New Developed Wind Pumping System

Abstract

In this paper a new wind pumping system is developed. This system is hybrid between mechanical and electrical wind pumping systems. It combines the advantages of these two systems. The developed wind pumping system consists of wind turbine, special gearbox, DC machine, battery bank, and water pump. Three wind pumping systems have been modeled and then simulated by using MATLAB/SIMULINK. The simulation results show that the developed wind pumping system has the best performance. Thus, the extracted water volume of the developed system is 984.1 m³, where mechanical and electrical systems extract 737.2 and 642.9 m³ respectively.

Keywords

Water pump wind turbine DC motor battery bank gear box MATLAB/SIMULINK

Introduction

Water is one of the basics of life, which is used for dirking and for Farming. Many civilizations are founded on the sources of water, such as the Ancient Egyptians on the Nile or the Ancient India, who based on the Indus River. Many water-related occur and continue to occur, for example Egyptian-Ethiopian conflict about Grand Ethiopian Renaissance Dam.

People whom live in desert, they suffer too much from a lack of water that because the dry climate there. Only groundwater extraction can provide a steady supply of water for these people. The water can be extracted through a well drilled into the aquifer, then pumping it by using water pump.

Almost water pumps are driven by electrical motor. Usually, remote areas don’t have the access for electricity, for this reason Wind pumping systems are one of few solutions to solve this problem.

There are two types of water pumping systems (WPS): Mechanical WPS (MWPS) and Electrical WPS (EWPS), each system has its advantages and its disadvantages. In this paper a new wind pumping system is proposed, it integrates the advantages of the MWPS and the EWPS into one system. The paper is organized as follows: firstly, the three wind pumping systems are presented, then they are modeled by using MATLAB/SIMULINK, finally the simulation and comparison results are discussed.

Mechanical wind pumping system

The use of wind energy begins in antiquity. Wind turbine was a major system for transportation, grinding grain, and pumping water before the invention of the steam engine (Nelson, 2013). Farm windmills were main factors for Great Plains of the United States. From 1850 on, water pumping windmills were manufactured in the tens of thousands (Nelson, 2013).

As shown in Figure 1, the mechanical wind pumping system (MWPS) contains wind turbine integrated with vertical piston motion through gear box to extract water from the well (Aized et al., 2019; Ziter, 2009). As illustrated in Figure 2 (Jaramillo et al., 2010),The water pump of this system needs high torque, for this reason, the type of the wind turbine that uses in MWPS is the American windmill which has 15–20 blades to provide high torque and operation at low starting wind speeds

Figure 1.

Mechanical wind pumping system.

Figure 2.

Different wind turbines.

The main advantage of this pumping system is the high power efficiency. Specifically, the efficiency of the power conversion is high, that because only the mechanical losses of the gear box and the water pump are considered in this system that means.

On the other hand, the disadvantages of this system are:

Low rotor power coefficient (0.3 as illustrated in Figure 2).

Only one source is used to pump the water, if there is now wind speed or the tip-ratio speed is over than 2 (Figure 2) the pumping system stops.

Electrically wind pumping systems

There are different structures of electrical wind pumping systems (EWPS). For example (Gam et al., 2018) proposed a system contains wind turbine connect to induction generator, this generator associated with rectifier than inverter, the output of the inverter connects to induction motor that integrates with a pump.

Zeddini et al. (2013) used the same design of (Gam et al., 2018) but they replaced the rectifier and the inverter by using a frequency regulator.

Barara et al. (2013) used only rectifier to turn a DC motor that couples with a pump.

All previous works didn’t use a storage system to store the excess power then used it in case of no wind power. On the other side, (Issad et al., 2018; Lara et al., 2011) put a battery bank between the rectifier and the inverter as shown in Figure 3. Other studies integrated PV on the DC bus such as (de Oliveira Ferreira et al., 2020; Poompavai and Kowsalya, 2019).

Figure 3.

Electrical wind pumping system.

This system uses the tree blades wind turbine. As illustrated Figure 2, this kind of wind turbine can provide the highest rotor power coefficient.

The advantages of the EWPS are:

The rotor power coefficient of the wind turbine is the higher compared with the other kind of wind turbines as shown in Figure 2.

The generated voltage and frequency of the induction generator are controllable thanks to the rectifier and the inverter.

The generated electrical power can be stored in the battery bank.

On the other side, the disadvantages of the EWPS are:

The rotor the tip-speed of the wind turbine of this system must be more than 5, which means the low wind speed can’t be useable as American windmill.

The power electronics, generator and motor reduce the efficiency of mechanical power that produced by the wind turbine.

Novel hybrid wind pumping system

The originality of this project is developed a new water pumping system. This system combines the advantages of the mechanical and the electrical systems. The developed wind pumping system consists of a wind turbine, a water pump, a DC machine, and a battery bank. Furthermore, the role of the wind turbine is transform aerodynamic power to mechanical power; this power can be used to drive the pump and to supply DC machine for electricity storage.

The DC machine is used to charge the battery bank in case that the wind turbine produces more power than the water pump needs.

On the other hand, if the wind turbine can’t satisfy the mechanical power of the water pump, the battery bank supply the DC machine to deliver a mechanical power to support the wind turbine for satisfying the power demand of the water pump (Figure 4).

Figure 4.

Novel hybrid wind pumping system.

The goal of this developed system is to increase the efficiency coefficient by reducing the power losses and storing the excess power.

Models of the wind pumping systems

The three wind pumping systems are simulated in MATLAB/SIMULINK. Furthermore, to make the comparison between these systems, the sizing and the model of the water pump, the water tank, the wind turbine, and the battery bank are the same.

Modeling of the water pump and storage tank

There are different types of water pumps, such as centrifugal pump and cylindrical pump … etc. The traditional mechanical wind pumping system uses cylindrical pump and the electrical system uses centrifugal pump. In general, the relationship of the hydraulic pumping power P_pump (W) and the water flow output of a pump Q (m³/s) is:

Q_{pump} = \frac{P_{pump}}{ρ_{water} . g . h}

(1)

Where, ρ_water is water density (kg/m³), g is gravity (m²/s), and h is pumping height (m).

The relationship between mechanical power that drives a pump P_mec (W) and P_pump is:

P_{pump} = η_{pump} . P_{mec}

(2)

Where, η_pump is efficiency of pumping power.

The water tank has water inflow and outflow, which are pump water flow and consumed water respectively. The volume of the stored water V_water (m³) can be represented as follows:

V_{water} = \int_{0}^{V_{water_\max}} (Q_{pump} - Q_{outflow}) dt

(3)

The parameters values of the water pump and the water tank are presented in the following Table 1.

Table 1.

Parameters of the water pump and the tank.

Parameter	Value
Water density	1000 kg/m³
Gravity	9.81 m²/s
Pumping height	25 m
Pumping efficiency	0.55
Maximum power of the pump	3 kW
Maximum water volume of the tank	200 m³

Modeling of the wind turbine

Figure 5 represents mechanical power of wind turbine as function of wind speed. Moreover, if wind speed is higher than cut-in (3 m/s) speed and less than or equal nominal speed (12 m/s) cut-out speed so the rated power is maintained. If wind speed between nominal speed and cut-out speed (16 m/s) here the mechanical power is steady on maximum power (10.90 kW). If the wind speed becomes higher than cut-out, the wind turbine is stopped. The mechanical rated power of the wind as follows (Achour et al., 2016, 2017):

P_{Wind} = \frac{1}{2} . C_{p} . ρ_{air} . A . V_{wind}^{3}

(4)

Figure 5.

Wind power and wind speed curve.

Where, C_p is power coefficient, ρ_air air density (kg/m³), A is area of windswept (m²), and V_wind is wind speed (m/s). The output power P_wind presents the total produced power of the wind turbine coupled with gear box. To size the wind turbine, we proposed that the maximum power of the wind turbine P_{wind_max} equals the double value of the pump maximum power (equation (5)).

P_{\max_wind} = 2 . P_{mec} = 2 \times \frac{3}{0.55} = 10.90 kW

(5)

The parameters values of the wind turbine are given in Table 2.

Table 2.

Parameters of the wind turbine.

Parameter	Value
Cut-in	3 m/s
Cut-out	16 m/s
Power coefficient	0.59
Air density	1.225 kg/m³
Area of windswept	7.682 m²
Maximum power of the wind turbine	10.90 kW

Modeling of the battery bank

The stored energy Q_b (W/s) and the stat of storage SOC of battery bank like next equations: can be written as following equations (Achour et al., 2015):

Q_{b} = \int_{0}^{Q_{b_\max}} P_{b} dt

(6)

SOC = \frac{Q_{b}}{Q_{b_\max}} . 100 %

(7)

Where, Q_{b_max} is maximum stored energy (40,000 W/h), P_b is battery power (if P_b > 0, the battery is charging, if P_b < 0 the battery is discharging).

Mechanical wind pumping system SIMULINK model

Figure 6 presents the SIMULINK model of the MWPS. The input of the water pump is the generated mechanical power of the wind turbine. On the other hand, the outflow of the water tank is steady at 35 m³/h.

Figure 6.

Mechanical wind pumping system SIMULINK model.

Electrical wind pumping system SIMULINK model

As illustrated in Figure 7, the SIMULINK model of the water pump and the water tank of the EWPS is the same model of the MWPS. On the other side, the mechanical power supply of the water pump is produced from the AC motor P_acmotor. The relationship between P_acmotor and P_mec as follows:

P_{mec} = η_{mec} . P_{acmotor}

(8)

Figure 7.

Electrical wind pumping system SIMULINK model.

Where, η_mec is efficiency of the AC motor mechanical power.

The inverter converts DC power of the DC bus P_dcbus to AC power to supply the AC motor. This conversion can be represented by the following equation:

P_{ac_motor} = η_{inv} . P_{dcbus}

(9)

Where, η_inv is the inverter efficiency.

The wind turbine generator is connected to the battery bank on the DC bus through the rectifier and the buck-boost converter. DC power of the DC bus can be represented as follows:

P_{dcbus} = (η_{rec} . η_{acgen} . P_{wind}) + (η_{bucbos} . P_{b})

(10)

Where, η_rec is the rectifier efficiency, η_acgen is efficiency of the AC generator electrical power, and η_bucbos is the buck-boost efficiency.

The input of the power control (P_control) of the battery bank is the power value of charging or discharging. When the wind turbine generator with electrical and mechanical losses produces more power than the water pump needs (3 kW), in this case the excess power is charged in the battery bank. On the other hand, if the wind turbine generator cannot produces effective power to drive the water pump, the battery bank helps it.

This operation can be translated to the following equation:

P_{control} = \frac{(η_{acgen} . η_{rec} . P_{wind}) - (\frac{P_{pum p_{\max}}}{η_{inv} . η_{acmotor} . η_{pump}})}{η_{bucbos}}

(11)

Mecha-electrical wind pumping system SIMULINK model

The proposed name of this developed system is mecha-electrical pumping system MEPWS. The SIMULINK model of MEPWS is represented in Figure 8. The water pump model stills the same. In the other side, the mechanical power supply system is the combination between mechanical and electrical systems. Moreover, the wind turbine can deliver directly the mechanical power to the water pump and it can charge the battery bank through the DC machine.

Figure 8.

Developed wind pumping system SIMULINK model.

The DC machine can be used as DC motor in the case when the wind turbine can’t produce enough mechanical power to satisfy the water pump demand. In this case, the battery bank is used as electrical source to supply the DC machine.

The mechanical power equation of this system as follows:

P_{mec} = P_{wind} + (η_{bucbos} . η_{dcmach} . P_{b})

(12)

Where, η_acgen is efficiency of the DC machine electrical power.

The power control input of the battery bank is the power value of charging or discharging. When the wind turbine produces more power than the water pump needs (3 kW), in this case the excess power is charged in the battery bank through the DC generator. On the other hand, if the wind turbine cannot produces effective power to drive the water pump, the DC motor helps it.

The equation of this operation as follows:

P_{control} = \frac{P_{wind} - (\frac{P_{pum p_{\max}}}{η_{pump}})}{η_{bucbos} . η_{dcmach}}

(13)

Simulation results

Figure 9 shows the simulated wind speed that is applied on the wind turbine of the three pumping systems in 1 day. To make these systems work in real conditions, the wind speed is fluctuated all the time. Thus, the wind turbine produces instable mechanical power as shown in Figure 10. In addition, between 0 and 1 hours the wind speed was 8.5 m/s and the power was 4215 W; between 1 and 2 hours the wind speed increased to 11 m/s so the power upped to 9136 W; between 2 and 5 hours, the power was in maximum value that because the wind speed was fluctuating in the interval of nominal and cut-out speed; between 5 and 11 hours the power start decreases from 6460 to 2354 W; between 11 and 12 hours the power is 6864 W, then it reached the maximum value 10,900 W (between 12 and 13); after that, the wind speed decreased to 10.5 m/s and the power was 7946 W; between 13 and 24 the wind speed was very slowly and decreasing, where the maximum wind speed in this interval was 8.5 m/s and the minimum value was 4 m/s. Thus, the mechanical power was very low in this interval (4366 W and 910.5 W respectively).

Figure 9.

Wind speed profile.

Figure 10.

Wind turbine mechanical power.

Figures 11 and 12 represent the produced mechanical power and used mechanical power by the pump respectively. As mentioned before, the maximum power that drives the water pump is 3 kW. Thus, in the two figures the power of electrical and developed system was equal or down 3 kW, that because the excess power was storing in the battery bank. In the other side, the additional produced power of the mechanical system was not utilizable by the water pump.

Figure 11.

Produced power.

Figure 12.

Used power by the water pump.

Comparing with the mechanical and the electrical systems, the produced mechanical power of the developed system was stable on 3 kW almost time (between 1 and 22 hour); on the other times, precisely, between 0 and 1 hour the produced power of mechanical and developed systems were 2318 W where the electrical pumping system produced 1512 W; between 22 and 23, the power of mechanical and developed systems were 1240 W where the electrical pumping system produced 808.7 W; between 23 and 24, the power of mechanical and developed systems decreased to 500.8 W where the electrical pumping system produced 325.5 W.

Figure 13 shows that the power charge in the developed system was greater than of it in electrical system. Thus, the state of charge of developed system was stiffing compared with the electrical system Figure 14.

Figure 13.

Power of battery bank.

Figure 14.

Battery bank storage.

Figure 15 illustrates that the inlet water flow of the Mecha-Electrical system was stable (about 0.0122 m³/s) almost time of filling the tank (between 1 and 22 hour). On the other side, the water flows of the other systems were fluctuated under 0.0122 m³/s.

Figure 15.

Inlet water flow.

As final result and as illustrated in Figure 16, the stored water of MEWPS was extremely higher than that of the mechanical and electrical systems. In addition, the total stored water volume of the developed system was 984.1 m³, where the mechanical and electrical system stored 737.2 m³ and 642.9 m³ respectively.

Figure 16.

Water tank storage.

Conclusion

The Mecha-electrical wind pumping system (M-EWPS) proved its effectiveness to minimize the power losses and to save the power, which makes it a new generation of wind pumping system. This paper represents the first step to build this system, and this could be an opportunity for researchers to carry on works in order to improve this powerful pumping system.

In this paper MWPS, EWPS and M-EWPS have been described, after that, the three pumping systems have been modeled and simulated.

The simulation results prove that the M-EWPS can extract and store the water more than MWPS and EWPS.

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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