Getachew Bekele (PhD) Addis Ababa Institute of Technology

Optimal Design of A Standalone

Photovoltaic Power Supply System for Air

Conditioning Application at Samara

University in Ethiopia as an Alternative to

Diesel Generator

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Locations

11.45 °N, 41E

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Background

• Annual temperature: 27C - over 50C

• Self-contained diesel station supplies electricity; the utility

grid is not yet within reach

• Animosity of diesel fuel and environment

• Increasing fuel price

• Requires skilled personnel for O&M

On the other side:

• Falling price of PV module

• Improvement of its PV efficiency

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Solar energy potential

• Annual average solar radiation for Ethiopia is 5.26 kWh/m2

• Afar region reaches up to 6.10 kWh/m2

• Data source:

– NASA Surface meteorology recorded for more than 10 years

– Also from Solar Energy: RETScreen Data

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Thermal load

• The load is air conditioning unit

• The estimation is done based on a popular and widely used thumb

rule for load estimation developed by company based designers

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Electrical load ... (Cont’d)

• The electrical load of the PV is selected to be an evaporative

air conditioning (EAC) unit through comparison against

refrigerated air conditioning (RAC)

Cooling load and electric consumption Average initial expense

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Standalone PV System

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Components

• Energy consumption of the units is calculated as 2,140 kWh/day

(kW × hours /day)

• 15% noise level has been added to the calculated load

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Input to HOMER

PV Diesel Generator Battery (Surrette

6CS25P)

Converter

Size (kW) 1 1 1,156Ah 1

Capital ($) 3,480 288 644 700

Replacement cost ($) 3,480 210 483 700

O&M cost ($/yr) 0 0.025($/hr) 20 0

Sizes considered

(kW)

0, 100, 520,

530, 540, 550,

600

0, 200, 292, 380 0, 100, 150, 200,

250, 300, 350,

400

Quantities considered 0, 80, 140, 150,

160, 180

Life time 25 years 60,000hrs 9,645 kWh 15 years

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Result &discussion

PV

(KW)

Gen

(KW) Battery

Inverter

(KW)

Capital cost

($) NTC ($)

COE

($/KWh)

Renewable

Fraction

Diesel

($/yr)

Gen

hours

(hr/yr)

540 - 1,200 250 2,827,000 3,666,051 0.323 1 - -

520 - 1,280 250 2,808,920 3,698,888 0.326 1 - -

550 380 1,200 300 3,006,240 4,200,306 0.345 0.94 24,538 393

600 380 1,280 300 3,231,760 4,283,414 0.352 0.97 11,695 189

600 380 1,440 300 3,334,800 4,411,491 0.363 0.98 6,592 108

100 380 - 100 527,440 5,849,272 0.481 - 356,649 5,227

100 380 - 150 562,440 5,899,329 0.485 - 356,649 5,227

- 380 640 100 591,600 6,513,526 0.536 - 369,070 5,447

- 380 640 150 626,600 6,562,532 0.54 - 369,013 5,445

520 380 - 200 2,059,040 6,907,650 0.568 0.1 321,626 4,844

520 380 - 250 2,094,040 6,933,183 0.57 0.11 320,035 4,817

- 380 - - 109,440 6,968,115 0.573 - 460,330 6,830

Overall optimization results

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Catagorized optimization results

Result &discussion ... (Cont’d)

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Result &discussion ... (Cont’d)

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Cost summary

Result &discussion ... (Cont’d)

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Result &discussion ... (Cont’d)

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Conclusions

• The study indicated that with 5.58–6.66 kWh/m2 potential, the

region is a prospective candidate for deployment of PV systems.

• In this work evaporative air conditioning system is proven to be a

more efficient load for the PV system

• The cost of energy (COE) is obtained is 0.323 US$/kWh for a

diesel fuel price of 0.8$/l,

• The maximum capacity shortage is just 10%.

• Hence, a stand alone PV system with battery storage (100%

renewable resource) is the preferable solution to the diesel

• The finding here is applicable to many similar

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