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System Design Calculation

This document provides guidelines for sizing the key components of a solar PV power system, including: 1) Determining the consumer energy demand based on electrical loads and running times. 2) Sizing the solar panel to meet the consumer energy demand based on the performance ratio and peak sun hours. 3) Calculating the battery capacity needed based on the consumer energy demand, desired days of autonomy, and depth of discharge. 4) Sizing the charge controller based on the maximum power point current from the solar panels and panel voltage. 5) Selecting appropriate cable sizes based on voltage drop, length, current, and material.

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Tomilayo Samuel Adeyemi
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444 views16 pages

System Design Calculation

This document provides guidelines for sizing the key components of a solar PV power system, including: 1) Determining the consumer energy demand based on electrical loads and running times. 2) Sizing the solar panel to meet the consumer energy demand based on the performance ratio and peak sun hours. 3) Calculating the battery capacity needed based on the consumer energy demand, desired days of autonomy, and depth of discharge. 4) Sizing the charge controller based on the maximum power point current from the solar panels and panel voltage. 5) Selecting appropriate cable sizes based on voltage drop, length, current, and material.

Uploaded by

Tomilayo Samuel Adeyemi
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PPTX, PDF, TXT or read online on Scribd
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NATIONAL POWER TRAINING INSTITUTE OF NIGERIA

SOLAR POWER SYSTEM

(PV SYSTEM SIZING)


PV SYSTEM SIZING REQUIREMENT

1. Site survey (structures, electrical consumers, meteorological


data)
2. Determine consumer energy demand
3. System voltage (12V, 24V, 48V)
4. Determine PV array power
5. Determine battery capacity and system voltage
6. Determine charger controller voltage and current
7. Determine inverter power
8. Determine cable size
SYSTEM VOLTAGE
 The system voltage depends on:

1. Electrical devices loads (ac or dc)

2. Energy demand (approx. up to 1KVAh 12V, up to 2.5KVAh


24V)

3. Cable lengths which includes:

a. PV – battery

b. Battery – electrical consumer (dc devices & inverter)


CONSUMER ENERGY DEMAND

 The consumer energy demand depends on:

1. Real power rating of devices (apparent power in case


of ac)

2. Running time of devices

3. Efficiency of inverter (app. 85% - 95%)

4. Inverter standby consumption (app. 1% of rated


power)

5. Inverter standby running time


CONSUMER ENERGY DEMAND
CALCULATION

 Inverter output energy (VAh) = Device wattage x hrs. of usage


cosθ

 Inverter input energy (VAh) = Inverter output energy


Inverter efficiency

 Inverter standby consumption (VAh) = Standby wattage x runtime

 Therefore, Consumer Energy Demand is given as:

Inverter input Inverter standby


CED = + consumption
energy (VAh)
(VAh)
EXAMPLE
 A family load audit runs as follows: 6CFL bulb(20W), 1TV set
(50W), 1DSTV decoder (12W), 3fans (100W) and 1 fridge
(222KWh/annum) running for 5hrs per day. What is the total daily
energy demand of the family?
LOAD CALCULATION/ SIZING
Energy
Device QTY Watts Cos θ App. power (VA) Hrs.
(VAh)

Television 1 50 0.6 83 5 415

CFL bulbs 6 40 0.6 400 5 2000

DSTV 1 12 0.6 20 5 100

Fan 3 100 0.6 500 5 2500

Fridge 1 25 1 25 5 125

Miscellaneous 1 100 1 100 5 500

TOTAL 1128 5640


Consumer Energy Demand =
amount of energy discharge from battery

Device
energy
Solar energy demand
generation

Battery charge Consumer energy demand


C (Ah) (battery discharge)
INVERTER SIZING

Apparent power
(VA) of devices
(ac or dc)
PERFORMANCE RATIO (PR)= 65%
PR depends on:
1. Operating voltage = battery
Out of MPP voltage is app. 25% less than
operation losses
MPP
= 25%
2. Losses due to dust
Performance

3. Battery charging losses


4. Charge controller losses
5. Wiring losses

Electrical
losses = 3% Charging
Ratio = 65%
losses = 7%
PANEL SIZING
 Solar energy demand from the panel is given as:

Solar Energy demand = Consumer energy demand


Performance Ratio = 65%

 Thus, Solar Power (Wp) is given as:

Solar Power (Wp) = Solar energy demand


Peak Sun Hour (PSH) – worst month
8,676Wh
5,640Wh
Solar energy demand
Consumer energy demand

Losses = 35%
8676Wh x 65% = 5640

5640/PR=65% = 8,676Wh
BATTERY SIZING

 Battery capacity of a Solar system depends on:

1. Daily consumer energy demand or battery discharge (Ah)

2. Desired lifespan in cycles or Depth of Discharge (DoD)

3. Days of Autonomy

 Thus, Battery capacity (C) is given as:

C= Consumer energy demand x Days of autonomy


DoD x System voltage
Battery capacity (C) can also be given as:

C = battery discharge x Days of autonomy


DoD

C (Ah) = +

Consumer energy demand


(battery discharge)
CHARGE CONTROLLER SIZING

 Charge controller rating depends on:


1. Current at MPP from the PV modules
2. Panel voltage
3. Plus 20% oversize factor
CABLE SIZING
 Cable rating depends on:
1. Desired max voltage drop
2. Length
3. Material
4. Current
 Thus, Cable rating is given as:

ΔV = 2L x I
ρA
 The max allowable voltage drop from PV to battery and from
battery to loads is 3%

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