In a time of a fast growing renewable electricity generation sector, there are challenges regarding the integration of such generation with current transmission infrastructure. Such challenges include problems associated with the intermittent power output of renewable energy sources and the inability to control there output to meet varying electrical demand. Using part of this available energy for the provision of domestic heating loads may help bridge the gap between supply and demand. The use of intermittent electrical energy sources for charging water based thermal energy stores was identified as a research gap. This research project studies the use of intermittent electrical supplies from wind turbines for the provision of space heating and hot water in domestic buildings. It also addresses how solar water heating may be incorporated into the same thermal energy storage unit to create a hybrid system. This thesis outlines and analyses two charge strategies that may be used to promote stratification in water based thermal energy stores when adding intermittent electrical energy. The first makes use of multiple heating elements switched on in sequence (direct system) while the second uses buoyancy forces to take cool water from the bottom of the tank, pass it through the heating element and then place it back in at the top of the tank at a higher temperature (side-arm). The research method includes; 1) a simplified theoretical simulation of direct and side-arm configurations in the transient system simulation software (TRNSYS) to identify system performance when charged from wind and solar energy; 2) a detailed theoretical representation of the side-arm charge mechanism with a modulating valve for TRNSYS; 3) an empirical validation of the detailed theoretical model of the side-arm charge cycle. Outcomes from the simplified theoretical model indicate that the side-arm configuration may have benefits over the direct configuration due to reduced heat loss from the tank, reduced auxiliary energy consumption and increased solar collector performance. The detailed theoretical representation of the side-arm was calibrated using the empirical data gathered. From this, important parameters affecting the performance of the side-arm charge cycle are evaluated. These include the effects of tank height, operating temperature and the power range from the intermittent electrical supply. It is identified that the assumptions made in the simple model are not possible to reproduce in real life and that an analysis using the complex model must be made in order to evaluate any potential benefits of the side-arm over a direct configuration.

This thesis investigates the role of support schemes to promote investment in renewable energy in the Nigerian power sector. The current situation does not favour investment in renewable energy. The argument developed by this thesis shows that the feed-in tariff (FIT) scheme is most suitable for encouraging investment in renewable energy in Nigeria. Drawing from legal analysis of international best practice and established FIT schemes in Germany and China, the research puts forward assertions that the FIT, with a design structure containing a fixed tariff for a guaranteed duration, tariff differentiation and degression, purchase obligation, guaranteed priority and guaranteed access to the grid, review measures and effective administration and implementation can encourage investment in renewable electricity in Nigeria. The thesis goes on to discuss how typical models of the FIT schemes used in the developed world need to be adapted to meet the existing challenges in the Nigerian electricity market if the FIT scheme is to be effective. The principal challenge is that consumers are unable to bear the cost of subsidies to investment in renewable energy. There are the concerns that purchasers of renewable electricity are not creditworthy. There are also general rule of law challenges which may lead to regulatory uncertainties and changes in support offered to investors. These require departures in design from the typical FIT models including those employed by Germany and China. The thesis proposes solutions to the particular difficulties in using an FIT scheme in Nigeria and concludes by providing a legal framework that includes suggested responses. It proposes that the FIT should be financed by the Nigerian state, by establishing a fund from the oil revenue account under the constitution. The risks of non-payment by the purchasers should be removed by establishing government guarantees backed by international financial institutions. Measures such as saving provisions in the law, stabilisation clauses in investment contracts and reliance on the provisions of bilateral investment treaties are important mechanisms that are proposed to check regulatory and investment uncertainties. The thesis presents a proposal for a legal framework for promoting renewable energy in the Nigerian power sector that incorporates these solutions.

The concentration photovoltaics (CPV) application promises to produce lower price electricity with less semiconductor usage in comparison with the common flat plate PV module. The compound parabolic concentrator (CPC) shows great potential in both economics and efficiency in low the concentration photovoltaics (LCPV) system because it does not require a tracking system and is able to concentrate light with a large incident angle range. A detailed investigation has previously been carried out regarding the novel CPC module purposed (Su et al., 2012a). The validation of the experiment shows the Lens-Walled CPC gives a superior optical and electrical performance compared with other CPCs. Non-uniform light distribution is a common issue with all CPC designs as it has a major influence on the concentration of solar cell performance. In order to study the effects of non-uniform distributed light on solar cell behavior in-depth, two simulation approaching methods including array modelling and finite element modelling (FEM) were carried out. Both simulation approaches observed a reduction in the solar cell fill factor (FF) under non-uniform distributed light. The high resistive losses in the cell are the main cause of this phenomenon. Three simulation models with different cell grid designs were studied to further study the influence of non-uniform distributed light. The light profiles from three different CPCs were implemented with the FEM model. The result shows although solid CPC has the highest current output in a certain condition, the Lens-Walled CPC has the most uniform light distribution, which reduces the influence from non-uniform light distribution to solar cell performance.

It is undeniable that activities and events within the water, energy, and food (WEF) security nexus are inextricably linked and their relationships numerous and substantial. Complexity increases when factors governing the daily lives of humanity namely social, technology advancement, environment, economic, and policies (STEEP) adds upon the difficulty in addressing the relationships. It is thus paramount to address the problems from a holistic and systematic approach to maximise benefits as well as to minimize the negative impacts upon one another. However, there exists little to zero means of measuring their performance, whether qualitatively or quantitatively, within the context of a nexus. Moreover, minimal understanding exists regarding the relationships between the WEF securities in Malaysia, an emerging economy rich in natural resources, which envisions to be a developed nation. This research sought to establish a measurement system for the WEF security nexus in Malaysia within the context of resource security wellbeing, sectoral balance, and sustainable development using a System Dynamics (SD) approach. This entailed an extensive literature review and qualitative interview with key stakeholders from the industrial sectors. The front end of the SD process is concerned with obtaining important and relevant information from literature and interviews, which are then used to construct causal loop diagrams (CLD). The back end of the SD is concerned with converting the CLDs into a stock and flow diagram (SFD), which provides a platform for quantitative simulation of different well-designed scenarios. Key findings from this research can be highlighted; these include: renewables are necessary for the long-term energy plan of Malaysia, nuclear power is necessary to keep electricity tariff low, water tariff of supply and services are severely low, increasing self-sufficiency level (SSL) of Malaysia’s staple food is important, under-utilised crops are efficient in meeting nutrient requirements, and cash crops imposed systemic stresses upon the water sector more than the energy sector. Consequently, recommendations for policy makers are suggested accordingly to achieve a reasonable proportion of RE penetration, providing education on nuclear benefits, centralising and streamlining water governance, socio-economic improvement of water economics, increase SSL of staple food, embark upon widespread adoption of local under-utilized crops, and controlling land use of non-food crops. The outcome of this research forms a vital and novel contribution to knowledge, when it is a pioneering work to address the WEF security nexus for Malaysia; especially in considering their securities for the country as a system rather than unaffected individual entities. This work will contribute towards spearheading the awareness and, hopefully, trigger further and more in-depth work in transdisciplinary resource and technology management. As a pioneering effort, this research has nonetheless provided the foundation and the fundamental understanding to an integrative and inclusive cross-sectoral national resource backbone - The WEF security nexus measurement system of Malaysia.

The reliable supply of hydrogen to a vehicle re-fuelling station has been tackled in this thesis. A currently operational system based on supplying energy from a bio-generator, fuelled from biogas generated by organic matter in an Anaerobic Digester, formed the basis of an expanded renewable energy system. The criterion for the new design was the supply of energy to an electrolyser/compressor/storage system at minimum cost and minimum interruption to supply. By separating hydrogen production from energy generation, the operating parameters of the electrolyser and compressor were optimized, leading to an energy load profile that guaranteed a reliable supply of hydrogen sufficient to fuel the daily needs of up to two hydrogen fuelled vehicles. Based on the energy load profile, a renewable energy system was designed around the existing bio-generator. A multi-objective optimization by Genetic Algorithm was employed to design a hybrid renewable energy system that minimized lifetime costs and unmet load. The resulting design consisted of a mixture of wind turbines, batteries, inverters/rectifiers, as well as the bio-generator. A control strategy that directed the interaction of all components was also produced. Multi-objective optimization by Genetic Algorithm was found to be a reliable, efficient method in designing a complex hybrid renewable energy system with non-linear characteristics. The results of modelling and simulation showed that an uninterrupted supply of energy could be produced, based on specific meteorological conditions, at a minimal cost. The research has shown that it is possible to develop a design that produces hydrogen reliably purely from renewable energy sources. The design is flexible enough to integrate other renewable energy sources and technologies as they develop.

Thesis (M.A.Sc.)--Dalhousie University (Canada), 2007. / Includes bibliographical references.

Modern man’s addiction to fossil fuels or non-renewable energy is the key reason behind the unprecedented economic growth experienced globally over the past 100 years. However, by definition these energy resources are not only finite, but their widespread use is causing massive environmental damage through air pollution and its associated impact on people’s health, as well as the emission of greenhouse gases which are attributed to the unprecedented rate of global warming - And it is for this reason that international initiatives such as the Kyoto Protocol, (which South Africa is a signatory of), aim to mitigate global warming by reducing member countries’ CO2 emissions.Simultaneously, South Africa (SA) is experiencing its own electricity supply problems due to under investment in the sector. While new power plants are being built, they utilize non-renewable energy sources and will take time to build (up to 5 years). It is also important to note that due to large coal reserves, South Africans enjoy amongst the lowest electricity tariffs in the world, but SA is amongst this planet’s biggest per capita polluters.The research thus aims to identify whether high income households are wasteful users of electricity - due to historic low prices, lack of knowledge regarding energy efficiency and the impact that electricity generation has on the environment - while at the same time determining the group's perception of domestic solar water heaters (DSWH), given our country’s favourable climaticconditions. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

In the present work, an inter principle research is carried out on complex fluid flow and heat transfer, using an innovative technology Nuclear Magnetic Resonance (NMR), from the Department of Physics. To enhance heat transfer performance of complex fluid flow, the present work mainly focuses on two different parts, one is the adoption of nanofluid; the other is flow forces analysis through bionic engineering studies on plant water migration system. Nanofluids are attracting considerable attention from both academic and industrial communities. Comparing with conventional pure fluids or solutions, nanofluids have higher thermal conductivity, due to the high surface to volume ratio of nanoparticle and liquid interface, which exhibits a great potential in enhancing heat transfer performance in various occasions. It is believed that different types and concentrations of nanofluid could strongly affect the thermal performance, and a great number of papers have been published to illustrate the phenomenon. However, none has really focused on the possible concentration change of nanofluid while flowing. Otherwise, the thermal performance of nanofluid flow could never be quantified. In the present work, a novel method to measure the dynamic concentration of nanofluid is proposed, using NMR technology. The experiments were carried out with ferrofluid under different concentration and temperature. A new parameter T2* was introduced in the study. T2* is a relaxation time of the signals that is released by hydrogen atoms after Radio Frequency (RF). And this signal intensity can be strongly affected by nanofluids. Experiments were carried out to obtain the T2* of nanofluid in the pipe. An empirical equation based on T2* and temperature was proposed to calculate the concentration of nanoparticles. Then, experiments were carried out with flowing ferrofluid in pipe. The dynamic concentration was calculated with the empirical equation. And with the series of experiment, it is confirmed that the flowing nanofluid consists of an obvious concentration gradient, and thus cause different layers of thermal performance from boundary to central line of a laminar pipe flow. Furthermore, the experiment result also gives out a chance to investigate the mechanism of nanoparticle movement in laminar flow with the concentration gradient along radius. Bionic Engineering is another research field that has been more and more interesting to researches from various fields. Since life has been evolving for over millions of years, many functions in lives has become extremely high efficiency and adaptive. These functions can be very worthy for researchers to study and utilize in industries. For heat transfer in fluid flow, it is very important to enhance the flow pattern. And thus water migration system in plants become very attractive. Plant can take water from soil up to several metres high. Learning from the water migration process in plants has been attracting interests from scientist for over a hundred years. The water migration in plant stem, especially xylem, involves various driving forces including capillary effect, osmosis effect, Marangoni effect and transpiration effect, etc. This present work mainly focuses on the water transport process within xylem. As xylem system is simplified as micro channel, a mathematic model is presented based on micro channel theory, with critical analysis and simplification. With a simplified micro channel from xylem structure and the calculation using the model of water migration in xylem, the relationship between various forces and water migration velocity is identified. The velocity of water migration within the plant stem is considered as detail as possible using all major forces involved. And a full mathematical model is proposed to calculate and predict the velocity of water migration in plants. Comparison between the calculated result and experimental one is made, to confirm the accuracy of the mathematical model. The present work proved that the mathematical model should be enough to predict the water migration in plants, and could also be critical for future water transport prediction in complex fluid flow in industry applications such as heat pipe.

Efficient bale stack location, infield bale logistics, and equipment track impacted area were conducted in three different studies using simulation in R. Even though the geometric median produced the best logistics, among the five mathematical grouping methods, the field middle was recommended as it was comparable and easily accessible in the field. Curvilinear method developed (8-259 ha), incorporating equipment turning (tractor: 1 and 2 bales/trip, automatic bale picker (ABP): 8-23 bales/trip, harvester, and baler), evaluated the aggregation distance, impacted area, and operation time. The harvester generated the most, followed by the baler, and the ABP the least impacted area and operation time. The ABP was considered as the most effective bale aggregation equipment compared to the tractor. Simple specific and generalized prediction models, developed for aggregation logistics, impacted area, and operation time, have performed well (0.88?R2?0.99). An ABP of 8 bales capacity, also capable of 11 bales/trip, was recommended. / North Dakota State University. Teaching Assistant Scholarship

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