ProPurAqva High-efficiency pump for ecological lake water circulation

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2 ProPurAqva High-efficiency pump for ecological lake water circulation To improve the water condition in troubled lake Pien-Saimaa Juha Pyrhönen and Jaakko Larjola Lappeenranta University of Technology (LUT) LUT Energy Electricity Energy Environment

3 KIVISALMI STARTING POINT Strong algae blooming on lake Pien-Saimaa in 2008 fast water-quality-improving actions were desired Decades of experience of Vehkataipale pumping station Low head about 10 cm observed in Vehkataipale A priori knowledge of suitable flow rate of about 10 m 3 /s in Kivisalmi Consultant suggested a high-head commercial pump for Kivisalmi Very low operation efficiency should have resulted Traditional commercial pumps are designed for high heads and use, therefore, a high axial velocity. The losses in very low-head applications are intolerable. In traditional pumps most of power just heats the water! OWN PUMP DESIGN WAS NEEDED!

4 NEW PUMP DESIGN In lake water circulation the total head is very low only a few centimeters. In Kivisalmi the estimated head was 4.1 cm! The head losses are dramatically influenced by the axial velocity in the pump passage (high speed high losses!) High pump impeller diameter and low flow speed are required for high efficiency! Direct drive is another key to high-efficiency The pump blades have to develop a head which is a sum of: - Head required to maintain 10 m 3 /s flow in the canal. - Head losses in the pump entrance and exit A special low-loss pump directly driven by a high-torque permanent magnet synchronous motor was designed

5 In Kivisalmi the head needed is obviously low The pump

6 A low head pump needs: Elliptical input Isolated, low-speed blades fixed to a correctly designed Nacelle Straightening blades removing curl Diffusor High-torque low-speed motor in the nacelle Blade form based on Bernoulli s principles

7 Pump direct drive PMSM PMSM with embedded NdFeB magnets 20 pole pairs 400 V, Hz Rated torque 4560 Nm Rated power 21.5 kw Efficiency 91% Speed 45.1 rpm Nacelle pressurization to guarantee dry operation

8 PUMP DATA Calculated Measured Note Volume flow 10 m 3 /s m 3 /s At a design speed of 45.1 min 1 Pump impeller diameter 3 m Water flow speed at pump element 1.5 m/s Head of the pump element, h m N/A Corresponding theoretical power P = 13.4 kw Pump element efficiency 89 % 88 % Indirect measurement Head of the whole system m m Corresponding useful power P u 4.0 kw 4.1 kw Pump element input shaft power 15.0 kw 15.2 kw Impeller thrust 7124 N Pump input torque 3180 Nm 3220 Nm Input electric power, P i 17.3 kw 17.5 kw At the design speed of 45.1 min 1 Electric drive efficiency (motor, cabling and frequency converter included) Real total efficiency of the system, 23.1 % 23.4 % 86.7% 86.8 % Based on the theoretical pump shaft power and system measured input power LUT Energy Energy Technology Electrical Engineering Environment Technology

9 Elliptical input, nacelle, pump blades and straightening blades seen from the front. Impeller diameter 3 m

10 Side view of the pump

11 Assembly in Kivisalmi Pump on its final place some meters under the water surface

12 LOW ENERGY EXPENSES The pump is designed for water transport with low head. High torque low speed high diameter impeller result in dramatically reduced energy expenses compared to the original suggestion. Special impeller blade design enables to manufacture pumps with 3 m or even with 6 m diameters with reasonable expenses. The Kivisalmi flow will be about 300 million m 3 /year with cost of 50 per million m 3 Annual energy expenses in continuous operation in the Kivisalmi case [ ]

13 Key data: Pump fluid dynamic and electrical design: LUT Energy, Finland Pump manufacturer: WP Waterpumps Oy, Finland Manufacturer of the pump motor: AXCO Motors Oy, Finland Patent applied for the construction Trademark applied for the name ProPurAqva

14 Main applications of the pump Horizontal transfer of clean water to troubled sea or lake areas Vertical transfer of oxygen rich surface water to the low-oxygen deep water areas

15 Possible new projects Kopinsalmi in Lake Saimaa Töölönlahti in Helsinki Vehkataipale in Lake Saimaa (four pump units to replace two old ones, power saving 300 kw)

16 Further technical improvements of the pump? The pump energy demand could be further decreased by making the diffuser longer (if there is enough space). Additional expenses are low, and by this mean the energy demand could be decreased by 15%. Significant decrease in energy demand could be reached by increasing the pump impeller diameter from 3 m to 5 m. This would of course, increase the pump price significantly. With a bigger impeller and with a longer diffusor the pump energy demand could decrease by 60%. This means, that in the Kivisalmi case (10 m 3 /s water transfer) the electricity demand would decrease from 17 kw to 7 kw Optimal design is usually, however, a compromise between pump prize and electricity expenses