Addition of VFD for Water Pump Systems with Constant Speed up to 75 kW
Pumps
Measure Goal
The goal is to estimate the electricity savings triggered by adding a frequency converter (VFD) for water pump systems with constant speed up to 75 kW with demand analysis. This measure is relevant when analyses have confirmed that the required flow rate is constant, but the current value is too high. The desired flow rate is achieved with reduced pressure. The savings are related to the reduction in flow rate and pressure.
Symbols, Terms and Units
| Symbol | Description | Unit |
|---|---|---|
E | annual electricity consumption | kWh/a |
ΔEeco | cumulative electricity savings | kWh |
f | Factor | — |
Ns | Standard effective duration | a |
Δp | Differential pressure at pump connections | kPa |
Q | Flow rate | m³/h |
t | annual operating hours | h/a |
η_CF | Efficiency of frequency converter | — |
η_P | Pump efficiency | — |
η_M | Motor efficiency | — |
Calculation Formulas
Stromverbrauch der aktuellen Pumpe
The electricity consumption of the current pump is calculated based on the measurement of the electrical power consumption by the system.
Stromverbrauch nach der Sanierung
The electricity consumption after renovation is calculated based on the actually required flow rate and the additional losses due to the frequency converter.
Wirkungsgrad des Frequenzumrichters
The additional losses caused by a frequency converter can be expressed depending on the rated power of the motor.
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