Literature Review Lettuce Agrivoltaics

Publisher : Plants

Year: 2023

Introduction:

• White (50% cool white + 50% warm light) (W);
• Red spectral bands with the maximum at660 nm and blue spectral bands with the maximum at 450 nm with ratio (1:1) (R/B450(1:1));
• Red spectral bands with the maximum at 660 nm and blue spectral bands with the maximum at 435 with ratio (1:1), (R/B435(1:1));
• Red spectral bands with the maximum at 660 nm and blue spectral bands with the maximum at 450, blue: red (1:1) supplemented by far red and green with ratio (1:1:0.07:0.64) (B/R/G/FR (1:1:0.07:0.64). Green is a wide range wavelength (500–600 nm). Rare red spectral bands with the maximum at 725 nm;
• White (50% cool white + 50% warm light) + UV-B (0.3 µW cm−1) (for an hour/24 h for a week before harvest) (W/UV-B). UV-B intensity was set at 0.3 microwatt.cm−2 measured using UV Light Meter UV340B (UV Light Meter, UV340B, Shenzhen Ever Good Electronic Co., Ltd., China). The UV-B was set to switch on during the lighting period of the other wavelengths;
• Red spectral bands with the maximum at 660 nm and blue at combination of blue spectral bands with the maximum at 435 nm + 450 nm with ratio (1:1), blue: red (1:1). (R/B450-435 (1:1)

Methodology: lab grown closed enivoronmnet

Result: Attention should ne on the use of R/B light commercially and recognizing that commercial harvest of a potentially smaller lettuce will be achieved earlier than a white light conventional growing system. This could be advantageous if the smaller lettuce size was acceptable to the purchaser. important far-red wavelengths accentuated the stem elongation in both varieties of lettuce, which can be used with caution in commercial set-ups.

Publisher:Plants

Year: 2021

Introduction:

This research focused on the physiology, growth and antioxidant response of hydroponically grown lettuce (Lactuca sativa L.) under only source LED lighting of differing wavelength. Lighting spectrums were created by differing combinations of LEDs of three different peak wavelengths, (Blue 435, Blue 450, and Red 663 nm) with different ratios .A further experiment was conducted, in which Blue and Red LEDs were combined  with Green (Blue 450, Red 663, and Green 520 nm) with different ratios.

Methodology:

they use red and blue light in agrotunnel to grow the lettuce

Result:

providing more blue colour with red will give more production

Discussion:

Publisher: Elsevier; Publication: Solar Energy;Year: 2021; Lifetime: ; PV Technology: ; Location: Lahore, Pakistan; PV Power: ; Energy: ; Efficiency:

• Introduction
  • Objective: To develop a light distribution model that can provide esimate of the irradiation incident on the ground in AV setting and use it to determine the implication on energy and crop yield
• Methodology
  • Two config: N-S oriented at a tilt and use monos, E-W vertical and use bifacials; location: Lahore, Pakistan
  • MATLAB code used for irradiance modelling; irradiation received by panels and ground calculated, shadowing on the ground, LER as well as crop yield (lettuce) determined
• Results and discussion
  • The two config tested with three variations in densities: p=h; p=2h and p=3h
  • Similar energy and crop yields for both confi for shade intolerant crops - with half dense PV config as compared to GMPV
  • Denser PV array; different yield; bi-E-W higher crop and mono-N-S higher energy
  • For greater than 80% of lettuce yield, PV density varies from half to twice of GMPVs
  • For greater than 80% of energy yield, crop yield varies from 65% (intolerant) to 100% (tolerant)
  • High hetrogeneity observed for N-S config while homogenous for E-W under low panel densities; for high panel densities, light distribution generally homogenous for both config
  • Crop yield suffers for E-W as p/h decreases; below p/h=4, crop yield for E-W are generally higher except for shade tolerant crops
  • At low densities, LER similar while it gets higher for monons with increased densities
  • Results related to impact of tilt angle also discussed
  • Soiling can cause 2-5% loss of annual PV power for tilted arrays
  • Model validation performed - model sligtly overstimates yield

Publisher: Elsevier; Publication: Renewable and Sustainable Energy Reviews ;Year: 2015; Location: US;

• Development of a solar PV model combined with crop and solar radiation model to ascertain the efficacy of agrivoltaic system
• 30% more economic value of agrivoltiac system when compared to agricultural systems
• In US, if lettuce fields were converted to agrivoltaic systems, more than 40 to 70 GW electricity generation can be increased
• PV System configuration: 4 meters high, half density - 3.2 m inter row spacing, full density - 6.4 m inter row spacing
• Lettuce can tolerate up to 30% shading
• 42% reduction in yeild for full density and 19% for half density agrivoltaic system as compared to control - Summer
• No significant reduction in yeild for lettuce in half density while 21% in full density as compared to control - Spring

Publisher: Elsevier; Publication: Applied Energy;Year: 2023;

• Increased land productivity by combining vertical farming (VF) with agrivoltaic greenhouses (closed agrivoltaic (CS) systems) - original CA had 100% PV cover ratio amd thus yield reduced significantly
• 13 times increased yield for lettuce observed as compared to CA only
• Energy required to meet the electricity needs - only 12% covered from CA
• More land required to achieve self sufficiency in electricity - 5 to 14 times higher than VF area
• Underutilized CA can be improved by integrating VF - a trade off between energy production and land consumption though exists

Publisher: Elsevier; Publication: Energy;Year: 2022;

• Objective: Ascertaining the potential of urban rooftop agrivoltaic system
• Case study: Shezhen, China
• Converting 854,000 rofftops can produce 9.84x105 tonnes of lettuce each year sufficient to fulfill the whole city needs
• Installed PV capcity will be 2106 MW - meets 0.2% of city's electricity needs
• PV panels coverage rate of up to 20% - checkerboard pattern - no reduction in lettuce yield

Publisher: Elsevier; Publication: Agricultural Water Management;Year: 2018; Lifetime: ; PV Technology: ; Location: Montpellier, France; PV Power: ; Energy: ; Efficiency:

• Introduction
  • Objective: To esimtate the effect of rain redistribution on crop yield and water requirement, ascertain water use and land use efficiencies, optimizng shading strategy soil water considering various factors
• Materials and methods
  • Location: Montpellier, France; crop: lettuce; drip irrigation
  • Four shading config; fixed tilt of 25o facing south - HD (3.2 m gap); FD (1.6m gap); ST (maximize solar interception by PV) and CT (parallel in morning and evening - max interception in afternoon)
  • Radiaion, air temp and RH, wind vel and dir, rain, soil moisture content was measured; evapotranspiration, water productivity and LER calculated
  • Irrigation model developed for AV considering stomatal conductance, variation of radiation and expandingo on Optirrig model
• Results
  • 33% ST, 30% HD, 49% FD and 23% CT - less radiation than Control
  • Actual evapotranspiration reduction: 22% ST, 26% HD, and 19% CT
  • Fresh biomass reduced for all AV config - -24% on average in spring; -16% for ST and CT while -31% for HD in summers
  • Reduced irrigation for both seasons for AV config
  • LER>1 for all AV config for both season
  • Almost similar yields are obtained with delay in harvest

Publisher: Elsevier; Publication: Renewable Energy;Year: 2022; Lifetime: ; PV Technology: ; Location: Lahore, Pakistan; Corvallis, US; PV Power: ; Energy: ; Efficiency:

• Introduction
  • Objective: To model variation in sunlight based on PV config and esimate implications on crop yield
• Methodology
  • Factor-based approach used to determine shading pattern underneath PV
  • Four config - N/S faced 30o fixed tilt, E-W verticals, N-S SAT and E-W SAT
  • Useful PAR ratio is the PARu,AV divided by PARu,open; Y,PAR = PARu,AV/PARu,open
  • Normalized PAR = PAR/PARth
• Results and Discussion
  • Half density = inter row spacing twice the normal heigh and half = four times the normal height; normal height 1m
  • PAR th = 213W/m2 for lettuce and tomato = 596W/m2
  • Fixed tilt - N/S vs E/W
    • E/W verticals have homogenous irradiation, higher PAR
    • N/S fixed tilts hetrogenous, lower PAR underneat panels compared to open space b/w modules
  • SAT - N/S vs E/W
    • Similar PAR pattern E-W vertical and E-W SAT
    • For both SAT - seasonal variation evident - higher in underneath panels in winters and lower in summers
    • Normalized PAR vary significantly under N-S SAT
  • Daily cummulative spatial useful PAR yield
    • 30% less useful PAR in winter and 10% in summer - NS fixed tilts, lettuce
    • 40-50% less useful PAR below PV modules, none in b/w spaces - NS fixed tilts, tomato
    • Tomato yield not less than 20% for E/W vertical - homogenous YPAR
  • Comparison with field experiment
    • Corvallis, US; N-S fixed tilt
    • YPAR from experiment = 0.46 and from simulation = 0.51
  • Intercropping for half density solar array
    • Based on threshold PAR (<80% for tomato), areas defined based on the pitch for cropping tomato and lettuce
    • Different for different configurations
    • E/W tracking - pitch can be segregated into 3 segments
    • N/S fixed - tomatoes to be farmed near north and lettuce south; uniform YPAR along the pitch during summer but not in winters
    • E/W verticals - YPAR more than 80%, hence no need for intercropping
    • Intercropping increases land productivity in general
  • Intercropping for full density solar array
    • N/S fixed - tomato and lettuce planted alternately
    • E/W vertical - same intercropping pattern as half density
    • E/W vertical provide highest YPAR for tomato, lowerst E/W SAt
    • 30% less radiation in full-density vs half-density
    • YPAR higher in half density than full density
  • Daily cummulative temporal useful PAR
    • N/S fixed tilt or tracking provide useful irradiation in mornings/evenings in summers; may be more useful for lettuce (shade tolerants)
    • In winters, useful radiation same for different configuations
  • Solar power output analysis
    • E/W tracking highest prodcution, N/S fixed tilt and tracking similar, E/W vertical the least
    • E/W provides highest useful PAR though

Publisher: Elsevier; Publication: European Journal of Agronomy;Year: 2012;

• Implication on crop yield and plant morphology/physiology of two different PV densities causing 50% and 70% shading
• Four types of lettuces experimented for two seasons
• Compared with the available relative radiation, the lettuce yield was either equal or higher
• FD:1.6m and HD: 3.2m inter row spacing, south facing and 25o fixed tilt
• 58% of contorl in FD and 81% for HD - in summers 2010; 79% and 99% of control for FD and HD in spring 2011

• Transparent modules used with optimcal micro-tracking technology from insolight to experiment lamb's lettuce
• 70% transmittance of incident light from modules; in trials 2 and 3 15% light transmission mode selected during mid day (12 to 2 pm)
• Chlorophyll content higher for crop under the modules - no difference between contorl and crop grown behind modules
• Leaves longer and wider under modules when compared to control and crop behind modules for trials 1 and 3, in the 2nd trial - not much difference
• Averaging all three trials, fresh weight under and behind modules increased by 17% and decreased by 8%, respectively, compared to the control
• Impact of seasons on fresh weight also observed

• Technoeconomic evaluation of lettuce agrivoltiac performed in Chile as lettuce is adversely affected by high irradiation
• Two scenarios: Either and AV plant will provide 30 to 40% shading or a separate GMPV is installed with nets providing the shading
• Both config fixed tilt, GMPV - modules 1m high while for AV module 2.4 m high
• Pitch distance 4m for GMPV while for AV, it will be determined based on light distribution simulation
• AV - azimuth: 310, panel tilt: 22; GMPV - azimuth: 0; panel tilt: 28
• Annual shading in AV between 30 to 40%
• AV presents a positive NPV; 7 years pay-back period

• Location of trial: Almeria - Spain
• Lettuce agrivoltaic tested under three different arrangements: concentrated shade (CS), scattered shade (SS) and full sun (FS) and in two season - spring and summer 2021
• With same shading cover area (22%), using mini PV modules arranged in pattern improves productivity in both seasons
• PAR was higher for SS than CS for all months of experiment
• Fresh weight of lettuce: SS - 46.4% more than CS and 68.8% more than FS; in summers even more - 61.2% and 87.6% more than CS and FS respectively

• Agrivoltaics systems installation for improved sunlight sharing between PV arrays and crops
  • Height of PV modules kept between 4 - 7 m above crops
  • Low density - p/h ratio 2 to 3 times of standard PV
• Paper introduces Light Productivity Factor (LPF) - factor that determines efficacy of light sharing between PV modules and crops
  • For PV only - LPF=1; with Agrivoltaics methodology 1 < LPF > 2
  • Used lettuce, turnip and corn
• Land Equivalent Ratio (LER) - factor that provides food-energy performance
  • Uses crop yield and electrical output
• Crop yield is directly proportional to useful photosynthetically active radiation (PAR)
• Crops have a threshold PAR above which the process of photosynthesis saturates
• Custom tracking; combination of standard and reverse tacking maximizes PAR requirement
• Results indicate:
  • For shade tolerant crops, full density PV arrays may be utilized
  • For shade sensitive crops. reduced density PV arrays may be utilized
  • E/W faced vertical PV orientation - preferable fixed tilt scheme
    • Benefits: Low elevation mounting, ease of operation of farm machinery and reduced soil loss

Publisher: Frontiers; Publication: Frontiers in Plant Science; Year: 2023; Lifetime:; PV Technology: Organic Solar Cell (OSC) ; Location: ; PV Power: ; Energy: ; Efficiency:

• Abstract
  • Semitransparent OSC effect electricity output as well as crop growth
  • Three different OSC filters used; lettuce and tomato grown
  • Lettuce yield not affected by AV; instead benefitted in terms of nutrient content and nitrogen utilization
• Introduction
  • 70% increase in food demand until 2050
  • Greenhouse more productive for crop growth, less water requirements, less pesticide/fertilizer use, provide shelter to plants from drought/heat/flood
  • Field crops damage due to weather in US in 2021 - 8 billion USD
  • Greenhouses are energy intensive, carbon footprint negative when compared to conventional crop if fossil fuels used in greenhouses
  • OSCs impact light spectrum as well as intensity
  • Blue and red light spectrum more efficiency used by plants for photosynthesis
  • Objective: To determine the impact of OSC on shade tolerant lettuce and shade intolerant tomato under simulated OSC greenhouse condition
  • No adverse impact on biomass
• Results
  • Light use: similar spectra as natural light
  • Biomass remained unaffected by different OSC filter
  • Photosynthesis improved in OSC when compared to control for lettuce, tomato same but transpiration rate decreased
  • Anthocyanin content for OSC in lettuce increased
• Discussion
  • The physiology of the plants changed with variation in light quality under different OSC filters

• Four scenarios considered, with varying parameters including latitude, azimuth, slope, and inter-row spacing between photovoltaic (PV) modules
• Two crops studied - potato and lettuce - potato more suitable to AV than lettuce considering its sensitivity to solar intensity
• Simulation based study using PV-syst and excel equations

• Lettuce and anthurium agrivoltaics showed 0.5 - 4.9oC decreased in module temperature resulting in upto 1.6% PV panel performance improvement
• Lettuce better than anthurium to boost efficiency of PV modules

Objective - Review existing literature of Agrivoltaics and ascertain its applicability in Australia

• Land equivalent ratio (LER) - parameter used for this study
• Electrical output of PV system modelled via System Advisory Model
• Crops (lettuce and silverbeet) grown without shading and under shade (using black tarps) for the study - solar panels not installed
• Yield produced in Agrivoltaics setting: 72% of lettuce yield compared with traditional farms; 60% of silverbeet yield compared with traditional farms (based on fresh mass)
• Reduced crop yield most probably due to increased shading

• Introduction
  • Inter-row distance in AV - thrice the height of panels
  • In dry climates, AV have shown to reduce drought stress, maintain higher soil moisture and imporved biomass
  • In suitable climates, reduction in crop yield and quality observed under AV
  • Objective: Propose Even-lighting Agrivoltaic System (EAS) for high yield/quality and eff. electrical output
• Materials and methods
  • From PV panel area, 1/3 area replaced with grooved glass plate; so area of glass plate is 1/3 the light receiving area of the system
  • PV density remains the same as conventional PV
  • Glass plate scatters the sunlight thus providing irradiation uniformly
  • Tilt considered 23o; height of PVs = 2.5m; model of glass developed in Solidworks and coupled with Zemax 12 to give the light patter/illimination
  • Two experiments:
    • smaller and semi-natural in Hefei; lettuce; four config: Control T1, Conventional AV T2, EAS T3 and EAS with additional lighting T4
    • larger in Fuyang; broccoli, shallot, garlic sprouts, garlic, broad bean, Jerusalem, rape; two config: control and EAS
  • PAR, crop growth, yield, LER, comprehensive eco benefits of EAS were measured
• Results
  • 47.38% improved irradiation with grooved glass as compared to conventional AV; crops growth rate similar to control
  • 5% yield reduction for all crops except broccoli and rape while Jerusalem artichoke increased 23%
  • EAS increases farmer income by 5.14 times and LER was 1.64
  • Uniform light scattering under grooved glass
  • Under conv AV, PPFD was v less when compared to control or EAS
  • 3.87% more irradiation received on panels than on ground; compared to control EAS received 40.87% less irradiation while conv AV 88.25% less
  • Lettuce: Similar fresh and dry weight in T1, T3 and T4; 53.5% and 60.5% reduction in T2
  • Large Scale Experiment: Reduction in broccoli 9%, rape 11%, shallot 2%, garlic sprouts 6%, garlic 4%, broad bean 6% and Jerusalem artichoke increased 23%
  • Protein content similar in 4 treatments, higher nitrate in T2 and T3 than T1 and T4
  • soluble sugar content in lettuce was T2> T4> T1>T3; for vitamin C, it was T2> T3> T1> T4; for nitrate content, it was T1 = T4 < T3 =T2
  • Farmer's income increased by 5.14 times for EAS
  • LER always greater than 1 - average 1.64

• The simulation performed on 1 ha - lettuce and sugar beetroot crop targetted
• Two different configuration - 3.2 m row spacing and 6.4 m row spacing
• Assuming 30% reduction of sunlight for 3.2m spacing and 10-20% reduction of sunlight for 6.4m spacing; expected yield of crops is supposed to be 70-80% of normal yield
• Increased land productivity by 45-70%
• With 6.4m spacing - 70% incident radiation; 3.2m spacing - 50% incident radiation available to crop
• Plant relative yield assumed to be 0.7 and 0.9 for 3.2 m and 6.4 m

Objective: Evaluate the impact on water use for residential agrivoltaics and typical roof-mount residential solar panels

• Ascertain water use, temperatures, power production of PV panels for agrivoltaics and a typical roof-mount installation
• Less irrigation requirement for agirovltaic vs control configuration
• Weights and leaf count lower for agrivoltaic system
• Roof-mount PV moduels have higher temperature - 3.6% decrease in power
• 19% drop in maximum air temperature and 17% for soil temperature
• 328g of lettuce under full sun vs 167g for agrivoltaic
• No. of leaves - 53.6 vs 31.1 while leaf length 5.9 vs 6.9 for agrivoltaics system

France:

• Maximum of 10% reduction in yield
• Maximum of 40% land coverage through PVs

https://www.pv-magazine.com/2024/04/09/france-issues-new-rules-for-agrivoltaics/

https://www.legifrance.gouv.fr/jorf/id/JORFTEXT000049386027

Italy:

• 70% of surface area of the plot must be dedicated to agricultural activity
• Total area covered by the modules - 40% max
• Minimum 60% of electrical output compared to a standard PV system

https://www.pv-magazine.com/2022/07/05/italy-publishes-new-national-guidelines-for-agrovoltaic-plants/

Germany:

• Land loss due to construction of AV system: up to 15% max
• Min 66% yield as compared to control

Agri-photovoltaic systems – Requirements for primary agricultural use English translation of DIN SPEC 91434:2021-05