Today’s automation technology makes it possible to operate production plant processes efficiently and to optimize them in response to the available operating conditions. Tailor-made control strategies can reduce the energy requirement in variable speed pump systems and thus save money for the operators. Different applications require different control options. These are mainly pressure, volume flow, filling levels, temperatures and quantities. In this specialization, control systems are being developed to operate such plants with optimum energy efficiency.

Energieflussdiagram eines Pumpenantriebs
Figure 1: Energy flow diagram of a pump drive

Motivation

Pump systems account for a large share of the electrical energy requirement in industrialized countries (up to 20%). In Germany, pumps account for approx. 12% of the total power consumption. Globally speaking, pumps are also among the major consumers. It is estimated that the global energy requirement for the drinking water supply is 7%, up to 90% of which is accounted for by extraction and distribution itself. Even though the oft-cited estimated share of the worldwide electrical energy requirement of 20% due to the operation of pumps seems a bit high, this figure does allow conclusions to be drawn about the enormous installed pump capacity. If the installed power is considered, an enormous leverage effect can be expected to result from improved operation using efficiency-increasing measures such as optimized speed control. Figure 1 shows a corresponding energy flow diagram from electrical energy to hydraulic energy.

The development of control algorithms requires models which can represent the transient and also the stationary behaviour of pumps and pipe systems. Firstly, it is possible to make use of the existing infrastructure at Kesslerplatz for this purpose. In the turbo engine laboratory, there is a centrifugal pump test bench which is very suitable for dynamic tests on the grounds of its relatively long pipe geometry (Figure 2). The acceleration behaviour of fluid columns through centrifugal pumps can also be examined here. Secondly, the Nuremberg Campus of Technology operates a test bench on which advanced models can be verified and control algorithms can be tested (Figure 3).

Pumpenversuchsstand im Turbomaschinenlabor
Figure 2: Pump test bench in the turbo engine laboratory

 

 

Pumpenversuchsstand am NCT
Figure 3: Pump test bench at NCT

 

 

Modelling and control technology

In industrial production, centrifugal pump systems are usually characterized by their H-Q characteristic curves in order to determine the corresponding operating point (OP). However, these same characteristic curves only apply to the stationary case, i.e. the settled resting state of the system. Nevertheless, even when calculating the stationary points in the real pump system, there can be considerable deviations from the characteristic curves supplied by the manufacturer for each pump. Find out more...

Block diagram of a centrifugal pump system

Increasing energy efficiency by means of adaptive operational management

Adaptive pump controls are suitable for cases where several degrees of freedom exist in the operating possibilities. This is primarily the case for pumps arranged in parallel or in series or for filling processes of fluid storage tanks or pressure containers. In turn, combinations of these system topologies have a further degree of freedom for the operation of pumps. Additional degrees of freedom in optimization include time specifications and changing fluid properties. Find out more...

Permitted working range for an autonomous operating point search by a centrifugal pump