Off-grid Rural Area Electrification by

Solar-Diesel Hybrid Mini-grid in

Bangladesh : Design Considerations

Shahriar Ahmed Chowdhury Email: shahriar.ac@gmail.com

Director, Centre for Energy Research Assistant Professor, Department of Electrical and Electronic Engineering, UIU

Functional Structure of IDCOL

Solar-Diesel Hybrid Minigrid

April 12, 2014 2

April 12, 2014 3

Financial Scheme of IDCOL Minigrid

Project

Grant Loan Equity Project Donors:

KfW, WB, ADB and JICA

Loan Scheme:

Interest rate: 6%

Tenure: 10 years

Principal grace: 2 years

Payment frequency: 3 months

Payment type: Annuity

Mini-Grid Design Steps

1 • Site Survey for Feasibility Study

2 • Demand Assessment (Load duration curve)

3 • Technical Design

4 • Financial Analysis

5 • Preparing Bankable Document

6 • Installation Supervision and Commissioning

April 12, 2014 4

Typical Rural (Household and Shops) Load

Duration Curve

0 5

10 15 20 25 30 35 40 45 50 55 60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kW

h L

oad

Time of the day

Winter, kWh Summer, kWh

For 800 house holds and a village market having 200 shops

April 12, 2014 5

April 12, 2014 6

Typical Rural Load Duration Curve With Productive

Day Loads

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

kW

h L

oa

d

Time of the Day (24 hours)

For 500 households, a village market having 150 shops and

industrial loads (Workshop, Saw mills and ice making industry)

Design Consideration

Solar-diesel Hybrid

Mini-grid

RE fraction

>80% or above

Payback period 10

years

Financial

Model

Reduced CoE by

increasing productive day loads

Battery Manageme

nt

Voltage drop at the end of distribution

feeders <5% of rated

Project life 20 years

April 12, 2014 7

Energy Mix for Rural mini-grid

Energy share curve of a 200kWp Solar-Diesel Hybrid Mini-

grid

Renewable Fraction > 90% April 12, 2014 8

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

20,000

Mo

nth

ly L

oad

(kW

h)

Electricity Generation Mix

Supply from diesel generator Datenreihen2

Project cost breakup Generation Equipment

(Solar Panel+ Generator)

19.7%

Electronics (Controller & Inverter)

17.3%

Storage System (Battery and Protection)

20.5%

Land and Infrastructure (Land+Land

Dev.+Building) 14.4%

Distribution Systems 15.9%

Other 4.3%

Technical Assistace

3.2%

Contigency 4.8%

April 12, 2014 9

Cost Reduction Potential

Increase of daytime load (does not require battery storage) Solar irrigation

Cottage industries (Sewing or weaving machine etc.)

Husking mills

Sawmills

Lathe machine

Welding machines

Grinding machines (spice)

Photocopier machine

Computer training centres

Poultry firms

Cold storages

Ice making industry (for fish preservation in island areas)

Offices /Schools/Madrasas etc. April 12, 2014 10

Storage system Most difficult part of designing an off grid solar system for rural

electrification is the storage system managements.

Bottle necks:

1. Limitation of charging and discharging currents limits the

design

flexibility.

2. Limitation of DoD of battery operation increases the

size of battery bank

3. Higher ambient temperature reduces the designed battery

life

Advantages of adding a diesel generator is included in mini-grid to

1. Increase the reliability of power

2. Reduce the storage requirement

3. Avoid autonomy requirements

4. Reduce project cost (reduced battery size reduces the

project cost)

April 12, 2014 11

Single line diagram of PV –diesel minigrid

April 12, 2014 12

Consumer type (Household) and approximate

monthly bill

Package type Load Quantity Power

/unit Approximate monthly

bill in USD

Package-1

(Small Households 550)

LED light 4 7 5.75

Ceiling Fan 2 25

Package-2

(Medium Households 205)

LED light 5 7

8.75 Ceiling Fan 2 25

TV 1 50

DVD 1 20

Package-3

(Well off households 85)

LED light 5 7

18.85

Ceiling fan 3 25

TV 1 50

Refrigerator* 1 100

CD/ DVD 1 20

Package-4 shops

LED light 3 7 2.6

Ceiling Fan 1 25

Package-5 shops

LED light 3 7

12.75 Ceiling Fan 2 25

TV 1 50

Refrigerator* 1 100

Package-6 School LED light 20 7

23.07 Ceiling Fan 10 25

April 12, 2014 13

Considering IDCOL model tariff varies from USD 0.35 – 0.45 depending

upon the size and load pattern of the minigrids

April 12, 2014 14