Solar-powered LED-based lighting facilities: An overview on recent technologies and embedded IoT devices to obtain wireless control, energy savings and quick maintenance

Abstract

Aim of this paper is to illustrate and describe the trend of last technological innovations and new IoT-based devices employed in solar-powered LED-based lighting systems, in order to obtain energy savings, low mainteinance costs and to offer additional services to the users or community. Technological developments, in the last years, have allowed the use of LEDs technology in many general illumination applications, from houses to commercial or outdoor spaces. LED lighting is projected to reduce related energy consumption of 15% in 2020 up to 40% in 2030; in this contest, solar-powered LED lighting facilities offer a significant contribution to obtain energy savings, together with substantial environmental and health benefits. Last innovations in nanotechnology and quantum physics have the potential to strongly increase the electrical power obtained from solar panels for feeding any portable device. Furthermore, the spread of Internet of Things (IoT) and the huge use of smartphones and related apps allow wirelessly to control and drive the LED-based lighting systems, that also can be provided with integrated sensors thus realizing new functionalities, an improved management of energy and new services for smart cities. Finally, systems made up of connected lighting devices could become data collection platforms that, making use of renewable energies, enable even greater energy savings referred to lighting and in general electrical facilities present in smart buildings or cities.

Full text

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SOLAR-POWERED LED-BASED LIGHTING FACILITIES: AN OVERVIEW
ON RECENT TECHNOLOGIES AND EMBEDDED IoT DEVICES TO
OBTAIN WIRELESS CONTROL, ENERGY SAVINGS AND QUICK
MAINTENANCE
Patrizio Primiceri and Paolo Visconti
Department of Innovation Engineering, University of Salento, Street for Monteroni, Lecce, Italy
E-Mail: patrizio.primiceri@unisalento.it
ABSTRACT
Aim of this paper is to illustrate and describe the trend of last technological innovations and new IoT-based
devices employed in solar-powered LED-based lighting systems, in order to obtain energy savings, low mainteinance costs
and to offer additional services to the users or community. Technological developments, in the last years, have allowed the
use of LEDs technology in many general illumination applications, from houses to commercial or outdoor spaces. LED
lighting is projected to reduce related energy consumption of 15% in 2020 up to 40% in 2030; in this contest, solar-
powered LED lighting facilities offer a significant contribution to obtain energy savings, together with substantial
environmental and health benefits. Last innovations in nanotechnology and quantum physics have the potential to strongly
increase the electrical power obtained from solar panels for feeding any portable device. Furthermore, the spread of
Internet of Things (IoT) and the huge use of smartphones and related apps allow wirelessly to control and drive the LED-
based lighting systems, that also can be provided with integrated sensors thus realizing new functionalities, an improved
management of energy and new services for smart cities. Finally, systems made up of connected lighting devices could
become data collection platforms that, making use of renewable energies, enable even greater energy savings referred to
lighting and in general electrical facilities present in smart buildings or cities.
Keywords: renewable energies, LED lighting, wireless control, data monitoring, IoT-based devices, energy savings, sensors.
INTRODUCTION
Light Emitting Diode (LED) plays a fundamental
role for energy saving and environmental protection in
lighting industry. LED-based lights are up to 80% more
efficient than traditional lighting sources such as
fluorescence and incandescent lamps. Unlike of these
which create light with filaments and gases encased in a
glass bulb, the LEDs or organic light-emitting diodes
(OLEDs), commonly referred to as Solid-State Lighting
(SSL) devices, consist of semiconductor or polymeric
materials that convert electricity into light. LEDs have
been around for 50 years but until the early 2000s were
used only in electronic devices as indicator lamps (Vitta et
al., 2012). Technological developments in the last two
decades have allowed LEDs to be used first in signal
devices, like traffic lights and exit signs, then in some
limited illumination applications, such as flashlights, and
now for many general illumination applications, from
houses to commercial spaces up to outdoor lighting
(Visconti et al., 2011, 2012), (Costantini et al., 2011).
Solid-state lighting is used in a variety of lighting
applications because it offers many benefits such as:
 long life: the LEDs can provide 50000 hours or more
of life, which can reduce maintenance costs (in
comparison, an incandescent light bulb lasts
approximately 1000 hours).
 Energy savings: white LED-based lighting systems
provide three or more times the luminous efficacy
(lumens/watt) of incandescent lamps. Colored LEDs
are especially advantageous for colored lighting
applications because optical filters are not needed.
 Emitted light with better quality: LEDs have
minimum ultraviolet and infrared radiation and its
light can be tuned to any color appearance.
 Intrinsically safe: LED-based systems are fed at low
voltage (few tens of Volt) and generally are cool to
the touch (compared to traditional lamps).
 Smaller, flexible light fixtures: the small size of
LEDs makes them useful for lighting tight spaces.
OLEDs are flat and flexible, allowing for unique
applications.
 Durable: LEDs have no filament to break and can
withstand vibrations.
SSL technology is demonstrating improved
efficacy over conventional lighting sources and low prices
that enable a payback within reasonable time periods. In
addition to improved source efficacy, SSL devices can be
more effective in delivering light when and where it is
needed, representing an additional factor of energy saving.
As shown in Figure-1 which shows the lighting
energy consumption forecast, LED lighting is projected to
reduce energy consumption by 15% in 2020 and 40% in
2030, which, in absolute terms, is 261 teraWattHours or
3.0 quads saved in 2030 (DOE SSL Program, 2014).

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Figure-1. Lighting energy consumption forecast as
predicted by the lighting market model.
As SSL technology has developed, it has become
clear that the impacts of SSL will go far beyond energy
savings alone. SSL-based facilities can bring to profound
beneficial impacts on the environment, horticulture,
livestock production, transportation safety, human health,
and productivity. All of these benefits can be realized
while saving significant amounts of energy compared to
conventional lighting technologies. Furthermore, LED
lighting manufacturers can choose to trade efficacy for
cost, life-time, color quality, light distribution and other
technical features. OLED technology is still in its infancy
but it promises high efficacy and low cost, as well as new
options for form factor and light distribution.
In addition, light control systems provide tangible
benefits by improving lighting energy efficiency, saving
energy costs, by respecting local rules relative to ignition
timing and percentages (both mandatory requirements and
best practices), so allowing to get numerous rebates and
government incentives or financing.
ADVANCED LED/OLED-BASED LIGHTING
SYSTEMS FOR OBTAINING ENERGY SAVINGS
The full efficiency of a lighting point is affected
by light utilization, which represents how well the light
generated from the luminaire reaches the target area and
provides suitable illumination. For example, thanks to the
small size of LEDs, an improved optical control and
directionality can be obtained; conversely, the large size of
OLEDs emitting surface in conjunction with low
brightness and low glare can enable their use very close to
the task area. For maximizing light utilization for both
LED and OLED sources, it is required a move beyond the
obsolete form factors such as those of the light bulb and
recessed luminaire, toward form factors that maximize
application efficiency as well as optical, electrical, and
thermal efficiencies. New LED-based facilities for outdoor
areas have demonstrated the ability to provide suitable
illuminance levels using a significantly lower total emitted
light respect to conventional lighting points that the new
LED devices have replaced. This is accomplished through
improved light distribution that reduces over-lighting in
the target area, improves illuminance uniformity and
produces less wasted light falling outside the target area.
Figure-2 shows a specific example of improved
light utilization of LED-based outdoor lighting facilities.
A parking lot lighting is realized using Cree LEDs in each
light point, getting 66% reduction of energy consumption
compared with High Intensity Discharge (HID) lamps due
to improved efficiency and reduced total light generation.
In addition, a significantly larger area of the parking lot is
illuminated much better, particularly advantageous for
driver and pedestrian safety (Edmond, Cree Inc., 2015).
Figure-2. Improved light utilization of LED-based
outdoor lighting facilities compared to HID light sources.
Furthermore, given the small size of LEDs, they
can be combined with specially designed lenses to
improve light utilization. Instead of a traditional spherical
shape, specific lenses have complex, multi-curved surfaces
without any prescribed symmetry. They precisely control
light to achieve a desired energy distribution in the
illuminated area. Each light ray emitted by LEDs mounted
on a flat installation board is directed by corresponding
lens to an appointed region as shown in Figure-3.
Figure-3. Properly designed lenses for improving light
utilization of LED-based outdoor lighting systems.
Effective light utilization is very important also
for indoor application, where OLEDs and low brightness

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planar LED solutions can be employed; the low brightness
and diffuse nature of these sources enables them to be
used very close to the task area without generating
excessive glare, enabling adequate illumination using less
light, or conversely, more illumination without
unacceptable glare.
Figure-4 shows two examples of SSL desk lamps
sold by Workrite Ergonomics company, one LED (Figure
4a) and the other one OLED (Figure 4b). Both lamps
deliver nearly identical brightness (106 and 108
footcandles respectively) at the center of the incident task
area; the OLED desk lamp delivers its 442 lumens over a
larger area, whereas the LED’s 306 lumens are much more
concentrated as shown in Figure-4a.
Figure-4. Two examples of LED (a) and OLED (b) desk
lamps that deliver their lumens over different areas.
Another aspect of light utilization is the use of
smart electronic controls to minimize power consumption
of the light source without affecting the lighting
application. LED and OLED sources are inherently
controllable (i.e., brightness dimmable and on/off turning),
which makes them compatible with the full range of
lighting controls.
Acuity Brands, one of the world's leading
providers of innovative lighting systems, has announced
the development of Duet SSL™ Technology, blending the
use of OLED and LED light sources in the same
luminaire, optimizing both to produce refined photometric
performances, improved lighting quality and cost
effectiveness. As shown in Figure-5, downward-facing
OLEDs are incident on the task surface, while LEDs face
upward and provide general illumination that can reflect
off from the ceiling to light the space. This combination
utilizes the soft diffuse glow of OLEDs where the light
interacts with the user whereas the LEDs provide cost-
effective supplementary lumens to fully light the space.
Figure-5. Duet SSL
TM
technology applied to new smart
luminaire with OLEDs for producing downward
illumination to light the task area and on the right, LED
devices on top to produce light that fills the room.
These examples provide just a perspective of how
SSL technology can improve lighting performances and
the value of a lighting facility. As product developers,
architects and lighting designers fully embrace the
possibilities of SSL technologies, new form factors,
lighting layouts and building integration approaches will
emerge. In this way, SSL technology will ensure not only
source efficiency but also optimized energy utilization,
building efficiency and better lighting performances,
finally ensuring energy savings and quick maintenance.
The electrical connection of light points can also
be improved through the use of direct current (DC) grids
in the building, removing the requirement for alternating
current (AC) to DC conversion at each LED lamp. This
can also facilitate direct connection to renewable energy
sources, such as solar panels or wind turbines, and to their
battery systems without requiring DC to AC conversion
and then conversion back to DC for the LED operation.
SOLAR-POWERED LED LIGHTING SYSTEMS
EMPLOYED IN MANY DIFFERENT AREAS
The reduction of the electrical consumption of
lighting systems, through SSL technology adoption,
allows to provide substantial relief from the pressure to
obtain additional power quantities in almost all developed
economies. In under-developed countries, the major
impact of SSL devices might be to provide high-quality
lighting in places where the illumination level has
previously been inadequate. For off-grid communities or
sites, the diffusion of SSL sources and photovoltaic
technology offers an optimal solution for lighting facilities
feeding instead of developing the grid to deliver
electricity.
(b)
(a)

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Figure-6. Photovoltaic technology offers an affordable
solution for power supplying the light points, allowing to
obtain electricity in many developing countries and places.
In addition to the money savings, solar-powered
LED lighting offers substantial environmental and health
benefits. The burning of kerosene lamps, still diffused in
many countries, produces several emissions such as black
carbon, strongly implicated in climate changes and a
responsable for global warming, producing the equivalent
of 240 million tons of CO
2
each year. The use of kerosene
lamps is also dangerous due to the risk of fires and
toxicity, containing high amount of heavy particulates
(Mills, 2016). According to the 2016 report prepared by
Bloomberg New Energy Finance and Lighting Global for
the Global Off-Grid Lighting Association, the off-grid
solar lighting market has experienced remarkable growth
in the past 5 years, with more than 100 companies selling
20 million branded products. These solar powered LED
lamps have provided light for about 100 million people, or
less than 8% of the potential market. Kenya, Tanzania and
Ethiopia are Africa’s prime markets while India is leader
in Asia (Off-Grid Solar Market Trends Report, 2016).
On the other hand, due to the increasing use of
renewable energies, home storage systems for electricity
produced by photovoltaic (PV) facilities are gaining
attractiveness, as their cost is reducing. These systems
store excess amounts of irregularly produced solar or wind
power and makes it available when necessary to power
supply the household appliances. More and more private
houses use storage systems to temporarily store power
generated by photovoltaics plants; instead of consuming
power from grid, the households can increasingly feed
home facilities and appliances by using renewable energy
produced on their own (Visconti et al., 2015).
Figure-7. Photovoltaic off-grid plant employed to feed
household facilities and appliances.
The major barrier to more rapid adoption of
renewable energies has been the shortage of financing and
loans to potential customers in order to realize the
necessary distribution infrastructure. The cost of solar
panels and storage batteries has not decreased over time as
rapidly as that of the LED-based lighting sources. Thus,
the major further contribution that the SSL technology can
make would be to increase the efficacy of the LED
packages in order to reduce the necessary capacity of solar
panels and batteries that feed the lighting systems.
However, with the introduction of flexible thin-
film solar cells shown in Figure-8a, the solar power
generator can be integrated into the building envelope
replacing conventional materials in roof, skylights or
facades (named building integrated photovoltaics). Sharp,
a solar panel manufacturer with headquarter in Japan,
recently introduced transparent solar power windows, as
shown in Figure-8b. There are no moving parts involved
in photovoltaic embedded systems and no related electrical
or acoustic noise; these features favours domestic solar
plants respect to other green-techs such as wind turbines.
Figure-8. Technological advancements in PV production:
flexible thin-film solar cells (a) and transparent solar
power windows (b).
(a) (b)

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The majority of today’s photovoltaic systems
does not require a lot of maintenance. Residential solar
panels usually only require cleaning a couple of times a
year. Major solar manufacturers guarantee a properly
operation for 20 or 25 years of their photovoltaic panels.
Technological advancements are continuously made in the
solar power industry; the innovations in nanotechnology
and quantum physics have the potential to strongly
increase produced electrical power from the solar panels.
ARCHITECTURE AND OPERATION MODE OF
SOLAR POWERED LED-LIGHTING SYSTEMS
The reduction of maintenance costs by improving
lamp life and luminaire’s reliability is a key factor of
outdoor lighting. In fact, for some outdoor applications
such as roadways, the obtainable maintenance savings can
far exceed energy savings. Solar-powered LED-based
street lamps require very little maintenance and are easier
to install than their wired counterparts connected to mains.
Underground wiring, on-site transformers and electrical
enclosures are typically more costly than installing new
photovoltaic lights. LED lamps require fewer
replacements, are dimmable and ensure significant energy
savings respect to traditional lamps (Visconti et al., 2013).
Sun light is converted into DC electricity when it falls on
the top surface of the solar cells inside the PV module by
means of photovoltaic conversion process. The generated
electricity can either be directly used during the sunshine
hours or may be stored in storage batteries to be used later.
Solar street lighting systems essentially include a properly
sized PV module, a battery whose charge is managed by
an electronic controller and in some cases an automatic
dusk-dawn switching system for turning on at the dusk and
off at the dawn the street lights.
Figure-9. Main components of solar powered LED-based
street lighting systems.
Therefore, solar panels harness solar energy
converting it into electric energy that, during the day, is
stored into the battery and, during the night, used to power
supply the street lamps.
Figure-10 shows the principal functional blocks
of a solar powered LED-based street lamp: a photovoltaic
module, a LED lamp, a charge controller and a lithium
battery are employed. Also a motion sensor is used in
order to switch on/off the LED street lamp depending on
the presence or absence of some pedestrian or vehicle.
Figure-10. Typical solar powered LED-based street lamp
with embedded a motion sensor.
A solar powered LED lighting system can include
other different components, as reported in Figure-11, such
as a device for anti-theft protection, an anti-corrosion
treatment and a solar tracking device for following the
solar movement to keep the PV panel facing the sun. In
fact, by rotating solar panels to track the sun’s path during
the day, more solar energy up to 30% can be captured
(Visconti et al., 2016).
Figure-11. Typical solar powered LED-based system with
anti-theft protection and a solar tracking device to follow
the sun's path.
The key component of the LED-based street lamp
is the LED source itself which allows to properly
illuminate the desired area using less energy and with
improved uniformity compared to a HID source, beside
other advantages such as reliability, long life-time,
improved color quality and reduced costs. A street lamp
usually consists of many LED-lens combinations; in

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Figure-12, a typical LED lamp for outdoor applications
with indication of its different sections is shown.
Figure-12. Typical LED-lamp with indication of the
different sections that allow its proper functioning.
More recent lighting systems use wireless
technology and fuzzy control theory for battery
management. The street lights using this technology can
operate as a network with each light point, having the
capability of performing on or off the network.
Figure-13. Image of street light wirelessly controlled by
remote terminal (a) and presence sensor embedded
in the LED-based lighting system (b).
WIRELESS MONITORING AND CONTROL OF
OUTDOOR LIGHTING SYSTEMS WITH
DIFFERENT SENSORS EMBEDDED
Connected lighting, smart lighting and adaptive
lighting are some of the terms that describe recent
innovations in the lighting industry enabled by the
development and diffusion of SSL technology. SSL is
fundamentally controllable, can be designed to be
spectrally tunable and can easily provide, with minimum
cost, additional functionalities by integration of sensors,
processors and network interfaces, as shown in Figure-14.
Figure-14. Wirelessly controlled lighting system: network
node can accommodate additional functionalities through
the integration of sensors (a). Lighting system wirelessly
driven and controlled through a cellular network (b).
The integration between SSL tecnology, low-cost
sensors, smartphones and IoT-based devices is expected to
facilitate new lighting functionalities and a great exchange
of data among lighting systems, installed everywhere both
inside or outside of buildings, and a data collection/
processing device (e.g. PC, tablet, smartphones) through
cellular or Internet network. The ubiquity of lighting
facilities, in fact, provides a unique and valuable
opportunity to create a dense grid of network nodes for
environmental/security data collection and sharing, as
shown in Figure-15. This causes not only improved
lighting control and energy management but also ensures
traffic and sites monitoring getting more safety or early
flood prediction or other useful services for community.
Figure-15. Connected lighting facilities: a base-station
wirelessly communicates with other close nodes and with
a central system through a cellular / IP internet network.
(a)
(b)
(a) (b)

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In addition to presense, motion and daylight
sensors, other types of sensors could be installed on a
street light pole, including those to measure CO2
concentration, vibration, sound level, barometric pressure
or to capture environment videos or photos. This allows
for data collection and exchange in ways not previously
possible so that the building owners/operators can manage
and better understand their physical environment ensuring
greater productivity, efficiency and security (Kathiresan et
al., 2014), (Sharath Patil et al..2015).
Figure-16. Extra services provided to a smart city when
utilizing LED lighting street poles integrated with sensors.
To create a smart city, a dense sensor network
must be deployed to provide data on different parameters
such as air quality, weather warnings, video surveillance,
parking space availability and traffic patterns. The
installation of new LED street lights guarantees to cities
considerable savings through increased energy efficiency,
decreased maintenance needs, longer life-times; it can be
the platform used to integrate a sensor network providing
additional features to the city, as illustrated in Figure-16.
By adding wireless controls to monitor and drive
lighting system integrated with sensors, LED street lights
act as a wireless mesh communication network that would
have a prohibitive cost if realized separately. Detected data
are sent to a centralized control unit which can be used to
provide to city staff useful information and to ensure
appropriate site control for police officers activity, as
shown in Figure-17. Thus, the street light poles could
become the ideal platform for adding environmental
sensors and security infrastructures, such as a cameras or
acoustic sensors to detect, for example, gun shots cackles
or cries of alarm in real time, and thus alerting the police
staff (Priyanka et al., 2015), (Saleem et al., 2015).
Furthermore, due to the low cost of devices,
sensors and electronic equipments available today thanks
to technological advances, the value of additional provided
services, made possible by means of SSL technology, fully
offsets the incremental costs of the sensors, network
interfaces and other additional components.
Figure-17. Collected data are sent to a centralized control
unit to monitor and control the road environment.
The smart cities provided with LED-based
lighting systems will save money because LED lights are
more energy efficient than the outdated High Pressure
Sodium (HPS) lamps and also because each LED street
light can be easier switched on on-demand or by
presence/motion sensors, thus paying only for used
energy. In addition, city officials will be able to program
when turning on/off street lights or dimming their
brightness to obtain further energy savings (e.g. providing
a 100% brightness when it turns dark and gradually to
reduce to 50% in the middle of the night, returning to full
brightness in the early morning for commuters).
Connected street lights, beside the countless services that
can offer, also communicate to the maintainers location
and possible failure of each light pole for efficent and
quick maintenance (Santhosh et al., 2015).
Figure-18. Smart city platform employs a dense grid of
network nodes for providing new different services and
also ensuring energy savings and quick maintenance.

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In conclusion, new LED-based facilities made up
of connected light points will become data collection
platforms enabling even greater lighting and non-lighting
energy savings in smart buildings and cities. This ability to
collect and exchange useful data, making use of the IoT
capabilities, will offer the potential to enable a wide
variety of services, benefits and new revenue streams that
will enhance the money value of lighting plants itself.
While the addition of sensors does not add any
significative cost to final street light facility, the 7-pin
American National Standards Institute (ANSI) receptacle
allows manufacturers an easy way to add on a sensors
location (see Figure-19). A wireless node can be added to
the street light receptacle providing the following features:
 Accurate, utility-grade energy metering for each street
pole, thus paying only for used energy.
 GPS chip embedded into sensor node, so knowing its
exact location.
 The node automatically connects to network and
acquires or transmits information in a short time so
reducing related costs.
 Control and sensing units integrated in a single piece
(in blue color in Figure-19). Node simply is connected
to external socket so it can be added easily at any time
without additional electronics in the LED street light.
 Operates with programmed schedules in case of
network outage.
Figure-19. LED street lamps with added the sensor node.
NEW LED-BASED LIGHTING TECHNOLOGIES
FOR ENERGY SAVINGS AND LOW COST
MAINTENANCE
Besides improved form factors and building
integration as reported in the introduction, SSL offers a
new range of features and design flexibility. For indoor
applications, an example of the design flexibility of LED
lighting technology and of efficient light utilization is the
OSRAM OmniPoint
TM
, a remotely manageable lighting
system that enables users to instantly shape the emitted
light (i.e., beam angle, direction, distribution, shape and
intensity) with a touch screen wireless interface (Figure-
20b). As shown in Figure-20a, the luminaire consists of an
array of individually controlled LED devices with a small
aperture, allowing wirelessly to properly illuminate an
ambient and/or a dark hidden place on user demand.
Figure-20. The OSRAM OmniPoint
TM
luminaire (a) and
the relative wireless user interface (b).
The user interface, shown in Figure-20b, allows
to select portions of space of the ambient in which adjust
lighting, as well as to control light intensity in the whole
room, so obtaining energy savings. Thus, this lighting
device offers significant improvement over traditional
lighting systems which would require a manual adjustment
of multiple fixtures on the ceiling (Mathews et al., 2016).
For outdoor applications such as street lighting
facilities, the use of integrated sensors allows to obtain
different services as discussed before, besides energy
savings. The street light system, reported in Figure-21, is
an example in which its turning on with full brightness is
provided only in case of presence/motion of vehicles. In
fact, lighting system decides if there is need of light or not,
detecting the movement of a vehicle and thus turning on
lights when the vehicle is coming and then reducing up to
50% light brightness when vehicle passes away.
(b)
(a)

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Figure-21. Detecting system of vehicles movement on
highways or roads to properly adjust light brightness;
oncoming car (a) and sequence of lighting switching
during car transition (b and c).
The latest innovations in street lighting systems
provided by EnGo company, a famous manufacturer of
lighting facilities, regard modern and multifunctional
solutions powered by solar and kinetic energy. By
exploiting only renewable energy sources, it is possible to
illuminate streets, parks, parking lots, corporate and
university campuses and to create appealing and modern
visual environments that will promote more and more
renewable energy diffusion due to lower installation,
energy and maintenance costs. In Figure-22, the possibility
to use kinetic energy tiles, through piezoelectric devices, is
shown; in this application, energy is recovered from
pedestrians’ footsteps for feeding LED-based street lamp.
Figure-22. Piezoelectric tiles allow to obtain energy from
pedestrians’ footsteps for street lamp power supply.
With a remote management platform and many
incorporated sensors, the LED-based street lighting system
transforms traditional street light to a multifunctional unit
that will save money and collect many valuable data.
These last, collected from different integrated sensors, are
sent on cloud for monitoring and control environmental
parameters and not only, as reported in Figure-23.
The additional innovative features such as set of intelligent
sensors, LED color change, charge spot as shown in
Figure-24, represent a revolutionary step forward in
modernizing of public lighting facilities.
Figure-23. Environmental information are collected by
integrated sensors (a) and sent on cloud (b).
Figure-24. Charge spot provided by the street light pole in
order to give to the user a further service making use of
renewable energy.
In conclusion, the light street pole may provide
many services thanks to the numerous sensors embedded
and to the available renewable energies for feeding LED
lamp, sensors and charging spot. As reported in Figure-25,
thanks to intelligent sensors and using PV panel or tiles to
exploit solar or kinetic energy respectively, it is possible to
realize a multi-function light point, maintaining low power
consumption and low maintenance costs.
(a) (b)
(a) (b)
(c)
CHARGE
SPOT
KINETIC
TILES

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Figure-25. Many services can be provided by new LED-
based street light pole, thanks to the integrated sensors,
exploiting the available renewable energies.
CONCLUSIONS
In this paper, we reported on new technologies
and devices employed in advanced solar powered LED-
based lighting systems, used for both outdoor and indoor
applications, in order to obtain energy savings, new
additional services for smart cities and quick low-cost
maintainance. LED lights are up to 80% more efficient
than traditional lamps, ensuring huge energy savings but
also suitable illuminance levels, improved light
distribution by using proper focusing lenses, illuminance
uniformity and producing less wasted light falling outside
the target area.
An efficient light utilization is very important; in
indoor applications, where OLEDs and low brightness
planar LED solutions can be employed, the low brightness
and diffuse nature of these sources enable them to be used
very close to the task area without generating excessive
glare and with the possibility to adjust brightness in
specific areas so creating desired lighting scenarios.
For off-grid communities or places, solar-
powered LED-based lighting systems offer an excellent
solution to efficently illuminate large areas rather than
bringing the electric grid to deliver needed electricity.
Solar LED lighting gives substantial environmental and
health benefits beside energy savings, such as the non-use
of kerosene, still diffused in under-developed countries,
that produces heavy particulates. Furthermore, new LED-
based lighting facilities require very little maintenance and
are easier to install than the wired counterparts, due to not
need to carry the mains voltage being supplied by solar or
kinetic energy, as described previously.
With the huge diffusion of IoT-based devices and
apps, it is possible wirelessly to control and drive the
LED-based lighting facilities, that can be provided of
integrated sensors, thus realizing new lighting
functionalities, improved management of the energy in
order to obtain energy savings and new services for the
community. By adding wireless modules, LED street
lights act as a mesh communication network, collecting
and sending data on cloud to a centralized control unit,
used to provide to city staff useful information and to
ensure appropriate site control for police officers. Street
light poles could become ideal platform for adding
environmental sensors and security infrastructures but also
to communicate to the maintainers location and failures of
each light pole for efficent and quick maintenance.
The additional innovative features such as smart
sensors, LED color change, availability of charge spots
and other services represent a revolutionary step forward
in modernizing public lighting facilities. Therefore, by
exploiting only renewable energy sources (solar, kinetic or
provided by wind), it is possible to illuminate streets,
parks, parking lots and university campuses but also to
provide other services to the community, ensuring, first of
all, energy savings, lower installation and maintenance
costs.
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