usage than quality, brand-name units (although even this is not always the case). You see a lot of comment in the popular media about turning lights out when not in use but the truth is that lighting represents only a tiny percentage of overall household power consumption. Some other, admittedly marginal savings can be made by reducing the “on” time of sensor lights, particularly outside floodlights which tend to be a bit more power hungry. If whoever/ whatever caused them to trip is still moving around out there, they’ll come back on again! Overall though, you’re not going to save any real money by modifying your lighting usage (with the possible exception of large outside floodlights). Standby power It is estimated that a typical household uses up to 100W in standby power – they’re all the things that are turned on by remote controls, or by pressing “soft start” buttons. 100W continuous adds up to about siliconchip.com.au 875kWh a year and at (say) 25c/kwh, will cost you a couple of hundred dollars or so a year. So can you save this by turning everything off at the power point? Yes you can – but you will often lose a lot of convenience. Anything with a clock may well lose its settings, as may many other devices which rely on standby power to keep their memories active. Some devices, such as Foxtel boxes, can take quite a while to reset themselves. It can be a real pain to have to reset everything each time the power goes back on! But you can – and arguably should – turn off quite a number of devices such as computers and monitors, amplifiers, indeed most home theatre equipment, ceiling fans/lights, and so on. Often it’s very inconvenient to reach a power point to turn devices on and off (another reason most people don’t bother!) but Carbon Reduction Industries have a handy “Ecoswitch” which brings the switch up to where it’s convenient. The socket end can connect to powerboards, etc, if required (www. ecoswitch.com.au). Magic Bullets? Sorry – there are no magic bullets. In the end it is as simple as making certain you understand where your electrical energy is used and that any inefficiencies are removed. The best energy saving device you can try is one of the cheap and cheerful energy meters available from Jaycar, Dick Smith and other stores. They are reasonably accurate and include power factor measurement. Those tried are within 2% of commercial meters. Their main disadvantage is limited resolution in measuring energy consumption (usually kWh, not Wh) over a period and also some can be “fooled” by complex waveforms when measuring low-power switchmode devices. In conclusion, there is only one golden rule in assessing promised energy and cost savings: “Only energy that is being wasted can be saved”. SC * This feature was inspired by, and largely based on, a contribution by John Cameron, with additional material by Leo Simpson and Ross Tester of SILICON CHIP. September 2011  27