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This thesis is concerned with the design and evaluation of a small scale solarthermoelectric power generation system. The system is intended for electricity generation and thermal energy supply to small scale applications in developing countries of the sunny equatorial regions. Detailed design methodologies and evaluations of both the thermoelectric device and the solar energy collector, which are parts of the combined system, are presented. In addition to experimental evaluations, three theoretical models are presented which allow the design and evaluation of both the thermoelectric module and the solar energy collector. One of the models (a unified thermoelectric device model) concerns the geometrical optimization and performance prediction of a thermoelectric module in power generation mode. The model is unified in the sense that it accounts for the effect of all the parameters that contribute to the performance of the thermoelectric module, a number of which are ignored by the available design models. The unified model is used for a comparative evaluation of five thermoelectric modules. One of these is commercially available and the others are assumed to have optimum geometry but with different design parameters (thermal and electrical contact layer properties). The model has been validated using data from an experimental investigation undertaken to evaluate the commercial thermoelectric module in power generation mode. Results showed that though the commercially available thermoelectric cooling devices can be used for electricity generation, it is appropriate to have modules optimized specifically for power generation, and to improve the contact layers of thermoelement accordingly. Attempts have also been made to produce and evaluate thermoelectric materials using a simple melt-qucnching technique which produces materials with properties similar to those of the more expensive crystalline materials.

Profiled steel cladding can be modified to act as an air heating solar collector by the addition of a transparent cover system. A mathematical model of the thermal performance of such an arrangement has been derived for the situation of a building-integrated solar collector facade, allowing for the condition of differing temperatures at front and rear faces of the collector. By introducing an equivalent ambient temperature, it is possible to quantify the performance of such a collector arrangement in terms of existing parameters as derived in the standard Hottel-Whillier-Bliss analysis. Using a purpose-built solar simulator, a set of standard performance characteristics for the proposed collector geometry is derived; these characteristics are used to confirm the validity of the derived model for use in this application area, i.e. as a building-integ rated system with the standard thickness of back insulation. Those conditions of front/rear temperature difference and rear insulation level for which the standard Hoftel-Whillier-Bliss analysis is no longer valid, are identified. The model has been encoded as a new subroutine within the thermal simulation program TRNSYS in order to investigate the energy performance of a typical profiled metal-clad building in the UK climate with and without the assistance of such a collector system. The effects of orientation of the solarcollector facade, together with collection area, steel-to-cover spacing and fan power requirements were determined. Assessment of capital maintenance, operating costs and energy savings permitted the cost-effectiveness of such a system to be evaluated. Guidance for future designers of such buildingintegrated systems is presented for UK conditions. It is concluded that the use of such a collector system can approach cost-effectiveness in electrically fuelled buildings, and that this is likely to be especially so if the building has a significant requirement for pre-heated fresh air. The system is shown to be not cost-effective at present for gas-fuelled installation in the UK, such as in the case of a retrofit to a typically profiled-clad sports centre, though factors other than that of payback alone may well influence such investment decisions in the future.

The search for alternative energy resources began early in this century after the discovery of crude oil, but in 1973, when crude oil prices dramatically increased, the search for new energy sources intensified. The conservation of oil consumption, mainly in industrial countries has been more strictly applied, due to the limited quantities of fossil fuels, especially crude oil which is expected to be depleted within the next few decades. Moreover, the increasing level of air pollution and its severe consequences on human, animal, and plant life and climate, has forced the world to try to reduce air pollution emissions in the short-run, and to search for more reliable, renewable energy resources. Amongst renewable energy resources, solar energy has attracted much attention due to its unique characteristics, including its wide availability in huge quantities, particularly at the middle latitudes, its relatively simple harnessing compared with nuclear energy, and most importantly, its clean source which does not discharge any pollution emission. The intensity of solar radiation in Saudi Arabia reaches an average of 290 wm-2, one of the highest insolation values in the world. Here attention has been focused on solar energy as the main alternative sources of power. However, there is a great variation in the distribution of incoming solar radiation within Saudi Arabia. This variation is attributed mainly to six major factors. They include the following: 1. Sunshine duration 2. Insolation index 3. Altitude of the station 4. Specific humidity 5. Cloud cover, and 6. Dust storms. In order to measure the effect of each factor mentioned above on the variation of incoming solar radiation, a multiple linear regression model is developed and used. This is the most appropriate method to explain the interrelationships between the determinants and their dependent variable. In addition to the physical factors, the human factor is considered in this thesis as a result of the crucial effect of the perspectives and attitudes of people upon solar energy development. Therefore, a questionnaire was conducted at Al-Uyaynah Village, northwest of Riyadh, which has a solar-generated electricity in Saudi Arabia.

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This work describes, (i) the designing and building of two sets of apparatus, namely a Liquid Nitrogen Cooled Ditectional Emissometer and a Laser-source Spectral Bidirectional Reflectometer (ii) measurements using the above apparatus on Solar selective absorber (Maxorb, Cusorb, Skysorb, Solarcoat- 100), non-selective absorber (Nextel, Solarcoat-50) and metal (Al, Cu and brass) samples. The emissometer incorporates liquid nitrogen cooling of the sample chamber thus reducing the error due to emission from the surroundings and extending the working range of sample temperature down to about 273 K. This instrument also uses a beam chopper with a phase sensitive detection system, and a Golay-cell detector. The overall error in the emittance values measured is estimated to be ± 5%. Using the emissometer all the samples in (ii) above were studied. The directional emittance behaviour of the metals and the non-selective absorbers agree well with theoretical predictions and with measurements made by other workers. In the case of the solar selective absorbers however, a peak in the directional emittance at 20°-30° reported by Hutchins (1979) is not seen in any of the present measurements. It is suggested that the ∈/∈'(0°) vs. ∈'(0°) plot can be used in comparing the emittance properties of solar selective absorbers with their substrate metals. The bidirectional reflectometer incorporates a novel device for mounting, positioning and orienting both the sample and the detector (Sample and Detector Assembly - SDA). The relatively small dimensions of this device compared with that of other bidirertional reflectometers reported makes it convenient to use and also allows it to be housed within a light-tight enclosure that minimizes problems with stray light. Extensive measurements have been made using laser sources at λ - 633 nm and λ - 1152 nm on the same set of samples of solar absorbers (selective and non-selective) studied with the emissometer. Comparison of the bidirectional reflectance characteristics of the solar selective absorbers shows marked differences between the materials. However certain features common to 'specularly' reflecting materials and others common to 'diffusely' reflecting materials have been identified. Materials like Cusorb and Solarcoat-lOO show a combination of these. Some of these features are discussed in terms of the surface microstructure data obtained using a scanning electron microscope and a conventional stylus type instrument.

This thesis describes the results of four years work on the design, construction, testing and evaluation of a high performance air heating collector designed to supply heat to a communal interseasonal store, which could heat many houses all the year round in the U.K. Interseasonal storage utilizing a pebble bed was investigated but shown to be costly both in terms of money and energy. The performance of medium to high temperature storage is shown to improve with high performance collectors. The level of insulation specified in the 1978 Building Regulations is found to be inadequate for solar heating with long and short term storage, because it is more economic to add more insulation than to install solar heating. While investigating the interseasonal storage of solar energy in pebble beds, data on the design and operation of air heating solar collectors was found lacking. Therefore the development and testing of both a high and low performance solar air heater was undertaken. The standard methods of testing collectors and in particular high performance collectors are shown not to provide an adequate method of comparing the daily efficiency of various types of collectors. Methods of testing air collectors are presented under transient conditions more representative of collector operation in the U.K. The parameters affecting high performance collectors are examined, in particular the reduction of heat loss between cover and absorber, and the effect on performance of diffuse and transient radiation. Results are also presented for testing a low cost plastic collector.