Uncertainty and Reliability of Comparison of Energetic Scenarios

Background: Comparison of scenarios that involve devices for conversion or production of energy needs energetic criteria. Energy Payback Time is a typical energetic parameter used to compare the performances of systems under specific scenarios. To discriminate between scenarios the difference of parameter values is considered. The significance of the difference makes the confidence on the result and the reliability of a comparison, it depends on the difference and its uncertainty. Objective: This paper shows and discusses how to evaluate the uncertainty of the difference of parameters, defines a target uncertainty to achieve reliable discrimination. A case study on photovoltaic scenarios is used to apply methodology, commercial modules monocrystalline Si, amorphous Si and polycrystalline Si were considered for comparison. Results: Scenarios were compared by their energy payback time. All uncertainty sources were quantified and discussed and energy payback time uncertainty was calculated. Confidence of comparisons was lower than 95% and a target uncertainty was calculated. Conclusion: The use of uncertainty approach gives a much more detailed information on comparison. Confidence is the reliability of the comparison. Uncertainty analysis identify the opportunities to reduce uncertainty and enhance confidence in comparison results