• Energy Research
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The possibility to increase human comfort and reduce the global footprint of buildings is a powerful driving force for introduction of new building technology. Here advanced coating technologies pl ...

Abstract A unique large scale pilot plant of the CellFlux thermal energy storage concept is experimentally investigated. This storage concept consists of a regenerator type thermal energy storage volume, which is coupled to a finned tube heat exchanger by a circulating intermediate working fluid. The system investigated in this work operates at a temperature of 390 °C and uses air as intermediate working fluid which is conveyed by a centrifugal fan. The storage volume has a bed length of over ten meters and is of a novel design, where the air flows in horizontal direction. Since this approach could cause a flow maldistribution, a thorough analysis is of major interest for the accuracy of subsequent numerical simulations. The experiments reveal that the mass flow along the centerline can be up to 20% higher than the mean bulk flow. A significant maldistribution between top and bottom area, however, is not observed. As an alternative to the typically used rock filling, the storage volume is equipped with standard hollow bricks. These bricks are cost effective but do not have a well-defined shape. Thus, the predictability of the pressure drop by correlations found in the literature is unclear. It turns out that the measured pressure drop is evenly distributed in axial flow direction but generally higher than expected from the assumption of pure channel flow. Further experiments are conducted to validate the heat capacity of the bricks and to derive a correlation for the inner heat transfer between bricks and storage walls. Eventually, the aim of the experimental investigation is a general proof of concept as basis for the numerical investigation. Thus, all specifications of the plant and the storage material are provided. The plant is analyzed towards plausibility of heat losses, showing that heat losses can be predicted well within the given uncertainties.

Environment preservation, energy, and the growing economy are becoming strongly interconnected themes requiring new solutions to be exploited. An example of this interconnection is the demand for the development of almost zero-energy buildings, i.e. buildings capable to be almost autonomous from external energy supply or at least not dependent on the energy supply from utilities. The actual conception of a zero energy building is a very complex system formed by several subsystems, with the consequence that costs are very high and reliability relatively low. The aim of this research program is to deepen the possibility to employ the Stirling engine and cooler technology to lower the number of components required in a near zero-energy building, increase the efficiency, and contemporary raise the reliability of the overall system. Stirling cooler could be used to convert mechanical work into heating and cooling effects and produce the temperature difference by the expanding and compressing the working fluid. A similar concept of the Stirling cooler could also be adopted to develop a heat pump. Compared to the traditional vaporcompression refrigeration systems, the Stirling coolers are of higher efficiency and with no components like compressor, expansion valve, evaporator, or condensers. Therefore, they are considered to be clean cooling devices. On the other hand, the Stirling engine is an external combustion engine, which is compatible with a variety of thermal sources, such as solar radiation, waste heat, geothermal energy, combustion, and so on. With the heat input to the hot end of the engine, the Stirling engine could be operated to produce mechanical work/electricity at high thermal efficiency. In principle, the Stirling machines are capable to provide all the forms of energy (heat, cool, and electricity) that form the almost total energy load of a building.

Abstract A numerical and experimental study was conducted, with the purpose of inferring the influence of the CO2 concentration ( x CO 2 ) for different equivalence ratios ( ϕ ) on CH4/CO2/air (biogas) flames chemiluminescence. A thorough analysis on the signals of OH∗, CH∗, C 2 ∗ and CO 2 ∗ was performed. Typical biogas compositions were tested under laminar atmospheric flame conditions, within the unburned equivalence ratio of 0.9 and 1.14 with CO2 concentrations up to 40% in the blend. Experimental measurements of chemiluminescence were done using spectroscopy in the UV–visible region of the spectra. Simulations were performed with the GRI-Mech 3.0 mechanism without accounting for the nitrogen chemistry, extended with a chemiluminescence kinetics of OH∗, CH∗, C 2 ∗ and CO 2 ∗ , in a burner-stabilized frame in CANTERA. Experimental measurements and numerical simulations are compared and generally are in good agreement. It was verified that CO2 dilution leads to a regular decrease in the emission intensities of OH∗, CH∗, C 2 ∗ and CO 2 ∗ . Relations between chemiluminescence intensity ratios and x CO 2 and ϕ were found. It was shown that OH∗/ CO 2 ∗ and C 2 ∗ / CO 2 ∗ have the potential predict x CO 2 in CH4/CO2/air flames. Moreover, it was verified that OH∗/CH∗, OH∗/ C 2 ∗ and CH∗/ C 2 ∗ are well suited to infer ϕ for the blends tested. It was verified that x CO 2 does not cause relevant changes in the chemiluminescence ratios when inferring ϕ .

This paper presents implementation of pressure transmitters, developed at Institute of Chemistry, Technology and Metallurgy (ICTM), within the feed water system existing in thermal power plant TENT-A located in Obrenovac, Serbia. For this purpose, high pressure transmitters (up to 400 bar), with standard current output (4–20) mA, digital display for in-situ reading and incorporated HART protocol for remote reading, are used. This type of monitoring enables higher degree of reliability, safety and energy efficiency of the feed water system. In order to optimize the energy efficiency aspect, special attention is focused on accuracy and precision of the measurements.

Abstract Environmental-impact reduction potential is great early in new product development. To exploit this potential, this study evaluates novel combinations of existent processing technologies. Process engineering is combined with an environmental product assessment along the supply chain. In the dairy sector, drying milk into milk powders is a highly energy-intensive process. This study investigates whether switching from milk powders to new products known as milk concentrates diminishes the overall environmental impact along the supply chains of dairy-containing products. A comparative life cycle assessment (LCA) is conducted, which considers individual processing steps that can be combined and operated in various ways to generate a multitude of different skim milk concentrates. For relevant environmental indicators such as cumulative energy demand, global warming potential, eutrophication potential, and acidification potential, concentrates were found to have a lower environmental impact than powders, even if the former are trucked up to 1000 km. This break-even distance is a conservative estimate. It depends upon the environmental impact of raw-milk production. The concentrate with the lowest environmental impact is produced by a combined concentration with reverse osmosis and evaporation to a dry-matter content of 35% and preservation via subsequent pasteurization. This holds for all indicators except eutrophication potential, for which this concentrate is the second-best option. This study identifies the frame within which milk concentrates are an advantageous substitution for milk powder and demonstrates the value of applying environmental assessment to product development and processing-technology selection.

Bacterial community structure and dynamics in anaerobic digesters are primarily influenced by feedstock composition. It is therefore important to unveil microbial traits that explain microbiome variations in response to substrate changes. Here, gene and genome-centric metagenomics were used to examine microbiome dynamics in four laboratory-scale reactors, in which sewage sludge was co-digested with increasing amounts of food waste. A co-occurrence network revealed microbiome shifts in response to changes in substrate composition and concentration. Food waste concentration correlated with extracellular enzymes and metagenome-assembled genomes (MAGs) involved in the degradation of complex carbohydrates commonly found in fruits and plant cell walls as well as with the abundance of hydrolytic MAGs. A key role was attributed to Proteiniphillum for being the only bacteria that encoded the complete pectin degradation pathway. These results suggest that changes of feedstock composition establish new microbial niches for bacteria with the capacity to degrade newly added substrates.

False codling moth Thaumatotibia leucotreta (Meyrick) is a pest native to sub-Saharan Africa infesting over 100 plant species including tomato. Its survival and performance are influenced by changes in precipitation and stress-related biochemical changes in the host plant. Water availability for agricultural production continues to decline due to climate change affecting drought-sensitive crops like tomatoes. Little is known on host plant-insect interactions of T. leucotreta and tomato as influenced by moisture stress. Hence, our study tested the impact of different water holding capacities (WHC) (40%, 50%, 60%, 70%, and 90%) of plant growing media on the growth of Anna F1 and Yaye tomato varieties and the infestation rate and development of T. leucotreta on the two varieties. WHC significantly influenced the growth of Anna F1 and Yaye tomato varieties. WHC significantly affected stem girth of Anna F1 variety and leaf length, leaf width, stem girth, and plant height of the Yaye variety. For Yaye variety, T. leucotreta laid a significantly high number of eggs when grown at 70% WHC and had the highest pupation when grown at 60% WHC. The development of T. leucotreta as observed on wing growth was highest at 40% and 50% WHC for both Anna F1 variety and Yaye variety. Our study shows that the infestation of tomato by T. leucotreta is likely to be high when grown in water-scarce media. The results are useful for predicting possible future T. leucotreta trends with increasing water scarcity due to climate change and in designing pest management programmes.

We report on the magnetic properties of NdFeB powders produced by gas atomization, which is a powder manufacturing technology scarcely used in the past to produce such alloys. Using this technique, we have produced several ternary NdFeB alloys with Nd contents between 26.9 wt.% and 28.5 wt.%. The as-atomized powders were split into different size fractions by sieving. Subsequently, we measured the magnetic properties as a function of temperature, between 10 and 400 K, and particle size. The magnetic behavior depends strongly on the microstructure of the material, which in turn is determined by the particle size. It is reported a slope anomaly in the curve of magnetization as a function of temperature at around 150 K due to a spin-reorientation transition. Since gas-atomized powders are isotropic, this magnetic transition produces an increment of the magnetization below this temperature.