Research Trends on Greenhouse Engineering Using a Science Mapping Approach

Horticultural protected cultivation has spread throughout the world as it has proven to be extremely effective. In recent years, the greenhouse engineering research field has become one of the main research topics within greenhouse farming. The main objectives of the current study were to identify the major research topics and their trends during the last four decades by analyzing the co-occurrence network of keywords associated with greenhouse engineering publications. A total of 3804 pertinent documents published, in 1981-2021, were analyzed and discussed. China, the United States, Spain, Italy and the Netherlands have been the most active countries with more than 36% of the relevant literature. The keyword cluster analysis suggested the presence of five principal research topics: energy management and storage; monitoring and control of greenhouse climate parameters; automation of greenhouse operations through the internet of things (IoT) and wireless sensor network (WSN) applications; greenhouse covering materials and microclimate optimization in relation to plant growth; structural and functional design for improving greenhouse stability, ventilation and microclimate. Recent research trends are focused on real-time monitoring and automatic control systems based on the IoT and WSN technologies, multi-objective optimization approaches for greenhouse climate control, efficient artificial lighting and sustainable greenhouse crop cultivation using renewable energy

Isoprene emission rates under elevated CO(2) and O(3) in two field-grown aspen clones differing in their sensitivity to O(3)

• Isoprene is the most important nonmethane hydrocarbon emitted by plants. The role of isoprene in the plant is not entirely understood but there is evidence that it might have a protective role against different oxidative stresses originating from heat shock and/or exposure to ozone (O3). Thus, plants under stress conditions might benefit by constitutively high or by higher stress-induced isoprene emission rates. • In this study, measurements are presented of isoprene emission from aspen (Populus tremuloides) trees grown in the field for several years under elevated CO2 and O3. Two aspen clones were investigated: the O3-tolerant 271 and the O3-sensitive 42E. • Isoprene emission decreased significantly both under elevated CO2 and under elevated O 3 in the O3-sensitive clone, but only slightly in the O3-tolerant clone. • This study demonstrates that long-term-adapted plants are not able to respond to O3 stress by increasing their isoprene emission rates. However, O3-tolerant clones have the capacity to maintain higher amounts of isoprene emission. It is suggested that tolerance to O3 is explained by a combination of different factors; while the reduction of O3 uptake is likely to be the most important, the capacity to maintain higher amounts of isoprene is an important factor in strengthening this character. © The Authors (2008)

Energy performance and thermo-economic assessment of a microturbine-based dual-fuel gas-biomass trigeneration system

The focus of this paper is on the energy performance and thermo-economic assessment of a small scale (100 kWe) combined cooling, heat and power (CCHP) plant serving a tertiary/residential energy demand fired by natural gas and solid biomass. The plant is based on a modified regenerative micro gas-turbine (MGT), where compressed air exiting the recuperator is externally heated by the hot gases produced in a biomass furnace. The flue gases after the recuperator flow through a heat recovery system (HRS), producing domestic hot water (DHW) at 90 °C, space heating (SH), and also chilled water (CW) by means of an absorption chiller (AC). Different biomass/natural gas ratios and an aggregate of residential end-users in cold, average and mild climate conditions are compared in the thermo-economic assessment, in order to assess the trade-offs between: (i) the lower energy conversion efficiency and higher investment cost when increasing the biomass input rate; (ii) the higher primary energy savings and revenues from feed-in tariffs available for biomass electricity exported into the grid; and (iii) the improved energy performance, sales revenue and higher investment and operational costs of trigeneration. The results allow for a comparison of the energy performance and investment profitability of the selected system configuration, as a function of the heating/cooling demand intensity, and report a global energy efficiency in the range of 25-45%, and IRR in the range of 15-20% assuming the Italian subsidy framework

Thermo-economic assessment of an externally fired hybrid CSP/biomass gas turbine and organic Rankine combined cycle

This paper focuses on the thermo-economic analysis of a hybrid solar-biomass CHP combined cycle composed by a 1.3-MW externally fired gas-turbine (EFGT) and a bottoming organic Rankine cycle (ORC) plant. The primary thermal energy input is provided by a hybrid concentrating solar power (CSP) collector-array coupled to a biomass boiler. The CSP collector-array is based on parabolic-trough concentrators (PTCs) with molten salts as the heat transfer fluid (HTF) upstream of a fluidized-bed furnace for direct biomass combustion. Thermal-energy storage (TES) with two molten-salt tanks (one cold and one hot) is considered, as a means to reducing the variations in the plant's operating conditions and increasing the plant's capacity factor. On the basis of the results of the thermodynamic simulations, upfront and operational costs assessments, and considering an Italian energy policy scenario, the global energy conversion efficiency and investment profitability are estimated for 2 different sizes of CSP arrays and biomass furnaces. The results indicate the low economic profitability of CSP in comparison to only biomass CHP, because of the high investment costs, which are not compensated by higher electricity sales revenues

Testing of models of stomatal ozone fluxes with field measurements in a mixed Mediterranean forest

Mediterranean forests close to urban areas are exposed to polluted plumes loaded with tropospheric ozone. This is the case of Castelporziano Estate, a 6000 ha Mediterranean forest 25 km from Rome downtown on the coast of the Mediterranean Sea. In September 2011 we started an intensive field campaign aimed at investigating ozone deposition from a mixed Mediterranean forest, mainly composed by Quercus suber, Quercus ilex, Pinus pinea. Measurements at canopy level with the eddy covariance technique were supported by a vegetation survey and the measurement of all environmental parameters which allowed to calculate stomatal ozone fluxes. Leaf-level measurements were used to parameterize models to calculate stomatal conductance based on a Jarvis-type and Ball-Berry approach. We show changes in magnitude of ozone fluxes from a warm (September) to a cold period (October December). Stomatal component explained almost the totality of ozone fluxes during the cold days, but contributed only up to 50% to total ozone deposition during warm days, suggesting that other sinks (e.g. chemistry in the gas-phase) play a major role. Modeled stomatal ozone fluxes based on a Jarvis-type approach (DO3SE) correlated with measured fluxes better than using a Ball-Berry approach. A third model based on a modified Ball-Berry equation was proposed to account for the non-linear dependency of stomatal conductance on relative humidity. This research will help the development of metrics for ozone-risk assessment and advance our understanding of mixed Mediterranean forests in biosphere atmosphere exchange. (C) 2012 Elsevier Ltd. All rights reserved