Modeling the Effects of Uncertainty and Reliability on the Cost of Energy from PV Systems

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Ristow, Alan
Begović, Miroslav
Rohatgi, Ajeet
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The cost of energy produced by a photovoltaic system is dependent upon the amount of energy produced by the system and the amortized cost of the system's components. Existing simulation tools either use crude estimators of system reliability or ignore the effects of system downtime on energy production altogether. Furthermore, the costs associated with system components are often not known precisely during system planning. However, it is difficult to reflect this uncertainty in energy cost calculations using conventional deterministic techniques. This work attempts to address these deficiencies by applying a stochastic model of system reliability to the prediction of energy production over a system's life. Similarly, it uses a stochastic model that encompasses the uncertainties associated with system component prices to estimate the uncertainty in the total installed system cost. Finally, using these two results, it computes the uncertainty in the cost of energy produced by the system. Preliminary testing of this approach, using failure data obtained from an actual system, produces cost estimates of $0.300–0.400/kWh, with a mean of $0.349/kWh, consistent with contemporary residential system cost analyses. The link between engineering and economics suggests that the proposed method may be useful as an optimization tool if an appropriate database can be developed from which to draw realistic input distributions.
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