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Vertical farming is considered to play a crucial role in future food supply. Until today, the high amount of electrical energy required for artificial lighting has been problematic in this context. Various possibilities for increasing efficiency through adapted lighting conditions have been and are being investigated. However, comparably little att...
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... These systems increase land use efficiency and maximize crop productivity by operating independently of external climates [3,4]. However, the high energy demands, particularly from the lighting, remain a barrier to commercial scalability, with lighting consuming 52% to 80% of the total energy [5]. Therefore, improving the light use efficiency of LEDs has become crucial for reducing operational costs and achieving energy Therefore, three nonlinear growth models were applied to simulate the growth process of hydroponic lettuce, and the best model was selected to determine the key time points for different growth stages. ...
The widespread application of LED plant factories has been hindered by the high energy consumption and low light use efficiency. Adjustment of the daily light integral (DLI) offers a promising approach to enhance the light use efficiency in hydroponic cultivation within LED plant factories. However, most LED plant factories use a constant DLI during the cultivation process, which often leads to excessive light intensity in the early growth stage and insufficient light intensity in the later stage. To address this issue, this study aimed to improve the photon yield of hydroponic lettuce by optimizing the DLI at different growth stages. A logistic growth model was employed to segment the lettuce growth process, with variable DLI levels applied to each stage. DLIs of 11.5, 14.4, and 18.0 mol m⁻²·d⁻¹ were implemented at the slow growth stage, and the DLIs were adjusted to 14.4, 17.3, and 21.2 mol m⁻²·d⁻¹ at the rapid growth stage. Photoperiods of 16 h·d⁻¹ and 20 h·d⁻¹ were used for the two growth stages, and LED lamps with white and red chips (ratio of red to blue light was 1.5) were used as the light source. The results indicated that the photoperiod had no significant impact on the shoot fresh weight and photon yield under the constant DLI conditions at the slow growth stage (12 days after transplanting). The 14.4 mol m⁻²·d⁻¹ treatment resulted in the highest photon yield due to the significant increases in the light absorption and net photosynthetic rate of the leaves compared to the 11.5 mol m⁻²·d⁻¹ treatment. No significant differences in the specific leaf area (SLA) and leaf light absorption were observed between the 14.4 and 18.0 mol m⁻²·d⁻¹ treatments; however, the photon yield and actual photochemical efficiency (ΦPSII) significantly decreased. Compared with the DLI of 14.4 mol m⁻²·d⁻¹ at the rapid growth stage (24 days after transplanting), the 17.3 mol m⁻²·d⁻¹ treatment with 20 h·d⁻¹ increased the leaf light absorption by 5%, the net photosynthetic rate by 35%, the shoot fresh weight by 25%, and the photon yield by 19%. However, the treatments with DLIs above 17.3 mol m⁻²·d⁻¹ resulted in notable decreases in the photon yield, ΦPSII, and photosynthetic potential. In conclusion, it is recommended to implement a 20 h·d⁻¹ photoperiod coupled with a DLI of 14.4 mol m⁻²·d⁻¹ for the slow growth stage and 17.2 mol m⁻²·d⁻¹ for the rapid growth stage of hydroponic lettuce cultivation in an LED plant factory.
... CEA in the urban desert is becoming a widespread plant production practice as a local food supplier. In the USA, the plant food production system uses 70% of the country's freshwater and 17% of fossil fuel and contributes 80% to pesticidal water contamination [69][70][71]. Generally, aeroponics, deep water, NFT, ebb and flow, and aquaponics are used as plant irrigation in CEA farming [72][73][74][75]. ...
The extreme heat and water scarcity of the desert southwest in the United States of America present significant challenges for growing food crops. However, controlled-environment agriculture offers a promising solution for plant production in these harsh conditions. Glasshouses and plant factories represent advanced but energy-intensive production methods among controlled-environment agriculture techniques. This review aims to comprehensively assess how controlled-environment agriculture can thrive and be sustained in the desert southwest by evaluating the energy efficiency of controlled glasshouses and building-integrated plant factories. The analysis focuses on the efficiency of these systems’ energy and water consumption, mainly using artificial lighting, heating, cooling, ventilation, and water management through various hydroponic techniques. Approximately 50% of operational energy costs in controlled glasshouses are dedicated to cooling, whereas 25–30% of energy expenses in building-integrated plant factories are allocated to artificial lighting. Building-integrated plant factories with aeroponic systems have demonstrated superior water use and energy efficiency compared to controlled glasshouses in desert environments. Integrating photovoltaic solar energy and glass rooftops in building-integrated plant factories can significantly reduce energy costs for urban farming in the desert southwest.
... The energy requirement for artificial lighting maintaining the set temperature and humidity can be fulfilled by optimizing maximum solar irradiance collection by the orientation of the planting trays at the required angles (Ng & Foo, 2020). Substituting energy-efficient LED lighting can help in reducing energy consumption to half (Balasus et al., 2021). The urban horticulture on the usable rooftops can mitigate the temperature inside the building in the summertime, which lowers the HVAC cost (Bonito et al., 2018). ...
The concept of green cities has been getting sustained focus for some time, intending to transform dispersed cities into environmentally, ecologically, and socially healthier spaces to live. The concept interlinks different domains of urban development, such as spatial planning, transport, water and sanitation services, urban greenery, renewable energy, sustainable building construction, and socioeconomic growth through green solutions. Energy planning and management play a vital role in transforming urban areas into environmentally sustainable cities. Integrating energy management as a key aspect of green city strategies from the pre-planning to post-implementation stages can expedite the process. This paper attempts to comprehend the intertwined role of energy management in green city planning through a comprehensive literature review. Relevant articles that discuss energy and management in interdisciplinary domains under the green city concept were identified and reviewed for the period—2000–2021. Diverse energy-efficient management measures and techniques are reviewed under seven domains of green city planning: green spatial planning, transportation, public infrastructure, urban agriculture, buildings, energy, and growth. The summarized literature emphasizes the relevance and significance of efficient energy management in the transition toward a green city. The study also discusses the need for a gradual transition and the challenges in successfully implementing and managing sustainable strategies. The successful implementation of climatic and environmental solutions through policy-level strategic interventions demands continuous effort and monitoring to achieve the long-term goal of sustainability. Energy-efficient urban development practices, with the foundation of a policy framework, can act as sustainable solutions to maintain the synergy between energy independence and urban development. Expediting the transformation of green cities with the adoption of energy-efficient strategies and renewables to decarbonize the energy supply is an accomplishable vision for every city.
... The improvement in functionality of these devices has resulted in a decrease in overall power consumption and has coincided with the development of several photovoltaic (PV) technologies, such as Dye sensitized solar cells [2], organic solar cells [3], and perovskite solar cells [4], that are highly efficient at harvesting ambient light, resulting in the possibility of developing perpetually self-powered battery-less IoT. One of the advantages these newer generation of PVs have over more established technologies is the ability to tune the spectral responsiveness of the PV device tailored to varied light conditions [5] found in homes [6][7][8] offices [9], factories [10,11], hospitals [12][13][14], retail stores [15,16], and other indoor locations [17][18][19][20][21][22][23][24]. ...
As the Internet of Things (IoT) expands, the need for energy-efficient, self-powered devices increases. This study examines light power resource availability for photovoltaics (PV) in various environments and its potential in self-powered IoT applications. We analyse light sources, considering spectral distribution, intensity, and temporal variations, and evaluate the impact of location, seasonal variation, and time of day on light power availability. Additionally, we discuss human and building design factors, such as occupancy, room aspect, sensor placement, and décor, which influence light energy availability and power for IoT electronics. Our data identifies best-case and non-ideal scenarios for light resources, estimating the energy yield from a commercially available organic photovoltaic cell, contributing to a deeper understanding of light power resource availability for self-powered IoT devices
... This situation is reflected in CML-LPS and CML-QS, which achieve 60% and 65% photon capture by applying a 45 • beam in the first phase of growth, 90 • in the second and third, and 140 • in the last with interleaved ignition lights. These structures, mainly due to the circular design of the luminaire [32], show savings in energy costs compared to LSL-LPS and LSL-QS, which maintain static lights with the same opening angle throughout the lettuce growth. ...
Indoor agricultural offers efficient alternatives for intensive food production through automation technologies and controlled environments. Light plays a crucial role in plant development; however, photons captured by the crop are often wasted in empty spaces, resulting in low light efficiency and high energy costs. This research aims to simulate eight structural designs for an indoor lettuce crop, exploring different planting systems and light and culture bed combinations (static and mobile) to identify the most effective mechanism for light efficiency during crop growth. The simulations were carried out with spreadsheets based on applying formulas of yield in dry biomass per photosynthetic photons, lighting costs, harvest, and production. The results indicate that Circular Moving Light and Mobile Culture Bed with Quincunx Planting (CML-QM) and Circular Moving Light and Mobile Culture Bed with Linear Planting (CML-LPM) exhibit higher photon capture percentages (85% and 80%, respectively) and lower electricity consumption compared to static designs. The simulation results demonstrate the potential for significant improvements in photon capture and cost savings through optimized system designs. This investigation provides valuable insights for designing more efficient systems and reducing electricity consumption to enhance the capture of photosynthetic photons in indoor lettuce cultivation.
... However, LED physical capabilities can be further leveraged to enhance crop canopy photon capture efficiency (CCPCE) or utilance, efficiency metrics of the fraction of emitted photons incident upon photosynthetic surfaces of plants (Balasus et al., 2021). If CCPCE also is high, overall EUE of an indoor crop-lighting system can be further enhanced. ...
Significant advancement has been achieved improving electrical efficiency and photon efficacy of light-emitting diodes (LEDs) as the sole source of crop lighting for indoor farming. However, a significant portion of highly efficient photon emissions from improved LEDs is wasted by natural beam spread beyond cropping areas. Additional attention is needed to enhance crop-canopy photon capture efficiency (CCPCE), the fraction of photons emitted from LEDs actually incident upon foliar canopies. We postulate that by taking advantage of unique physical properties of LEDs, such as low radiant heat at photon-emitting surfaces and dimmable photon emissions, reduced vertical separation distance between light-emitting surfaces and light-receiving surfaces will enhance CCPCE by capturing more obliquely emitted photons that otherwise are lost. This “close-canopy-lighting” (CCL) strategy was tested in two ways: For an energy-efficiency strategy, LEDs were dimmed to the same photosynthetic photon flux density (PPFD) of 160 µmol m⁻² s⁻¹ at 45-, 35-, 25-, and 15-cm separation distances between lamps and cropping surfaces. For a yield-enhancement strategy, dimming was not applied, so higher PPFDs occurred at each separation distance closer than 45 cm for the same input energy. In the first strategy, the same biomass of lettuce (Lactuca sativa L. cv. Rouxai) was produced at each separation distance, while significantly lower energy was expended for lighting at each closer separation. Significantly higher biomass was produced at reduced separation distances with the same energy expenditure by LEDs using the yield-enhancement strategy. For both strategies, energy-utilization efficiency (g/kWh) doubled at the closest separation distance of 15 cm compared to the standard 45-cm separation distance. Even higher energy-utilization efficiency was achieved at a 25-cm separation distance when growth compartments were enclosed with a reflective curtain in the yield-enhancement strategy. Our findings suggest that CCL is a highly effective energy-saving strategy for overhead LED lighting, suggesting the need for innovative next-generation re-design of height-adjustable LED mounts and controlled air movement between tiers of indoor farms utilizing CCL.
... At the end of the vegetative stage (day 13), the remaining nine plants were switched to inductive photoperiod (12 h d −1 ) for 8 weeks (day 14-70) until harvest. The light uniformity in each light treatment was between 0.91 to 0.94; this was determined by the ratio of the minimum to average PPFD level as described by Balasus et al. [61]. During cultivation, plants were randomly reorganized every 3 days, which avoided inconsistent PPFD levels caused by light uniformity. ...
Light is one of the most crucial parameters for enclosed cannabis (Cannabis sativa) production, as it highly influences growth, secondary metabolite production, and operational costs. The objective of this study was to investigate and evaluate the impact of six light spectra on C. sativa (‘Babbas Erkle Cookies’ accession) growth traits and secondary metabolite (cannabinoid and terpene) profiles. The light spectra evaluated included blue (430 nm), red (630 nm), rose (430 + 630 nm, ratio 1:10), purple (430 + 630 nm, ratio 2:1), and amber (595 nm) LED treatments, in addition to a high-pressure sodium (HPS, amber-rich light) treatment as a control. All the LED light treatments had lower fresh mean inflorescence mass than the control (HPS, 133.59 g plant⁻¹), and monochromatic blue light yielded the least fresh inflorescence mass (76.39 g plant⁻¹). Measurement of Δ9-tetrahydrocannabinol (THC) concentration (%) and total yield (g plant⁻¹) showed how inflorescence mass and THC concentration need to be analyzed conjointly. Blue treatment resulted in the highest THC concentration (10.17% m/m), yet the lowest THC concentration per plant (1.44 g plant⁻¹). The highest THC concentration per plant was achieved with HPS (2.54 g plant⁻¹). As with THC, blue light increased cannabigerol (CBG) and terpene concentration. Conversely, blue light had a lesser impact on cannabidiol (CBD) biosynthesis in this C. sativa chemotype. As the combined effects of the light spectrum on both growth traits and secondary metabolites have important ramifications for the industry, the inappropriate spectral design could cause a reduction in cannabinoid production (20–40%). These findings show promise in helping producers choose spectral designs that meet specific C. sativa production goals.
... CPCE was initially defined by Bugbee (2016) but has more recently been dubbed utilance by Balasus (2021) based on photometric qualities from the International Lighting Vocabulary. [6][7][8] Utilance may be expressed as where , is the photon flux received by the reference surface and is the sum of photon fluxes emitted by the luminaires of the lighting system. In the context of targeted lighting in CEA, the reference surface includes all photosensitive bodies of the plant, which includes leaves and fruits. ...
... The Raspberry Pi photographs the growth area with a camera and identifies plant tissue using OpenCV. The pixels on 7 International Conference on Environmental Systems the camera are segmented into four groups: Usable areas (UA) 1-3 and unusable area. The UA 1-3 pixels correspond to LED segments 1-3 as shown in Figure 6. ...
... 24 Finally, with respect to imaging, a spatially resolved plant model would provide estimates of PPFD, leaf area, and other phenotypic traits. 7,25,26 Integrating multiple cameras with the light fixture would provide the input necessary for creating an accurate, three-dimensional model of the plant. ...
The challenge of meeting the increasing global food demand has driven a shift toward controlled-environment agriculture, particularly in plant factories. However, the high energy consumption associated with these systems raises concerns about their long-term sustainability and economic feasibility. A comprehensive review was conducted to identify existing and potential technologies and strategies that can enhance the energy efficiency of plant factories. Data regarding environmental conditions, energy efficiency, water efficiency, and space efficiency were also extracted to facilitate comparison across studies. Findings indicate that optimizing crop yields and reducing energy consumption are key to improving the efficiency of plant factories. These can be achieved by integrating advanced environmental control technologies, energy-efficient system designs, modular plant factory configurations tailored to local climatic conditions, and effective management practices. While adopting renewable energy alone is insufficient to meet total energy demands, it significantly reduces energy costs and carbon emissions. Furthermore, strategically integrating plant factories with other industries will promote the efficient use of residual resources, fostering a circular economy and enhancing resource efficiency within plant factory systems and the broader economic framework. The insights provided in this review will contribute to developing sustainable and economically viable plant factory systems, supporting future advancements in controlled-environment agriculture.
