Application of thermal energy harvesting from photovoltaic panels

This paper describes a newly developed system for harvesting thermoelectric energy from photovoltaic panels. This system helps to power monitoring systems for photovoltaic panels (PVs) in locations where there is no energy source using waste thermal energy from PVs exposed to the sun’s rays. In the study described here, the thermal energy from a PV panel was captured and transferred to a thermoelectric generator (TEG). A temperature gradient was created by reducing the temperature using an aluminium heat sink in ambient weather conditions. This temperature gradient was used to generate electricity via two TEGs. In field tests carried out in April, in Aksaray province in central Turkey, the maximum temperature gradient due to solar radiation was measured as 21.08 °C. The harvested energy was increased to a usable level of 4.1 V using a DC-to-DC converter and stored in a li-ion rechargeable battery. The maximum charge current level of the battery was 147 µA. The maximum harvested energy was 458.64 mW, and a stable level of around 350 mW was achieved. The experimental operation of the prototype system was carried out in stable weather conditions; however, weather and climatic conditions greatly affect levels of energy harvested as a result of changing temperature gradients. The energy obtained with the prototype may reduce the battery maintenance costs of PV monitoring systems and lead to the development of new such systems which cannot presently be used due to a lack of energy

Synergistic effect of natural zeolites on flame retardant additives

Thesis (Master)--Izmir Institute of Technology, Chemical Engineering, Izmir, 2004Includes bibliographical references (leaves: 93-97)Text in English; Abstract: Turkish and English97 - 92 leavesIntumescent flame retardant systems were proposed to increase flame retardancy performance of polymers without environmental hazard. An intumescent system consisting of ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and natural zeolite (clinoptilolite, Gördes II) as a synergistic agent was used in this study for flame retardancy of polypropylene (PP). APP and PER combination were examined at different ratios (0.25, 0.33, 0.5, 1, 2, 3, and 4) for optimization of formulation of flame retardancy. The zeolite was incorporated into flame retardant formulation at four different concentrations (1,2, 5, and 10wt%) to investigate synergism with the flame retardant materials. Filler content was fixed at 30w% of total amounts of flame retardant PP composites. The zeolite and APP were treated with two different coupling agents namely, 3-(trimethoxysilyl)-1-Propanethiol and (3-aminopropyl)-triethoxysilane for consideration influence of surface treatments on mechanical properties and flame retardant performance of composites.To investigate thermal behaviour of flame retardant PP composites with and without zeolite, samples were heated on optic microscope hot stage. Both of the composites behaved similarly during heating from room temperature to 203oC. Molten pentaerythritol was observed as a second phase in molten polypropylene at 203 oC. Bubble formations were not observed. Flame retardants did not cause any foam formation during processing of mixture at 190oC in rheomixer and hot press. SEM pictures of non-burnt and burnt flame retardant (FR) PP composites with and without zeolites did not reveal significant difference considering foam size and shape compared to composites without zeolite. Zeolite crystals did not exhibit any deformation during burning of composite.Flammability of FR-PP composites were determined by UL-94 flame test in air. Burning rate of composite was measured for flammable composite in atmospheric condition. The limiting oxygen index (LOI) test method provided measuring the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen that supports combustion of pure PP, zeolite reinforced PP and flame retardant PP composites. The best flame retardant performance was achieved with APP:PER(3:1)+PP+2% zeolite and APP:PER(2:1)+PP+5% zeolite formulations, exhibiting 37.4 and 38% LOI values respectively. LOI values reached maximum value 41% with mercapto silane treated APP:PER(2:1) at 5w% Zeolite PP composite Young's modulus of composites decreased with increasing amounts of APP in composite on the contrary to their elongation at break properties

Divergent thinking and mathematics achievement in Turkey: Findings from the programme for international student achievement (PISA-2003)

AbstractThe purpose of this study was to examine divergent thinking on achievement in four areas of mathematics (geometry, arithmetic, algebra, statistics and probability). The sample consisted of 4545, 15-years old Turkish students whom participated in the PİSA-2003 study. The participants completed a questionnaire and participated in mathematics test. ANOVA and MANOVA was used to identify differences if any among divergent thinker vs. non-divergent thinkers in four areas of mathematics. Results from this study indicate that divergent thinking ability plays an important role in achievement in mathematics

A review on adsorption heat pump: Problems and solutions

Adsorption heat pumps have considerably sparked attentions in recent years. The present paper covers the working principle of adsorption heat pumps, recent studies on advanced cycles, developments in adsorbent-adsorbate pairs and design of adsorbent beds. The adsorbent-adsorbate pair features for in order to be employed in the adsorption heat pumps are described. The adsorption heat pumps are compared with the vapor compression and absorption heat pumps. The problems and troubles of adsorption heat pumps are classified and researches to overcome the difficulties are discussed

Energy and Exergy Analysis of LiBr-aq and LiCl-aq Liquid Desiccant Dehumidification System

In this study, energy and exergy analysis of experimental results obtained from a dehumidification system using LiBr-aq (lithium bromide-water) and LiCl-aq (lithium chloride-water) as desiccant was made. In dehumidifier and regenerator columns polycarbonate sheets, which have not been used before, were used as packing material to increase contact area in purposed liquid desiccant dehumidification system. In the analysis, variation of electrical coefficient of performance and exergy efficiency with airflow rate for different solution mass flow rates were investigated. Because of investigation, maximum values of electrical coefficient of performance and exergy efficiency were calculated approximately as 2.8 and 18%, respectively

Predviđanje optimalne gustoće ekspandiranog polistirena za najbolje performanse toplinske izolacije polistirenske kompozitne iverice primjenom umjetne neuronske mreže

The objective of this study is to predict the optimum expanded polystyrene (EPS) densities for the best insulation properties of the particleboards manufactured with waste EPS instead of formaldehyde-based adhesives used in particleboard production with artificial neural network (ANN). For this purpose, the waste EPS particles of five different densities were used in the production of composite particleboards. The experimental dana used in the study were obtained from the previous study. Half of the beech, poplar, alder, pine and spruce chips were dried in a drying oven and the other half were naturally conditioned at room temperature, and then 18 mm thick three-layer composite particleboards were produced. The thermal conductivity of panels was determined according to ASTM C 518. The prediction model with the best performance and acceptable deviations was determined by using statistical and graphical comparisons between the experimental data and the prediction values obtained as a result of ANN analysis. Then, using this prediction model, the thermal conductivity coefficient values were estimated for the intermediate EPS densities that were not experimentally tested. According to the analysis findings, the thermal insulation performance for both beech and spruce polystyrene composite particleboards (PCP) panels increased with using of waste EPS foams with a density of 30 kg/m3. The lowest thermal conductivity values were obtained from the EPS waste foams with the density of 18, 13 and 22 kg/m3 for the PCP panels produced with poplar, alder and pine in the natural drying, respectively. In the technical drying, these values were found to be 15, 14 and 11-13 kg/m3, respectively. Technical drying showed much better thermal performance than natural drying while poplar indicated the best performance among the wood species.Cilj je ove studije primjenom umjetne neuronske mreže (ANN) predvidjeti optimalne gustoće ekspandiranog polistirena (EPS) radi postizanja najboljih izolacijskih svojstava iverice proizvedene s otpadnim EPS-om umjesto s ljepilom na bazi formaldehida, kakvo se rabi u proizvodnji iverice. Stoga je za proizvodnju iverice upotrijebljen otpadni EPS pet različitih gustoća. Eksperimentalni podatci primijenjeni u studiji dobiveni su prijašnjim istraživanjem. Jedna je polovica iverja bukovine, topolovine, johovine, borovine i smrekovine osušena u sušioniku, a druga je polovica iverja kondicionirana na sobnoj temperaturi. Od osušenoga i kondicioniranog iverja proizvedene su troslojne kompozitne iverice debljine 18 mm. Toplinska vodljivost ploča određena je metodom ASTM C 518. Predikcijski model najboljih svojstava i prihvatljivih devijacija određen je statističkom i grafičkom usporedbom eksperimentalnih podataka s vrijednostima predviđenima ANN analizom. Potom su primjenom predikcijskog modela procijenjeni koeficijenti toplinske vodljivosti za one gustoće ekspandiranog polistirena koje nisu eksperimentalno ispitane. Prema toj analizi, termoizolacijska svojstva polistirenske kompozitne iverice (PCP) od bukovine i smrekovine poboljšana su pjenom od otpadnog EPS-a gustoće 30 kg/m3. Najniže vrijednosti toplinske vodljivosti za polistirensku kompozitnu ivericu od prirodno osušene topolovine, johovine i borovine dobivene su uz uporabu pjene otpadnog ESP-a gustoće 18, 13 i 22 kg/m3. Za polistirensku kompozitnu ivericu od tehnički osušenog iverja te su vrijednosti bile 15, 14 i 11-13 kg/m3. Tehničkim sušenjem iverja postignuta su znatno bolja toplinska svojstva polistirenske kompozitne iverice nego prirodnim sušenjem, a topolovina je pokazala najbolja svojstva od svih ispitivanih vrsta drva

Execution technique and pigment characteristics of Byzantine wall paintings of Anaia Church in Western Anatolia

In this study, material characteristics of wall paintings executed in 11th Century Byzantine Church located in archaeological site of Anaia (Turkey) were investigated to provide historical information of the painting techniques. For this purpose, physical, chemical and mineralogical compositions of the paintings were determined by X-Ray Diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy coupled with Energy Dispersive spectroscopy and Thermo-Gravimetric Analysis. Analysis results indicated that the paintings were executed using lime-secco technique. In this technique, pigments were mixed with lime and applied on a smooth plaster layer. Pigments used were mainly iron oxides for red, yellow and purple paintings, aluminosilicates such as celadonite for green paintings and lazurite for dark blue paintings

Comparison of thermal performances of plywood shear walls produced with different thermal insulation materials

Shear walls are one of the envelopes of light-frame wooden buildings where thermal insulation is most required. The thermal performance of shear walls can vary according to the type, properties and thickness of the wood and insulation materials used in their production. In this study, it was aimed to compare the thermal performances of plywood shear walls produced with different thermal insulation materials. For this aim, the archetype walls with properties similar to commonly used plywood shear walls were designed and produced for each thermal insulation material type and wood specie. The shear wall groups were formed by using Scots pine (Pinus sylvestris), black pine (Pinus nigra) and spruce (Picea orientalis) as wood species and cellulose, flax, felt, XPS, EPS, sheep’s, rock and glass wool as thermal insulation materials. Thermal conductivity of the shear wall groups was determined according to the ASTM C518-04 standard. Thermal resistance and other thermal performance parameters were calculated using the thermal conductivity values. As a result of the study, rock wool was the best thermal insulation material among the Scots pine shear wall groups while glass wool was the best thermal insulation material among the black pine and spruce shear wall groups. The shear walls produced with EPS foam boards indicated the worst thermal performance among all group

The effect of different fineness values of Afşin Elbistan fly ash on permeability in concrete

Too much CO2 is released during cement production. In many researches, the use of natural or recycled compounds plays an important role in the cement composition. The use of these components contributes both to reducing the amount of waste and to protecting the environment in nature. It is possible to produce an environmentally friendly concrete, thanks to its being a fly ash thermal power plant waste and its use as mineral additive in terms of its composition. In this study, it is aimed to produce impermeable concretes with the use of C type fly ash as substitutes for cement in concrete composition in substitution rates of 10 %, 30 % and 50 %. In order to reduce the permeability of concrete in this direction, as a result of grinding the fly ash in the ball mill for 0, 10, 20, 30, 45 and 60 minutes, concrete samples were prepared with and without admixture (Reference). Capillarity test was performed to determine the permeability at the end of cure periods of 28 and 90 days on concrete samples. According to the results obtained at the end of 28 days, the best impermeability was achieved in the mixture with 50 % fly ash replacement and 60 minutes grinding time. In 90 days, the best impermeability was obtained in the mixture with 30 % fly ash replacement and 0 minutes of grinding time. As a result, it was seen that permeability decreased with increasing thinness and substitution rate of fly ash in concrete composition