Thermal energy use in three Swedish greenhouses – the outdoor temperature-dependent variation and the influence of wind speed under no-sunlight conditions

Thermal energy is used in greenhouses for the temperature and humidity control.  In the North of Europe, energy expenditures have a significant share in the total greenhouse production cost.  A study was performed to quantify and analyze the use of thermal energy in three Swedish commercial greenhouses (two with tomatoes and one with ornamental plants), to test the hypothesis that substantial amounts of heat are used at higher outdoor temperatures, and to investigate the influence of the wind speed on the energy use under no-sunlight conditions.  Hourly climate data were registered by means of Priva control systems.  The use of thermal energy was computed based on the readings from the flowmeters and the temperature of the inlet/outlet water to/from the boilers.  In the study, seven different ranges of outdoor temperatures for studying energy use at various outdoor temperatures were considered.  The use of thermal energy in Greenhouse A amounted to 793 MJ/m2 (April-October).  The yearly use of thermal energy in Greenhouse B with tomatoes was 1529 MJ/m2 and in Greenhouse C with ornamental plants 873 MJ/m2.  The results showed a positive relation between the wind speed and the use of thermal energy.  Under no-sunlight conditions, correlation coefficients between the wind speed and the use of thermal energy obtained for the various outdoor temperature ranges being considered were in the range of 0.017 to 0.470.  Calculations suggested that a reduction of the wind speed, e.g. by a fence or trees, by 50% may result in a 4% to 10% decrease of thermal energy use.  In one of the greenhouses (A) the magnitude of thermal energy use at higher outdoor temperatures (15°C to 20°C) was similar to the use in the same greenhouse at outdoor temperatures of 10°C to 15°C.  It was noted that the use of thermal energy is dependent on more factors than the wind speed and the outdoor temperature and that the importance of energy efficient dehumidification should be studied in future work.   Keywords: Thermal energy use; greenhouses; tomatoes; ornamental plants; wind spee

Thermal energy use for dehumidification of a tomato greenhouse by natural ventilation and a system with an air-to-air heat exchanger

The aim of the study was to estimate the amount of thermal energy used for dehumidification of a naturally ventilated tomato greenhouse and to estimate how mechanical ventilation with the use of a heat exchanger recovering heat from the exhaust to the supply air may decrease the energy use. Measured use of thermal energy in a naturally ventilated tomato greenhouse was compared to modelled values using Powersim® software. By the help of the model an estimation of the amount of energy used for dehumidification was made for the months April – September. A non-hygroscopic rotary air-to-air heat exchanger was studied, and its temperature and moisture efficiencies were measured. Modelling for leaf area index (LAI) 3.5 and 4.0 m2 m-2 indicated that 23 and 29% of the total thermal energy was used for moisture removal respectively. Modelling for the heat exchanger indicated thermal energy savings of 15 and 17% for the same LAI respectively

Thermal energy use in greenhouses

In the North European greenhouses, energy use for climatization accounts for a significant share of the operational costs. Air temperature and humidity are important factors whose control is crucial for assuring high productivity and limited use of energy. The objective of this thesis was to examine the use of thermal energy in greenhouses and to investigate the impact of a number of climate parameters on that use. A specific goal was to compare the measured use of energy for heating with the values simulated employing a model developed in Powersim software and, by means of the model, to determine the amount of energy necessary for dehumidification of a tomato greenhouse. Another specific goal was to employ the experimentally obtained performance values for a rotary heat exchanger to estimate the potential energy savings when heat exchanger is used for dehumidification of a greenhouse. Indoor and outdoor climate data were collected in three greenhouses located in southern Sweden, two with tomatoes and one with ornamental plants. The use of thermal energy in a tomato greenhouse was first measured and then modelled in Powersim for different levels of transpiration, i.e. for a leaf index area (LAI) of 3.5 and 4.0 m²/m². The impact of wind under no-sunlight conditions and at different outdoor temperatures was investigated. The performance of the heat exchanger operating at high humidity levels was tested in a series of measurements. The study showed that the use of thermal energy in greenhouses with tomatoes was significantly higher than in the greenhouse with ornamental plants. Further, the amount of energy used increased together with the wind speed. The reduction of the wind speed by 50% could result in energy savings of 4-10%. The use of thermal energy as obtained in the Powersim simulations was fairly similar to the measured values, especially when the modelling was for higher transpiration levels. However, it was concluded that further work on the model is needed. The simulations indicated that 23-29% of thermal energy in a greenhouse was used for dehumidification purposes. It was experimentally shown that thermal and moisture efficiencies of the heat exchanger employed in the study were about 70% and 45%, respectively. Further, it was found by modelling that the usage of such a heat exchanger in the investigated greenhouse resulted in the energy savings of 15-17%

Thermal energy use for dehumidification of a tomato greenhouse by natural ventilation and a system with an air-to-air heat exchanger

The aim of the study was to estimate the amount of thermal energy used for dehumidification of a naturally ventilated tomato greenhouse and to estimate how mechanical ventilation with the use of a heat exchanger recovering heat from the exhaust to the supply air may decrease the energy use. Measured use of thermal energy in a naturally ventilated tomato greenhouse was compared to modelled values using Powersim® software. By the help of the model an estimation of the amount of energy used for dehumidification was made for the months April – September. A non-hygroscopic rotary air-to-air heat exchanger was studied, and its temperature and moisture efficiencies were measured. Modelling for leaf area index (LAI) 3.5 and 4.0 m2 m-2 indicated that 23 and 29% of the total thermal energy was used for moisture removal respectively. Modelling for the heat exchanger indicated thermal energy savings of 15 and 17% for the same LAI respectively

Deir el-Naqlun 2014–2015. Preliminary report

The complex of the Nekloni monastery in Fayum (Deir el-Naqlun) was explored in yet another three seasons of fieldwork by a team from the Polish Centre of Mediterranean Archaeology. On the plateau, investigations were carried out in the southern part of Building D (Rooms D.50 and D.41–D.44), northern part of Building E, western part of the 12th–13th-century Cemetery A and Building I. A 6th-century Hermitage EE.06 in the Naqlun hills to the east of the plateau was cleared, yielding a collection of study material, especially pottery from the kitchen unit dated to the second half of the 5th–6th century. The assemblage from the kitchen unit was composed of cooking pots and saucepans; tableware was represented by goblets, plates and bottles (qullae), while storage/ transport vessels mainly by amphorae. Products of Egyptian workshops were mixed with imported wares of North African and Eastern Mediterranean origin (including Cyprus, Cilicia and Gaza)

Raman Imaging Providing Insights into Chemical Composition of Lipid Droplets of Different Size and Origin: In Hepatocytes and Endothelium

In this work, 3D linear Raman spectroscopy was used to study lipid droplets (LDs) <i>ex vivo</i> in liver tissue and also <i>in vitro</i> in a single endothelial cell. Spectroscopic measurements combined with fluorescence microscopy and/or histochemical staining gave complex chemical information about LD composition and enabled detailed investigations of the changes occurring in various pathological states. Lipid analysis in fatty liver tissue was performed using a dietary mouse model of liver steatosis, induced by a high fat diet (HFD). HFD is characterized by a high percentage of calories from saturated fat (60%) and reflects closely the detrimental effects of dietary habits responsible for increased morbidity due to obesity and its complications in well-developed Western societies. Such diets lead to obesity, hyperlipidemia, insulin resistance, and steatosis that may also be linked to endothelial dysfunction. In the present work, Raman spectroscopy was applied to characterized chemical composition of lipid droplets in hepatocytes from mice fed HFD and in the endothelium treated with exogenous unsaturated free fatty acid (arachidonic acid). The results demonstrate the usefulness of Raman spectroscopy to characterize intracellular lipid distribution in 2D and 3D images and can be used to determine the degree of saturation. Raman spectroscopy shows the potential to be a valuable tool for studying the role of LDs in physiology and pathology. The method is generally applicable for the determination of LDs of different size, origin, and composition. Moreover, for the first time, the process of LD formation in the endothelium was detected and visualized in 3D