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Whether they are used as a supercharger in heat pumps or in the pumping station of a waterwork, pumps are among the largest industrial consumers of electricity. Based on the life cycle of a pump, the energy costs average around 45% of the total costs.
A significant amount of energy can potentially be saved in pump systems, not least because they are generally operational in the partial load range. According to the German Federal Ministry for Economic Affairs and Climate Action, the energy consumption of pump systems can be reduced by 30% through a combination of energy-efficient technologies and process optimization.
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Modern pump systems generally consist of a motor, a motor control, and the actual pump, as well as valves, actuators, and accessories such as sensors, hoses and filters.
Each of these components must be considered when thinking about increasing energy efficiency. When it comes to motors, the efficiency rating according to the IEC 60034-30 standard should be considered (efficiency class/IE = International Efficiency). Efficiency is rated in four classes:
In industrial facilities, different combinations of components are used in pump systems.
The basic approach behind power-on-demand systems is to operate the pump in a way that varies depending on the process and the power that is actually required, rather than using a constant speed. Speed-controlled pumps of this kind only consume energy when the system is actually generating power (power on demand). This means that heat dissipation is reduced significantly and effectively.
A power-on-demand system can be implemented with a conventional asynchronous motor. Depending on the operating cycles and running times, motors in efficiency classes IE2 to IE4 are used. Either a variable speed starter or a variable speed drive can be used for speed control.
The motor control receives data from a pressure sensor about the pressure in the hydraulic system and adjusts the motor speed to the required rated flow accordingly. This system also makes it possibly to supply several parallel processes that have similar requirements for rated flow and pressure. The various actuators can be controlled via directional, proportional or servo valves.
Advantages of power-on-demand systems
Three clean water pumps in a waterworks owned by the Stauden-Wasserversorgung water utility company were powered by conventional electric motors at 55 kilowatts of power each, all activated via motor starters. With this drive technology, the pumps could not operate at their optimum operating point, i.e., in the most energy-efficient manner – the pumps either did not run at all or ran at full power.
Aquatech replaced the conventional electric motors with IE4 motors, which are particularly energy-efficient. In addition, speed-controlled operation was introduced for the motors. The motor starters were thus replaced with PowerXL DG1 variable speed drives from Eaton.
All in all, the combination of IE4 motors with the DG1 drives enabled the Stauden-Wasserversorgung water utility company to cut the energy costs of the pump system by about 15 %.
Reducing the energy consumption of a pump system is the first step towards creating an energy-efficient system. The second step is to pave the way for an energy management system. The key principle here is data acquisition: Only by comprehensively recording and analyzing data relating to energy and machines is it possible to review energy consumption, identify opportunities for optimization and monitor the effects of any measures that are implemented.
An intelligent connection system at device level, such as Eaton’s SmartWire-DT, offers significant advantages here. Such systems mean that components such as switchgear, circuit breakers, pilot devices and actuators can be connected to the controller via a single wire instead of time-consuming point-to-point wiring being required.
Speed-controlled, electro-hydraulic drives are intelligent drive systems that offer an optimal system solution for increasing the energy efficiency of pumps in many applications. They not only help to protect the climate and save energy, but also lower the total cost of ownership (TCO).
Although the investment costs are higher than those of conventional pump systems, these are offset by lower energy costs and shorter payback periods. A further benefit stemming from the fact that they operate based on requirements (power on demand) is that more compact systems can be implemented. In turn, these have lower cooling demands and reduced sound emissions. Speed-controlled pump drives make it possible to achieve significant energy savings with relatively low investment costs – a reduction in energy consumption of up to 70 % has already been achieved in practice.
More detailed information is available in Eaton’s white paper “Planning and operating hydraulic power units to provide greater energy efficiency”, which is available for download on the company’s website.
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