Greenhouse Roof Research Articles

Environmental Sustainability of Greenhouse Covering Materials

The fundamental objective of the review article was to explore the ecological sustainability of greenhouse covering material based on the following themes; considerations for greenhouse materials, properties of polymers and glass, additives, fillers, stabilizers and reinforcements, performance, Ultraviolet (UV) transmittance, phase change materials (PCMs), and environmental sustainability. A comparison of various polymers (polyvinyl chloride (PVC), acrylic, D-polymer, Linear low-density polyethylene (LLDPE), polyolefins), and silica glasses illustrated that each type of greenhouse cladding material has its unique merits and limitations. The performance of silica glasses, PVC, polyolefins was influenced by weather, greenhouse design, plant under cultivation, percentage UV transmittance, incorporation of additives and stabilizers, reinforcements, and integration of photovoltaic panels into the greenhouse roof among other factors. Polymers can be customized to achieve 0%UV transmittance, slow-insecticide release, and anti-microbial properties. In contrast, glass materials are preferred based on suitable photosynthetically active radiation (PAR) transmittance and near-infrared (NIR) reflection and less risk of photo-oxidation. From an ecological perspective, polymers can be recycled via mechanical and chemical recycling, closed-loop cycling, and polymerization of bio-based feedstock. However, post-consumer plastic films do not possess the same optical and energy properties as virgin polymers. The combined benefits of different polymers suggest that these materials could be adopted on a large scale over the long-term.

Effects of greenhouse roofs on thermal comfort, behavior, health, and finishing performance of commercial zebu steers in cold arid environments

The aim of this study was to determine the effects of two housing systems (thermal plastic greenhouse roofs—PGR—vs. without roof—PWR) on health, welfare, and finishing performance of zebu steers in cold arid environments. A total of 880 animals were included in the study; these were divided into two independent studies. For the first study, 260 steers were used (effect on steers' welfare), and for the second study, 620 steers were used (effect on steers' performance). Steers in the PWR treatment showed a trend of standing during 12:00 to 14:59 h, which was considered the hottest period of the day and the steers that were standing showed a trend for feed intake. On the other hand, the steers in the PGR treatment showed a trend of lying down (P < 0.001) and ruminating (P = 0.031) during the same period of the day; in addition, more steers were drinking in PGR than in PWR treatment. Survival analysis of physical health indicated that the number of healthy steers decreased as the number of days increased; more sick steers were observed in PWR treatment (P < 0.05). Finally, steers in PGR achieved different (P < 0.001) final body weight (599.7 ± 46.4 kg) compared with steers in PWR treatment (569.0 ± 31.6 kg). The steers in PWR showed higher feed intake (P < 0.001); nonetheless, the steers in PGR treatment showed higher average daily gain (P < 0.001) and higher feed conversion efficiency (P < 0.001). Under the winter conditions where the temperatures fluctuated from a high of 33.9°C to a low of −2.7°C, the use of thermal plastic greenhouse roofs demonstrated an improvement of steers’ welfare, health, the average daily gain and feed conversion efficiency.

A Photovoltaic Greenhouse with Passive Variation in Shading by Fixed Horizontal PV Panels

The traditional shading systems that greenhouses use cause some of the solar radiation that is reflected or absorbed to be lost and, therefore, not used by the plants under cultivation. An interesting solution to these problems is to position photovoltaic (PV) panels on the roofs of greenhouses. All of the photovoltaic greenhouses that have been realized in Mediterranean areas are characterized by a fixed position of the PV panels and excessive shading, especially in autumn and winter. The purpose of this study is to describe a prototype of a photovoltaic greenhouse with both fixed and horizontal PV panels that exploit the natural variation in the elevation angle of the sun’s rays during the year to allow for “passive” variation in shading. The considerable variation in the elevation angle of the sun’s rays (from 24.4° to 71.1°) results in a high variation in shading (from 39.4% to 72.6%), with the highest values in the summer months and the lowest values in the winter months. This trend is favorable for meeting the photosynthetically active radiation (PAR) needs of greenhouse plants. If the plants under cultivation require more solar energy, it is necessary to increase the distance between the panels. We implement a specific mathematical relationship to define the precise distance to be assigned to the photovoltaic panels on the roof pitch.

Morphology, yield and quality of greenhouse tomato cultivation with flexible photovoltaic rooftop panels (Almería-Spain)

Flexible photovoltaic panels are an option to generate renewable energy that could be compatible with the production of greenhouse crops, especially in warm sunny countries. The aim of this study was to evaluate, during two growing seasons, the effect of shading caused by flexible photovoltaic panels mounted on the greenhouse roof on tomato plant morphology and fruit yield and quality. This study was conducted during two growing seasons in a commercial greenhouse for tomato production. Two photovoltaic panel arrays placed on the greenhouse roof were analysed. Both occupied 9.8% of the cover. The parameters studied were PAR, plant morphology, crop yield and fruit quality. The results show that the small reduction in PAR caused by flexible photovoltaic panels on the roof did not affect the total and marketable yield; plant morphology; number of flowers per branch; and fruit colour, firmness and pH. However, the fruit diameter decreased, without affecting the yield (kg·m−2). Both flexible photovoltaic panel arrays on the greenhouse roof produced a similar effect on plant morphology, crop yield and fruit quality.

Experimental and numerical investigation of the thermal performance of evaporative cooled greenhouses in hot and arid climates

The controlled microclimate of greenhouses is vital for producing quality yield. This paper investigates the thermal performance of an evaporative cooled greenhouse operating in Qatar. Three design factors affecting the greenhouse thermal performance were assessed, namely the greenhouse geometry, operational parameters, and its geographical location. Geometrical parameters include induction fan elevation, roof shape, and aspect ratio. Operational parameters refer to the air flowrate. The greenhouse location dictates the incident solar intensity that was studied. Computational Fluid Dynamics (CFD) was used to model a typical ASHRAE compliant greenhouse. The simulation results were validated using measured data of a greenhouse inner air temperature, relative humidity, and the global incident solar radiation, showing good agreement. Simulation results showed that induction fans located at or below the crop height resulted in lowering the average temperature of the greenhouse. Doubling of the greenhouse ventilation rate from 20 ACH to 40 ACH further decreased the greenhouse air temperature. Temperature rise due to high incident solar radiation is reduced by increasing the ventilation rates. The uneven span greenhouse roof shape resulted in the lowest average inner temperature. For the same greenhouse floor area and volume, the effect of the aspect ratio showed negligible differences.

Greenhouse knockdown in Merauke

The farming method in Merauke Papua is conventional, therefore production is not maximized throughout the year. The purpose of this study was to build a household scale greenhouse that could be assembled. This research was an experimental and Action Research; the research phase including Knockdown greenhouse design, made greenhouses, greenhouse tested (transporting, assembling and installing and clearing). The results of the knockdown greenhouse structure research used a combination of iron pipe and hollow iron; the application was on the column pole/column using a 3-inch diameter iron pipe while for the roof and wall frame using 4 cm hollow iron 3 mm thickness. for foundations used pedestal/local foundations with a total of 18 foundations with dimensions of 27,000 m3 (30 cm x 30 cm x 30 cm). The knockdown greenhouse roof consists of 2, namely; 1). The rooftop used the used bottle roof cover material, 2). The lower roof used the Paranet/insect screen roof cover material. The installation and dismantling of the knockdown Greenhouse take + 2 hours 30 minutes, with time division: 1). + 45.40 minutes installer for greenhouse structure; 2). Thirty-five minutes installation of roof cover (used bottles) and; 3). Fifty minutes installation of the insect screen.

Performance analysis of radiation and electricity yield in a photovoltaic panel integrated greenhouse using the radiation and thermal models

The agricultural photovoltaic panel integrated greenhouse (PVIG) are attempted to improve the utilization of solar energy for sustainable agriculture. This study proposes a numerical method to predict the radiation distribution and the electricity yield of a PVIG throughout the year using 3D radiation model and thermal model. The radiation model is validated in a PVIG in the southeast of China with 36 rooftop PV panels of straight-line layout and the PV array covering 25% of the greenhouse roof area. According to simulation of conventional greenhouse and PVIG with straight-line (La), crisscross (Lb) and checkerboard (Lc) PV panels’ layouts, the performance of different PVIG is evaluated in terms of the non-uniformity of the radiation distribution, the radiation intensity and the electricity yield of PV panels. The non-uniformity of the hourly radiation under the La layout is not much different from the layout Lb and Lc, and the cumulative weekly radiation under the layout of La is increased by 8.3% and 12.7% in the experimental PVIG, respectively. The thermal model of PV panels mounted on the greenhouse roof is developed to accurately predict the PV electricity yield, considering the impact of greenhouses and external environments on PV panels. In contrast to the layouts of La and Lb, the annual electricity yield of PV panels with the layout of Lc raises by 3.2 and 2.2 kWh m−2 respectively. Compared with conventional greenhouse, the distribution and intensity of cumulative weekly radiation are not significantly affected by the optimal PV array covering 25% of the greenhouse roof area. These results indicate that the 3D radiation model and thermal model can be used as an efficient tool to optimize the performance of PVIG.

Numerical and experimental analyses of a transparent solar distiller for an agricultural greenhouse

Solar distillers are the simplest desalination equipment used to produce fresh water using the most sustainable source of energy. In this research, a new fully transparent solar distiller is designed to be integrated into the roof of an agricultural greenhouse using the excess solar radiation to produce desalinated water for plant irrigation. A numerical technique is proposed to analyse the performance of the distiller. This technique couples a lumped model based on transient mass and energy balance equations for different components of the distiller with a computational fluid dynamics (CFD) model to simulate the flow, heat transfer, and phase change of humid air and water with a free surface inside the distiller. The predicted temperature variations of the glass and basin by the lumped model are used as boundary conditions for the CFD model to improve the accuracy of the water production estimations. The results of the lumped model and the coupled lumped–CFD model are compared with the experimental data from a transparent distiller test performed at Alexandria, Egypt. The same average daily efficiency of 12.4% for both the experimental measurements and the coupled lumped–CFD model is shown. The results of the validated numerical model indicate that the daily yield can be increased by approximately 22% by increasing the basin insulation. Additionally, the predicted maximum yield is 618.2 mL/day in August. Integrating transparent distillers into a greenhouse roof can provide 37.5% of irrigation water and reduce the power consumption of the greenhouse cooling system by 60%.

Experimental study on the effect of a novel water injected polycarbonate shading on light transmittance and greenhouse interior conditions

Direct entry of solar radiation through the covers into the greenhouse enclosure is the primary source of heat gain. The amount of radiation (or light) entering the greenhouse can be controlled by shading and/or reflecting the incident radiation. In this study, the effect of a novel shading technique which is named Water Injected Polycarbonate Shading (WIPS) was investigated. In this method to create shading, the ducts in between the two-layer polycarbonate sheet were used to pass and maintain a suitable liquid (e.g. water) flow to the roof of the greenhouse. However, the use of water does not cause any barrier for the light passing the greenhouse roof which can reduce plants photosynthesis. This is the most important parameter for shadings that has to be used in greenhouses. Due to the ability to absorb infrared radiation by water, the proposed shading system absorbs about 14% of the solar spectrum and hence helps greenhouse cooling, with less side effect on other solar spectrum and hence photosynthesis. The results of statistical analysis revealed that WIPS system can decrease greenhouse temperature in the range of about 1 to at most 3 °C at the peak of the ambient temperature. Also, using water in the WIPS shading does not create an obstacle to ultraviolet light. Comparison of mean with “t” test showed that there is a significant difference between the temperature and infrared light transmission in two greenhouses without shading and with WIPS greenhouse, at the 5% and 1% probability level, respectively. However, no significant difference in UV and visible light observed between the two greenhouses, implying shading performance of WIPS with no serious obstacle for photosynthesis.

Yield and quality of lettuce in response to the plant position in photovoltaic greenhouse

In recent years there has been an increasing spread of photovoltaic greenhouses, especially in southern European countries, due to the higher incentives recognized to solar photovoltaic (PV) panels integrated on the greenhouse roofs and/or to local laws which limit the photovoltaic systems on the ground. To maximize the income from the production of electricity, often solar panels cover 50% or more of the roof, but the shading caused by these elements on the growing surface seriously limits the productivity and affects crop development. In order to assess the effects of the spatial distribution of the solar radiation inside these structures on yield and quality of leaf vegetable crops, the response of lettuce, grown in two cycles (autumn and winter-spring), in an east-west oriented photovoltaic greenhouse with the 50% of the roof covered by PV modules was analysed. The influence of span orientation, plant position (under plastic or PV roof) and cultivar were analysed as experimental treatments in a split-split plot design with two replications. Total and marketable yield of the lettuce heads and some quality parameters (dry matter and nitrate content) were evaluated. A significant variability of the total and marketable yield due to the plant position and as consequence to the solar radiation distribution inside the structure during the growing cycle was observed. Furthermore, ranges and variability of the nitrate content of lettuce (expressed as NO(3) mg kg(‑1) of fresh weight) were affected by the plant position and harvest season. In order to maximize yield and quality of the crops, the arrangement of plant rows and transit areas, as well as the management of nutrition, should be optimized in relation to the shading caused by the PV roof during the growing cycle.

Influence of shading treatment on yield, morphological traits and phenolic profile of sweet basil (Ocimum basilicum L.)

We investigated the roles of different shading strategies on plant growth, antioxidant activity and phenolic profile of sweet basil (Ocimum basilicum L.), a widely used herb with culinary and medicinal properties. Sweet basil plants were cultivated in a commercial multi-span tunnel-greenhouse covered with an EVAC plastic film, shaded from solar radiation in five different ways: n. 1, by calcium hydroxide whitening; n. 2, installing up - or n. 3, under - the greenhouse roof, a PE-HD white reflective net with 36% shading factor; n. 4, installing up - or n. 5, under - the greenhouse roof, a PE-HD white reflective net with 58% shading factor. The remaining part of the greenhouse (n. 6 - control) was unshaded. In each trial, yield traits, antioxidant activity and contents of phenolics of sweet basil plants were assessed to evaluate the influence of the shading strategy on these parameters. The antioxidant capacity was evaluated by using three different in vitro assays: DPPH scavenging activity, reducing power (FRAP) and lipid peroxidation inhibition (BCB). To compare the data obtained by the different chemical methods, the relative antioxidant capacity index (RACI) was calculated. The yield was highest in unshaded plants. The control trial, in which the incoming solar radiation was filtered only by the film which covers the greenhouse, showed the highest RACI value (0.98), indicating that the antioxidant capacity was probably influenced by higher light and temperature conditions. Phenolic quantification, determined by HPLC-DAD, enabled to observe a correlation between the antioxidant power and the identified metabolites.

Rainwater Harvesting in Greenhouses Establishments and Use as Irrigation Water

Rainwater collection systems are an alternative water supply method that provides environmental and economic benefits according to traditional water supply methods in arid and semi-arid climates. Rainwater harvested in greenhouse roof by rain gutters can be used to irrigate and grow the plants cultivated in greenhouses. However, rain gutters and storage tanks in greenhouses should be of sufficient size to collect rainwater. Water consumption of plants in the greenhouse should be calculated correctly to determine the storage size in greenhouses. In this study, daily water consumption of tomatoes cultivated in greenhouses not regularly heated in Kumluca district of Antalya province is calculated according to FAO Penman Monteith method. Then, the storage capacity of the remaining part of the falling monthly rainfall used in the greenhouse was determined. As a result of the study, the amount of annual irrigation water harvested from rainfall in Kumluca district where total rainfall is 734.44 l/m2 was determined as 661.00 l/m2 based on rainfall factor of 0.9. In the period between September and June when single crop was grown in the year, the total amount of irrigation water needed by the plants in the not regularly heated greenhouse was calculated as 569.86 l/m2. Accordingly, it was determined that it is possible to meet all of the irrigation water to be provided to the plant with rainwater harvesting. Depending on the amount of rainwater harvest obtained, it was determined that the storage capacity of 0.40 m3/m2 in greenhouse is needed. In the study, it was determined that rainwater harvesting may contribute to the development of agricultural activities in areas suffering from water scarcity. Keywords : Greenhouse, Rainwater harvest, crop water requirement, Collection systems. DOI : 10.7176/JSTR/5-5-01

RAINWATER HARVESTING ON GREENHOUSE ROOF AND USE IN IRRIGATION

Rainwater collection systems are alternative water supply methods providing environmental and economic benefits compared to traditional water supply methods used in arid and semi-arid climates with water shortages. Rainwater harvested in greenhouse roof by rain gutters can be used to irrigate and grow the plants cultivated in greenhouses. However, rain gutters and storage tanks in greenhouses should be of sufficient size to collect rainwater. Water consumption of plants in the greenhouse should be calculated correctly to determine the storage size in greenhouses. The amount of annual irrigation water harvested from rainfall in Kirsehir province where total rainfall is 388.3 l/m2 was determined as 349.57 l/m2 based on rainfall factor of 0.9. Total amount of irrigation water needed by the plants in the unheated greenhouse between April and September for single crop cultivation was 568.33 l/m2. The results revealed that 61.49% of irrigation water needed for plants can be met by rainwater harvesting. In addition, 47.74% of the total water demand of plants in the heated greenhouse where crops are grown throughout a year can be met by rainwater harvesting. The storage capacities needed for unheated and heated greenhouses were determined as 0.21 m3/m2 and 0.30 m3/m2 depending on the amount of rainwater harvested. The results showed that rainwater harvesting may contribute to the improvement of agricultural activities in water-scarce regions.

Photothermal/day lighting performance analysis of a multifunctional solid compound parabolic concentrator for an active solar greenhouse roof

Currently, the excess light above a light saturation point cannot be harnessed for plant growth in conventional greenhouse covers. In this study, we developed a solid compound parabolic concentrator (CPC) cover for use in greenhouses to convert excess light into heat. Optical simulation software was used to track the sunlight at different incident angles over time. We also conducted experiments to determine the transmittance and heating power of the solid CPC coating under real weather conditions. The maximum instantaneous thermal efficiency and thermal energy of a single solid CPC cover plate were 32.2% and 353 W/m2, respectively. The simulation results were in good agreement with the experimental output power and the trend of the actual transmittance of the covering material. The transmittance of the covering material was low when the midday sun was intense, and the transmittance was relatively high in the morning and afternoon. The variation of red and blue light in the greenhouse with the spectrum was analyzed at the same time. Studies have shown that this new greenhouse covering material can better adjust the brightness, make the illumination in the greenhouse more uniform, and thus improve the thermal environment in the greenhouse. The heat pipes converted excess light into heat, thereby achieving comprehensive utilization of solar light and heat.

Increase of light transmission of a Venlo-type greenhouse during winter by 10%: a design study

During winter and at higher latitudes, natural light is the limiting factor for crop growth in greenhouses. The design of Venlo-type greenhouses in the Netherlands has not changed for many years, although recent developments of diffuse glass with anti-reflective coatings might necessitate alteration of the roof design for maximized light transmissivity during winter. Light transmissivity of a greenhouse, in general, is influenced by roof slope, gutter orientation, roof shape, dimensions, position and reflectivity of construction elements, screen installation, position and transmissivity of screen material, transmissivity and light-scattering pattern of the covering and the effect of condensation on the inner side of the covering material or screen. Using the ray-tracing model RAYPRO (Swinkels et al., 2001), the integral effect of all individual and combined measures on light transmission of the greenhouse at crop level was calculated. The results show that it is possible to increase light transmission by more than 10% with a novel greenhouse roof concept. Results of ray-tracing calculations for individual and combined measures are described in this paper. After identifying the roof concept with the theoretically highest increase in light transmissivity during winter in the Netherlands, economic feasibility and all constructional restrictions were taken into account in close cooperation with industrial partners. This has led to a novel roof design that was built as a demonstration greenhouse on a scale of 500 m2 in summer 2016 at Wageningen University & Research station in Bleiswijk. This “winterlight greenhouse” had resulted in a re-design of the traditional Venlo-type greenhouse roof, covering and screen.

Development of Low-cost Detachable Roof Greenhouse for Round the Year Cultivation of Tomato and Capsicum

Greenhouse is a well-established technology for crop cultivation or nursery growing under controlled, or partially controlled, condition. The major hindrance in its widespread adoption is construction cost and environment management. A low-cost detachable roof greenhouse was developed for round-the-year cultivation of tomato/capsicum. The temperature under the greenhouse during winter season (November-February) was 1-3 0 C higher than at open field condition due to greenhouse effect. The temperature during summer season (March-June) in the greenhouse was between 5-46 0 C, and was lower than the temperature (6-49 0 C) under open field condition. During rainy season (July-October), the temperature recorded were 9-38 0 C and 12-41 0 C, respectively, under greenhouse and open field condition. The light intensity and relative humidity in the greenhouse varied between 0.7-53.2 klux and 14-96 %, respectively.

Electrical Energy Producing Greenhouse Shading System with a Semi-Transparent Photovoltaic Blind Based on Micro-Spherical Solar Cells

An increasing population and limited arable land area endanger sufficient and variegated food supplies worldwide. Greenhouse cultivation enables highly intensive plant production and thereby enables the production of abundant fresh vegetables and fruits. The salient benefits of greenhouse cultivation are supported by ingenious management of crop environments, assisted by fossil fuel and grid electricity supplies. To reduce dependence on traditional energy resources, various studies have investigated exploitation of renewable energies for greenhouse environment management. Among them, solar photovoltaic (PV) technologies are anticipated to feed electrical energy to greenhouse appliances for microclimate control. This study proposes a venetian-blind-type shading system consisting of semi-transparent PV modules as blind blades based on micro-spherical solar cell technology to achieve greenhouse shading and electricity production concurrently. In response to the solar irradiance level, the PV blind inclination was altered automatically using a direct current (DC) motor driven by electrical energy generated by the PV blind itself. The PV blind was operated continuously during a five-month test period without outage. Moreover, the PV blind generated surplus electrical energy of 2125 kJ for blind system operations during the test period. The annual surplus energy calculated under the present experimental condition was 7.8 kWh m−2 year−1, suggesting that application of the PV blind to a greenhouse roof enables sunlight level control and electrical appliance operations in the greenhouse with a diminished fuel and grid electricity supply, particularly in high-insolation regions.

Performance of multilayered LDPE films used as greenhouse cover in semiarid climate

The low-density polyethylene films used for greenhouse roof were naturally weathered for 9 months in harsh climatic conditions (Tiaret region, Algeria). The changes in the mechanical properties have been measured by tensile and creep-recovery tests. The measurements were carried out for both monolayer and tri-layer films. The anisotropic character of the films is preserved during ageing. The improvement in the creep resistance via cross-linking for both monolayer and tri-layer films affects different deformations. The results revealed that the degradation performance of these new tri-layer films is found to be quite better than that of the monolayer film, with regard to the mechanical properties.

Rolled plastic film damage simulation considering surface roughness useful for greenhouse roof automatic ventilation

Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese greenhouse design is gaining popularity because of its automated rolled-up ventilation system that is integrated into the roof. However, due to the frequent movement of the roll-up system, the plastic film deteriorates rapidly and typically lasts for only three or four months. In order to better understand the film deterioration, we studied the mechanics involved at the point of contact between the film and the metal greenhouse frame. We found that film deformation and failure were closely related to stretching and creasing, and these processes were observed at the microscope level. In this paper, the plastic film damage was investigated through the rolling contact analysis focusing on the pipe surface roughness. We found that at the inside film surface the larger strain is caused by the pipe surface roughness. This larger strain generates the wave deformation of the film, crease and line scar whose number increases with increasing the roughness of the arch pipe. The effects of pipe coating and perforated film are discussed to prevent the film damage.

Analysis of materials used for Greenhouse roof covering - structure using CFD

Greenhouse is widely used to create a suitable environment for the growth of plant. During summer, high temperatures cause harm to the plant. This work calculates characteristics required to optimize the above-mentioned parameters using different roof structure covering materials for the greenhouse. Moreover, this work also presents a simulation of the cooling and heating system. In addition, a computer model based on Ansys Fluent has been using to predict the temperature profiles inside the greenhouse. Greenhouse roof structure shading may have a time-dependent effect the production, water and nutrient uptake in plants. An experiment was conducted in the emirate of Dubai in United Arab Emirates to discover the impact of different materials in order to have an optimal plant growth zone and yield production. These structures were poly ethylene and poly carbonate sheets of 2 different configurations. Results showed that poly carbonate sheets configuration of optimal thickness has given a high result in terms of yield production. Therefore, there is a need for appropriate material selection of greenhouse roof structure in this area of UAE. Major parameters and properties need to be considered while selecting a greenhouse roof structure are the resistance to solar radiation, weathering, thermal as well as mechanical properties and good abrasion resistance. In the present study, an experiment has been conducted to find out the material suitability of the greenhouse roof structure in terms of developing proper ambient conditions especially to minimize the energy lose by reducing the HVAC and lighting expenses. The configuration verified using the CFD, so it has been concluded that polycarbonate can be safely used in the greenhouse than other roof structure material having white or green colour.