Greenhouse Food Production Research Articles

A multi-level approach to the energy-water-food nexus: From molecule to governance

The energy-water-food (EWF) nexus is an approach to resource management that highlights the inextricable relationship that exists among three essential resources. The EWF nexus is aimed at fostering interlinkages, limiting trade-offs and exploiting synergies that exist amongst these resources. Adopting the nexus approach is key to sustainable development, as it can alleviate resource insecurities and harness collaboration between sectors. Several EWF nexus-related studies have exhaustively analysed the different levels of decision-making within the nexus. However, these studies have failed to account for the multi-level relationship that exists among the different levels of the nexus, as most have adopted a level-based approach. This review study presents a novel multi-level approach to addressing the EWF nexus-related challenges. The study analyses the multiple levels that exist within the EWF nexus. The three levels identified are the molecule, process, and governance levels. The study goes on to show how communication amongst all three levels not only impacts the performance of the system but is crucial for decision-making as the three stages are intrinsically related such that the decisions at one level directly influences the others. The study starts by reviewing the various molecular-level changes that can be made in each of the EWF resources to enhance their performance. Then a review of the set of modelling and analytical tools that have been applied to the process and governance levels are presented. Finally, a novel decision-making pyramid integrating all three levels is presented and discussed using the case of a greenhouse food production system.

Optimal spectra management for self-power producing greenhouses for hot arid climates

The air conditioning in hot and arid climates remains one of the grand challenges for food production in greenhouses. Therefore, significant efforts are given to determine the suitable techniques for effective cooling of greenhouses. Usually, greenhouses are used in colder climates to gather sunlight for heating purposes. However, hot climates with elevated solar irradiation characteristics suffer from high temperatures within the greenhouse. In this study, we propose a unique method solving the extensive cooling requirement of greenhouses in hot arid climates by employing an optimal spectra management strategy. The novel sun-tracking roof design of the greenhouse incorporates hot dielectric mirrors and solar panels, which help to reduce the cooling load and provide electricity to the vapor compression cooling unit. The spectrum above 750 nm is reflected to vertically aligned InGaAs solar cells for additional power generation, whereas the c-Si solar cells are able to provide effective shadowing at noontime without significant comprimise on photosynthetically active radiation (PAR) while producing power. The results showed an average reduction of 28.9% and 25.4% in the cooling load of the proposed greenhouse compared to the conventional greenhouse during the summer and winter seasons for sun tracking hours (10:00 a.m. to 1:00 p.m.), respectively, at a set greenhouse temperature of 28 °C. The proposed greenhouse produced an average of 22.18 kWh/day of electrical energy throughout the year. The novel roof significantly lowers the cooling load and partially meets the energy demand of greenhouses without compromising on photosynthetically active radiations to enter the greenhouse.

Comprehensive review on dehumidification strategies for agricultural greenhouse applications

Humidity is one of the important climate parameters in greenhouse food production. Maintaining humidity levels within the optimal growth range enhances yield. Moreover, excessively high relative humidity leads to diseases and deterioration of the crops. This paper presents a state-of-the-art review of the various dehumidification technologies available in the agricultural industry. Several novel conceptual designs from the literature are also discussed. The principal humidity control approaches utilized in greenhouses are ventilation (natural and forced), maintaining a high temperature, condensation on a cold surface, and adsorption by hygroscopic materials. The most common method for dehumidification is ventilation due to its minimal infrastructure. Although this method is considered the simplest, it causes additional sensible heating loads, particularly in colder climates. The added heating load can be reduced, ideally eliminated, by employing heat recovery systems. Furthermore, dehumidification by controlled condensation on a cold surface enables the capture and re-use of the latent energy released in condensation. By adsorption of water vapor using hygroscopic material, the latent heat of condensation is converted to sensible heat, which can be used for space heating in the greenhouse. Such a system can reduce the greenhouse humidity while maintaining a more uniform temperature profile over the crop canopy and reducing energy consumption. Finally, it is essential to emphasize that an appropriate dehumidification method should prevent condensation on plant surfaces, and also its operational cost should be as low as reasonably achievable to remain beneficial for growers.

Optimal processing of greenhouse crop residues to use as energy and CO2 sources

This work presents the development of suitable strategies focusing on greenhouse crop residues as energy and CO2 sources for improved food production in greenhouses. The utilization of greenhouse crop residues in combustion processes for heating and carbonic enrichment in greenhouses has previously been developed and evaluated. Nevertheless, greenhouse crop residues present several problems that make it difficult to use them for these purposes. Among the characteristics that can impede their use are excessive moisture and ash contents as well as their low density. In this work, the relevant solid fuel properties for this type of biomass have been studied.In addition, three pre-treatment strategies are proposed and evaluated, which aim to enhance the fuel quality of this biomass. These strategies were: 1) first relates to the drying strategy employed for reducing greenhouse crop residue moisture. 2) the second one relates to a reduction in ash content by avoiding contact with greenhouse soil and 3) mixing with other biomass kinds with better quality as solid fuels.The assays performed showed that these strategies were successful, resulting in biomass with a high heating value, up to 26.9 MJ/kg, and a lower ash content than untreated residues, with values as low as 13.0% dry weight. This value is closer to that for the standard biomass most commonly employed in direct combustion applications. The biomass produced has been verified as suitable for conventional boilers with thermal efficiencies up to 70%. The methods developed allow to reuse greenhouse crop residues as greenhouse fuel, providing both heat and CO2; thus enhancing production and sustainability.

Sustainable Food Production in Greenhouses and its Relations to the Environment

A greenhouse is essentially an enclosed structure, which traps the short wavelength solar radiation and stores the long wavelength thermal radiation to create a favourable microclimate for higher productivity. The sun’s radiation incident on the greenhouse has two parts: direct radiation and an associated diffuse sky radiation. The diffuse part is not focused by the lenses and goes right through Frensel lenses onto the surface of the absorbers. This energy is absorbed and transformed into heat, which is then transported via the liquid medium in copper pipes to the water (heat) storage tanks or, if used, open fish tanks. In this way, an optimal temperature for both plant cultivation and fish production can be maintained. Stable plant growth conditions are light, temperature and air humidity. Light for the photosynthesis of plants comes from the diffuse radiation, which is without substantial fluctuations and variation throughout most of the day. The air temperature inside the greenhouse is one of the factors that have an influence on the precocity of production. The selective collector acts in a more perceptible way on extreme air temperatures inside the greenhouse. Hence, the system makes it possible to avoid the excessive deviation of the temperature inside the greenhouse and provides a favourable microclimate for the precocity of the culture. Sediment and some associated water from the sediment traps are used as organic fertiliser for the plant cultivation. The present trend in greenhouse cultivation is to extend the crop production season in order to maximise use of the equipment and increase annual productivity and profitability. However, in many Mediterranean greenhouses, such practices are limited because the improper cooling methods (mainly natural or forced ventilation) used do not provide the desired micro-climatic condition during the summer of a composite climate. Also, some of these greenhouses have been built where the meteorological conditions require some heating during the winter, particularly at night. The worst scenario is during the winter months when relatively large difference in temperature between day and night occurs. However, overheating of the greenhouse during the day is common, even in winter, requiring ventilation of the structure. Hence, several techniques have been proposed for the storage of the solar energy received by the greenhouse during the day and its use to heat the structure at night. Reviews of such techniques are presented in this paper. Air or water can be used for heat transport. The circulating water is heated during the day via two processes. The water absorbs part of the infrared radiation of the solar spectrum. Since the water is transparent in the visible region, they do not compete with the plants that need it. Alternatively, the water exchanges heat with the greenhouse air through the walls. At night, if the greenhouse temperature goes down below a specified value, the water begins to circulate acting as heat transfer surfaces heating the air in the greenhouse. This communication describes various designs of low energy greenhouses. It also, outlines the effect of dense urban building nature on energy consumption, and its contribution to climate change. The objectives are to produce vegetables in greenhouse environment. Measures, which would help to save energy in greenhouses, are also presented. It also enabled the minimisation of temperature variation and, hence avoided the hazard of any sudden climatic change inside the greenhouse.

Sustainable Food Production in Greenhouses and Its Relations to the Environment

A greenhouse is essentially an enclosed structure, which traps the short wavelength solar radiation and stores the long wavelength thermal radiation to create a favourable microclimate for higher productivity. The sun's radiation incident on the greenhouse has two parts: direct radiation and an associated diffuse sky radiation. The diffuse part is not focused by the lenses and goes right through Frensel lenses onto the surface of the absorbers. This energy is absorbed and transformed into heat, which is then transported via the liquid medium in copper pipes to the water (heat) storage tanks or, if used, open fish tanks. In this way, an optimal temperature for both plant cultivation and fish production can be maintained. Stable plant growth conditions are light, temperature and air humidity. Light for the photosynthesis of plants comes from the diffuse radiation, which is without substantial fluctuations and variation throughout most of the day. The air temperature inside the greenhouse is one of the factors that have an influence on the precocity of production. The selective collector acts in a more perceptible way on extreme air temperatures inside the greenhouse. Hence, the system makes it possible to avoid the excessive deviation of the temperature inside the greenhouse and provides a favourable microclimate for the precocity of the culture. Sediment and some associated water from the sediment traps are used as organic fertiliser for the plant cultivation. The present trend in greenhouse cultivation is to extend the crop production season in order to maximise use of the equipment and increase annual productivity and profitability. However, in many Mediterranean greenhouses, such practices are limited because the improper cooling methods (mainly natural or forced ventilation) used do not provide the desired micro-climatic condition during the summer of a composite climate. Also, some of these greenhouses have been built where the meteorological conditions require some heating during the winter, particularly at night. The worst scenario is during the winter months when relatively large difference in temperature between day and night occurs. However, overheating of the greenhouse during the day is common, even in winter, requiring ventilation of the structure. Hence, several techniques have been proposed for the storage of the solar energy received by the greenhouse during the day and its use to heat the structure at night. Reviews of such techniques are presented in this paper. Air or water can be used for heat transport. The circulating water is heated during the day via two processes. The water absorbs part of the infrared radiation of the solar spectrum. Since the water is transparent in the visible region, they do not compete with the plants that need it. Alternatively, the water exchanges heat with the greenhouse air through the walls. At night, if the greenhouse temperature goes down below a specified value, the water begins to circulate acting as heat transfer surfaces heating the air in the greenhouse. This communication describes various designs of low energy greenhouses. It also, outlines the effect of dense urban building nature on energy consumption, and its contribution to climate change. The objectives are to produce vegetables in greenhouse environment. Measures, which would help to save energy in greenhouses, are also presented. It also enabled the minimisation of temperature variation and, hence avoided the hazard of any sudden climatic change inside the greenhouse.

Solar liquid desiccant regeneration and nanofluids in evaporative cooling for greenhouse food production in Saudi Arabia

This article is about using solar energy and liquid desiccant to provide evaporative cooling systems of spaces occupied by plants in high ambient humidity climate. The system took full benefit of the regeneration of liquid desiccant by pure solar energy. The effect of airflow on the predicted and measured average daily maximums of greenhouse temperatures obtained using desiccant system and those obtained with conventional evaporative cooling for the month of June was investigated and reported. The desiccant evaporative cooling system lowered the average daily maximum temperatures in the greenhouse by about 6°C relative to conventional evaporative cooling system. Furthermore, shell and tube heat exchanger configuration was adopted to simulate pipes implanted in the desiccant pad and fed with nanofluids supplied from a cooling tower. The effects of changing volume fractions of nanoparticles on energy effectiveness and heat transfer coefficient of an assumed shell and tube heat exchanger have been analyzed and discussed. Improvements on convective heat transfer coefficient of 7.20–14.40%, 6.20–12.30%, and 5.50–9.01% were obtained for 0.01–0.04 volume concentrations of Al2O3-W, Fe3O4-W, and ZnO-W nanofluids, respectively. In addition, energy effectiveness has been analyzed and enhancements of 27.50–50.10%, 25.01–40.10%, and 24.00–32.02% were obtained for volume fractions from 0.01 to 0.04 of ZnO, Fe3O4, and Al2O3 nanoparticles, respectively, suspended in water with constant mass flow rates of fluids. Dynamic indicators (life cycle and annualized life cycle costs) were applied to evaluate the economic-effectiveness of this energy supply system. The total life cycle cost was found to be $11,206 and the annualized life cycle cost for this system was found to be 1317$/year.

Modelling and experimental verification of a solar-powered liquid desiccant cooling system for greenhouse food production in hot climates

Experiments and theoretical modelling have been carried out to predict the performance of a solar-powered liquid desiccant cooling system for greenhouses. We have tested two components of the system in the laboratory using MgCl2 desiccant: (i) a regenerator which was tested under a solar simulator and (ii) a desiccator which was installed in a test duct. Theoretical models have been developed for both regenerator and desiccator and gave good agreement with the experiments. The verified computer model is used to predict the performance of the whole system during the hot summer months in Mumbai, Chittagong, Muscat, Messina and Havana. Taking examples of temperate, sub-tropical, tropical and heat-tolerant tropical crops (lettuce, soya bean, tomato and cucumber respectively) we estimate the extensions in growing seasons enabled by the system. Compared to conventional evaporative cooling, the desiccant system lowers average daily maximum temperatures in the hot season by 5.5–7.5 °C, sufficient to maintain viable growing conditions for lettuce throughout the year. In the case of tomato, cucumber and soya bean the system enables optimal cultivation through most summer months. It is concluded that the concept is technically viable and deserves testing by means of a pilot installation at an appropriate location.

A solar cooling system for greenhouse food production in hot climates

This study is motivated by the difficulty of cultivating crops in very hot countries and by the tendency for some such countries to become dependent on imported food. Liquid desiccation with solar regeneration is considered as a means of lowering the temperature in evaporatively-cooled greenhouses. Previous studies demonstrated the technical feasibility of the desiccation–evaporation process, but mainly in the context of human dwellings. In the proposed cycle, the air is dried prior to entering the evaporative cooler. This lowers the wet-bulb temperature of the air. The cooling is assisted by using the regenerator to partially shade the greenhouse. The heat of desiccation is transferred and rejected at the outlet of the greenhouse. The cycle is analysed and results given for the climate of the The Gulf, based on weather data from Abu Dhabi. Taking examples of a temperate crop (lettuce), a tropical crop (tomato) and a tropical crop resistant to high temperatures (cucumber) we estimate the extension in growing seasons relative to (i) a greenhouse with simple fan ventilation (ii) a greenhouse with conventional evaporative cooling. Compared to option (ii), the proposed system lowers summers maximum temperatures by 5 °C. This will extend the optimum season for lettuce cultivation from 3 to 6 months of the year and, for tomato and cucumber, from 7 months to the whole year.

“The Greenhouse of the Future”: Using a Sponsored Competition in a Capstone Course

Horticulture students often lack practical experience integrating information from diverse sources to solve complex real-life problems. Capstone courses seek to remedy this by giving students an opportunity to demonstrate a range of workplace skills such as teamwork, effective communication, and critical thinking. Sponsored competitions provide educators with an active-learning framework into which the goals of a capstone course can be developed. In 1996 the U.S. Dept. of Energy and the Epcot Center announced the “Greenhouse of the Future” competition. The competition sprang from an interest by sponsoring agencies to promote the development of new environmentally sound technologies for greenhouse food production and was open to all U.S. undergraduate students. The competition encouraged the formation of interdisciplinary student teams under the direction of a faculty advisor and offered the winning entry a $10,000 research grant and the opportunity to display the new technology at the Epcot Center in Florida. The M.S.U. entry focused on the development of season-extending energy retention systems designed for small greenhouses, production testing of cool-season, stress-tolerant crops such as Mesclun salad greens, and the use of an environmentally neutral growing system. Sponsored competitions present an important tool for achieving certain educational objectives and may be one way to help students think on a higher level. Encouragement and development of similar competitions within the green industry is needed. Competition guidelines, components of the M.S.U. winning entry, and integration of the competition into the capstone course “Greenhouse Management” will be discussed.

A global review of greenhouse food production

A global review of greenhouse food production

Book Review: Controlled Environment Agriculture: A Global Review of Greenhouse Food Production. Foreign Agricultural Economic Report No. 89.

Book Review: Controlled Environment Agriculture: A Global Review of Greenhouse Food Production. Foreign Agricultural Economic Report No. 89.

Reviews

Book reviewed in this article: Land Reform and Economic Development. By PETER DORNER. Penguin Books. Controlled Environment Agriculture: A Global Review of Greenhouse Food Production. By DANA G. DALRYMPLE. U.S.D.A. Agricultural Expansion in the United Kingdom with Declining Manual Labour Resources. By A. P. POWER and S. A. HARRIS. Government Economic Service Principles of Farm Business Analysis and Management. By ROBERT O'CONNOR. Irish University Press Linear Programming Applications to Agriculture. By R. R. BENEKE and R. WINTERBOER. Iowa State University Press Financial Management in Agriculture. By JOHN A. HOPKINS, PETER J. BARRY and C. B. BAKER. Interstate Printers and Publishers, Danville, Illinois. Cost Factors of Agriculture. By K. N. SINGH et al. National Institute of Bank Management (India), Bombay. Agricultural Product Prices. By W. G. TOMEK and K. L. ROBINSON. Cornell University Press. Agricultural Marketing and Prices. By KEITH O. CAMPBELL. Cheshire, Melbourne. Natural Rubber and the Synthetics. By P. W. ALLEN. Crosby Lockwood, London. Technical Assistance Administration in East Africa. Edited by YASHPAL TANDON. The Dag Hammarskjold Foundation, Stockholm. Joe Duncan ‐ The Scottish Farm Servants and British Agriculture. By J. H. SMITH. Department of Politics, University of Edinburgh.