The lighting industry is still a linear economy, despite the extensive use of light-emitting diode (LED) and the ban of incandescent/halogen lamps, claiming to be greener and more human centered. Light-emitting diode has changed radically the whole lighting industry with an increased luminaire efficacy more than four times higher compared with fluorescent lamps and their new opportunities for modern control systems. In the years to come, millions of fluorescent luminaires will become waste and will be replaced by LED luminaires. According to the Cost European Cooperation in Science & Technology Program the next step will be from sustainability to regenerative (enabling social and ecological systems to maintain a healthy state and to evolve) and to get there, circular economy is essential. In order to reduce even further the carbon footprint, the retrofit of existing luminaires and additional modern control systems should be the solution. Circular economy aspects for the lighting area were identified using the university adopted lighting retrofit solutions as case studies. For an LED retrofitted recessed luminaire 4 × T8 18 W studies showed a major installed power reduction, a good lighting distribution, but also revealed some problems: the retrofit luminaire has no certification, necessity of qualified personnel, high labor costs, etc. A major issue is the fact that luminaire design did not take into consideration circular economy aspects like the possibility of future retrofit solutions. It is important that from now on a different approach should be foreseen for the LED luminaire design. There is a section about vision, which plays an important role in preparing new luminaire generations with circular economy in mind.

Daylight levels decrease asymptotically with distance from the window so that a disproportionate amount of daylight/solar gain must be introduced into the front of the room to achieve small increases in daylight deep inside at the back. Several systems exist to redirect daylight into areas of buildings that cannot be lit by traditional glazing. One major generic group is known as ‘beam daylight’ - redirects sunlight by adding reflective or refracting elements to conventional windows. The second major group is known as Tubular Daylight Guidance Systems (TDGS). Tubular daylight guidance systems are linear structures that channel daylight by means of optical interactions into the core of a building. The paper presents a case-study for a passive TDGS installed in a residential building in Cluj-Napoca, Romania. Field measurements are presented as well as software simulation results (DIALux, Lux Calculator). Based on the official numbers of dwellings provided by the Romanian National Institute of Statistics and the energy savings presented in the case-study, some predictions were made regarding the energy saving potential of passive tubular daylight systems over Romania.

For the next few years millions of fluorescent luminaires will become waste and will be replaced by light-emitting diodes—LED luminaires. According to the Cost European Cooperation in Science & Technology Program, the next step will be shifting from sustainability to regeneration (enabling social and ecological systems to maintain a healthy state and to evolve); to reach this point, a is circular economy becomes necessary. The Technical University of Cluj-Napoca’s Lighting Engineering Laboratory—LEL—is the main lighting independent consultant in Transylvania (the north-west region of Romania). For the Building Services Faculty, LEL adopted different energy efficient lighting solutions to replace existing fluorescent T8 luminaires. The best available techniques were evaluated over the last few years. Out of a range of different smart lighting control systems, LED were chosen and used for retrofitting the existing T8 luminaires or simply replacing them with new dedicated LED luminaires. The study analyzed five different lighting setups for upgrading the existing fluorescent T8 2*36W luminaires. One setup used T5 lamps and the others used retrofitted or dedicated LED lighting solutions. First the lighting quantities of each setup were evaluated under real and experimental conditions. Second, a programable power source was used for measuring power quality indicators corelated with the provided lighting outputs, under different voltage values and waveforms. For each lighting setup, an even and odd current harmonic limit check was performed in line with class C—lighting equipment, IEC 61000-3-2 requirements. A new energy efficiency and power quality indicator was proposed—the lighting apparent power density [VA/sq.m/100lx].

The paper analyses the power-quality effects of connecting LED luminaires to street lighting installations. The power quality impact of LED luminaires and the implementation of smart control systems are discussed. Several power-quality measurements have been performed to determine the effect of connecting multiple LED luminaires to the electrical power network. Three LED street lighting systems were selected, each equipped only with LED luminaires of different power ratings and numbers, produced by different manufacturers. The measurements were performed at the lighting connection box, and the results are presented and discussed for each case.