Energy performance and climate control in mechanically ventilated greenhouses: A dynamic modelling-based assessment and investigation

Controlled environment agriculture in greenhouse is a promising solution for meeting the increasing food demand of world population. The accurate control of the indoor environmental conditions proper of greenhouses enhances high crop productivity but, contemporarily, it entails considerable energy consumption due to the adoption of mechanical systems. This work presents a new modelling approach for estimating the energy consumption for climate control of mechanically ventilated greenhouses. The novelty of the proposed energy model lies in its integrated approach in simulating the greenhouse dynamics, considering the dynamic thermal and hygric behaviour of the building and the dynamic response of the cultivated crops to the variation of the solar radiation. The presented model simulates the operation of the systems and the energy performance, considering also the variable angular speed fans that are a new promising energy-efficient technology for this productive sector. The main outputs of the model are the hourly thermal and electrical energy use for climate control and the main indoor environmental conditions. The presented modelling approach was validated against a dataset acquired in a case study of a new fully mechanically controlled greenhouse during a long-term monitoring campaign. The present work contributes to increase the knowledge about the dynamics and the energy consumption of greenhouses, and it can be a valuable decision support tool for industry, farmers, and researchers to properly address an energy efficiency optimisation in mechanically ventilated greenhouses to reach the overall objective of decreasing the rising energy consumption of the agricultural sector

Nueva nave de Ensayos Mecánicos en el Instituto Eduardo Torroja

This important building meets an urgent need at the Institute Eduardo Torroja to have a mechanical testing hall that is capable of dealing with all kinds of tests that are likely to arise in the foreseeable future. In designing it account has been taken of all requirements anticipated as a result of the experience obtained during the use of the earlier testing hall which the Institute already has. The new testing hall consists essentially of a metallic structure, 33.50 m high, 11.50 m wide and 8 m high, enclosed by prefabricated LECA type panels. The hall has a powerful reinforced concrete slab, 11.50 m wide and 25.50 m long, which is 1.20 m thick. The slab has 270 anchorage points, with a load capacity of 50 t and 100 t each. These points can be loaded singly, or in groups. The slab rests on two lateral reinforced concrete walls, of 80 cm thickness. Below the slab there is a basement, which can be used in conjunction with the hall above for testing purposes, since the anchorage points make it possible to communicate both sides of the slab. A careful system of illumination has also been provided, and heavy vehicles can enter both the basement and the main hall. One ten ton bridge crane has been installed, although two such cranes can be fitted. All calculations have been done with the aid of the electronic computer of the I.E.T.c.c. The total design makes this project one of the most important of its type in Europe.A los quince años de estrenar la primera nave de Ensayos Mecánicos con que contó el Instituto, se inaugura esta segunda nave. A ella nos vamos a referir en el presente artículo, esencialmente descriptivo. No obstante, son tan singulares las razones que han motivado su necesidad que, aunque sea en forma sumamente breve, creemos de interés dar cuenta de ellas en este preámbulo

External gap progression after cyclic fatigue of adhesive overlays and crowns made with high translucency zirconia or lithium silicate

Objectives: To evaluate three-dimensional external gap progression after chewing simulation of high translucency zirconia (HTZ) and zirconia-reinforced lithium silicate (ZLS) applied on endodontically treated teeth with different preparation designs. Materials and Method: Endodontically treated molars were prepared with low-retentive (adhesive overlay) and high-retentive (full crown) designs above cementum-enamel junction and restored with HTZ and ZLS. Micro-computed tomography analysis was assessed before and after chewing simulation to evaluate three-dimensionally the external gap progression. Results were statistically analyzed with two-way ANOVA and post-hoc Tukey test. Results: High-retentive preparation design had a significantly inferior gap progression compared to the overlay preparation (p < 0.01); ZLS exhibited a significant inferior gap progression compared to HTZ (p < 0.01). Conclusions: High-retentive preparations restored with ZLS seem to better perform in maintaining the sealing of the external margin after cyclic fatigue. Clinical significance: The clinician should pay attention to the proper combination of preparation designs and ceramic material selection for an endodontically treated molar restoration. HTZ seems to perform worse than lithium silicate in terms of marginal sealing, still showing lacks in resistance to cyclic fatigue when adhesive preparations are performed