James Swart

Optimum Tilt and Orientation Angles for Photovoltaic Panels in the Vaal Triangle

Optimizing the output power of a photovoltaic panel improves the efficiency of a solar driven energy system. The maximum output power of a photovoltaic panel depends on atmospheric conditions, such as (direct solar radiation, air pollution and cloud movements), load profile and the tilt and orientation angles. This paper describes an experimental analysis of maximizing output power of a photovoltaic panel, based on the use of existing equations of tilt and orientation angles derived from mathematical models and simulation packages. Power regulation is achieved by the use of a DC-DC converter, a fixed load resistance and a single photovoltaic panel. A data logger is used to make repeated measurements which ensure reliability of the results. The results of the paper were taken over a four month period from April through July. The photovoltaic panel was set to an orientation angle of 0° with tilt angles of 16°, 26° and 36°. Preliminary results indicate that tilt angles between 26° and 36° provide optimum photovoltaic output power for winter months in SouthAfrica.

Correlating the power conversion of a PV panel to the solar irradiance obtained from Meteonorm

The purpose of this paper is to correlate the power conversion of a photovoltaic (PV) panel to the global solar irradiance obtained from a software package called Meteonorm. Power conversion time is defined as the percentage of time in which a PV panel is converting solar energy into electrical energy and was determined for a nine month period from April through December 2011. Preliminary results, which include regression analysis (R2), conversion-time per week and work-time per day, indicate a favorably comparison between the empirical results and the simulation results.

Theory versus practical in a curriculum for engineering students — A case study

fusing theory and practical in a curriculum for engineering students is a core academic function of a University of Technology. The department of Electronic Engineering at the Vaal University of Technology places particular emphasis on this fusion by means of interactive classroom sessions combined with methodical laboratory work. A previous paper, presented at AFRICON 2007, highlighted several key reasons as to why this fusion must transpire in a curriculum for engineering students. However, comments received from the delegates at that conference highlighted one notable deficiency in the results. The theory before practical approach was only applied to a single experiment on phase lock loops, while the practical before theory approach was solely used with a transmission line experiment. It was therefore suggested that these two approaches be reversed with regard to the relevant practical assignments. The theory before practical approach revealed a much higher average pass rate over the three year study period, proving it to be the preferred method for fusing theory and practical in a curriculum for engineering students. Nevertheless, this study did reveal that a mixed-method approach is still viable for senior engineering students.

Evaluating the effect of orientation angles on the output power of a stationary photovoltaic panel

Economic and environmental concerns over fossil fuels encourage the development of photovoltaic (PV) energy systems. The aim of this paper is to evaluate the effect of orientation angles on the output power of a PV panel, thereby harnessing more of the available solar energy. The practical setup consists of a number of identical PV systems where the PV panels were set to an orientation angle of 0° N, +15° W, and −15° E, with a constant tilt angle of 36°. Tilt and orientation angles play a major role in dictating the output power of a PV panel and subsequently on the power fed into the respective load within the PV system. Preliminary results, which include percentages showing when the system was fully charged and the work-time per day, indicate that a 0° N orientation angle produces the highest amount of output power for a latitude of 26° S.

THE ELECTRICAL PROPERTIES OF CHLORITE TREMOLITE MARBLE MEASURED FOR A RANGE OF RADIO FREQUENCIES

This article attempts to present a simple approach to measuring the electrical properties of rocks over the frequency range from 50 MHz to 950 MHz. These electrical properties, and especially the resonating frequency points, may prove useful in the transfer of radio frequency energy to rock samples for precomminution treatment of run of mine ore. The rock sample that was used consists of calcite, tremolite, and chlorite, with minor opaques and minute inclusions of magnetite in the chlorite. The petrography and geochemistry of the sample are presented. The rock sample was used as the dielectric material in a parallel-plate capacitor. Impedance and phase-angle measurements were obtained using a vector voltmeter, radio frequency generator, power splitter, and coaxial cables and connectors. The resistivity, conductivity, and resonance curves of this sample are graphically portrayed versus frequency.

Mounting DE-Series MOSFETs - a comparison of two recognised techniques

MOSFET devices have developed significantly to become the number one choice for high-power applications in power electronics and electronic communication. Commercially available devices now operate into the VHF range, boasting output powers of up to 300 W. The IXYS RF manufactured IXZ210N50L RF power MOSFET falls into this category of MOSFET devices. It is optimised for linear operation and suitable for broadcast and communication applications. This paper presents two proposed techniques, from the manufactures, for mounting this device with regard to high-power applications. These two techniques (A and B) are contrasted with regard to thermal efficiency, cost and simplicity. The MOSFET drain current is adjusted from 0.5 to 4.5A in both techniques with corresponding heat sink temperatures being measured using the PICO TC-08 temperature logger. The results revealed that technique B has a slightly lower on-state resistance when compared to technique A. However, technique B has a more complex mount and a higher cost. The change in on-state resistance is due to a rise in the junction temperature resulting from the drain current increase.

Determining the electrical properties of granite for the VHF range using a parallel-plate capacitor

The electrical properties of a sample of granite for the VHF range were determined with the use of a new simple method, in which the granite sample acted as a dielectric material in a parallel-plate capacitor. Conductivity, resistivity and resonance graphs are provided for the VHF range. A mathematical equation for the resonance graph is provided.

Fusing theory and practical in a curriculum for engineering students - A case study

Engineering students at the Vaal University of Technology are exposed to both theoretical and practical instruction within their specified disciplines. This provides the students with greater learning opportunities, which is a core academic function of a university of technology. The department of Electronic Engineering comprises one of eight departments within the Faculty of Engineering and Technology that emphasizes the importance of practical instruction for engineering students. This department focuses primarily on finding solutions to industrial problems in the power electronics and telecommunications world. This paper will attempt to highlight the importance of fusing theory and practical in a curriculum for engineering students. Two different approaches exist in this regard, namely presenting the theory before the practical and the practical before the theory. Both approaches were included in a module, Radio Engineering III, which serves as the case study for this paper. It comprises five different theory sections and 10 practical assignments. Most of the engineering students enrolled for this module successfully completed the practical work, which was designed with both approaches in mind. A post-practical survey revealed that the students felt that the practical work done in the laboratory was relevant to the theory work done in the classroom. It also revealed that students enjoyed the practical work, acquiring needed skills relevant to their engineering discipline.

Ensuring sustainability of PV systems for a given climate region in South Africa

A number of software simulation packages for alternative energy systems exist which may be used to determine PV system installation parameters (e.g. tilt and orientation angles) and operating limits (e.g. maximum drain current per day). However, climate change has contributed to a series of variations in weather patterns, resulting in either prolonged rain periods or lengthy heat waves. Both these variable climatic conditions exert a negative influence on the sustainability of PV systems, resulting either in system downtime or system lifetime reduction. This paper aims to contrast the results of a specific software package (RETScreen) for PV systems to experimental results obtained for a given climatic region in South Africa. The results indicate that the RETScreen software packages results should be seen as a guide in the design and installation of sustainable PV systems.