The demand for modern energy services is increasing rapidly. Solar energy has the potential to meet a significant share of the world’s energy request. Solar energy is one of the cleanest renewable forms with little or no effect on the environment. The concentrating solar power is one of the methods to harvest sun’s energy. Concentrating solar power has the advantage of easier energy storage compared to photovoltaic systems. However, the cost of energy generated by those systems is higher than conventional energy sources. It is necessary to improve the performance of concentrating solar power to make them cost competitive. Moreover, few countries such as Saudi Arabia are moving from energy based on fossil fuel to renewable energy, therefore, improving the performance of concentrating solar systems and reducing their cost is considered to emulate photovoltaic systems. This research aims to develop an innovative design of parabolic trough solar collector that uses magnetic nanofluids as a heat transfer fluid to enhance the thermal efficiency compared to conventional parabolic trough. Based on past researches, new parabolic trough design is then proposed and investigated. Ferromagnetic nanoparticles dispersed in common heat transfer fluids (ferrofluids) exhibit better thermos-physical properties compared to the base fluids. By applying the right magnetic intensity and magnetic field direction, the thermal conductivity of the fluid increased higher than typical nanofluids. Moreover, the ferrofluids exhibit excellent optical properties. The external magnetic source is installed to alter the thermo-physical properties of the fluid. This thesis is comprised of four studies including two experimental studies, one heat transfer analysis, and one economic and environmental study. A small scale parabolic trough collector was manufactured and assembled at the laboratory based on the British Standards. A steady-state method was used to measure the performance of the parabolic trough collector in corresponding studies. The performance of the ferrofluids as a heat transfer fluid was compared to the base fluid. The two experimental studies differ in the absorber used. The two absorbers used were a conventional non-direct absorber and a direct absorber without a selective surface that allows ferrofluids to absorb the incoming solar irradiation directly. The effects of nanoparticle concentration, anti-foaming, external magnetic field intensity were investigated. The volume fraction of nanoparticles was 0.05%, 0.25%, and 0.75%. Three different magnetic field intensities were investigated, 3.14 mT, 6.28 mT, and 10.47 mT. Using ferrofluids to enhance the heat transfer performance the efficiency of the ferrofluids solar collector was compared to the based fluid (water). The results show that the parabolic trough solar collector in the experiment has similar performance of flat-plate solar collectors. The efficiency of the collector improved when ferrofluids water used compared to water. Ferrofluids with low concentration improved the performance of the solar collector. The ferrofluids showed much better performance at higher reduced temperature with lower overall heat loss coefficient. Due to the non-Newtonian behaviour of the fluid, increasing the volume fraction of particles will suppress the enhancement. The pH of ferrofluids influences the behaviour of the fluid. pH values higher than 5 showed a Newtonian behaviour of the fluid. In the presence of magnetic field, the performance of the solar collector enhanced further. By increasing the magnetic field intensity, the absorbed energy parameter increased, and at higher magnetic field intensity, the rate of enhancement decreases due to the magnetic saturation of ferrofluids. In this study, the performance of non-direct absorption receiver was better than the direct absorption receiver. However, the performance of the collector with a direct absorption receiver and using ferrofluids in the presence of the external magnetic field in some cases was higher than the performance of non-direct receiver with water as heat transfer medium. The performance of ferrofluids based parabolic trough collector was theoretically investigated. The correlation, equations, and specifications used in the model were discussed in detail. The model was used to study two different parabolic trough designs. First, the parabolic trough was validated with the experimental results of AZTRAK platform. The results of the model show a good agreement with the experimental data. Thereafter, nanoparticles were added to the heat transfer fluid, and the performance of the collector with and without the presence of external magnetic field was determined. The performance of the collector did not change a lot unless the external magnetic field was present. Moreover, the effect of the glass envelope on the performance was observed. A glass cover with vacuum in the annulus has higher performance and less thermal loss. Second, the model was used to study the performance of the test rig ferrofluids based parabolic trough. The performance of the parabolic trough was first considered as concentrating collector and then as a non-concentrating collector. With the lack of an external magnetic field, the efficiency changed slightly, wherein the presence of the external magnetic field the performances of the collector enhanced and showed higher performances. In General, the presence of the magnetic field showed promising enhancement. Economic and environmental effects of using ferrofluids based solar collector compared to a flat-plate collector for household water heating systems. Results show that the ferrofluids based parabolic trough has lower payback period and higher economic saving at its useful life end than a flat-plate solar collector. The ferrofluids based collector has higher embodied energy and pollution offsets tan flat-plate collector. Moreover, if 50% insertion of ferrofluids based parabolic trough for domestic hot water could be achieved in Tabuk over 83,750 metric Ton of CO2 could be eliminated.

This study provides an insight into the fundamentals of PV performance enhancement under different environmental conditions. The study also presents a new concept of PCM integrated PVT system which has a better performance from both electrical and thermal perspectives. The study employs both analytical and computational techniques to investigate the PV performance under the effect of different parameters such as wind speed, solar radiation level, ambient temperature and additional cooling condition. A parametric analysis of the PCM is also carried out under different solar radiation level, water inlet temperature and flow speed. Additional analysis regarding to the effects of PCM’s thermal physical properties against its thermal performance is also presented. A validation analysis is carried out prior to the parametric analysis to ascertain the reliability of the CFD models used, the prediction result of the CFD model is compared with analytical calculations as well as data from literature. The study found that the active water cooling is the best solution which can provide guaranteed performance enhancement regardless effects of ambient conditions. The novel PVT-PCM system is found to have a noticeable electrical performance enhancement over conventional PV panel as well as having the ability to store a significant amount of thermal energy. It is found that the PVT-PCM system has much lower PV cell temperature (maximum temperature reduction of 36.5°C and 38.3°C respectively) compared to conventional PV systems when used in both Nottingham and Shanghai area, hence provide up to 5.4kWh (5.7kWh in Shanghai) more energy per unit module. The stored thermal energy could be utilized to provide moderate heating to air and/or water. The air preheated by PVT-PCM system could satisfy space heating requirement during April to October in Nottingham without any additional energy consumption. On the other hand, the preheated water could reduce boiler heating energy from up to 20% and 41% respectively for Nottingham and Shanghai climate. The overall performance benefits of the proposed PVT-PCM system could be greater if used in hotter climates. Finally, a cost analysis was carried to prove the whole system is financially feasible for use in both climates of Nottingham and Shanghai with a discounted payback period of 10.67 and 12.83 years respectively.

The emergence of decentralized energy resources has brought numerous novel and advanced designs of efficient power generation systems with utilisation of renewable energy for locally provided, sustainable and cost-effective energy production. The micro trigeneration system has been a highly anticipated solution to fulfil domestic energy requirements, allowing simultaneous generation of electricity, heating and cooling from one primary source. As a matter of fact, the micro trigeneration system is still under research and development stage, with limited available demonstrations around the world. Current laboratory experimental and simulation studies mainly focus on integrations of mature technologies, whereas many promising alternatives have not been widely explored, for example organic Rankine cycle (ORC) and liquid desiccant cooling technology. The main aim of this thesis is to technically develop and evaluate a novel micro trigeneration system with a combination of scroll-based ORC and membrane-based liquid desiccant cooling (MLDC). In principle, the micro trigeneration system provides highly efficient energy conversion in a decentralized manner, as the scroll-based ORC has superior abilities in generating electricity and providing sufficient thermal output that matches the low-temperature regeneration requirement of the liquid desiccant in the MLDC. In terms of system sustainability, compact linear Fresnel reflectors (CLFR) can be one option of the primary energy source for the micro trigeneration system. A comprehensive literature review has demonstrated that no work has been conducted previously on such a system. In this thesis, the possibility of integrating CLFR to power generation systems has been firstly investigated and a detailed optical design of the CLFR-hybrid system has been conducted through geometrical modelling and experimental work. Results demonstrate that the CLFR-hybrid system with polar orientation is feasible to efficiently convert the absorbed solar energy into thermal energy, which thereby can be utilised for powering the micro trigeneration system. The concept of the novel micro trigeneration system with scroll-based ORC and MLDC has been critically examined and energy performance of the two main components, namely scroll-based ORC and MLDC have been evaluated respectively through both theoretical modelling and experimental work. Experimental tests show that the scroll-based ORC electric output of 564.5W, scroll expander isentropic and volumetric efficiencies of 78% and 83% are achievable at a 1kW capacity. In terms of MLDC, experimental results indicate the importance of system mass balance between the membrane-based dehumidifier and regenerator for continuous operation. Under the steady operating condition of MLDC, a supply air temperature of 20.4°C with dehumidification effectiveness of 0.3 and system COP of 0.70 are attainable at calcium chloride (CaCl2) solution concentration of 36%. Simulations based on a validated and comprehensive system model demonstrate the feasibility of pairing the scroll-based ORC and MLDC for the microre trigeneration system. The exhaust heat from the scroll-based ORC effectively fulfils the regeneration requirement of the MLDC. The inclusion of MLDC facilitates the micro trigeneration system overall efficiency with an increase of approximately 35.49%, compared to that of ORC-based separate power generation. Theoretical results show that the proposed micro trigeneration system has the overall system efficiencies of 38.96% in cogeneration mode and 41.23% in trigeneration mode. The thesis makes contribution to the knowledge of micro trigeneration technology, distributed power generation, energy conversion and air conditioning. Moreover, the presented parametric studies of CLFR, ORC and MLDC can be employed for designing and optimizing the relevant individual components. Regarding the future work, this thesis recommends more in-depth system modelling with a combination of CLFR, ORC and MLDC, logic optimisation of the micro trigeneration system and comprehensive field trial testing of the micro trigeneration system in building context.

Key factors in using variable renewable energy to sustain crop growth were investigated using the Isle of Lewis as a case study. Methods investigated sought to exploit plants' abilities to accommodate a variable solar input by supplementing it with variable renewable energy. The extant solar resource on Lewis was characterised. The mean ratio of photosynthetically active radiation (PAR) to solar radiation (SR) (fE) recorded in 2010 was 0.458. fE was found to be significantly different between the first and last hour of daylight and 12:00 GMT (F, (2, 33) = 7.98, p<0.001) and between winter and summer months (F, (1, 10) = 20.86, p<0.001). This supports the suggestion that fE decreases as the atmospheric path length decreases. Significantly higher mean fE was also identified for the cloudiest days (F, (1, 22) = 6.22, p<0.05). Supplementing sunlight with intermittent, artificial illumination powered using wind energy significantly increased the growth of Brassica hirta. 53.26% of the additional dry weight produced using fixed diurnal illumination was achieved with 35% of the energy using this technique. The dry weight of B. hirta grown with illumination timed with tidal streams was not significantly different from that grown using fixed diurnal patterns. This is potentially important for the use of renewable energy for horticultural illumination. The possibility of using energy to prioritise lighting in well insulated growing structures and the compatibility of electricity production and horticultural demand on Lewis were considered. These findings support the direct use of variable renewable energy to sustain crop growth and promote the concept of using plants to store renewable energy. This is of potential benefit for problems of renewable energy intermittency, the predicted need to increase world food supply and providing economic opportunities for remote areas with a poor solar resource but good supplies of variable renewable energy.

With the Scottish Government's commitment to sourcing 100% of the national electricity demand from renewable sources by 2020, within the global framework of climate change mitigation, the potential of the marine environment around the Highlands and Islands Region of Scotland to add to Scotland's renewables portfolio has led to the expansion of the wave and tidal industries in recent years. Nevertheless, to date, there has been limited research conducted on the social systems around marine renewable energy development, excluding offshore wind. In answer to this deficit, this study explores a well-established concept within the academic arenas of business, health, and rural development, among others, of agents for change (AFCs), within the context of the rapidly emerging wave energy sector. Two case studies, Lewis in the Outer Hebrides, and Orkney, were chosen based on their localities and the interest that they have garnered from wave energy developers due to their high energy marine environments. A grounded approach was taken to data collection and a social power analysis was conducted in order to find AFCs working within or closely with the wave energy industry that were not part of structured or hierarchical organisations. One emergent theme was that there was a noteworthy barrier to wave energy development in the case studies and to the work that the agents for change were doing in the form of a complex dynamic between financial investments in the sector, national grid, national energy policy, and the technology itself. The agents for change were found to act as catalysts for the wave energy industry through their perseverance and visionary approach to development. The motivations of the AFCs is discussed and the shifting roles that they took as a project progresses is described and compared to other change process models, namely Lewin (1958) and Kotter (1995).

Este trabalho aborda diversas implicações de ordem tecnológica, ambiental e social relacionados ao uso de carvão vegetal nos pólos guseiros. Através de coleta de dados em publicações técnicas, visitas a centros de tecnologia guseira e entrevistas com especialistas da área, foram levantadas as informações que serviram de base à elaboração deste trabalho. A análise e interpretação dos resultados obtidos mostram que a manutenção da produção de ferro-gusa depende do contínuo fornecimento de carvão vegetal, como termo-redutor de boa capacidade calorífica, preço baixo e fácil acesso. Todavia, nas condições atuais, o suprimento de carvão vegetal à indústria está relacionado à exploração intensiva de florestas nativas e uma correspondente falta de áreas reflorestadas capazes de suprir a demanda de lenha para carvoejamento. Além do carvão vegetal, outros insumos também podem ser usados na redução do minério de ferro: o gás natural (na produção integrada de aço) o carvão de coco de babaçu, o carvão vegetal de espécies nativas da Amazônia e mesmo o carvão mineral. Estes insumos, entretanto, apresentam problemas ainda não totalmente quantificados, como suprimento, tecnologia adequada de uso e custos de exploração. O uso intensivo de carvão vegetal se baseia na existência de uma rede de carvoejadores e fornos, que operam num ritmo de trabalho intenso (às vezes cerca de quinze horas por dia), baixa remuneração por madeira carvoejada (meio dólar por metro cúbico de carvão vegetal) e falta de seguridade social. De modo geral, os produtos de gusa pouco consideram o uso de carvão de florestas plantadas, pois admitem que um carvão de maior custo, constituir-se-ia em ameaça à própria continuação da produção de ferro-gusa. / The aim of this work is to discuss implications technological, environmentally and social limitations of the pig-iron´s production using charcoal. Through technical papers, technical visits to research centers and interview with experts, a data basis was collected to produce this work. The analysis of data showed that: the continuity of pig-iron making depends on continuos supply of charcoal, at low cost, with good heat capacity, and with easy acess. However, under current conditions, the charcoal supply to industry is depending of a intensive exploration of native forest. At the same time, there is a lack of land suitablefor reforestation to provide wood to renewable charcoal making. Nevertheless, there are several resources that can be used to reduce the iron ore: charcoal of babassu coconut, charcoal of native amazonic trees, natural gas (integrated plants) and even coal. Some of them are candidates to replace the charcoal, but further technological, infrastructural and economic developments are still required. The intensive utilization of charcoal by siderurgy is based in a network of kilns and charcoal makers working under extreme conditions (indeed, some work fifteen hours per day), they have no social security and extremely low wages (some receive only half a dollar per cubic metre of charcoal). In general, pig-iron´s makers do not consider the use of charcoal from forested wood, because its higher cost may challenge the viability of pig-iron production.

A vinhaça da cana-de-açúcar constitui-se no principal resíduo líquido gerado pelo setor sucro-alcooleiro e, face aos enormes volumes produzidos , os problemas decorrentes de seu armazenamento e disposição o final passaram a constituir nos últimos tempos num grande desafio a técnicos envolvidos com essa questão. Este estudo tem por objetivo apresentar uma alternativa de aproveitamento desse resíduo, Aquelas tradicionalmente conhecidas no meio alcooleiro, por .intermédio do tratamento e transformação da vinhaça em biogás e sua utilização na geração de eletricidade. Para tanto, adotou-se a tecnologia de digestão anaeróbia de alta eficiência através de digestores de fluxo ascendente para a produção de biogás e, uma vez purificado, o aproveitamento desse gás em motores e turbinas adequadas a esse tipo de combustíve1, conforme a literatura consultada. No sentido de avaliar a viabilidade prática deste trabalho, optou-se pela elaboração de um estudo de caso, no qual foi dimensionada uma destilaria hipotética de \'cerca de 150.000 litros de álcool/dia, gerando um volume de cerca de 1.800.000 litros de vinhaça/dia. Por meio desta simulação, foram analisados os aspéctos técnicos e econômicos envolvidos, possibilitando assim, uma apreciação crítica e realista do estudo proposto. / The vinasse of sugar-cane represents the main liquid residue produced by the sugar-alcohol sector and, in view of the enormous volumes produced, the problems related to its storage and final disposal came to pose a great challenge to the technical people involved in this matter these last few years. This study aims to present an alternative for the exploitation of this residue, to these traditionally employed in the alcohol production industry, based on the treatment and transformation of vinasse to biogas, and its subsequent utilization in eletric generation. In this context the technology of high efficiency anaerobic digestion using up-flow anaerobic digestors for biogas production was adapted. Once purified, the biogas produced can be utilized in engines and turbines specially adapted for this fuel, as evinced in the literature consulted. With a view to evaluate the pratical feasibility of this work, the elaboration of a case study was selected, in which a hypothetical distillery with a capacity of about 150.000 litres of alcohol/day, would generate a volume of about 1.800.000 litres of vinasse/day. By means of this simulation, the technical and economic aspects involved were analyzed, thus making possible a critical and realistic appreciation of the study proposed.

In this present world order of growing information, communication and technological advancement, it is primordial that climate change adaptation and mitigation efforts seeks to make people resilient to inevitable climate inconsistency through the exploitation and development of renewable energy sources. Though climate impacts are global, the population most at risk is predominantly from developing countries, particularly poor communities who have experienced multi-layered threats from floods, droughts and energy supply, just to mention a few. This explains why sustainable development is at the heart of all development trajectories in the world today, specifically the post-2015 development tenets. Climate change adaptation and mitigation requires international collaboration from all nations in order to get an effective and unified response to climate change. Building a critical mass for action and an institutional memory to sustain policies and efforts is crucial. A resilient-based approach to climate mitigation and adaptation founded on a crisis-driven reaction to communities vulnerable to climate threat will boost quality of life through the provision and safeguarding of safety nets for the poor. Solar water heaters, a renewable energy source, are here considered as a critical option to South Africa’s coal-driven economy as a means of alleviating energy poverty in rural and low-income communities, to be more precise. Therefore, SWHs have become the epicentre of sustainable development policies and climate change mitigation efforts in South Africa. So far, this device has attracted the attention of local governments in the country who view it as a game changer in the field, particularly towards greenhouse gas emission and energy conservation. The contour of this thesis is to assess the impact of solar water heaters on sustainable development. Although it is generally difficult to assess the real impact of technology on people, that of SWHs was established by asking questions about livelihood before, during and after the introduction of this device.

The growth of the industry and population of South Africa urges to seek new sources of electric power, hence the need to look at alternative power sources. Power output from some renewable energy sources is highly volatile. For instance power output from wind turbines or photovoltaic solar panels fluctuates between zero and the maximum rated power out. To optimize the overall power output a model was designed to determine the best trade-off between production from two or more renewable energy sources putting emphasis on wind and solar. Different measures of risk, such as coefficient of variation (CV) and value at risk (VAR), were used to determine the best hybrid renewable energy system (HRES) configuration. Depending on the investors’ expected returns (demand) and risk averseness, they will be able to use the model to choose the best configuration that suites their needs. In general it was found that investing in a diversified HRES is better than investing in individual power sources.

Recent years have seen a dramatic increase in first generation bio-fuel production, mainly driven by concerns of climate change and rising prices of transportation fossil fuels. Due to significant pressure on the few available food sources, second generation bio-fuels have entered the fray, as a sustainable alternative. This research‟s aim was to search for cellulolytic micro-organisms and enzymes from the gut of the dung beetle, Euoniticellus intermedius, (Coleoptera: Scarabaeida) that can be used in the production of second generation bio-fuels. Dung beetle larvae were dissected and the gut micro-flora cultured in cellulose medium. Bacterial growth and cellulase activity was monitored on a daily basis. DNA isolation was then done on the cellulose medium-cultured microbes and the isolated DNA cloned in E. coli. The clones were screened for cellulase activity using plate assays. A total of 7 colonies out of 160 screened colonies showed positive CMC (endo-β-1,4-glucanase) and MUC (cellobiohydrolase) activities. Sequencing of these positive colonies yielded mostly bacteria belonging to the Enterobacteriaceae family, most of which have not been previously reported to have cellulase activity. This study‟s findings prove that in addition to this dung beetle‟s gut being a fruitful source of microbial biodiversity, it is also a potential source of cellulolytic micro-organisms and enzyme activities that will aid the function and design of future bioreactors for the bio-fuel industry.