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Optimal Design of Inherently Safer Domestic CHP Systems
Abstract
The residential co-generation system is a promising strategy to satisfy the electricity and hot water demands in residential complexes. This is an attractive option from both economic and environmental points of view; however, the associated risk has not been accounted for. It is very important to consider the risk associated with residential co-generation systems because the involved units use volatile fuels such as natural gas or liquefied petroleum gas. Therefore, this paper presents an optimization approach for designing residential co-generation systems through a multi-objective optimization formulation that simultaneously accounts for minimizing the total annual cost and the environmental impact as well as the associated risk to satisfy the electricity and hot water demands in a residential complex. The proposed model incorporates the optimal selection for the technologies used as well as the operation. A case study for a residential complex in Mexico is presented to show the applicability of the proposed approach, where it was shown to be possible to obtain attractive solutions from economic, environmental, and safety points of view.
... The optimization objective is minimizing the total annual cost and the associated CO 2 emission. Fuentes-Cortés et al. [34] presented an optimization approach that simultaneously minimizing the total annual cost and the greenhouse gas emissions as well as the associated risk to satisfy the hot water and electricity energy demands through a multi-objective optimization formulation in a residential complex. ...
... The total annual operating cost involves the annual natural gas cost C f , the start-up cost C st , and the electricity importation cost C buy [see Eq. (33)]. The natural gas cost includes the natural gas cost of GT, FB, and HWB, which are provided by Eq. (34), where P f is the [56], BT, CT, FB, and HWB [43], respectively. Eq. (36) provides the total annual cost of electricity imported from the local power grid, where P j,t buy is the specific electricity importation price. ...
... The decision maker can select a satisfactory compromise solution from the achieved non-dominated solutions. Among the different multi-objective optimization solution methodologies, the e-constraint method [57] is one of the widely used method to generate the Pareto set by solving a sequence of constrained single objective optimization problems [18,34,58]. In the present study, the e-constrained method and solving code [59] are applied to solve the multi-objective optimization model. ...
... The optimization methods are more flexible because of their capability to tackle conflicting objectives, which can be solved through a multi-objective optimization (MOO) scheme. This type of methods include the integration of quantitative risk assessment (QRA) for safety analysis in the optimization approach focusing on economics, safety and environment (Fuentes-Cortés et al., 2016), an optimization technique for analyzing design alternates (Ruiz-Femenia et al., 2017) and a multidimensional optimization method to concentrate on safety, environment, economics, and sustainability aspects (Guillen-Cuevas et al., 2018). Besides these formal methods, a new concept has now been introduced for the identification of hazard prevention strategies (HPS) in process designing via inherent safety assessment and can be used at the earlier design stages. ...
Hazards associated with chemical processes can lead to accidents and require therefore proper management. An inherent safety strategy is a proactive approach to serve this purpose, one capable of minimizing hazards whilst offering sustainable process design. Current inherent safety techniques are limited to comparing process routes and selecting safer one using the process parameters, whereas process equipment characteristics are rarely scrutinized. Therefore, this paper consolidates a new technique that integrates the mutually shared attributes of process equipment, in order to offer inherently safer process design at the preliminary design stage. Inherent safety assessment for process equipment (ISAPE) consists of an indexing procedure, followed by risk assessment. The indexing procedure can highlight the critical process equipment, which can be further studied through risk assessment. When the risk is beyond acceptable threshold and must be minimized, inherent safety concepts are implemented, leading towards inherently safer process design. The complete ISAPE technique is exhibited through the case study of the acetone production process. In this case study, various ISD options have been applied to the critical process equipment, identified through the proposed indexing; the options have then been compared to select the best one. The method is easy to use, and as such, it is suitable to be put into practice by design engineers at the preliminary design stage.
... In Eq. (5), ε j is taken in the range of the minimum and maximum values of the fuel consumption objective function as defined in Eq. (4), where F B max and F B min are the maximum and minimum values of the fuel consumption objective function, and GRID is the grid point number that can be adjusted to obtain a rich representation of the Pareto frontier. Thus, dual-objective optimization problem is formulated based on the solution of constrained single objective optimization problems [48][49][50]. Then, the ε-constraint solving code [51] is applied to solve the dual-objective optimization model. ...
Water and energy are inextricably linked in various industrial applications. In a Rankine cycle-based combined heat and power plant, water is used as a working fluid for power generation and as a heat carrier. The water used as heat carrier is typically incompletely recovered. Therefore, a considerable amount of make-up water is required. Energy-intensive water treatment technologies are typically used given the strict quality requirements for boiler feed water. Thus, a systematic approach is required for the synthesis and optimization of water desalination and energy conversion processes. In this study, a novel water desalination system that couples thermal membrane distillation and reverse osmosis is proposed. A water–energy integration system that features strong nexus of water and energy is then developed. A dual-objective mathematical model is also formulated for the thermodynamic analysis and optimization of the novel system to minimize fuel and freshwater consumption. Furthermore, a case study is elaborated to validate the proposed novel integration system and optimization methodology. A sensitivity analysis of the key parameters on the performance of the novel system is also conducted. The water consumption objective optimization results show that the freshwater consumption of the proposed novel water–energy integration system is reduced by 54.8% compared with the conventional system. Similarly, the results achieved from minimizing the fuel consumption show that the fuel and freshwater consumptions of the proposed novel water–energy integration system are reduced by 1.7% and 21.0%, respectively, compared with those of the conventional system. The Pareto frontier achieved from the dual-objective optimization offers a trade-off between water and fuel consumption for the proposed water–energy integration system.
... Combined heat and power (cogeneration) systems allow recovering significant amounts of waste heat (Bamufleh et al. 2013). Recently, cogeneration systems have been considered in residential complexes (Fuentes-Cortes et al. 2015a), where safety represents an important factor (Fuentes-Cortes et al. 2015b). Furthermore, there have been reported some approaches to account for the sustainability of cogeneration systems (Rosato et al. 2017), which involve the use of solar energy (Sanchez-Bautista et al. 2015), biofuels ) and other integration approaches (Tippawan et al. 2015). ...
This paper presents a multi-objective optimization formulation for enhancing the sustainable development of a residential complex. The approach accounts for the water-energy-waste nexus of the complex and enables various pathways for system integration. For conserving the fresh water demands, the proposed model includes the synthesis of water networks while accounting for wastewater reclamation and recycle and rainwater harvesting. The proposed model also incorporates the optimal design of a residential cogeneration unit to satisfy the demands for electric power and hot water. An absorption refrigeration system is considered to utilize waste heat and provide the needed refrigeration. The emitted carbon dioxide is fed to an algae growth system, which is integrated with the use of reclaimed water. A solid-waste gasification system is considered to provide electric power and heat to the residential complex. The optimization approach accounts for all the interactions of the involved units and for the seasonal variabilities of the system. A case study for a residential complex of Mexico is solved.
... Ren et al. (2008) reviewed two typical micro CHP alternatives with two different operating modes including minimum-cost operation and minimum-emission operation. Jiang-Jiang et al. (2010) analyzed the technical, environmental, and economic performances of CHP systems following the thermal and electricity demand management in different climate zones in China, and Fuentes-Cortes et al. (2015a) presented different models to determine the size and operating scheme for residential CHP systems, where the annual cost and greenhouse gas emissions are minimized, where the multi-generation system accounts for building complexes (Fuentes-Cortes et al. 2016a) and the associated risk in the residential cogeneration system (Fuentes-Cortes et al. 2016b). ...
This paper presents a multi-objective optimization formulation for designing domestic cogeneration systems to satisfy thermal and electric energy demands. The proposed model is formulated as a multi-objective mixed-integer nonlinear programming model, which incorporates as economic objective function the minimization of the total annual cost, which includes the capital costs for the new units and the thermal storage system as well as the operating and maintenance costs. The model also incorporates an environmental objective function, which accounts for the life cycle assessment through the Eco-indicator 99 method to account for the damages to the resources, human health, and ecosystem quality. The proposed model allows considering the interaction with the external users and the external electric grid. The optimization formulation is solved to generate design alternatives to establish tradeoffs among the considered objectives.
This work addresses the multi‐objective design of water, energy and food supply systems in isolated rural communities using local resources. The approach used considers objective functions based on life cycle analysis such as water and carbon footprint, as well as economic performance considering the application and integration of normalized metrics to address the water‐energy‐environment‐food nexus. The results show that it is possible to build robust and accessible metrics for the analysis of problems with various design objective functions in decision‐making environments. The optimization problem considers decision variables associated with the sizing of units such as photovoltaic panels, wind turbines, thermal and electrical energy storage, wood‐fired boilers and the integration of food production systems involving aquaculture and local corn production. Water management is associated with domestic activities and crop irrigation.
The accomplishments of inherent safety in the field of loss prevention thus far are impressive due to its scientific philosophy: reducing risks at source rather than adding engineered and procedural protections. Generally, the implementation of inherent safety can be done through a cohesive set of fourteen principles elucidated by Kletz and Amyotte. This work, guided by the fourteen principles, presents a systematic review on the implementation methodologies of inherent safety. Firstly, PRISMA procedure was adopted to select eligible literatures according to inclusive and exclusive criteria. After obtaining the selected literatures, the preference, level of application, and gaps in using these principles were critically analyzed. Of the fourteen principles, intensification, substitution, attenuation, simplification, limitation of effects, and avoidance of knock-on effects are preferable to implementing inherent safety in chemical process. Although the remaining principles are also potentially useful, they are not commonly used due to their costs and complexities of implementation. Overall, this work presents a complete spectrum to look across the implementation methodologies of inherent safety and concludes with some holistic and inclusive approaches as future research recommendations.
Chemical process manufacturing is associated with risks, which cannot be eliminated. Anyhow, controlling or minimizing of risks is possible up to a certain extent through various process safety strategies. Among these strategies, the inherent approach offers a sustainable process design. This review aims to offer an extensive survey regarding the bibliometrics and the features of the state-of-the-art inherent assessment methods. For the bibliometric part, numerous trends like publication trend, authors and geographical cooperation and prominent keywords are presented using the VOSviewer software. For the second intention, the scope and features of inherent assessments methods for sustainable process design are discussed in addition to the historical development of these methods. The techniques are categorized among seven groups based on the method adopted for inherent assessment along with the benefits and detriments of each group. It is revealed that initially, the inherent assessment has focused on the comparison of various process routes, whereas, the modern methods intend to minimize the risk. Furthermore, it is recognized that the process equipment approach is not much explored yet, which may improve the sustainable process designing via the equipment characteristics. Finally, the limitations of present schemes and future research directions for inherent assessment implications in the sustainable process design are also highlighted, such that the objectives of economic, healthier, safer and environmental-friendly process plants can be materialized.
This work addresses the optimal sizing and selection of the most used technologies reported in literature for energy and water supply of sustainable buildings. The addressed technologies includes Combined Heat and Power units, solar collectors, photovoltaic panels, conventional boilers, wind turbines, Organic Rankine Cycles, biogas production and water treatment systems. The selection technology problem is cast as an optimization model which takes into account embedded nonlinear behavior of the addressed equipment, especially the ones associated with operative efficiency, and dynamics of the storage units. The renewable energy generation, total annual cost, emissions generated and water consumption of the system are used as objective functions. Since some of these objective functions are contradictory, a multi-objective and multi-scenario Mixed Integer nonlinear optimization approach was used to reach trade-off solutions. The multi-objective approach presented allows to define the preferences of the designer based on predefined weights for reaching trade-off solutions using a dimensional approach. The environmental and energy profiles of a residential building in the Pacific Coast of Mexico are presented as Case Study. The results show the importance of including the nonlinear behavior of the technologies for defining a suitable operational policy as well as the effect of using different criteria about the design of water-energy systems.
Inherent safety aspects are not usually considered as a driving force during the conceptual design stage of chemical plants. Instead, after the selection of the optimal economic flowsheet, safety is added to the design. However, this sequential design approach could reach to inferior designs due to protection devices’ cost overrun. The objective of this work is to implement a strategy to simultaneously design a profitable and inherently safer distillation train. Two safety indexes, a disaggregated version of the Safety Weighted Hazard Index and Dow’s Fire and Explosion Index, have been adapted to quantify the inherent safety performance. A large-scale multi-objective MILP problem is formulated. Thus, two strategies of objective reduction are utilized: Principal Component Analysis coupled with Deb’s algorithm and a method based on the dominance structure. The results prove the suitability of these safety index as inherently safer metrics, and showcase the ability of the objective reduction methods to discriminate among the inherent safety criteria.
This work presents a multi-objective optimization model for the design of an integrated residential complex, which incorporates the proper use of available resources and wastes through recycling and reusing networks. The proposed model involves the proper use of water accounting for rainwater harvesting and the reuse of reclaimed water. The model also includes the design of a cogeneration system to satisfy electricity demands as well as hot water demands. The treatment of the produced solid waste is also incorporated through an incineration system, and an algae system is involved for sequestering the associated emissions. The proposed model aims to satisfy the energy, heat and water demands, and the treatment for the residues with the objective to minimize the associated cost and the associated emissions. Furthermore, the proposed model includes an objective function associated to the minimization of the damage to the health of the inhabitants.
This paper addresses the status, problems and development of distributed energy resources in developing countries. We have focused on the projects in Latin America, Asia, Eastern Europe and North Africa. The problems for developing new energy technologies are linked to the particular conditions as regulated markets, energy policies, urban planning and development, low-income communities, environmental impact and economic instability. We are presenting a perspective based on the literature review of the different proposals for solving the particular problems associated to the implementation of energy projects under the modeling perspective, highlighting the residential environment and domestic applications. Five different fields used on modeling approaches are included in the review: technologic development, economic performance, environmental impact, social context and modeling proposals. We have identified the addressed problems, the applied modeling techniques, the trends showed by the results presented and the expectations for future works in the field of distributed generation.
This work explores the impact of re-adjusting demand patterns (electricity and hot water) of building occupants on the economic and environmental performance of combined heat and power (CHP) systems. Trade-off analysis reveals that adjustments in demand patterns provide significant flexibility to synchronize electricity and hot water demands and with this it is possible to minimize water usage, emissions, and cost. As expected, however, such benefits come at expense of significant occupant dissatisfaction. To address this issue, we use a multi-stakeholder optimization framework that takes occupant priorities into account and computes a compromise solution that minimizes the collective stakeholder dissatisfaction. By using this framework, we find that there exist non-obvious CHP operating policies that achieve nearly perfect tracking of nominal occupant demands while significantly improving economic and environmental performance. The proposed framework can be used to inform occupants on the impact of their priorities on CHP performance.
The environmental policies associated to the reduction the carbon dioxide emissions have been based on economic penalizations for the generated greenhouse gas emissions. One of the objectives of these strategies is to stimulate the developing of new energy technologies or improving the efficiency of the current generation schemes. This work evaluates the impact of carbon policies in the design of combined heat and power systems (CHP) involving biogas usage. This paper presents a mixed-integer nonlinear programming model for designing a CHP system interconnected to the grid that allows selecting and sizing the prime mover and the thermal storage tank for supplying the energy demand in a housing complex. A case study from Mexico is presented, where the multi-objective problem presents different strategies used for monetizing the externalities associated to the carbon dioxide emissions, which are compared with the results of using compromise solutions. The results show that the strategies of monetization do not have a significant effect in the design and they do not result in an incentive for biogas consumption. On the other hand, the compromise solutions result in a trade-off between the economic and environmental objectives and they stimulate the developing of local biogas markets.
This paper presents an optimization approach for designing cogeneration systems using flares and vents under abnormal conditions from different industrial plants. The aim of the proposed approach is to enhance resource conservation by utilizing waste flares and vents to produce power and heat while reducing the negative environmental impact associated with discharging these streams into the atmosphere. A nonlinear optimization model is proposed to determine the optimal design of the cogeneration system that maximizes the net profit of the system. The model addresses the inevitable uncertainties associated with the abnormal situations leading to venting and flaring. A random generations approach based on historical data and a computationally efficient algorithm are introduced to facilitate design under uncertainty and to enable the assessment of different scenarios and solutions with various levels of risk. A case study is presented to show the applicability of the proposed model and the feasibility of using cogeneration systems to mitigate flaring and venting and to reduce the environmental impact and operating costs.
The paper demonstrates the profiles of electricity consumption in the low energy housing sector using various time frames, and provides a solid basis for energy estimation by analysing actual 12 month electricity data from 60 comprehensively monitored low energy houses in Australia's leading sustainable green village (Lochiel Park), located in South Australia. The results highlight that although considerable electricity reduction is achieved in low energy houses, the outdoor ambient air temperature is still a highly influential factor that determines the total and peak demand in these houses. It also suggests that energy estimation should focus on residents’ basic life style and appliance usage behaviour. The results presented here can be used to refine end-use electricity demand modelling for low energy houses in South Australia, and can hence assist the design of electrical infrastructure requirements in new low energy housing developments.
High resolution multi-energy model (electricity, heat, gas) for domestic dwellings.•Space heating, domestic hot water, cooking, and electrical appliances sub-models.•Accurate assessment of heating system and dwelling thermal inertia.•Various market/network relevant model applications demonstrated.
The paper deals with risk analysis and management in the realisation of process plants by engineering and contracting companies. Specifically, a new analytical methodology is developed to manage the typical risks of plant commissioning. Following a detailed study of the commissioning process and its criticalities, Hazop is selected as the most suitable approach in forecasting particular risks of this project stage. Starting from the limitations of both Hazop and Human Hazop (the extension of the technique to the field of procedures performed by humans), a new technique (Multilevel Hazop) is suggested which identifies in advance all the criticalities of each commissioning activity and defines actions to reduce risk and optimise dedicated resources. After implementation of Multilevel Hazop in a real commissioning process, a new version of the technique (Two Stage Multilevel Hazop) is proposed. This allows a significant reduction in implementation costs, justifying use of the technique both in innovative or critical cases, where the expected saving from risk reduction is high, and in general contexts.
(Graph Presented) This paper presents a methodology based on multi-objective optimization techniques for designing residential cogeneration systems. There is proposed an integrated system to provide hot water and electricity for domestic use in a residential complex. The accounted objective functions are the minimization of the total annual cost and the generated greenhouse gas emissions. As optimization decisions are considered the operating regime and sizing of the central generation power equipment (in this case, an internal combustion engine) and the thermal storage tank. The model takes into account the time variation of the energy demands, different rates of purchase - sale of electricity and seasonal temperature changes. Two different residential complexes from Mexico with different weather and energy demands were considered as case studies. Significant economic and environmental benefits were identified by applying the proposed methodology.
One of the largest user of electricity in the average U.S. household is appliances, which when aggregated, account for approximately 30% of electricity used in the residential building sector. As influencing the time-of-use of energy becomes increasingly important to control the stress on today's electrical grid infrastructure, understanding when appliances use energy and what causes variation in their use are of great importance. However, there is limited appliance-specific data available to understand their use patterns. This study provides daily energy use profiles of four major household appliances: refrigerator, clothes washer, clothes dryer, and dishwasher, through analyzing disaggregated energy use data collected for 40 single family homes in Austin, TX. The results show that when compared to those assumed in current energy simulation software for residential buildings, the averaged appliance load profiles have similar daily distributions. Refrigerators showed the most constant and consistent use. However, the three user-dependent appliances, appliances which depend on users to initiate use, varied more greatly between houses and by time-of-day. During peak use times, on weekends, and in homes with household members working at home, the daily use profiles of appliances were less consistent.
A test campaign was carried out to generate renewable hydrogen based on wood gas derived from the commercial biomass steam gasification plant in Oberwart, Austria. The implemented process consisted of four operation units: (I) catalyzed water–gas shift (WGS) reaction, (II) gas drying and cleaning in a wet scrubber, (III) hydrogen purification by pressure swing adsorption, and (IV) use of the generated biohydrogen (BioH2) in a proton exchange membrane (PEM) fuel cell. For almost 250 h, a reliable and continuous operation was achieved. A total of 560 (Ln dry basis (db))/h of wood gas were extracted to produce 280 (Ln db)/h of BioH2 with a purity of 99.97 vol %db. The catalyzed WGS reaction enabled a hydrogen recovery of 128% (ṅBioH2)/(ṅH2,wood gas) over the whole process chain. An extensive chemical analysis of the main gas components and trace components (sulfur, CxHy, and ammonia) was carried out. No PEM fuel cell poisons were measured in the generated BioH2. The only detectable impurities in the product were 0.02 vol %db of O2 and 0.01 vol %db of N2.Keywords: Biohydrogen; Biomass; Gasification; Product gas; Water−gas shift; Gas scrubbing; Pressure swing adsorption; Latex
In this work, the life cycle economic and environmental optimization of shale gas supply chain network design and operations is addressed. The proposed model covers the well-to-wire life cycle of electricity generated from shale gas, consisting of a number of stages including freshwater acquisition, shale well drilling, hydraulic fracturing and completion, shale gas production, wastewater management, shale gas processing, electricity generation as well as transportation and storage. A functional-unit based life cycle optimization problem for a cooperative shale gas supply chain is formulated as a multi-objective non-convex mixed-integer nonlinear programming (MINLP) problem. The resulting Pareto-optimal frontier reveals the trade-off between the economic and environmental objectives. A case study based on Marcellus shale play shows that the greenhouse gas emission of electricity generated from shale gas ranges from 433 to 499kg CO2e/MWh, and the levelized cost of electricity ranges from 91/MWh. A global optimization algorithm is also presented to improve computational efficiency.
Industrial facilities impacting a watershed may be clustered into groups based on their geographical locations. Water usage and discharge for each clustered group of industries may be integrated through the introduction of an eco-industrial park (EIP). This paper presents a mathematical programming model for water integration of EIPs to be synthesized with the purpose of mitigating the environmental impact of industrial effluents discharged into watersheds. The model considers the creation of multiple EIPs, their location, sizing, and tasks. To determine the effect of the discharges on the surrounding watershed, a material flow analysis (MFA) model was coupled with water recycle strategies within the industrial facilities and the associated EIPs. The MFA characterizes the interaction of individual discharges and tracks the impact of the natural (physical, chemical, and biological) phenomena within the watershed on the fate and transport of pollutants. A multi-objective optimization formulation is developed to guide the decisions for multi-plant water integration while accounting for the impact on the watershed. The objective function reconciles the minimization of the environmental impact on the watershed, the minimization of the total annualized cost of the water-management system which includes the cost of fresh water, effluent treatment, and piping and pumping associated with the eco-industrial parks. An example is presented to show the scope and capabilities of the proposed optimization approach.
This paper presents a multi-objective optimization approach for designing residential cogeneration systems based on a new superstructure that allows satisfying the demands of hot water and electricity at the minimum cost and the minimum environmental impact. The optimization involves the selection of technologies, size of required units and operating modes of equipment. Two residential complexes in different cities of the State of Michoacán in Mexico were considered as case studies. One is located on the west coast and the other one is in the mountainous area. The results show that the implementation of the proposed optimization method yields significant economic and environmental benefits due to the simultaneous reduction in the total annual cost and overall greenhouse gas emissions.
The combination of an automatic HAZOP analysis with a structural model was introduced to obtain a systematic procedure for hazard and mal-operations identification. There are three stages of the proposed procedure. The first stage was used to analyze the conventional hazard and mal-operations for each process unit, whereas the second stage extended the analysis to adjacent units. The interaction style was used to identify the cause-consequence relationships between upstream and downstream unit with the concepts of the non-local path and the dummy parameters. Therefore, a generic HAZOP library will be additional modified. The third stage created the templates for hazard and mal-operations identification for operating arbitrary units. This proposed HAZOP analysis was verified with conventional HAZOP of the defatted soy flour pilot plant with three scenarios. The analysis scheme fulfilled the library of the case study and discovered 18 new consequences for the first scenario, 10 new consequences for the second scenario. For the third scenario, the analysis specified on an arbitrary flash drum by applying three guide-words (more, less and no) and found 46 causes and 83 consequences. The proposed methodology, therefore, can simplify and reveal the guidance for hazards and mal-operations identification.
Energy security has been an actively studied area in recent years. Various facets have been covered in the literature. Based on a survey of 104 studies from 2001 to June 2014, this paper reports the findings on the following: energy security definitions, changes in the themes of these definitions, energy security indexes, specific focused areas and methodological issues in the construction of these indexes, and energy security in the wider context of national energy policy. It is found that the definition of energy security is contextual and dynamic in nature. The scope of energy security has also expanded, with a growing emphasis on dimensions such as environmental sustainability and energy efficiency. Significant differences among studies are observed in the way in which energy security indexes are framed and constructed. These variations introduce challenges in comparing the findings among studies. Based on these findings, recommendations on studying energy security and the construction of energy security indexes are presented.
The high penetration of distributed generators, most of them based on renewable energy sources, is modifying the traditional structure of the electric distribution grid. If the power of distributed generators is high enough to feed the loads of a certain area, this area could be disconnected from the main grid and operate in islanded mode. Microgrids are composed by distributed generators, energy storage devices, intelligent circuit breakers and local loads. In this paper, a review of the main microgrid architectures proposed in the literature has been carried out. The microgrid architectures are first classified regarding their AC or DC distribution buses. Besides, more complex microgrid architectures are shown. Both advantages and disadvantages of each one of the microgrid families are discussed.
Legionella pneumophila is frequently detected in hot water distribution systems and thermal control is a common measure implemented by health care facilities. A risk assessment based on water temperature profiling and temperature distribution within the network is proposed, to guide effective monitoring strategies and allow the identification of high risk areas. Temperature and heat loss at control points (water heater, recirculation, representative points-of-use) were monitored in various sections of five health care facilities hot water distribution systems and results used to develop a temperature-based risk assessment tool. Detailed investigations show that defective return valves in faucets can cause widespread temperature losses because of hot and cold water mixing. Systems in which water temperature coming out of the water heaters was kept consistently above 60 °C and maintained above 55 °C across the network were negative for Legionella by culture or qPCR. For systems not meeting these temperature criteria, risk areas for L. pneumophila were identified using temperature profiling and system's characterization; higher risk was confirmed by more frequent microbiological detection by culture and qPCR. Results confirmed that maintaining sufficiently high temperatures within hot water distribution systems suppressed L. pneumophila culturability. However, the risk remains as shown by the persistence of L. pneumophila by qPCR.
HAZOP (Hazard and Operability) studies began about 40 years ago, when the Process Industry and complexity of its operations start to massively grow in different parts of the world. HAZOP has been successfully applied in Process Systems hazard identification by operators, design engineers and consulting firms. Nevertheless, after a few decades since its first applications, HAZOP studies are not truly standard in worldwide industrial practice. It is common to find differences in its execution and results format. The aim of this paper is to show that in the Mexican case at National level in the oil and gas industry, there exist an explicit acceptance risk criteria, thus impacting the risk scenarios prioritizing process. Although HAZOP studies in the Mexican oil & gas industry, based on PEMEX corporate standard has precise acceptance criteria, it is not a significant difference in HAZOP applied elsewhere, but has the advantage of being fully transparent in terms of what a local industry is willing to accept as the level of risk acceptance criteria, also helps to gain an understanding of the degree of HAZOP applications in the Mexican oil & gas sector. Contrary to this in HAZOP ISO standard, risk acceptance criteria is not specified and it only mentions that HAZOP can consider scenarios ranking. The paper concludes indicating major implications of risk ranking in HAZOP, whether before or after safeguards identification.
Distributed energy resources (DER) are emerging rapidly. New engineering technologies, materials, and designs improve the performance and extend the range of locations for DER. In contrast, constructing new or modernizing existing high voltage transmission lines for centralized generation are expensive and challenging. In addition, customer demand for reliability has increased and concerns about climate change have created a pull for swift renewable energy penetration. In this context, DER policy makers, developers, and users are interested in determining which energy technologies to use to accommodate different end-use energy demands. In this paper, we present a two-stage multi-objective stiategic technology-policy framework for determining the optimal energy technology allocation for DER. The framework simultaneously considers economic, technical, and environmental objectives. The first stage utilizes a production frontier estimation model for each end-use to evaluate the performance of each energy technology based on the three objectives. The second stage incorporates factor efficiencies determined in the first stage, capacity limitations, dispatchability, and renewable penetration for each technology, and demand for each end-use into a bottleneck multi-criteria decision model which provides the Pareto-optimal energy resource allocation. For demonstration purposes, we apply the framework to a dataset constructed for a typical commercial building located in the Northeastern United States and discuss the results.
This paper presents a review on combined cooling, heating, and power (CCHP) systems. This work summarizes the methods used to perform energetic and exergetic analyses, system optimization, performance improvement studies, and development and analysis of CCHP systems, as reported in existing literature. In addition, this work highlights the most current research and emerging trends in CCHP technologies. It is envisioned that the information collected in this review paper will be a valuable source of information, for researchers, designers, and engineers, and provides direction and guidance for future research in CCHP technology.
Embedding the concept of sustainability into a company’s culture is immensely challenging but is likely to be critical to the long-term viability of science and technology companies that rely on successful innovation to remain competitive. Moving to a more sustainable society can be expected to provide plenty of commercially attractive business opportunities for forward thinking organizations. The combination of life cycle thinking with the enabling science of chemistry will be essential to successfully address world challenges such as the strain on resources caused by population growth and changing demographics. The Dow Chemical Company has been developing strategies and tools around holistic thinking for more than 20 years and has recently introduced a methodology to broaden sustainability knowledge and encourage life cycle thinking among innovators new to this topic while providing insight into the sustainability of new product development. A tool, the Dow Chemical Sustainability Footprint Tool, is described, using examples to illustrate the insights gained by project teams and business management. With more than 250 project assessments carried out so far, it is fair to say that sustainability knowledge among innovators is increasing, that the tool has met its design criteria such as being self-explanatory and easy and quick to use, and that it is providing business management with sustainability overviews of their project portfolios.
Achievable outcomes of the combined heat and power (CHP) system applications are subject to several factors. In this study the value of integrated system sizing and operational strategy selection has been evaluated. This would facilitate maximum return on investment as well as reducing primary energy resource consumption and environmental impact. The required model improvements are identified and applied, which will encompass the transient characteristics of the CHP system components and their true operational constraints in a more realistic manner. In addition, the proposed methodology is generic enough to cover energy demand fluctuations of any existing manufacturing plant by aggregated data integration to guarantee improved on-site energy generation system outcomes. Finally the proposed methodology is applied to a pharmaceutical manufacturing plant. The results illustrate promising potential improvements in comparison with existing approaches for CHP system configurations.
Significant reductions in anthropogenic greenhouse gas (GHG) emissions, particularly of fossil carbon dioxide (CO2), are necessary worldwide in order to prevent adverse impacts of global climate change on the socio-economic sectors, ecological systems, and human health. In this context, this study aims to investigate the economic and environmental aspects of sustainability associated with the integration of algal biodiesel production with a steam electric power plant for microalgae biofixation of CO2 in flue gases and then algal biomass conversion to biodiesel. This integrated energy system is a multipurpose process that provides the CO2 required by the microalgae cultures as well as electricity, biodiesel produced from the algal biomass, and lipid-depleted biomass which is in turn used as an auxiliary fuel in the power plant. A multi-objective optimization strategy based on genetic algorithms is proposed to yield a set of optimal solutions providing the best compromise between the profit and the environmental impact of regenerative Rankine power generation plants coupled with algae-to-biodiesel production facilities. The power plant operates continuously, but CO2 is fed to open pond raceways only during the daytime (12 h a day) for algae growth. The rigorous IAPWS-IF97 formulation is used to calculate the thermodynamic properties of water and steam in the steam power cycle. The environmental impact is measured by the Eco-indicator 99 methodology that follows LCA principles. The optimization problem includes the selection of multiple primary energy sources for the power plant boiler, such as fossil fuels (coal, oil, and natural gas), biofuels, and biomass (switchgrass, softwood, and hardwood) in order to achieve significant reductions of CO2 emissions. The optimal trade-off designs are obtained by implementing the ε-constraint method. The optimization method has been applied to a case study in México. The Pareto optimal solutions indicate that the current price for biodiesel of $3.91/gal on average would make the integrated energy system under consideration profitable. In addition, the system could achieve significant environmental improvements due to life-cycle GHG reductions that result not only from biofixation of CO2 from combustion flue gases by microalgae and then algal biomass conversion and use as renewable fuels (i.e., biodiesel and lipid-depleted biomass) that substitute for fossil fuels, but also by significantly reducing the fossil fuel requirement compared to stand-alone coal-fired power plants.
Traditional inventory models involve different decisions that attempt to optimize material lot sizes by minimizing total annual supply chain costs. However, the increasing concern on environmental issues stresses the need to treat inventory management decisions as a whole, by integrating economic and environmental objectives. Recent studies have underlined the need to incorporate additional criteria in traditional inventory models in order to design “responsible inventory systems”. This paper explores the integration of factors affecting the environmental impact within the traditional EOQ model and proposes a “Sustainable EOQ Model”. All sustainability factors linked to the material lot size are analyzed from the beginning of the purchasing order to the end of its life inside the buyer plant. Thus, the environmental impact of transportation and inventory is incorporated in the model and investigated by an economic point of view. In particular internal and external transportation costs, vendor and supplier location and the different freight vehicle utilization ratio are considered in order to provide an easy-to-use methodology. The optimization approach is applied to representative data from industrial problems to assess the impact of sustainability considerations on purchasing decisions if compared with the traditional approaches. Finally, an illustration of the effect of using the new “Sustainable EOQ model” is presented and discussed.
The aim of this paper is the evaluation of the profitability of micro-CHP systems for residential application. An integrated CHP system composed of a prime mover, an Electric Energy Storage system, a thermal storage system and an auxiliary boiler has been considered. The study has been carried out taking into account a particular electrochemical storage system which requires also thermal energy, during its operation, for a better exploitation of the residual heat discharged by the prime mover. The prime mover could be a conventional Internal Combustion Engine or also an innovative system, such as fuel cell or organic Rankine cycle. An investigation of this integrated CHP system has been carried out, by means of an in-house developed calculation code, performing a thermo-economic analysis. This paper provides useful results, in order to define the optimum sizing of components of the integrated CHP system under investigation: the developed code allows also to evaluate the profitability and the primary energy saving with respect to the separate production of electricity and heat.
A distributed energy system refers to an energy system where energy production is close to end use, typically relying on small-scale energy distributed technologies. It is a multi-input and multi-output energy system with substantial energy, economic and environmental benefits. However, distributed energy systems such as micro-grids in residential applications may not be able to produce the potential benefits due to lack of appropriate system configurations and suitable operation strategies. The optimal design, scheduling and control of such a complex system are of great importance towards their successful practical realization in real application studies. This paper presents a short review and an energy systems engineering approach to the modeling and optimization of micro-grids for residential applications, offering a clear vision of the latest research advances in this field. Challenges and prospects of the modeling and optimization of such distributed energy systems are also highlighted in this work.
Cogeneration technologies are increasingly being utilised in the construction sector. Micro-cogeneration technologies only become economically feasible after they have been in operation over a lengthy period of time and this makes necessary the sizing of appropriate storage systems. The integration of cogeneration within overall heating and cooling loads requires the use of complicated simulation codes. However the need for this integration can be removed with the design of a cogeneration system which only covers the thermal demand required for the provision of domestic hot water, this demand being relatively easy to forecast. Based on a given domestic hot water demand, a calculation procedure for sizing the storage system is presented. This procedure is experimentally validated with only minor differences between expected and actual results, this being attributable to the limitations of the experimental set-up. It achieves more than acceptable results when compared with other model designed for heating applications in the building sector.
Decentralised energy in the UK is rare. Cities in the north of England however lead the UK in terms of sustainable, low-carbon, local/district heating, through the implementation of combined-heat-and-power (CHP) facilities; substantial schemes are installed in several cities, including Barnsley and Sheffield. This paper presents the results from extensive experimental and theoretical feasibility studies, in which the merits of these were explored. Barnsley has a number of biomass-fuelled community energy generators, where pollutant monitoring and mathematical modelling were conducted to assess combustion characteristics and overall system performance. Measured pollutant levels were within the relative emission limits, though emission concentrations (CO, CO2, NO and particles) in the flue gas from the coal boiler were higher than the wood pellet boiler. Sheffield already has a citywide district energy network, centred around a sustainably-sourced waste-to-energy facility; an expansion of this scheme was investigated here. This focuses mainly on the link to a 30 MW wood-fired CHP plant, which could be a significant provider of additional thermal capacity (low-grade heat) to an expanded network. Through identifying heat sources and sinks – potential suppliers and end-users – key areas were identified where a connection to the heat network would be feasible.
Many European states support Combined Heat and Power (CHP) investments and provide better selling tariffs for the electricity produced. In this paper, a model was developed that can help energy planning and decision-making for CHP investments in an unstable energy market. The model uses as variables state subsidies, natural gas and electricity selling price. Five different scenarios from Greek economic reality had been used in order to evaluate their economic viability and the investment risk. Finally, a sensitivity analysis was carried out, having as variables the natural gas price and the State subsidy. The sensitivity analysis of the natural gas price showed that although profits decrease as natural gas price increases, the investment remains viable for almost twice the current natural gas price. This means that small fluctuations of natural gas price do not affect the investment to a crucial degree.
Passive fire protection by the application of fireproofing materials is a crucial safety barrier in the prevention of the escalation of fire scenarios. Fireproofing improves the capacity of process items and of support structures to maintain their structural integrity during a fire, preventing or at least delaying the collapse of structural elements. Maintenance and cost issues require, however, to apply such protection only where an actual risk of severe fire scenarios is present. Available methodologies for fireproofing application in on-shore installation do not consider the effect of jet-fires. In the present study, a risk-based methodology aimed at the protection from both pool fire and jet fire escalation was developed. The procedure addresses both the prevention of domino effect and the mitigation of asset damage due to the primary fire scenario. The method is mainly oriented to early design application, allowing the identification of fireproofing zones in the initial phases of lay-out definition.
Water hyacinth causes severe ecological problems in the infested water bodies. Several strategies have been proposed to eliminate this plant. Nevertheless, most of them have not been economically attractive. This paper proposes a general superstructure and a mathematical programming model for the sustainable elimination of water hyacinth through a distributed biorefining network. The proposed model optimizes the selection of the products, the siting and sizing for the processing facilities, and the selection of the markets, while accounting for technical and economic constraints. A case study for the central part of Mexico, where water hyacinth is a serious problem, is used to show the applicability of the proposed holistic approach. The results show that an optimally synthesized distributed biorefining network is capable of sustainable and economic elimination of water hyacinth from contaminated water bodies while generating value. Additionally, the results shown through Pareto curves allow the identification of a set of optimal solutions featuring trade-offs between economic and environmental objectives.
A project was performed for the Explosion Research Cooperative to develop algorithms for predicting the frequencies of explosions based on a variety of design, operating and environmental conditions. Algorithms were developed for estimating unit-based explosion frequencies, such as those reported in API Recommended Practice 752, but in more detail and covering a much broader range of chemical process types. The project also developed methods for predicting scenario-based explosion frequencies, using frequencies of initiating events and conditional probabilities of immediate ignition and delayed ignition resulting in explosion. The algorithms were based on a combination of published data and expert opinion.
Nuclear energy cannot be avoided in the near future. To regain public acceptance the safety of nuclear power plants has to be increased. Consequently, feasibility studies have been carried out for a containment proposal for future pressurized water reactors which will keep people unharmed even in the case of severe nuclear accidents under the assumption “all that can go wrong, will go wrong”. The main features of the design concept are a core melt cooling and retention device, a passively acting cooling system to remove the decay heat and a double-wall containment which is able to withstand high static and dynamic internal pressures due to hydrogen detonation. Internal structures are designed to resist extreme loadings resulting from various accident scenarios including in-vessel steam explosion and vessel failure under high system pressure.
The process area of an offshore oil and gas platform is very compact with a high degree of congestion and confinement due to space limitations and environmental conditions. Although there are safety systems installed on the platforms, the process area is never completely safe. Among the loss producing events, fires and explosions are the most frequently reported process related accidents. They have potential to cause serious injury to personnel, major damage to equipment and structure, and disruption of operations. It is therefore necessary to perform a fire and explosion hazard analysis as a basis for the implementation of appropriate mitigation measures and emergency response plans to protect personnel.
In this paper, we reviewed the existing consequence models, such as source models, dispersion models, ignition models, fire and explosion models, and selected the ones most suitable for offshore conditions. These models were then used to perform a consequence assessment for an offshore platform by simulating four different scenarios. Two main revisions were incorporated: (1) a grid-based approach was adopted to enable better consequence/impact modelling and analysis of radiation and blast overpressures, and (2) an enhanced onsite ignition model was integrated in the consequence assessment process to obtain better results.
In this work, a novel approach is proposed for expressing the risks of process plants consisting of a large number of scenarios, in the form of a risk metrics of leading indicators to prevent potential high profile industry accidents. The methodology includes: 1) risk estimation of a portfolio by CPQRA (or QRA), 2) monetization of the tangible risks with the inclusion of the lost time of production, 3) estimation of the maximum portfolio loss using Value-at-Risk approach, 4) inclusion of intangible risks using FN-curve and, 5) generation of F$-curve of tangible risks. The proposed methodology can particularly help in understanding the stakes at risk by performing the overall cost-benefit analysis, for identifying the most risky scenarios and identifying critical equipments to enable better risk-informed decision making in order to adopt appropriate risk mitigation measures. This work establishes the groundwork for developing measures for understanding and comparing the large number of risk values derived from QRA studies for large portfolios. It will aid in less subjective decision making as it enables the decision maker to choose the most preferred portfolio option among alternatives. Decisions made with the accurate understanding of the consequences of risks can significantly reduce potential work-related fatalities, property losses and save millions of dollars.
This paper first addresses the definition of various objectives involved in eco-efficient processes, taking simultaneously into account ecological and economic considerations. The environmental aspect at the preliminary design phase of chemical processes is quantified by using a set of metrics or indicators following the guidelines of sustainability concepts proposed by IChemE (2001). The resulting multiobjective problem is solved by a genetic algorithm following an improved variant of the so-called NSGA II algorithm. A key point for evaluating environmental burdens is the use of the package ARIANE™, a decision support tool dedicated to the management of plants utilities (steam, electricity, hot water, etc.) and pollutants (CO2, SO2, NO, etc.), implemented here both to compute the primary energy requirements of the process and to quantify its pollutant emissions. The well-known benchmark process for hydrodealkylation (HDA) of toluene to produce benzene, revisited here in a multiobjective optimization way, is used to illustrate the approach for finding eco-friendly and cost-effective designs. Preliminary biobjective studies are carried out for eliminating redundant environmental objectives. The trade-off between economic and environmental objectives is illustrated through Pareto curves. In order to aid decision making among the various alternatives that can be generated after this step, a synthetic evaluation method, based on the so-called Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) (Opricovic & Tzeng, 2004), has been first used. Another simple procedure named FUCA has also been implemented and shown its efficiency vs. TOPSIS. Two scenarios are studied; in the former, the goal is to find the best trade-off between economic and ecological aspects while the latter case aims at defining the best compromise between economic and more strict environmental impacts.
Increasing scarcity of fossil fuels makes the deployment of hydrogen in combination with renewable energy sources, nuclear energy or the utilization of electricity from full time operation of existing power stations an interesting alternative. A pre-requisite is, however, that the safety of the required infrastructure is investigated and that its design is made such that the associated risk is at least not higher than that of existing supplies. Therefore, a risk analysis considering its most important objects such as storage tanks, filling stations, vehicles as well as heating and electricity supplies for residential buildings was carried out. The latter are considered as representative of the entire infrastructure. The study is based on fault and event tree analyses, wherever required, and consequence calculations using the PHAST code. The procedure for evaluating the risk and corresponding results are presented taking one of the objects as an example.
In this paper, various aspects of trigeneration power plants including advantages, challenges and criteria for high efficiency operation are discussed. In trigeneration systems, prime movers are treated to be the heart of the plant and thus an appropriate selection is crucial for successful operation. A comparative analysis of potential prime movers, together with a comprehensive literature review used in trigeneration and, their selection criteria are presented. A case study of a trigeneration plant based on solid oxide fuel cells and an organic Rankine cycle is examined using thermodynamic analysis. This thermodynamic analysis includes performance assessment of the system through energy and exergy efficiencies. An environmental impact assessment is also conducted based on CO2 emissions as a measure. The present study reveals that compared to power cycle efficiency (considering net electrical efficiency), there is a minimum potential of 22% gain in efficiency when trigeneration is used. Also, it is shown that there is more than 200 kg MWh−1 reduction in CO2 emissions when trigeneration is used compared to the case where a power cycle is only used. Copyright © 2010 John Wiley & Sons, Ltd.
Distributed generation is being deployed at increasing levels of penetration on electricity grids worldwide. It can have positive impacts on the network, but also negative impacts if integration is not properly managed. This is especially true of photovoltaics, in part because it's output fluctuates significantly and in part because it is being rapidly deployed in many countries. Potential positive impacts on grid operation can include reduced network flows and hence reduced losses and voltage drops. Potential negative impacts at high penetrations include voltage fluctuations, voltage rise and reverse power flow, power fluctuations, power factor changes, frequency regulation and harmonics, unintentional islanding, fault currents and grounding issues. This paper firstly reviews each of these impacts in detail, along with the current technical approaches available to address them. The second section of this paper discusses key non-technical factors, such as appropriate policies and institutional frameworks, which are essential to effectively coordinate the development and deployment of the different technical solutions most appropriate for particular jurisdictions. These frameworks will be different for different jurisdictions, and so no single approach will be appropriate worldwide.
The current subsidized energy prices in Iran are proposed to be gradually eliminated over the next few years. The objective of this study is to examine the effects of current and future energy price policies on optimal configuration of combined heat and power (CHP) and combined cooling, heating, and power (CCHP) systems in Iran, under the conditions of selling and not-selling electricity to utility. The particle swarm optimization algorithm is used for minimizing the cost function for owning and operating various CHP and CCHP systems in an industrial dairy unit. The results show that with the estimated future unsubsidized utility prices, CHP and CCHP systems operating with reciprocating engine prime mover have total costs of 5.6 and $2.9x106 over useful life of 20 years, respectively, while both systems have the same capital recovery periods of 1.3 years. However, for the same prime mover and with current subsidized prices, CHP and CCHP systems require 4.9 and 5.2 years for capital recovery, respectively. It is concluded that the current energy price policies hinder the promotion of installing CHP and CCHP systems and, the policy of selling electricity to utility as well as eliminating subsidies are prerequisites to successful widespread utilization of such systems.
Analysis of combined cooling, heating, and power (CCHP) systems is frequently based on reduction of operating cost without measuring the actual energy use and emissions reduction. CCHP systems can be optimized based on different optimization criterion such as: energy savings, operation cost reduction or minimum environmental impact. In this study, CCHP systems operated following the electric load (FEL) and the thermal load (FTL) strategies are evaluated and optimized based on: primary energy consumption (PEC), operation cost, and carbon dioxide emissions (CDE). This study also includes the analysis and evaluation of an optimized operational strategy in which a CCHP system follows a hybrid electric–thermal load (HETS) during its operation. Results show that CCHP systems operating using any of the optimization criteria have better performance than CCHP systems operating without any optimization criteria. For the evaluated city, the optimum PEC and cost reduction are 7.5% and 4.4%, respectively, for CCHP-FTL, while the optimum CDE reduction is 14.8% for CCHP-FEL. Results also show that the HETS is a good alternative for CCHP systems operation since it gives good reduction of PEC, cost, and CDE. This optimized operation strategy provides a good balance among all the variables considered in this paper.
Inherently safer product, process and plant design represents a fundamentally different approach to safety in chemical manufacturing. The process designer is challenged to identify ways to eliminate the hazards associated with the process, rather than to develop add-on barriers to protect people from the hazards of the manufacturing process and its materials. This is best accomplished early in the product and process design cycle, but it is never too late to apply inherently safer design concepts. However, the process designer must also recognize that most processes have many hazards, and must always retain a broad perspective when evaluating options. Design alternatives which reduce or eliminate one hazard may create or increase the magnitude of others. The designer must apply good judgment and appropriate analytical and decision making tools to allow him to select the best overall process alternative, considering all of the hazards.
A new method called SREST-layer-assessment method with automated software tool is presented that in a hierarchical approach reveals the degree of non-ideality of chemical processes with regard to SHE (safety, health and environment) aspects at different layers: the properties of the chemical substances involved (substance assessment layer (SAL)), possible interactions between the substances (reactivity assessment layer (RAL)), possible hazard scenarios resulting from the combination of substances and operating conditions in the various equipments involved (equipment assessment layer (EAL)), and the safety technologies that are required to run a process safely and in accordance with legal regulations (safety-technology assessment layer (STAL)). In RAL, EAL and STAL the main focus is put on process safety. A case study is used to show the principles of the method. It is demonstrated how the method can be used as a systematic tool to support chemical engineers and chemists in evaluating chemical process safety in early process development stages.
The twin challenges of a lower-carbon future and national energy security are focusing attention on the most effective means of energy generation in the built environment. Efficiency gains are offered by the distribution of heat from community heating and combined heat and power (CHP) plant, which is presently underdeveloped in the UK by comparison with continental Europe. Natural gas is the preferred fuel for most of today's district energy systems which are technically developed, but proposed schemes must be tested against CHP ‘quality’ criteria to ensure there is not an increase in primary energy use compared to larger-scale central generation. Future district energy systems must aim to exploit local energy resources, such as biomass, wind and micro-hydro, and local thermal resources, such as solar collectors and ground source heat pumping. They may also incorporate novel forms of heat and power storage and load management.District energy schemes must be planned within a context of increasingly efficient buildings requiring less heat while the demand for electricity increases. In addition, local power schemes will have to meet future environmental requirements, for example for air quality where waste or biomass is combusted.
This paper investigates the relevance of external determinants for the adoption of stationary fuel cells (FCs) by different user groups with respect to the marketability of this innovative technology. FCs allow electricity and heat to be decentrally generated in an energy-efficient and potentially environmentally friendly manner. European energy policy is undertaking efforts to increase the proportion of combined heat and power (CHP) plants. A series of studies have spoken of their considerable market potential. A qualitative study was conducted with six focus groups consisting of 49 commercial users and six focus groups with 54 private consumers. The results of the study show that the specific infrastructure required for decentralisation and policy issues are highly relevant for the user adoption of FCs. Security of supply when energy generation is more strongly decentralised, reliable maintenance of the system, and clear political objectives are examples of factors that are considered essential prerequisites for the adoption of this technology.
A review is carried out on the development of small- and micro-scale biomass-fuelled combined heat and power (CHP) systems. Discussions have been concentrated on the current application of Organic Rankine Cycle (ORC) in small- and micro-scale biomass-fuelled CHP systems. Comparisons have been made between ORC and other technologies such as biomass gasification and micro-turbine based biomass-fuelled CHP systems. The advantages and disadvantages of each technology have been discussed. Recommendations have been made on the future development of small- and micro-scale biomass-fuelled CHP.
Inherent safety is a proactive approach for hazard/risk management during process plant design and operation. It has been proven that, considering the lifetime costs of a process and its operation, an inherently safer approach is a cost-optimal option. Inherent safety can be incorporated at any stage of design and operation; however, its application at the earliest possible stages of process design (such as process selection and conceptual design) yields the best results.Although it is an attractive and cost-effective approach to hazard/risk management, inherent safety has not been used as widely as other techniques such as HAZOP and quantitative risk assessment. There are many reasons responsible for this; key among them are a lack of awareness and the non-availability of a systematic methodology and tools.The inherent safety approach is the best option for hazard/risk management in offshore oil and gas activities. In the past, it has been applied to several aspects of offshore process design and operation. However, its use is still limited. This article attempts to present a complete picture of inherent safety application in offshore oil and gas activities. It discuses the use of available technology for implementation of inherent safety principles in various offshore activities, both current and planned for the future.
During economic doldrums, decision making on investments for safety is even more difficult than it already is when funds are abundant. This paper attempts to offer some guidance. After stating the present challenge to prevention of losses in the process industries, the systematic approach of quantified risk assessment is briefly reviewed and improvements in the methodology are mentioned. In addition, attention is given to the use of a risk matrix to survey a plant and to derive a plan of action. Subsequently, the reduction of risk is reviewed. Measures for prevention, protection, and mitigation are discussed. The organization of safety has become at least as important as technical safety of equipment and standards. It is reflected in the introduction of a safety management system. Furthermore, the design process in a pro-active approach is described and the concept of inherent safety is briefly addressed. The concept of Layer of Protection Analysis is explained and also the reason why it is relevant to provide a cost-benefit analysis. Finally, after comments regarding the cost of accidents, the basics of costing and profitability are summarized and a way is suggested to apply this approach to risk-reducing measures. An example is provided on how a selection can be made from a number of alternatives.
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