7 This paper presents a lighting control system based on natural light monitoring and on occupancy control, characterized 8 by installation easiness, even for existing plants, and cheapness. 9 The system is based on a smart control unit and lighting control devices that can be directly mounte d on the lamps in 10 series connection. The installation is noninvasive and does not require any changes in the wiring system , since the 11 communication between each lamp and the control system is realized by means of a 2.4 GHz wireless protocol. The 12 system fun ctionality is ensured with any lamps, also with non -dimmable ones. Tests and functionality verifications on 13 the system were performed in laboratory, proving the applicability to real cases and performance s that are comparable 14 to the ones achievable with di mmable LED lamps, but with a significant cost saving. 15 Hypothesizing the application of the proposed system and of different control technologies and strategies to a real 16 academic classroom case study, different lighting scenarios have been simulated. Obta ined results allow quantifying the 17 effects in terms of energy consumption and CO 2 emissions relative to such scenarios, achieving up to 69.6% of energy 18 saving and 30.5% of CO 2 emissions avoided. From an economic point of view, the comparison between the pr oposed 19 control system and commercial systems show s a shorter PayBack Period, from 9 to 5 years. 20 Keywords: lighting control; universal lamp dimming; wireless system; energy saving; economic analysis. 21 1. Introduction 22 Energy consumption for lighting is, nowadays, responsible of about 20% of the overall energy consumption [1]. 23 This datum justifies the recent attempts for searching efficient technologies, able to contribute to energy consumption 24 reduction. 25 The high perfo rmances of LED (light emitting diodes) lamps pushed their rapid spread [2], leading to a direct 26 energy saving. 27 According to a study of Ozenc et al. [3], LED lamps, besides having a higher lighting efficiency compared to 28 fluorescent lamp, allow high savings in case of dimming. Hypothesizing a 50% dimming ratio, fluorescent lamps lose 29 24% of lighting efficiency, whilst LED lamps 1.3%. Therefore, in terms of energy efficiency, LED s are more suitable 30 for dimming than fluorescent lamps. 31 Differently, according to Doulos et al. [4], control systems are still not sufficiently examined. Lighting control 32 techniques and strategies represent a complex matter, due to their planning process, to the proper matching of the 33 2 dimming system for the used luminaires [4], to the installation features [5] and to the difficulties on the evaluation of 34 investment payback time [5 -6]. For all these reasons, spread of lighting control systems is slower than lamps and 35 luminaires. Nevertheless, research on lighting control systems proceeds along different directions. In some cases, 36 scientific developments aim to an upgrade of light control technologies [7 -8]. In other cases, the scope is searching for a 37 reliable evaluation system of real energy savings [9]. 38 An interesting review on lightin g control technologies is presented by Haq et al. [10]. Yu and Su [11] presented a 39 literature review in which they state that, amongst all lighting control systems, the ones more commonly employed are 40 the high frequency dimming control and the on -off contr ol; the choice of the control system deeply influences the 41 energy saving potential. Salata et al. [12] discussed a case study of a classroom of an academic building. Results 42 obtainable by considering the interplay between natural and artificial light are h ighlighted. A new lighting system is 43 proposed, able to manage the automatic partialization of motorized indoor roller blinds and the presence of occupants in 44 the room. 45 Energy saving is well discussed in literature. The energy saving amount can vary on mont hly and seasonal basis, as 46 assessed in [13]. In the paper, monthly savings vary from 20% in December to 47% in June and July. Energy saving of 47 21% in winter season increases to 45% in summer. On seasonal basis, savings differ according to weather condition s. 48 The overall annual energy saving achievable by adopting a daylight responsive control system is up to 31% for climate 49 conditions similar to the ones of Istanbul. In the paper by Martirano [14], the consumption relative to two adjacent 50 classrooms has bee n evaluated. In particular, the light control system foreseen for the two rooms is conceived to meet 51 the needs required by scheduling, luminance control, occupancy, daylighting and zoning. The evaluations are carried 52 out using the LENI (lighting energy num eric indicator) methodology. According to the author, the energy saving 53 achievable by adopting action in power reduction (like, for instance, more efficient lamp) is almost the 20%, while the 54 savings obtainable by using lighting control systems (like occup ancy sensors) depend on the control mode (dimming or 55 switching) and swing between 35% and 42%. By implementing control systems and efficient equipment, the energy 56 saving accounts for 54%. The work of Bardhan and Debnath [15] deals with the analysis of the energy saving potential 57 of a residential building when, as daylight performance parameter, the Useful Daylight Illuminance (UDI) is 58 considered. It turns out that energy saving potential depends on the orientation and on the window -to-wall (WWR) 59 ratio. The maximum energy saving for the analyzed building, equal to 26%, is achieved with a south -east orientation of 60 the functional space and WWR of 20%. In the work of Choi et al . [16], two methodologies of predicting the lighting 61 power savings are compared. One ( Method A) refers to the relationship between lighting energy and illuminance. These 62 two parameters, which can be considered as input and output of the system respectively, are also evaluated according to 63 3 the dimming ratio of the luminaire. The second appro ach (Method B) consists in taking into account the indirect 64 illuminance in the evaluations carried out through Method A. Results obtained via method A and B are then compared 65 to the lighting energy saving experimentally measured. In reference [17], the ene rgy and power consumption of three 66 identical classrooms equipped with different dimming systems have been compared. An open -loop system was installed 67 in a classroom, whilst in the other two there were two different closed -loop systems (with individual dayl ight sensor per 68 luminaire or centrally positioned sensor). Results gathered during 12 months, during which the rooms were occupied for 69 teaching purposes, show ed that the daylight control system with open -loop system lead to a 46% lighting energy saving. 70 This value is higher than the saving due to closed -loop system, which yielded to 34% and 18% energy saving, the latter 71 being recorded for the room with central positioned sensor. 72 Detailed studies on lighting control for daylighting and occupancy adaptation s how the different approaches 73 adoptable. A work proposed by Peruffo et al. [18] discussed a wireless mesh networked lighting system with multiple 74 sensors equipped with a central controller, evaluated through a simulation performed with DIALux. In this study , it is 75 underlined that wireless connections are simpler than wired ones, and they are useful for lighting controls retrofitting. 76 Aghemo et al. [6] presented an experimental analysis given by the installation of custom -designed building automation 77 and cont rol systems for lighting and air conditioning on 11 offices in Turin (Italy). Lighting control is realized with 78 digital dimming ballast (DALI protocol), while system nodes communicate with LonWorks protocol. Results show an 79 energy saving variable from 17% to 32%, considering both the annual electric consumption and the parasitic energy 80 consumption, due to sensors and controllers. A study conducted by Xu et al. [19] presented an energy performance 81 evaluation for lighting systems with 8 different control stra tegies. The employed technology is based on commercial 82 sensors (OSRAM LS/PD MULTI 3) and the data gathering core is a PLC (programmable logic controller). Results 83 show that the employment of a generic lighting control system allows energy savings of the or der of 50%. The 84 combination of task lighting and dimming allows achieving energy saving up to 59%, still guaranteeing comfort for 85 occupants. Doulos et al. [5] presented a study in which they quantify energy savings among 18 different EDBs 86 (electronic dimmi ng ballasts), identifying the relationship between light output ratio and control voltage, consumed 87 power and control voltage, power factor and control voltage and between consumed power and light output ratio. 88 Simulation results of an office building reve al significant differences in energy saving due to tested ballasts. Rossi et al. 89 [20] discussed a comparison between two lighting control scenarios in an open office lighting model: the first scenario 90 considered a daylight and occupancy adaptation based on pre-specified illumination targets, whereas the second 91 scenario evaluated via simulations the performance of a lighting control based additionally on user control requests. In 92 the work of Caicedo et al. [21], a lighting system with light sensors co -locate d at light source was considered, in order 93 4 to assess by means of simulations how a central controller can minimize power consumption maintaining a minimum 94 average illuminance level on the workspace plane. Prior -information for sensor calibration step were also provided. 95 In this work, different types of control systems, the development of the related technologies, the savings obtainable 96 from their application and factors affecting their performance are debated. Moreover, trend of developments on lighting 97 control and possible future advancements are discussed. The next part of the paper is organized as follows. In Section 2 98 the objectives of the work are presented. Section 3 reports the novel lighting control system and the simulated case 99 study. Section 4 deal s with obtained results. Finally, in Section 5 conclusions are given. 100 2. Objectives 101 Lighting control systems, although allowing relevant reduction of energy consumption, are often affected by design 102 and installation complexity, high costs, difficulties in evaluating real energy benefits and technical management 103 problems [5 -6, 22]. These r easons determine their smaller spread compared to the possible expectations. As stated in 104 [23], the spread of lighting control system is wider in new buildings than in old ones. This point of view negatively 105 influences results on overall energy savings obtainable by the lighting sector. In fact, according to Pellegrino et al. [24], 106 based on the small amount of new buildin gs realized in developed Countries, the energy saving potential can be realized 107 only with the retrofitting of the existing building stock. 108 For these reasons, the main objective of the present work is the proposal of a novel automatic daylight control 109 syste m and occupancy sensing, employable with different lamp typologies; it is conceived especially for application on 110 existing buildings, thanks to its extreme ease of installation, wireless communication capability and to low investment 111 cost. The idea of crea ting a new control system usable with any lamps aims at minimizing the negative aspects that 112 usually characterize the installation of a lighting control system in existing buildings, i.e. high investment costs and 113 possible modifications of lighting fixture , with the attempt of maximizing the diffusion of such systems. The proposed 114 system differs from available literary solutions [25 -28] and available commercial products because it allows to define a 115 lighting control systems making use of any type of lamps, regardless of their dimmable and non -dimmable 116 characteristic, also including the conventional light bulbs such as halogen and fluorescent lamps, beyond of LED ones. 117 Up to now, all literary contributions that have been presented try to manipulate the driver circuit inside the LED lamp in 118 order to make it compatible with external dimmers, so they appear as theoretical case studies rather than suitable for 119 practical applications or large scale installations. On the opposite, commercial solutions up to now rely on the 120 availability of very expensive dimmable LEDs or potentiometers, usually manual, that can be installed to dim 121 traditional lamps and that are not able to work with non dimmable LEDs, since they are fabricated with a different 122 5 technology process. So, the proposed system represents a unified solution for an efficient and automatic lighting 123 control. 124 System performances of the proposed system were analyzed through laboratory tests, in order to evaluate its 125 sensitivity by defining different illuminance le vels for fluorescent and LED lamps, dimmable and non -dimmable. 126 At the end of the experimental laboratory phase, and after demonstrating the applicability of the system to real cases, 127 being not possible to install the proposed system in public environments, since it is at prototypical stage, the feasibility 128 of the system has been verified at simulation level. The case study is a classroom of the Faculty of Engineering of the 129 University of L’Aquila, in central Italy. 130 At this stage, the aim is to carry out the energy and economic analysis of the performances of the lighting plant, 131 considering different technologies and control strategies: fluorescent, dimmable and non -dimmable LED lamps, and 132 with occupancy and daylighting adaptation provided by the proposed sys tem. The economic analysis was deepened by 133 comparing the system proposed in this paper, employable also with non -dimmable LED lamps, with a commercial 134 lighting control system usually employable with only dimmable LED lamps. 135 The case study was analyzed via simulation carried out with Relux software, on a calibrated model, by considering 136 both solely daylight and solely artificial light. 137 Therefore, the main research objectives can be summarized as follows: 138 1. design and description of a new universal daylight and occupancy control system employable with any 139 lamps, based on microcontrollers, actuators and a wireless sensor network; 140 2. prove of the applicability of the system to real cases with different lamps (fluorescent, dimmable and non 141 dimmable LEDs); 142 3. application of the system to a case study, through the use of a validated model, for energy and economic 143 analyses of the results. 144 3. Methodology 145 In this section, the methodology employed for achieving the goals of this paper is discussed. 146 3.1 Lighting control system 147 Before describing the architecture of the proposed system, it is necessary to verify the state of the art, concerning 148 how dimming is commonly performed. Generally speaking, the dimmer is a power electronic device used for lighting 149 control. It can be usefu l in several applications as for the industrial and residential lighting control. Among the 150 6 advantages for consumers to use dimmers there is the economic convenience with respect to other solutions and energy 151 conservation. 152 Nowadays, phase -controlled dimme rs based on a TRIAC (triode for alternating current) (or two thyristors) can be 153 considered the more diffused for lighting control. In this scenario, several circuits have been developed and presented in 154 the literature by using forward and reverse phase con trolled approaches [29 -30] also wired or wireless remote 155 controlled. In particular, when the forward phase -controlled dimmers are considered, the TRIAC is triggered into 156 conduction at some point during the AC half -cycle and continues to conduct until it se lf-commutates at the end of the 157 half-cycle [31 -34]. On the other hand, when the reverse phase -controlled dimmers are considered, the component is 158 moved into conduction immediately after the zero crossing commutating off only in a chosen point during the ha lf-cycle 159 of the AC [35, 36]. 160 Currently, the most popular dimmer in the market is the TRIAC phase control dimmer [31 -33]. The TRIAC success 161 reason is that it can be triggered at any time of the sinusoidal voltage and can be kept in conduction state until r eaching 162 0 line voltage, so allowing the lamp to be dimmed in the range from 1% to 100%; however, it does not work for a kind 163 of lamps. Nowadays, residential dimmers are designed to meet the needs of homeowners and architects in both style 164 and function. Com mercial companies offer a complete line of dimmers and dimming systems that are designed to meet 165 the requirements of architects and specifiers of commercial space such as hotels, restaurants, offices and warehouses. 166 This is true for both new and existing i nstallations where replacing standard switches with dimmers and using dimmable 167 LED helps saving energy and the associated utility costs. The actual problem is the absence of a so called real 168 “universal” dimmer that allows for a fluid "dimming" of every con ventional light bulb such as halogen lamps, 169 fluorescent lamps and even dimmable and non -dimmable LEDs. While energy reduction is an important aspect, paying 170 attention to the visual comfort needs of occupant users in terms of illuminance requirements is als o important. This 171 means that the dimming levels of each luminaire are also to be determined by corresponding electronic remote or 172 internal to the lamps controllers related to physical aspects such that the total artificial light output contribution, in 173 combination with daylight contribution also related to the human presence. As far as we are concerned, there are not 174 commercial devices or systems that can be used in both novel and existing scenarios for building automation and 175 lighting control. 176 3.1.1 Contro l system architecture 177 The proposed lighting control system has been conceived as a combined architecture embedding sensing elements 178 and actuators that are managed by a dedicated control unit with a microcontroller. The system provides the optimum 179 7 light level in any environments by means of an automatic control system able to define the necessary lighting conditions 180 with respect to both natural lighting and occupancy conditions. 181 The lighting control system that has been designed allows the dimming of any lamps installed in the local power 182 grid network, without requiring changes in the lamp type currently in use, in the ceiling lights or even a dedicated 183 electrical system. A block scheme representation of the lighting control device is provided in Fi g. 1. It can be installed 184 directly nearby the considered lamp in series connection and it does not require any added connection since it is able to 185 activate the by -directional communication with the master control unit on a 2.4 GHz wireless protocol, as sh own in Fig. 186 2. The system performs a continuous monitoring of the lighting conditions if there are occupants; conversely, if the 187 occupancy sensor does not sense anyone, the lamp is turned off after a fixed delay time that can be defined by the user. 188 In thi s condition, the occupancy sensor continues to monitor the environment for further presences within its field of 189 view and the logic unit for manually lighting by incoming users. 190 Fig. 1. The proposed lighting control system. 191 Fig. 2. The lighting co ntrol network architecture. 192 Lighting control deviceAC 110-220V Lamp Lighting control deviceAC 110-220V Lamp Lighting control deviceAC 110-220V LampLighting control deviceAC 110-220V Lamp Lighting control deviceAC 110-220V Lamp Lighting control deviceAC 110-220V LampControl Unit 8 When lighting is necessary, as revealed by any control device, the logic unit that embeds a microcontroller defines 193 suitable lighting conditions considering the natural lighting level in the same environment by means of the daylight 194 sensor and the desired, pre -defined, target value. The desired brightness is achieved directly acting on the driver stage 195 and actuator connected to the considered lamp and the lighting starts from very low level till reach ing the necessary 196 target value in about 1 second. The control method is based on the phase synchronization of the system with the power 197 grid by means of a zero -crossing detection approach. Once the proposed control system is synchronized with the AC 198 network s ignal, the dimming capability is achieved by cutting the amplitude of the sinusoidal voltage incoming to the 199 lamp after a pre -defined time delay. The logic unit is programmed with a pre -calibrated relationship for each lamp type 200 between the desired illumin ance and the necessary time delay to achieve it. This means that only when the lamp is used 201 at 100% of its brightness capability it is biased with fully sinusoidal voltages, otherwise the maximum value is set at 202 lower value by the proposed algorithm that l imits the amplitude of the biasing signal, so obtaining a lower RMS (root 203 mean square) power level and lower light. In Fig. 3, some examples are provided; the picture shows different biasing 204 signals for the lamp that determine different emitted light, acco rdingly. 205 Fig. 3. Example of application: measured control signals that allow obtaining different lighting levels. It is important to note that directly acting on the time domain, by cutting the voltage amplitude at the desired time 206 instant, it is poss ible to achieve a continuous tuning system with performance not worse with respect to commercial 207 dimmed lamps, as shown in the following. In this way, the brightness capability is fully controlled and it can be 208 changed almost in continuous wave in the full range. Thanks to suitable circuitry choices, the proposed solution is 209 robust also with respect to flickering phenomena due to harmonic distortions. This capability is ensured by using trap 210 filters and frequency -selective low -impedance paths that avoid the injection of high -order harmonic components into 211 the lamp. The same robustness is achieved also towards the whole lights grid, since the voltage clipping technique here 212 adopted does not propagate distortions to the other lighting elements, because the har monic components are filtered by 213 9 the driver stage. So the harmonic content generated by the system is not greater of those provided by commercial 214 dimmer or dimming circuits integrated in dimmable LED s; anyway, although any lamps can be sensitive also to th e 215 provided low harmonics levels, a common EMI (electromagnetic interference) filter may be introduced in the electrical 216 grid to completely solve the problem. In addition, since in this approach the lamp is defined as a generic complex 217 impedance, usually mo deled with a resistor and an inductor in series, the lamp type changes do not affect the overall 218 capability and characteristics of the control system. The only action which is required in this case is choosing the proper 219 configuration algorithm for the mic rocontroller. 220 A remarkable additional feature relies in the characteristics of the driver stage. Since the system directly works on 221 the AC 110 -220 V 50 -60 Hz power grid network, while the logic unit usually requires lower voltage values, the driver 222 stage in Fig. 1 is conceived performing also a decoupling between the high and low voltage networks by means of an 223 electro -optic transducer. An optic coupler is used between the logic control unit and the dimming network and actuator 224 so providing a complete isol ation of the sensing and control elements with respect to the electric grid. This is a key 225 feature since it makes the provided system not invasive and at the same time shielded from possible network 226 disturbances and overload , that may damage the control sy stem. More in detail, the delay time defined by the logic unit 227 to obtain the desired brightness level is managed by the microcontroller defining a gate, digital, control signal which 228 excites the optic transmitter. The pulsed light activates the photosensor inside the optic coupler so determining the 229 current flow on the dimming network by switching on and off a power MOS (metal oxide semiconductor) transistor 230 directly connected to the high voltage network. It is notable to consider that the use of a MOS tran sistor to drive the 231 current flow is an additional key point of the proposed system. In fact, in despite of a classical TRIAC that properly 232 works on a resistive load (i.e. a fluorescent lamp which can be considered as a R -L equivalent network), a power MOS 233 transistor, controlled by means of the gate voltage, ensures good operations for any load, that means for any kind of 234 lamps. This strategy has the further advantage to transfer in a high voltage system the control capability and sensitivity 235 proper of a mic ro electronic system, with unmistakable advantages in term s of accuracy and power handling. In Fig. 4 236 an example is given, reporting both the digital timing signals and the current profile flowing into a non dimmable LED 237 lamp. 238 10 Fig. 4. Example of application: timing signal of the provided control system. Finally, at system level, each control system installed nearby a lamp is able to communicate by means of a 2.4 GHz 239 wireless communication system with a high -level control unit (Fig. 2) which embeds a microcontroller and a wireless 240 transmitter and it can be considered as the local user interface. It allows setting the desired lighting target to provide in 241 the considered environment, to set the proper calibration algorithm with respect to the lamps currently in use and to 242 define more complex lighting monitoring system. The latter means that the sensing elements can be arranged also in 243 different positions with respect to the lamps locations considering the more suitable monitoring condition s for the local 244 environment. In this case, the control unit is in charge to determine the overall lighting and occupancy conditions and to 245 define the operative instruction for each logic unit, accordingly. The sensing elements have an internal battery that , with 246 a normal use, allows about 1 year operations; anyway, if they are installed together with the logic unit and close to each 247 lamp, their DC power supply can be directly obtain ed from the logic unit that define the necessary DC bias voltage from 248 the el ectrical grid, by using an AC/DC switched mode power supply (SMPS), useful for reducing the board dimensions. 249 It is important to notice that the dimming of the lamps has a minimal influence on the total power consumption of 250 the lighting system. The contro l unit has a typical power consumption of 3 W and a single unit is needed for each 251 scenario, while the complete lighting control device used nearby each lamp requires about 0.5 W when active in 252 receiver mode and 1 W when active in transmission mode. Anyway , some of the on board sensors and circuits are in 253 sleep mode when no significant events are detected and this allows to reduce the operation time and so the effective 254 power consumption. In additions, as already said, also a lower number of sensing element s with respect to that of the 255 logic units and lamps can be used, since sensors can be arranged also in different positions with respect to the lamps 256 locations; this allows to further decrease the real power consumption of the proposed system. Anyway, in th e worst 257 case, that consists of using a complete lighting control system for each lamp, the total power consumption required by 258 the electronic system is much more lower of that supplied to the lamps in a typical scenario. 259 11 In Fig. 5, photographs of the light ing control system are shown. It is evident from the implemented components that 260 the current system dimensions can be reduced, for a commercial device, achieving a very low occupation area making it 261 easily installable. 262 (b) (a) (c) Fig. 5. Photograph of the lighting control system prototype. (a) Driver stage, actuator and control unit . (b) Standalone photosensor . (c) Standalone occupancy sensor. 3.1.2 Experimental analys es 263 Experimental analyses, carried out in the laboratory, have the purpose of: 264  verifying feasibility and applicability of the proposed lighting control system for different lamp typologies, both 265 dimmable and non -dimmable; 266  proving that the proposed control system can dim also non -dimmable lamps from 100% to 10%, without typical 267 inconveniences, like flicker. 268 For all the experimental tests, a box was employed, in order to measure the illuminance values provided by the 269 lamps (Fig. 6). The lamp was fixed in the upper part of the box, while the illuminance measuring probe was placed at 270 the bottom. Before carrying out the experimental tests, the illuminance zero value inside the box has been verified, in 271 order to obtain measurem ents with artificial light only. Experimental tests were realized with voltage and frequency 272 values equal to 220 V and 50 Hz, respectively. Moreover, all measured values were recorded after electrical stabilities 273 were provided. 274 12 Fig. 6. Box for experime ntal tests. All the values are expressed in [m]. For the experimental phase, the proposed lighting control system has been applied to three different lamps: 275 fluorescent, dimmable LED and non -dimmable LED (Table 1). 276 Table 1 Technical specification of fluorescent and LED lamps , for laboratory tests . Physical quantity Fluorescent lamp Non-dimmable LED lamp Dimmable LED lamp Correlated color temperature[K] 4,300 2,700 2,700 Luminous flux [lm] 1,000 470 810 Power [W] 20.0 5.5 10.0 Luminous efficacy [lm/W] 53.3 85.5 81.0 For each lamp, different dimming levels were imposed, varying illuminance from 100% to 10%, considering step 277 size of 10%. Illuminance values have been measured by a luxmeter, whose characteristics are reported in Table 2. For 278 each di mming level, the required power consumption has been evaluated by measuring voltage and current levels by 279 means of an oscilloscope. 280 Table 2 Metrological properties of the luxmeter. Measuring range [lx] Accuracy Luxmeter 0.1 – 200,000 ± 3% ≤ 20,000 lx ± 5% > 20,000 lx 3.2 Case study 281 The analysis of a case study has the aim of evaluating the effects derived from the installation of the proposed 282 lighting control system, analyzing how technologies and control strategies influence the energy and economic 283 indicators. Furthermore, to better understand the economic feasibility of the proposed system, it has been compared to a 284 commercial system, from the economical point of view. 285 Since education buildings represent a relevant research area for those w ho are involved in building design [37], a 286 classroom of the structure which hosts the Faculty of Engineering of the University of L’Aquila (IT) was chosen. The 287 13 Faculty is made up by three wings (A, B and C of Fig. 7) and by a historical building, currently under reconstruction 288 after the earthquake that hit the city of L’Aquila in 2009. 289 Structures of wing A and B have three floors, hosting classrooms, offices and laboratories. Wing C hosts the lecture 290 hall and the library. The overall area accounts for 12,78 0.0 m2. 291 Fig. 7. Overall view of the Faculty of Engineering of University of L’Aquila. 3.2.1 Case study description 292 The case study analyzed is a classroom, called B 0.9, at the ground floor of wing B which is East -West oriented. 293 Classroom geometry is regular: main dimensions are equal to 6.98 m x 8.45 m, the net area is 59.00 m2 and the height is 294 3.70 m (Fig. 8). The classroom has a glazed west -facing wall, having three windows, whose dimensions are equal to 295 1.70 m x1.90 m and a French window with dime nsions of 1.90 m x 2.90 m. 296 As a whole, the net transparent glazed area is 15.2 m2. The west -wall surface (including window frames and 297 transparent area) is equal to 25.8 m2. Therefore, the window -to-wall ratio (WWR), given by the ratio between net 298 glazed ar ea and wall area, equals 0.59. The Window -to-Floor -Ratio (WFR), calculated as the ratio between the glazed 299 area and the net area of the room, is 0.26. 300 Being the wing B quite detached (Fig. 7), the classroom does not have external obstructions, except for s hading due 301 to a horizontal overhang 1.10 m width that has been modeled. In the lecture room, there are 27 seats, arranged on three 302 rows having 9 seats each. 303 14 Fig. 8. Classroom and sensors layout: purple squares for occupancy sensors, red circles for daylight sensors, and control unit indicated with letter (C). All the values are expressed in [m]. In the classroom, there are 9 luminaires with fluorescent lamps (type O SRAM Lumilux Cool White) of 36 W each 304 (yellow rectangles of Fig. 8), mounted on the ceiling, with an overall installed power of 324 W. Luminaires have a 305 paraboloid optic with mirror -reflective surface with high reflection. Manually controllable internal ve rtical blinds allow 306 the reduction of natural light in the room , but they are not considered in this study . According to standard EN 12464 -1 307 [38], reference parameters for educational buildings are: 308  average maintained illuminance: Em = 500 lx; 309  uniformity on working plane: U ≥ 0.6; 310  unified glare rating: UGR ≤ 19; 311  color rendering index: CRI ≥ 80. 312 3.2.2 Model description and calibration 313 Possible energy saving estimation due to lighting control system is a complex matter, because of the high number of 314 variables and their interplay [22]. For this reason, simulation tools are very useful instruments in daylighting design 315 process [39]. Indeed, according to Reinhart and Fitz [37] about the 80% of works concerning daylight are carried out by 316 using software. 317 The case study was modeled with the Relux software, developed by RELUX Informatik AG in Switzerland. This 318 software is a tool for lighting simulation, easy to use; it provides reliable results, both for artificial lighting and for 319 daylighting simulations. In fact, according to a study, which is part of IEA -SHC Task 31, by Maamari et al. [40], where 320 the validation of two software in 32 scenarios is presented, Relux has showed better results than the analytical 321 assessment. Shailesh and Raikar [41] presented an analysi s of the interaction between natural and artificial light in a 322 15 commercial office building in India, by means of computer simulations using Relux software, in order to demonstrate 323 the potential of energy saving by adopting daylighting harvesting solutions. Yu et al. [42] discussed an application of 324 Relux simulation to investigate energy saving potential from daylighting in a new educational building in UK. The last 325 part of the work shows the comparison of the annual energy saving by various estimation method s, showing the reliable 326 results gathered from Relux. 327 The model of the classroom investigated in this work was realized by accurately reproducing the real room layout 328 with its furniture and blackboard. For this case study, we have considered the following sensors configuration: 9 329 lighting control devices, one for each lamp, 4 separated occupancy sensors to cover all the floor area, and one control 330 unit (Fig. 9 a). In the model, the following reflectances were set: ceiling with white plaster (71%), walls with white 331 plaster (76%), floor with grey ceramic tiles (11%). 332 The measuring plane was positioned 0.75 m far from the floor, analogously to the real height of the desk, which is 333 considered as workplane. 334 The Relux model of the classroom was calibrated both in daylight condition and in artificial lighting. Lighting 335 results with natural light were compared to those measured in field. Measurements were carried out on June 9th, 2017, 336 under clear sky conditions. The sim ulation was performed by considering CIE (International Commission on 337 Illumination) Clear Sky Model conditions. Data of natural light were measured with a luxmeter, whose technical 338 characteristics are reported in Table 2. 339 The virtual measuring plane was retrieved according to the real desk layout in the room. Therefore, 5 evenly spaced 340 measuring points were selected for each of the three desk rows, as shown in Fig. 9b. 341 For each measuring point, 9 acquisitions were carried out, from 9.00 am to 5 .00 pm, with a sampling rate of one 342 hour, to evaluate how natural light irradiates in the room along time. The measuring probe was positioned on the desk, 343 considered as workplane, which is 0.75 m high, at a minimum distance of 1.30 m from vertical walls, to g ain the global 344 horizontal illuminance. By comparing simulated and measured data, the model was deemed calibrated, as the deviation 345 (∆ (%)) was within ± 20% (Eq. 1). 346 ∆(%)= (M−S M)∗100 (1) where (M) stands for the measured value, and (S) for the simulated one. 347 16 (a) (b) Fig. 9. Room layout. (a) Positioning of: luminaries (yellow rectangle), occupancy sensors (purple square), photosensors (red circle) and control unit (letter C). (b) Data acquisition grid: front , middle and rear labels refer to the relative positioning of the desk rows to the professor desk. After calibrating the model by considering only daylight, a further calibration was performed in solely artificial 348 light. In this case, measurements were performed during nighttime, with roller blinds completely shut down, to avoid 349 the possible interference of external artificial lights. 350 Equipment and measuring grid were the same adopted for the calibration in natural light. Before performing 351 measurements with lamps switched on, it has been proved that the measured illuminance was null. For each measuring 352 point, 7 acquisitions were carried out, and the average of measured values of each point was then considered. 353 A picture of the room, and its 3D model under natural light, are proposed in Fig. 10. Under overcast sky conditions, 354 the mean daylight factor of the classroom is equal to 2.64 %, and it is higher where the light enters. 355 (a) (b) Fig. 10. Case study. (a) Picture. (b) 3D model render with lamps switched off. 17 Model calibration with natural light showed good results, for all measuring points and for all time steps. Fig. 11 356 shows the comparison between measured and simulated results, for each point and versus time, highlighting the natural 357 light penetration in the room. 358 (a) (b) (c) Fig. 11. Comparison between simulated (dark colors) and measured (light colors) illuminance values with natural light. (a) Front row. (b) Middle row. (c) Rear row. Percentage deviation for each acquisition is reported in Table 3. Obtained results show t hat simulation results (S) are 359 near to measured (M), with percentage deviation ( Δ(%)) within the range ± 20%. 360 Table 3 Simulated and measured results, with their percentage deviation – natural light case. Point 1 Point 2 Point 3 Point 4 Point 5 Ma Sb Δ(%) M S Δ(%) M S Δ(%) M S Δ(%) M S Δ(%) 9.00 Front 221 256 -15.8 185 213 -15.1 144 156 -8.3 114 125 -9.6 112 113 -0.9 Middle 218 229 -5.0 181 215 -18.8 138 163 -18.1 119 138 -16.0 110 122 -10.9 Rear 223 230 -3.1 181 217 -19.9 137 164 -19.7 119 142 -19.3 107 127 -18.7 10.00 Front 230 243 -5.7 186 213 -14.5 151 162 -7.3 139 129 7.2 129 116 10.1 Middle 226 260 -15.0 187 212 -13.4 150 163 -8.7 140 138 1.4 129 123 4.7 Rear 228 224 1.8 184 219 -19.0 146 174 -19.2 132 144 -9.1 121 123 -1.7 11.00 Front 240 240 0.0 207 227 -9.7 168 161 4.2 147 131 10.9 136 119 12.5 Middle 240 263 -9.6 203 221 -8.9 167 169 -1.2 150 137 8.7 138 120 13.0 Rear 252 216 14.3 206 222 -7.8 167 172 -3.0 146 138 5.5 132 123 6.8 12.00 Front 258 213 17.4 214 217 -1.4 173 163 5.8 152 130 14.5 142 116 18.3 Middle 266 270 -1.5 212 213 -0.5 170 163 4.1 154 139 9.7 142 124 12.7 Rear 269 238 11.5 215 217 -0.9 170 167 1.8 150 143 4.7 136 127 6.6 13.00 Front 296 255 13.9 237 231 2.5 185 169 8.6 160 130 18.8 146 117 19.9 Middle 304 276 9.2 239 238 0.4 187 177 5.3 160 141 11.9 146 122 16.4 Rear 300 257 14.3 235 239 -1.7 186 183 1.6 160 145 9.4 141 126 10.6 14.00 Front 326 265 18.7 260 241 7.3 198 174 12.1 169 140 17.2 151 128 15.2 Middle 337 287 14.8 249 237 4.8 196 189 3.6 168 150 10.7 149 129 13.4 Rear 334 292 12.6 254 251 1.2 184 188 -2.2 162 156 3.7 143 133 7.0 15.00 Front 763 867 -13.6 586 607 -3.6 437 439 -0.5 337 351 -4.2 277 311 -12.3 Middle 735 858 -16.7 567 624 -10.1 422 446 -5.7 334 360 -7.8 271 320 -18.1 18 Rear 718 861 -19.9 547 613 -12.1 414 452 -9.2 328 363 -10.7 276 324 -17.4 Front 1048 1103 -5.2 801 732 8.6 576 525 8.9 428 394 7.9 343 329 4.1 16.00 Middle 1060 1076 -1.5 776 768 1.0 544 524 3.7 417 397 4.8 332 334 -0.6 Rear 1001 1056 -5.5 736 761 -3.4 524 515 1.7 400 392 2.0 316 333 -5.4 Front 1193 1405 -17.8 895 943 -5.4 650 622 4.3 489 447 8.6 384 360 6.3 17.00 Middle 1159 1356 -17.0 844 937 -11.0 603 612 -1.5 473 444 6.1 372 359 3.5 Rear 1126 1303 -15.7 821 870 -6.0 586 583 0.5 453 428 5.5 355 351 1.1 aM: measured values [lx]; bS: simulated values [lx]. N.B.: maximum and minimum percentage deviations (∆(%)) of each time step are in bold. In the case of solely artificial light, illuminance results from simulation agree with those gathered from multiple in 361 field measurements. With respect to the natural light case, values are more uneven, mainly due to lamps ’ different 362 installation time, that implies their different deteriorations [32]. In fa ct, to take into account the different performance 363 decays due to different installation times, it has been necessary to tune the Maintenance Factor (MF) on the model. The 364 obtained MF was 0.6. The comparison between measured and simulated results is propose d in Table 4 and plotted in 365 Fig. 12. 366 Table 4 Simulated and measured results, with their percentage deviation – artificial light case. Point 1 Point 2 Point 3 Point 4 Point 5 Ma Sb Δ(%) M S Δ(%) M S Δ(%) M S Δ(%) M S Δ(%) Front 187 207 10.8 204 225 10.3 208 210 11.1 197 210 6.7 165 166 0.8 Middle 299 264 -11.6 301 288 -4.4 294 268 0.5 288 268 -6.8 234 211 -9.8 Rear 247 265 7.4 271 285 5.2 276 265 5.9 259 265 2.4 213 207 -2.8 aM: measured values [lx]; bS: simulated values [lx]. N.B.: maximum and minimum percentage deviations (∆(%)) of each time step are in bold. 367 Fig. 12. Comparison between simulated (dark colors) and measured (light colors) illuminance values with artificial light. Red, green and blue refer respectively to front, middle and rear row. 19 Measured illuminance values, and consequently the values simulated thro ugh the calibrated model, are always lower 368 than the minimum value required by standard EN 12464 -1 [38] and equal to 500 lx (Fig. 13). These low values of 369 illuminance are due to the reduced performance of the lamps installed in the academic classroom, cause d by the natural 370 deterioration of the lamps. 371 According to [16], illuminance level not fulfilling target value implies that measured and predicted energy savings 372 cannot be compared. Therefore, before carrying out energy and economic analyses, on the calibra ted model, it has been 373 retrieved the lighting power necessary to obtain the target value (500 lx), employing the fluorescent lamp type described 374 in Table 5. The increase of mean illuminance on workplane determines the increase of installed power from 324 W to 375 648 W. 376 (a) (b) Fig. 13. Illuminance distribution for artificial lighting. (a) 2D contour plot. (b) Render with lamps switched on. Table 5 Technical specification of fluorescent and LED lamps. Fluorescent lamp Non-dimmable LED lamp Dimmable LED lamp Physical quantity LUMILUX® Cool White MASTER LEDtube Ultra Output LR12840M – 18W Lamp lenght [mm] 1,200.0 1,200.0 1,200.0 Correlated color temperature [K] 4,000 4,000 4,000 Color rendering index > 80 > 83 > 83 Life time [h] 18,000 50,000 50,000 Luminous flux [lm] 3,350 2,500 2,700 Power [W] 36 18 18 Luminous efficacy [lm/W] 93.1 139.0 150.0 377 3.3 Lighting scenarios 378 20 The energy analysis was carried out to quantify consumption variations due to the application of the lighting control 379 system proposed in this paper. Different scenarios were considered for the case study. The reference case refers to the 380 actual lighting sy stem installed, made up of fluorescent lamp without lighting control system. Case 1 concerns the 381 substitution of fluorescent lamps with non -dimmable LED lamps, maintaining the same illuminance value on the 382 workplane. Case 2 and 3 are related to the case 1 with the adding of, respectively, occupancy and daylight controls. The 383 last one, case 4, evaluates the LED lighting system equipped with both occupancy and daylight control s. Lighting 384 scenarios are summarized in Table 6. 385 In the model, all sensors of the lighting control system were placed in the ceiling (Fig. 9a), deeming this positioning 386 the best adoptable [43]. 387 Table 6 Lighting scenarios. Lamp type Control system Fluorescent lamps LED lamps Occupancy control Daylight control Reference Case  Case 1  Case 2   Case 3   Case 4    Characteristics of fluorescent lamps currently installed in the room and of LED lamps chosen for the energy retrofit 388 are reported in Table 5. 389 3.4 Energy and economic analysis 390 The energy analysis was performed following european standard EN 15193 [44], applied through the ReluxEnergy 391 module of Relux. Main evaluated parameters are annual energy consumption (W L) in [kWh/y] (Eq. (2)) and LENI 392 [kWh/m2y] (Eq. (3)). 393 𝑊𝐿= (PN FC) ((tDFOFD)+ (tNFO)) 1000 (2) In Eq. (2), (P N) is the installed electric power for artificial lighting [W], (F C) is the constant illuminance factor, (t D) 394 is the annual operating hours during the daylight time [h/y], (F O) is the occupancy dependency factor, (F D) is daylight 395 dependency factor, and (t N) the annual operating hours during non -daylight time [h/y]. 396 𝐿𝐸𝑁𝐼 = 𝑊𝐿 𝐴 (3) 21 LENI is defined in Eq. (3) as the ratio between annual energy consumption and the total floor area (A). 397 Input values for ReluxEnergy mod ule are reported in Table 7. 398 Table 7 Input values for ReluxEnergy setup. Parameter Setting Location L’Aquila (42°) Building type Academic building Annual daylight time usage (t D) 1,800 h/y Annual non -daylight time usage (t N) 200 h/y Mantained illuminance 500 lx Absence factor 0.25 (classroom) Double glazed facade Default values Horizontal overhang angle 36.0° (French window) 47.7° (windows) Based on energy consumption, for the considered scenarios, the evaluation of CO 2 emissions has been performed. 399 The emission factor employed is equal to 0.46 kgCO 2/kWh [45]. 400 The economic assessment of all scenarios was carried out by considering the main economic indexes: PBP (payback 401 period) and NPV (net present value). Both were evaluated considering base rate of 2% for 20 years (Eq. 4 and 5). Italian 402 electricity price for domestic consumers, equal to 0.21 €/kWh was considered [46]. 403 ∑𝐹𝑡 (1+𝑘)𝑡− 𝐹0𝑃𝐵𝑃 𝑡=1 =0 (4) 𝑁𝑃𝑉 = ∑𝐹𝑡 (1+𝑘)𝑡𝑛 𝑡=0 (5) where (F t) is the cash flow at time (t) in [€], (k) is the base rate, (n) is time span [years], and (F 0) is investment cost [€]. 404 The aim of the economic analyses is to prove that, thanks to the low cost of the proposed control system, to the 405 possibility of installing it even on non -dimm able LED, and to the ease of installation, payback time achievable are 406 lesser than analogous commercial systems. Table 8 summarizes technologies and control systems costs considered in 407 the economic analysis. It is important to notice that the prices relate d to the proposed lighting control system refer only 408 to the cost of electronic components that are necessary to develop the defined prototype system. For a complete budget 409 analysis, also the fabrication costs may be taken into account. Anyway, they have no t been reported since the 410 production costs decrease with the increasing demand of products. Therefore, the marginal cost of production of each 411 system is minimal, considering quantitative comparable to those of a commercial system, like that reported in Table 8. 412 In addition, the wiring costs for the commercial lighting control system and costs related to update of electric plant 413 were not considered. This choice implies the underestimation of the total cost of common lighting control systems and, 414 22 therefore, i n this paper their NPV and PBP are much more favorable than reality even neglecting the fabrication cost of 415 the proposed system. 416 Table 8 Technologies and control systems costs considered in the economic analysis. Proposed lighting control system Description Quantity Units Unit price [€] Total price [€] Non-dimmable LED Lamp ( MASTER LEDtube Ultra Output) 18 pieces 36.98 665.64 Lighting control device without sensors 9 pieces 9.00 81.00 Control unit 1 pieces 20.00 20.00 Occupancy sensor 4 pieces 1.00 4.00 Light sensor 9 pieces 5.00 45.00 TOTAL 815.64 Commercial lighting control system Description Quantity Units Unit price [€] Total price [€] Dimmable LED Lamp ( LR12840M – 18W) 18 pieces 56.28 1,013.04 Dimmer 9 pieces 31.98 287.82 Daylight and occupancy sensor (thePrema S360 DALI UP WH) 1 pieces 132.00 132.00 TOTAL 1,432.86 4. Results 417 4.1 Lighting control system 418 Results of the experimental tests highlight that the proposed control system allows to dim different light sources, 419 regardless of their dimmable characteristic. Dimming non dimmable lamps represents the novelty of the system that, 420 moreover, has the capability of avoiding some typical inconveniences that might raise, such as flicker. Indeed, dimming 421 different lamps with step of 10% of illuminance is always possible without flicker effects even when low illuminance 422 levels are reached. Fig. 14 shows the different illuminance values (variable from 100% to 10 %), obtained with different 423 dimming levels. The aim of the analyses is to show that, for each lamp considered for laboratory tests , illuminance can 424 be changed linearly, without flicker problems. In this way, the proposed system demonstrates its universal applicability, 425 allowing to hypothesize new scenarios for energy savi ngs, especially in existing buildings, where no changes on 426 luminaries and/or on electrical wiring are required. 427 23 Fig. 14. Illuminance values with different dimming levels obtained through the use of the proposed lighting control system for the different considered lamps (see Table 1). In terms of power consumption, Fig. 15 shows that the requirements in terms of absorbed p ower are dependent on 428 the provided illuminance and similar behavior is obtained for both dimmable and non -dimmable LED lamps, as well as 429 fluorescent lamp. Even if, in this last case, the power levels are higher, due to technology limitations. 430 Fig. 15 . Power consumption with different dimming levels. 4.3 Energy and economic assessments 431 Energy results of the case study, considering different scenarios, allow evaluating possible benefits obtainable with 432 the installation of different efficient technologies and the proposed control system. Monthly consumption and energy 433 savings obtainable with all the considered cases are plotted in Fig. 16. 434 24 Fig. 16 . Monthly energy consumption for all the considered cases. Table 9 shows a summary of energy r esults for the scenarios. Energy savings from the installation of occupancy 435 control (60.5%) and daylight control (61.4%) are quite near. The highest energy saving (69.5%) can be achieved by 436 combining both occupancy and daylight adaptation. 437 Table 9 Energy results of different scenarios. Scenario Energy results (according to EN 15193) Fluo. lamps Non-dimmable LED Lamps Occupancy control Daylight control Energy consumptiona (W L) [kWh/y] LENIb [kWh/m2y] Energy savings [%] Reference Case  1,137.0 19.3 N.A. Case 1  569.0 9.6 50.0 Case 2   449.0 7.6 60.5 Case 3   439.0 7.4 61.4 Case 4    346.0 5.9 69.6 a Calculated by Eq. (2), with (t D) equal to 1,800 h/y and (t N) equal to 200 h/y [44]. b Calculated by Eq. (3). Variations in terms of installed power, energy consumption, and CO 2 emissions are show n in (Fig. 17). Colored 438 circles indicate energy consumption (Y -axis) for the scenarios and their sizes are scaled to installed power (in [W]), 439 whose value is reported in the label. Fo r each case, related CO 2 emissions are displayed with orange circles and the 440 amount (in [kgCO 2/year]) is written in them. 441 25 Fig. 17. Energy consumption, power installed and CO 2 emissions of the scenarios. It is worth noting that all the cases considered for the retrofit have the same installed power, equal to 288 W, but 442 energy consumption varies as well as CO 2 emissions. Particularly, the best case, in terms of energy and environmental 443 aspects, is obtained by considering both occupancy and dayl ight sensors, since the energy consumption and CO 2 444 emissions are the lowest. Results from the separate installation of occupancy and daylight sensors (cases 2 and 3) are 445 near, showing that the two systems provide similar benefits. 446 Economical analysis h as been carried out by considering the Italian electricity price for domestic consumers [46]. 447 From the economic point of view, all scenarios have positive NPVs and PBPs ranging between 4 and 5 years, proving 448 the investments convenience. To appreciate the c onvenience of the proposed lighting control system, a further 449 comparison with a commercial control system was carried out (Table 10). 450 Table 10 Economic results. Scenario Economic results Non-dimmable LED Lamps Dimmable LED Lamps Occupancy control Daylight control PBP [years] NPV [€] Case 1  5 1,260 Case 2   4 1,660 Case 3   5 1,554 Case 4    5 1,862 Commercial control system    9 1,256 Cash flows and PBPs are show n in Fig. 18. 451 26 (a) (b) Fig. 18. Cash flow and PBP. (a) Comparison between the different control strategies, realized through the proposed system. (b) Comparison between proposed (solid line) and commercial systems (dashed line). It is worth noting that the best PBP is given by the installation of the proposed control system, considering only the 452 occupancy sensors, thanks to their low cost. Anyway, it is possible to observe that the proposed control system, 453 equipped with both occup ancy and daylight sensors, nearly halves the PBP with respect to the commercial system 454 (Table 10), reducing the payback time from 9 to 5 years. The reason of this difference is mainly due to the possibility of 455 installing the proposed system with non -dimmab le LED lamps. Moreover, the wireless communication protocol allows 456 an easier deployment of sensors that allow providing better economic results, minimizing wiring and plant adaptation. 457 To better understand economic benefits obtainable with the proposed con trol system, a further evaluation is proposed. 458 By considering the average value of electricity price in Europe, equal to 0,18 €/kWh [46], the economic results are once 459 again positive, even if slightly worse than the case with italian electricity price. In deed, by using the european electricity 460 price, the proposed system allows a PBP reduction with respect to a commercial control system, from 11 to 6 years, and 461 a NPV increase, from 876.0 € to 1,481.0 €. 462 5. Conclusions 463 Lighting control systems with dayligh t and occupancy adaptation allow relevant reduction of energy consumption, 464 but they are often affected by installation complexity, high costs, difficulties on the evaluation of real energy benefits, 465 technical management problems, and, above all, proper mat ching of the dimming system for the used lamps. For these 466 reasons, diffusion of these systems is lower than expectations. 467 This paper presents a new lighting control system, especially conceived for installation on existing buildings. This 468 system is based o n smart control unit and lighting control devices that can be directly mounted on the lamps in series 469 connection. The installation of the system is noninvasive and does not require any changes in the electrical grid, since 470 27 the communication between each la mp and the control system is based on long range wireless communication at 2.4 471 GHz. The system architecture has been proved in laboratory. The main and novel results obtained are its functionality 472 with any lamps (fluorescent, non -dimmable LED, and dimmable LED), and its applicability to real cases. 473 At the end of the experimental laboratory tests, being not possible to install the proposed system in public 474 environment, since it is at prototypical stage, the feasibility of the system has been verified at sim ulation level. The case 475 study is a classroom of the Faculty of Engineering of the University of L’Aquila, in central Italy. The simulated model 476 was calibrated both with natural and artificial light, showing deviation values within ± 20%. This phase allowed 477 carrying out energy analysis of the performances of the lighting plant, considering different technologies and control 478 strategies: fluorescent, dimmable and non -dimmable LED lamps, and with occupancy and daylighting adaptation, 479 provided by the proposed sy stem. The economic analysis, deepened by comparing the proposed system with a 480 commercial lighting control system, clearly shows that the proposed system is affordable, reducing the payback time of 481 the investment. 482 The main results obtained are: 483  a new universal daylight and occupancy control system for any lamps. Laboratory tests on the system show ed 484 positive results; 485  the application of the proposed system, simulated through the use of a validated model in a academic classroom, 486 allows energy saving equa l to 69.6 % and 30.5 % of CO 2 emissions avoided; 487  improvement of the PayBack Period from 9 to 5 years, by comparing the investment costs of the proposed system 488 with respect to a commercial lighting control system. 489 According to these encouraging results, fut ure development of t he proposed system will involve the application in 490 real scenarios , once obtained the product qualification. 491