• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • Tagged with
  • 132
  • 106
  • 84
  • 11
  • 7
  • 6
  • 5
  • 5
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • 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.
1

Investigation of a hybrid wind-photovoltaic electrical energy system for a remote community

Al-Smairan, Mohammad Hamdan January 2006 (has links)
No description available.
2

Raising efficiency in photovoltaic systems : high resolution monitoring and performance analysis

Firth, Steven January 2006 (has links)
Many countries are installing photovoltaic (PV) systems as part of a shift towards a low carbon economy. This thesis describes the development of new PV system monitoring techniques to improve understanding in PV system performance. One hundred and nine domestic PV systems are studied and their energy performance is revealed through high resolution monitored data. The PV systems studied were installed from 2002 to 2004 as part of the UK Government's PV Domestic Field Trial. Located in five clusters throughout the UK, the sites are a combination of new build and retrofit projects. Each house has a separate grid-connected PV system and the 109 systems cover a variety of orientations, PV array sizes, PV module types and inverter sizes. The monitored performance data includes measurements of in-plane solar irradiance, PV module temperature, and DC and AC energy outputs. Data is recorded as five minutely average values for periods of up to two years. Data loggers store and provide access to the data through the public telephone network. New techniques have been developed to analyse the five minutely monitored data from each house directly without averaging or aggregating the values. Data quality and plausibility checks are undertaken to ensure the reliability of the measurements and the monitoring techniques are developed using data from fifty four of the PV systems. Plots of five minutely irradiance versus efficiency values show clouds of points which represent 'normal operation'. A statistical method is developed to detect faults and to separate them from the normal operation. Six types of normal operation energy losses and four types of faults are identified and these are investigated through original techniques including a method of constructing 'efficiency curves' for the different stages of normal operation and a method to detect shading based on the position of the sun. The reduction in overall annual performance caused by each type of loss and fault is calculated and the opportunities to minimise the losses and faults are investigated. This approach demonstrates a new strategy for monitoring PV systems, based on directly analysing high resolution monitored data. The method provides detailed insight into PV system performance and the results can be used to make recommendations for raising the efficiency of existing and future PV systems
3

Thin films of CuInSeâ??2 for photovoltaic devices

Knowles, Ashley Alan January 1990 (has links)
No description available.
4

Solar refrigeration : evaluation of technical options and design of a solar-generator-adsorber for a novel adsorption refrigerator

Tabassum, Alim Abid January 1989 (has links)
Various technical options for developing a solar operated refrigerator have been discussed. Their suitability for being used as a vaccine store for the conditions specified by the World Health (EPI) Organization Expanded Programme on Immunization 4have been evaluated. A model to predict the performance of a photovoltaic refrigerator have been developed and used to identify factors which influence its performance. It was concluded that it can be more competitive in areas where insolation is high and sunshine hours are long. It has been proposed that ice-lined refrigerators, which would run during the day, may be more economical and eliminate the need for a battery storage. The option of operating an 'Electrolux' absorption refrigerator with evacuated tube heat pipe collectors has been assessed. It was concluded that the operation was not possible without a major re-design of the commercially available models. However, it was proposed that coordination of the EPI with other development programmes may be useful. It is proposed to build, with this coordinated effort, biogas plants. Biogas can then fuel the modified burner of the kerosene fueled absorption refrigerators. This may well prove to be a cheaper option. Characterization of various adsorption pairs has been done using the experimental rig developed for the purpose. The influence of various properties of adsorption pairs on the performance of an adsorption refrigeration cycle has been studied. It was observed that the generation temperature in an adsorption refrigeration cycle (or a bivariant absorption system), for a specified operating regime, was only a function of the refrigerant. A relationship between the refrigerant properties and the generating temperature for specified operating conditions was developed. Using this relationship it was established that ammonia and methanol cannot be generated at temperatures below 1200C for WHO/EPI specified operating conditions, if the condenser was air-cooled. A novel idea of direct absorption of solar radiation into the activated carbon bed is put forward to combat the temperature differential of 214°C, in a conventional design of SGA, between the carbon and the metal container. The idea was practically implemented by replacing the top of the metal box by transparent glass sheet. The seal between the metal container and glass imposed practical difficulties in that design but the tests proved that the idea had potential. A new tubular design of the SGA is proposed finally which is hoped to bring improvement to the performance of activated carbon adsorption refrigerators.
5

The role of defects in the radiation damage of solar cells

Peters, Jan W. January 1993 (has links)
No description available.
6

Optical properties of some surfaces for solar energy application

Musa, Alia H. January 1980 (has links)
The present work is a study of the optical properties of some surfaces, in order to determine their applications in solar energy utilisation. An attempt has been made to investigate and measure the optical properties of two systems of surface moderately selective surfaces like thermally grown oxide of titanium, titanium oxide en aluminium and thermally grown oxides of stainless steel; and, selective surfaces of five different coloured stainless at (INCO surfaces) and of black nickel foil. A calorimetric instrument based on the steady state method for measuring directly the total emittance has been designed. Chapter 1 is an introductory survey of selective surface. It also includes a brief review of various preparation techniques in use since 1955. Chapter 2 investigates the theory of selective surfaces, defining their optical properties and their figures of merit. It also outlines the method of computing the optical properties (i.e. absorptance, a, and emittance, a) which have been adopted for the present work. Chapter 3 describes the measuring technique and the modes of operation of the equipment used in the experimental work carried out. Chapter 4 gives the results of the experimental work to measure the optical properties, the life testing and chemical composition of the surfaces under study. Chapter 5 deals with the experimentation leading to the design of a calorimetric instrument for measuring the total emmitance directly. Chapter 6 presents concluding remarks about the outcome of the present work and some suggestions for further work. sent work is a study of the optical properties of some surfaces, in order to determine their applications in solar energy utilisation. An attempt has been made to investigate and measure the optical properties of two systems of surface moderately selective surfaces like thermally grown oxide of titanium, titanium oxide en aluminium and thermally grown oxides of stainless steel; and, selective surfaces of five different coloured stainless at (INCO surfaces) and of black nickel foil. A calorimetric instrument based on the steady state method for measuring directly the total emittance has been designed. Chapter 1 is an introductory survey of selective surface. It also includes a brief review of various preparation techniques in use since 1955. Chapter 2 investigates the theory of selective surfaces, defining their optical properties and their figures of merit. It also outlines the method of computing the optical properties (i.e. absorptance, a, and emittance, a) which have been adopted for the present work. Chapter 3 describes the measuring technique and the modes of operation of the equipment used in the experimental work carried out. Chapter 4 gives the results of the experimental work to measure the optical properties, the life testing and chemical composition of the surfaces under study. Chapter 5 deals with the experimentation leading to the design of a calorimetric instrument for measuring the total emmitance directly. Chapter 6 presents concluding remarks about the outcome of the present work and some suggestions for further work.
7

The development of a solar wall module using a selective surface

Lloyd, C. G. January 1983 (has links)
A need was indicated for the identification of a possible new solar energy product to improve the sales potential of a metal film with a selective surface, manufactured by the industria I sponsor of this project (INCO). A possible way of overcoming the disadvantageous economics of solar energy collection was identified. This util ised the collection of solar energy by the walls of buildings constructed in such a manner as to allow the transfer of energy into the building, whilst providing adequate thermal insulation in the absence of sunlight. The actual collection element of the wall, being metallic, is also capable of performing the function of a low temperature heating .system in the absence of sunlight. As a result of this, the proposed system, -bydisplacing both the wa II and centra I heating system which would otherwise be necessary, demonstrates economic benefits over systems which are constructed solely forthe< purpose of collecting solar energy. The necessary thermodynamic and meteorologi.cal. chara.cteristics and data: are established, and applied to a typical urban site in the North of EngJand, for 0 typical average year, with and without a shading device incorporated into the construction. It is concluded that the proposed system may offer considerable benefit inredvc~ ing the effective heating season in all orientations of wall.
8

Studies of solar radiation and its measurement

Athwall, Punna S. January 1982 (has links)
A mathematical model has been developed for predicting the spectral distribution of solar radiation incident on a horizontal surface. The solar spectrum in the wavelength range 0.29 to 4.0 micrometers has been divided in 144 intervals. Two variables in the model are the atmospheric water vapour content and atmospheric turbidity. After allowing for absorption and scattering in the atmosphere, the spectral intensity of direct and diffuse components of radiation are computed. When the predicted radiation levels are compared with the measured values for the total radiation and the values with glass filters RG715, RG630 and OG530, a close agreement (± 5%) has been achieved under clear sky conditions. A solar radiation measuring facility, close to the centre of Birmingham, has been set up utilising a microcomputer based data logging system. A suite of computer programs in the BASIC programming language has been developed and extensively tested for solar radiation data, logging, analysis and plotting. Two commonly used instruments, the Eppley PSP pyranometer and the Kipp and Zonen CM5 pyranometer, have been compared under different experimental conditions. Three models for computing the inclined plane irradiation, using total and diffuse radiation on a horizontal surface, have been tested for Birmingham. The anisotropic-alI-sky model, proposed by Klucher, provides a good agreement between the measured and the predicted radiation levels. Measurements of solar spectral distribution, using glass filters, are also reported for a number of inclines facing South.
9

Performance of high-efficiency PV systems in a maritime climate

Strobel, Matthias Benjamin January 2008 (has links)
A unique measurement system is designed and installed to investigate the performance of high-efficiency PV systems in a high latitude maritime climate. Continuous monitoring of DC and AC currents and voltages of several inverters connected to modules of the latest generation of high-efficiency PV technologies is combined with full I-V characteristics of each module alongside high-resolution meteorological data.
10

Study of solar absorption cooling systems

Kumar, P. January 1984 (has links)
Solar energy is a vast and inexhaustible source of energy. However, solar radiation approaching the earth's surface is variable. Efficient use of this radiation is complicated by this variable nature. The work described in this thesis deals mainly with the use of solar energy for absorption cooling systems. Basic cooling and heat pump systems are described in brief. A literature survey of the absorption cooling systems is given and the scope for research work in this area is discussed. The effect of variations of the parameters in the closed cycle and open cycle absorption cooling systems has been analysed in order to optimise the performance of the systems. Experimental verification of the above analysis for a closed cycle system using water-lithium bromide as a working pair is presented along with some typical characteristic performance data for certain conditions. These conditions are lower generator temperatures, which lead to more efficient solar energy collection systems and higher absorber/condenser temperatures providing the feasibility of air cooling. Computer programs for the above analyses are given. A closed cycle absorption system using water-lithium bromide has also been theoretically analysed for simultaneous cooling and heating. A computer program developed for the above analysis is presented. A modification in the practical cycle to achieve high temperature lifts for simultaneous heating and cooling appears to be very attractive. An expression for coefficient of performance of an ideal absorption cycle system, when condensing temperature is not equal to absorber temperature, has been derived. Experimental verification of the above concept in a single stage cycle is also reported. An experimental unit to generate design data for a solar generator, of an open cycle absorption cooling system has been designed and installed. This unit is described in detail. Solar simulation has been done in two ways. The first way is by a radiation source consisting of CSI lamps and the second way is by providing an equivalent electrical heat flux. The relationship between the two is discussed. Based on the experimental data obtained, correlations in conventional forms for heat and mass transfer operations in the generator are presented. A mathematical model of the solar generator incorporating the above correlations is discussed. A computer program for the prediction of the performance of the generator is presented. The experimental results are compared with the predicted results and optimum conditions for various situations are discussed.

Page generated in 0.0657 seconds