versión On-line ISSN 2413-3051
versión impresa ISSN 1021-447X
J. energy South. Afr. vol.23 no.4 Cape Town 2012
Tawanda HoveI; Henerica TazvingaII
IDepartment of Mechanical Engineering, University of Zimbabwe, Zimbabwe
IIDepartment of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
This paper presents the development and application of a simple spreadsheet-based simulation model for sizing, energy performance evaluation and economic analysis of PV-diesel-battery power supply systems. The model is employed to generate a set of sizing curves that define the design space for hybrid systems using dimensionless generator component size variables, for a specified supply reliability and diesel energy dispatch strategy. The component size combination with the least unit cost of energy is selected among the many possible combinations satisfying a desired loss-of-load probability. Storage battery and diesel generator lifespan, as well as generator fuel efficiency, which depend on the operational loading stress of these components, are recognised as important variables in the economics of the system. The lifespan of the battery is premised to depend on the depth and rate of discharge of the operating cycles, while both the diesel generator lifespan and fuel efficiency are dependent on the degree and frequency of partial loading. The choice of diesel generator dispatch strategy was shown to be another important factor influencing the energy performance and economics of the system. The outputs of the model reveal several important sizing, operational and economic characteristics of the systems, and enables appraisal of comparative advantage of different types of designs and operational strategies. The merits of the hybrid concept are well demonstrated by the study results.
Keywords: PV-diesel hybrid systems, optimal sizing, loss of load fraction, energy cost, dispatch strategy
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Received 17 December 2010
Revised 26 July 2012