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ENERGY SAVING ADVANTAGES OF THE SUPA STELTH PUMP © by Terence R Day THE ISSUES, PROBLEMS AND HIGH COST OF PUMPING AND THEIR SOLUTIONS • • • • •

SOLUTION 1: SLOW RUNNING SOLUTION 2: LARGER DIAMETER PIPES SOLUTION 3: PUMP AND MOTOR MATCHING SOLUTION 4: MATCH THE SYSTEM RESISTANCE SOLUTION 5: NEW SUPA STELTH PUMP WET END

UNIVERSITY TESTS AND VALIDATION NB one or more of the 5 solutions above are able to be applied to any pumping problem.

EFFICIENCY AND ENERGY FACTOR Efficiency is an indirect indicator of dollar cost in pumping. If misunderstood and misapplied pumping can cost more. The term; “high efficiency”, can infer no other considerations are important. Pumping at reduced water speed and efficiency can move the same amount of water for a fraction of the dollar cost! What does “Efficiency” mean? Non- technical people can get confused especially since the introduction of the Government legislated energy star rating for swimming pool and spa pumps in Australia. Decision makers need a basic grasp of the difference between “Efficiency” and “Energy Factor”. Essential information: a pump is never tested alone! What’s tested is a total system that includes the pump, pipes, bends and filter etc. The test rig simulates an in the field “system”, and provides a variable resistance to the flow and collects the performance data. Then applications for the pump can be found. The “Efficiency” on a spec sheet is that of the pump and test rig and never of the pump alone. This is unavoidable as there is no other way to test a pump. Particular pump applications are not emphasized here. It’s about how we can learn from science and some Government authorities, concepts that can be applied in industries that we are interested in. It is erroneous to think that the higher the best efficiency point (BEP) of a pump, that less pumping cost is an automatic corollary. There are other important considerations. The energy usually input is electrical which spins a motor shaft and impeller which accelerates the water. The water then possesses kinetic energy plus static pressure energy which is the total amount of energy in the water (total pressure). This combined pressure energy in the water is then divided by the

2 electrical energy to derive the efficiency %. If 1000 watts of electrical energy goes into the motor and the resultant total energy in the water is 800 water watts; that pump (pump “system”) is 80% efficient. Efficiency therefore means: how efficiently does a pump transform one form of energy into another form? IE “what is the ratio of electrical watts into the pump motor to water watts from the pump” ENERGY FACTOR AND DOLLAR SAVINGS Energy Factor (EF) deals with the dollar cost to pump water. Understanding it reveals how to reduce the dollar cost of getting the same pumping result, IE of accelerating a given volume of water. If electricity cost is constant, the only way to save money is to reduce the quantity of electrical energy going into the pump regardless of pump efficiency or time taken. How do you achieve less electrical watts in?

HOW TO SAVE MONEY: SOLUTION 1: SLOW RUNNING This involves the reduction of costly electrical energy into the pump. Pentair Water rightly claims to be able to reduce the cost of swimming pool filtration by 90%. What would have cost $100 now costs $10. However their Intelliflo does so at less than 10% efficiency! This needs explaining.

Other manufacturers claim 75% reduction in cost of pumping eg Astralpool and Zodiac. The savings are not due to the Intelliflo motor’s “onboard computer” though that may help to regulate the speed for changing conditions. It is due to the lower flow rates requiring longer pumping times whether computer controlled or not. Any pump can achieve similar results and in almost any industry. Governments recognize that the Energy Factor is a more useful concept than the “Efficiency” of the pump for reducing energy use. EG Australia and California with other US states soon following. Here is the California standard for Energy Factor: THIS IS THE METHOD USED FOR MEASURMENT OF POOL PUMP “ENERGY FACTOR” OR PER THE CALIFORNIA ENERGY COMMISSION (CEC) TITLE 20.

3 EF = Flow (gallons per minute) X 60/Power (watts of electrical). This gives the amount of gallons per watt hour. This equals gallons pumped per dollar. In Australia “Energy Factor” is expressed as litres per watt hour. It states how much electrical energy is required to pump a given amount of water by a particular pump. The Australian standard AS5102 imposes the “D” curve. The Standard requires that the pump “Energy Factor” is to be calculated only where its pressure/flow curve intersects the “D” curve while pumping 120 litres/minute.

PRESSURE/FLOW CURVE

Fig 1 The “D” curve from Australian Standard AS5102 with pressure flow curve intersecting it “Litres per watt hour” (i.e. litres pumped per dollar) is assessed for all pool and spa pumps at the D curve intersection while pumping 120 litres/minute. All pumps will use less electricity and the pump that uses the least electricity at 120 litres/minute has the highest Litres per Kw/hr and the most energy stars on the pump label. The buyer can look for a pump that offers the lowest dollar cost to run and the additional choice to run the pump at even lower speed, consuming even less electricity, while still

4 getting the job done albeit by pumping longer. 120 litres/minute is merely the stipulated flow for testing for determining the energy star rating. Conversely, to get the highest possible efficiency a pump must be run at very high speed or RPM to get the highest pressure. THE PRINCIPLES OF SLOW RUNNING Of static and velocity pressure, static pressure is the greatest. When water speed is reduced, the system resistance and therefore the pressure, is also reduced. So the main energy, static pressure, is reduced. Consequentially, so is the efficiency. That’s not a bad thing; it simply is what it is. In another scenario: If a pump has a very high flow rate with accompanying low static pressure, its efficiency is always low. That’s also ok. Highest efficiency is always good but it’s not the whole story. SYSTEM PRESSURE VARIES WITH FLOW SPEED CHANGE The need for pressure reduces if the speed of the flow is reduced. Pipe wall drag on the water and the filter resistance decrease and also water momentum change, due to pipe bends, is reduced. Increasing pipe diameter slows the water. If you cannot enlarge pipes you can slow the pump RPM. If you can do neither you must exactly hit the system “sweet spot” with the pumps BEP (solution 4). If the speed of the flow is halved then the pressure reduces 4 times. But significantly the electrical watts reduce 8 times! It’s the watts consumed over a time that you pay the dollars for. Reducing the water speed by 41.5% reduces the flow by 41.5% but the pressure reduces to half (1.415 squared) and the electrical watts reduce 2.833 times (1.415 X 1.415 X 1.415). So if you reduce the flow speed by 41.5% and the electrical watts input had been 100 watts they then reduce to 35.3 watts. So you pay $35.30 instead of $100.00. The efficiency is reduced but so what? You now don’t need the pressure, meaning you don’t need the high efficiency. You saved money by pumping a little longer! Slowed water reduces pipe wall and other drag sources thus reducing the need for pumping pressure. But can the pumping be performed effectively with reduced flow when the “system” of pipes and filter has not changed? Yes, because the resistance has reduced! Driving a car slower also saves a much higher percentage of fuel money than the percentage of speed reduction. For the highest possible “litres per watt hour” i.e. pump for the least money, you can run at reduced flow rate i.e. reduced pump RPM but for longer; or implement solution 2 below. SOLUTION 2: LARGER DIAMETER PIPES Pipe diameters can be more important than pump speed. A high efficiency pump at very high speed is able to deliver reduced dollar cost if the pipes are large diameter because 1; this reduces water speed

5 and therefore the wall drag inside the pipes and 2; enlarged pipes also increase the ratio of cross sectional area of the flow to pipe wall area. I.e. there is more water volume to pipe wall area so less drag. If pipes are bigger, pump RPM does not necessarily need to be reduced; either way, slow the flow. If simply enlarging all new pipe diameters universally was mandated it would save billions of dollars in electricity costs worldwide if implemented globally. And that is without even improving pumps and pump motors. Now to be clear. Some pumps and some motors must run at high speed for hard filtering jobs or to pump to high elevations requiring high pressure which results in a high efficiency. But when only a single speed motor is available or through ignorance, getting the job done faster than is necessary generates unnecessary pressure and so the consequential high efficiency is viewed as a virtue of the pump. It is but it’s a costly virtue. Older systems often have small diameter pipes but in any system, small diameter pipes or not, there is always something that can be done to improve the pump or system to get some energy savings. One of the problems is that due to past lack of concern with environmental and energy issues the cheap single speed induction motors were the only option. Their speed, or RPM, is set by the electricity generating stations supply frequency (hertz). It did not matter much when electricity was cheap. Now there are many endeavors worldwide to build more energy efficient motors. SOLUTION 3: PUMP AND MOTOR MATCHING Most companies choose motors “off the shelf” to drive their pumps. This has also contributed to the inefficiencies of pumping systems worldwide. The reason is that the “wet end” of a pump and an electric motor both exhibit a best efficiency point (BEP). This BEP is at the highest point on a chart curve derived from the pump or motor testing. The BEP of the motor and of the pump usually do not coincide. If a wet end of a pump is at its best efficiency of 70% at 1800 RPM and a certain pressure/ flow but its motor is at its best efficiency of 70% at 3200 RPM, then the two together running at 2,500 RPM may have an efficiency of only 35% because their BEP’s do not coincide when viewed on a chart. SOLUTION 4: MATCH THE SYSTEM RESISTANCE However, if the pump wet end and motor have been well matched and delivering 70% BEP, but the system resistance(sweet spot) is well below or well above the pressure that the whole pump gets its best efficiency point( BEP) at, then that pump and system may still get only 35% efficiency even though it is capable of 70% efficiency. A pump/motor combination is purchased by a naïve purchasing officer because its spec sheet boasts 80% efficiency while the other pumps Googled were not claimed to be above 72% efficiency. The pump is driven by a fixed speed induction motor. One of the factory’s systems of pipes is only 10metres long with 2 bends but another system of pipes is 30metres long with 7 bends.

6 So one pipe system is 3 times longer than the other. Its resistance and pressure are 9 times that of the 10 metre pipe (3X3=9). The 7 bends as opposed to 2 bends massively increase the system resistance. But the sweet spot which the BEP lies squarely over is generated by a pipe system of 15 metres long with 3 bends. If you found a system flowrate target with a resistance exactly matching the pump BEP then you would get the published pump efficiency of 80%; the reason it was chosen by the purchasing officer. But that pump with a potential of 80% efficiency may be operating at only 20% to 40% efficiency if not matched to the target! Thus 3 things need matching; the wet end to the motor and that to the system. ONE PUMP DOES NOT FIT ALL Below is an actual pool pump pressure/flow curve. The BEP is about 44%, typical of pool pumps as seen on right of chart. The 3 circles show 3 different flow rates depending on the resistance found in each of the 3 systems it might be plugged into. A very restrictive system might cause the pump flowrate to drop to 100 litres/min at 185 kpa of pressure (left circle). It would then have an efficiency of only 28%! The right circle outlines where the pump might run in a high flow, low pressure application. At 330 litres/min and 90 kpa it is only 35% efficient. But the pump has a BEP of 44%! Our purchasing officer purchased the pump with the simplistic notion that the pump would always be running at 44% efficiency!

BEP

Fig 3 Efficiency curve laid over a pressure flow curve

7 A BEP is only ever found at one narrow band of pump performance. Not matching that narrow band to the corresponding point of resistance of the system is one of the most money wasting decisions that can be made. That is because it is easy to know how to calculate it. WHEN THE SYSTEM RESISTANCE CHANGES The system resistance increases slowly while the flow reduces slowly in the case of a slowly clogging filter; or it changes quickly up or down as in the case of one or otherwise many taps being turned on or with a car engine cooling pump having changing cooling needs as the engine changes revs. In Fig 3 a filter may theoretically begin to collect debris at about 400 litres/min and 50 kpa of pressure and may be totally clogged when the flow has reduced to 100 litres per min at 185 kpa or otherwise at 200 litres per minute at 155 kpa depending on whether backwashing the filter has been remembered. So as with changing flows (flows by pressures, example, a pool pump) there is also a changing efficiency over time seen from the efficiency curve above the pressure/flow curve in the chart of Fig 3. A pump with a broader efficiency curve gives a higher average efficiency than another pump with a higher BEP but a narrow efficiency curve! With these changing systems there is merely an average efficiency but it is more important than a BEP! Between 400 litres/ minute reducing to 100 litres/ minute in Fig 3 the average efficiency is about 30%. Full attention to the above principles, applied nationally and globally would help all of us to have less reason for complaining about damage to the environment and our wallets. SOLUTION 5: NEW SUPA STELTH PUMP WET END SOLUTION

Fig 4 The Supa Stelth and the “leading brand 1” using the same single speed motor. Tested 07/11/2011

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Fig 5 The Supa Stelth and “leading brand 2” using single speed induction motors with the “leading brand 2” motor drawing 17% more amps than the Stelth. Tested 28/11/2011

24.7 LITRES PER WATT/HOUR

37 LITRES PER WATT/HOUR

Fig 6 Competitor pump and Supa Stelth both reduced to 1900 RPM. The Supa Stelth has far less reduced efficiency than competitor which is typical of conventional centrifugal pool pumps. Both pumps are powered by Brushless DC motors. Tested 29/11/2011 Notice the “litres per Watt/hour for each at 30 kpa. That gap gets even larger with increasing pressure in the chart of Fig 6. One reason the Supa Stelth has higher efficiency and higher litres per watt/hour over all centrifugal water pumps is that it has no diffusers or volute. Conventional centrifugal pumps must fling high kinetic energy water into the diffusers to get their pressure. At low speed, with resultant low kinetic energy water from the impeller, conventional pump diffusers do not work properly but instead get in the way.

9 The Supa Stelth pump has no diffusers but gets its pressure by its “solid body vortex” of water which is simultaneously a centrifuge and the fact that the water vortex has a higher speed at its periphery than at its impeller blade tips; the water molecules line up like spokes (no molecular shear). This is totally unique to the Supa Stelth pump and a world first. PRESENT MONEY SAVING MOTOR SOLUTIONS For a few years there have been brushless DC motors (BLDC) which run at varying RPM driving pumps. That means some pumps now give higher “Litres per watt/hr”; they save dollars when run slowly. They then run at a higher speed only necessary if the conditions change and when they need to get the highest efficiency (highest pressure)for a relatively short time. • • • • •

A pool pump can run slow for dollar savings and then run fast for priming, running water features and vacuuming etc. An engine cooling pump can run slowly for low car engine revs saving fuel and then faster for high engine revs. A bilge pump can run slowly while only a small amount of water needs pumping (and save lives if there are battery or generator problems) but then very fast for a major leak. A rural pump can run slow for big dollar savings but then run fast in an emergency or extra taps are turned on in the house. Industry, aeronautical, aerospace, marine and transport can also benefit from the use of variable speed motors which also have average higher efficiency than induction motors.

The reasons are twofold 1: the brushless variable speed motors are more efficient anyway and 2: they can be better matched for speed and torque to the wet end of the pump so that the two achieve their best efficiency together. NEW MOTOR SOLUTIONS: A NEW GENERATION OF MONEY SAVING MOTORS New motors are being developed right now that will give even higher money savings than the existing variable speed motors. The savings will be from increased efficiency at all speeds or from lower manufacturing cost or both. HIGH SPEED MOTORS Some of the new motors must run at high speed to achieve their highest efficiency. That is not an impediment to low cost pumping or to any application. All centrifugal water pumps have an optimum RPM where they perform best. At other speeds most perform poorly. High speed motors therefore should be matched to pumps that can deliver high efficiency over a broad RPM range including at high RPM’s. Only the Supa Stelth pump possesses these features. It is not the motor or pump speed per se that is the issue if adequate sized pipes are used. Slow the water speed with large diameter pipes and not the motor or pump speed necessarily.

10 MOTOR MATCHING WITH THE SUPA STELTH PUMP When existing or the new motors are matched with the Supa Stelth pump, the highest possible efficiencies and litres per watt/hour are delivered for the greatest possible money savings. The Supa Stelth pump has the broadest efficiency curve. It always delivers a higher efficiency over a broader flow regime and over an extremely wide RPM range. NEW SUPA STELTH PUMP WET END SOLUTIONS The SUPA STELTH PUMP can now be related to the subjects discussed. It enhances the 4 solutions described but also delivers large energy saving benefits even if one or more of those solutions cannot be implemented. The SUPA STELTH is described in relation to: • • • •

SOLUTION 1: SLOW RUNNING SOLUTION 2: LARGER DIAMETER PIPES SOLUTION 3: PUMP AND MOTOR MATCHING SOLUTION 4: MATCH THE SYSTEM RESISTANCE

SOLUTION 1: SLOW RUNNING When the SUPA STELTH pump runs at reduced speed its efficiency also reduces but not as far as that of conventional pumps (see Fig 6). This is because it has no diffusers that in conventional pumps convert the kinetic energy in the water to static pressure energy. Diffusers do not work at low pump speed. The Supa Stelth generates its static pressure energy by an entirely different means; it is a centrifuge. That means its efficiency is always higher than conventional pumps at all speeds from very slow to very fast. SOLUTION 2: LARGER DIAMETER PIPES Slower water through larger pipes is complimented by the larger flowrate of the SUPA STELTH. Conventional pump diffusers, designed to increase pressure, simultaneously work as rate limiting valves partially negating the large pipe advantage enabling higher flowrates . Conventional pumps cannot produce the large flows in any case that the larger pipes could accommodate but the SUPA STELTH can. SOLUTION 3: PUMP AND MOTOR MATCHING It is much easier to match any motor to a SUPA STELTH “wet end” because of its broader efficiency curve. As described above; ideally the BEP of both motor and wet end should coincide. If that’s difficult, the broadest efficiency curve is the widest, easiest to hit target for the motor’s BEP. The two will always be of higher efficiency and especially so with changing system resistance.

11 The SUPA STELTH also performs better than any other pumps over a broad RPM range with higher efficiency than can be achieved by conventional pumps. The charts of Fig 7 are produced by an Australian University on a SUPA STELTH pump of only 130 millimeters diameter by 40 millimeters outside dimensions. The test rig employs a torque transducer so that the shaft power and not electric motor power is measured. Efficiency for its size is unprecedented and also for over such a wide RPM range. Other small pumps are always low efficiency. Since these charts the efficiency has not reduced even at 5,000 RPM. Higher RPM’s are planned (after increasing test rig pipe diameter!)

Fig 7 University produced chart. SUPA STELTH has a far greater RPM range maintaining efficiency than conventional pumps; suits low speed, variable speed and high speed motors

12 SOLUTION 4: MATCH THE SYSTEM RESISTANCE Accomplished best by the SUPA STELTH for two reasons 1; the broad efficiency curve enables a higher efficiency where the resistance of the “system” is hard to calculate or unknown until the pump is connected and pumping and 2; the SUPA STELTH is able to be quickly adapted to any system by the extremely quick changeover of the impeller and or the internal inserts (3 minutes). No other pump can do this because if their impeller diameter is changed they must also change their diffuser dimensions or they lose efficiency.

Fig 8 Snap in inserts reduce pump internal diameter

Fig 9 Quick change impeller enables fast adaptation to any system

13 UNIVERSITY TEST RESULTS Test results are available from the testing by two different Universities, one for the very small SUPA STELTH pumps suitable for bilge, engine cooling, domestic appliances up to rural and pool pump capacity and from the second University; test results for larger size Supa Stelth pumps. Tests results including “back to back” are available to interested parties by arrangement.

SUMMARY It may be now possible to save 50% of the 30% of the world’s electricity that powers pumps and fans worldwide. High Efficiency (EFF) should mean a pump costs less to run but paradoxically it can cost more if efficiency is not understood and applied correctly. A pump should never be purchased based solely on its quoted best efficiency point (BEP). It should match the system or it could run at half the quoted efficiency and so cost more to run. Energy Factor (EF) indicates the dollar cost and the understanding to be able to reduce cost. The Supa Stelth pump is lower cost to manufacture and runs several times quieter than other pumps because the main source of noise in centrifugal pumps has been removed being the diffusers or otherwise the cutwaters of centrifugal volute pumps.