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The greenhouse cultivation system in European countries represents one of the most energy-intensive sectors in the agriculture and agro-industry sector. In this regard, renewable energies represent an innovative solution to reduce energy costs and environmental impacts. Both, the energy demands and the economic aspects are analyzed with regard to the main energy users, i.e.: heating and cooling systems, lighting and pumping for irrigation. This work considers the use of solar photovoltaic and thermal energy. The use of semi-closed greenhouses is also considered.

In recent years, due to the circular economy, the use of green energy forms, such as biofuels and biogas from anaerobic digestion of fermentable materials (e.g., agricultural and livestock residues) has entered our lives. According to the International Energy Agency it is estimated that the needs in 2040 will be 48% higher than in 2012 so all political decisions have converged on an urgent need for the use of more and more renewable and green energy. Considering the overall economic activity of these sectors in the region of Thessaly, the aim of this study is to highlight the residues from agricultural and livestock activities in the primary sector and calculate the annual biomass production, the methane and biogas potential, the electrical and thermal energy that can be produced from these wastes, as well as the solid residue that can be used to improve the soil of the region. The study was based on data referring to the years 2015 to 2020. The production of livestock and agricultural residues, averaged over the above six-year period in the study area, was estimated at approximately 4.8 × 106 t·yr.−1, with livestock residues accounting for 83% and agricultural residues for 17%. Furthermore, the total residues can produce an average biogas potential of approximately 4.7 × 106 m3·yr.−1, while the amount of electricity that can be produced ranges from 708–1091 GWh·yr.−1, and the corresponding thermal energy from 1112–1577 GWh·yr.−1. As a result of the complete anaerobic digestion process, a solid residue could also be obtained for the improvement of the region’s soil, which translates into a quantity in the range of 4.01 × 104 to 5.10 × 104 t·yr.−1.

Green façades consist of the application of vegetation on buildings' vertical enve-lope. The integration of vegetation into the building fabric improves not only the aesthetic appearance, but also the energy performance of the building itself. The introduction of green façades mainly aims at a passive thermal control of build-ings' for enhancing sustainability of the built environment. An experimental green façade was tested at the University of Bari, in a Mediterranean climate context. The experimental green façade was south-exposed and realized with evergreen plants, following the characteristics of the indirect typology. A portion of the south wall was left bare to be used as a control for comparison. The contribution of the green façade in terms of passive climate control was particularly relevant during summer. Vegetation affects the boundary climatic conditions and the surface temperature. A reduction in sensible air and surface temperature of up to 2.2°C and 6.7°C, respectively, was recorded. The wall behind vegetation received 95.6% less solar radiative energy than the bare wall. These results were a direct conse-quence of the two main cooling mechanisms that characterize the green façade, the evapotranspiration and the shading effect. These effects affected the heat transfer reducing the energy input through the covered wall. The reduction of the incoming heat through the covered wall was read as energy saving, since it inevita-bly affects the building energy demand for cooling. It was found that the green fa-çade allowed a mean daily energy saving of 1.1 MJ m-2 and that 90.9% of this was obtained at daytime. These findings contribute to increasing the knowledge of en-ergy functioning and of the real advantages provided by green façades.

A sustainable and environmentally alternative to commonly used air conditioning systems can be the solar cooling system due to the use of renewable and clean energy. Solar absorption systems can be used for greenhouse cooling in areas with high outdoor temperatures and solar radiation levels. These systems take advantage of the simultaneity between the solar energy availability and the greenhouse cooling demand allowing the reduction of conventional electricity and water consumption. This paper presents the results of the application of a solar cooling plant for the climate control of a greenhouse at the University of Bari, Italy. The experimental plant consists of a Mediterranean greenhouse, having a surface of 300 m2, and of a single effect LiBr-H2O absorption chiller fed by evacuated-tube solar collectors. Two different localized systems were chosen for the distribution of cold inside the greenhouse: the first system presents pipes placed centrally on the cultivation vessels; the second consists of pipes in contact with aluminium plates and of a transparent EVA film, used to border an area close to plants. The distribution system of cold with pipes, plate and EVA film provided a slightly higher cooling capacity due to the presence of the plates which increases the ability to dissipate energy.

A novel prototype NB-IoT-based quasi-smart water management platform for irrigation is proposed. The prototype has been deployed in a vineyard in Peta village, Greece, as part of the AREThOU5A project. An IoT framework for regularly and accurately tracking the status of soil hydration and reporting it to a centralized entity for further processing since water needs are directly related to soil moisture is proposed. The framework is based on specialized IoT hardware that includes low-cost microcontrollers with integrated sensor interfaces and telecommunication modems, open-source applications, open and standardized data transfer protocols, with low capital and operating costs. In the vineyard, an IoT end-node have been placed. Each node: i) collects soil moisture and temperature samples at a depth of 20 cm, ii) is battery-powered and has a battery life of several months on a single charge, and iii) connects to the system back-end via NB-IoT. The sensor measurements from the IoT nodes are forwarded to a cloud-based infrastructure using the Constrained Application Protocol (CoAP)/IPv6 protocol using a public mobile network. Data is maintained on a cloud backend and can be accessed in real-time via dashboards from any Internet-connected individual. In terms of hardware integration, operating solutions, networking and connectivity support, the proposed platform offers numerous novel features.

The control of large greenhouse installations, especially those with hydroponics crops, is based on the analysis and use of data recorded by many sensors. At the same time, the size of such installations does not allow for their effective terrestrial surveillance, to detect problems promptly. In recent years, there has been an interest in the development of autonomous agbots equipped with agricultural sensors. Several ground-based AGV (automated guided vehicles) and UAV (unmanned aerial vehicles) systems have been developed for use in open-air plots. A key feature of all these innovative systems is spectroscopy, the development of which has been assisted by the surveillance capabilities and speed of modern-day UAVs (drones). However, there is a lag in the use of spectroscopy inside greenhouses since UAVs do not move freely indoors. In this paper, we propose as a solution a three-device (3DS) system.

Background: Photovoltaics (PV) provide an alternative solution to cover energy demands in greenhouses. This study evaluates the effect of PV panels installed on the roofs of greenhouses, and the partial shading that they cause, on the growth parameters and growth indicators of the experimental cultivation of peppers (Capsicum annuum cv. California Wonder). The growth of the plants, the antioxidant profile, radical scavenging activity, total phenolic content, and the phenolic and metabolic profiles (using LC-MS spectrometry and NMR spectroscopy) are evaluated.; Results: Data are presented from a full cultivation period. Results indicated that indoor temperatures were similar for both glass and glass-PV (glass with PV panels installed) greenhouses during the day and the night. The production yield was higher for the glass-PV greenhouses. The pepper fruits' weight, dimensions, and thickness were similar in both cases. Comparison of the pepper fruit extracts in terms of total phenolic content, antioxidant, and antiradical activities indicated differences that were not statistically significant. Photometric and spectroscopic studies both showed a smaller distribution of values in the case of the glass-PV greenhouse, probably indicating a more consistent phytochemical profile.; Conclusion: Covering only a small proportion (ca. 20%) of the greenhouse roof with photovoltaic panels contributes considerably to its energy demands without affecting plant growth and quality. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

Energy demand of greenhouses is an important factor for their economics and photovoltaics can be considered an alternative solution to cover their electrical and heating needs. On the other hand, plants cultivated under different solar radiation intensities usually appear different physiological adaptations. The objective of this research was to investigate the effect of photovoltaic panels’ induced partial shading on growth and physiological characteristics of lettuce (Lactuca sativa L.) and rocket (Eruca sativa Mill.) plants. Our results indicate that lettuce productivity and the corresponding photosynthetic rate were not affected under the photovoltaic cultivation in comparison with the reference one. On the other hand, the rocket cultivation was less productive and showed lower photosynthetic rate under photovoltaic panels than in the reference greenhouse. The different physiological response between lettuce and rocket seems to be associated with the effect of environmental factors such as solar radiation intensity, temperature and humidity apart from the possible inherent characteristics of each plant species.

Greenhouse covering materials have a substantial impact on the in-house thermal conditions. The development of alternative materials which can regulate the radiation and heat penetration in the greenhouse can significantly improve the cultivation conditions as well as minimize the energy requirements for heating, cooling and ventilation. In this study polymer prototype nanocomposites were developed through the use of uniform dispersions of highly porous granules, capable of regulating the Photosynthetically Active Radiation. The investigated material was tested against its environmental performance as well as for its nanomechanical behaviour. For this purpose, two identical small-scale experimental greenhouses were employed, in which the temperature, the relative humidity and the density of solar energy (penetrating and Photosynthetically Active Radiation) were measured. The mechanical properties, namely Young’s modulus and hardness of the tested material, were estimated by analysing the measured load–displacement curves delivered by nanoindentation testing. The findings of this study revealed that the proposed material has such a performance in radiation which allows its employment for temperature tolerant crops and cool growing.

Great advancements in technologies such as big data analytics, robots, remote sensing, the Internet of Things, decision support systems and artificial intelligence have transformed the agricultural sector. In the greenhouse sector, these technologies help farmers increase their profits and crop yields while minimizing the production costs, produce in a more environmentally friendly way and mitigate the risks caused by climate change. In greenhouse farming, especially in the Mediterranean region, a lack of knowledge and qualified personnel able to uptake new knowledge, the small size of farms, etc., make it difficult to implement new technologies. Although it is necessary to demonstrate the advantages of innovations related to sustainable agriculture, there is a little opportunity for specific training on greenhouse production in cutting-edge technologies. To gain insight into this problem, questionnaires for greenhouse farmers and intermediaries were developed in multiple choice format and filled in by the stakeholders. A statistical analysis was performed, and the results are presented in graphical form. In most cases, the findings confirmed that producers who run small farms, in most cases, have a lack of knowledge, especially on how to manage climate control systems or fertigation systems. The majority of farmers were elderly with a low level of education, which makes it difficult to be aware of the training issues, due to distrust and a lack of innovation culture. Therefore, their strategy was usually survival with cost control. However, young graduates have been recently returning to agriculture, and they are open to training activities and innovation. The most desirable training offer should be related to sustainable agriculture and precision agriculture technologies.

The installation of PV panels on the greenhouse’s roof reduces solar radiation that passes through roof glazing and falls to the plants inside the greenhouse, affecting their lighting and therefore crop growing. In this paper, performance results of energy production and plant growing from installed PV panels on greenhouse roof, are presented. The results are obtained from a cultivation period of lettuce crop inside two greenhouses, one with fixed roof installed photovoltaics and another unit without photovoltaics. Regarding electrical output, PV panels produced 50.83 kWhm −2 for the characteristic cultivation period of Feb-Mar-Apr, creating also a 20% greenhouse shading. Plant growing results under shading effect were satisfactory, as they were at same level with those of reference greenhouse without PV covered roof. Extending the results for three PV installation modes to 1 ha greenhouse, theoretical results were calculated. The considered PV installation modes are the fixed one, with panels placed on south facing greenhouse roof and two sun tracking modes, with PV panels in rows and axis on east-west and north-south direction. The calculations showed that sun tracking PV panels produce more electricity than fixed mode and can result to solar control of the interior space of the greenhouse.

The controlled environment includes the greenhouse and its environmental control systems that are implemented to obtain the desired climate in order to produce a quality crop within a predictable and repeatable time schedule. Energy consumption for heating and cooling is the primary cost component in greenhouse operation. Heat losses due to both, conduction/convection through and radiation from the covers of the greenhouse represent the main causes of the unacceptably high energy consumption in today's greenhouses. The poor insulating properties of the materials presently used result in heat losses which may reach 50% of the overall energy consumption during the greenhouse operation. Also, most places have a summer climate that requires greenhouse cooling. Today, industry and environment requirements are always asking for better performing materials. For all the above reasons, a new polymer nanocomposite sheet cover has been developed through the use of uniform dispersions of highly porous granulated nanoparticles. In this work, the energy requirements of a greenhouse covered by a nanocomposite film were evaluated and the results revealed that it offers improved thermal and optic qualities. This work was co-funded by the European Regional Development Fund and the Republic of Cyprus through the Research Promotion Foundation, Project with Protocol No. ΤΕΧΝΟΛΟΓΙΑ/ΥΛΙΚΑ

According to the European Environment Agency, the agricultural sector consumes around 3% of the total energy consumed in the European Union and specifically 28.8 million tones of oil equivalent in 2016. Although between 2005 and 2016, the final energy consumption in the EU decreased in the fishing, agriculture and forestry sectors by 24.7 % the energy required in this sector is considered to have a significant contribution to the energy related policies of the EU. Greenhouses constitute a major energy consumer of the agricultural sector in the European Union. Although strictly speaking, greenhouses differ from buildings in several ways, such as the construction, the building systems and the use, the principles used to analyse the energy consumption of greenhouses, as well as the strategies to control their energy performance are quite similar with those of the building sector. This study aims to present the recent advancements in the analysis of the energy performance of greenhouses, with a special focus on next generation greenhouses, also known as intelligent greenhouses. The main energy consumption sources in greenhouses, as well as their normalized intensity is presented. State-of-the-art automations to control the energy performance of greenhouses, as well as intelligent systems used to achieve the required thermal conditions in greenhouses, such as automation systems, infrared heating and advanced covering materials are presented. The main challenges of the intelligent greenhouse sector, as well as the requirements for the development of new energy related standards for greenhouses are also discussed. The study concludes with the presentation of the energy performance of a greenhouse, considered as intelligent, of the Department of Agricultural Technology of the Technological Education Institute of Western Greece in Patras, Greece. Detailed data logging of the temperature and indoor conditions of an intelligent greenhouse are analysed and compared with regard to contemporary greenhouses, revealing and quantifying the potentials of this sector in the energy saving strategies of Greece and the EU.

The implementation of Infrared (IR) radiation in heated greenhouses possesses the advantage of high directional control and focused compensation of energy losses, appropriate for creating local microclimate conditions in highly energy-consuming systems, such as greenhouses. Moreover, it can efficiently maintain favorable environmental conditions at the plant canopy. The present study studies the application of Infrared (IR) heating in an experimental greenhouse with eggplant (Solanum melongena L.) cultivation. The experimental results are presented from a full cultivation period inside two identical, small scale experimental greenhouses, with IR and forced air heating system, respectively. The effects of IR heating over plant growth parameters, including the yield of the fruits as well as the total phenolic content and the antioxidant profile of eggplants fruits&rsquo, extracts are measured and discussed. The results indicate a greater uniformity production in the IR heating greenhouse in terms of antioxidant and radical scavenging activities, as well as the total phenolic content. Moreover, the phenolic profile of eggplant fruits from both greenhouses revealed the existence of numerous bioactive compounds, some of which were only characteristic of the eggplant fruits from IR heated greenhouses.

The implementation of Infrared (IR) radiation in heated greenhouses possesses the advantage of high directional control and focused compensation of energy losses, appropriate for creating local microclimate conditions in highly energy-consuming systems, such as greenhouses. Moreover, it can efficiently maintain favorable environmental conditions at the plant canopy. The present study studies the application of Infrared (IR) heating in an experimental greenhouse with eggplant (Solanum melongena L.) cultivation. The experimental results are presented from a full cultivation period inside two identical, small scale experimental greenhouses, with IR and forced air heating system, respectively. The effects of IR heating over plant growth parameters, including the yield of the fruits as well as the total phenolic content and the antioxidant profile of eggplants fruits’ extracts are measured and discussed. The results indicate a greater uniformity production in the IR heating greenhouse in terms of antioxidant and radical scavenging activities, as well as the total phenolic content. Moreover, the phenolic profile of eggplant fruits from both greenhouses revealed the existence of numerous bioactive compounds, some of which were only characteristic of the eggplant fruits from IR heated greenhouses.

The advantages of Infra-Red (IR) heating is verified and demonstrated in a full-scale production greenhouse for vegetable seedlings, heated by gas-fired IR radiators. Temperature distributions data collected during a 62-day period during the winter showed that the seedlings could be kept at the optimum thermal conditions while the greenhouse air was maintained at a 2°C-3°C lower temperature, indicating a significant reduction in energy requirements. These results were also supported by Liquefied Petroleum Gas (LPG) consumption data collected over a period of two consecutive years, in relation to climatic conditions.

Photovoltaics (PV) provide an alternative solution to cover energy demands in greenhouses. This study evaluates the effect of PV panels installed on the roofs of greenhouses, and the partial shading that they cause, on the growth parameters and growth indicators of the experimental cultivation of peppers (Capsicum annuum cv. California Wonder). The growth of the plants, the antioxidant profile, radical scavenging activity, total phenolic content, and the phenolic and metabolic profiles (using LC-MS spectrometry and NMR spectroscopy) are evaluated.Data are presented from a full cultivation period. Results indicated that indoor temperatures were similar for both glass and glass-PV (glass with PV panels installed) greenhouses during the day and the night. The production yield was higher for the glass-PV greenhouses. The pepper fruits' weight, dimensions, and thickness were similar in both cases. Comparison of the pepper fruit extracts in terms of total phenolic content, antioxidant, and antiradical activities indicated differences that were not statistically significant. Photometric and spectroscopic studies both showed a smaller distribution of values in the case of the glass-PV greenhouse, probably indicating a more consistent phytochemical profile.Covering only a small proportion (ca. 20%) of the greenhouse roof with photovoltaic panels contributes considerably to its energy demands without affecting plant growth and quality. © 2018 Society of Chemical Industry.

The performance of an Infra-Red heating system using gas fired IR radiators is demonstrated in a full scale production greenhouse for vegetable seedlings. Outside meteorological data and the greenhouse thermal conditions have been monitored for a heating period of 60 days, to assess the quality of the canopy climate and the potential in energy savings. Results indicate that the seedlings are kept at optimum thermal conditions while the greenhouse air is maintained at lower temperature, by 2-3 °C, indicating a significant reduction in energy requirements. During operation, plant growth seemed to be positively affected by the IR radiation, whereas no plant infections by pests and / or diseases were observed.

In this study, the potential of near infrared heating (NIR) is assessed experimentally in comparison to forced air heating. To this end the night time heating needs for two identical, scaled down, experimental greenhouses located in central Greece were monitored for one thermal period. Four IR electric lamps were used to heat the first greenhouse whereas the second one was equipped with an electric forced air heater and an electric fan which was used for the homogenization of the temperature distribution. The output of several thermocouples located at the canopy area, on the cover and in the greenhouse air in both greenhouses were recorded every minute and 10 minutes averages were stored on a data logger, along with parameters characterizing the outdoors macroclimate, including outside and sky temperatures, wind speed and relative humidity measured by a suitable meteorological mast. The two heating systems were operated automatically to keep a reference temperature at the canopy within certain limits during nights (14-16 °C), suitable for the growth of lettuce, which was used as the test cultivation. Both heating systems maintained successfully the required conditions at the canopy for the growth of the plants. The energy consumption was recorded based on the time of operation of the heating systems. The internal air temperature in the IR heated greenhouse was always several degrees lower than the reference temperature of the plants resulting in significant energy consumption savings for the IR heated greenhouse. Savings of 38-50% were measured for the IR system in relation to the consumption of the conventionally heated greenhouse during the thermal period summing up to a total mean of 43%.

Infrared (IR) heating as alternative to forced air heating has been studied experimentally for 70 days in two identical, small-scale, experimental greenhouses. The two heating options were implemented with four IR electric lamps and an electric forced air heater correspondingly. The microclimate in the greenhouses was monitored with thermocouples. Parameters characterizing the outdoors macroclimate were also monitored. Lettuce was used as the test crop, and the two heating systems were operated automatically to maintain a suitable reference temperature at the canopy. The investigation focused on night heating needs. Results indicated that the internal air temperature in the IR-heated greenhouse was always kept several degrees lower than the value targeted for the canopy. This lower temperature resulted in 43% average energy savings for the IR-heated greenhouse, compared to the conventionally heated one. A simple numerical model was used to estimate the potential energy savings in a production-scale greenhouse.

The advantages of Infrared (IR) heating is verified and demonstrated in an experimental greenhouse with eggplant cultivation. IR radiation heating systems possess the advantage of high directional control and focused compensation of energy losses, appropriate for creating local temperature conditions in open or thermally unprotected spaces, resulting in an overall reduction of heat losses and consequently heating energy needs up to 50%. IR heating systems can efficiently maintain favourable environmental conditions at the plant canopy. The objective of this research is to investigate the effect of IR radiation on growth parameters and physiological characteristics of eggplant. Extensive experimental results are presented from a full cultivation period inside two identical, small scale experimental greenhouses, with IR and forced air heating system, correspondingly. Eggplant (Solanum melongena L.) is used as the test crop for a three months period. The produced data include solar radiation, relative humidity, greenhouse indoor air temperature and plant growing. Results are compared to conventional cultivation. In parallel with plant growing parameters’ evaluation, the antioxidant and metabolic profile of eggplant from the experimental greenhouse was evaluated in comparison to conventional cultivation.

The potential advantages of night-time heating of greenhouses by modern infrared (IR) radiative sources, instead of forced hot air, are examined experimentally and theoretically. Measurements of indoor and outdoor conditions during typical cold nights in central Greece were taken in an experimental greenhouse using either forced hot air or IR heating. A simple theoretical model that contains all the essential physics was developed and subsequently used in parametric studies. Experimental and simulation results confirmed that, with IR heating, inside air temperatures several degrees lower than the desired plant canopy temperature were sustained, and that this temperature difference increased proportionally to the nightly drop in outside temperature. The model estimated energy savings in the order of 45% to 50% using the IR sources currently available, and predicted significant further benefits from improvements in the radiative efficiency of the IR sources.