Browsing by Author "Strauss, J. M."

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    Design analysis methods for Stirling engines
    (Energy Research Centre, University of Cape Town, 2008) Snyman, H.; Harms, T. M.; Strauss, J. M.
    Worldwide attempts are being made to increase the use of our renewable energy sources as well as to use our current fossil fuel energy sources more efficiently. Waste heat recovery forms a substantial part of the latter and is the focus of this project. Stirling technology finds application in both the renewable energy sector and in waste heat recovery. Investigating the applicability of Stirling engines in the above-mentioned fields is relevant to develop more efficient external combustion units as well as to utilize our renewable energy sources. Developing a design analysis and synthesis tool capable of optimizing Stirling powered units forms the main objective of this project. The methodology followed to achieve this, involved the application of three different methods of analysis, namely the method of Schmidt, the adiabatic analysis and the simple analysis based on a five volume approach. The Schmidt analysis is used to obtain the internal engine pressure which is a required input for the adiabatic analysis while the simple analysis introduces pumping losses and regenerator inefficiencies. These methodologies are discussed briefly in this paper. Experimental verification of the analytical data was carried out on a Heinrici Stirling engine and both the analytical data and the experimental data are presented here. Shortcomings of these methods of analysis are highlighted and an alternative approach to solve particular shortcomings is presented.
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    Simulating The Driving and Charging of Electric Minibus Taxis: A Case Study for Stellenbosch
    (IWACP, 2023) Pretorius, B. G.; Strauss, J. M.; Booysen, M. J.
    The Global North is increasing the drive for the electrification of the mobility industry. In sub-Saharan Africa, however, the adoption is yet to pick up steam due to various other challenges in the region. The viability of converting the paratransit fleet (which consists mostly of minibus taxis) to electric vehicles (EVs) with current combustion-based operations is investigated by making use of simulation software, and EV-Fleet-Sim. This developed software simulates the driving and charging of operationally tracked taxis in the Stellenbosch area. A charging algorithm, as well as a simple battery model, was included in the simulation to provide a more accurate representation of the scenario. Most of the taxis were found to still complete their required trips with the specified battery size of 70 kWh. However, new methods would need to be found, such as including a mixed fleet with some petrol or diesel taxis, to assure a 100% trip completion rate. The grid impact per vehicle was found with an expected maximum load appearing between the hours of 08h00 and 10h00 of 22 kW per vehicle, which corresponds to the time after the morning peak traffic of getting people to work. Furthermore, a minimum number of chargers can be implemented which will not affect the trip completion rate of the taxis. This was found to be for 4 chargers per 17 taxis. Future work is left to the testing of various parameters to find optimal solutions as well as including home charging and failed trip classification.