Equipment Using a Predictive Health Model

Abstract—In this paper, a model-predictive control based framework is proposed for modeling and optimization of the health state of power system equipment. In the framework, a predictive health model is proposed that predicts the health state of the equipment based on its usage and maintenance actions. Based on the health state, the failure rate of the equipment can be estimated. We propose to use this predictive health model to predict the effects of different maintenance actions. The effects of maintenance actions over a future time window are evaluated by a cost function. The maintenance actions are optimized using this cost function. The proposed framework is applied in the optimization of the loading of transformers based on the thermal degradation of the paper insulation

Falsification of Signal-Based Specifications for Cyber-Physical Systems

In the development of software for modern Cyber-Physical Systems, testing is an integral part that is rightfully given a lot of attention. Testing is done on many different abstraction levels, and especially for large-scale industrial systems, it can be difficult to know when the testing should conclude and the software can be considered correct enough for making its way into production. This thesis proposes new methods for analyzing and generating test cases as a means of being more certain that proper testing has been performed for the system under test. For analysis, the proposed approach includes automatically finding how much a given test suite has executed the physical properties of the simulated system. For test case generation, an up-and-coming approach to find errors in Cyber-Physical Systems is simulation-based falsification. While falsification is suitable also for some large-scale industrial systems, sometimes there is a gap between what has been researched and what problems need to be solved to make the approach tractable in the industry. This thesis attempts to close this gap by applying falsification techniques to real-world models from Volvo Car Corporation, and adapting the falsification procedure where it has shortcomings for certain classes of systems. Specifically, the thesis includes a method for automatically transforming a signal-based specification into a formal specification in temporal logic, as well as a modification to the underlying optimization problem that makes falsification more viable in an industrial setting. The proposed methods have been evaluated for both academic benchmark examples and real-world industrial models. One of the main conclusions is that the proposed additions and changes to analysis and generation of tests can be useful, given that one has enough information about the system under test. It is difficult to provide a general solution that will always work best -- instead, the challenge lies in identifying which properties of the given system should be taken into account when trying to find potential errors in the system

Optimal Control in Three-deck Multi-Zone Air-Handling Units: A Case-Study

A multi-zone air-handling unit was popular several decades ago due to the convenience of small sized modular units, which were inexpensive to install and easily maintained in a mechanical room. The cost and convenience proved to be of little benefit as the units perform poorly from an energy usage perspective. A “three-deck” multi-zone unit is a hybrid of its kind, and it can be very efficient when controlled properly. In theory, there will not be simultaneous heating and cooling if its heating damper is controlled separately from the control of the cooling damper. When the zone load is neutral (not heating or cooling), for example, all the mixed air will be bypassed through the bypass deck. However, there are opportunities and challenges in this system. This paper presents theoretical backgrounds of advantages and challenges in the system operation of the three-deck multi-zone unit and methods to optimize temperature and economizer control to improve energy efficiency. A case-study will be presented examining a medical facility’s utilization of 35 three-deck multi-zone units serving most hospital areas, as well as illustrates a 10% savings in total gas and electric consumptions over the period of one year

Methodologies and advancements in the calibration of building energy models

Buildings do not usually perform during operation as well as predicted during the design stage. Disagreement between simulated and metered energy consumption represents a common issue in building simulation. For this reason, the calibration of building simulation models is of growing interest. Sensitivity and uncertainty analyses play an important role in building model accuracy. They can be used to identify the building model parameters most influent on the energy consumption. Given this, these analyses should be integrated within calibration methodologies and applications for tuning the parameters. This paper aims at providing a picture of the state of the art of calibration methodologies in the domain of building energy performance assessment. First, the most common methodologies for calibration are presented, emphasizing criticalities and gaps that can be faced. In particular the main issues to be addressed, when carrying out calibrated simulation, are discussed. The standard statistical criteria for considering the building models calibrated and for evaluating their goodness-of-fit are also presented. Second, the commonly used techniques for investigating uncertainties in building models are reviewed. Third, a review of the latest main studies in the calibrated simulation domain is presented. Criticalities and recommendations for new studies are finally provided

Performance comparison between KNN and NSGA-II algorithms as calibration approaches for building simulation models

Shadi Basurra , and Ljubomir Jankovic, ‘Performance comparison between KNN and NSGA-II algorithms as calibration approaches for building simulation models’, in BSO 2016 Proceedings. Paper presented at the 3rd IBPSA England Conference, Newcastle, September 2016. Content in the UH Research Archive is made available for personal research, educational, and non-commercial purposes only. Unless otherwise stated, all content is protected by copyright, and in the absence of an open license, permissions for further re-use should be sought from the publisher, the author, or other copyright holder.In this paper, a study of calibration methods for a thermal performance model of a building is presented. Two calibration approaches are evaluated and compared in terms of accuracy and computation speed. These approaches are the 푘 Nearest Neighbour (KNN) algorithm and NSGA-II algorithm. The comparison of these two approaches was based on the simulation model of the Birmingham Zero Carbon House, which has been under continuous monitoring over the past five years. Data from architectural drawings and site measurements were used to build the geometry of the house. All building systems, fabric, lighting and equipment were specified to closely correspond to the actual house. The preliminary results suggest that the predictive performance of simulation models can be calibrated quickly and accurately using the monitored performance data of the real building. Automating such process increases its efficiency and consistency of the results while reducing the time and effort required for calibration. The results show that both NSGA-II and KNN provide similar degree of accuracy in terms of the results closeness to measured data, but whilst the former outperforms the latter in terms of computational speed, the latter outperforms the former in terms of results wide coverage of solutions around the reference point, which is essential for calibration.Final Published versio

Are the Dietary Guidelines for Meat, Fat, Fruit and Vegetable Consumption Appropriate for Environmental Sustainability? A Review of the Literature

This paper reviews the current literature around the environmental impacts of dietary recommendations. The focus of the review is on collating evidence relating to environmental impacts of the dietary advice found in the World Health Organisation guidelines, and environmental impact literature: reducing the consumption of fat, reducing the consumption of meat-based protein and animal-based foods, and increasing the consumption of fruit and vegetables. The environmental impact of reducing dietary fat intake is unclear, although reducing consumption of the food category of edible fats and oils appears to have little impact. However most, but not all, studies support environmental benefits of a reduced consumption of animal-based foods and increased consumption of fruit and vegetables. In general, it appears that adhering to dietary guidelines reduces impact on the environment, but further study is required to examine the environmental impacts of animal-based foods, and fruit and vegetable intake in depth

Exploring the impact of model calibration on estimating energy savings through better space heating control

It is widely accepted that simulation tools need to be carefully configured with appropriate inputs to yield good estimates of building performance. Having a good representation of a building’s performance is particularly important when trying to generate a baseline against which energy savings are to be measured. This is especially challenging in residential buildings where there is a high dependency on occupant behaviour. Relevant data for domestic building is scarce and an option is to use existing guidelines published by organisations such as CIBSE or DOE. This paper considers the relative savings that might be expected by implementing several space heating control strategies, by evaluating the change in performance from a baseline model. The impact of calibrating the model on the results is given as is a description of the calibration approach used. It is demonstrated that potential energy savings can be either over or under predicted depending on the nature of the control strategy employed

Review of rheological behaviour of sewage sludge and its importance in the management of wastewater treatment plants

Abstract The process operation of wastewater treatment plants (WWTPs) is based on the proper set up of several physical, chemical and biological parameters. Often, issues and problems arising in the process are strictly linked to the rheological behaviour of sewage sludge (SeS). Therefore, rheological measurements, which recently have captured a growing interest, represent an important aspect to consider in the design and operation of WWTPs, especially in the sludge-handling processes. The knowledge of rheological behaviour of SeS represents a crucial step to better understand its flow behaviour and therefore optimize the performance of the processes, minimizing the costs. The SeS are non-Newtonian fluids and, to date, Bingham and Ostwald models are the most applied. This work presents an overview of scientific literature about the rheological properties of SeS and discusses the importance of its knowledge for the management of WWTPs