• Energy Research

Studies involving the design of interplant water networks have received significant attention over the past few years. Many methods have been developed to assist in obtaining efficient water reuse network design schemes, mainly using fundamental concepts of water integration. Our recent work has presented the importance of considering spatial constraints in the form of utility corridor availability, when identifying cost‐effective interplant water network arrangements in industrial zones (Alnouri et al., [2014]: Clean Technologies and Environmental Policy 16, 1637–1659). This article extends the scope of our previous work by enabling the identification of new corridor locations, which could potentially be used alongside existing utility infrastructure. We present an optimization framework that allows unutilized areas of land within industrial zones to be sectioned off and added as optional transportation channels, together with existing utility corridor regions, in the course of attaining cost‐effective interplant water network designs. The methodology entails that identification of optimal wastewater reuse schemes among various processing entities, by exploring options for enhanced utility corridors. As an illustration, several cases that utilize an assumed layout for an industrial zone have been carried out, in which a number of unutilized regions of land were identified to exist. Several opportunities that allow for potential corridor additions onto existing corridor infrastructure, through the exploitation of unutilized regions of land within the plot, were explored. A number of improvements in the water network designs obtained are highlighted for the different case scenarios that have been investigated, using the proposed approach. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1492–1511, 2016

Abstract The performance of ORC systems strongly depends on working fluid properties. We explore the relationships between working fluid properties and ORC common economic and thermodynamic performance criteria from a theoretical and an analytical point of view. The mapping of individual properties and performance criteria presented in this paper will provide a basis for the development of efficient and systematic strategies and approaches for ORC working fluid selection in future.

Abstract This work presents a systematic approach toward the design of Organic Rankine Cycles (ORC) for the generation of power from multiple heat sources available at different temperature levels. The design problem is approached in a mixed-integer non-linear programming (MINLP) formulation where an inclusive and flexible ORC model is automatically evolved by a deterministic algorithm for global optimization. The basic building block of the model is the ORC cascade which consists of a heat extraction, a power generation, a condensation and a liquid pressurization section. The aim of the optimization is to determine the optimum number of ORC cascades, the structure of the heat exchanger network shared among different cascades, the operating conditions and the working fluid used in each cascade in order to identify an overall ORC structure that maximizes the power output. The approach is illustrated through a case study which indicates that a system of two waste heat sources is best exploited through two interconnected ORC utilizing different working fluids.

This work presents a Computer-Aided Molecular Design (CAMD) method for the synthesis and selection of binary working fluid mixtures used in Organic Rankine Cycles (ORC). The method consists of two stages, initially seeking optimum mixture performance targets by designing molecules acting as the first component of the binaries. The identified targets are subsequently approached by designing the required matching molecules and selecting the optimum mixture concentration. A multiobjective formulation of the CAMD-optimization problem enables the identification of numerous mixture candidates, evaluated using an ORC process model in the course of molecular mixture design. A nonlinear sensitivity analysis method is employed to address model-related uncertainties in the mixture selection procedure. The proposed approach remains generic and independent of the considered mixture design application. Mixtures of high performance are identified simultaneously with their sensitivity characteristics regardless of the em...

This work adopts the ECCs (exergy composite curves) approach to explore the potential for ORC (organic Rankine cycle) process improvements. The method is used to explore different ORC configurations supported by a mathematical model representing a generic multi-pressure ORC cascade and developed based on the principles of the ECCs method. The model facilitates interconnectivity at different temperature and pressure levels, also considering two types of turbines, namely an expansion and an induction turbine. It is employed to investigate the performance of two major ORC configurations, namely one considering independent pressure loops with an expansion turbine and the other considering pressure loops contacted through induction turbines. These configurations are updated with new features within an iterative procedure supporting the systematic identification of the optimum number of pressure loops together with several operating optimization parameters. The optimization is performed using an inclusive objective function, while the obtained results indicate ORC systems of high performance.

Abstract This work investigates the performance of working fluid mixtures for use in solar ORC (Organic Rankine Cycle systems) with heat storage employing FPC (Flat Plate Collectors). Several mixtures are considered including conventional choices often utilized in ORC as well as novel mixtures previously designed using advanced computer aided molecular design methods (Papadopoulos et al., 2013). The impact of heat source variability on the ORC performance is assessed for different working fluid mixtures. Solar radiation is represented in detail through actual, hourly averaged data for an entire year. A multi-criteria mixture selection methodology unveils important trade-offs among several important system operating parameters and efficiently highlights optimum operating ranges. Such parameters include the ORC thermal efficiency, the net generated power, the volume ratio across the turbine, the mass flow rate of the ORC working fluid, the evaporator temperature glide, the temperature drop in the storage tank, the ORC total yearly operating duration, the required collector aperture area to generate 1 kW of power and the irreversibility. A mixture of neopentane – 2-fluoromethoxy-2-methylpropane at 70% neopentane is found to be the most efficient in all the considered criteria simultaneously.

This work presents the first approach to the systematic design and selection of optimal working fluids for Organic Rankine Cycles (ORCs) based on computer aided molecular design (CAMD) and process optimization techniques. The resulting methodology utilizes group contribution methods in combination with multi-objective optimization technology for the generation of optimum working fluid candidates. Optimum designs of the corresponding ORC processes are then developed for the comprehensive set of molecules obtained at the CAMD stage, in order to identify working fluids that exhibit optimum performance in ORCs with respect to important economic, operating, safety and environmental indicators. The proposed approach is illustrated with a case study in the design of working fluids for a low-temperature ORC system. Particular attention is paid to safety and environmental characteristics such as flammability, toxicity, ozone depletion and global warming potential. The methodology systematically identified both novel and conventional molecular structures that enable optimum ORC process performance.

In order to reduce the usage of fossil fuels in industrial sectors by meeting the requirements of production processes, new heat integration and heat recovery approaches are developed. The goal of this study is to develop an approach to increase energy efficiency of an industrial zone by recovering and reusing waste heat via indirect heat integration. Industrial zones usually consist of multiple independent plants, where each plant is supplied by an independent utility system, as a decentralized system. In this study, a new approach is developed to target minimum energy requirements where an industrial zone would be supplied by a centralized utility system instead of decentralized utility system. The approach assumes that all process plants in an industrial zone are linked through the central utility system. This method is formulated as a linear programming problem (LP). Moreover, the proposed method may be used for decision making related to energy integration strategy of an industrial zone. In addition, the proposed method was applied on a case study. The results revealed that saving of fossil fuel could be achieved.