The initial situation

The Waterworks of the City of Brno (Brnenske vodovody a kanalizace a.s.) asked the company PUMPA a.s., a customer of Franklin Electric, to evaluate the existing pumping stations in the cities of Březové and Svitavou. The aim was to upgrade the existing system to the latest technical standard and to find possible energy saving potentials. When the team from PUMPA a.s. arrived on site, the first step was to select a well for the project, where the energy audit would be carried out and which would be representative of the cities Březové and Svitavou.

The selected well was equipped with a pump with a 45 kW asynchronous electric motor. The pump worked at an operating point of Q=54 l/s and H=34 m. The adjustments to the required parameters (Q&H) were carried out mechanically (throttled) at that time. The annual power consumption at this well was 320.244 kWh. This corresponds to 0.2459 kWh/m³ per unit of water pumped.

 

The solution

In cooperation with the experts from Franklin Electric, the situation was analysed and the innovative High Efficiency System was chosen, which enables energy savings of up to 20 %.

The system consists of a 304SS NEMA synchronous motor, a frequency converter (VFD) and a suitable output filter. The system is supplemented by a suitable submersible pump.

High Efficiency System for the well:

• Rewindable permanent magnet submersible motor 22 - 30 kW
• Stainless steel submersible pump
• Variable Frequency Drive IP66 (VFD)
• Sinusoidal filter IP54
• flow meter

After evaluating all the advantages that the High Efficiency System would bring, the Waterworks decided to invest in the modernisation of the well. The equipment was installed by Franklin Electric.

The result exceeded expectations

It did not take long for the results of the newly installed system to become apparent, as energy costs fell continuously. The total annual consumption of electrical energy at the well decreased to 176.466 kWh and the energy consumption per unit of water pumped was 0.1355 kWh/m³.

The new system has therefore exceeded expectations, achieving a 45 % saving in total electrical energy consumption per m³ of water pumped compared to the previous equipment.

The reason for this enormous energy saving is partly due to the fact that the originally installed system had to be modernized, and also the set-up had to be optimized. The second reason is the outstanding efficiency of the Franklin Electric High Efficiency System. It is the combination of perfectly matched components and their control: motor, pump, frequency drive and output filter. Most importantly, it is the submersible motor’s permanent magnet equipped rotor that eliminates rotor losses thus significantly reducing motor current and heat rise. In many cases, reduced motor current equals less drop cable cross sectional area further reducing overall installation cost.

The return on investment for this project had been calculated for 2 years. However, due to the high energy savings, the entire investment for the well system was amortized after only 1.5 years.