In the promotion and development of renewable energy systems, control engineering is one area which can directly affect the overall system performance and economics and thus help to make renewable energies more attractive and popular. For cost effectiveness, ideally the renewable energy industry requires a control design technique which is very effective yet simple with methods that are transparent enough to allow implementation by non-control engineers. The objective of this thesis is to determine if Model Based Predictive Control (MBPC) is a suitable control technique for use by the renewable energy industry. MBPC is chosen as it uses simple and fairly transparent methods yet claims to be powerful and can deal with issues, such as non linearities and controller constraints, which are important in renewable energy systems. MBPC is applied to a solar power parabolic trough system and a variable speed wind turbine to enable the general applicability of MBPC to renewable energy systems to be tested and the possible benefits to the industry to be assessed. Also by applying the MBPC technique to these two strongly contrasting systems much experience is gained about the MBPC technique itself, and its strengths and weaknesses and ease of application are assessed. The investigation into the performance of Model Based Predictive Control and in particular its application in the renewable energy industry leads to two contrasting conclusions. For simple systems with non-demanding dynamics and having a good model of the system, MBPC provides a very good and effective solution. However for more demanding systems with complex dynamics and strong non-linearities, a basic MBPC controller, applied by a non-control engineer, cannot be recommended.

Dissertation (PhD)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.

International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, California / Shrinking budgets and labor pools have impacted our ability to perform experiments at the Nevada Test Site (NTS) as we did previously. Specifically, we could no longer run heavy cables to remote data acquisition sites, so we replaced the cables with RF links that were transparent to the existing system, as well as being low-cost and easy to deploy. This paper details how we implemented the system using mostly commercial off-the-shelf components.

International Telemetering Conference Proceedings / October 25-28, 1993 / Riviera Hotel and Convention Center, Las Vegas, Nevada / A repeater is being designed to provide a telemetry and compressed video link from a remote robot located in the Dry Valleys Region of Antarctica, over a mountain range to California via McMurdo Antarctica. In return a command link is provided for control. A simple task normally, but a bit more difficult when considerations include the unforgiving elements of Antarctica itself. Even with a design using the most robust equipment, tradeoffs must always be made for the effects of the isolation and the weather. This paper describes one approach to the design of equipment capable of insuring the proper bandwidth, power output, and receive sensitivity that can use the energy provided by Mother Nature to continually charge the primary power source, and the engineering struggle to use electronic equipment in the severe and harsh environment of Antarctica.

It is widely known that the element sodium plays a vital role in providing highefficiency CIGS solar cells and that when cells are built on sodium free substrates theyneed an alternative (a substitute) sodium source. In this study a molybdenum-sodiumcompound has been deposited, investigated and evaluated as an alternative backcontact layer containing sodium. The compound had a 5 at % sodium concentrationand it was manufactured by an Austrian company called Plansee. The aim of the studywas to create an equivalent back contact in the sense of sodium delivery, conductivityand adhesion compared to a normal molybdenum back contact on a soda lime glass. The experimental part of the study started with the construction of complete cells,which were fabricated and measured. This work took place at the ÅngströmLaboratory, Uppsala University, Sweden. The characteristics of the layer and the cellswere analyzed by current voltage measurements, quantum efficiency measurementsand secondary ion mass spectrometry analysis. Cell manufacturing involved sputtering,co evaporation and chemical deposition processes. Results show that the molybdenum-sodium compound increases the efficiency of acell built on a sodium-free substrate. Efficiencies reached 8 % for cells without sodiumin the molybdenum and these cells produced 67 % efficiency and 80 % open circuitvoltage of the reference value. Cells with sodium in the back contact layer produced90 % of the efficiency and 95% of the open circuit voltage relative to the references.The best cell with the molybdenum-sodium compound reached an efficiency of 13.3%. This implies that the new back contact layer acts as a sodium source but the cellshave 1-2 % lower efficiency than the reference cells built on soda lime glass. Othercharacteristics of the layer as conductivity and adhesion show no significant differenceto an ordinary molybdenum back contact. Measurements also indicate that the sodium is probably located inside themolybdenum grains and just a small amount is found at the boundaries and in betweenthe grains. Sodium inside the molybdenum grains is difficult to extract and thereforenot enough sodium will diffuse into the CIGS layer. The conclusions drawn from this study are that the molybdenum-sodium compoundhelps to increase the efficiency of a CIGS solar cell built on a sodium-free substrate,but it does not deliver enough sodium to constitute a substitute sodium source.

Predicting the amount of solar radiation that reaches the earth’s surface is critical to understanding the performance of solar power systems, and cloud cover has a particularly strong impact on both the amount and direction of this radiation. Due to its variable nature, solar power is typically thought of as able to provide electricity only as a supplement to traditional power sources. However, by incorporating energy storage into solar facility design, it is possible to mitigate the variations in power production due to changes in sunlight. A key question then is how much energy storage would be required to account for daily solar irradiance variations and allow a solar power facility to produce electricity at least 80% of the year, comparable to traditional coal and natural gas plants. I have developed a simple algorithm for computing the intensity and angular distribution of light transmitted through, and reflected from, clouds. This result allows for accurate determination of variations in irradiance values across the globe. I have also created a model for the energy produced from a 100MW(e) solar power facility coupled to a large-scale thermal energy storage system. I used daily solar irradiance values to determine the array size needed at every location on the planet, and compared the power output at every location when both 1200MWh(e) and 1800MWh(e) of storage were incorporated into the plant design. I then computed the fraction of the year that power was produced at the rated capacity and the amount of time before the facility energy requirements are recouped. My analysis shows that more than 69% of the global land mass has sufficient solar resources provide continuous electricity output more than 80% of the time, and 27% of the land mass can do this more than 90% of time. In these locations the energy payback time ranges from 1.75 to 10 years. / text

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Thesis (Ph.D.)--University of Stellenbosch, 2002. / Bibliography. Also available via the Internet.

Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 119-125).