Photovoltaic Greenhouse Research Articles

Luminescent Solar Concentrators for Greenhouse Applications Based on Highly Luminescent Carbon Quantum Dots

Carbon quantum dots (CQDs) are promising luminophores for luminescent solar concentrators (LSCs) in transparent photovoltaic greenhouse covers due to their high ultraviolet (UV)‐light absorption coefficient, which is vital for plant growth. Herein, high quantum yield (75%) and large Stokes shift (0.706 eV) CQDs are synthesized by a simple, fast, cheap, and mass scalable method. A comprehensive study on the LSC engineering is carried out. Thin layers of CQDs with different concentrations of 1, 3, and 5 wt% and different number of layers (1–5) are coated on glass and poly(methyl methacrylate) (PMMA) waveguides, sized 5 × 5 × 0.6 and 15 × 15 × 0.6 cm3. The best performing single‐layer LCS exhibits power conversion efficiency (PCE) and optical efficiency as high as 1.6% and 6.5%, respectively (LSC size 5 × 5 × 0.6 cm3), and 1.19% and 3.27% (LSC size of 15 × 15 × 0.6 cm3), respectively. Over 90 days, stability tests show a 2% PCE decrease. Tests on a small‐scale greenhouse model demonstrate that transparent photovoltaic LSC roofs not only produce electricity but also control temperature inside the greenhouse. Hence, CQD‐based LSCs synthesized by the scalable method can be used in commercialization of transparent greenhouses photovoltaic covers.

Improving tomatoes quality in the Sahel through organic cultivation under photovoltaic greenhouse as a climate change adaptation and mitigation strategy

Climate change negative impacts on food production systems have forced large scale food producers to make available less healthy products. Although available on the markets, tomatoes are no more tasting as they used to be and providing fewer nutrients compared to then. This study investigates and compares the quality and yield of organic tomatoes (Solanum lycopersicum) produced in an insect net covered photovoltaic greenhouse against ambient production. Plant’s physical characteristics were measured, yields and nutrient content were found at harvest, and environmental conditions (temperature, relative humidity, solar irradiance and CO2) were recorded. Plants grew as high as 160 cm inside the greenhouse under an average afternoon temperature of 30.71 °C and a vapor pressure deficit (VPD) of 1.88 kPa against outside plant growth of 72 cm height under averages of 36.04 °C and 3.05 kPa. Although, inside greenhouse tomatoes were physically more attractive and firm with two times healthier tomatoes (98%), 52.39% higher content in protein, 13.31% more minerals and 13.19% more dry matter than outside tomatoes, the yield from outside environment was 4.57 times higher than that of inside due to probably the used crop variety adapted to the harsh climate. Using a crop variety optimum for greenhouse, increasing ventilation and using better fertilizers with enough irrigation could help increase productivity while keeping high fruit quality inside the greenhouse, leading to healthier fruits for food security in the Sahel.

Solar irradiance prediction with variable time lengths and multi-parameters in full climate conditions based on photovoltaic greenhouse

Photovoltaic power generation can provide energy for greenhouses and achieve high quality and high yield of crops. In reality, solar irradiance is fluctuating and intermittent. Thus, the key to ensure efficient photovoltaic power use under greenhouse environmental conditions is to provide an accurate prediction of solar irradiance. Yet, currently studies on irradiance prediction in terms of the variable time lengths, multi-parameter and full climate conditions are rather limited. To improve the comprehensive performance of the prediction model, this paper proposes models of irradiance time series prediction such as Pyraformer, Informer, Transformer and TimesNet. Those models were tested based on the synergistic combination of weather conditions (WC), sunshine time accumulation (STA/h), instantaneous total irradiance (ITI/(W/m2)) and irradiance daily accumulation (IDA/(MJ/m2)). The model performance was rigorously evaluated with 9 prediction lengths, 5 training days, 4 seasons and 5 days for 9 weather conditions. The results showed that the Transformer model had the best overall prediction performance for STA, ITI, IDA and WC at different time steps of 10 min to 24 h. All models were suitable for predicting time series within 1 h. However, TimesNet model was not suitable for predicting time series with steps outside 1 h. On the other hand, by using the sun combination dataset, the Transformer model had the best performance at a time step of 10 min. The mean absolute error (MAE), mean-square error (MSE), root mean squared error (RMSE) and coefficient of determination (R2) of ITI were 0.118 W/m2, 0.059 W/m2, 0.243 W/m2 and 93.9 %, respectively. When exploring the minimum dataset, with the increase of data samples, the prediction effect of TimesNet showed an increasing trend. While, Transformer had the best prediction effect for the dataset with one year of use. When exploring seasonality, Pyraformer model had the best prediction effect on winter and summer, and TimesNet had the best prediction effect on autumn and spring. Local prediction of 9 climate conditions showed that the effects of snow and dust storm were not ideal. The research results showed that the characterization factors that were closely linked to irradiance. The prediction scheme proposed in this paper combined the advantages of different time steps, different factor combination datasets, different data volumes and seasonality, which greatly improves the generalization ability of the model. This study can provide a reference for irradiance prediction and more refined management of photovoltaic (PV) greenhouse.

Experiment on the Uniformity of Internal Lighting in Zigzag Photovoltaic Greenhouses by Grating Plates

As one of the main projects of facility agriculture promotion, the PV (photovoltaic) greenhouse has the problems of PV power generation competing for light with crop production, strong indoor chiaroscuro, and uneven light distribution. The internal light uniformity is tested by a zigzag greenhouse model to compare the light transmission effects of different light-transmitting materials applied to PV greenhouses. Altogether, 20 line/inch 3 mm and 30 line/inch 3 mm, 40 line/inch 2 mm, 25 line/inch 4 mm grating plates and 2 mm and 3 mm thick ordinary glass were used as light-transmitting components, and the light intensity and light uniformity in the greenhouse were the measurement indicators. The results show that the use of grating plates as covering material can improve the light intensity at the intersection of light and dark, but the overall light transmittance is not as good as glass because it is plastic, which ages easily with low light transmittance. It can also improve the use of land under the shade of PV modules to provide a better growth environment for crops. The test results show that using grating plates can maximize the light intensity of the greenhouse and solve the problem of uneven distribution of light inside the greenhouse caused by obstruction of PV equipment and greenhouse framework. In sunny weather, the light intensity in three rows of the measurement points at the north side in the greenhouse is greater than 20,000 Lx, and the light environment in other areas is between 5000 Lx and 20,000 Lx, which is suitable for planting shade-loving crops.

Design and Performance Evaluation of a Photovoltaic Greenhouse as an Energy Hub with Battery Storage and an Electric Vehicle Charger

This work presents a photovoltaic greenhouse’s design and performance evaluation as an energy hub in modern agriculture that integrates battery energy storage, an electric vehicle charging station, and non-controlled loads. The greenhouse roof comprises 48 semi-transparent photovoltaic panels with nominal transparency of 20% and 110 W capacity. The control of the photovoltaic greenhouse as an energy hub was approached as an optimization problem with the aim of minimizing the energy purchased from the grid. The simulation results indicate that the system is capable of balancing power transactions within the microgrid, thus enabling electromobility and, at the same time, achieving an average energy saving of up to 41%. Furthermore, it was found that the case of slow charging of the electric vehicle at night was less demanding on the battery system than fast charging during the day in terms of abrupt power transitions and average state of charge of the battery system, 61% vs. 53%, respectively. Empirical results also demonstrated the negative impact of soiling generated by agricultural activity on the performance of solar panels. For a period analyzed of three years, an average annual production loss of 6.8% was calculated.

Coordinated scheduling of photovoltaic greenhouse energy based on PBFT consensus mechanism

Coordinated scheduling of photovoltaic greenhouse energy based on PBFT consensus mechanism

Revolutionising Energy Generation for Agriculture Utilization in Malaysia: Photovoltaic Greenhouse Concept

Malaysia is a fortunate country graced by abundant sunlight, potentially having success in the application of photovoltaic (PV) powered greenhouses to safeguard food security. This research seeks to develop a design basis for PV greenhouse suitable for application in Malaysia. The motivation behind this research arises from the fact that while there have been studies on the application of PV greenhouses globally, most of them have focused on Europe, the Mediterranean, and Japan. The research will include two experimentalprototypes and one control prototype, all featuring identical mono-span roof PV greenhouses with a 15° tilt angle and E-W orientation which has been determined based on literature review. For stage 1 of the research, the prototypes will differ in terms ofthe PV array arrangements on the roof; whereas in stage 2, PV panels fitted with V-Trough Solar Concentrators will be utilized instead of ordinary PV panels. By filling the research gap by exploring the potential of PV greenhouses in Malaysia, the outcomeof this research will contribute to the development of a design basis for PV greenhouses in Malaysia, revolutionising photovoltaic-powered modern agricultural technology.

Energy performance assessment of photovoltaic greenhouses in summer based on coupled optical-electrical-thermal models and plant growth requirements

Photovoltaic (PV) greenhouses are widely used to regulate internal irradiance and air temperature to create optimal climatic conditions for plant growth. Therefore, comprehensive multidomain energy models of PV greenhouses are more likely needed to improve the system performance. However, few studies investigate optical-electrical-thermal characteristics and PV greenhouse evaluation indicators based on crop growth requirements. The aim of this work is to develop coupled optical-electrical-thermal models to assess the energy performance of the PV greenhouse with different PV roof coverage ratios during the summer months. In addition, the models of photosynthetically active radiation (PAR) and net photosynthetic rate (PN) are presented based on the irradiance and temperature of the PV greenhouse to evaluate the dynamic response of crops to interior climate conditions. The models are validated with experiments on the PV greenhouse in Kunming, with a total area of 26.25 m2. The electricity supply and demand systems include PV modules (3.285 kWp), a battery bank (24 kWh), an air–water heat pump (AWHP), and spray combined with fan cooling. Two cooling scenarios are analysed and compared by varying the PV module coverage ratio. Scenario 1 (S.1) is AWHP cooling, and scenario 2 (S.2) is spray combined with fan cooling. The optimum interior temperature and PAR of the PV greenhouse are 22 °C and 300 μmol·m−2·s−1, respectively. The simulations indicate that if the proportion of the PV layout on the greenhouse roof is greater than 20%, the year-round PAR inside the greenhouse will be below the threshold value of 550 μmol·m−2·s−1 at which the strawberry PN is saturated. For every 10% increase in PV roof coverage, the interior air temperature decreases by 0.02–0.56 °C corresponding to a daily cooling load reduction of 0.45–1.02 kWh/d, while the PV generation increases by 1.7–3.19 kWh/d and the maximum electricity consumption of S.1 and S.2 drops by 0.66 kWh/d and 0.52 kWh/d, respectively. Moreover, the high self-consumption-sufficiency balance (SCSB) values show that the PV and battery sizes are 2.22–2.78 kWp (40–50% coverage) and 15.72–15.75 kWh for S.1, and those in S.2 are 1.11–1.67 kWp (10–30% coverage) and 0.66–3.22 kWh. The coefficient of performance (COP) of the system reaches a maximum of 0.45–1.12 at 40% coverage in S.1 and 1.88–3.01 at 10–30% coverage in S.2. When the PV module coverage is 40% in S.1, the levelized costs of electricity (LCOE) and levelized costs of cooling (LCOC) are the lowest at 0.0760USD/kWhel and 0.0693USD/kWhc. Similarly, the lowest LCOE and LCOC of S.2 are 0.0306USD/kWhel and 0.0210USD/kWhc, as the PV module coverage is 30%. The study will be beneficial for applying photovoltaic modules, battery banks, and cooling technologies in the greenhouse, especially considering the dynamic crop response to internal climates and the energy performance assessment.

TECHNICAL AND ECONOMIC ANALYSIS OF COMMERCIAL PROSUMER 30 KW + CHARGING STATION FOR PLUG-IN ELECTRIC/HYBRID CARS 44 kW CASE STUDY: ROMANIA

The support of prosumers in the countries of the European Union has registered significant growth, especially regarding the energy produced from photovoltaic panels in households or in commercial spaces after 2020. Romania will promote the distributed generation from renewable sources with installed power between 3 kW and 100 kW, the on-grid installations being subsidized through the financial support of the Environmental Fund Administration (3 kW for residential prosumers) with ,,photovoltaic green house,, program and Ministry of Economy, Energy and Business Environment with the ,,Electric Up,, program (between 27 kW - 100 kW power with recharging stations of at least 22 kWp for electric and hybrid electric vehicles for commercial prosumers). This paper proposes an analysis of a commercial prosumer with a specific case study in north Dobrogea in Romania, comprise of a comparative analysis for an integrated 30 kW comercial user with 44 kW charghing station for electric and hybrid electric vehicles installed on the ground, in order to reduce the energy consumption with a management system for the optimal coordination of the energy to the owner's need, also to see the rentability of the system when it's a comercial user and the own consumption is higher during the day. The project applies to Romanian legislation and can be used for similar projects considering that in coming years these types of systems will appear.

A Case of Interdisciplinary Fusion under Dual Carbon Goal: Coordinated Carbon Reduction with Greenhouse Photovoltaics and Electric Vehicles

Building a new type of power system is an important guarantee to support China’s “dual carbon” goal. Due to the inseparable relationship between industrial and agricultural production and electric energy utilization, there must be interdisciplinary integration to achieve the goal of “dual carbon”. The disciplines of horticulture and electric power are taken as examples in this paper to analyze the feasibility of carbon emission reduction through coordinating agricultural photovoltaic (PV) greenhouse and electric vehicle (EV) energy storage. Firstly, the mechanism of carbon emission difference caused by electric energy supplementing during EV charging is analyzed. Secondly, in the context of the contradiction between the reduction of battery life caused by discharging (increasing carbon emission) and the increase in PV output consumption by orderly charging and discharging (reducing carbon emission), an optimization model for the synergistic operation of EV clusters and greenhouse PVs (with the objective of minimizing carbon emissions) is proposed. Finally, the effectiveness of the proposed model is verified through simulation cases. The energy storage characteristics of EVs is capable of realizing the transfer of PV power generation in the time dimension, and the coordinated operation of greenhouse PVs and EVs’ charging and discharging can effectively reduce carbon emission during the EV operation period. In a typical summer scenario of PV output, the carbon emission of EVs in V2G (vehicle to grid) mode was reduced by 69.13% compared to disorderly charging. It is shown that the adequacy of PV generation and the orderly dispatching of the charging and discharging of EVs are the key factors in reducing carbon emission throughout the life cycle of EVs.

Worldwide Research Trends in Agrivoltaic Systems—A Bibliometric Review

An agrovoltaic system combines agricultural crop production and energy production in the same place, emphasizing the dual use of land. This article provides a bibliometric analysis of agrivoltaic topics based on publications indexed in SCOPUS, in which either economic assessments of agrivoltaics, agrivoltaic systems for crops and livestock animals, photovoltaic greenhouse and agrivoltaics with open field are discussed, or its ideas are used to analyze certain locations. A bibliometric analysis was conducted using the SCOPUS database. Multiple bibliometric tools, such as R Studio and Biblioshiny, were applied to analyze data for this study. Finally, 121 relevant articles were obtained and reviewed. The results show that the focus topic is a brand-new research area, with the majority of relevant scientific publications concentrated in the last three years, and with much ongoing research. This is why AV-specialized scientific conferences might be the best place to get relevant and up-to-date information, with the highest number being offered in the USA and China. A typical trend in recent years has been researched, focusing on different agricultural aspects. The research results show that scientific publications in recent years mainly focus on short-term predictions, there is no recognized evaluation standard for various prediction analyses, and it is difficult to evaluate various prediction methods so far.

Collaborative Optimization of PV Greenhouses and Clean Energy Systems in Rural Areas

As an important infrastructure supporting rural development, an integrated energy system plays an irreplaceable role in China's rural revitalization strategy. The deployment of rural energy projects is an effective way for rural areas to achieve double carbon goals and accelerate agricultural modernization. Based on the actual rural energy systems in northern China, this paper takes the rural energy system with photovoltaic greenhouses as the research object. Both the agrometeorological and energy meteorological models are established considering the meteorological sensitivity of agricultural production and photovoltaic generation. We propose a novel method for optimizing the collaboration between photovoltaic greenhouse load control and rural energy systems. The combined coordination model of agriculture and energy networks is established, and the combined model involves carbon, electrical energy, and thermal energy. Supplemental greenhouse lighting and greenhouse heating consume most of the energy and are finely modeled with focused attention on photosynthesis. Finally, a real-world 47-bus distribution network and three photovoltaic greenhouses in northern China are simulated as an analytical example. The simulation results showed that by using the proposed optimization method, a 3996 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> greenhouse with a 25% photovoltaic coverage ratio can save 15% on energy costs.

High‐Efficiency Semi‐Transparent Organic Solar Cells Using Pentacyclic Aromatic Lactam‐Containing Terpolymer Strategy for Eco‐Friendly Greenhouse Application

Semitransparent organic solar cells (ST‐OSCs) offer unique features such as spectral tunability and see‐through function, giving them great potential in photovoltaic (PV) agriculture. However, the combination of sufficient average visible transmittance (AVT) and high power conversion efficiency (PCE) with eco‐friendly device fabrication has always been a key issue. Herein, a simple but effective strategy by incorporating pentacyclic aromatic lactam acceptor unit (TPTI) in copolymer donors for toluene processed high‐efficiency ST‐OSCs is performed. The comparisons between D18‐ and DEH‐X‐based ST‐OSCs demonstrate the effect of TPTI inserting on the polymer main skeleton can not only lower the energy level, improve the processability in nonhalogen solvent, tune the ideal morphology for efficient charge dissociation, but also control a photon transport window suitable for plant absorption. Therefore, the resulting OSCs processed with toluene exhibit a PCE of 14.6% with an AVT of 22%, which represents one of the highest values for ST‐OSCs made from nonhalogenated solvents. What's more, it is found that plant growth under ST‐OSCs filtered light is comparable with that under natural light. Herein, a guide for developing high‐performance ST‐OSCs is provided and the prospect of ST‐OSCs for green manufacturing PV greenhouse application is demonstrated.

Simulation and Experimental Study of Light and Thermal Environment of Photovoltaic Greenhouse in Tropical Area Based on Design Builder

In order to study the adaptability of photovoltaic greenhouses to climate in tropical areas, a photovoltaic greenhouse model (photovoltaic panel coverage rate: 76.9%) was built in this study according to a 1:1 proportion. The distribution law of the indoor illuminance, temperature, and humidity were studied simultaneously in the photovoltaic greenhouse by actual measurements and simulation. The filed data are shown as follows: (1) Illuminance: in limited rain winter, the average illuminance and light transmittance were 7.02 kLux and 25.77%, respectively (10:00–16:00); but in different weather conditions during summer, the average illuminance and light transmittance were 15.47 kLux and 32.35%, respectively (9:00–16:00). (2) Temperature and humidity: the indoor temperatures of the greenhouse were between 22.1 and 29.3 °C in limited rain winter, with a relative small temperature difference between indoor and outdoor environments; the relative humidity values were between 69% and 97%; but in summer, the temperatures at all indoor test site were higher than outdoor sites, with an average temperature difference of 2.7 °C and relative humidity values between 46% and 94%. According to the simulation by Design Builder, the average light transmittances were 33.09% in winter and 37.54% in summer, the temperature difference between winter and summer was less than 1 °C, and the relative humidity decreased with the increase of temperature, which basically coincided with the filed data. The results of the analysis showed that the illuminance, temperature and humidity of the photovoltaic greenhouse can satisfy the production requirements of shade-enduring and neutral crops. At the same time, by comparing the illumination, temperature and humidity of the photovoltaic greenhouse with that of an ordinary greenhouse, the former had good adaptability to climate in tropical areas, which can achieve the goal of photovoltaic generation and agricultural production synchronously.

Addressing virtual asymmetry of photovoltaic greenhouse with comprehensive AOMH based SWAPP approach

Photovoltaic based greenhouse system suffers from the issue of virtual asymmetry despite of considering the photovoltaic modules with symmetric characteristics and matched specifications. Virtual symmetry in such photovoltaic applications results in mismatching losses. This paper aims to address the issue of virtual asymmetry specifically to photovoltaic arrays inclined in opposite directions on a general-purpose hut type structure in a photovoltaic based greenhouse. A prototype model is designed and developed, using a unique add-on modular hardware with its soft switching adaptive power profile approach along with maximum power point tracking implementation to address the issue of degradation of operational efficiency of oppositely inclined PV panels. Due to the proposed synthesis of add-on modular hardware along with soft switching adaptive power profile approach and maximum power point tracking; it is a unique photovoltaic power optimizer, extracting enhanced energy with a stabilized common DC bus. Further, photovoltaic source capacity is matched against varying load from few watts to the full rated load capacity, as per scheduled operations of airflow, photosynthetically active radiation for improved photosynthesis, climate control, and backup battery energy source. The third intangible benefit is minimized thermal loss with an added margin of safe operating area for each power device, resulting in the maximized mean time before failure. As per observation, the additional photovoltaic energy gain under virtual asymmetrical conditions is 8.97–11.21% with overall system efficiency as 64.90–92.04% having a variable load from 10 to 100%. The proposed work may be scaled up for a bigger PV-GH size.

Analysis of the Viability of a Photovoltaic Greenhouse with Semi-Transparent Amorphous Silicon (a-Si) Glass

For decades, society has been changing towards an energy mix that enhances the use of renewable sources and a more distributed generation of energy. The agricultural sector is included in this trend, which is why several studies are currently being carried out focused on the use of solar energy in greenhouses. This article aims to demonstrate the viability of a greenhouse that integrates, as a novelty, semi-transparent amorphous silicon photovoltaic (PV) glass (a-Si), covering the entire roof surface and the main sides of the greenhouse. The designed prototype is formed by a simple rectangular structure 12 m long and 2.5 m wide, with a monopitch roof, oriented to the southwest, and with a 35° inclination. The greenhouse is divided into two contiguous equal sections, each with an area of 15 m2, and physically separated by an interior partition transparent wall. The surface enclosure of one of the sections is made of conventional glass, and the one of the other, of PV glass. How the presence of semitransparent PV glass influences the growth of horticultural crops has been studied, finding that it slightly reduces the production of vegetal mass and accelerates the apical growth mechanism of heliophilic plants. However, from a statistical point of view, this influence is negligible, so it is concluded that the studied technology is viable for horticultural production. The energy balance carried out indicates that the energy produced by the PV system is greater than the energy consumed by the greenhouse, which shows that the greenhouse is completely viable and self-sufficient for sites with the adequate solar resource.

Climate assessment of greenhouse equipped with south-oriented PV roofs: An experimental and computational fluid dynamics study

The present study was undertaken to better understand the effect of the shading induced by south oriented photovoltaic panels on the distributed climate and plant activities in a mono-span greenhouse using CFD tool. The climate behavior during summer and winter days inside a greenhouse integrated with PV panels on the roof and a reference was assessed. Solar radiation distribution, wind velocity, relative humidity, and ambient temperature from the two greenhouses were presented and energy production and plant activity parameters were evaluated. The greenhouse equipped with photovoltaic panels provides more favorable climatic conditions during summer season. Therefore, results of the paper can be useful for farmers in the Mediterranean area to contain the ability level of this innovative photovoltaic greenhouse crop and to perceive if it can perform a balance between yield crop and PV electricity production. Results showed that PV panels can produce around 55 W/m2 for the cultivation period of January. During a summer day, the solar radiation of the PV greenhouse was lower than that of the reference greenhouse and exceeded 115 W/m2, and the difference between the inside and the outside reached 220 W/m2. The annual solar energy of the photovoltaic panel was around 5054.4 kWh. Accordingly, the shading plays a positive effect on plants in decreasing temperature due to the reduced thermal load of the sun inside the greenhouse. In addition, the payback period of PV system was found to be less than 6 years.

用于农业大棚的光伏阵列最大功率点跟踪算法研究

In order to enhance the utilization of solar energy in photovoltaic greenhouse, this paper takes the optimization strategy of photovoltaic array's maximum power point tracking algorithm as research object. According to the changing rule of the slope of photovoltaic array's output P-U curve, this paper proposes a new variable-step conductance increment method to track the maximum power point. When the working point is located on the left side of maximum power point, the logarithmic function value of curve’s slope is adopted as the voltage step to adjust the position of working point. When the working point is located on the right side of maximum power point, the exponential function value of curve’s slope is adopted as the voltage step to adjust the position of working point. Through the MPPT modelling and simulation in MATLAB/Simulink and the corresponding circuit test, the result shows that comparing with the traditional variable-step conductance increment method, the proposed algorithm can find the maximum power point faster, and it can effectively reduce the power loss caused by step oscillation in the searching process, which achieves the goal of enhancing conversion efficiency of photovoltaic power generation.

Agricultural sustainability estimation of the European photovoltaic greenhouses

Abstract The integration of the photovoltaic (PV) energy in the greenhouse farm has raised concerns on the agricultural sustainability of this specific agrosystem in terms of crop planning and management, due to the shading cast by the PV panels on the canopy. The PV greenhouse (PVG) can be classified on the basis of the PV cover ratio (PVR), that is the ratio of the projected area of PV panels to the ground and the total greenhouse area. In this paper, we estimated the yield of 14 greenhouse horticultural and floricultural crops inside four commercial PVG types spread in southern Europe, with PVR ranging from 25 to 100%. The aim of the work is to identify the PVG types suitable for the cultivation of the considered species, based on the best trade-off between PV shading and crop production. The daily light integral (DLI) was used to compare the light scenarios inside the PVGs to the crop light requirements, and estimate the potential yield. The structures with a PVR of 25% were compatible with the cultivation of all considered species, including the high light demanding ones (tomato, cucumber, sweet pepper), with an estimated negligible or limited yield reduction (below 25%). The medium light species (such as asparagus) with an optimal DLI lower than 17 mol m−2 d−1 and low light crops can be cultivated inside PVGs with a PVR up to 60%. Only low light demanding floricultural species with an optimal DLI lower than 10 mol m−2 d−1, such as poinsettia, kalanchoe and dracaena, were compatible inside PVGs with a PVR up to 100%. Innovative cropping systems should be considered to overcome the penalizing light scenarios of the PVGs with high PVR, also implementing LED supplementary lighting. This paper contributes to identify the sustainable PVG types for the chosen species and the alternative crop managements in terms of transplantation period and precision agriculture techniques, aimed at increasing the crop productivity and adaptability inside the PVG agrosystems.

The Effect of Different Levels of Shading in a Photovoltaic Greenhouse with a North–South Orientation

Photovoltaic greenhouses have been claimed to be a solution to cover the energy demand of the protected crops sector. Thus, there is a need to know what is the maximum percentage of shading produced by roof-top photovoltaic panels that does not affect crop yields. The present study analyzes the effects of increasing percentages of shading in a greenhouse tomato crop located in the southeast of Spain. For this study, photovoltaic panels have been simulated with opaque sheets located in the roof-top of a north–south oriented greenhouse. Three treatments of top roof shading percentage (15%, 30% and 50%) where studied and compared with the control treatment without shading (0%). During the study, parameters registered were radiation, temperature, pH and electric conductivity of the substrate, crop yields and fruit quality. Results of the analysis show that higher percentages of shading in the roof-top of greenhouses reduce so much available radiation for the crop causing a reduction in the yield and fruit quality, even in Mediterranean areas where radiation is not a limiting factor.