Standalone Commercial PV Streetlight System Design Project

This assignment details the design of a standalone commercial PV streetlight system, emphasizing the selection of LED lighting over incandescent options due to their inefficiency. The design prioritizes light output and its distribution, aiming for more illumination on the roadside and less on the opposite side. A 50-watt LED street light is chosen, with reasoning for its suitability for pole height, pole spacing, and road width, alongside its economic viability. The core components of the system—photovoltaic module, charger, and battery—are sized based on energy demand calculations. The process involves determining the energy consumed by the LED lights, calculating the energy supplied by the PV module, and sizing the PV module itself using peak watt calculations. The battery is sized to store sufficient energy for nighttime operation and cloudy days, with considerations for autonomy days, battery loss, depth of discharge, and nominal battery voltage. Finally, the battery charger is sized based on the short circuit current of the PV arrays, ensuring it can handle the current from the PV modules. The assignment includes references to relevant sources.

It is wise to choose LED lighting over incandescent lights in the design of street lighting
systems, as the latter are inefficient and expensive. Light output and its asymmetric distributions
are key factors to consider in the design, in that case street lighting system should give more
output to the road side and less to the opposite side. Power ratings of the street light is chosen
based on height of the pole, distance between the poles and the width of the road [1].
A pole height of 15 feet and above will require a street light with a power rating of between 30-
50 watts. In this design we will consider a 50 watts LED street lights to accommodate fairly long
street pole and fairly spaced poles as this will save on the cost of installation. Furthermore, the
wattage will provide more light to the wide roads. Power ratings of 50 Watts is also
economically viable, as much energy won’t be consumed and is readily available in the market.
The main components of commercial PV street light systems are photo voltaic module, charger,
battery and street light. Photo voltaic module is responsible for the conversion of UV rays into
direct current power. Battery charger controls the current and voltage that flows in from photo
voltaic module thus preventing overflow of current and voltage to the battery, battery will not be
over-charged and will make it last longer. Battery is a storage device, it stores energy from the
PV module, it is where the street lights gets the power supply [2].
The first step to the design of the lighting system is to determine power and energy consumed by
the LED street light. Power consumed by the LED lights was chosen to be 50 watts, with the
power, energy can be calculated.
Power = 50 watts
Energy = power * time
Where time is the number of hours per day the street light will be on,
The street lights will be on for 12 hours per day, thus
Energy demand by the street lights = 50 * 12
= 600 watt-hours
The second step is to determine the energy to be provided by the PV module to meet the demand
of the street light. To find this the energy demand by the street is multiplied by 1.3, this factor
will compensate the energy that will be lost in the system [3].
Energy to be supplied by PV module = 600 * 1.3
= 780 watt-hours
Sizing photovoltaic module
To calculate the sizing of the photovoltaic module, peak watt (Wp) that is expected from the
modules is determined. Peak watt largely depends on location of the site. In this design we will
consider panel generation factor for EU countries which is equivalent to 2.93
Total peak watt (Wp) per day = energy to be supplied by PV modules/ panel generation factor

= 780/2.93
= 266 watt-hours
The next step is to calculate the number of PV modules for the lighting system using total peak
watt
Minimum number of modules = Total watt peak (Wp) / rated output watt-peak of the PV modules
A PV module with rated output watt peak of 110 is chosen
Minimum number of modules = 266 / 110
= 2.4 modules
Actual minimum number of modules is 3
For better operation of the system, 4 modules is used for this design
Battery sizing
The type of battery that serves better with the solar lighting system is the deep cycle battery. The
battery should also be large enough to store required/demanded energy to operate the lighting
system during the night and when its cloudy
Battery size = (total energy demanded by lighting system per day * days autonomy) / (battery
loss * depth of discharge* nominal battery voltage)
Day of autonomy refers to the number of the days the battery can sufficiently supply the lighting
system without receiving power from the PV panels, and 4 days is chosen for this design [4].
Battery loss = 0.85
Depth of discharge = 0.6
Nominal battery voltage = 12 volts
Battery size = (780 * 4)/ (0.85 * 0.6 * 12)
= 510 Ah
The battery should have nominal voltage of 12 volts and a capacity of 600 Ah.
Sizing battery charger.
The charger is rated based on voltage and current capabilities. Battery charger chosen must
match the voltage of PV panel and that of batteries. The charger should also have enough
capacity to withstand current coming from PV arrays. Sizing a charger depends on two factors;
PV modules configuration that is whether they are connected in parallel or in series and the
current coming from the PV arrays [1].
Battery charger size = total short circuit current of the photo voltaic arrays * 1.3

Every module comes with its specification, the data in it are voltage, power, current, open circuit
voltage and short circuit current. The specification will enable us calculate the battery charger
size, for instance a module with a short circuit current of 7.5 A, battery charger for our design
will be
Battery charger size = number of strings * short circuit current of one module* 1.3
= 4 * 7.5 * 1.3 (The modules are connected in series)
= 39 A
Battery charger size should be greater or equal to 40 A

REFERENCES
[1] Led Lights In India, “Buying LED street? Real factors you should consider for best quality”,
n.d. Accessed on: October 6, 2019 [online]. Available:
https://www.ledlightsinindia.com/information/led-street-light-quality-factor-buying-guide
[2] Engoplanet, “How to design and calculate solar street lighting system”, n.d. Accessed on:
October 6, 2019 [online]. Available: https://www.engoplanet.com/single-post/2017/08/21/How-to-
design-and-calculate-Solar-Street-Light-system
[3] J.Lagorse, P.Damien, and M.Abdellatif. "Sizing optimization of a stand-alone street lighting
system powered by a hybrid system using fuel cell, PV and battery." Renewable Energy, pp.683-
691, 2015
[4] HA,Mohammed. "Design and implementation of a photovoltaic system used for street
lights." 2016 2nd International Conference on Control Science and Systems Engineering
(ICCSSE). IEEE, 2016.