Generic Case Study Research Articles

Dynamic modeling for evaluation of triple-pipe configuration potential in geothermal district heating networks

District Heating (DH) systems will play an important role in future sustainable energy systems. Existing networks can be optimized by lowering primary return temperatures in order to improve the use of geothermal resources. This can be done by installing triple-pipe systems. This paper defines the concept of triple-pipe configurations as it is understood in France. The objective of this paper is to demonstrate the relevance of those configurations for optimizing geothermal DH system efficiency. A dynamic thermal-hydraulic model was developed using the programming language Modelica. A generic case study is modeled considering the extension of an existing network. It is shown that triple-pipe configurations offer lower return temperatures and gas consumption, while increasing of the renewable energy share in the network energy mix.

Towards low carbon business park energy systems: A holistic techno-economic optimisation model

In this paper, an energy model is developed customised for the design of low carbon energy systems on business park scale. The model comprises two sequential stages: In the first stage, heat recovery within the system is maximised, while utility system and energy storage are optimally integrated and designed to fulfil remaining energy requirements at minimum total annualised costs. Simultaneously, heat networks can be deployed to transfer heat between separate parts of the system. Intra-annual variations in thermal and electrical energy demand and supply are taken into account, next to a carbon emission cap. In the second stage, the model generates an optimal multi-period heat exchanger network (HEN) enabling all required heat exchanges. The proposed model builds upon a multi-period energy integration model that can deal with restrictions in heat exchange. This model is combined with a generic technology model that can be manipulated to represent the various thermal or electrical energy conversion technology units in the utility system. Moreover, simple models for thermal and electrical energy storage are included that allow for calculation of storage levels subject to energy loss over time, without increasing the number of time steps to be analysed. A method for automated superstructure expansion is incorporated in the solution procedure to enable the optimisation of the number of units per technology in the configuration of the utility system. The HEN is automatically generated using a multi-period stage-wise heat exchanger network model. The energy model is applied to a literature example and to a generic case study demonstrating its holistic and integrated approach towards the synthesis of low carbon energy systems.

Strict Lyapunov functions for time-varying systems with persistency of excitation

We study the stability of the origin for a class of linear time-varying systems with a drift that may be divided in two parts. Under the action of the first, a function of the trajectories is guaranteed to converge to zero; under the action of the second, the solutions are restricted to a periodic orbit. Hence, by assumption, the system’s trajectories are bounded. Our main results focus on two generic case studies that are motivated by common nonlinear control problems: model-reference adaptive control, control of nonholonomic systems, tracking control problems, to name a few. Then, based on the standing assumption that the system’s dynamics is persistently excited, we construct a time-dependent Lyapunov function that has a negative definite derivative. Our main statements may be regarded as off-the-shelf tools of analysis for linear and nonlinear time-varying systems.

International collaboration in the IAEA nuclear hydrogen production program for benchmarking of HEEP

The Hydrogen Economic Evaluation Programme (HEEP) was developed by the International Atomic Energy Agency (IAEA) to perform economic assessment of nuclear hydrogen production technologies. Yet HEEP is still under update to reflect latest advances in nuclear hydrogen production research and development. This paper presents an overview of HEEP and latest benchmarking results with emphasis on its capabilities. Comparative assessment was performed to examine the accuracy of the calculations. Executing same case studies several times showed accurate reproducibility of the results which assured the consistency of HEEP results. Five generic and detailed case studies with different nuclear power plants and hydrogen generation plants were considered in comparative assessment with the results of G4-ECONS and H2A software. The chronological and financial parameters were also varied through these cases. Furthermore, to demonstrate the capabilities of HEEP, some results of other comparative case studies that were performed by PAEC in Pakistan and AECL in Canada will be highlighted. The consistency and accuracy of the performed analyses confirm the credibility and reliability of HEEP.

Including stakeholder input in formulating and solving real-world optimisation problems: Generic framework and case study

Multi-objective evolutionary algorithms (MOEAs) are becoming increasingly popular for solving formal environmental and water resources optimisation problems. In the past, the focus of these studies has generally been on methodological issues related to the optimisation algorithm. However, in recent years, there has been increased recognition of the need to apply these approaches to real-world problems to facilitate the realisation of their full potential. In order to assist with this, a framework for including stakeholder input in real-world optimisation problems is introduced in this paper, including a conceptual framework and a procedure for implementing it. The framework is applied to an urban water supply security study for Adelaide, South Australia. This study highlights the role of stakeholder input at the various stages of the optimisation process, as well as the resulting changes in the formulation, analysis and results. A discussion of the lessons learnt from the case study is also provided.

Addressing dynamic risk in the petroleum industry by means of innovative analysis solutions

The importance of Integrated Operations (IO) is rapidly growing in today's petroleum industry. It is being developed to improve capture of real-time safety barrier data and to process, visualize and share this information for closer onshore-offshore collaboration and expert support. Increased capacity in the communication infrastructure (e.g. via fibre optics) and integration and processing of data from various sources enable more accurate methods of risk analysis that would have been previously considered time- costly. For this reason this study addresses the topic of dynamic approach to risk in an IO context by presenting and integrating advanced techniques of hazard identification and risk assessment, such as: DyPASI (Dynamic Procedure for Atypical Scenarios Identification), DRA (Dynamic Risk Assessment) and the Risk Barometer methodology. DyPASI was developed in the EC project iNTeg-Risk. This technique aims to produce complete and updated HAZID process. Atypical accident scenarios, which by definition are deviating from normal expectations of unwanted events or worst case reference scenarios, are identified through a systematic screening of related emerging risk notions. The DRA method aims to estimate updated expected frequency of accident scenarios by means of Bayesian inference. Real time abnormal situations or incident data are used as new information to update the failure probabilities of the system safety barriers, which necessarily affect the overall scenario frequencies and the related risk picture. The Risk Barometer was developed within the Center for Integrated Operations in the Petroleum Industry. It aims to continuously monitor specific indicators measuring the status of critical safety barriers and translate them into risk picture changes. Its result is an intuitive graphical representation of the overall risk level in order to support decision makers in daily operations. The description of these techniques will be accompanied by a preliminary application on a generic case-study, in order to demonstrate the effectiveness of such dynamic approach in risk management and prevention of related major accidents.

Integration of biomass into urban energy systems for heat and power. Part I: An MILP based spatial optimization methodology

The paper presents a mixed integer linear programming (MILP) approach to optimize multi-biomass and natural gas supply chain strategic design for heat and power generation in urban areas. The focus is on spatial and temporal allocation of biomass supply, storage, processing, transport and energy conversion (heat and CHP) to match the heat demand of residential end users. The main aim lies on the representation of the relationships between the biomass processing and biofuel energy conversion steps, and on the trade-offs between centralized district heating plants and local heat generation systems. After a description of state of the art and research trends in urban energy systems and bioenergy modelling, an application of the methodology to a generic case study is proposed. With the assumed techno-economic parameters, biomass based thermal energy generation results competitive with natural gas, while district heating network results the main option for urban areas with high thermal energy demand density. Potential further applications of this model are also described, together with main barriers for development of bioenergy routes for urban areas.

Life Cycle Assessment (ISO 14040) Implementation in Foods of Animal and Plant Origin: Review

The importance of environmental protection has been recently upgraded due to the continuously increasing environmental pollution load. Life Cycle Assessment (LCA), wellknown as ISO 14040, has been repeatedly shown to be a useful and powerful tool for assessing the environmental performance of industrial processes, both in the European and American continents as well as in many Asian countries (such as Japan and China). To the best of our knowledge, almost no information is provided in relation to LCA implementation in Africa apart from an article related to Egypt. Although food industries are not considered to be among the most heavily polluting ones, for some like olive oil, wine, dairy, and meat processing, their impact on the environment is a heavy burden. The introduction of LCA aimed at identifying both inputs and outputs to find out which are the most detrimental to the environment in terms of water/energy consumption and solid/liquid and gas releases. In this review, a thorough coverage of literature was made in an attempt to compare the implementation of LCA to a variety of products of both plant and animal origin. It was concluded that there is a high number of subsystems suggested for the same product, thereby, occasionally leading to confusion. An idea toward solving the problem is to proceed to some sort of standardization by means of several generic case studies of LCA implementation, similarly to what had happened in the case of Hazard Analysis and Critical Control Points (HACCP) implementation in the United States, Canada, Australia, United Kingdom, and other countries.

Generic Model and Case Studies of Microwave Power Sensor Calibration Using Direct Comparison Transfer

This paper proposes a generic model for analyzing the microwave power sensor calibration by direct comparison transfer. The model is derived using a signal flow graph together with nontouching loop rule analyses. The proposed model is investigated through several case studies which are commonly encountered and provides a theoretical basis for practical applications. Finally, realizations of the derived calibration equations for some practical cases are also discussed.

Predicting dam failure risk for sustainable flood retention basins: A generic case study for the wider Greater Manchester area

This study aims to provide a rapid screening tool for assessment of sustainable flood retention basins (SFRBs) to predict corresponding dam failure risks. A rapid expert-based assessment method for dam failure of SFRB supported by an artificial neural network (ANN) model has been presented. Flood storage was assessed for 110 SFRB and the corresponding Dam Failure Risk was evaluated for all dams across the wider Greater Manchester study area. The results show that Dam Failure Risk can be estimated by using the variables Dam Height, Dam Length, Maximum Flood Water Volume, Flood Water Surface Area, Mean Annual Rainfall (based on Met Office data), Altitude, Catchment Size, Urban Catchment Proportion, Forest Catchment Proportion and Managed Maximum Flood Water Volume. A cross-validation R2 value of 0.70 for the ANN model signifies that the tool is likely to predict variables well for new data sets. Traditionally, dams are considered safe because they have been built according to high technical standards. However, many dams that were constructed decades ago do not meet the current state-of-the-art dam design guidelines. Spatial distribution maps show that dam failure risks of SFRB located near cities are higher than those situated in rural locations. The proposed tool could be used as an early warning system in times of heavy rainfall.

High-throughput automation design considerations for biotechnology processes involving RNA purification protocols using multi-centrifuge bioseparation steps

Design of an automation line is a multi-objective optimization problem involving throughput, yield, floor space and cost constraints. The paper examines the feasibility of a computer-aided automation design for biotechnology applications using Arena(TM) software. A generic case study chosen for this study involves a sequence of steps in a preparation process of RNA from tissue-cultured cells. These steps involve repetitive usage of centrifuging operations to perform separation of biochemical substances. A sample must be loaded onto a centrifuge by a pick-and-place device (typically a robot manipulator). Consecutive centrifuging steps may involve multiple centrifuges as well as robots, or some measure of equipment sharing. The paper proposes a unified simplified cost model for all design objectives (throughput, space utilization, process capital and operational cost) and a quantitative selection criterion to allow for an optimal automation design.

Financial and economic determinants of collective action: The case of wastewater management

Where public environmental funds support development of wastewater infrastructure, funding institutions ensure the economic use of funds, while the beneficiaries minimize their own costs. In rural areas, there is often a choice between decentralized or centralized (multi-village) systems: if the centralized system is most economic, then only this system is eligible for public funding. However, its implementation requires a voluntary cooperation of the concerned communities, who need to organize themselves to develop and run the infrastructure. The paper analyzes the social determinants of collaboration in a generic case study, using the following variables: method of (economic) assessment, modeled by the social discount rate, funding policy, modeled by the funding rate, and users' self-organization, modeled by cost sharing. In a borderline situation, where the centralized system turns out to be most economic, but this assessment is contingent on the assessment method, collective action may fail: the advantages of collective action from funding are too small to outweigh organizational deficiencies. Considering in this situation sanitation as a human right, authors recommend using innovative forms of organization and, if these fail, reassessing either the amount of funding or the eligibility for funding of more acceptable alternatives.

Robust Data-Driven Modeling Approach for Real-Time Final Product Quality Prediction in Batch Process Operation

Making on-specification products is a primary goal, and also a challenge in chemical batch process operation. Due to the uncertainty of raw materials and instability of operating conditions, it may not produce the desired on-spec final product. It would be helpful if one can predict the product quality during each operation, so that one can make adjustments to process conditions in order to make on-spec product. This paper addresses the issue of real-time prediction of final product quality during a batch operation. First, a data-driven modeling approach is presented. This multimodel approach uses available process information up to the current points to capture their time-varying relationships with the final product quality during the course of operation, so that the prognosis of product quality can be obtained in real-time. Then, due to its data-driven nature, the focus is given on how to make the models robust in order to eliminate the effect of noise, especially, outliers in the data. A model-based outlier detection method is presented. The proposed approach is applied to a generic chemical batch case study, with its prediction performance being evaluated.

Nonlinear FDI based on state derivatives, as provided by inertial measurement units

Various strategies based on differential geometry or system inversion have been proposed to deal with fault detection and isolation (FDI) for nonlinear systems. Many of them require the computation of successive derivatives of inputs and outputs, which might be unrealistic in practical applications where measurements suffer noise and disturbances. In this paper, we take advantage of the fact that, in domains such as aerospace or robotics, sensors allow the measurement of first-order derivatives of state variables. This information, along with the redundancy provided by the control module can be used to generate residuals. Such a procedure is proposed and applied to a generic 2D aeronautical case study.

Guidance on Safety/Health for Process Intensification Including MS Design. Part IV: Case Studies

AbstractThe new technology of process intensification by multiscale equipment can significantly contribute to the achievement of a safer design by switching from batch/semi‐batch to continuous operation combined with a reduction of the inventory of hazardous substances in critical stages. On the other hand, the shift to higher space‐time‐yields and temperatures comprises new risks (see Parts I and II). A tool was developed for preliminary risk assessment to cover characteristic features of micro‐designed equipment, called HAZOP‐LIKE study (see Part III). The generic case studies were applied to two demonstration projects within the IMPULSE project: sulfur dioxide oxidation and the alkylation reaction for the production of ionic liquids. The generic templates proved to be applicable and support comprehensive risk analysis studies on processes with hidden deviations not obviously following traditional HAZOP studies.

Stochastic hydrogeological modelling of fractured rocks: a generic case study in the Mórágy Granite Formation (South Hungary)

Stochastic hydrogeological modelling of fractured rocks: a generic case study in the Mórágy Granite Formation (South Hungary)In connection with the Hungarian radioactive waste disposal program a detailed study of the mass properties of the potential host rock (granite) has been carried out. Using the results of this study the various parameters (orientation, length, intensity, transmissivity, etc.) describing a fracture set were estimated on the basis of statistical considerations. These estimates served as basic input parameters for stochastic hydrogeological modelling of discrete fracture networks (DFN), which is a strongly developing area of hydrology, providing geologically realistic geometry for site investigations. The synthetic fracture systems generated were tested against some (but not all) field observations. The models built up on the basis of the statistical descriptions showed the same equivalent hydraulic conductivity for the modelled region as the field measurements. In addition, the models reproduce the observed hydraulic head-scattering along vertical boreholes. On the basis of the stochastic simulations of the fracture system some input parameters for the performance assessment of the planned repository were investigated. Calculation of flows into a planned disposal tunnel indicated that if the hydraulic conductivity of the material in the tunnel is the only variable parameter then there are two thresholds: under 1×10-9m/s and above 1×10-5m/s further change of the hydraulic conductivity does not dramatically affect the inflow.

Playing Games with Timed Games

In this paper we focus on property-preserving preorders between timed game automata and their application to control of partially observable systems. Following the example of timed simulation between timed automata, we define timed alternating simulation as a preorder between timed game automata, which preserves controllability. We define a method to reduce the timed alternating simulation problem to a safety game. We show how timed alternating simulation can be used to control efficiently a partially observable system. This method is illustrated by a generic case study.

Application of the Spanish methodological approach for biosphere assessment to a generic high-level waste disposal site

A methodological approach which includes conceptual developments, methodological aspects and software tools have been developed in the Spanish context, based on the BIOMASS “Reference Biospheres Methodology”. The biosphere assessments have to be undertaken with the aim of demonstrating compliance with principles and regulations established to limit the possible radiological impact of radioactive waste disposals on human health and on the environment, and to ensure that future generations will not be exposed to higher radiation levels than those that would be acceptable today. The biosphere in the context of high-level waste disposal is defined as the collection of various radionuclide transfer pathways that may result in releases into the surface environment, transport within and between the biosphere receptors, exposure of humans and biota, and the doses/risks associated with such exposures. The assessments need to take into account the complexity of the biosphere, the nature of the radionuclides released and the long timescales considered. It is also necessary to make assumptions related to the habits and lifestyle of the exposed population, human activities in the long term and possible modifications of the biosphere. A summary on the Spanish methodological approach for biosphere assessment are presented here as well as its application in a Spanish generic case study. A reference scenario has been developed based on current conditions at a site located in Central-West Spain, to indicate the potential impact to the actual population. In addition, environmental change has been considered qualitatively through the use of interaction matrices and transition diagrams. Unit source terms of 36Cl, 79Se, 99Tc, 129I, 135Cs, 226Ra, 231Pa, 238U, 237Np and 239Pu have been taken. Two exposure groups of infants and adults have been chosen for dose calculations. Results are presented and their robustness is evaluated through the use of uncertainty and sensitivity analyses.

Identification of ambiguity in the case study research typology: what is a unit of analysis?

PurposeAt the moment central concepts relating to the case study strategy are insufficiently understood. This is unfortunate in that the truth value of results inferred from case studies may be questioned. Given the fact that case studies are widely employed in many fields the identified ambiguities represent an imperative dilemma of great consequences to the research community in general. Hence, the objectives are to identify ambiguities, explore further consequences of ambiguities and to propose a rival understanding that will remedy the present inconsistencies.Design/methodology/approachAn analysis of literature was undertaken. Based on a critical assessment of existing theoretical concepts, modifications and novel conceptual ideas are proposed. The proposed framework is, moreover, thoroughly exemplified by a business‐to‐business research example, thereby enhancing applicability when future case studies are undertaken.FindingsThe outcome was a string of generic case study characteristics, an elaboration of ambiguity and consequences of the identified ambiguity, a modification of Yins' case study design typology, and finally an integrative theoretical framework that illustrates an alternative conception of the unit of analysis and the case. Accepting the criticisms and ideas presented makes it easier to identify and demarcate units of analysis that are comparable with the original analyzed unit of analysis. This will enhance the probability of authenticity and fittingness of inferred case results.Originality/valueThe contributions of this paper will facilitate a higher level of awareness about the assumptions of the paradigmatic posture researchers hold. This will cause researchers to craft more logical coherent designs and conduct better case studies across fields of theories. Moreover, they will to a higher extent be able to understand rival points of view, enabling them to construct more nuanced and astute discussions and novel insights.

Priority areas for future research identified by Dienet

The European Dienet project addressed modelling of die compaction for a range of materials. This was undertaken through three generic case studies. In the course of the work, potential areas for future research were identified. The views of the members of the Dienet group were canvassed and there was broad agreement that two areas are of the highest priority: modelling of fill, flow, transfer and low pressure compaction, including validation techniques; and modelling of cracking, including validation techniques.