Prospect of Mini-Hydel Power Generation in Drainage Systems of Bangladesh

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2021 2nd International Conference on Robotics,Electrical and Signal Processing Techniques (ICREST)

Prospect of Mini-Hydel Power Generation in Drainage Systems of Bangladesh

M M Naushad Ali

Department of Electrical and

Electronic Engineering Bangladesh University

Dhaka, Bangladesh [email protected]

Mehedi Hasan

Department of Electrical and Computer Engineering

North South University

Dhaka, Bangladesh mehedi.hasanO 1 @northsouth. edu

Ahmed J. Nahian

Department of Electrical and

Electronic Engineering Bangladesh University

Dhaka, Bangladesh aj [email protected] Nusrat Chowdhury

Department o f Electrical and

Electronic Engineering Daffodil International University

Abdul Hasib Siddique

Department of Electrical and

Electronic Engineering University o f Science and Technology

Chattogram, Bangladesh ahnion. ahs@gmail. com Chowdhury Akram Hossain

Department of Electrical and

Electronic Engineering American International university

Abstract— In today’s world, large scale hydroelectric power plants have an impact in the energy demography; although, the huge potential of pico, micro and mini-hydropower plants are still very much untapped. In this work, a techno-economic viability, of mini hydro power potential from drainage water, has been investigated in four areas of Dhaka city. Considering the head of water fall and the flow rate in the drainage system, technical, economic and environmental parameters are studied.

100 kW to 500 kW power can be generated from the proposed system with economic benefit o f around BDT 3.9M to 28M per year, and emissions reduction o f around 500 to 3000 ton- CO²/year.

Keywords— renewable energy, mini-hydro, drainage, Bangladesh

I. In t r o d u c t i o n

B angladesh b ein g a developing country, w ith a n ever

grow ing population, needs continuous electricity supply, w here 56% is b ased o n natural gas [1]. A ccording to Lom borg, to m eet the dem and fo r electricity, the source o f p roduction should shift fro m the current natural gas to im ported coal; this w ould m ake electricity m uch cheaper and m ore available and w ould increase the econom y by B D T 4.2 trillion [2]. B u t this w ill lead to increased C O2 em issions. B angladesh has also b ee n identified as the 6 th m ost vulnerable to clim ate change, w ith a G lobal C lim ate R isk Index (CRI) score o f 22.67 [3].

O w ing to lim ited natural resources, challenges and costs o f transm ission expansion, and clim ate change issue, the country m ust shift to m ore sustainable and distributed m eans o f electricity generation. International policies, such as U N Sustainable D evelopm ent G oals [U N SD G 7], are prom oting increased use o f renew able energy resources. Some national instrum ents, such as N ational E nergy Policy and B angladesh Clim ate Change Strategy and A ction P la n are also m otivations to shift to cleaner form s o f energy p roduction [4-5]. The country already has 4.5 m illion Solar H om e System s (SH S) installed in the off-grid rural areas o f B angladesh and about

13 m illion beneficiaries are getting solar electricity [6-7].

W ith these m otivations, a hybrid m odel o f grid-hydro p o w er station is p roposed here. The generation plan t m ay be m icro o r m ini hydro plant, according to distinct scenarios considered: different heads and flow rates. H ydropow er is p roved to be n on-polluting and environm entally friendly,

w h ich uses renew able w ater source [8]. Sm all hydro projects (SH P) such as these, despite sufficient potential, has seen slow grow th in regions like B an g lad esh b ecause of: rem ote potential locations and difficult terrains, less com m ercial v iability due to the size and rem ote access, and little policy actions influencing th eir pen etratio n in the m arket [9].

H ydel p o w er plants classified u sin g am ount o f po w er g eneration such as pico-hydro (<100 kW ), m icro-hydro (up to 100 kW ), m ini-hydro (101 kW -2000 kW ), sm all-hydro (2001 kW -25000 kW ) and large hydro (>25000 kW ) [10]. A dhau et al. explored technical and financial prospect o f m ini-hydro p o w er generation o n existing irrigation projects in Indian sites [10]. A li e t al. p roposed a m ini hydel po w er generation design fo r a drainage system in Sindh, w here field-based data param eters w ere used to analyse technical feasibility [11].

R a za n et al. did a com prehensive study o n m icro-hydropow er plan t and its potential in B angladesh, w here they identified potential sites and outlined the param eters and calculations n eeded to identify the sites [12]. Jui et al. did a feasibility study o f m ini hydroelectric p o w er plant in Sitakunda w here they estim ated the p o w er output b ased o n the flo w rate and head o f a w aterfall [13].

In this research, the w ater fro m drainage system , that is pum p ed to the natural w ater stream s, is utilized fo r pow er g eneration u sin g a hydel p o w er system . F easibility studies are done in term s o f technical, econom ic and environm ental perspectives.

II. Pr o p o s e d Me t h o d

A. Proposed System

T he system pro p o sed is a grid-connected m ini-hydro p o w er p lan t th at utilizes the flow rate o f the drainage system to supply the load. Fig. 1 show s the schem atic diagram o f the system , w here the A C load is supplied fro m b o th the hydro p lan t and A C grid. The turbine is run b y the drainage water, after b ein g treated and solid w aste rem oved. The battery stores the energy pro d u ced fro m the turbine and supplies to th e load th ro u g h the inverter. W hen the supply is short fro m the turbine, the load is m et u sin g the grid electricity.

Selection o f a turbine is a n im portant task to achieve desired output. G eneration o f electricity depends o n the turbine th at is coupled w ith the generator. A m ongst a w ide

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Fig. 1. Schematic o f proposed system

range of turbines, a specific turbine is chosen based on the head and flow rate. In the proposed system, the head varies from 1 to 5 m, and the flow rate varies from 15 to 30 m3/s.

Considering these, Kaplan turbine has been the appropriate choice as it is suitable for low head with high flow rate [14].

In the proposed system, due to high efficiency and lighter weight, a permanent magnet DC generator is used over wound stator generators to convert mechanical energy to electrical energy. These types of generators have better efficiency since there are no field winding and field coil losses and also minimize losses in the rotor by 20 to 30 percent.

A charge controller or battery regulator is mainly used for protecting batteries from drawing overcurrent which results in increased battery performance and lifespan. It also maintains controlled discharge of batteries and diverts the power when the batteries are fully charged.

B. Parameters fo r system evaluation

For system evaluation, technical, economic, and environmental parameters are analyzed.

The generated power from the mini-hydropower system is given by,

LEC = Ci+Co m [ B DT / k W h ]

(

3

)

L XE

where,

C

j

= initial investment cost [BDT]

C

o m

= operation and maintenance (O&M) cost [BDT]

L = lifetime [years]

The economic benefit (B) is calculated considering the utility electricity cost (BDT/kWh) of the considered location for a certain type of load,

B = E X (c

n

- LEC) [BDT/year] (4) where,

cn

= utility electricity cost at location n [BDT/kWh]

The emissions reduction for using renewable energy compared to utility electricity is calculated using the equation below,

wQHgg

1000 [kw]

where,

w = specific weight of effluent [kg/m3]

E X

GEF

(!) E R =

[ton — C0

2

/year] (5)

1000 2

where,

GEF

= grid emissions factor [ton-CO

2

/MWh]

Q = rate of flow of water [m

3

/s]

H = height of fall or head [m]

n = efficiency of generation g = gravitational acceleration [m/s2]

The energy produced by the system per year is calculated by,

E = P x

8760 [kW h/year] (2)

C. Case Study

A case study is done to check the feasibility of the proposed system. Four locations in Dhaka are chosen to analyse the proposed system. TABLE I shows the locations and the average flowrates throughout the year in the drainage system. Using these flow rates as reference, 5 m3/s is added for assuming highest flow rate, and 5 m3/s is subtracted for assuming lowest flow rate and used in the analysis of power generation, energy production, LEC, economic benefit and emissions reduction. For each flow rate, heads of 1 m, 3 m and 5 m are used.

The levelized electricity cost (LEC) of the system is calculated using the equation below,

TABLE I. DRAINAGE SYSTEM FLOW RATE IN DIFFERENT LOCATIONS OF DHAKA [15]

Pum ping Station Flow R ate [m3/s] (2018

2019)

Kalyanpur 20

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Dholaikhal 22

Rampura 25

Kamalapur 15

T A B L E II show s the assum ptions tak en for the calculation o f param eters for system evaluation. The load for the system is considered to be the streetlights across the locations. The utility electricity cost o f D haka for streetlights is used to calculate the econom ic b enefit in BD T/year. T he grid em ission factor (G EF) is utilised to calculate the em issions reduction using the proposed system com pared to using grid electricity.

TABLE II. As s u mpt io n so fe c o n o mica n de n v ir o n me n t a l CALCULATIONS

P aram eter Assumption Reference

Efficiency (rj) 50%

Gravitational Acceleration (g)

[m/s2]

9.81 Water Density (w)

[kg/m3] 1000

Grid Cost

[BDT/kWh] 7.17 [16]

GEF [ton-

C02/MWh] 0.67 [17]

Lifetime [years] 20 [18]

Initial Investment

Cost [BDT/kW] 99,000 [18]

O&M Cost

[BDT/kW/year] 4,500 [18]

III. Re s u l t s a n d Di s c u s s i o n

The results w ere analyzed and discussed according to technical, econom ic and environm ental perspectives to determ ine th e feasibility and prospect o f the proposed hydel po w er plant.

A. Technical Analysis

The pow er generated by the proposed system , for different flow rates and head, a t different locations are illustrated in Fig.

2. The results show that th e generated po w er increases linearly w ith th e increase in head and flo w rates. F o r K alyanpur, the generated pow er is 98.1 kW and 490.5 kW for a head o f 1 m and 5 m respectively, at the average flow rate o f 20 m 3/s. F or D holaikhal, th e generated pow er is 107.9 kW and 539.6 kW for a head o f 1 m and 5 m respectively, at the average flow rate o f 22 m 3/s. For R am pura, the generated pow er is 122.6 kW and 613.1 kW for a head o f 1 m and 5 m respectively, at the average flow rate o f 25 m 3/s. F o r K am alapur, th e generated

pow er is 73.6 kW and 367.9 kW for a head o f 1 m and 5 m respectively, at the average flow rate o f 15 m 3/s.

The annual energy production, for each location is shown in T A B L E III.

B. Economic Analysis

The LE C o f the proposed hydel pow er plants stands at 1.079 B D T /kW h, w hereas the grid electricity cost for streetlights is at 7.17 B D T /kW h [14].

T A B L E III shows th e econom ic b enefit per y ear for each location w ith variable flow rates and heads.

TABLE III. En e r g yOu t pu t a n dEc o n o micBe n e f it f o r4 l o c a t io n s Location Flow R ate

(Q) [m3/s]

H ead (H) [m]

E nergy (E) [kW h/year]

Economic Benefit (B) [BDT/year]

Kalyanpur

15

1 644517 3,925,903

3 1933551 11,777,709

5 3222585 19,629,516

20

1 859356 5,234,538

3 2578068 15,703,613

5 4296780 26,172,688

25

1 1074195 6,543,172

3 3222585 19,629,516

5 5370975 32,715,860

Dholaikhal

17

1 730453 4,449,357

3 2191358 13,348,071

5 3652263 22,246,784

22

1 945292 5,757,991

3 2835875 17,273,974

5 4726458 28,789,956

27

1 1160131 7,066,626

3 3480392 21,199,877

5 5800653 35,333,128

Rampura

20

1 859356 5,234,538

3 2578068 15,703,613

5 4296780 26,172,688

25

1 1074195 6,543,172

3 3222585 19,629,516

5 5370975 32,715,860

30

1 1289034 7,851,806

3 3867102 23,555,419

5 6445170 39,259,031

Kamalapur

10

1 429678 2,617,269

3 1289034 7,851,806

5 2148390 13,086,344

15

1 644517 3,925,903

3 1933551 11,777,709

5 3222585 19,629,516

20 1 859356 5,234,538

3 2578068 15,703,613

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Fig. 3. Emissions Reduction (ER) with change in head and flow rate at different locations

| I 5 I 4296780 | 26,172,688 |

C. Environmental Analysis

B ased on the energy produced by the system , the reduction in C O2 em issions is show n in Fig. 3. E m issions reduction is h igher if the flow rate and head are higher, as the energy generation is higher. T his reduction due to the utilization o f clean energy source com pared to using the grid for sam e energy usage.

IV. Co n c l u s i o n

The p aper proposes a tech-econom ic analysis o f m ini

hydroelectric p ow er plant utilizing the flow rate o f drainage w ater. A case study, in four locations o f D haka, w as done to analyse the proposed system and feasibility of m ini-hydel plants.

W ith flow rates ranging from 10 m 3/s to 30 m 3/s and head range from 1 m to 5 m , we can generate an average o f 100 kW to 500 kW po w er from the proposed system th at can be supplied to streetlights in the corresponding areas providing econom ic benefit o f around B D T 3.9M to 2 8 M p er year. In addition to this, the system also has environm ental benefit by reducing around 500 to 3000 ton-C O2/year. C onsidering the benefits o f bo th financial and environm ental aspects, feasibility to build m ini hydro pow er p lan t using drainage w ater system in four areas o f D haka is reasonable.

In future, an analysis w ith w ater treatm ent p lan t for the drainage w ater could be considered w hich w ill influence energy consum ption, econom ic ben efit and em issions reduction. A n experim ental setup could be done to verify the theoretical assum ptions and results. C ost-benefit analysis o f the setup could b e used to calculate retu rn o f investm ent and p ayback period before im plem enting high scale projects.

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