Abstract
High-tech greenhouses and artificial light applications aim to improve food production, in line with one of the sustainable development goals of the UN Agenda 2030, namely, “zero hunger”. In the past, the incandescent lamps have been used for supplementary lighting (SL) at higher latitudes to increase greenhouse production during the dark season. Light-emitting diodes (LED) have been replacing gas discharge and incandescent lamps, and their development is expanding SL applications in different agricultural scenarios (e.g., urban farming, middle latitudes). In fact, recent research on LED applications in Mediterranean greenhouses have produced encouraging results. Since middle latitudes have a higher daily light integral (DLI) than higher latitudes in the dark season and climate conditions influence the installed power load of greenhouses, LED installation and management in Mediterranean greenhouses should be different and less expensive in terms of investment and energy consumption. Accordingly, the aim of this review is to outline the state of the art in LED applications and development, with a focus on latitude-related requirements. Tomato was used as a representative crop.
Highlights
Based on the United Nations sustainable development goals, high-tech greenhouses will remain the most efficient systems for food production [1], and the use of artificial lighting, especially in northern Europe and North America, is fundamental for achieving the sustainable development goal of “zero hunger” [2].The first use of artificial light in agriculture was in 1861 in France
Before the advent of light-emitting diodes (LEDs), high-pressure sodium (HPS) lamps were the most widely used in horticulture greenhouses due their electrical efficiency (30–40%; Table 1)
LED technology is the most widely adopted for artificial lighting in greenhouses, due to its spectral flexibility in the wavelengths required by plants and its energy conversion efficiency (Table 1)
Summary
Based on the United Nations sustainable development goals, high-tech greenhouses will remain the most efficient systems for food production [1], and the use of artificial lighting, especially in northern Europe and North America, is fundamental for achieving the sustainable development goal of “zero hunger” [2]. Since the energy conversion efficiency of such lamps is as low as 1 to 5% (Table 1), they were replaced by gas discharge lamps (fluorescent, high-pressure, and metal-halide), which became the most widely adopted solution for residential and agricultural applications. Before the advent of light-emitting diodes (LEDs), HPS lamps were the most widely used in horticulture greenhouses due their electrical efficiency (30–40%; Table 1). LED technology has continued to develop different semiconductors to obtain different light emission spectra, increase energy efficiency, and match plant absorption spectra. LED technology is the most widely adopted for artificial lighting in greenhouses, due to its spectral flexibility in the wavelengths required by plants and its energy conversion efficiency (Table 1). The effects of different spectral composition, position (interlighting and toplighting), photosynthetic photon flux density (PPFD), and daily light integral (DLI) on tomato growth are discussed, and we compare SL installation and management at middle and high latitudes
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