Maximizing solar water pump efficiency: Exploring MPPT strategies for optimization

The global agricultural sector is of utmost importance and is heavily dependent on water supplies to survive. The effective use of water in agriculture is essential, and water pump systems are essential to this process. These pumps have historically been run by diesel or traditional electrical sources. However, there are obstacles that make them less practical for general use, such as the increasing cost of diesel and the sporadic nature of traditional power supply.

The solar water pump system has come to light as a potential solution to these problems. By using solar energy, the device provides an affordable and environmentally friendly way to operate agricultural water pumps. The system, which consists of a motor, power electronic converter, and solar PV array, captures solar energy and transforms it into electrical power. Although producing electricity is a very simple process, using photovoltaic power presents a considerable problem because of the non-linear nature of the PV array.

In order to maximize the efficiency of solar-powered water pumps, a study explored a variety of MPPT management algorithms, offering insightful information about how well these pumps function under varied solar conditions.¹ The results emphasize how important efficient MPPT techniques are to improving the general effectiveness of renewable energy applications. Reference 2 provided an analysis of the evolution of solar water pumping systems and sheds light on the issues and developments in this field. Key elements are covered in detail, offering a complete analysis of the cutting-edge techniques and technology used in solar water pumping. The study advances knowledge in the area by highlighting the importance of continuous advancements in photovoltaic technology-powered sustainable and effective water pumping systems. Reference 3 thoroughly reviewed solar photovoltaic water pumping system technology, emphasizing its use in community drinking water and irrigation. The review covers important facets of the technology and offers a thorough examination of both its present state and future directions. The efficacy and applicability of solar photovoltaic water pumping systems for community water supply and agricultural irrigation are better understood, thanks to this research. Researchers and practitioners working in the fields of water resource management and renewable energy found this paper to be a useful resource and provided a thorough analysis in Ref. 4, illuminating a number of the technology’s facets. Modeling, design process, and size optimization were covered in detail in Ref. 5, which also offered insights into grid-connected and independent setups. In the meantime, Ref. 6 concentrated on real-world implementation by evaluating the effectiveness of solar agricultural water pumping devices. Collectively, these articles enhance the body of literature by addressing many aspects of solar-powered water pumping, ranging from an introduction of technology to design optimization and assessment of the actual performance.

A thorough analysis was conducted in Ref. 7, with an emphasis on the field performance, control tactics, and designing techniques of these systems. An incisive assessment of the state of research and actual conditions of solar photovoltaic water pumping systems was given in Ref. 8, addressing a wide variety of topics. Furthermore, Ref. 9 made a contribution by providing a case study analysis and evaluating the performance studies of directly connected solar water pumping systems. Collectively, these publications address design issues, control tactics, system status, and performance assessments, all of which are important to the growing understanding and development of solar-based water pumping technology. Reference 10 shed light on systems that use induction motor drives and offered insights into the use of solar photovoltaics for water pumping, with a focus on motor drive technology in particular. A thorough analysis of the layout and functionality of solar-powered water pumping systems was carried out in Ref. 11, outlining a renewable energy plan that is especially suited for Mozambique. Reference 12 added more to the body of knowledge in this area by offering a thorough analysis of a range of solar-powered water pumping system characteristics. Collectively, these publications address a wide range of topics, including system design and performance, motor drive technology, and the wider use of solar-powered water pumping in various geographical situations. The creation of a maximum power point tracking (MPPT) control technique for an induction motor drive with solar power and direct torque control, combining a reliable speed and parameter adaptation scheme designed for water pumping applications, was the main topic of Ref. 13. Offering insights into maximizing the use of renewable energy sources, Ref. 14 presented a thorough analysis of control and energy management techniques applied to solar photovoltaic and wind energy-fed water pumping systems. In a more recent work, Ref. 15 provided an optimization strategy employing genetic algorithm-based MPPT for increased efficiency while examining the financial and environmental advantages of switching to solar water pump systems. Together, these articles expand our knowledge and progress on solar-powered water pumping systems by tackling topics including optimization strategies, energy management tactics, and control strategies.

The control algorithms used in solar-powered water pumping systems were reviewed in detail in Ref. 16, which also offered a detailed analysis of different approaches. Reference 17 provided a comprehensive overview of the literature on solar-powered water pumping systems, encompassing a broad range of subjects in the field. With a particular emphasis on PV-fed water pumping systems that use brushless DC (BLDC) motors, Ref. 18 reviewed these systems and added more to our knowledge of motor technologies in these kinds of applications. Altogether, these works contribute to the field by discussing motor technology, general system research, and control methodologies in the context of solar-powered water-pumping systems through extensive analysis, concentrating on several solar water-pumping system components, including their configurations, traits, and functionality.¹⁹ By providing a thorough analysis of solar, wind, and hybrid wind-PV water pumping systems from an electrical engineering perspective, Ref. 20 offered a broad perspective by covering numerous facets of these renewable energy-driven systems. To improve the efficiency of solar water pumping systems, Ref. 21 provided a novel fractional-order fuzzy-MPPT approach. By covering parts, system viewpoints, and sophisticated control techniques for increased efficiency, these publications together boost our knowledge and development of solar water pumping systems.

Discussing the financial and ecological advantages of switching to solar water pump systems, Ref. 22 explores the application of solar photovoltaic systems in water pumping, offering a detailed examination of advancements and obstacles in the field. It serves as a valuable resource for researchers and professionals seeking insight into smart energy technologies. A thorough analysis of solar photovoltaic-powered pumping systems was given in Ref. 23, which also provided an up-to-date summary of the field’s current status. For solar photovoltaic water pumping systems, Ref. 24 presented a unique metaheuristic algorithm-based MPPT technique coupled with one cycle control, furthering the development of control strategies in such applications. Together, these articles improve our knowledge of the technical, financial, and environmental aspects of solar water pumping systems. They cover sophisticated control methodologies, optimization strategies, and system reviews. Thorough design, simulation, and performance analysis was provided in Ref. 25, which also offered insightful information about the state of the technology today. For water-pumping applications, Ref. 26 offered an innovative solution that integrates power sources in a unique way by suggesting a solar photovoltaic array and brushless DC motor drive fed by the grid. By performing a thorough analysis of Machine Learning (ML)-based Maximum Power Point Tracking (MPPT) approaches, which are useful for obtaining maximum power in solar power systems, Refs. 27 and 28 add more to the body of research. These papers collectively contribute to the ongoing advancement of solar water pumping technologies, addressing technical considerations, environmental impacts, novel system configurations, and advanced control techniques.

The selected MPPT techniques—perturb and observe, incremental conductance, and the beta method—undergo thorough evaluation in this study, aiming to determine their suitability for optimizing the performance of solar water pumps in agricultural applications. The research considers factors such as simplicity, efficiency, and applicability to the specific demands of water pumping in agriculture. Perturb and observe is known for its simplicity, involving small perturbations in the operating point to track maximum power. Incremental conductance adjusts the operating point by considering the conductance of the PV array. The beta method, a derivative of perturb and observe, introduces a variable “beta” to enhance the tracking efficiency.

The outcomes of this study will provide valuable insights into the effectiveness of these MPPT techniques in enhancing the overall performance of solar water pumps, addressing the unique challenges posed by agricultural water pumping. By identifying the most suitable MPPT method, this research aims to contribute to the optimization of solar-powered water pump systems, promoting their widespread adoption and sustainability in the agricultural sector. As MPPT technology continues to evolve, the findings from this study will contribute to the ongoing efforts to improve the efficiency and accessibility of solar-powered solutions in agriculture.^1–3 

The basic block diagram of the solar water pump system is shown in Fig. 1. It consists of an autonomous solar array, an essential DC–DC boosting converter, a three-phase Voltage Source Inverter (VSI), and an induction motor coupled to a centrifugal pump that circulates water. This combined system functions as the testing ground for three different Maximum Power Point Tracking (MPPT) techniques.

The PV array is essential for converting solar energy into electrical energy in the setup that is presented. The three-phase VSI and the DC–DC boost converter are then used to direct the produced electrical power to the water pump. With the aid of the implemented MPPT strategy, the DC–DC converter is essential for maintaining the voltage at the DC-link level. To optimize power extraction, the MPPT controller ensures that the produced solar energy is utilized as efficiently as possible.

To guarantee the rated water flow discharge, the solar water pump system incorporates a v/f (voltage-to-frequency) control technique, specifically implemented for the three-phase VSI. This control method ensures the synchronization of the water pump’s performance with the available solar-generated power. The interaction of the PV array, DC boost converter, three-phase VSI, and induction motor with a centrifugal pump creates a comprehensive system that is used to evaluate various MPPT methods. This experimental setup allows for a thorough examination of the efficiency and effectiveness of these MPPT methods in the context of solar water pump applications.

Table I provides a detailed calculation of all the important parameters for the solar water pump system, including the pump constant, solar PV array, motor pump, and DC boost converter components. The component rating is defined in the first column, and the formulas used to derive the ratings are listed in the second column. The chosen and calculated values for each component are displayed in the third and fourth columns, respectively.

The first step in the motor pump calculation is figuring out how much hydraulic power (Wh) is needed to pump the specified volume of water. Next, the required motor output power is calculated with the pumping system’s 60% efficiency factor taken into account. The solar PV power is derived based on the stated motor power demand. The choice of the PV panel is made based on the rated power required for the motor.

Factors such as DC link voltage, DC link capacitance, needed duty ratio, and inductance are carefully assessed for the DC boost converter. The DC link capacitor is calculated using line voltage, supply current, reference DC voltage, and actual DC voltage. The DC link voltage is obtained by factoring in the input line voltage required for the motor. The needed DC output voltage and the maximum PV voltage are taken into account when calculating duty ratios. PV current, switching frequency, peak PV voltage, and duty ratio are taken into account while determining the inductor’s characteristics.

Finally, the motor’s output power and target speed are factored in to calculate the pump constant. The system is simulated in MATLAB software using all of these parameters, and the outcomes are thoroughly examined while three different MPPT approaches are applied. It is important to remember that, as will be further explained in the section that follows, the control strategy for the motor stays consistent even while the MPPT control technique changes.

Within this system, a comparative analysis employs three distinct MPPT methods: perturb and observe, incremental conductance, and the beta MPPT method. Each of these methodologies is elucidated as follows.

When using the MPPT technique, the system measures the PV panel’s voltage and current before calculating the power the panel produces. Based on the direction of the previous perturbation and the direction of the most recent power increase, the decision-making procedure for the subsequent perturbation is established. The duty ratio is then modified correspondingly, either increasing or decreasing, depending on the identified disturbance.

A visual representation of the perturb and observe algorithm is illustrated in Fig. 2, showcasing the sequential steps and decision points involved in the perturbation process. This algorithm aims to iteratively optimize the operating point of the solar array by continuously perturbing and observing changes in power, ensuring a dynamic adjustment that leads to maximization of power output.

The PV panel’s voltage and current are sensed by the system in this MPPT approach, as shown in Fig. 4. A value for the beta constant is obtained by using these voltage and current data. The two stages of the method’s operation, shown by the range between the minimum and maximum values of beta, depend on this constant beta value. At the first stage, the system intelligently senses the current operating point in proximity to the real Maximum Power Point (MPP). Transitioning to the second stage, the method employs a conventional approach, refining its search to precisely reach the exact maximum power point. This two-stage operation enhances the efficiency and accuracy of the MPPT process, ensuring optimal power extraction from the PV panel.

Efficient operation of an electric drive necessitates effective speed control. One of the simplest methods for achieving this control is through variable voltage- and variable frequency-based strategies shown in Fig. 5. This form of control ensures a seamless adjustment of speed, with the output voltage being directly proportional to the frequency. Consequently, this proportional relationship maintains a consistent motor flux, contributing to the overall efficiency of the drive.

The said system was tested at standard temperature, i.e., 25 °C, and solar irradiance, i.e., 1000 W/m². All three MPPT methods were tested with solar water pumps, and their results are obtained through MATLAB software.

The rated peak voltage (PV) and current for the solar photovoltaic (PV) system are 315.5 V and 8.2 A, respectively, representing the peak operating point on the PV and IV curve. This specific value is expected by all Maximum Power Point Tracking (MPPT) methods. In Fig. 6(a), results from the Perturb and Observe (P and O) MPPT method show that the operating voltage and current settle at 1.97 s, but there is noticeable oscillation at that value. This oscillation could potentially have a negative impact on the performance of the solar pump. On the other hand, Fig. 6(b) displays results obtained using the Incremental Conductance (IC) MPPT method. Here, the operating voltage and current settle more quickly, at 1.1 s, than P and O MPPT. Although there is still some oscillation, it is less pronounced than in the P and O method. Similar results are observed in Fig. 6(c) for the beta MPPT method. The settling of operating voltage and current is similar to that in P and O MPPT, but the oscillation is close to negligible. This suggests that the beta MPPT method has a more positive impact on the performance of the solar water pump than P and O MPPT.

In summary, while all three MPPT methods achieve the expected operating voltage and current, the beta MPPT method stands out for its quicker settling time and minimal oscillation. These characteristics indicate that the beta MPPT method may contribute to an improved overall performance of the solar water pump, making it a potentially more effective choice than the P and O and the IC MPPT methods.

According to the rated values of PV voltage (315.5 V) and current (8.2 A), the required power for the PV system is calculated to be 2587 W, representing the peak operating point on the power vs PV curve. This expected power value is consistent across all MPPT methods. In Figs. 7(a) and 7(b), the power drawn by the Perturb and Observe (P and O) and Incremental Conductance (IC) MPPT algorithms exhibits noticeable oscillations at higher values. Consequently, the efficiency of power conversion fluctuates within the range of 80%–95%. However, in the case of the beta MPPT method, as depicted in Fig. 7(c), power oscillation is minimal, and the power conversion efficiency is nearly 98%. This indicates that the beta MPPT method is more stable and efficient in maintaining power output without significant fluctuations.

In summary, while the P and O and the IC MPPT methods result in larger power oscillations and variable conversion efficiencies, the beta MPPT method demonstrates superior stability with negligible power oscillation and a consistently high power conversion efficiency of around 98%.

The DC link voltage for the converter is calculated to be 400 V, as indicated in Table I. This target value is pursued using various MPPT algorithms, and the results are presented in Figs. 8(a)–8(c). All three algorithms successfully achieve the required DC link voltage, but the IC MPPT method exhibits a faster response in settling. When it comes to oscillations, the beta MPPT method stands out, displaying fewer ripples in the DC link voltage. This characteristic contributes to a more efficient and reliable supply to the Voltage Source Inverter (VSI) of the inverter system.

To further analyze the impact of the DC link voltage, Fast Fourier Transform (FFT) analysis is conducted, and the results are discussed in detail below. This analysis provides insights into the frequency components and stability of the DC link voltage obtained through different MPPT algorithms.

In the scenario of Perturb and Observe (P and O) MPPT, the significant oscillations in its operating voltage and current contribute to a higher ripple in the DC link voltage. Consequently, the Total Harmonic Distortion (THD) for the Voltage Source Inverter (VSI) voltage is notably elevated, measuring 117.69%. The fundamental value of the VSI voltage is recorded at 219.3 V, as depicted in Fig. 9(a).

Examining the current characteristics, illustrated in Fig. 9(b), the fundamental value of the current is measured at 12.3 A, accompanied by a THD value of 8.15%. These findings highlight the impact of P and O MPPT on the DC link voltage ripple, subsequently influencing the harmonic content in both voltage and current waveforms of the VSI.

In the context of Incremental Conductance (IC) MPPT, the operating voltage and current exhibit noticeable oscillations, contributing to a slightly increased ripple in the DC link voltage. As a result, the Total Harmonic Distortion (THD) for the Voltage Source Inverter (VSI) voltage is measured at 117.35%. The fundamental value of the VSI voltage is identified as 220.2 V, as depicted in Fig. 10(a).

Analyzing the current characteristics, presented in Fig. 10(b), the fundamental value of the current is recorded at 12.37 A, accompanied by a THD value of 9.72%. These observations underscore the impact of IC MPPT on the DC link voltage ripple, which subsequently influences the harmonic content in both voltage and current waveforms of the VSI.

For the beta MPPT method, the operating voltage and current exhibit nearly negligible oscillations, resulting in a DC link voltage that is nearly ripple-free. Consequently, the Total Harmonic Distortion (THD) for the Voltage Source Inverter (VSI) voltage is measured at 115.91%. The fundamental value of the VSI voltage is determined to be 234.6 V, as illustrated in Fig. 11(a).

Examining the current characteristics, as depicted in Fig. 11(b), the fundamental value of the current is recorded at 12.14 A, accompanied by a THD value of 6.37%. These findings emphasize the superior stability of the beta MPPT method, leading to minimal oscillations in operating parameters and consequently resulting in reduced harmonic distortion in both voltage and current waveforms of the VSI.

In Fig. 12, the outcomes of motor speed and electromagnetic torque are illustrated for all three MPPT methods. Once again, the Incremental Conductance (IC) MPPT method demonstrates a swift response compared to the others. However, it is noteworthy that the beta MPPT method exhibits minimal torque ripple, distinguishing it from the other methods.

In the evaluation of the three MPPT methods [Perturb and Observe (P and O), Incremental Conductance (IC), and beta] for a solar water pump system, the following key findings have been observed:

1. P and O MPPT:

   • Results in noticeable oscillations in operating voltage and current.

   • High ripple in DC link voltage.

   • Elevated Total Harmonic Distortion (THD) in VSI voltage and current waveforms.

2. IC MPPT:

   • Displays faster response than P and O MPPT.

   • Exhibits noticeable oscillations in operating voltage and current.

   • Higher THD in VSI voltage and current, although slightly improved compared to P and O.

3. Beta MPPT:

   • Minimal oscillations in operating voltage and current.

   • Almost ripple-free DC link voltage.

   • Lower THD in VSI voltage and current, indicating improved stability.

Considering these findings, the beta MPPT method emerges as the most favorable choice. It demonstrates a well-balanced performance with minimal oscillations, low ripple in the DC link voltage, and reduced THD in VSI voltage and current. The beta MPPT method not only achieves the desired operating points efficiently but also contributes to a more stable and reliable operation of the solar water pump system.

In summary, the beta MPPT method is suggested as the most suitable choice for optimizing the performance of the solar water pump system.

Implementing various Maximum Power Point Tracking (MPPT) techniques in agricultural scenarios presents both hurdles and opportunities. Hurdles include the variability of environmental conditions such as weather and shading, complex system integration requirements, maintenance challenges, cost constraints, and the need for knowledge dissemination among farmers. However, these hurdles are accompanied by opportunities such as increased efficiency in power generation, environmental sustainability through renewable energy adoption, remote monitoring capabilities for improved system management, potential revenue streams from excess energy production, and eligibility for government incentives. With careful planning, investment, and support, the implementation of MPPT techniques in agriculture has the potential to enhance energy management practices, promote sustainability, and improve economic outcomes for farmers worldwide.

The setup expenses for integrating various MPPT methods in agricultural settings encompass the initial investment in MPPT equipment, including controllers, sensors, and solar panels, as well as the associated installation costs and potential expenditures on training and knowledge dissemination for farmers and technicians. These expenses constitute a crucial aspect of implementation, requiring careful consideration to ensure the economic viability and long-term benefits of adopting MPPT techniques in agricultural scenarios.

Maintenance needs for MPPT systems in agricultural settings involve regular upkeep tasks such as cleaning solar panels, inspecting wiring and connections, and monitoring system components for wear and tear. In addition, access to technical support services and periodic software updates may be necessary to ensure optimal performance and address any issues that arise over time. Proper maintenance practices are essential to maximize the efficiency and longevity of MPPT systems, contributing to their long-term effectiveness and sustainability in agricultural operations.

Long-term energy conservation benefits of integrating MPPT methods in agricultural settings are significant as these techniques optimize solar power systems to maximize energy output over time. By continuously tracking and optimizing power production, MPPT systems contribute to increased efficiency, reduced reliance on fossil fuels, and lower greenhouse gas emissions, leading to environmental sustainability. Moreover, the cost savings achieved through improved energy utilization can enhance the financial viability of agricultural operations, making MPPT integration a valuable investment for long-term energy conservation and economic sustainability.

In conclusion, while integrating MPPT methods in agricultural settings involves initial setup expenses and ongoing maintenance needs, the long-term benefits in terms of energy conservation and cost savings make it a viable option. By carefully assessing setup costs, implementing proper maintenance practices, and considering the long-term energy conservation benefits, integrating MPPT techniques can be a valuable investment for agricultural operations.

Enhancing water pump efficiency in agriculture presents a dual advantage of reducing carbon emissions and preserving water resources. By improving the efficiency of water pumps, farmers can decrease energy consumption for irrigation, thereby lowering the carbon footprint associated with electricity generation or diesel-powered pumps. Concurrently, optimized water delivery systems minimize water wastage, ensuring more effective utilization of this vital resource. This not only conserves water but also fosters environmental sustainability by alleviating strain on natural water sources and promoting resilience in regions susceptible to water scarcity or drought conditions. Overall, investing in efficient water pump technologies contributes to both environmental protection and agricultural sustainability, offering significant benefits for farmers and ecosystems alike.

The authors express their gratitude to the leadership at YCCE, Nagpur, for providing inspiration and encouragement to undertake research work in the field of agriculture.

The authors have no conflicts to disclose.

Atul S Lilhare: Conceptualization (equal); Formal analysis (equal); Investigation (equal); Methodology (equal); Software (equal); Validation (equal); Writing – original draft (equal). Sumant G Kadwane: Supervision (equal); Writing – review & editing (equal).

The data that support the findings of this study are available within the article.