Optimal lay-out and operation of combined heat & power (CHP) distributed generation systems

The paper presents an optimization model of a distributed cogeneration system with a district heating network, applied to a real city centre situation. The distributed urban cogeneration system includes both a set of micro-gas turbines, located inside some public buildings, and a centralized cogeneration system based on a Internal Combustion Engine. The objective function adopted for the optimization is the Total Annual Cost for owning, maintaining and operating the whole system. To face the problem a Mixed Integer Linear Program (MILP) is defined and solved by a commercial software. Starting from the thermal and electrical demand of the buildings, the MILP model allows to define the possible installation of the centralized cogeneration ICE (Internal Combustion Engine) and the number of microturbines in the different buildings, the optimal lay-out of the district heating network and the optimal operation strategy for the whole system as well. In particular the energy performance and global CO₂ emissions are evaluated.     

Optimization Modeling for Sewer Network Management

Due to their low visibility, sanitary sewers' condition assessment and rehabilitation are frequently neglected until a catastrophic failure occurs. Neglecting regular maintenance of these underground utilities adds to life-cycle costs and liabilities, and in extreme cases causes stoppage or reduction of vital services. A systematic approach for the determination of deterioration of sewer systems and an integrated management system are necessary to fully understand the complete status of this underground infrastructure system. This paper discusses the major aspects of integrated management for sewer systems, namely, the development of network identification, sewer classification and sewer condition rating systems, sewer deterioration mechanisms, prediction modeling, and the use of optimization techniques for maximizing benefit∕cost ratios over a planning horizon. A case study, based on large combined sewers from the city of Indianapolis, has been used to demonstrate the use of the framework of this integrated life-cycle based sewer management system. Deterministic dynamic programming is employed to identify appropriate sewer rehabilitation techniques at different stages during the planning horizon adopted for the sewer systems.     

On the thermoeconomic approach to the diagnosis of energy system malfunctions: Part 2. Malfunction definitions and assessment

This paper goes further with the aim at demonstrating the capabilities of the thermoeconomic approach to the diagnosis of energy utility systems. This paper deals with a common vocabulary, definitions of concepts and mathematical principles, and above all, focuses on the concept of malfunction, starting from an engineering point of view and then shifting to a pure formalization as thermoeconomic parameters. Possible malfunctions of components of a combined cycle power plant are described in this part in terms of causes and effects. In addition, the main theoretical aspects of the thermoeconomic approach are shown. In particular the fuel impact formula, which constitutes the main thermoeconomic tool for quantifying the effects of degradation, is discussed.     

On the thermoeconomic approach to the diagnosis of energy system malfunctions: Part 1: the TADEUS problem

This work is the first part of a wider project aiming at demonstrating the capabilities offered by the thermoeconomic approach to the diagnosis of malfunctions in energy utility systems (TADEUS problem). The final goal is to create a common basis of work for people interested in applying thermoeconomics to identify malfunctions and to evaluate their effects on the overall plant performance. The main issues to be addressed when performing a diagnosis of energy system malfunctions using a thermoeconomic approach are summarized. A combined cycle power plant is proposed to demonstrate the practical feasibility of the thermoeconomic approach. An overview of its operation characteristics, thermodynamic design properties and control strategy is given in Part 1, and a comprehensive model is described for further use as common basis to illustrate the various diagnosis approaches either by the authors or third parties. Possible component malfunctions and main theoretical aspects of the thermoeconomic approach are presented in Part 2. The paper shows at which level of detail the analysis of physical and technical characteristics of the plant should be performed, how to develop a design and off-design model suitable for malfunction analysis, how to analyse and define component malfunctions and how to interpret and use thermoeconomic variables and indexes.