Flexible-fuel vehicle | EPFL Graph Search

A flexible-fuel vehicle (FFV) or dual-fuel vehicle (colloquially called a flex-fuel vehicle) is an alternative fuel vehicle with an internal combustion engine designed to run on more than one fuel, usually gasoline blended with either ethanol or methanol fuel, and both fuels are stored in the same common tank. Modern flex-fuel engines are capable of burning any proportion of the resulting blend in the combustion chamber as fuel injection and spark timing are adjusted automatically according to the actual blend detected by a fuel composition sensor. This device is known as an oxygen sensor and it reads the oxygen levels in the stream of exhaust gasses, its signal enriching or leaning the fuel mixture going into the engine. Flex-fuel vehicles are distinguished from bi-fuel vehicles, where two fuels are stored in separate tanks and the engine runs on one fuel at a time, for example, compressed natural gas (CNG), liquefied petroleum gas (LPG), or hydrogen. The most common commercially a

Flexibilisation of Biogas-Based Power-to-Gas Processes: A Techno-Economic and Experimental Assessment

Andreas Gantenbein

Biogas-based power-to-X technology allows storing renewable electricity, while producing CO2-neutral products.This work investigates the conversion and upgrading of digestion-derived gas mixtures with focus on increasing the operational flexibility of the overall process. Compensation of fluctuations in the feed gases enable a better economic predictability of the processes and increase the product gas output.A techno-economic evaluation was performed on bubbling fluidised bed (BFB) methanation and biological methanation for CO2 conversion in all-year operation. Each considered process was modelled and optimised to obtain grid-ready biomethane. Rate-based models were used for the main units (BFB reactor, H2-separation membrane). For the biological methanation, simulated performance data from literature were included. The analysis revealed a 17 - 19% lower production cost for BFB methanation, mainly due to lower investment cost for the main reactor vessel. Instead of using PEM electrolysis, high temperature electrolysis (SOE) would allow for heat integration with the BFB reactor, which increases the plant efficiency from 54% to 73% (LHV). A further production cost reduction can be achieved by direct methanation of biogas, omitting prior separation of CO2.Based on gas separation experiments with a commercial biogas upgrading module (Evonik Sepuran) performed in a TRL 5 plant, a flexible upgrading concept using a permeation model was developed. It allows to swiftly switch between conventional membrane-based CO2 separation by a 2-stage membrane unit and direct methanation of biogas and subsequent H2 recycling.A techno-economic analysis was performed on the flexible upgrading concept. The operation hours of the electrolyser were determined by applying a threshold to the electricity price distribution of the past years. The sensitivity on electricity cost (i.e. PtG operation hours) is clearly reduced with the flexible processes, resulting in a better economic predictability of the overall process, compared to a pure PtG installation. System analysis shows the need to allow part load operation of the methanation.Symmetric part load operation (reduced availability of CO2 and H2) was tested in a field experiment by direct methanation of biogas with subsequent H2 recycling in the TRL 5 methanation pilot plant. Stable operation of the methanation plant could be achieved at part load levels from 45% to 100% with closed recycle loop. The BFB reactor alone was tested in a load range of 20 to 100%. A dynamic experiment demonstrated fast, successive load changes while still producing grid-ready biomethane.Asymmetric part load (only H2 limiting) operation was investigated by process simulations and field experiments. Since CO2 is present in the system in an over-stoichiometric amount, H2 recycle and CO2 separation have to be performed simultaneously. Process simulations showed that selecting a most ideal PtG configuration based on technical feasibility is difficult, as further constraints, such as overall economics and operation scheduling have to be considered in process design and evaluation. In all cases, the CO2 separation from the integrated processes leads to a loss of H2 and CH4 from the process. The introduction of an additional membrane stage with a sweep stream is proposed to reduce the loss of reactive gases via the off gas stream.

EPFL2022

Cooperative Perception Algorithms for Networked Intelligent Vehicles

Milos Vasic

The degree of intelligence built-in in today's vehicles in constantly on the rise. The vehicles are being equipped with sensors, with the goal to estimate the state of the vehicle and the environment surrounding it. Intelligent algorithms that process the sensory data can give their output at different levels, ranging from simple warnings, over evasive maneuvers (such as emergency braking), to complete autonomy. While it has been demonstrated that autonomous vehicles can rely solely on their on-board sensors, their performance can be optimized through cooperation with other road vehicles. Information coming from infrastructure can be fused in as well. This is where the communication between vehicles, as well as between vehicles and the infrastructure, comes into play. The main benefits of cooperation include larger coverage and extended situational awareness through sharing sensor data and vehicle intentions (trajectories). In this thesis, we address the cooperative perception problem. To solve this problem efficiently, we construct an end-to-end framework in three steps. First, we design an experimental platform that allows for testing our cooperative perception algorithms. In particular, we equip two fully electric Citroën C-ZERO cars with sensors, on-board computers and communication equipment. At the same time, we reproduce our platform in Webots, a high-fidelity simulation tool originally developed for mobile robots and recently upgraded for road vehicles. We develop and calibrate vehicle and sensor models with the goal to reproduce the real-world conditions as closely as possible, and in turn facilitate the deployment of algorithms developed in simulation on real cars. Second, we design two cooperative algorithms for tracking multiple objects (cars and pedestrians) using laser and camera sensors. The key components of the algorithms are our cooperative fusion methods, which allow for fusion of data obtained from a cooperative vehicle with the data obtained from on-board sensors. The algorithms are first evaluated in simulation and tested in specific scenarios. For instance, to showcase the power of our approach in a potential application, we design an overtaking decision algorithm that uses our cooperative perception algorithm as a baseline. The overtaking application proves the added-value of cooperative perception in situations with occluded or insufficient sensory field of view. Third, we deploy a selected algorithm on real vehicles and validate it in real time. A distributed software framework is designed for this purpose, enabling a relatively smooth transition from simulated to real environments. Moreover, the cooperative perception algorithm is subsequently enhanced for operating in more complex scenarios. Furthermore, we develop a cooperative localization method to achieve increased accuracy in cooperative vehicles' relative localization, thus enabling our cooperative perception algorithm to work properly when deployed on moving vehicles. Overall, we develop an end-to-end framework for cooperative perception, which unifies many different sensory technologies. Despite the end goal has always been that of deploying the framework on our test vehicles, we make substantial effort to keep it as general as possible. Our framework represents a stepping stone towards more complex, multi-vehicle automated systems.

EPFL2017

Refining sweet sorghum to ethanol and sugar: economic trade-offs in the context of North China

Arnaud Dauriat, Edgard Gnansounou

Reducing the use of non-renewable fossil energy reserves together with improving the environment are two important reasons that drive interest in the use of bioethanol as an automotive fuel. Conversion of sugar and starch to ethanol has been proven at an industrial scale in Brazil and the United States, respectively, and this alcohol has been able to compete with conventional gasoline due to various incentives. In this paper, we examined making ethanol from the sugar extracted from the juice of sweet sorghum and/or from the hemicellulose and cellulose in the residual sorghum bagasse versus selling the sugar from the juice or burning the bagasse to make electricity in four scenarios in the context of North China. In general terms, the production of ethanol from the hemicellulose and cellulose in bagasse was more favorable than burning it to make power, but the relative merits of making ethanol or sugar from the juice was very sensitive to the price of sugar in China. This result was confirmed by both process economics and analysis of opportunity costs. Thus, a flexible plant capable of making both sugar and fuel–ethanol from the juice is recommended. Overall, ethanol production from sorghum bagasse appears very favorable, but other agricultural residues such as corn stover and rice hulls would likely provide a more attractive feedstock for making ethanol in the medium and long term due to their extensive availability in North China and their independence from other markets. Furthermore, the process for residue conversion was based on particular design assumptions, and other technologies could enhance competitiveness while considerations such as perceived risk could impede applications.