This thesis first presents a new cooperative wireless communication network strategy that incorporates energy cooperation and data cooperation. The model establishment, design goal formulations, and algorithms for throughput maximization of the proposed protocol are presented and illustrated using a three-node network with two energy harvesting (EH) user nodes and a destination node. Transmission models are established from the performance analysis for a total of four scenarios. Based on the models, we seek to find optimal energy management strategies by jointly optimizing time allocation for each user, power allocations over these time intervals, and data throughputs at user nodes so as to maximize the sum-throughput or, alternatively, the minimum throughput of the two users in all scenarios. An accelerated Newton barrier algorithm and an alternative algorithm based on local quadratic approximation of the transmission models are developed to solve the aforementioned optimization problems. Then the thesis extends the cooperative strategy to multi-source wireless communication network, where N source users communicate with the destination via one relay that harvests energy from the RF signals transmitted by the sources through time-division multiple access (TDMA). We characterize the Energy-Throughput (E-T) tradeoff regions between the maximum achievable average throughput of the sources and the total amount of saved energy in three circumstances. For the case N=1, all harvested energy will be used to forward the message. For the case N>1, we compare two transmission strategies: one is common PS ratio strategy that the relay adopts the same PS ratio for all sources; the other is individual PS ratio strategy that each source uses an individual PS ratio. Numerical experiments under practical settings provide supportive evidences to our performance analysis. / Graduate

In this work the development of a Self-Powered System-On-Chip is explored by examining two components of process development in different perspectives. On one side, an energy component is approached from a biochemical standpoint where a Microbial Fuel Cell (MFC) is built with standard microfabrication techniques, displaying a novel electrode based on Carbon Nanotubes (CNTs). The fabrication process involves the formation of a micrometric chamber that hosts an enhanced CNT-based anode. Preliminary results are promising, showing a high current density (113.6mA/m2) compared with other similar cells. Nevertheless many improvements can be done to the main design and further characterization of the anode will give a more complete understanding and bring the device closer to a practical implementation. On a second point of view, nano-patterning through silicon nitride spacer width control is developed, aimed at producing alternative sub-100nm device fabrication with the potential of further scaling thanks to nanowire based structures. These nanostructures are formed from a nano-pattern template, by using a bottom-up fabrication scheme. Uniformity and scalability of the process are demonstrated and its potential described. An estimated area of 0.120μm2 for a 6T-SRAM (Static Random Access Memory) bitcell (6 devices) can be achieved. In summary, by using a novel sustainable energy component and scalable nano-patterning for logic and computing module, this work has successfully collected the essential base knowledge and joined two different elements that synergistically will contribute for the future implementation of a Self-Powered System-on-Chip.

This diploma thesis concerns the design proposal for a bicycle gearbox powered by human force. The first part summarizes the existing solutions. The second part includes the proposal of the new design, together with the calculation of the strength for selected parts. Attached are the drawings documenting the findings.

This diploma thesis deals with vehicles that are driven by human power, namely the design of a bicycle frame intended for city traffic. Part of the work is a section that describes the historical development of cycling bikes, as well as an overview of individual bicycle conceptions, focusing on their advantages and disadvantages

-Design of a conceptual bus using results to determine current trends in public transport. -Integration of electronic mirrors to increase safety, use of clean electrical components without emissions, use of lidar sensor built into the lights, air purification -Electric bus design in terms of design, production technology and ergonomics, production of a physical model and posters. -Work brings insight into current trends in public transport, and offers solutions for integration into design.

This master thesis deals with the design of beehive security system against unauthorized manipulation. The system uses LoRaWAN wireless communication technology for data transmission. The device records the movement of the beehive using an accelerometer and then locates the beehive using a GPS module. The low-energy system works via a battery-powered ESP32 microcontroller and is located on a beehive. The battery is charged using a solar panel. The system can be modularly expanded with additional sensors to monitor the condition of the bees. The device has been tested in practice, where it has been confirmed that it meets the required properties for securing beehives.

This project examines the initial system analysis and system level design for an integrated elect cal system to be used in a solar powered car. The system design includes the ability to collect and store solar power, as well as manage control signals. The electrical motor for the purposes of this report is considered as part of the mechanical system of the car. The report follows the rigorous systems approach format for as adapted from Blanchard and Fabrycky's Systems Engineering and Analysis 1990). The report begins with a statement of the problem, and continues through preliminary design. / Master of Science

With increasing popularity of indoor farming, more and more home growers are faced with sub-optimal lighting conditions in northern countries or poorly lit windows. We have designed and built a proof-of-concept system capable of reducing electricity cost and CO2 footprint of the electricity used for consumer grade grow lights without adversely impacting the grow cycle of the plant. Our system provides optimal grow light conditions for a given plant while using forecasts and live grid data from the ENTSO-E transparency platform to automatically use or store electricity during low-cost hours and avoid using grid electricity during high-cost hours, but can also be configured to prioritize electricity use when the available grid power’s carbon intensity is low. The system, consisting of a server and an embedded control unit, was designed and implemented according to Nunamaker and Chen’s five-step iterative systems development research method and later evaluated by simulating the system for 14 days using real world sunlight and grid data. The results of the simulation show a significant reduction in both spending and carbon emissions related to electricity use, with figures of 73% and 28%, respectively. However, when accounting for life-cycle cost and emissions from the battery, the prototype in its current configuration is neither profitable nor a net positive for the environment. With changes to battery type and taking advantage of economies of scale, a future version could be economically viable, but to be environmentally sustainable, further advances in eco-friendly battery production are needed.

Global growing demand for agricultural production has put increased pressure on freshwater resources in various global locations. Many areas have saline groundwater resources which have not been utilized for agriculture due to the economics associated with water pumping and desalination. Limited availability to electricity and high operational costs of diesel generators are major obstacles to utilization of these resources. Reduced costs associated with large-scale renewable energy have renewed interest in understanding the potential impacts of developing distributed photovoltaic (PV) powered water pumping and desalination systems for agriculture. In order to determine the economic feasibility of solar-powered water pumping and desalination for agriculture, an engineering system model that performs hourly simulations of direct-coupled PV pumping and desalination systems by integrating environmental resource data and industrial component performance data was developed. Optimization algorithms were created to identify the best membrane type, control method and reverse osmosis system configuration for a given set of locational parameters. Economic analysis shows that PV-powered systems are more economical than diesel-powered systems for water pumping, with water desalination costs for PV- and diesel-powered systems being comparable. Grid-powered systems are able to pump and desalinate water for a lower cost than PV or diesel for all cases evaluated. A sensitivity analysis is performed to generalize results for different input parameters and illustrate the impact of input variables on water unit costs. Several case studies in the Jordan Valley were evaluated to illustrate the economic viability of solar-based systems with simulation results including a direct comparison to diesel- and grid-connected alternatives. Results indicate that under fair environmental conditions and irrigating greenhouse vegetables, the PV-, diesel-, and grid-powered systems produce favorable internal rates of return of 40%, 84%, and 248%, respectively. Under poor environmental conditions and less profitable crops the PV-, diesel-, and grid-powered systems all result in negative internal rates of return, illustrating the need for optimal location and crop selection for system implementation.

Engagement is the active involvement in experiences which allows for development. For children with severe mobility impairments however, challenges arise in accessing experience which can lead to learned helplessness. Due to these challenges powered mobility has been suggested as a mechanism for the provision of self-initiated access to experiences. However, powered mobility is out of reach of the majority of children with disabilities in South Africa hence a non-powered alternative has been sought. This study sought to determine the effect of non-powered, self-initiated mobility on the engagement of young children, with severe mobility impairment, in play. A multiple probe design across participants was used. Four participants, aged 2 years 10 months to 6 years 9 months with severe mobility impairment (Gross Motor Function Classification Scale (GMFCS) level V) underwent a minimum of 5 baseline sessions, followed by 8 intervention sessions. Engagement was measured during each session using the Individual Child Engagement Record –Revised (ICER-R). The data was analysed using visual graphic and statistical analysis. All participants demonstrated an improvement in engagement in play with the introduction of non-powered, self-initiated mobility. A reciprocal deterioration in non-engagement was also recorded. A decrease in engagement in play at the start of intervention was attributed to the focus of engagement being on mobility skills as the device was introduced but this reverted as the participants spent more time on the mobility device. Functional abilities were identified as having a greater role in engagement than age. The introduction of non-powered, self-initiated mobility correlated with the improvement of engagement of young children with severe motor impairment. Non-powered, self-initiated mobility is a viable, cost effective mechanism for mobility at a young age. / Thesis (PhD)--University of Pretoria, 2015. / Centre for Augmentative and Alternative Communication (CAAC) / PhD / Unrestricted