• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 436
  • 312
  • 61
  • 44
  • 41
  • 28
  • 18
  • 13
  • 11
  • 11
  • 11
  • 11
  • 11
  • 11
  • 8
  • Tagged with
  • 1231
  • 1231
  • 310
  • 262
  • 171
  • 167
  • 143
  • 136
  • 116
  • 101
  • 90
  • 88
  • 80
  • 80
  • 79
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Measurement and modelling tools for the evaluation of directional optical and thermal radiation properties of glazing

Van Nijnatten, Peter A. January 2002 (has links)
No description available.
62

Accurate spectrophotometric optical properties measurement techniques for solar energy materials

Squire, Theresa-Jane January 1999 (has links)
No description available.
63

An economic appraisal of building-integrated photovoltaics

Eiffert, Patrina January 1998 (has links)
No description available.
64

Passive solar energy and buildings : including shading and climate of Saudi Arabia

Joudah, Nabeel Addul-Rahman January 1992 (has links)
Climate is a major determinant in building design. There has been a long standing need by designers and architects, as well as engineers, in Saudi Arabia for easy access to hourly climatic data. Such data are essential for many passive and active solar applications, including the simulation of the energy performance of building designs. A major contribution of the present study lies in the development of a Reference Year representative of the climate in Saudi Arabia. This reference year compensates the scarcity and inadequate climatic data presently published in Saudi Arabia. It also provides substantial data base of climatic variable for use in simulation programs, not only for Saudi Arabia, but also for similar hot-arid regions. The present study also bridges the gap, currently observed in literature and research, concerning the energy performance of internal shading devices. These devices, and in particular curtains and blinds, are quite common features in our living spaces. T he effects such devices have on the energy balance of indoor spaces and the comfort of occupants, can be assessed by the simplified design tools developed in the present study. The characteristics of two samples (a domestic curtain and a low-e coated blind) have been measured using outdoor test rooms at the "Passys" test site. Results have indicated that the blind is more effective than the domestic curtain. The blind can reduce the transmission coefficient of double glazed fenestration by 11%, and can reduce the solar heat gain factor by 34%. In comparison, the curtain reduces the fenestration heat transmission coefficient and solar heat gain factor by 8% and 29% respectively. Results from the simulation programs "ESP" and "Curtain" have been compared with measured parameters. The analysis have provided confidence in such tools. This thesis has been structured to be of value to architects. The effort put forward in the layout and presentation of the thesis provide a readable and easy to understand research material. The reviews, results, and analysis covered in this thesis would be useful for further research.
65

Ground-based high energy power beaming in support of spacecraft power requirements

Guoan, Christopher M. 06 1900 (has links)
This thesis investigates the feasibility of projecting ground-based laser power to energize a spacecraft electrical bus via the solar panels. The energy is projected through a telescope, using modern optical compensation systems, at controlled wavelengths. Research conducted on high-energy lasers has matured to the point today, that the bulk of the power required by spacecraft on orbit can be projected from the surface of the earth. With battery life being the greatest limitation on spacecraft lifespan, the ability to provide electrical power from the surface to a satellite in eclipse with degraded batteries could mean multi-billion dollar cost savings by extending the lifetime of current and future satellites. / US Navy (USN) author.
66

A study of various forms of CdS solar cells

Pande, Piyush Chandra January 1984 (has links)
No description available.
67

Computational study of chalcogenide based solar energy materials

Dongho Nguimdo, Guy Moise January 2016 (has links)
A thesis submitted to the Faculty of Science, in fulfilment of the requirements for the degree of Doctor of Philosophy. University of the Witwatersrand, Johannesburg May 23, 2016 / Amongst the major technological challenges of the twenty rst century is the harvesting of renewable energy sources. We studied the solar cell performance of the ternary compounds AgAlX2 (X = S, Se and Te) and AgInS2 as promising materials for meeting this challenge. Structural, electronic and optical properties of the compounds were investigated by means of the density functional theory and many body perturbation theory. Using cohesive energy and enthalpy, we found that among six potential phases of AgAlX2 and AgInS2, the chalcopyrite and the orthorhombic structures were very competitive as zero pressure phases. We predicted a low pressure-induced phase transition from the chalcopyrite phase to a rhombohedral phase. For the chalcopyrite phase, we found that the tetragonal distortion and anion displacement were the cause of the crystal eld splitting. The bandgaps from the general gradient approximation PBEsol were underestimated when compared to experiment and accurate bandgaps were obtained from the hybrid functioanl HSE06, the meta-general gradient approximation MBJ and GW approximation. Optical absorption from the Bethe-Selpeter equation indicated the presence of bound exciton in AgAlX2. We estimated the solar cell performance of the compounds using the Shockley and Queisser model and the spectroscopy limited maximum e ciency approach. We found that apart from AgAlS2, the estimated theoretical e ciency of the other compounds was greater that 13 %.
68

Efficient power management design for energy harvesting biomedical applications

Chen, Zhi Yuan January 2018 (has links)
University of Macau / Faculty of Science and Technology. / Department of Electrical and Computer Engineering
69

An investigation into the sensitivity of the performance of an active solar heating system to the control strategy employed

Reynell, M. J. W. January 1985 (has links)
The aim of this thesis was to investigate and challenge current thinking regarding the sensitivity of the thermal performance of active solar water heating systems to the control strategy employed, with particular attention to the effect of the control temperature differential settings between the solar absorber plate and the solar store at which the circulating pump is switched on and off (dTon and dToff). A mathematical analysis suggested that the performance should be more sensitive to the above parameters than is generally believed. The theoretical appraisal also suggested a relationship for the ratio dTon/dToff required for stable pump control. Measured data from a large-scale solar heating field trial were carefully correlated with the predictions of a computer model. The calibrated model was then used to carry out a sensitivity analysis into the effect of altering the control criteria. The results have shown that, contrary to current thinking, the long-term thermal performance of the system is significantly impaired by the use of a pump switch-on criterion (dTon) higher than 6°K, and that the sensitivity to this parameter increases with increasing dTon. The results have also revealed that the heat losses throughout the system are five or six times higher than theoretical calculations based on the insulation manufacturers' specifications predict. This is not an isolated result, but has been experienced on other monitored installations, and the implication is that the quoted figures for insulation performance (which are derived from tests under tightly controlled laboratory conditions) are extremely difficult to achieve in practice. It is argued that the above two observations are linked, and that a high switch-on criterion leads to significant amounts of collectable solar radiation being wasted as the collector absorber plate loses heat to the surrounding air without reaching a temperature sufficient to turn the circulating pump on. The effect of the control settings on pump switching stability was also investigated, and, whilst the point at which instability occurred did not agree precisely with the theoretical value, the general relationship between the ratio dTon/dToff and the number of pump switching cycles per year supported the mathematical hypothesis. The discrepancy was attributed to the difficulty of measuring the collector overall heat loss coefficient, U1, precisely. For the installation under study it was found that a value of dTon/dToff above 8 would ensure stable pump control. Interpreting optimum performance in terms of both annual solar energy output and pump switching stability, the combination of all the above results led to the general recommendation that a pump switch-on setting of 4-6°K with a switch-off setting of 0.1-0.5°K should be employed to achieve optimum performance of a solar water heating system utilising flat plate solar collectors in the UK. The switch-on criterion of 4-6°K can be achieved reasonably easily by the use of standard, inexpensive controllers and nickel-based temperature sensors. However, such controllers are not capable of consistently resolving temperature differentials to the degree required to meet the switch-off criterion of 0.1-0.5°K over the full operating temperature range. For large installations, therefore, the use of high quality controllers with calibrated platinum resistance thermometers as temperature sensors will prove cost-effective and is strongly recommended.
70

The cost of passive solar energy

Meyer, John Irving January 1977 (has links)
Thesis. 1977. M.Arch.A.S.--Massachusetts Institute of Technology. Dept. of Architecture. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / by John I. Meyer, Jr. / M.Arch.A.S.

Page generated in 0.0659 seconds