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Reference is increasingly being made towards the need for the world to find new and renewable forms of energy, especially for electric power generation, but also for space heating and the heating of water. Solar energy is one of the cheapest forms of renewable energy available and is so far one of the most underutilised resources. One contribution makes reference to the way forward as being ‘using concentrating solar power which uses parabolic mirrors to focus the solar heat (energy) and generate steam to drive electric generators’ as is currently happening in the utility power marketplace in the USA. This thesis deals with the issues surrounding the original development of a two axis solar energy tracking system (SET) in 1997. The subsequent redesign, development and upgrade, undertaken from 2002 to 2006, with its performance and efficiency being measured in 2006 and 2007 using a specially configured measurement and recording system. A Solar Energy Tracker (SET) is designed to track the sun moving in two axes, reflecting the solar radiation received on its mirrors to a target mounted at the end of a boom, at the focal point of the mirrors. In late 2005 and early 2006, a solar thermal hot water manufacturer and installer heard about the developments and requested some form of involvement, especially if Christchurch Polytechnic Institute of Technology (CPIT) provided research input and assisted in the further development and testing of solar thermal hot water systems. This sponsor offered two projects in 2006 and again in 2007. Other solar thermal hot water suppliers also requested involvement in the research and development being performed at CPIT, which led in August 2006, December 2006, June 2007 and December 2007, to a number of other solar thermal hot water and air wall systems being installed. Progressively, the roof of C block at CPIT has become full of solar thermal hot water systems and solar air wall systems, both of the conventional type and those with newer technologies at the core of their development. This thesis outlines the stages in the redesign and development of the SET, and the various stages in its testing, development and refinement up to its present form. The thesis chapters are written based around the mechanical and electrical design, the auto-tracking and daylight controls, the PLC (programmable logic controller) controller, the mirror and substrate testing, the SCADA (Supervisory Control And Data Acquisition) system, the testing and comparison with other domestic solar thermal hot water systems and finally the testing of the SET itself. It also details the future developments and outlines possible uses for the SET in its redefined form. With clean and polished mirrors the SET has proven itself capable of achieving a temperature rise across the target of 15 °C at a flow rate of 4 l/m. On some occasions this temperature rise can be in excess of 20 °C, but testing thus far, has shown this cannot be sustained for any worthwhile period of time (15-30 minutes). This translates to an efficiency of 5-10 % when related to an energy produced per twenty four hour time period. However, if the efficiency is calculated for the actual period of generation, ‘generation efficiency,’ then this figure rises to 24 %. An overview is given of associated solar thermal hot water and solar air wall system research and development (that is ongoing at CPIT) as well as the performance and efficiency graphs for the solar thermal hot water systems on test. No manufacturer’s, industry or brand trade names are mentioned, as this research is still confidential and commercially sensitive. However, the technology involved and characterised by each solar thermal system is recorded in a generic sense. The SET was originally developed with the purpose of heating hot water and today this is still the intent. The possible applications for this hot water are many and varied from electricity generation, space heating and further into developing or new industrial processes. The performances of the other domestic solar thermal hot water systems currently under test, are compared with the figures from the SET, with the maximum efficiency, presently available, being from an evacuated tube heat pipe system at up to 65 %, whereas traditional finned flat plate technologies have efficiencies after twelve months of up to 48 %.

The increasing global energy demand, which today is mainly supplied by energy sources with a fossil origin, is a severe threat to the environment and to the security of supply. In order to handle these problems, renewable energy sources are promoted globally as well as nationally in Sweden. Solar photovoltaic (PV) technology is one of the most mature and commercial renewable energy technologies and could play a vital role in phasing out fossil energy sources. In the emerging, promising concept of solar landfills, PV systems are installed on closed landfill sites in order to combine renewable electricity production with resource efficient use of land. In this study the legal, technical and financial aspects concerning a solar landfill project in a Swedish setting were investigated. Additionally, the potential of the concept on a regional level in Sweden was analysed. The methodology used in the study featured literature research, interviews, and a feasibility assessment of a solar landfill project on Visby landfill. Regarding the legal aspects linked to a solar landfill project, an inconsistency between Swedish municipalities concerning the need of a building permit for a ground mounted PV system was revealed in the study. While some municipalities demand a building permit, others do not. Additionally, the fact that a closed landfill usually is classified as an environmentally hazardous activity doesn’t result in any need for additional permissions for a PV system installation on a closed landfill. Therefore, such legal aspects are not likely to hinder a solar landfill project to any great extent. Considering the technical aspects, the choice of mounting system must be done carefully because of the special conditions which exist on a landfill site; such as ground penetration restrictions and risks of settlement. While a ballasted mounting system can avoid ground penetration, a driven pile mounting system generally features a lighter construction. Furthermore, a fixed tilt mounting system is preferred over a sun tracking mounting system due to the extra weight and sensitivity to settlement which comes with the latter choice. Regarding the choice of PV modules, thin film modules generally feature a lower weight and can therefore be advantageous in comparison with crystalline silicon modules. In the case of Visby landfill, where penetration was preferred to be avoided but where the risk of settlement was considered low, the PV system which was deemed most suitable for the site featured a ballasted fixed tilt mounting system with crystalline silicon PV modules. Considering the financial aspects, the study emphasises the importance of using the produced electricity to offset consumed electricity in order to enable a sound investment. This can be done by a wise choice of owning and financing structure where the produced electricity offsets consumed electricity for a large consumer, e.g. an industry or a grocery store, or for a number of residences in a community solar. The economic feasibility also heavily depends on the projects’ possibility to use policy incentives and tax exemptions. The feasibility assessment of Visby landfill showed that the most economically feasible investment was possible by founding a community solar which offsets the members’ consumed electricity. Such an investment would feature a 10 year payback time and an internal rate of return of 8.3 %. Finally, the potential of the solar landfill concept on a regional level was identified as significant. In a scenario where the PV system suggested for Visby landfill in the feasibility assessment is installed on all the suitable landfill sites on Gotland, the island has the possibility to produce 22 GWh of electricity from solar landfills, thereby meeting the regional energy goal set for 2020.

The shortage of electricity in Nigeria creates a huge gap between demand and supply, making individuals and organizations look for alternatives to obtain regular supply of power. The objective of this study was divided into two parts. First identify the barriers and drivers of the adoption of solar PV systems among home owners and organisations in Rivers State Nigeria. Second, identify the challenges faced by the suppliers of this product for small and large scale suppliers. In order to achieve the objectives of this study, a qualitative research approach was used to carry out the study. A loosely-structured interview and a well-structured interview were used as the method. Findings from this study suggest that the need for a regular power supply was enough to motivate residential adopters to purchase and install solar PVC's and sustainability was a sufficient driver to encourage adoption among organizations interviewed in this study. On the other hand, inadequate policies to encourage subsidies, high cost, difficulty to access finances, high interest rates 20%-22% and short period of payback (3years) for loans involving renewable technology were identified as barriers among residential adopters. Lack of implementation of policies for example, double standard shown by custom officials at ports against the zero tax on importation of renewable energy products set by the government, low level of awareness among the public and lack of organized co-oprative group which provides advisory information to potential adopters were among the barriers identified within this study from interviews conducted with suppliers of solar PV systems.

An expert system has been constructed for the purpose of assisting in the design and analysis of direct gain passive solar environments. This system has been constructed for the use of senior undergraduate architecture students in a computer-based design studio. The primary use of the system is in the role of an educational tool which generates design recommendations from user input and predicts some physical characteristics of the environment.The system is applicable to passive solar environments with vertical, south-facing glazing. The system incorporates three models. The first model represents an attached sunspace with no thermal mass storage. The second model represents a direct gain living space. The third model represents a direct gain living space integrated with thermal mass storage. The third model allows the use of floors, ceilings, and walls as mass for thermal storage. Four representative mass materials (concrete, adobe, common brick, and dense concrete masonry) have been included for comparison purposes. Four representative sub-climates are also incorporated into the system: cold / arid, hot / arid, hot / humid, and cool / humid. For educational purposes, the system makes separate calculations for identical structures based on models for inhabited and uninhabited cases.The system incorporates scientific and mathematical relationships as well as rulesof thumb which have demonstrated their applicability to passive solar design. The system performs calculations based on work by Balcomb, et al. [5, 9], and Duffle and Beckman [1], to estimate environmental temperature swings, total solar energy input, and thermal absorption by mass storage elements. The system also utilizes models based upon work by Mazria [4] to recommend glazing areas. Recommended glazing areas are calculated from user input variables such as structure type, site latitude, and floor area.The system's ease of use allows it to be adapted for various classroom goals, and its generalized nature permits the instructor to adapt it easily into different areas of architectural design curricula. The system is written for use with the CLIPS expert system shell. / Department of Physics and Astronomy

Solar energy constitutes one of the main alternatives for facing the energy problems of the future, taking into account the foreseeable depletion of the fossil fuels. Transpired solar air collectors are relatively simple alternatives, which do not need a continuous supervision and are mostly maintenance free. Their life cycle is relatively high, around 25 years, and the total investment can be fully recovered in the short-term. The aim of this master’s thesis is to analyze the feasibility of installing transpired solar air collectors as secondary systems in big industrial buildings, for heating purposes. The collectors would be designed for compensating the heat losses of a building which is mainly heated up by a heat pump system. Precisely, this work tries to evaluate the profitability of installing these collectors in Gävle, taking into account the particularities of this location in the considered study. This project work is focused on testing if these systems can provide enough thermal energy for heating up big-sized industrial buildings. For this purpose, firstly, the heat demand of the building for each month was calculated; secondly, the maximum output from the collector was estimated, using WINSUN simulator; and, finally, the energy difference that had to be covered by the main system was calculated. Once this was done, the yearly running cost for the main system and the total investment for the transpired air solar collector were estimated. Due to the lack of experimental data, the obtained results can only be taken as approximations. All the calculations and estimations have been made using WINSUN, a simulator that has been configured according to the particularities of the project. The results show that the solar collector provides a total thermal output of 29.700 kWh/year (system which has a total investment of 77.000 SEK). The total heat demand of the building is estimated to be of 87.100 kWh/year, being 51.800 kWh/year fulfilled by the heat pump system (which has a yearly running cost of 24.000 SEK/year). The collector has an average efficiency of 51,04%.

A study has been undertaken of the detailed photoelectrochemistry of a number of III-V and oxide semiconductors. In particular, the work has been aimed at obtaining a material which can act as a stable and efficient photoelectrode for the solar photoelectrolysis of water. However to achieve this aim, it was considered essential to obtain a far deeper understanding of the mechanisms of the electrochemical reactions taking place at the semiconductor/electrolyte interface. The mechanism for Hydrogen evolution from the surfaces of the p-type III-V materials has represented a particular problem. P-type GaP was chosen as the representative member of the III-V materials and a mechanistic study has been made of the material using a.c. and d.c. experiments in addition to a detailed interfacial impedance analysis. A model for the Hydrogen evolution reaction has been proposed invoking surface bound Hydrogen atoms as both intermediates in the desired reaction and also as photogenerated surface states in parasitic recombination reactions. With the experience of the work on p-GaP, the analagous mechanisms to those found on p-GaP have been found to be consistent with results obtained on p-GaAs, p-InP and p-GaSb. However for these latter materials, additional complexities have arisen from their greater instability with respect to cathodic corrosion. A method has been sought for modifying the surface of the III-V materials in order to obtain improved Hydrogen evolution efficiencies. Such a modification has been discovered for p-GaP by the adsorption of a Ruthenium species from solutions of crude RuC1₃.xH₂0. Its mode of operation is discussed at length. For the oxide materials, a semiconducting oxide has been sought that possesses the ideal band energies and bandgap to obtain optimum photoefficiencies for the photoelectrclysis of water. The design constraints for such a material are presented and some results on a number of novel oxide semiconductors are discussed in relation to their use in such photoelectrolysis cells.

The limited underground water resources and the dramatic increase of fresh water consumption in Qatar forced the government to seek alternative ways to compensate for the lack of fresh water resources. Unfortunately, most of the currently available alternatives are costly in terms of excessive fuel consumption; also they require large capital investment and high maintenance cost. Such plants currently produce over 98% of the total fresh water in Qatar. This ratio may increase to 100% in the next few years. The main aim of this work is to investigate the most viable water desalination processes, which can produce sufficient, and a continuous supply of fresh water with low operation and construction costs. Climatic conditions and solar radiation in Qatar have been studied and analysed to determine the performance of any potential solar system applicable to this country. A technical and economical investigation into the current and common desalination methods with particular emphasis on the three main desalination systems including multistage flash, multiple effect distillation and reverse osmosis were conducted and included. A comprehensive literature survey on various water desalination methods was undertaken. The current experimental program was confined mainly to one novel type of tilted tray solar still system, namely pyramid tilted tray solar still, which was developed to increase productivity by increasing the receiving surface area of the still (the absorber) in order to collect the optimum amount of solar radiation. Two types of cover have also been selected and tested in this work, namely pyramid and dome shapes. These tilted tray solar stills were designed and constructed on a small scale and have been tested under controlled laboratory conditions at the University of Hertfordshire. Various parameters, which are likely to effect the still performance have been investigated. These include water flow rate, spacing between cover and tray surface, glass thickness, insulation layer, and inlet water temperature. Finally, a comparison of the stills performance characteristics of the two shapes has been carried out. The laboratory experimental results of hourly production revealed that pyramid type solar still yield higher distilled water output results than the dome type. However, the use of the pyramid shape with tilted tray solar can lead to further increase in the still productivity by optimising the orientation and surface area of the still absorber. The field experimental results of pyramid solar still, which were conducted under local climate conditions of Qatar, indicated clearly that solar desalination can be a suitable economical option, particularly for remote areas, where the fresh water demand is low and water transport is expensive. Moreover, a theoretical model was employed to predict the effects on solar still performance under three various parameters under typical climatic conditions of Qatar; These include the thermal insulation layer, the water depth and wind speed. Due to the economical reasons the dual-purpose multistage flash process will remain for the foreseeable future the preferred process, when fresh water and electricity demands are growing concurrently and rapidly.