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Beyond producing leafy greens, there is a growing interest in strawberry production on indoor vertical farms. Considering that sole-source lighting is one of the most important components for successful indoor crop production, we investigated how photosynthetic photon flux density (PPFD) and the photoperiod of sole-source lighting affected plant growth, flowering, and fruit production in strawberry ‘Albion.’ Bare-rooted strawberry plants were grown in deep water culture hydroponics inside an indoor vertical farm at 21 °C under white + blue + red light-emitting diodes at a PPFD of 200, 300, or 450 µmol∙m−2∙s−1 with a 12-h or 16-h photoperiod. Under both photoperiods, increasing PPFD from 200 to 450 µmol∙m−2∙s−1 linearly increased crown diameter by 18–64%, shoot fresh and dry mass by 38–80%, and root fresh and dry mass by 19–48%. Under a PPFD ≥ 300 µmol∙m−2∙s−1, root fresh and dry biomass increased by 95–108% and 41–44%, respectively, with an increasing photoperiod from 12 to 16 h. In addition, increasing the photoperiod from 12 to 16 h accelerated flowering by 17–21 days under a PPFD ≥ 300 µmol∙m−2∙s−1 and first fruit harvest by 17 days at a PPFD of 450 µmol∙m−2∙s−1. Regardless of PPFD, strawberry fruit production (g·m−2·month−1) increased by 372–989% under a 16-h photoperiod in comparison to under a 12-h photoperiod. In contrast, there was little effect of PPFD on fruit production. Our results suggest that increasing the PPFD or photoperiod can increase strawberry plant growth, but increasing the photoperiod can have a dominant effect on increasing early fruit production in strawberry ‘Albion’.

To match the key features of light-emitting diode (LED) lighting source and further save power, LED lighting driver also requires long life, while maintaining high efficiency, high power factor, pulse-width modulation dimming and low cost. However, a typical LED lighting driver has the following drawbacks: (i) utilise bulky electrolytic capacitor as storage capacitor with short lifetime; (ii) employ a low-frequency diode bridge as the rectifier cell; and (iii) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, this study proposed a bridgeless electrolytic capacitor-less AC/DC converter for offline LED lighting application. In the proposed converter, the conventional diode rectified bridge is replaced by Totem-pole bridgeless configuration for reducing the number of semiconductors in the line-current path. Meanwhile, the valley-fill circuit is introduced to further reduce the capacitor size. As comparison to its counterpart, the proposed circuit requires only one quarter of the capacitor energy when considering the energy amount (CV2) as the capacitor sizing criterion. Furthermore, the isolation type of the studied circuit is compatible with Twin-Bus configuration for achieving higher overall system efficiency. Finally, the experimental results, taken from a laboratory prototype rated at 50 W, are presented to verify the effectiveness of the proposed converter.

Daylight controls our natural biorhythm, influences our mood, has an important effect on how we feel and has an essential role in creating a healthy workplace. In most cases, daylight is not enough for reach the levels of illumination appropriate to the normal operation and we use artificial light. Incorrect lighting affects people's comfort, can lead to physical fatigue (especially eye fatigue) and reduced intellectual performance, especially when high concentration is needed. The implementation of lighting systems based on LED technology in the seminar halls, using the natural light input via a light sensor, provides lighting flexibility and ensures a level of illumination appropriate to the our activities. By replacing the current lighting systems with the LED technology and implementing a lighting control system there are significant reductions in energy consumption and CO2 releases. The OccuSwitch DALI protocol is a sensor that connects to the luminaires to be controlled. The sensor has two functions: a light sensor and a motion sensor for presence control. By implementing this solution, savings of up to 70% can be achieved compared to the current lighting system.

In recent years, research on light emitting diodes (LEDs) has highlighted their great potential as a lighting system for plant growth, development and metabolism control. The suitability of LED devices for plant cultivation has turned the technology into a main component in controlled or closed plant-growing environments, experiencing an extremely fast development of horticulture LED metrics. In this context, the present study aims to provide an insight into the current global horticulture LED industry and the present features and potentialities for LEDs’ applications. An updated review of this industry has been integrated through a database compilation of 301 manufacturers and 1473 LED lighting systems for plant growth. The research identifies Europe (40%) and North America (29%) as the main regions for production. Additionally, the current LED luminaires’ lifespans show 10 and 30% losses of light output after 45,000 and 60,000 working hours on average, respectively, while the vast majority of worldwide LED lighting systems present efficacy values ranging from 2 to 3 μmol J−1 (70%). Thus, an update on the status of the horticultural LED sector, LEDs’ applications and metrics, and the intense innovation are described and discussed.

Vitamin D deficiency has become a social problem in many countries as modern people’s indoor living time increases and their exposure to natural light shortens. In order to solve this problem, sun exposure is recommended. Outdoor activity guide service is provided by providing accurate UV-related information, while UV lighting technology is being developed in order to provide UV dose to indoor residents. However, these methods have limitations in directly supporting adequate UV doses for those who have difficulty in carrying out outdoor activities, whereas UV lighting does not provide accurate safety information about exposure. In this paper, a UVB-LED special lighting that supports indoor residents to meet a daily recommended UVB dose is proposed. First, the UVB-LED light source that can achieve an optimal UVB dose is selected. Its lighting characteristics are measured and analyzed and then a combination and control condition of the light source that can safely provide UVB dose are derived. After a stand-type lighting equipment considering ease of use is designed, a UVB-LED special lighting that meets the photobiological safety standard of lighting (Risk Group 2) is developed. The expected amount of vitamin D synthesis by distance and use duration is calculated through a performance test for the proposed lighting. The test results show that when the proposed lighting is used at a distance of 20 cm for 33–40 min, the daily recommended vitamin D synthesis can be achieved.

More than a century after the introduction of incandescent lighting and half a century after the introduction of fluorescent lighting, solid-state light sources are revolutionizing an increasing number of applications. Whereas the efficiency of conventional incandescent and fluorescent lights is limited by fundamental factors that cannot be overcome, the efficiency of solid-state sources is limited only by human creativity and imagination. The high efficiency of solid-state sources already provides energy savings and environmental benefits in a number of applications. However, solid-state sources also offer controllability of their spectral power distribution, spatial distribution, color temperature, temporal modulation, and polarization properties. Such \"smart\" light sources can adjust to specific environments and requirements, a property that could result in tremendous benefits in lighting, automobiles, transportation, communication, imaging, agriculture, and medicine.

Light emitting diodes (LEDs) are an energy efficient alternative to high-pressure sodium (HPS) lighting in tomato cultivation. In the past years, we have learned a lot about the effect of red and blue LEDs on plant growth and yield of tomatoes. From previous studies, we know that plants absorb and utilize most of the visible spectrum for photosynthesis. This part of the spectrum is referred to as the photosynthetically active radiation (PAR). We designed a LED fixture with an emission spectrum that partially matches the range of 400 to 700 nm and thus partially covers the absorption spectrum of photosynthetic pigments in tomato leaves. Tomato plants grown under this fixture were significantly taller and produced a higher fruit yield (14%) than plants grown under HPS lighting. There was no difference in the number of leaves and trusses, leaf area, stem diameter, the electron transport rate, and the normalized difference vegetation index. Lycopene and lutein contents in tomatoes were 18% and 142% higher when they were exposed to the LED fixture. However, the ß-carotene content was not different between the light treatments. Transpiration rate under LED was significantly lower (40%), while the light use efficiency (LUE) was significantly higher (19%) compared to HPS lighting. These data show that an LED fixture with an emission spectrum covering the entire PAR range can improve LUE, yields, and content of secondary metabolites in tomatoes compared to HPS lighting.

The use of light-emitting diode (LED) technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL) regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity.

Silicon substrate golden light LED, as an emerging blue-light-free health lighting technology, has become one of the key technologies for home health lighting environments. This study uses silicon substrate golden light LED as the lighting source for home lighting, and based on the lighting demands of two indoor types, employs DIALux Evo lighting simulation software to simulate the indoor lighting environment. First, the simulated lighting data for various indoor areas are compared with the national lighting standards (GB/T50034-2024) to verify whether the lighting type meets the home lighting requirements. Next, a comparison is made between the lighting efficiency of silicon substrate golden light LED and a reference sample LED to validate whether the silicon substrate golden light LED possesses high lighting efficiency and low power consumption. Finally, long-term exposure to both the silicon substrate golden light LED and reference sample LED is used to record the secretion levels of melatonin in the human body. The experimental results show that the silicon substrate golden light LED not only provides sufficient home lighting but also demonstrates high efficiency and low power consumption. Additionally, under the illumination of silicon substrate golden light LED, the melatonin secretion concentration significantly increases to (960 ± 15) pg/mL after 2.5 h of exposure, which is 8.2 times higher than that of the conventional LED group (t = 12.34, df = 14, p < 0.001). The silicon substrate golden light LED technology provides a feasible solution for home health lighting design by creating a zero-blue-light health lighting environment.

Inorganic light-emitting diodes and photodetectors represent important, established technologies for solid-state lighting, digital imaging and many other applications. Eliminating mechanical and geometrical design constraints imposed by the supporting semiconductor wafers can enable alternative uses in areas such as biomedicine and robotics. Here we describe systems that consist of arrays of interconnected, ultrathin inorganic light-emitting diodes and photodetectors configured in mechanically optimized layouts on unusual substrates. Light-emitting sutures, implantable sheets and illuminated plasmonic crystals that are compatible with complete immersion in biofluids illustrate the suitability of these technologies for use in biomedicine. Waterproof optical-proximity-sensor tapes capable of conformal integration on curved surfaces of gloves and thin, refractive-index monitors wrapped on tubing for intravenous delivery systems demonstrate possibilities in robotics and clinical medicine. These and related systems may create important, unconventional opportunities for optoelectronic devices. Flexible electronic devices that can be stretched without losing performance have seen increasing functionality. In particular, the demonstration of light-emitting diodes and photodetectors on flexible electronic substrates now opens the door to applications of flexible optoelectronic sheets in biomedicine and robotics.