Incorporation of hybrid phase change materials in plastering mortars for increased energy efficiency in buildings

Tese de Doutoramento em Engenharia Civil.

Compact thermal storage: a-state-of-the-art review of experimental results

Thermal energy storage (TES) can increase the thermal energy effieresa, of a process by reusing the waste heat from industrial process, solar energy or other sources. There are different ways to store thermal energy: by sensible heat, by latest heat, by sorption process or by chemical reaction. This thesrs provides a-state-of-the-art review of the experimental performance of TES systems based on solid gas sorption process and chemical reactions. The importance of theses processes is that provides a heat loss free storage system with a high energy density.

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Photoacoustic studies on thermal parameters of liquid crystal mixtures

Complete thermal characterization of liquid crystal mixtures in the smectic phase consisting of various relative volume fractions of cholesterol and 1-hexadecanol have been carried out using the photoacoustic technique. Thermal diffusivity values of these liquid crystal mixtures are evaluated using the open cell photoacoustic technique whereas the thermal effusivity value is measured using the conventional photoacoustic technique. From the measured values of these transient thermophysical parameters, the thermal conductivity and heat capacity of the sample under investigation are calculated. Analyses of the results show that all the thermophysical parameters depend strongly on the volume fraction of the constituents. Results are interpreted in terms of enhanced hydrogen bonding and the consequent enhancement in cohesive thermal energy transport with increasing volume fraction of 1-hexadecanol

Evaluation of electrical conductivity and thermal diffusivity of vanadyl naphthalocyanine

The electrical conductivity and thermal diffusivity of pristine and iodine doped vanadyl naphthalocyanine (VONc) were studied. In the pristine sample, the temperature dependence was very weak below 300 K. The increase in conductivity at higher temperature must be due to an enhancement in carrier density with increase in thermal energy. The electrical conductivity of VONc increased when doped with iodine. The behavior of VONcI indicated that considerable changes have occurred in the electronic environment of the molecule as a result of doping. Iodine doping enhanced the thermal diffusivity of VONc. The increase in thermal diffusivity of the iodine doped sample may be due to the disorder of iodine atoms occupying the channels in one dimensional lattices.

Studies on energy exchange between sea and atmosphere from the indian ocean with special reference to arabian sea and bay of bengal

There are only a few attempts in the Indian ocean to evolve reliable climatic models of energy exchange fluxes and to study their inter annul variations. Large space scale and time history of the flux fields could be estimated by the bulk aerodynamic exchange and radiation equation, making use of the climatic normal’s of the related parameters derived from the remarkably good amount of surface marine observations compiled and made available on magnetic tape TDF II by the national climatic centre of NOAA for the period of years 1854 –early 1973. In this thesis the author has made an attempt to calculate the thermal energy exchange fluxes in a meaningful way, using the bulk aerodynamic coefficients which depend on the changes in the wind speed. The spatial and temporal distribution of the exchanges of energy between the ocean and atmosphere , are presented and their impact on the climatic variations of the Indian ocean are discussed from the point of view of predominating air sea interaction processes.

Assessment of Energy Conservation in Indian Cement Industry and Forecasting of Co2 Emissions

Cement industry ranks 2nd in energy consumption among the industries in India. It is one of the major emitter of CO2, due to combustion of fossil fuel and calcination process. As the huge amount of CO2 emissions cause severe environment problems, the efficient and effective utilization of energy is a major concern in Indian cement industry. The main objective of the research work is to assess the energy cosumption and energy conservation of the Indian cement industry and to predict future trends in cement production and reduction of CO2 emissions. In order to achieve this objective, a detailed energy and exergy analysis of a typical cement plant in Kerala was carried out. The data on fuel usage, electricity consumption, amount of clinker and cement production were also collected from a few selected cement industries in India for the period 2001 - 2010 and the CO2 emissions were estimated. A complete decomposition method was used for the analysis of change in CO2 emissions during the period 2001 - 2010 by categorising the cement industries according to the specific thermal energy consumption. A basic forecasting model for the cement production trend was developed by using the system dynamic approach and the model was validated with the data collected from the selected cement industries. The cement production and CO2 emissions from the industries were also predicted with the base year as 2010. The sensitivity analysis of the forecasting model was conducted and found satisfactory. The model was then modified for the total cement production in India to predict the cement production and CO2 emissions for the next 21 years under three different scenarios. The parmeters that influence CO2 emissions like population and GDP growth rate, demand of cement and its production, clinker consumption and energy utilization are incorporated in these scenarios. The existing growth rate of the population and cement production in the year 2010 were used in the baseline scenario. In the scenario-1 (S1) the growth rate of population was assumed to be gradually decreasing and finally reach zero by the year 2030, while in scenario-2 (S2) a faster decline in the growth rate was assumed such that zero growth rate is achieved in the year 2020. The mitigation strategiesfor the reduction of CO2 emissions from the cement production were identified and analyzed in the energy management scenarioThe energy and exergy analysis of the raw mill of the cement plant revealed that the exergy utilization was worse than energy utilization. The energy analysis of the kiln system showed that around 38% of heat energy is wasted through exhaust gases of the preheater and cooler of the kiln sysetm. This could be recovered by the waste heat recovery system. A secondary insulation shell was also recommended for the kiln in the plant in order to prevent heat loss and enhance the efficiency of the plant. The decomposition analysis of the change in CO2 emissions during 2001- 2010 showed that the activity effect was the main factor for CO2 emissions for the cement industries since it is directly dependent on economic growth of the country. The forecasting model showed that 15.22% and 29.44% of CO2 emissions reduction can be achieved by the year 2030 in scenario- (S1) and scenario-2 (S2) respectively. In analysing the energy management scenario, it was assumed that 25% of electrical energy supply to the cement plants is replaced by renewable energy. The analysis revealed that the recovery of waste heat and the use of renewable energy could lead to decline in CO2 emissions 7.1% for baseline scenario, 10.9 % in scenario-1 (S1) and 11.16% in scenario-2 (S2) in 2030. The combined scenario considering population stabilization by the year 2020, 25% of contribution from renewable energy sources of the cement industry and 38% thermal energy from the waste heat streams shows that CO2 emissions from Indian cement industry could be reduced by nearly 37% in the year 2030. This would reduce a substantial level of greenhouse gas load to the environment. The cement industry will remain one of the critical sectors for India to meet its CO2 emissions reduction target. India’s cement production will continue to grow in the near future due to its GDP growth. The control of population, improvement in plant efficiency and use of renewable energy are the important options for the mitigation of CO2 emissions from Indian cement industries

Impact of sward type, cutting date and conditioning temperature on mass and energy flows in the integrated generation of solid fuel and biogas from semi-natural grassland

Energy production from biomass and the conservation of ecologically valuable grassland habitats are two important issues of agriculture today. The combination of a bioenergy production, which minimises environmental impacts and competition with food production for land with a conversion of semi-natural grasslands through new utilization alternatives for the biomass, led to the development of the IFBB process. Its basic principle is the separation of biomass into a liquid fraction (press fluid, PF) for the production of electric and thermal energy after anaerobic digestion to biogas and a solid fraction (press cake, PC) for the production of thermal energy through combustion. This study was undertaken to explore mass and energy flows as well as quality aspects of energy carriers within the IFBB process and determine their dependency on biomass-related and technical parameters. Two experiments were conducted, in which biomass from semi-natural grassland was conserved as silage and subjected to a hydrothermal conditioning and a subsequent mechanical dehydration with a screw press. Methane yield of the PF and the untreated silage was determined in anaerobic digestion experiments in batch fermenters at 37°C with a fermentation time of 13-15 and 27-35 days for the PF and the silage, respectively. Concentrations of dry matter (DM), ash, crude protein (CP), crude fibre (CF), ether extract (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF), acid detergent ligning (ADL) and elements (K, Mg, Ca, Cl, N, S, P, C, H, N) were determined in the untreated biomass and the PC. Higher heating value (HHV) and ash softening temperature (AST) were calculated based on elemental concentration. Chemical composition of the PF and mass flows of all plant compounds into the PF were calculated. In the first experiment, biomass from five different semi-natural grassland swards (Arrhenaterion I and II, Caricion fuscae, Filipendulion ulmariae, Polygono-Trisetion) was harvested at one late sampling (19 July or 31 August) and ensiled. Each silage was subjected to three different temperature treatments (5°C, 60°C, 80°C) during hydrothermal conditioning. Based on observed methane yields and HHV as energy output parameters as well as literature-based and observed energy input parameters, energy and green house gas (GHG) balances were calculated for IFBB and two reference conversion processes, whole-crop digestion of untreated silage (WCD) and combustion of hay (CH). In the second experiment, biomass from one single semi-natural grassland sward (Arrhenaterion) was harvested at eight consecutive dates (27/04, 02/05, 09/05, 16/05, 24/05, 31/05, 11/06, 21/06) and ensiled. Each silage was subjected to six different treatments (no hydrothermal conditioning and hydrothermal conditioning at 10°C, 30°C, 50°C, 70°C, 90°C). Energy balance was calculated for IFBB and WCD. Multiple regression models were developed to predict mass flows, concentrations of elements in the PC, concentration of organic compounds in the PF and energy conversion efficiency of the IFBB process from temperature of hydrothermal conditioning as well as NDF and DM concentration in the silage. Results showed a relative reduction of ash and all elements detrimental for combustion in the PC compared to the untreated biomass of 20-90%. Reduction was highest for K and Cl and lowest for N. HHV of PC and untreated biomass were in a comparable range (17.8-19.5 MJ kg-1 DM), but AST of PC was higher (1156-1254°C). Methane yields of PF were higher compared to those of WCD when the biomass was harvested late (end of May and later) and in a comparable range when the biomass was harvested early and ranged from 332 to 458 LN kg-1 VS. Regarding energy and GHG balances, IFBB, with a net energy yield of 11.9-14.1 MWh ha-1, a conversion efficiency of 0.43-0.51, and GHG mitigation of 3.6-4.4 t CO2eq ha-1, performed better than WCD, but worse than CH. WCD produces thermal and electric energy with low efficiency, CH produces only thermal energy with a low quality solid fuel with high efficiency, IFBB produces thermal and electric energy with a solid fuel of high quality with medium efficiency. Regression models were able to predict target parameters with high accuracy (R2=0.70-0.99). The influence of increasing temperature of hydrothermal conditioning was an increase of mass flows, a decrease of element concentrations in the PC and a differing effect on energy conversion efficiency. The influence of increasing NDF concentration of the silage was a differing effect on mass flows, a decrease of element concentrations in the PC and an increase of energy conversion efficiency. The influence of increasing DM concentration of the silage was a decrease of mass flows, an increase of element concentrations in the PC and an increase of energy conversion efficiency. Based on the models an optimised IFBB process would be obtained with a medium temperature of hydrothermal conditioning (50°C), high NDF concentrations in the silage and medium DM concentrations of the silage.

Measurement of thermal neutron cross section and resonance integral for the (165)Ho(n, gamma)(166g)Ho reaction

The ground state thermal neutron cross section and the resonance integral for the (165)Ho(n, gamma)(166)Ho reaction in thermal and 1/E regions, respectively, of a thermal reactor neutron spectrum have been measured experimentally by activation technique. The reaction product, (166)Ho in the ground state, is gaining considerable importance as a therapeutic radionuclide and precisely measured data of the reaction are of significance from the fundamental point of view as well as for application. In this work, the spectrographically pure holmium oxide (Ho(2)O(3)) powder samples were irradiated with and without cadmium covers at the IEA-RI reactor (IPEN, Sao Paulo), Brazil. The deviation of the neutron spectrum shape from 1/E law was measured by co-irradiating Co, Zn, Zr and Au activation detectors with thermal and epithermal neutrons followed by regression and iterative procedures. The magnitudes of the discrepancies that can occur in measurements made with the ideal 1/E law considerations in the epithermal range were studied. The measured thermal neutron cross section at the Maxwellian averaged thermal energy of 0.0253 eV is 59.0 +/- 2.1 b and for the resonance integral 657 +/- 36b. The results are measured with good precision and indicated a consistency trend to resolve the discrepant status of the literature data. The results are compared with the values in main libraries such as ENDF/B-VII, JEF-2.2 and JENDL-3.2, and with other measurements in the literature.

Evaluation of a high temperature solar thermal seasonal borehole storage

A solar thermal system with seasonal borehole storage for heating of a residential area in Anneberg, Sweden, approximately 10 km north of Stockholm, has been in operation since late 2002. Originally, the project was part of the EU THERMIE project “Large-scale Solar Heating Systems for Housing Developments” (REB/0061/97) and was the first solar heating plant in Europe with borehole storage in rock not utilizing a heat pump. Earlier evaluations of the system show lower performance than the preliminary simulation study, with residents complaining of a high use of electricity for domestic hot water (DHW) preparation and auxiliary heating. One explanation mentioned in the earlier evaluations is that the borehole storage had not yet reached “steady state” temperatures at the time of evaluation. Many years have passed since then and this paper presents results from a new evaluation. The main aim of this work is to evaluate the current performance of the system based on several key figures, as well as on system function based on available measurement data. The analysis show that though the borehole storage now has reached a quasi-steady state and operates as intended, the auxiliary electricity consumption is much higher than the original design values largely due to high losses in the distribution network, higher heat loads as well as lower solar gains.

Thermal Evaluation of a Solarus PV-T collector

Low concentrator PV-T hybrid systems produce both electricity and thermal energy; this fact increases the overall efficiency of the system and reduces the cost of solar electricity. These systems use concentrators which are optical devices that concentrate sunlight on to solar cells and reduce expensive solar cell area. This thesis work deals with the thermal evaluation of a PV-T collector from Solarus.Firstly the thermal efficiency of the low concentrator collector was characterized for the thermal-collector without PV cells on the absorber. Only two types of paint were on the absorber, one for each trough of the collector. Both paints are black one is glossy and the other is dull,. The thermal efficiency at no temperature difference between collector and ambient for these two types of paint was 0.65 and 0.64 respectively; the U-value was 8.4 W/m2°C for the trough with the glossy type of paint and 8.6 W/m2°C for the trough with dull type of paint. The annual thermal output of these two paints was calculated for two different geographic locations, Casablanca, Morocco and Älvkarleby, Sweden.Secondly the thermal efficiency was defined for the PV-T collector with PV cells on the absorber. The PV cells cover 85% of the absorber, without any paint on the rest of the absorber area. We also tested how the electrical power output influences the thermal power output of the PV-T collector. The thermal and total performances for the PV-T collector were only characterized with reflector sides, because of the lack of time we could not characterize them with transparent sides also.

Refrigerator COP with thermal storage

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effects of rotation in the laser-pulse photoassociation in a thermal gas of atoms

Photoassociation is a possible route for the formation of chemical bonds. In this process, the binding of colliding atoms can be induced by means of a laser field. Photoassociation has been studied in the ultracold regime and also with temperatures well above millikelvins in the thermal energy domain, which is a situation commonly encountered in the laboratory. A photoassociation mechanism can be envisioned based on the use of infrared pulses to drive a transition from free colliding atoms on the electronic ground state to form a molecule directly on that state. This work takes a step in this direction, investigating the laser-pulse-driven formation of heteronuclear diatomic molecules in a thermal gas of atoms including rotational effects. Based on the assumption of full system controllability, the maximum possible photoassociation yield is deduced. The photoassociation probability is calculated as a function of the laser parameters for different temperatures. Additionally, the photoassociation yield induced by subpicosecond pulses of a priori fixed shape is compared to the maximum possible yield.

EFFECT OF THERMAL TREATMENT ON THE CHEMICAL CHARACTERISTICS OF WOOD FROM Eucalyptus grandis W. Hill ex Maiden UNDER DIFFERENT ATMOSPHERIC CONDITIONS

Thermal treatment (thermal rectification) is a process in which technological properties of wood are modified using thermal energy, the result of Which is often value-added wood. Thermally treated wood takes on similar color shades to tropical woods and offers considerable resistance to destructive microorganisms and climate action, in addition to having high dimensional stability and low hygroscopicity. Wood samples of Eucalyptus grandis were subjected to various thermal treatments, as performed in presence (140 degrees C; 160 degrees C; 180 degrees C) or in absence of oxygen (160 degrees C; 180 degrees C; 200 degrees C) inside a thermal treatment chamber, and then studied as to their chemical characteristics. Increasing the maximum treatment temperatures led to a reduction in the holocellulose content of samples as a result of the degradation and volatilization of hemicelluloses, also leading to an increase in the relative lignin content. Except for glucose, all monosaccharide levels were found to decrease in samples after the thermal treatment at a maximum temperature of 200 degrees C. The thermal treatment above 160 degrees C led to increased levels of total extractives in the wood samples, probably ascribed to the emergence of low molecular weight substances as a result of thermal degradation. Overall, it was not possible to clearly determine the effect of presence or absence of oxygen in the air during thermal treatment on the chemical characteristics of the relevant wood samples.