Publications by Daniel Favrat | EPFL Graph Search

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The 5th generation compact district heating and cooling networks in a temperature range of 10 to 16 °C have a great potential for energy savings by providing a heat source for decentralized heating heat pumps, a cold source for air-conditioning and a heat ...

Although heat pump based district heating is often an obvious solution, adapting the delivery temperature to the most exigent users is detrimental to overall system performance. This pitfall can be avoided with a centralized plant of heat pumps, cogeneration and an auxiliary furnace, supplemented by decentralized heat pumps. However, the problem of mixed energy production and delivery which this poses is complex and presents for the daunting if not impossible task of adequately, much less optimally, determi

Switzerland like many countries plans to undertake an energy transition and the government proposes different paths for 2035 and 2050 to achieve it. However the authors of this paper felt the need for a better information of the public on the energy matter ...

Multistage heat pumps are one of the most efficient technologies for delivering heat at temperatures below 100°C, Thanks to their fairly high exergy efficiency. In the recent years the development of radial compressors mounted on gas bearings have unlock t ...

Biogas as renewable source of energy is underexploited. We extrapolate the potential recoverable from waste streams in the EU-15 to 769 PJ (17.5 Mtoe), of which under 10% is used (1.7 Mtoe). SOFC can promote the valorisation of biogas in small CHP installations (10-500 kWel). An energy/exergy balance model was performed on a SOFC demonstration unit coupled to an existing farm biogas site. From 8.9 kW of biogas, the module was calculated to derive 3.4 kWel and 4.1 kW useful heat, achieving 38% electrical and

The degradation of solid oxide fuel cells (SOFC) depends on stack and system design and operation. A methodology to evaluate synergistically these aspects to achieve the lowest production cost of electricity has not yet been developed. A repeating unit mod ...

Few experimental test data are available for evaporation of ammonia inside tubes and numerous new data have been measured and presented here. An improved approach to the prediction of flow boiling heat transfer in horizontal tubes has been proposed through the study of each flow pattern separately, incorporating a new criterion defining the onset of nucleate boiling as a function of the critical convective heat transfer coefficient representative of the location where nucleate boiling might occur. A new fun

The energy integration of industrial processes is becoming increasingly more effective thanks to new methodological developments such as pinch technology. This paper aims at extending the number of factors considered in pinch analysis toward a life-cycle optimisation and proposes new synthesis representation schemes. The original pinch method centres primarly on maximizing the internal heat transfer with the choice of appropriate Tmin s. The proposed extension takes into account the complete heat transfer

As part of a comprehensive study on factors affecting flow boiling in horizontal tubes, local boiling heat transfer coefficients were measured for R- 134a evaporating inside the same 12.00 mm bore, plain tube for horizontal flow, vertical upflow and vertical downflow over a wide range of mass velocities, vapor qualities and heat flux for a direct comparison of the effects on tube orientation on heat transfer. The experiments show a significant effect of flow direction on local heat transfer coefficients wit

The concept studied in this work is a low power ORC-ORC system (about 20 kW heat at the condenser) which is composed of an ORC engine cycle driving a reversed ORC heat pump cycle, both using the same fluid. The radial compressor and turbine are directly co ...

Intube flow boiling experiments for refrigerant R-134a mixed with a lubricating oil are reported. The tests were run at a nominal inlet pressure of 3.4 bar over a wide range of vapor qualities at mass velocities of 100, 200 and 300 kg/m2s (73500, 147000 and 220500 lb/h ft2) for inlet oil concentrations from 0, 0.5, 1.0, 3.0 and 5.0 wt.% oil. At high vapor qulities (x > 0.75-0.85), the local boiling heat transfer coefficients dropped off rapidly with increasing oil concentration. At low to intermediate vapor

This study deals with a type of thermally driven heat pumps that consists of a reverse Rankine heat pump cycle, the compressor of which is driven by the turbine of a supercritical Organic Rankine Cycle (ORC). The application is residential heating (domesti ...

From the standpoint of an energetically and economically efficient waste elimination, the design and operation of optimized incineration power plants with the cogeneration of electricity and heat has become today an important issue. Decision models developed to minimize the total costs associated with such systems only partially respond to the problems associated with the choice of the synthesis (configuration, technology), the design, and the operation of the waste treatment unit. In fact, the time factor

Domestic heat pumps have been identified as a key-technology to decrease the energy consumption of the domestic sector, which represents 29% of the world final energy consumption. Space & water heating represent more than two third of the domestic sector e ...

Thermo-economic modelling techniques are well known techniques to optimise power plant designs. These methods are usually based on the definition of a superstructure that includes the major options of the design. If this approach has proved to be appropria ...

The work accomplished during the second period of the project mainly focused on the experimental evaluation of the prechamber system comparing its performance regarding emissions and efficiency to standard spark ignition mode. Further instrumentation of the engine made it possible to verify that ignition actually takes places inside the prechamber. A system to start up the engine without spark plug was installed and successfully tested. In order to achieve the necessary further improvement of the engine per

Modern energy systems are more and more based on integrated technologies in a world evolving towards increasing concerns not only for economics but also for environmental issues with a growing focus on resources and emissions. In parallel, information tech ...

A novel ignition concept based on autoignition in an unscavanged prechamber is currently being developed at the Laboratory for Industrial Energy Systems (LENI). On a single cylinder test engine a series of experimental runs (CR=8.5-14, =1-1.6, RPM=1150/150 ...

There is a growing need for the analysis of energy systems not only on the bases of their operational life, but also on the basis of considerations for the manufacturing and recycling phases. Environmental and to a lesser extent resource scarcity factors sould also be taken into consideration. A general unified thermodynamic approach based on exergy was recently proposed [1,2,3] and is briefly summarized. The main idea of this approach is to minimize the cumulated exergetic losses of operation, manufacture

Gaseous fuels produced, for example, by waste or agricultural by-products fermentation (biogas) can be burned in-situ by cogeneration systems like spark-ignition internal combustion engines. However, the more and more stringent legislation for exhaust gas emissions requires improvement of the combustion process particularly when catalytic after treatment is not reliable as in the case of sewage or landfill biogas. The system proposed in this paper is the use of an unscavenged combustion prechamber instead o

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District heating and cooling energy network using CO2 as a heat and mass transfer fluid

An Environomic Approach for the Life Cycle Modeling and Optimization of a District Heating Network Based on Centralized and Decentralized Heat Pumps (Part I: Methodology).

The information platform energyscope.ch on the energy transition scenarios

Dynamic Modeling and Simulation of Two-stage Compression Heat Pumps with Flash Economizer

Biogas exploitation by SOFC

Progressive activation of degradation processes in solid oxide fuel cells stacks: Part I: Lifetime extension by optimisation of the operating conditions

Evaporation of Refrigerants in a Horizontal tube: An Improved Flow Pattern Dependent Heat Transfer Model Compared to Ammonia Data

Energy Integration of Industrial Processes Based on the Pinch Analysis Method Extended to Include Exergy Factors

Flow Boiling in Horizontal and Vertical Tubes: the Effect of Tube orientation on Heat Transfer.

Prototype of a thermally driven heat pump based on integrated organic Rankine cycles (ORC)

Local Flow Boiling and Pressure Drop Measurements for R134a/Oil Mixtures Part 1: Evaporating in a Microfin Tube

THEORETICAL STUDY OF THERMALLY DRIVEN HEAT PUMPS BASED ON DOUBLE ORGANIC RANKINE CYCLE: WORKING FLUID COMPARISON AND OFF-DESIGN SIMULATION

Time-Dependent Thermoeconomic Optimization of the Future Waste Incineration Power Plant in Posieux, Switzerland

Experimental investigation of a two-stage oil-free domestic Air/Water heat pump prototype powered by an oil-free high-speed twin-stage radial compressor rotating on gas bearings

Advanced Power Plant Design Methodology using Process Integration and Multi-Objective Thermo-Economic Optimisation

Prechamber autoignition of gaseous mixtures: numerical simulation with detailed chemistry and testing on engine test bench

From thermoeconomics to environomics and beyond

Experimental investigation of prechamber autoignition in a natural gas engine for cogeneration

Contribution to a Life Cycle Exergy Analysis of Heat Pumps with Various Evaporator Sources.

Unscavenged Combustion Prechamber as a way to Improve Efficiency and Emissions of a Lean-Burn Cogeneration Biogas Engine: Comparison with Natural Gas