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A new type of district energy network has recently been proposed that is based on the use of CO2 as a heat transfer fluid. It uses the latent heat of vaporization, instead of sensible heat, to store and transfer heat. Previous studies have focused on demon ...

This paper aims to illustrate a new holistic modeling environment through a case study implementing a district heating system to supply four groups of users identified in the city of Tokyo. The holistic modeling environment, called DOME (Distributed Object-based Modeling Environment) is being applied by researchers in the Alliance for Global Sustainability (AGS) to develop a platform for assessing technologies and policies with the intent to reduce significantly CO2 emissions in large cities. DOME is used a

As energy plays a central role in the world development, it represents as well a major challenge for sustainable development. Today, more than 80% of the primary energy consumption is based on fossil fuels and the share is likely to remain high in the future. Even if technology developments will reduce the specific consumption, the world energy demand is likely to increase in line with its population. Energy and material efficiency and the integration of the renewable resources will therefore have to play a

A new concept of small hybrid solar power system (HSPS) has been successfully demonstrated in the context of a project called SPS (Solar Power System). This plant integrates two rows of solar collectors, two superposed Organic Rankine Cycles (ORC) each equipped with a scroll hermetic expander-generator and a heat engine. In operation with solar energy only, the heat is supplied by a thermal fluid (presently pressurized water) heated in the vacuum insulated focal tubes of sun following, flat concentrators ma

The Swiss limit for NOx exhaust gas emissions from decentralised electrical power and heat cogeneration units using stationary I.C. engines operating on natural gas, despite a recent increase from 80 to 250 mg/mN3 (5% O2), remains the most severe in force in the world. The only technology currently able to meet this limit - the use of a stoichiometric mixture and a three-way catalyst - results in a relatively low global engine efficiency and suffers from a limited reliability of the exhaust gas treatment sy

Structural reliability is a hurdle for the large-scale commercialisation of solid oxide fuel cell (SOFC). The cells are prone to cracking, due to the brittleness of their constitutive materials. In operation, the failure of one of them can arise from the non-uniform temperature distribution, coupled to detrimental interaction with the other stack components. In the long-term, the uneven distribution of temperature, gas composition, current density or overpotential induces non-uniform creep deformation and m

Currently the herringbone grooved journal bearing (HGJB) has applications in the domain of small, low power energy related applications, where high rotational speeds are required for reaching reasonable efficiency and where standard oil lubricated bearings are limited or even unable to operate over the life time required. Furthermore the presence of oil requires auxiliary control systems reducing the overall system efficiency and reliability. High-speed rotors running in hermetic units processing refrigeran

After an experimental study of refrigerants HFC-134a, HCFC-123, HFC- 404A and HFC-407C, and considerable modifications to the test stand, LENI has undertaken a new experimental program and has assembled a large new database for evaporation of ammonia and two ammonia-oil mixtures (1% and 3% wt. oil) inside horizontal tubes with smooth and enhanced surfaces. This work extends the current database to include a refrigerant in which there is a marked renewal of interest. The comparison of the ammonia results wit

The project High Temperature Heat Pump has been completed in 2 phases. First a new type of scroll compressor with adapted injection port for vapor injection, was tested with an air-water heat pump (fig 2.2, 2.3). This type of heat pump reaches the extreme running conditions for the retrofit of existing fuel boilers at air (a) -12°C and water (W) 65°C with very satisfying performances (Final Report, Phase 1). In this report a second improved compressor could be tested: with a COP of 2.74 (was 2.58) at A2W50r

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depe ...

Among the structure independent approaches of process integration, pinch technology has been shown for continuous processes to be extremely powerful to develop energy efficient processes and enhance synergic effects within and between processes. The earlier focus of the method has mainly been concerned with a minimization of the heat transfer exergy losses based on a given economic criterion. However, there is a need to increasingly consider environmental and other life cycle aspects as early as possible in

The Laboratory of Industrial Energy systems has evaluated a series of high performance air-water heat pump concepts with the aim to retrofit existing fuel fired boilers for residential hydronic heating systems. The results are published within the framework of the Swiss Retrofit Heat Pump project, which is conducted by the Swiss Federal Office of Energy. The two-stage heat pump cycle has shown the best efficiency prospects. Oil migration between the upper stage and lower stage compressors is the main obstac

Following the pioneering work of the AGS Tokyo half project, a geographical information system has been developed to model the energy requirement of a urban area. The purpose of this platform is to model with sufficient details the energy services requirement of a given geographical area to allow the evaluation of the integration of advanced integrated energy conversion systems. This tool is used to study the emergence of more efficient cities that realize the integration of energy efficiency measures and o

Supplying electricity, heat and cold is an essential part of the development of more sustainable city districts. Previous studies have illustrated interest in using the exergy efficiency concept to decompose the problem and rank the technology combinations for heating or cooling according to their overall efficiency. This methodology is extended herein to include network losses that depend on the temperature level and grid losses that play a role when comparing electricity supplied by the grid rather than b

A summary of the objectives and conclusions reached in this project are: •A litterature search on post dryout heat transfer for pure refrigerants and for refrigerant-oil mixtures was performed and a comprehensive review written (Chapters 9, 10, and 11); •The correct thermodynamic definition of the heat transfer coefficient for evaporation of refrigerant-oil mixtures was presented and then used in the project, i.e. defining the heat transfer coefficient using the local bubble point temperature Tbub of the re

The substitution of CFC refrigerants in refrigeration systems, heat pumps and organic Rankine cycles for heat recovery, requires good methods for predicting heat transfer of substitute fluids. The measurements in the LENI test facility (concentric tubes with water flowing in a countercurrent flow) with HFC 407C, HFC 134a, HCFC 123, HFC 404A and HFC/HCFC 402A provide a new data band for new refrigerants, and allow a coherent comparison with old refrigerants CFC 11, CFC 12, CFC/HCFC 502 and with existing corr

Energy needs in urban areas are heterogeneous by their nature, spatial distribution and temperature level required. Three concepts of district energy networks that could provide the energy services efficiently to a city centre are compared. The focus is on ...

The methods for designing, planning and managing integrated energy systems, while holistically considering the major economic and environmental factors, are still embryonic. However, the first phase of the design is often crucial if we want to manage resou ...

Vehicle drivetrains are complex integrated systems, which need to be designed for numerous thermodynamic, economic and environmental factors. As part of a project of the Alliance for Global Sustainability between the MIT, the SFITs and the University of Tokyo, a new evolutionary multi-objective optimisation algorithm has been developed and applied to various problems including vehicle drivetrain configurations. The simulation of a potential vehicle is complex and calculation intensive. The new algorithm, th

Hybrid solar thermal power plants (with parabolic trough type of solar collectors) featuring gas burners and Rankine steam cycles have been successfully demonstrated by California's Solar Electric Generating System (SEGS). This system has been proven to be one of the most efficient and economical schemes to convert solar energy into electricity. Recent technological progress opens interesting prospects for advanced cycle concepts: a) the ISCCS (Integrated Solar Combined Cycle System) that integrates the par

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Dynamic Modeling and Simulation of Two-phase Evaporators and Condensers in the context of a CO2 Based District Energy Network

District Heating in the City of Tokyo: A Case Study using a new Integrated Simulation Environment

Energy efficient technologies towards a 2 kW society

Multicriteria Optimisation of Small Hybrid Solar Power System

Swiss Motor. Modification d’un moteur diesel pour le fonctionnement au gaz naturel en cogénération. Fonctionnement avec mélange stoechiométrique (l=1) et pauvre (l>>1).

Current state of models for the prediction of mechanical failures in solid oxide fuel cells

Multi-Objective Optimisation of Herringbone Grooved Gas Bearing Supporting a High Speed Rotor, Taking into account Rarefied Gas and Real Gas Effects

Evaporation de mélanges d’ammoniac et d’huile dans des tubes.

Pompe à chaleur air-eau à Haute Température. Phase 2: cycle à injection optimisé, essai journaliers et compreseur booster. Analyse thermo-économique.

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part I: Probability of failure of the cells

Process Integration: From Continuous to Batch Processes

Analyse de la migration d’huile dans les pompes à chaleur mono- et biétagées

EnerGis : A geographical information based system for the evaluation of integrated energy conversion systems in urban areas.

Exergy Efficiency Is a Key Performance Indicator to Rank Advanced Active Energy Technologies at the District Level

Heat Transfer and Pressure Drop in the Dryout Region of Intube Evaporation with Refrigerant/Lubricant Mixtures.

Evaporation du réfrigérant HFC 407C sur des tubes lisses ou à surface améliorée.

Key Energy and Technological Aspects of Three Innovative Concepts of District Energy Networks

Multiobjective Optimisation of integrated energy systems for remote communities considering economic and CO2 emissions

Multi-Objective Optimisation of Vehicle Drivetrains

Thermoeconomic Analysis of Advanced Solar-Fossil Combined Power Plants