Combining simulation and optimization for improved decision support on energy efficiency in industry

Industrial production systems in general are very complex and there is a need for decision support regarding management of the daily production as well as regarding investments to increase energy efficiency and to decrease environmental effects and overall costs. Simulation of industrial production as well as energy systems optimization may be used in such complex decision-making situations. The simulation tool is most powerful when used for design and analysis of complex production processes. This tool can give very detailed information about how the system operates, for example, information about the  disturbances that occur in the system, such as lack of raw materials, blockages or stoppages on a production line. Furthermore, it can also be used to identify bottlenecks to indicate where work in process, material, and information are being delayed. The energy systems optimization tool can provide the company management additional information for the type of investment studied. The tool is able to obtain more basic data for decision-making and thus also additional information for the production-related investment being studied. The use of the energy systems optimization tool as investment decision support when considering strategic investments for an industry with complex interactions between different production units seems greatly needed. If not adopted and used, the industry may face a risk of costly reinvestments. Although these decision-making tools individually give good results, the possibility to use them in combination increases the reliability of the results, enhances the possibility to find optimal solutions, promises improved analyses, and a better basis for decisions in industry. The energy systems optimization tool can be used to find the optimal result and the simulation tool can be used to find out whether the solution from the optimization tool is possible to run at the site. In this thesis, the discrete event simulation and energy systems optimization tools have been combined. Three Swedish industrial case studies are included: The new foundry at Volvo Powertrain in Skövde, Arla Foods dairy in Linköping and the SKF foundry in Katrineholm. Results from these cases show possibilities to decrease energy use and idling, to increase production, to combine existing and new production equipment and to decrease loss of  products. For an existing industrial system, it is always preferable to start with the optimization tool reMIND rather than the simulation tool – since it takes less time to build the optimization model and obtain results than it does to build the corresponding simulation modeling. While, for a non-existent system, it is in general a good idea to use both the simulation and the optimization tool reMIND simultaneously, because there are many uncertain data that are difficult to estimate, by using only one of them. An iterative working process may follow where both tools are used. There is a need for future work to further develop structured working processes and to improve the model to e.g. take production related support processes into account. To adapt the results in industries, improve the user friendliness of the tool and the understanding of the underlying modeling developments of the optimization tool reMIND will be necessary.Industriella system i allmänhet är mycket komplexa och det finns ett behov av beslutsstöd vid hantering av den dagliga produktionen, liksom beslut om investeringar för att öka energieffektiviteten och minska miljöpåverkan och kostnader. Simulering av industriell produktion och energisystemoptimering kan användas som beslutsstöd i sådana komplexa beslutssituationer. Simuleringsverktyg är mest kraftfullt när det används för design och analys av komplexa produktionsprocesser. Verktyget kan ge mycket detaljerad information om hur systemet fungerar, till exempel information om de störningar som inträffar i systemet såsom brist på råvaror, blockeringar eller avbrott på en produktionslinje. Dessutom kan verktyget användas för att identifiera flaskhalsar för att indikera var arbete, material och information är försenade. Energisystemoptimeringsverktyget kan ge företagsledningen ytterligare information om en eventuell studerad investering. Verktyget kan ge mer underlag för att fatta beslut och därmed ge mer information för den produktionsrelaterade investeringen som studeras. Behovet av användningen av energisystemoptimeringsverktyg som investeringsbeslutsstöd när man överväger strategiska investeringar för en industri med komplexa interaktioner mellan olika produktionsenheter bedöms vara stort. Om inte kan industrin istället möta en risk för kostsamma reinvesteringar. Även om dessa verktyg kan vara beslutsstöd var för sig och ge bra resultat, så medföljer möjligheten att kombinera dessa verktyg att tillförlitligheten av resultaten ökar, såväl som möjligheten att hitta optimala lösningar, bättre analyser och ett bättre underlag för beslut inom industrin. Optimeringsverktyget kan användas för att hitta det optimala resultatet och simuleringsverktyg kan användas för att ta reda på om lösningen från optimeringsverktyget är möjlig att realisera i verklig drift. I den här avhandlingen har diskret händelsestyrd simulering och energisystemoptimeringsverktyg kombinerats. Tre svenska industriella fallstudier är inkluderade: Volvo Powertrains nya gjuteri i Skövde, Arla Foods mejeri i Linköping och SKF-gjuteriet i Katrineholm. Resultat från dessa fall visar på möjligheterna att minska energianvändningen och tomgångsförlusterna, att öka produktionen, att kombinera ny och befintlig produktionsutrustning på ett effektivare sätt, och att minska kassation av produkter. För ett befintligt industriellt system är det alltid mer effektivt att börja med optimeringsverktyget reMIND snarare än simuleringsverktyg - eftersom det tar mindre tid att bygga en optimeringsmodell och få resultat, än det gör för att bygga en motsvarande simuleringsmodell. För ett icke-existerande system är det i allmänhet ett effektivare tillvägagångssätt att använda både simulerings och optimeringsverktyg reMIND samtidigt, eftersom det finns många osäkra data som är svåra att uppskatta, med hjälp av endast ett av verktygen. En iterativ arbetsprocess kan följa där båda verktyg används. Det finns ett behov av fortsatt arbete bl. a. av att utveckla strukturerade arbetssätt och att kunna integrera produktionsrelaterade stödprocesser i modelleringen. För att anpassa resultaten för industrin, och förbättra användarvänligheten av verktyget, utvecklingen av optimeringsverktyget reMIND kommer att behövas

Timing and sizing of investments in industrial processes– the use of an optimization tool

Investments of different kinds are vital for industries to stay competitive. However, there are several issues that need to be considered before investing, e.g. the timing and size of the investment. In this paper a methodology is presented for analysing investments form the point of view of optimal size and timing. The energy systems optimization tool reMIND is used as the basis of the modelling, and has been used in several industrial energy systems studies for various purposes. reMIND is based on Mixed Integer Linear Programming (MILP) and has been further developed to consider investments of different kinds. The different constraints needed to model the investment properly are presented together with the variables included in the objective function. A simple case study is also included to illustrate how the method is used. The results from the case study show that the timing and size of the different investments change, depending on the size of the proposed increase in production rate

Considering start-ups and shutdowns using an optimisation tool – Including a dairy production planning case study

There are many different aspects a production-planning model has to be able to handle to make a model adequate for the purpose. One aspect is the handling of start-ups and shutdowns for different processes. The production plan is likely to be changed when considering, for example, a cost connected to the start-up and/or shutdown of processes. Besides costs associated with start-ups and shutdowns, waste may be produced during the start-up and shutdown. However, there is also the possibility of carrying out soft start-ups and shutdowns or limiting the number of start-ups and shutdowns. Thus, start-ups and shutdowns have to be handled in an adequate way in models to produce reliable and accurate results. In optimisation tools, this may be dealt with by introducing certain constraints, including integers. In this paper, the implementation of alternative ways to consider start-ups and shutdowns are presented. This is done in the energy system optimisation tool reMIND, which deals with Mixed Integer Linear Programming (MILP) problems. The purpose of this paper is to show four alternatives to consider start-ups and shutdowns in optimisation models. This involves, in total, almost 50 constraints. Also, a simple dairy case study is included in the paper to visualise the effect of implementing the different alternatives to shutdowns.Funding Agencies|Swedish Energy Agency (SEA)||</p

Impact of daily work habits and working environment on employees productivity, guidelines for promoting wellbeing at work

"Darba ikdienas paradumu un darba vides stresa ietekme uz darbinieka darbaspējām, vadlīnijas veselīga dzīvesveida veicināšanai darba vietā". Darba autors: Mārtiņš Žogots. Darba zinātniskā vadītāja: Dr. med., asociētā profesore Ženija Roja. Darbs izklāstīts uz 93 lpp., ietver 23 attēlus, 10 tabulas, 8 pielikumus, 96 informatīvos avotus. Maģistra darba pētījums sastāv no 4 daļām. Pirmajā daļā ir apskatīta un analizēta literatūra par faktoriem, kas ietekmē darbinieka darbaspējas un praktiskiem veselības veicināšanas pasākumiem, darbaspēju saglabāšanai un uzlabošanai. Literatūras analīze pierāda, ka veselības veicināšanas pasākumiem ir būtiska ietekme uz darbinieka darbaspējām. Otrajā daļā ir apskatītas pētījumā izmantotās metodes, bet trešajā daļā ir apkopoti pētījuma rezultāti un veikta to analīze. Izstrādāti priekšlikumi un veselības veicināšanas pasākumi. Iegūtie pētījuma rezultāti ļauj secināt, ka būtiskākie psihoemocionālie darba vides riski ir saistīti ar darba tempu, kontroli pār veicamo darbu un ilgstošu saskari ar citiem cilvēkiem. Izstrādātas praktiskās rekomendācijas gan uzņēmuma vadībai, gan uzņēmuma darbiniekiem. Izmantotās metodes: Kopenhāgenas psihosociālās aptaujas īsā versija; Notingemas universitātes metode stresoru noteikšanai; ActPRO Wellness 360° labsajūtas indekss; darbinieku labklājības pulsa aptauja "&frankly"; Firstbeat dzīvesveida novērtējums."Impact of daily work habits and working environment on employees productivity, guidelines for promoting wellbeing at work". Author: Mārtiņš Žogots. Scientific advisor: Dr. med., associate professor Ženija Roja. Total number of pages 93, including 23 pictures, 10 tables, 8 annexes, 96 informative sources. The Master's thesis research consists of 4 parts. The first part includes analyze of literature on the factors influencing the worker's ability to work and practical measures for wellbeing, how to maintain and improve workability of employees. Literature analysis shows that wellbeing activities have a significant impact on the employee's ability to work. The second part describes the methods used in the study, while the third part summarizes the results and analyses of the study. Proposals and wellbeing activities have been developed. The obtained results of the research allow to conclude that the most important psycho-emotional risks of the work environment are related to the pace of work, control over the work performed and long periods of time in contact with other people. Practical recommendations are developed for company management and company employees. Research methods used: short version of the Copenhagen Psychosocial Survey; University of Nottingham method for determining stressors; ActPRO Wellness 360 ° Wellness Index; Employee Wellbeing Pulse Survey "&frankly"; Firstbeat Lifestyle Assessment

Combining optimisation and simulation in an energy systems analysis of a Swedish iron foundry

To face global competition, and also reduce environmental and climate impact, industry-wide changes are needed, especially regarding energy use, which is closely related to global warming. Energy efficiency is therefore an essential task for the future as it has a significant impact on both business profits and the environment. For the analysis of possible changes in industrial production processes, and to choose what changes should be made, various modelling tools can be used as a decision support. This paper uses two types of energy analysis tool: Discrete Event Simulation (DES) and Energy Systems Optimisation (ESO). The aim of this study is to describe how a DES and an ESO tool can be combined. A comprehensive five-step approach is proposed for reducing system costs and making a more robust production system. A case study representing a new investment in part of a Swedish iron foundry is also included to illustrate the method's use. The method described in this paper is based on the use of the DES program QUEST and the ESO tool reMIND. The method combination itself is generic, i.e. other similar programs can be used as well with some adjustments and adaptations. The results from the case study show that when different boundary conditions are used the result obtained from the simulation tools is not optimum, in other words, the result shows only a feasible solution and not the best way to run the factory. It is therefore important to use the optimisation tool in such cases in order to obtain the optimum operating strategy. By using the optimisation tool a substantial amount of resources can be saved. The results also show that the combination of optimisation and simulation tools is useful to provide very detailed information about how the system works and to predict system behaviour as well as to minimise the system cost.funding agencies|Swedish Energy Agency (SEA)||</p

Optimization as investment decision supportin a Swedish medium-sized iron foundry : a move beyond traditional energy auditing

Due to increased globalisation, industries are facing greater competition that is pressing companies into decreasing their expenses in order to increase their profits. As regards Swedish industry, it has been faced with substantial increases in energy prices in recent years. Barriers to energy efficiency such as imperfect information inhibit investments in energy efficiency measures, energy audits being one means of reducing barriers and overcoming imperfect information. However, an evaluation of such energy audits in Sweden reveals that it is chiefly low-cost measures that are undertaken as a result of an audit. Moreover, these audits often tend to focus on support processes such as ventilation, lighting, air compressors etc., while measures impacting production processes are often not as extensively covered, which underlines the need for further support in addition to energy audits. Decision support is practised in a variety of different disciplines such as optimization and simulation and the aim of this paper is to explore whether investment decision support practices may be used successfully towards small and medium-sized manufacturers in Sweden when complex production-related investment decisions are taken. The optimization results from the different cases, involving a foundry’s investment in a new melting unit, indicate that with no electricity price fluctuations over the day, the investment seems sound as it lowers the overall energy costs. However, with fluctuating electricity prices, there are no large differences in energy costs between the option of retaining the existing five melting furnaces at the foundry and investing in a twin furnace and removing the holding furnaces – which was the initial investment plan for the foundry in the study. It would not have been possible to achieve this outcome without the use of investment decision support such as MIND. One of the main conclusions in this paper is that investment decision support, when strategic investment decisions are to be taken, may be a means of emphasising energy efficiency for energy-intensive SMEs beyond the level of traditional energy auditing.Original publication: Patrik Thollander, Nawzad Mardan and Magnus Karlsson, Optimization as investment decision supportin a Swedish medium-sized iron foundry: a move beyond traditional energy auditing, 2009, Applied Energy, (86), 4, 433-440. http://dx.doi.org/10.1016/j.apenergy.2008.08.012. Copyright: Elsevier B.V., http://www.elsevier.com/</p

Designing Policies and Programmes for Improved Energy Efficiency in Industrial SMEs

Climate change, due to anthropogenic emissions of greenhouse gases, is driving policymakers to make decisions to promote more efficient energy use. Improved industrial energy efficiency is said to play a key role in the transition to more carbon-neutral energy systems. In most countries, industrial small and medium-sized enterprises (SMEs) represent 95% or more of the total number of companies. Thus, SMEs, apart from using energy, are a major driver in the economy with regard to innovation, GDP growth, employment, investments, exports, etc. Despite this, research and policy activities related to SMEs have been scarce, calling for contributions in the field. Therefore, the aim of this paper is to critically assess how adequate energy efficiency policy programmes for industrial SMEs could be designed. Results show that scientific publications in the field differ in scope and origin, but a major emphasis of the scientific papers has been on barriers to and drivers for energy efficiency. Scientific contributions from studies of energy policy programmes primarily cover energy audit programmes and show that the major energy efficiency measures from industrial SMEs are found in support processes. The review further reveals an imbalance in geographic scope of the papers within the field, where a vast majority of the papers emanate from Europe, calling for scientific publications from other parts of the world. The study synthesizes the findings into a general method on how to design efficiency programs for the sector