Infrastructure Engineering - Research Publications
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ItemNo Preview AvailableEquifinality and process-based modellingKhatami, S ; Peel, M ; Peterson, T ; Western, A (American Geophysical Union, 2018-11-26)Equifinality is understood as one of the fundamental difficulties in the study of open complex systems, including catchment hydrology. A review of the hydrologic literature reveals that the term equifinality has been widely used, but in many cases inconsistently and without coherent recognition of the various facets of equifinality, which can lead to ambiguity but also methodological fallacies. Therefore, in this study we first characterise the term equifinality within the context of hydrological modelling by reviewing the genesis of the concept of equifinality and then presenting a theoretical framework. During past decades, equifinality has mainly been studied as a subset of aleatory (arising due to randomness) uncertainty and for the assessment of model parameter uncertainty. Although the connection between parameter uncertainty and equifinality is undeniable, we argue there is more to equifinality than just aleatory parameter uncertainty. That is, the importance of equifinality and epistemic uncertainty (arising due to lack of knowledge) and their implications is overlooked in our current practice of model evaluation. Equifinality and epistemic uncertainty in studying, modelling, and evaluating hydrologic processes are treated as if they can be simply discussed in (or often reduced to) probabilistic terms (as for aleatory uncertainty). The deficiencies of this approach to conceptual rainfall-runoff modelling are demonstrated for selected Australian catchments by examination of parameter and internal flux distributions and interactions within SIMHYD. On this basis, we present a new approach that expands equifinality concept beyond model parameters to inform epistemic uncertainty. The new approach potentially facilitates the identification and development of more physically plausible models and model evaluation schemes particularly within the multiple working hypotheses framework, and is generalisable to other fields of environmental modelling as well.
ItemGlobal optimisation of chiller sequencing and load balancing using Shuffled Complex EvolutionStewart, I ; Aye, L ; Peterson, T (International Building Performance Simulation Association & AIRAH, 2017-11-15)A new model has been developed to optimise the sequencing and load balancing of chillers in the central plants of commercial buildings with multiple water-cooled chillers. The model uses the Shuffled Complex Evolution optmisation algorithm to minimise the total energy consumptions of chillers and pumps by maximising the whole system (central plant) coefficient of performance under a known discrete cooling load. Two commercial buildings in Melbourne’s CBD were simulated as case studies to assess the validity and effectiveness of the model. The control strategies identified by the model performed better than the existing configuration in both cases, reducing energy consumption by 12.2% and 16.6% when compared to the observed energy data for 2016.