Research Papers and Publications

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Browsing Research Papers and Publications by Author "Abraham, C.J."

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    Ray of Hope for Sub-Saharan Africa’s Paratransit: Solar Charging of Urban Electric Minibus Taxis in South Africa
    (Energy for Sustainable Development, 2021) Ndibatya, Innocent; Booysen, M.J.; Abraham, C.J.
    Minibus taxi public transport is a seemingly chaotic phenomenon in the developing cities of the Global South with unique mobility and operational characteristics. Eventually this ubiquitous fleet of minibus taxis is expected to transition to electric vehicles, which will result in an additional energy burden on Africa's already fragile electrical grids. This paper examines the electrical energy demands of this possible evolution, and presents a generic simulation environment to assess the grid impact and charging opportunities. We used GPS tracking and spatiotemporal data to assess the energy requirements of nine electric minibus taxis as well as the informal and formal stops at which the taxis can recharge. Given the region's abundant sunshine, we modelled a grid-connected solar photovoltaic charging system to determine how effectively PV may be used to offset the additional burden on the electrical grid. The mean energy demand of the taxis was 213kWh/d, resulting in an average efficiency of 0.93kWh/km. The stopping time across taxis, a proxy for charging opportunity, ranged from 7.7 h/d to 10.6 h/d. The energy supplied per surface area of PV to offset the charging load of a taxi while stopping, ranged from 0.38 to 0.90kWh/m2 per day. Our simulator, which is publicly available, and the results will allow traffic planners and grid operators to assess and plan for looming electric vehicle roll-outs.
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    Walking on Sunshine: Pairing Electric Vehicles With Solar Energy for Sustainable Informal Public Transport in Uganda
    (Energy Research and Social Science, 2021-11) Ndibatya, Innocent; Booysen, M.J.; Abraham, C.J.; Rix, A.J.
    Minibus taxi public transport is a seemingly chaotic phenomenon in the developing cities of the Global South with unique mobility and operational characteristics. Eventually this wide-spread effect of minibus taxis will have to transition to electric vehicles. This paper examines the impact of this inevitable evolution on a city-wide scale in Kampala, Uganda. We present a generic simulation environment to assess the grid impact and charging opportunities, given the unique paratransit mobility patterns. We used floating car data to assess the energy requirements of electric minibus taxis, which will have a knock-on effect on the region's already fragile electrical grid. We used spatio-temporal and solar photovoltaic analyses to assess the informal and formal stops that would be needed for the taxis to recharge from solar PV in the region's abundant sunshine. The results showed that the median energy demand across all simulated days of the effect of taxis was 220kWh=d. This ranged to a maximum of 491kWh=d, with a median charging potential (stationary time) across taxis of 8 h=d to 12 h=d. The median potential for charging from solar PV ranged from 0:24kWh=m2 to 0:52kWh=m2 per day, across the taxis. Our simulator and results will allow traffic planners and grid operators to assess and plan for looming electric vehicle roll-outs to the most-used mode of transport in Africa.