International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1765

ISSN 2229-5518

An Efficient Solar Pumping System for Rural

Areas of Bangladesh

Md. Habib Ullah, Tanvir Ahmad, Md. Niaz Morshedul Haque, Md. Jakaria Rahimi, Ripan Kumar Dhar

Abstract— This research deals with the design and simulation of a simple but efficient photovoltaic water pumping system for rural areas of Bangladesh. The main objectives were to get a cost effective and efficient system employing MPPT. To keep the cost minimized some design consideration are presented. Presently used Buck converter based MPPT is compared with more efficient Buck boost and Cuk converter topologies. The simulations perform comparative tests using actual irradiance data for Bangladesh. The results showed a very compact and efficient result can be obtained the proposed topology including Cuk converter based MPPT.

Index Terms— DC-DC converters, MPPT, PV modules, Solar pumping, Simulation modeling.

——————————  ——————————

1 INTRODUCTION

In a country like Bangladesh where farming is one of the strongest pillars of the economics, irrigation system should be very well-equipped and should be managed well. In
doing so, we have to ensure adequate supply of electrical power for water pumping as per requirement. In general, AC powered system is economic and takes minimum maintenance when AC power is available from the nearby power grid. However, Due to severe crisis of electricity in Bangladesh at present we have to find some efficient way to resolve this problem. Windmills have been installed traditionally in many rural areas of different places in the world, where water sources are spread over many miles of land and power lines are scarce: many of them are however, inoperative now due to lack of proper maintenance and age. Today, many stand-alone type water pumping systems use internal combustion engines. These systems are portable and easy to install. However, they have some major disadvantages, such as: they require frequent site visits for refueling and maintenance, and furthermore diesel fuel is often expensive and not readily available in rural areas of many developing countries. The consumption of fossil fuels also has an environmental impact, in particular the release of carbon dioxide (CO2) into the atmosphere. CO2 emissions can be greatly reduced through the application of renewable energy technologies, which are already cost competitive with fossil fuels in many situations. Good examples include large-scale grid-connected wind turbines, solar water heating, and off-grid stand-alone PV systems [1]. The use of renewable energy for water pumping systems is, therefore, a very attractive proposition. Windmills are a long- established method of using renewable energy; however they are quickly phasing out from the scene despite success of large

————————————————

 Md. Habib Ullah , Department of Electrical and Electronics Engineering, Ahsanullah University of Science and Technology, Bangladesh, PH-+8801675842410. E-mail: imshouruv@gmail.com

 Md. Jakaria Rahimi, Assistant professor, Department of Electrical

and Electronics Engineering, Ahsanullah University of Science amd

Technology, Dhaka, Bangladesh. E-mail: mjrahimi@gmail.com

 Tanvir Ahmad, E-mail: tanvir_165@yahoo.com

 Md. Niaz Morshedul Haque, Email- morshedul.haque@btraccl.com

scale grid-tied wind turbines. PV systems are highly reliable and are often chosen because they offer the lowest life-cycle cost, especially for applications requiring less than 10KW, where grid electricity is not available and where internal- combustion engines are expensive to operate [1]. If the water source is 1/3 mile (app. 0.53Km) or more from the power line, PV is a favorable economic choice [2].
A great deal of research has been done to improve the efficiency of the PV modules. A number of methods of how to track the maximum power point of a PV module have been proposed to solve the problem of efficiency and products using these methods have been manufactured and are now commercially available for consumers [3]. As the market is now flooded with varieties of these MPPT that are meant to improve the efficiency of PV modules under various insulations conditions it is not known how many of these can really deliver on their promise under a variety of field conditions.
In our research, the primary goal was to develop an efficient cost effective water pumping system run by solar power, which will be optimized specially for the rural areas of Bangladesh. In doing so firstly we tried to use minimum number of components to minimize cost and losses. Then investigated if the MPPT that are said to be highly efficient and do track the true maximum power point under the various conditions in a country like Bangladesh [3].
In our research, the Boost converter is not considered as it is inferior than others while proving large initial current reducing the voltage lower than its input, which is very much desired at starting.

2 DESIGN CONSIDERATION

To develop a cost effective solar powered pumping system following points are taken in to consideration.

2.1 Alternative Storage: Excluding the battery

Needless to say, photovoltaic are able to produce electricity only when the sunlight is available, therefore stand-alone systems obviously need some sort of backup energy storage which makes them available through the night or bad weather conditions. The most popular solution of using batteries has a

IJSER © 2013 http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1766

ISSN 2229-5518

number of disadvantages. The type of lead-acid battery suitable for PV systems is a deep-cycle battery [4], which is different from one used for automobiles, and it is more expensive and not widely available. Battery lifetime in PV systems is typically three to eight years, but this reduces to typically two to six years in hot climate since high ambient temperature dramatically increases the rate of internal corrosion [3]. Batteries also require regular maintenance and will degrade very rapidly if the electrolyte is not topped up and the charge is not maintained. They reduce the efficiency of the overall system due to power loss during charge and discharge. Typical battery efficiency is around 85% but could go below 75% in hot climate [3]. From all those reasons, experienced PV system designers avoid batteries whenever possible. The additional cost of reservoir is considerably lower than that incurred by the battery equipped system.

2.2 The use of DC pump: excluding the inverter

It helps in two stages i) exclusion of inverter thus reducing price significantly ii) A robust load matching using maximum power transfer theorem.

2.3 MPPT tracking

When a PV module is directly coupled to a load, the PV module’s operating point will be at the intersection of its I–V curve and the load line w
hich is the I-V relationship of load. For the equivalent circuit in
Figure 3-1, a resistive load has a straight line with a slope of

1/Rload as shown in Figure 3-2. In other words, the impedance of load dictates the operating condition of the PV module.

In general, this operating point is seldom at the PV module’s MPP, thus it is not producing the maximum power. A study shows that a direct-coupled system utilizes a mere
31% of the PV capacity. A PV array is usually oversized to compensate for a low power yield during winter months. This mismatching between a PV module and a load requires further over-sizing of the PV array and thus increases the overall system cost. To mitigate this problem, a maximum power point tracker (MPPT) can be used to maintain the PV module’s operating point at the MPP. MPPTs can extract more than 97% of the PV power when properly optimized [6].

2.4 Choosing the Best MPPT Tracker

A MPPT is used for extracting the maximum power from the solar PV module and transferring that power to the load [8, 9].
The heart of MPPT hardware is a switch-mode DC-DC converter. It is widely used in DC power supplies and DC motor drives for the purpose of converting unregulated DC input into a controlled DC output at a desired voltage level [10]. MPPT uses the same converter for a different purpose: regulating the input voltage at the PV MPP and providing load matching for the maximum power transfer.
Many MPPT techniques have been proposed in the literature; example are the Perturb and Observe (P&O) methods [8, 11-14], Incremental Conductance (IC) methods [6,
12], Fuzzy Logic Method [8, 11, 15], etc. In this paper two most popular of MPPT technique (Perturb and Observe (P&O) methods and Incremental Conductance methods) and three
different DC-DC converter (Buck, Boost and Cuk converter) is compared to get the optimum solution of MPPT.

3 DC-DC CONVERTERS

3.1 Buck Converter

The buck converter can be found in the literature as the step down converter [5]. This gives a hint of its typical application of converting its input voltage into a lower output voltage, where the conversion ratio M =Vo/Vin varies with the duty ratio D of the switch [4, 5].

Fig. 1. Equivalent circuit of a Buck converter.

D=Duty cycle;
Vo/Vin=D; Io/Iin=1/D; So, from these two equations, Rin= Vin/Iin= (1/D2) × (Vo/ Io) = (1/D2) × Rload;

3.2 Boost Converter

The boost converter is also known as the step-up converter. The name implies it’s typically application of converting a low input voltage to a high output voltage, essentially functioning like a reverse buck converter.

Fig. 2. Equivalent circuit of a Boost converter.

D=Duty cycle; Vo/Vin=1/ (1-D);
Io/Iin=1-D; So, from these two equations, Rin= Vin/Iin= (1-D2) × (Vo/ Io) = (1-D2) × Rload;

3.3 Buck-Boost Converter

It’s the combination of Buck & Boost as follows

Fig. 3. Equivalent circuit of a Buck-Boost converter.

IJSER © 2013 http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1767

ISSN 2229-5518

Now, D=Duty cycle; Vo/Vin=D/ (1-D); Io/Iin=(1-D)/D; So, from these two equations,
The DC pump can be characterized by following equation as per the Simulink simulation results.
Rin= Vin/Iin= [D2/(1-D2)] × (Vo/ Io) = [D2/ (1-D2)] × Rload;

-5 3

= 9.5 × 10 .

-3

8.7 × 10

. V 2

+ 0.37. V + 0.2

3.4 Cuk Converter

0ad

0 0 0

TABLE 2

Please The Cuk converter uses capacitive energy transfer and analysis is based on current balance of the capacitor. Cuk converter will responsible to invert the output signal from positive to negative or vice versa.

Fig. 4. Equivalent circuit of a Cuk converter.

Now, D=Duty cycle; Vo/Vin=D/ (1-D); Io/Iin=(1-D)/D; So, from these two equations,
Rin= Vin/Iin= [D2/(1-D2)] × (Vo/ Io) = [D2/ (1-D2)] × Rload;

4 SIMULATION CONSIDERATION

According to Irradiance data of Bangladesh, it varies from
200W/m2 to 1000W/ m2 at day time from 6 am to 6 pm in the
month of June [16]. In our simulation we have simulated the
circuit for 5 different stages in this range. The solar panel
taken in consideration has specification as in Table 1.

TABLE 1

PV PANEL SPECIFICATION

CONVERTER DESIGN SPECIFICATIONS

5 SIMULATION RESULT

First the capabilities of the three converters are compared to trace the MPPT properly with the variation of input irradiance and also input module voltage.

(a) PV Power vs. Voltage

160

140

120

100

80

60

40

20

0

0 5 10 15 20 25 30 35 40 45 50

Module Voltage (V)

Fig. 6. The MPPT tracking using Buck converter.

(b) PV Current vs. Voltage

5

4

3

2

1

0

0 10 20 30 40 50

Module Voltage (V)

Fig. 5. Kyocera SD 12-30 water pump performance chart [2].

Fig. 7. The MPPT tracking using Buck converter.

IJSER © 2013 http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1768

ISSN 2229-5518

160

(c) Output Power vs. Duty Cycle

(b) PV Current vs. Voltage

5

140

4

120

100 3

80

60 2

40

1

20

0

0 0.2 0.4 0.6 0.8 1

Duty Cycle

0

0 10 20 30 40 50

Module Voltage (V)

Fig. 8. The output power curve of Buck converter.

Fig. 11. The MPPT tracking using Buck-Boost converter.

(d) Output Current vs. Voltage

6

160

(c) Output Power vs. Duty Cycle

140

5

120

4

100

3 80

2

1

0

0 5 10 15 20 25 30 35

Output Voltage (V)

60

40

20

0

0 0.2 0.4 0.6 0.8 1

Duty Cy cle

Fig. 9. The output current curve of Buck converter.

Fig. 12. The output power curve of Buck-Boost converter.

150

(a) PV Power vs. Voltage

(d) Output Current vs. Voltage

6

5

4

100

3

50 2

1

0

0 10 20 30 40 50

Module Voltage (V)

0

0 5 10 15 20 25 30 35

Output Voltage (V)

Fig. 10. The MPPT tracking using Buck-Boost converter.

Fig. 13. The output current curve of Buck-Boost converter.

IJSER © 2013 http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1769

ISSN 2229-5518

150

(a) PV Power vs. Voltage

(d) Output Current vs. Voltage

6

5

4

100

3

50 2

1

0

0 10 20 30 40 50

Module Voltage (V)

0

0 5 10 15 20 25 30 35

Output Voltage (V)

Fig. 14. The MPPT tracking using Cuk converter.

Fig. 17. The output current curve of Cuk converter.

(b) PV Current vs. Voltage

5

4

TABLE 3

OUTPUT DATA FOR BUCK CONVERTER

3

2

1

0

0 10 20 30 40 50

Module Voltage (V)

Fig. 15. The MPPT tracking using Cuk converter.

TABLE 4

OUTPUT DATA FOR BUCK-BOOST CONVERTER

160

140

120

(c) Output Power vs. Duty Cycle

100

80

60

40

20

0

0 0.2 0.4 0.6 0.8 1

Duty Cy cle

Fig. 16. The output power curve of Cuk converter.

IJSER © 2013 http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 8, August-2013 1770

ISSN 2229-5518

TABLE 5

OUTPUT DATA FOR CUK CONVERTER

So, we can see that the Buck-Boost converter configuration and Cuk converter configuration is properly tracking the maximum power point but not the buck converter. Figure 6 to figure 17 and table 3 to 5 were obtained by using Matlab coding.

6 CONCLUSION

In this research work, to find out an optimal solution for solar dc pumping system for Bangladesh, we have observed some remarkable findings through simulation to optimize the performance of solar dc pumping. Firstly we have found that to harness the power from solar panel efficiently we can use either the Buck-Boost or Cuk converter to track the MPPT very efficiently. In terms of efficiency and cost-effectiveness the Cuk converter is the best solution. So using a very compact topology of Cuk MPPT tracker followed by the DC motor with proper rating of solar panel can serve the purpose of solar pumping very efficiently. In future we are going to implement the topology to check out the actual throughput of the pump and its effectiveness.

REFERENCES

[1] Thompson, Marry A. Reverse-Osmosis Desalination of Seawater Powered by Photovoltaics Without Batteries Doctoral Thesis, Loughborough University, 2003W.-K. Chen, Linear Networks and Systems. Belmont, Calif.: Wadsworth, pp. 123-135, 1993. (Book style)

[2] Kyocera Solar Inc. Solar Water Pump Applications Guide 2001 (downloaded from www.kyocerasolar.com)

[3] BP Solar BP SX150 - 150W Multi-crystalline Photovoltaic Module

Datasheet, 2001

[4] Messenger, Roger & Jerry Ventre Photovoltaic Systems Engineering 2nd

Edition CRC Press, 2003

[5] Masters, Gilbert M. Renewable and Efficient Electric Power Systems John

Wiley & Sons Ltd, 2004

[6] Hohm, D. P. & M. E. Ropp “Comparative Study of Maximum Power Point Tracking Algorithms” Progress in Photovoltaics: Research and Applications November 2002, page 47-62

[7] Hua, Chihchiang, Jongrong Lin & Chihming Shen “Implementation of a DSPControlled Photovoltaic System with Peak Power Tracking” IEEE Transactions on Industrial Electronics, Vol. 45, No. 1 February 1998, page 99-107

[8] Dang, Thuy Lam A Digitally-controlled Power Tracker Master’s Thesis,

California Polytechnic State University, Pomona, 1990

[9] Day, Christopher Alan The Design of an Efficient, Elegant, and Cubic Pico-Satellite Electronics System Master ’s Thesis, California Polytechnic State University, San Luis Obispo, 2004

[10] Mohan, Undeland, Robbins Power Electronics – Converters, Applications, and Design 3rd Edition John Wiley & Sons Ltd, 2003

[11] Enslin, John H., Mario S. Wolf, Daniël B. Snyman, & Wernher Swiegers “Integrated Photovoltaic Maximum Power Point Tracking Converter” IEEE Transactions on Industrial Electronics, Vol. 44, No. 6

December 1997, page 769-773

[12] Green, Martin A. Solar Cells; Operating Principles, Technology, and

System Applications Prentice Hall Inc., 1982

[13] Hart, Daniel W. Introduction to Power Electronics Prentice Hall Inc.,

1996

[14] Hohm, D. P. & M. E. Ropp “Comparative Study of Maximum Power Point Tracking Algorithms” Progress in Photovoltaics: Research and Applications November 2002,page 47-62

[15] Castañer, Luis & Santiago Silvestre Modelling Photovoltaic Systems,

Using PSpice John Wiley & Sons Ltd, 2002

[16] Hussain,M. etal. “Final Report of Solar and Wind Energy Resource

Assessment (SWERA) – Bangladesh”, 2007

IJSER © 2013 http://www.ijser.org