Light Emitting Diode Street Lighting Research Articles

Are LED lights driving the massive nuptial flight swarm of the tramp ant Technomyrmex albipes?

AbstractWhereas most economic and ecological impacts of tramp ant species stem in large part from numerical dominance and exacerbated aggressiveness of workers, those imposed by alate (winged) ants have been rarely described. In the present study, we report an unprecedented massive alate swarming (i.e., mating flight) event in southern Taiwan by a tramp ant species, Technomyrmex albipes (Smith) (Hymenoptera: Formicidae), that triggers immediate pest management responses, and examine factor(s) that potentially contribute to the remarkably high number of alates. We monitored the seasonal activities of T. albipes workers and phenology of alate swarming, attempting to link the worker foraging dynamics with swarm ontogeny. As it was argued that recent streetlight fixtures converted from high‐pressure sodium to light‐emitting diode (LED) may serve as a major cause of the massive swarming, alates' light color preference was investigated. Sex ratio of trapped alates was also assessed to test whether sex‐specific light preference exists in T. albipes. We showed that foraging intensity of workers increased in the spring, peaked in May, and was followed by the nuptial flight season that began in August and lasted for 4 months. The phenological pattern is consistent with the colony dynamics in many other ant species. Although the two light preference experiments did not yield the same results, T. albipes alates overall preferred lights with shorter wavelengths in the active trapping, partially supporting the argument of white LED streetlights contributing to the massive flight. The sex ratio of trapped alates was overall female‐biased, suggesting female alates are disproportionally produced and/or more sensitive toward lights.

Development and Implementation of LED Street Lights with Bright and Extinguishable Controls and Power Converters.

This study developed and implemented a driving power supply for light-emitting diode (LED) array streetlamps. The power stage was a quasi-resonant (QR)-flyback converter, its input power was the alternating-current power, and the LED array streetlamp was driven by the direct-current output power. The developed QR-flyback converter was operated in discontinuous conduction mode, and the pulse-width modulation (PWM) control chip was used to switch and conduct at the resonant valley of the drain-source voltage on the metal-oxide-semiconductor field-effect transistor (MOSFET) switch to reduce the switching loss. Moreover, the PWM control chip had a disable function, which was connected with a bright and extinguishable control circuit, and the high/low voltage level signal output by the Arduino development board can be used to control the output power of the QR-flyback converter, achieving bright and extinguishable controls for the LED array streetlamp.

A Novel Light-Emitting Diode Streetlight Driver Circuit Applied to a Direct Current-Input Voltage Source

With the global advocacy of green lighting and the urgent need for energy saving and carbon reduction, more and more street lighting applications have entered the era of being replaced by light-emitting diode (LED) lighting sources. This paper presents a new LED streetlight driving circuit applied to a direct current (DC)-input voltage source, which consists of a buck converter combined with a flyback converter to reduce the number of circuit components required and to recover the leakage energy of the transformer to improve energy conversion efficiency. In addition, this study also completed the analysis of the operational principle of the new LED streetlight driving circuit, and developed a prototype LED streetlight driver with DC-input voltage of 48V and output power of 72 W (36 V/2 A). Finally, the measurement results of the prototype circuit show that the output voltage ripple rate was less than 15%, the output current ripple rate was less than 6%, and the circuit efficiency was as high as 91%.

Polyethersulfone wick and metal wick based loop heat pipe for LED street light thermal management

The challenge of dissipating heat from light-emitting diode (LED) poses a limitation on LED's application. Loop heat pipe (LHP) is an efficient heat transfer device that is used in the thermal management of electronic components. Therefore, in this article, an LED with an LHP as the heat dissipation solution was designed and investigated for the replacement of halogen street lights without changing other accessories of the existing street lights. The prototypes with sintered nickel wick and polyethersulfone (PES) wick were studied at the tilt angle from 0° to 12° and the ambient temperatures from 16 °C to 50 °C. In addition, five prototypes were tested for 50 days to verify the stability of the PES wick. The solution could solute the heat dissipation problem of the LED in a limited space and inclination. From the results, the PES wick showed a better performance. When the power was 110 W and the angle was 12°, the temperature of the light source could be below 62 °C and the thermal resistance could be below 0.37 °C/W. The results demonstrate that the ability of the prototype with PES wick can well solute the heat dispassion problem of the LED.

Experimental and numerical analysis of effect of combined drop-shape pin fins and plate fins type heat sink under natural convection

As the junction temperature of a light-emitting diode (LED) is inversely proportional to its lifespan and efficiency. This study investigates the thermal performance of heat sink-based model with a drop-shaped pin fin for LED cooling under natural convection, experimentally, and numerically. The study used three distinct drop form pin fin arrays with variable vertical fin spacing (Sv = 25, 50, and 75 mm), with the best array being used in subsequent studies with variations in drop-shaped pin fin size (diameter DD and apex length LD ). The heat transfer coefficient and Nusselt number were obtained in the quantitative analysis of thermal performance. A numerical model with Boussinesq approximation for natural convection is used for this study and well-validated with experimental results. A qualitative investigation was also carried out utilizing numerical research to investigate velocity streamlines and their impacts on heat transfer enhancement in various configurations. An experimental test with conventional plate fin, circular pin fins were done for the verification of the test setup results and their results were compared with results calculated from the standard correlations presented in previous well-known literature. The maximum heat transfer coefficient was found to be 12.80 W/m2K for drop form pin fins with vertical fin spacing (Sv ) equal to 75 mm, a diameter of 6 mm, and a length of 7.2 mm, and the corresponding Nusselt number was 94.85. Also, the maximum enhancement in Nusselt number was found to be (Nu/Nu plate fin) 3.11 corresponding to the conventional plate-fin heat sink. This comparison will help the industrialists determine innovative passive cooling technology for electronic devices such as LED street lights.

Towards smart sustainable cities using Li-Fi technology: geo-location infrastructure utilizing LED street lights.

BackgroundCities are shifting toward providing more efficient services and the Internet of Things (IoT) becoming the future of things. The shift toward using eco-friendlier LED lights in lighting cities is another genuine game-changer in the future of Light Fidelity technology (Li-Fi). Li-Fi is a visible light communication (VLC) technology that uses Light Emitting Diodes (LED) bulbs for communication. The utilisation of thousands of light sources around a city acting as wireless access points and delivering location-based content will shift cities towards being smart sustainable cities. Recently, this technology got huge attention from the research community and different research has been conducted to improve this filed. However, there is a noticeable need to develop real-world systems that utilise Li-Fi technology.MethodsThis article aims to contribute to developing a Geo-Li-Fi system that uses LED lights to provide the services for collecting contextual data and delivering location-based services (LBS) in different areas of the city. The system is described along with details of its design, implementation and development. Moreover, the overall set-up of the testbed that used to evaluate the proposed system is presented. In addition, an experiment is conducted using a real-world scenario to test the functionality of the system and report the outputs.ResultsThe effect of the system is discussed according to different aspects of sustainability which include economic, social and environmental aspects. The system was tested in indoor and outdoor environments, and it can be seen that the sunlight does not affect the ability of LEDs to deliver the content during the daytime. Regarding the transmission range of the LED lamp, it can be seen that it is affected by different factors. It depends mainly on the power of lamp, so it will be increased significantly when the power of LED is increased. Also, an increase in the beam angle will result in wider coverage area which affected by the intensity.

A Review of Automatic Irradiation Adjustment Based LED Street Light with Vehicle Movement Detection

Abstract: In present day, the maintenance of streetlight is one of the major problem for electricity boards in India. Also, there is scope for saving power during off peak time i.e. in from around midnight 12AM to 04AM in the morning. The methods that are currently used to maintain and control the street light is more complex and uneconomical. In this paper a new technique is proposed to control the intensity of LED Street lights using LDR, and to automate street lights using PIR sensors, and LDRs, resulting in power saving. Implementation is done using PIC controller. This paper presents a smart street lighting system which provides a safe night time environment for all road users and pedestrian. The main objectives are to build an automation system of street lighting using a low-cost microcontroller which is PIC and to achieve energy-saving. Light Emitting Diode (LED) is represented as the light module. This system is controlled according to the specific mode. These modes are controlled by two sensors which are Light Dependent Resistor (LDR) and Passive Infrared (PIR) sensor. This system can automatically turn on and off the lights according to traffic flow. This system operates during the night and the focus is only for the one-way road at a junction. Street light will be on when only there is road user otherwise, it will turn off. This design can save a great amount of electricity or energy consumption compared to conventional street lights that keep alight during nights. Moreover, the maintenance cost can be reduced and lifespan of the system will increase. As the result, the system has been successfully designed and implemented as a model system Keywords: PIR, LDR, Streetlights, Power supply, microcontroller

Review of Various Technology Automatic Dimming Control of LED Street Light

Abstract: In present day, the maintenance of streetlight is one of the major problem for electricity boards in India. Also, there is scope for saving power during off peak time i.e. in from around midnight 12AM to 04AM in the morning. The methods that are currently used to maintain and control the street light is more complex and uneconomical. In this paper a new technique is proposed to control the intensity of LED Street lights using LDR, and to automate street lights using PIR sensors, and LDRs, resulting in power saving. Implementation is done using PIC controller. This paper presents a smart street lighting system which provides a safe night time environment for all road users and pedestrian. The main objectives are to build an automation system of street lighting using a low-cost microcontroller which is PIC and to achieve energy-saving. Light Emitting Diode (LED) is represented as the light module. This system is controlled according to the specific mode. These modes are controlled by two sensors which are Light Dependent Resistor (LDR) and Passive Infrared (PIR) sensor. This system can automatically turn on and off the lights according to traffic flow. This system operates during the night and the focus is only for the one-way road at a junction. Street light will be on when only there is road user otherwise, it will turn off. This design can save a great amount of electricity or energy consumption compared to conventional street lights that keep alight during nights. Moreover, the maintenance cost can be reduced and lifespan of the system will increase. As the result, the system has been successfully designed and implemented as a model system. Keywords: PIR, LDR, Streetlights, Power supply, microcontroller

Review of Various Technology Automatic Dimming Control of LED Street Light

In present day, the maintenance of streetlight is one of the major problem for electricity boards in India. Also, there is scope for saving power during off peak time i.e. in from around midnight 12AM to 04AM in the morning. The methods that are currently used to maintain and control the street light is more complex and uneconomical. In this paper a new technique is proposed to control the intensity of LED Street lights using LDR, and to automate street lights using PIR sensors, and LDRs, resulting in power saving. Implementation is done using PIC controller. This paper presents a smart street lighting system which provides a safe night time environment for all road users and pedestrian. The main objectives are to build an automation system of street lighting using a low-cost microcontroller which is PIC and to achieve energy-saving. Light Emitting Diode (LED) is represented as the light module. This system is controlled according to the specific mode. These modes are controlled by two sensors which are Light Dependent Resistor (LDR) and Passive Infrared (PIR) sensor. This system can automatically turn on and off the lights according to traffic flow. This system operates during the night and the focus is only for the one-way road at a junction. Street light will be on when only there is road user otherwise, it will turn off. This design can save a great amount of electricity or energy consumption compared to conventional street lights that keep alight during nights. Moreover, the maintenance cost can be reduced and lifespan of the system will increase. As the result, the system has been successfully designed and implemented as a model system. Key Words: PIR, LDR, Streetlights, Power supply, microcontroller

A Review of Automatic Irradiation Adjustment Based LED Street Light with Vehicle Movement Detection

In present day, the maintenance of streetlight is one of the major problem for electricity boards in India. Also, there is scope for saving power during off peak time i.e. in from around midnight 12AM to 04AM in the morning. The methods that are currently used to maintain and control the street light is more complex and uneconomical. In this paper a new technique is proposed to control the intensity of LED Street lights using LDR, and to automate street lights using PIR sensors, and LDRs, resulting in power saving. Implementation is done using PIC controller. This paper presents a smart street lighting system which provides a safe night time environment for all road users and pedestrian. The main objectives are to build an automation system of street lighting using a low-cost microcontroller which is PIC and to achieve energy-saving. Light Emitting Diode (LED) is represented as the light module. This system is controlled according to the specific mode. These modes are controlled by two sensors which are Light Dependent Resistor (LDR) and Passive Infrared (PIR) sensor. This system can automatically turn on and off the lights according to traffic flow. This system operates during the night and the focus is only for the one-way road at a junction. Street light will be on when only there is road user otherwise, it will turn off. This design can save a great amount of electricity or energy consumption compared to conventional street lights that keep alight during nights. Moreover, the maintenance cost can be reduced and lifespan of the system will increase. As the result, the system has been successfully designed and implemented as a model system Key Words: PIR, LDR, Streetlights, Power supply, microcontroller

Quantifying wedge-tailed shearwater (Ardenna pacifica) fallout after changes in highway lighting on Southeast O'ahu, Hawai'i.

Attraction to artificial light at night (ALAN) poses a threat to many fledgling seabirds leaving their nests for the first time. In Hawai'i, fledgling wedge-tailed shearwaters disoriented by lights may become grounded due to exhaustion or collision, exposing them to additional threats from road traffic and predation. While the timing and magnitude of shearwater fallout varies from year to year, little is known about how changing lighting and environmental conditions influence the risk of grounding for this species. We analyzed 8 years (2012-2019) of observations of road-killed shearwaters along the Kalaniana'ole Highway on O'ahu to quantify the timing and magnitude of fallout during the fledging season (November-December). Our goal was to compare fallout before (2012-15) and after (2016-19) a transition in highway lighting from unshielded high-pressure sodium (HPS) to full-cutoff light-emitting diode (LED) streetlights. To detect the shearwater response to the lighting regime, we also accounted for three potential environmental drivers of interannual variability in fallout: moon illumination, wind speed, and wind direction. The effects of these environmental drivers varied across years, with moon illumination, wind speed and wind direction significantly affecting fallout in at least one year. Altogether, the interaction between moon illumination and wind speed was the most important predictor, suggesting that fallout increases during nights with low moon and strong winds. The lack of an increase in fallout after the change from HPS to shielded 3000K - 4000K LED streetlights suggests the new streetlights did not worsen the light pollution impacts on wedge-tailed shearwaters on Southeast O'ahu. However, due to potential species-specific disparities in the behavior and light attraction of petrels, similar studies are needed before energy saving LED lights are implemented throughout the Hawaiian archipelago.

Study of glaring effect from light emitting diodes via lens approach

The purpose of this study was to evaluate the glaring effect from light-emitting diode (LED) streetlight with two different brands of lens (Lens A and Lens B). By using DIALux Evo with 70W LED luminaires, same scenarios of road lighting designs with pole distance of 35m and pole heights of 10 m on a 7 m wide road was evaluated from both the lenses. Calculation was performed on a section defined by one pole on one side of the road (single row). The pole height, light overhang and boom length were 10m, 1m and 1.5m, respectively. The light loss factor was 0.80. TracePro was used to simulate the distribution of light by tracing rays. All mounted luminaries have three zones of light output which are backlight, uplight and frontlight. Both frontlight and backlight sub-zones are factored into the glare rating. Lens B demonstrated a better threshold increment (8) and the lowest lumens for glare rating as compared to Lens A. This was due to the shape of lens. Smaller shape of lens contributes to narrower light distribution patterns as well as smaller average beam angle, suggesting that Lens B was more suitable for LED streetlights.

Vehicle positioning scheme based on visible light communication using a CMOS camera.

As an application of visible light communication (VLC), visible light positioning (VLP) technology has great potential for vehicle positioning due to its characteristics of no electromagnetic interference, low cost, and high positioning accuracy. In addition, the light emitting diode (LED) in street lights, traffic lights and vehicle lighting systems makes this positioning solution attractive for vehicular applications. However, the modulated LED signal will bring blooming effects on the images captured by a complementary metal oxide semiconductor (CMOS) camera. And it will decrease the positioning performance. Meanwhile, positioning errors will happen when the CMOS camera is tilted. In the paper, a vehicle positioning scheme based on VLC is proposed and experimentally demonstrated. It uses LED street light as a transmitter and the CMOS camera as a receiver. To mitigate the blooming effect in the CMOS camera based VLC, a bit length estimation (BLE) based sampling scheme is proposed to obtain the reference location information from the captured images. In addition, a novel angle compensation scheme combined with a particle filter is proposed to improve the accuracy of vehicle positioning when the CMOS camera is tilted. The experiments are performed under moving speeds of 40 to 80 cm/s and the measured distances of 80 to 115 cm. Assuming the performance of the proposed demonstrator is not modified when upscaling its size to a real scenario (such as speeds of 4 to 8 m/s and distances between the LED and camera of several meters), it can be concluded that as the speed of the moving vehicle is 8 m/s, the proposed vehicle positioning scheme based on VLC can achieve positioning accuracy of 0.128 m and 0.13 m for the tilt angles of 9° and 15.5°, respectively.

Rational Basis for Light Emitting Diode Street Lighting Retrofit Luminaire Selection

Many municipalities are beginning to undertake efforts to retrofit their existing high pressure sodium (HPS) street lighting with LED (light emitting diode) luminaires. Unlike HPS lighting systems, which are available in a limited range of standard wattages and configurations, LED street lighting systems vary widely in wattage and physical configuration. Moreover, the technological performance of LED lighting continues to improve, whereas HPS is a mature technology with substantial improvements unlikely in the future. To develop a sound basis for selecting LED lighting systems for retrofit street lighting, photometric simulation calculations under a range of pole spacing, road width and luminaire wattage were performed. The results indicated that LED luminaires can have substantially lower wattage than HPS luminaires to produce the same light levels on the road. Further, LED luminaires tend to direct more of their output onto the road compared with HPS luminaires. As a result, LED luminaires can be used that produce substantially fewer lumens overall than HPS systems. Because the white light from LED sources makes illuminated street scenes appear brighter than the yellowish light from HPS lamps, even further reductions in light output can be accomplished with LED street lighting systems to match the same visual effect under HPS.

Light-Emitting Diodes (LED): A Promising Street Light System to Reduce the Attraction to Light of Insects

Currently, there is a demand for more energy-efficient lighting sources, however, light emitted by different lighting systems differs in primary properties such as intensity, propagation direction, and wavelength spectrum, among others, and these properties may affect insect light attraction. Despite the energetic benefits of light-emitting diodes (LED) as street light systems, their ecological impacts on insects have not yet been tested on a wide range of taxa. Using an experimental approach, we showed that LED street lights lead to a reduction in the total number of insects captured with light traps in a wide range of families. Coleoptera and Lepidoptera orders were the most sensitive groups to ecological light pollution in the study area. We suggest that LED was the least attractive light system for most of the affected groups both because of its very little emitted short-wavelength light and because of its lower light intensity. We expect that the more and more widespread use of LED lights as a measure to reduce economic costs of outdoor lighting should lead to a lower attraction to street lights in most of the affected insect taxa and to diminish the negative impacts of artificial light attraction on the ecosystems.

Retrofitting streetlights with LEDs has limited impacts on urban wildlife

Artificial light at night (ALAN) causes a wide range of ecological impacts across diverse ecosystems. Most concentrated in urban areas, ALAN poses a particular risk to associated wildlife by disrupting physiology, behaviour and ultimately survival. This risk is predicted to shift as nighttime lightscapes in many cities undergo change. Globally, streetlights are currently being retrofitted with newer technologies that differ in the spectrum and intensity of their emissions, but there is a dearth of in situ urban experiments on the ecological impacts of this change. We monitored timing of dawn and dusk bird song; frequency of owl vocalisations; avian diversity, relative abundance and community composition; small invasive mammal and ground insect activity; and invertebrate relative abundance at 26 residential properties over an 18-month period that coincided with a retrofit from high-pressure sodium (HPS) to white light-emitting diode (LED) streetlights. Initiation time of dawn song was advanced or delayed for two bird species following the retrofit and backyard avian community composition was altered. Avian species richness, relative abundances of three bird species and ground insect activity increased in the presence of LED streetlights. No other retrofit effects were found. Our study suggests that retrofitting streetlights with white LEDs may lead to both positive and negative conservation outcomes for urban wildlife, but direct impacts are relatively small and may be mitigated by changes in lighting characteristics, such as dimming. Streetlight retrofits could provide an opportunity to reduce the impacts of ALAN on urban wildlife if intentionally designed with conservation benefits in mind.

A Single-Stage High Power Factor Power Supply for Providing an LED Street-Light Lamp Featuring Soft-Switching and Bluetooth Wireless Dimming Capability

Light-emitting diode (LED) has the characteristics of environmental protection and energy saving, having become the lighting source of a new generation of street-light lamps. The traditional two-stage power supply for providing an LED street-light lamp is composed of an AC-DC converter with a power-factor-correction (PFC) function at the front stage and a DC-DC converter at the rear stage. The two-stage power supply for an LED street-light lamp has a large number of electronic components and costs, and the circuit efficiency is not high. Therefore, this paper presents a novel single-stage high power factor AC-DC power supply for providing an LED street-light lamp featuring soft-switching and Bluetooth wireless dimming capability through using smart tablets or smartphones to remote control the output power of the LED street-light lamp for achieving energy-saving benefits. The proposed AC-DC LED power supply integrates an interleaved buck converter circuit with coupled inductors and a half-bridge LLC resonant converter circuit into a single-stage power conversion circuit. Moreover, the coupled inductor of the interleaved buck converter circuit is designed to operate in the discontinuous conduction mode, which can naturally achieve PFC. In addition, the two power switches in the novel LED power supply have zero-voltage switching (ZVS) characteristics, which can reduce the switching losses of the power switches. The two output diodes have the characteristics of zero-current switching (ZCS), which can reduce the conduction losses of the power diodes. This paper developed a single-stage prototype circuit for providing an 144 W (36 V/4 A)-rated LED street-light lamp. According to the experimental results of the prototype circuit with an AC input voltage of 110 volts, the presented single-stage LED power supply offers high power factor (PF > 0.99), low input-current total harmonic distortion factor (THD < 3%), and high efficiency (>89%). In addition, this paper used the built-in Bluetooth wireless communication function of a smart tablet or smart phone to fulfill remote dimming control. By changing the duty ratio of the control signal, we could realize remote dimming control of 20% to 100% of the output LED street-light lamp power.

Energy Sustainability Paradox: Exploring the Challenges and Opportunities of Solar LED Street Lights in Sokoto, Nigeria

Sustainability, quest for greener environment and energy/cost savings are some of the driving forces for the global push in utilizing renewable energy resources for powering street lights especially those located in densely populated areas. Photo-voltaic and LED technologies are considered by many as a match made in heaven as they are essential if not mandatory for achieving these goals. For 11 years (between 2007 and 2018), there has been a significant effort by Sokoto State Government to light up streets in the central part of the city using these two technologies. Using a descriptive approach, the paper established the status, challenges and opportunities associated with solar powered Light Emitting Diode (LED) street lights in Sokoto over the 11 years period. Out of 450 installed units in the city, only 25% are functional at present. The number is also gradually diminishing. The technological, social and institutional challenges associated with managing LED street light devices in the city were equally discussed. Promises of the technology, climatic conditions of the city and current push for metropolitan security are among the potential drivers for continuous implementation of the technology in the city. However, while the available solar power in the city serves as a driving force, its association with higher temperatures makes equipment maintenance difficult thereby undermining sustainability.

Switching LPS to LED Streetlight May Dramatically Reduce Activity and Foraging of Bats

Artificial light at night is considered a major threat to biodiversity, especially for nocturnal species, as it reduces habitat availability, quality, and functionality. Since the recent evolution in light technologies in improving luminous efficacy, developed countries are experiencing a renewal of their lighting equipment that reaches its end-of-life, from conventional lighting technologies to light emitting diodes (LEDs). Despite potential cascading impacts of such a shift on nocturnal fauna, few studies have so far dealt with the impact of the renewal of street lighting by new technologies. Specifically, only one study, by Rowse et al.2016, examined the effects of switching from widely used low pressure sodium (LPS) lamps to LEDs, using bats as biological models. This study was based on a before-after-control-impact paired design (BACIP) at 12 pairs in the UK, each including one control and one experimental streetlight. If Rowse et al. 2016 showed no effect of switching to LEDs streetlights on bat activity, the effects of respective changes in light intensity and spectrum were not disentangled when testing switch effects. Here, we conduct a retrospective analysis of their data to include these covariates in statistical models with the aim of disentangling the relative effects of these light characteristics. Our re-analysis clearly indicates that the switches in spectrum and in intensity with replacement of LPS with LED lamps have significant additive and interactive effects, on bat activity. We also show that bat activity and buzz ratio decrease with increasing LED intensity while an opposite effect is observed with LPS lamps. Hence, the loss or the gain in bat activity when lamp types, i.e., spectrum, are switched strongly depends on the initial and new lamp intensities. Our results stress the need to consider simultaneously the effects of changes in the different lights characteristics when street lighting changes. Because switches from LPS to LED lamps can lead to an increase in light intensity, such technological changes may involve a reduction of bat activity in numerous cases, especially at high LED intensities. Since we are currently at an important crossroad in lighting management, we recommend to limit LED intensity and improve its spectral composition toward warmer colors to limit potential deleterious impacts on bat activity.

Economic efficiency and energy security of smart cities

The aim of this paper is to provide an analysis of the determinants of economic efficiency and to assess the prerequisites for the energy security of smart cities. The main methods of the paper include an economic analysis of the infrastructure improvements that result in reducing the energy demand of the smart cities represented by the intelligent light-emitting diode (LED) street lighting system. Smart LED streetlights are getting increasingly popular in the world’s major metropolises as one of the leading components of the “smart” city. We compare the efficiency of LED street lighting used in smart cities with a commonly used lighting system based on sodium lamps. Our results demonstrate that LED street lighting system can significantly reduce the energy demand of any modern city. Moreover, we show that smart grids might help distribution systems within smart cities to better integrate intermittent renewable energy sources such as wind and solar. The main research novelty of our study compared to previous studies from the literature is the estimation of net profit (NP), Net Discounted Savings (NDS), as well as the total savings (TS) using the example of an average European metropolis. Our findings show that there is a need for better management including strong networks of leaders to drive smart city policies and investments and to cover wider city areas with economically sustainable projects and plans. In addition, our findings yield that smart city projects should aim at finding solution for smart connected local energy storage systems to support more renewable energy sources on the power grids. Our results might be of a special interest for city planners, local government stakeholders, as well as urban policy makers dealing with planning and managing smart cities.