A new approach to modelling process and building energy flows in manufacturing industry.
Global conservation of energy and material has become a key topic among governments, businesses, local societies and academics. A point made by many on the subject of energy begin by stating the importance of conserving the earth’s natural resources, and the need to reduce greenhouse gas emissions in a bid to reduce global warming. This research is no exception, concentrating on an energy and material intensive sector of the global economy; manufacturing industry. This research formulates a methodology for modelling energy flows between a factory building, its manufacturing process systems and the materials used. The need for such an approach arises from the gap in knowledge between the understanding of energy consumed by factory buildings and process systems in manufacturing industry. Factory buildings are purpose built environments that house manufacturing processes, manufacturing plant, materials and occupants. Modern production lines are designed to optimise the flow of materials throughout a factory; to and from storage, production, assembly and distribution. Manufacturing production systems dictate the shape and size of factory buildings. This can lead to a high proportion of the overall energy consumption to be attributed to building services. The coupling of factory energy flows assists energy managers at both the facility and process levels, in order to identify efficiency improvements and reduce energy use and associated carbon emissions. A better understanding of the overall energy balance of a factory environment will allow energy to be used in a more sustainable manner. Simulation tools are widely used in the disciplines of building design and manufacturing systems engineering. Traditional building energy flow paths are well documented and are handled within dynamic building modelling tools. Globally, manufacturing activities cover a wide field of industrial practice and use a range of simulation software packages such as flow diagramming packages, computational fluid dynamics, discrete event tools, direct coding, optimisation tools etc. The increasing use of simulation makes it difficult for a manufacturing systems analyst to choose a suitable approach for energy modelling. An important aspect of the methodology described in this thesis is the coupling of energy flows that occur internally (within a factory boundary) and externally (outside a factory boundary e.g. weather) in relation to time and location within and around a factory environment. Building modelling tools provide a structured and well defined approach to monitoring energy flows within traditional built environments. The methodology extends the framework of an existing building modelling tool; the International Building Physics Toolbox (IBPT), to include the simulation of manufacturing process systems and material flow within a factory. There is a wide range of manufacturing processes used in industry so the scope of this research is reduced to thermal and electrical processes only. A thermal process is considered to be an extension of a thermal zone (such as a room), as defined in building modelling tools. Two thermal processes are considered; processes that act on a volume of gas (i.e. air) and those that act on a volume of liquid. Material flow is represented in the model by time series. The lumped capacitance method is used to approximate the change in surface temperature of a material in relation to its stored energy, long wave radiation between the material and its surroundings, and convective heat transfer. To validate the use of the IBPT algorithms to model building physics, the results derived by using the IBPT are compared with those derived by using an industry standard trusted building modelling tool called ‘Integrated Environmental Solutions Virtual Environment’ (IES VE), in comparable areas of building modelling. Three industrial case studies have been analysed, and these represent real scenarios from the automotive and aerospace manufacturing industry sectors. Two out of the three case studies include the simulation of the building (fabric and heating system), material flow and manufacturing process systems (air and liquid based). The third case study focuses on process modelling only, with future scope to include the factory building. Data obtained from industrial practice is used to validate the results of energy modelling using the proposed method. Results from the case studies demonstrate the capabilities of the proposed method of modelling factory energy flows and associated energy consumption at both facility and process level. Opportunities to reduce energy use and associated carbon emissions are also identified. The methodology does have some limitations in the form of the number of manufacturing process types represented and the complex nature of modelling real energy flows that occur within factory buildings. However the findings of the research show that an integrated approach to modelling factory energy flows through development of a building modelling framework has real benefits for manufacturing industry. These benefits are very unlikely to be realised by modelling processes and buildings separately, as is the way current modelling methods are carried out by the separate discipline areas of building design and manufacturing systems. Factory energy managers and future factory designs are example areas in which the presented integrated tool would be most beneficial used. Future research within this area could include an extension of the framework to model moisture transfer, the inclusion of further types of manufacturing process systems and further investigation into the coupling of time-driven and event-driven hybrid modelling techniques to simulate material flow both in terms of locality and thermal behaviour.
- PhD