Feasibility of solar photovoltaic energy as an energy source for the electrowinning of zinc in South Africa

Abstract

Energy consumption for metal extraction and beneficiation is substantial and is expected to keep growing due to increased demand. With rising worldwide energy prices and the continued energy crisis in South Africa, there is a need to decrease the dependence on the national energy grid. Among the refining processes, electrowinning is one of the most energy intensive unit operations. In the context of zinc, electrowinning can consume on average 2,900-3,300 kWh/t-zinc, approximately accounting for 60% of the total electricity consumption of refined zinc production. Industrial and economic growth, a major focus of Southern African countries, is positively correlated with zinc demand due to its role in general construction, electricity transmission, and telecommunications. South Africa is endowed with 14 Mt of zinc content within 200-300 Mt of zinc ore reserves and expanding internal zinc production capacity is a current focus. Since electrowinning units operate with low-voltage direct current, photovoltaic solar energy appears to be an applicable green energy source due to its electricity output also being low-voltage direct current. In addition, South Africa has an attractively high solar irradiance (220 W/m2 compared with Europe's 100 W/m2). Hence, an investigation into the technical and economic feasibility of substituting or supplementing the energy demand, using solar energy for the electrowinning unit of a theoretical zinc refinery operating in the Northern Cape of South Africa, is warranted. A high-level carbon footprint analysis is included. The findings from this study could assist in stabilising the energy supply for the beneficiation of zinc in South Africa, as well as contribute to the decarbonisation of the industry.