Fig 2 - uploaded by Tero Ahonen
Content may be subject to copyright.
Parallel operation of pumps 1 and 2 (points A and B) and thee resulting operating point location C with the total flow rate Q1+Q2. (Bortoni et al. 2008)
Source publication
The article aims to find a solution for the energy efficiency improvements in variable speed-controlled parallel pumping systems with lesser initial data and without additional flow metering and start-up measurements. This paper introduces a new control strategy for variable speed-controlled parallel pumps based on flow rate estimation and pump ope...
Context in source publication
Context 1
... rotational speed to be lower than the nominal rotational speed, thus gaining more energy efficient operation.The basic version of the rotational speed control for parallel-connected pumps, the traditional rotational speed control strategy, is based on the adjustment of the rotational speed of only a single pump at a time. This is illustrated in Fig. 2 in the case of two parallel pumps. Before the additional pump is started, the rotational speed n of the primary pump is increased to the nominal rotational speed nnom. ( Karassik et al., 2001;Volk, 2005;Jones, 2006) A higher energy efficiency compared with the traditional rotational speed control can be achieved if both parallel pumps ...
Citations
... Conventional methods cannot directly determine the maximum number of pumps that can be paralleled; as the number of parallel units increases, the drawing proportion needs to be reduced, resulting in reading error [29] . According to the characteristic model of the parallel variable-speed pump, B. Barán [30] used an analysis method to optimize and determine the number of parallel pumps. ...
Central heating system faults affect building energy consumption and indoor thermal comfort significantly. To aim at the balance between thermal comfortable and energy-saving of the heating system for high-rise residential buildings, this paper proposes a method for the central heating system of high-rise residential buildings based on distributed model predictive control. The method analyzes the coupling factors between adjacent rooms’ temperature. Based on the state space method, a multivariable indoor temperature model is established and verified. The distributed model predictive control method is used to control and optimize the indoor temperature, and the load distribution of the circulating water pump in the heat exchange station is optimized according to the predicted heat demand. The results demonstrate that the indoor temperature after distributed model predictive control can stable near the set value. Compared with the centralized control methods, the proposed methodology can reduce energy consumption by 14.28%. Meanwhile, the efficiency of water pumps is increased by 16.74% after using the distributed control strategy.
... In [16], a control strategy is proposed for a variable speed multi-pump system to reduce energy consumption. It was shown that the system of parallel pumps has the highest efficiency when the pumps operate at the same speed and flow rate than when one of the pumps operates at the rated speed and the speed of the other one is adjusted to obtain the required flow rate. ...
Reliability, along with energy efficiency, is an important characteristic of pump units in various applications. In practical pump applications, it is important to strike a balance between reliability and energy efficiency. These indicators strongly depend on the applied control method of the pump unit. This study analyzes a trade-off method for regulating a system with three parallel pumps equipped with only one frequency converter (multi-pump single-drive system). A typical operating cycle of a pumping system with variable flow rate requirements is considered. The proposed trade-off method is compared with the traditional regulation, when a change in the operating point of the pump is achieved only by changing the rotation speed, and with the method for maximum reliability. It is shown that the proposed trade-off method makes it possible to ensure sufficient reliability of the multi-pump system operation without a significant increase in energy consumption.
... To avoid inefficient part load phases dual-pump configurations are investigated that replace a single main pump by two smaller variable displacement pumps [15] or by a smaller primary pump and a VSFD EMP (operated in open loop) [16]. Last, energy efficient control strategies of parallel speed variable pump systems parallel centrifugal pumping systems were investigated in [17]. ...
Hydraulic power packages (HPP) integrate electric motor-driven pumps (EMP) and
hydraulic equipment to supply (on demand) hydraulic power to specific functions. To
achieve a high operational availability two redundant EMPs are installed per HPP. To
produce maximum output power, the EMPs need to operate in parallel. In the first
part of this paper a baseline pressure control strategy is developed that enables the
parallel operating mode. It has to cover the performance requirements and it is crucial
to avoid stability issues of today’s aircraft multi-pump hydraulic systems, induced by
slightly differing pump characteristics. A central pressure controller, which calculates
the total (cumulated) control effort and allocates it evenly to both EMPs, is selected
as the basic controller structure. A loopshaping approach, where the requirements
are mapped on target loop shapes, is applied. The control design is verified by nonlinear
simulation and by experiments using representative aircraft prototype EMPs.
Their slightly differing characteristics are utilized for an implicit proof of robustness.
The second part of this paper makes use of the low utilization of the EMPs during
most parts of the flight to achieve secondary objectives (efficiency, dynamic performance)
and to improve the handling of operational constraints (e.g. electric input power
limit). A model predictive control allocation (MPCA) algorithm flexibly allocates the
total control effort to the EMP units. The allocation is derived from the solution of
an optimization problem with the operational limits as constraints. Non-linear simulations
of two exemplary scenarios show that the MPCA algorithm minimizes power
losses by increasing the utilization of the more efficient unit. In addition, the MPCA
algorithm improves the dynamic performance in case of an assymetric performance
degradation by prioritizing the unit with better performance capability. The potential
for improvement increases with the difference between the units and therefore offers
advantages in dynamic allocation in particular for fault-tolerant operation.
... Variable-frequency drives can provide better energy use efficiency in pumping systems, as the operation point of the motor-pump set is adjusted to the design point of each subunit by varying the motor supply frequency, acting on the control of its rotation (Araújo et al., 2006;Viholainen et al., 2013;Sungur et al., 2016;Valer et al., 2016). Thus, its use can provide an improvement in the pressure and flow control of irrigation systems, besides saving energy by avoiding the dissipation of hydraulic energy in pressure regulator devices (Burt et al., 2008). ...
Irrigation is essential for the development of crops in regions with scarcity or irregular rainfall distribution, enabling high productivity. However, the use of water resources and electrical energy leads to a concern with irrigation efficiency. Pressure demand varies during the operations of irrigation systems and the appropriate pressure can be regulated by variable-frequency drives for the power supply of the motor-pump set. This study aimed to analyze the technical and economic feasibility of using a variable-frequency drive to adjust the pressure in subunits of micro-irrigation systems. Laboratory tests were carried out to determine the electrical power consumed in each irrigated subunit for different slopes and the application or not of the variable-frequency drive. Thus, an economic analysis was carried out considering the electricity tariff for group B and rural consumer class, as well as different annual irrigation times. The results showed the potential for energy saving with the use of the variable-frequency drive. Thus, the economic analysis showed that the variable-frequency drive was a better alternative than the dissipative method.
... In [9], the solution for energy efficiency boosting in a multi-pump system with variable speed drives is proposed. The concept does not include any additional flow meters or measuring instruments for flow-head characteristics. ...
... The performance curve of the first pump (VSD) should cross point 1 with coordinates (Q req /2; H req ). The rotational speed of the first pump is determined by equation (9). The regulation throttle of the second pump (non-adjustable) is controlled to maintain ...
... The performance curve of the first pump (VSD) should cross point 1 with coordinates (Qreq/2; Hreq). The rotational speed of the first pump is determined by equation (9). The regulation throttle of the second pump (non-adjustable) is controlled to maintain Q2 = Qreq/2. ...
The energy efficiency of a multi-pump system consisting of two low-power (0.75 kW) pumps operating in parallel mode and a single-pump mechanism (1.5 kW) is compared in this study. For this purpose, mathematical models, experimental data, and data retrieved from the manuals provided by the pump manufacturers are used. The single-pump system is fed by a single variable speed drive. A multi-pump system running in parallel mode consists of two pumps. One of them is driven by an induction motor connected directly to the electrical grid and equipped with a throttle. Another pump is actuated by an induction motor fed by a variable speed drive. The flowrate of the liquid in the multi-pump is controlled with the help of speed variation and throttling. In the case of the single-pump system the conventional speed control method is applied during the analysis. For both pump system topologies, the daily and annual energy consumption is obtained. As a result of conducted calculations, it was shown that the multi-pump provides 29.8% savings in comparison to the single-pump system in the case of a typical flowrate profile.
... With a conventional FS-PSHP, the real power of the pump is nearly constant at its rated value, and the discharge varies with the head value in the pumping cycle. On the other hand, the affinity law, i.e., P new ¼P old (N new /N old ) 3 , in pumping mode shows the input real power is proportional to the cube of the pump speed [38,39]. For this study, if the motor operates in the speed variation range 14%, i.e., ±7%, the real power can regulate within the range of 64%, i.e., 0.86 3 , to 100% of rated power, which is limited by risk of cavitation in the pump runner and minimum head as shown in Fig. 4. Therefore, the VS-PSHP can regulate the frequency of the grid even in the integration of renewable energies such as wind and solar plants whose production is unpredictable. ...
... Each VFD is also capable of driving more than one motor [34]. Therefore, their implementation in Central Plant, where multiple motors and pumps are installed close to each other, will lead to some cost consolidation [35]. Reducing the fan speed with VFDs results in a reduction of the airflow and significant energy consumption [36]. ...
... While this study does not include the airflow measurements, it confirms that the implementation of VFDs will lead to better energy efficiency. Also, the implementation of VFDs can reduce the risk of mechanical failure [35]. ...
At Texas State University (TSU) in the United States, “sustainability” is pursued within the context of (1) a non-binding declaration in the University’s plan, and (2) a State legislative directive to reduce energy consumption. Grounded in these direct links between sustainability and energy use, this paper evaluates energy efficiency at TSU. The aim of the applied case study is to inventory current (business as usual) energy consumption levels at TSU, and to understand how those levels might change under a regime of more sustainable energy technology. The paper performs financial analysis to show that selected sustainable energy projects can not only reduce energy use at TSU, and thereby strengthen the University’s commitment to sustainability. Sustainable energy projects will also save the University money in the long run. The case study draws on a sample of the 13 on-campus buildings with the highest current levels of energy consumption. The approach of the paper is to determine the level of attractiveness of investing in new technology by calculating the Net Present Value (NPV) in terms of financial savings every year (simple payback) or a more extended period (cash flow model). The environmental impact is calculated in terms of CO2 emission based on Scope 2 methodology. We find that TSU could achieve annual electricity savings of 15,391,436 kWh (17% of its annual energy costs) from implementing selected projects and save more than $1,000,000 in annual costs. Overall, TSU could reduce CO2 emissions by 12,561.81 metric tons. The shortest payback period belongs to the pump replacement, and the most significant annual kWh saving is represented by the replacement of the lighting system. Solar panel installation has the highest upfront investment reaching more than $7 million, while its implementation will bring the highest environmental impact by avoiding 2926.81 metric tonnes of CO2 every year. However, the recommended minimum cost of energy at 14–16 (¢/kWh) for solar panel implementation cannot compete with the 8 cents per kWh paid for the electricity at San Marcos. The findings have immediate practical relevance for campus planning at TSU, and the methods are replicable and extendable for use by practitioners and researchers at other Universities or large institutions.
... In the past, many investigations have been performed for improving efficiency in multi-channel confluent water supply systems. The authors in [1], for example, describe a new control strategy for variable-speed controlled parallel pumps ("pump-controlled" systems), which significantly improves energy efficiency compared with traditional control. In [2], a new kind of "pump-valve-controlled" strategy for a parallel-pumps water supply system was developed, and the model was optimized using a genetic algorithm. ...
Transportation efficiency is a problem of particular interest in multi-channel confluent water supply engineering. Transportation efficiency depends not only on the system control strategy but also on the pressure loss (pressure difference between the inlet and outlet) and pressure drop (amplitude of outlet pressure fluctuations) of its structure. In this article, sensitivity analyses of the pressure loss and pressure drop to changes in multi-channel confluent water supply geometry are presented. An experimental set-up was established to validate computational fluid dynamic (CFD) predictions and obtain the boundary conditions for two-channel synchronous switching. The influences of the geometric structure varies by the clustered pipe diameter (40 mm < Dc < 80 mm), main pipe diameter (30 mm < Do < 80 mm), channel pitch (60 mm < L < 400 mm) and number of channels (2 ≤ n ≤ 4); those variables were investigated with the help of CFD simulations. The results showed that configuration “C” can be considered a costless method of decreasing pressure loss (βC(2.05) < βA(2.42) < βB(2.64)) and that the different configurations are insensitive to pressure drop. The variations of the influence of channel pitch and clustered pipe diameter on pressure loss have extremes at L/d = 5 and Dc/d = 2.5, respectively, but the effect on pressure drop is not obvious. The main pipe diameter and the inlet velocity have more significant influences on efficiency. The results can be used to choose the proper geometry of multi-channel confluent water supply to enable energy savings.
... Here, the turn on and of points of three pumps (switch points) and speeds are calculated and savings up to 15 % are reached. Another model-based strategy is presented in [5]. This investigation uses a soft-sensing method for flow rate estimation to lower the power demand, which led to 20-25 % energy savings. ...
... In open-loop pumping systems, the dynamic head is a function of the flow rate, and the static head remains unchanged (as in Equation (3)). The static head is zero for a closed loop pumping system [24] (as in Equation (4)). ...
Among the total energy consumption by utilities, pumping systems contribute 30%. It is
evident that a tremendous energy saving potential is achievable by improving the energy efficiency
and reducing faults in the pumping system. Thus, optimal operation of centrifugal pumps throughout
the operating region is desired for improved energy efficiency and extended lifetime of the pumping
system. The major harmful operations in centrifugal pumps include cavitation and water hammering.
The pump faults are simulated in a real-time experimental setup and the operating point of the
pump is estimated correspondingly. In this article, the experimental power quality and vibration
measurements of cascade pumps during cavitation and water hammering is recorded for different
operating conditions. The results are compared with the normal operating conditions of the pumping
system for fault prediction and parameter estimation in a cascade water pumping system. Moreover,
the Fast Fourier Transform (FFT) analysis comparison of normal and water hammering (faulty
condition) highlights the frequency response of the pumping system. Also, the various power quality
issues, i.e., voltage, current, total harmonic distortion, power factor, and active, reactive, and apparent
power for a cascade multipump control is discussed in this article. The vibration, FFT, and various
power quality measurements serve as input data for the classification of faulty pump operating
condition in contrast with the normal operation of pumping system.
