• Energy Research

Thermal fading (TF) is an important characteristic in choosing appropriate thermoluminescence (TL) materials for particular applications. TF is the process of reducing the capability of producing the response due to radiation exposure. The fading rate of LiF based thermoluminescent (TL) material depends on many experimental parameters such as storage temperature, readout mechanism, annealing and radiation type or time based on the storage time before or after radiation. The general aim of the present work is to investigate if the activation energy E, frequency factor s, maximum temperature, Tm and concentration, n values evaluated from the experimental thermal fading rates glow–curves through a computerized glow–curve deconvolution analysis (CGCD), can simulate the thermal fading glow-curves using a phenomenological model for LiF:Mg, Ti.

Temperature and size dependence of photoluminescence (PL) of nano-silicon embedded in SiO2 matrix samples were studied. In these measurements, four samples with deferent implantation dose showed their similar tendency. Their nano-structure was investigated by high resolution electron microscopy (HREM) and selected area diffraction (SAD) which confirmed that only those prepared with the higher Si implantation dose formed crystal nano-silicon. The further analysis of the dependence of thermal activation energy on the PL emission energy demonstrates their different behaviors. This leads to an optical method to detect the crystal nano-silicon through comparing their thermal activation energy with the Calcott model, a model that implies the emission from nanocrystallites. Furthermore, the appearance of thermal activation energy in amorphous nano-silicon is discussed in the light of recombination mode of localized carriers through the band-tail state.

Julia code for solar thermal simulations included in "Energy Modeling of Solar Water Heating Systems with On-Off Control and Thermally Stratified Storage Using a Fast Computation Algorithm"

The building sector has a poor performance in terms of energy efficiency and is looking for alternatives to reduce the use of fossil fuels on building use stage. Renewables are unlimited and solar thermal energy is a technology with a demonstrated potential. The façade is a key element able to harness renewable energy coming from the sun becoming in an Active Solar Thermal Façade (ASTF). The main purpose of this study is the development of a parametric study using a numerical model to analyze the behavior of an unglazed solar collector. Thus, evaluating different design and meteorological parameters to show their influence on the heat transfer and the efficiency. The study shows that solar irradiation and mass flow are the most influential on thermal difference. However, for the efficiency ambient temperature and inlet temperature both are the most influencing ones. In brief, a set of parameters have a significant influence on the behavior of the ASTF that are fully governed by environmental conditions. Nevertheless, there are some other parameters that can be controlled during the operation. The challenge is to make a continuous configuration of this adaptable values depending on the external situation to achieve a higher performance for the ASTF.

Follow the methodology of the research for replication. The blue colour bar in the data is the otimised values. Please feel free to use the sorting feature in excel to sort it according to your needs.

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Caloutta-700 092 Manuscript received 20 August 1981, revised 26 January 1982, accepted 23 May 1982 Solid state dehydration of hydrated calcium salts of picolinic acid, nicotinic acid and isonicotinic acid and subsequent decarboxylation of the corresponding anhydrous salts have been studied by simultaneous TG, DTA and DTG techniques. From the analysis of the TG, DTA and DIG traces for the dehydration of the hydrated salts, the thermal stability order of the hydrates has been found to be Ca(pic)2,H2O> Ca(isoNic)2 4H2O > Ca(Nic)2,3H2O. But the trend observed in the decarboxylation process is Ca(Nic)2 > Ca(isoNic)2 > Ca(pic)2, Thermal parameters like activation energy, enthalpy change and order of reaction for each process have been computed by standard methods. An attempt has been made to correlate the trend in the thermal stability of the anhydrous salts towards decarboxylation with their molecular structure.

University of Minnesota M.S.Ch.E. thesis. August 2019. Major: Chemical Engineering. Advisors: Brian Hinderliter, Keith Lodge. 1 computer file (PDF); vi, 76 pages. ; Low Density Polyethylene (LDPE) thin film was exposed to oxygen gas overpressure and water. in a Parr Instruments pressure vessel at four temperatures 22, 50, 70 and 80°C; and, at 30 and 50 psi initial oxygen pressures. Sheet polypropylene (PP) and high-density polyethylene (HDPE) as well as injection molded HDPE, HDPP, and LDPE dogbones were exposed at 70°C and 30 psi initial oxygen pressure. Immersion of LDPE films was done under and above water at 80°C and 50 psi initial oxygen pressure. Permeation cup tests were done to determine the permeability of water vapor across the LDPE film at 60, 70, and 90°C. The extent of oxidation and functionality was monitored using ATR-FTIR and was consistent with previous work on polyethylene-oxygen reaction pathways. The permeability of the LDPE films and carbonyl content increased linearly with temperature, oxidation time, and oxygen pressure. The dogbones studied showed little change in mechanical properties.

The thermal behavior of lignins from softwood and hardwood species has been investigated using thermogravimetry and differential scanning calorimetry. Klason Lignin from Pinus taeda and Klason lignin from Eucalyptus grandis were studied. The differential scanning calorimetry results showed that both Klason lignins studied presented similar glass transition temperature. Thermogravimetric results showed that the lignin degradation occurs in three stages. The Klason lignin of Pinus taeda is more thermally stable than Eucalyptus grandis, probably because of the higher thermal stability of the guaiacyl units in softwood lignin. The degradation of both lignins initiate by a diffusion process. However when the conversion values are higher than 0,1 the lignin degradation mechanism is a complex procedure and involves the degradation of a highly condensed aromatic structure formed at the previous degradation stages.

Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012. ; High efficiency tandem selective solar absorber materials of carbon in nickel oxide (C-NiO) composite were fabricated on an aluminium substrate using a simple and cost effective sol-gel process. The process involved preparation of carbon and nickel oxide precursor sols which were homogeneously mixed to form a final C-NiO precursor sol. The carbon precursor sol was prepared by dissolving sucrose (SUC) in 8 ml of distilled water. The NiO precursor sol was prepared by dissolving 7.5 g nickel acetate in 50 ml ethanol, then adding 6.3 g diethanol amine (DEA) to stabilise the solution followed by addition of a structure directing template of polyethylene glycol (PEG). The final C-NiO precursor sol was spin coated on pre-cleaned aluminium substrate to form thin films which were then heat treated in nitrogen ambient inside a tube furnace. The final heat treatment temperature of the sols was determined by thermal studies using thermo gravimetric analytic (TGA) and differential scanning calorimetric (DSC) techniques. TGA and DSC studies of the final precursor sol showed that the weight loss of the precursors stabilised at around 450 °C. The impact of the sol-gel process parameters namely heat treatment temperature, PEG content, SUC content as well as spin coating speed on the optical properties i.e. solar absorptance (αsol) and thermal emittance (εtherm) was investigated. It was found that the optical properties as well as photo-thermal conversion efficiency, η = αsol - εtherm, improved with an increase in heat treatment temperature in the range studied (300-550 °C). This is in good agreement with the results obtained from thermo-gravimetric analysis which showed the weight loss of the precursor to stabilise around a temperature of 450 °C. Results obtained from the Raman studies showed a progressive increase in the graphitic domain in C-NiO samples with an increase in temperature. Heat treatment temperatures above 450 °C gave the best optical properties. Scanning ...