Publications by Alfred Rufer | EPFL Graph Search

A four-cylinder pneumatic expansion motor with high efficiency

A four-cylinder pneumatic motor is proposed and analyzed as an expansion machine to be used in a compressed-air energy storage system. The motor uses a combination of displacement work at constant pressure followed by a sequence of expansion of the air. Th ...

Academia.edu Journals2025

Performance Evaluation of Static and Dynamic Compressed Air Reservoirs for Energy Storage

Alfred Rufer

The concept of static and dynamic reservoirs is presented, and their performances are evaluated. The static reservoir is a simple reservoir with constant volume, and the dynamic one has a volume which varies as a function of the position of an internal pis ...

MDPI AG2025

Towards the Isothermal Gas Compression—A Novel Finned Piston-Cylinder with Increased Efficiency

Alfred Rufer

In this paper, a novel concept of a finned piston system is presented and analyzed in which the compression heat is continuously extracted from the compression chamber. The resulting compression characteristic moves in the direction of an isothermal proces ...

2024

ENERGETIC PROPERTIES OF THE (FAST) CHARGING AND DRIVING OF AN ELECTRIC VEHICLE – A RAGONE ANALYSIS

Alfred Rufer

The energy efficiency of EVs is analysed for the charging and for the driving process where real parameters of a product of the automotive industry are considered. The efficiency in the charging mode is analysed and represented in function of the charging ...

2024

Semi-rotary and Linear Actuators for Compressed Air Energy Storage and Energy Efficient Pneumatic Applications

Alfred Rufer

This text explains the use of compressed air for energy storage and efficient pneumatic applications. Chapters cover the elementary physical and engineering principles related to compressed air, including compression and expansion characteristics, adiabati ...

Taylor and Francis2023

Expansion Work Recovery of Hydrogen for a FC-Truck-Tentative Design of an Expansion Machine

Alfred Rufer

Hydrogen powered vehicles use high-pressure reservoirs from which the gas is transferred to the low-pressure fuel-cell via a classical pressure reduction valve. In these systems no expansion work is recovered and the question is addressed of the potential ...

MDPI2023

Increasing the Energy Efficiency of Gas Boosters for Hydrogen Storage and for Refueling Stations

Alfred Rufer

A new electrically driven gas booster is described as an alternative to the classical air-driven gas boosters known for their poor energetic efficiency. These boosters are used in small scale Hydrogen storage facilities and in refueling stations for Hydrog ...

MDPI2023

Quantitative Design of a New e-Methanol Production Process

Alfred Rufer

In the context of the need to significantly reduce greenhouse gas emissions from personal transportation, a new process for the production of e-methanol is presented. It is a CO2 hydrogenation process, powered mainly by renewable energy sources such as pho ...

MDPI2022

On The Efficiency Of Energy Storage Systems - The Influence Of The Exchanged Power And The Penalty Of The Auxiliaries

Alfred Rufer

Storage is an important domain of the energy sector, with its traditional, classical solutions for smaller and larger amounts of energy. Energy storage has become of higher importance in relation with the development of alternative energy sources, leading ...

UNIV NIS2021

A High Efficiency Pneumatic Drive System Using Vane-Type Semi-Rotary Actuators

Alfred Rufer

A compressed air driven generator is proposed, where the pneumatic energy is converted into mechanical energy using two vane-type rotational actuators. The use of a second actuator with a higher displacement in order to produce a thermodynamic expansion al ...

UNIV NIS2021

Design and Control of a KE (Kinetic Energy) - Compensated Gravitational Energy Storage System

Alfred Rufer

A gravitational energy storage device is described where the kinetic energy to recover while braking a vertically moving mass is compensated by an auxiliary storage device based on supercapacitors. The characteristic power surge occurring by a fast decreas ...

IEEE2020

A Bidirectional Buffered Charging Unit for EV’s (BBCU)

Alfred Rufer

A bidirectional buffered charging unit for EV’s is presented, allowing the charge with high power even if the line current capability is limited. The bidirectional buffer is connected to the AC line and is mainly dedicated to vehicles with on-board AC-DC c ...

2018

System Architectures for Multiports, Bidirectional and Buffered Charging Units for EV’s

Alfred Rufer

Bidirectional buffered units for Multiports charging of EV’s are presented, allowing to charge with high power even if the line current capability is limited. The systems are also dedicated to operate as reactive power compensators, or to provide grid syst ...

2018

A Bidirectional Buffered Charging Unit for EV's (BBCU)

Alfred Rufer, Gabriel Fernandez

A bidirectional buffered charging unit for EV's is presented, allowing the charge with high power even if the line current capability is limited. The bidirectional buffer is connected to the AC line and is mainly dedicated to vehicles with on-board AC-DC c ...

IEEE2018

Multiobjective Optimization of Medium-Frequency Transformers for Isolated Soft-Switching Converters Using a Genetic Algorithm

Alfred Rufer, Alejandro Rujas, Irma Villar, Asier Garcia Bediaga

The main challenge of medium-frequency transformers is the number of design parameters, constraints and objectives, and the difficulty of handling them on a particular design. This paper presents a novel computer-aided optimal design for MF transformers us ...

Ieee-Inst Electrical Electronics Engineers Inc2017

Analytical Models of Multiphase Isolated Medium-Frequency DC-DC Converters

Alfred Rufer, Alejandro Rujas, Irma Villar, Asier Garcia Bediaga

This paper presents new analytical equations, parametrized with respect to the number of converter phases, for multiphase isolated dc-dc topologies. This paper describes five multiphase isolated converter models, as well as their level of accuracy. Based o ...

Ieee-Inst Electrical Electronics Engineers Inc2017

Feed-Forward based Control in a DC-DC Converter of Asymmetric Multistage Stacked Boost Architecture

Alfred Rufer, Gina Kristin Steinke, Georgios Mademlis

A new feed-forward control technique for a DC-DC step-up converter based on the asymmetric Multistage Stacked Boost Architecture (MSBA) is proposed. The devel-oped feed-forward controller directly handles the load current and the perturbations that may be ...

Ieee-Inst Electrical Electronics Engineers Inc2017

The Dream of Efficient Energy Storage - From Bess, Kers & Co to the Hybrid Power Plant

Alfred Rufer

Storage is an important domain of the energy sector, with its traditional, classical solutions for smaller and larger amounts of energy. Energy storage has become of higher importance in relation with the development of alternative energy sources, called a ...

IEEE2017

Design, modeling and experimental validation of a novel finned reciprocating compressor for Isothermal Compressed Air Energy Storage applications

Alfred Rufer, Mahbod Heidari

Considering the need for a reliable and environmentally friendly energy storage solution for addressing renewable energy intermittency issue and following the developments on Isothermal Compressed Air Energy Storage (I-CAES) systems, a new finned piston co ...

Pergamon-Elsevier Science Ltd2017

Input-Series and Output-Series High Voltage Converter with Active Balancing Circuit for N-1 Operation

Alfred Rufer, Tiago Alexandre Nabais Lima

An input-series/output-series converter dedicated to high power applications is presented. The converter is composed of plural MF transformers based on DC-DC sub-converters. The series connection allows reaching input-voltage levels in the range of several ...

Ieee2016