Stéphane Citherlet - Academia.edu (original) (raw)

Papers by Stéphane Citherlet

Recycled concrete is now used in many different applications and scientific studies have shown th... more Recycled concrete is now used in many different applications and scientific studies have shown that they have performances similar to concretes which use natural gravel [1, 2]. With the aim to evaluate the environmental impacts of recycled concrete, a life cycle impact assessment (LCIA) has been performed and results compared with those of normal This study is the result of a project involving the “Claie-aux-Moines (GCM)” gravel mining company and the Canton of Vaud to determine whether the impacts of transporting materials are significant for three different concrete production processes. Two relevant environmental indicators in building environment showed that the recycled concrete have relatively less impacts than normal concrete. This study also demonstrated that the material origin should be taken into account in the LCIA as transport distances have a non-negligible influence on the impacts. These findings suggest that recycled concrete could be an alternative solution to norma...

Universidade do Minho eBooks, 2017

This publication has been compiled with reasonable skill and care. However, neither University of... more This publication has been compiled with reasonable skill and care. However, neither University of Minho nor the EBC Contracting Parties (of the International Energy Agency Implementing Agreement for a Programme of Research and Development on Energy in Buildings and Communities) make any representation as to the adequacy or accuracy of the information contained herein, or as to its suitability for any particular application, and accept no responsibility or liability arising out of the use of this publication. The information contained herein does not supersede the requirements given in any national codes, regulations or standards, and should not be regarded as a substitute for the need to obtain specific professional advice for any particular application.

Proceedings of EuroSun 2018, 2018

During the last years, solar thermal systems have lost in attractiveness mostly due to their high... more During the last years, solar thermal systems have lost in attractiveness mostly due to their high initial installation costs, higher complexity compared to photovoltaic systems and a regular need of maintenance to avoid overheating and freezing problems, e.g. control of glycol mixture properties. Drainback (DB) solar thermal systems may overcome some of these issues and contribute to the market recovery as it prevents overheating and freezing of the solar system components even when pure water is used as the heat carrier fluid. It also needs less components than classical pressurised systems, which leads to less complex, lower system costs. Nevertheless, this type of system has not been very successful in Switzerland, only accounting for a small part of the market. In order to identify the barriers preventing the wide Swiss acceptance of DB systems, a literature review was performed and an online survey conducted and addressed to the different actors of the solar thermal sector. The aim is to understand the reasons of low market penetration of DB systems in Switzerland and to clearly identify the main barriers to its spreading. Results show that investments in research, product development, technology demonstration and market deployment in the form of professional training and technology information are essential to promote the DB in Switzerland.

The performance of four solar thermal collectors (f lat plate, evacuated tube, unglazed with rear... more The performance of four solar thermal collectors (f lat plate, evacuated tube, unglazed with rear insulation and unglazed without rear insulation) wa s experimentally measured and simulated for temperatures below ambient. The influence of severa l parameters (e.g. collector inlet temperature, air temperature, condensation) is investigated under di fferent operating conditions (day and night). Under some conditions condensation might occur and heat g ains could represent up to 55% of the total unglazed collector energy by night. Two TRNSYS coll ector models including condensation heat gains are also evaluated and results compared to experime ntal measurements. A mathematical model is also under development to include, in addition to the co ndensation phenomena, the frost, the rain and the long-wave radiation gains/losses on the rear of the solar collector. While the potential gain from rai n was estimated to be around 2%, frost heat gains wer e m asured to be up to 40% per day, under...

This paper presents an overview of the R&D activities for the Bâti-Tech project that concerns int... more This paper presents an overview of the R&D activities for the Bâti-Tech project that concerns integration of solar thermal collectors into an existing, commercialised multifunctional facade element. The study involves both monitoring and test bench measurements along with dynamic simulations of the facade element integrated in a building. The existing facade concept includes thermal and acoustic insulation and PV production. The overall objective of the project is to modify the current facade element and integrate a solar thermal collecting function for building heating purposes. This project, funded by the Canton of Vaud, was launched at the end of 2013 within the framework of its "100 millions pour les energies renouvelables et l’efficacite energetique" programme. Research has indicated that the PV performance of the investigated facade is greatly affected by shading of the near surrounding. Measured stagnation temperatures of the PV panel of the facade element have also...

For several decades, di fferent numerical models of storage tanks using PCM for latent energy sto... more For several decades, di fferent numerical models of storage tanks using PCM for latent energy storage have been developed; a few of thes e models have been elaborated to work with the TRNSYS simulation package (Jokisalo, 2000). Unfortunately, none o f them gave enough s atis faction to allow a l arge di ffusion, either due to a l ack o f time to test its reliability (Visser, 1986), or a lack o f flexibility which does not allow the modelling o f di fferent types o f containers for PCM (Egolf, 1997).

The aim of this study is to analyse the energy and economic performances of different types of fa... more The aim of this study is to analyse the energy and economic performances of different types of facilities coupling a ground/water heat pu m with an air-heater equipped with solar thermal collectors. Different parameters such as the annual coefficient of performance or the power consumption were compared between various conditions. The optimization of the control and energy storage was investigated to reduce the triggering time of the air-heater. This study was performed by dynamic simulation usin g TRNSYS. In the time allocated to this project, the icing of the air-hea ter as well as the defrost cycles could not be studied as no numerical model takes into acc ount this phenomenon. At current energy prices, the most economical solut ion is the heat pump without solar thermal collectors. However, from the energy point of view, the overall annual coefficient of performance of the system could be i mproved by 15% to 36% depending on the climate. Introduction Nowadays, solar installation...

Pierryves Padey, HEIG-VD / IGT, pierryves.padey@heig-vd.ch, www.lesbat.ch Stephane Citherlet, HEI... more Pierryves Padey, HEIG-VD / IGT, pierryves.padey@heig-vd.ch, www.lesbat.ch Stephane Citherlet, HEIG-VD / IGT, stephane.citherlet@heig-vd.ch, www.lesbat.ch Sara Eicher, HEIG-VD / IGT, sara.eicher@heig-vd.ch, www.lesbat.ch Francesca Cellina, SUPSI / ISAAC, francesca.cellina@supsi.ch, http://www.supsi.ch/isaac Roberta Castri, SUPSI / ISAAC, roberta.castri@supsi.ch, Uros Tomic, ZHAW / INE, tomi@zhaw.ch, http://zhaw.ch/ine Dominique Kunz, FHNW / IEBau, dominique.kunz@fhnw.ch, https://www.fhnw.ch Vicente Carabias, ZHAW / INE, cahu@zhaw.ch, http://zhaw.ch/ine Jürg Bichsel, FHNW / IEBau, Juerg.bichsel@fhnw.ch, https://www.fhnw.ch

Journal of Physics: Conference Series, 2019

In Switzerland, most of the information available on the energy bills corresponds to the minimum ... more In Switzerland, most of the information available on the energy bills corresponds to the minimum legal requirements imposed by national regulations. Such a scarcely understandable information does not motivate consumers to reflect on their level of energy consumption. A more user-friendly information presentation on the energy bill may induce increased awareness, laying the grounds for behaviour changes required to achieve the goals of the Energy Strategy 2050 of the Swiss Federal Council. The aim of the IMPROVE project was to explore how both consumers and energy utilities evaluate and perceive the importance of introducing enriched information on the energy bill to encourage households to reconsider their energy consumption levels.

Energy Procedia, 2016

Willing to be an active participant to the Swiss strategy for sustainable development, Colas Swit... more Willing to be an active participant to the Swiss strategy for sustainable development, Colas Switzerland SA, has decided to integrate a solar thermal installation in one of its bitumen storage industrial site. Situated in Yverdon-les-Bains (Switzerland), the solar installation aims to provide up to 60% of the thermal energy demand of the site. Coupled with a gas boiler, the solar collectors were designed to meet the energy needs of an onsite building, and to ensure constant temperature of a bitumen tank and two emulsions tanks (mixture of bitumen and water). In order to analyse and optimise the thermo-economic and environmental efficiency of this installation, a R&D project funded by the Swiss Federal Office of Energy was launched in 2014. This article gives an overview of the project objectives and describes the solar thermal installation and its operating modes. It also presents the numerical model and the first experimental results. First observations have revealed a thermal installation operating well behind its expected targets. Typically, the solar collector efficiency at temperatures above 200°C is 50% lower than expected since it is operating under non-optimal conditions. Some technical dysfunctions have also been detected in the control system of one of the storage tanks. Consequently, a thorough evaluation of the operation of the installation was conducted to identify any other anomalies. In parallel to this work, the numerical model of the installation was developed and is currently under validation against the ongoing experimental measurements. Preliminary simulations of the installation in its current state have showed a solar yield nearly 2 times lower than expected, confirming the existence of anomalies in the running of the installation.

In the framework of the IEA Task 32 (Solar Heating and Cooling Programme), we developed a numeric... more In the framework of the IEA Task 32 (Solar Heating and Cooling Programme), we developed a numeric model to simulate heat transfer in phase change materials (PCM), and experimental data. The analyzed system is bulk PCM plunged in a water tank storage of a solar combisystem (heating and domestic hot water production). The numerical model, based on the enthalpy approach,

Solar Energy, 2015

Combined heat pumps and solar collectors got a renewed interest on the heating system market worl... more Combined heat pumps and solar collectors got a renewed interest on the heating system market worldwide. Connected to the heat pump evaporator, unglazed solar collectors can considerably increase their efficiency, but they also raise the coefficient of performance of the heat pump with higher average temperature levels at the evaporator. Simulation of these systems requires a collector model that can take into account operation at very low temperatures (below freezing) and under various weather conditions, particularly operation without solar irradiation. A solar collector mathematical model is developed and evaluated considering, the condensation/frost effect and rain heat gains or losses. Also wind speed and long wave irradiation on both sides of the collector are treated. Results show important heat gains for unglazed solar collectors without solar irradiation. Up to 50% of additional heat gain was found due to the condensation phenomenon and up to 40% due to frost under no solar irradiation. This work also points out the influence of the operating conditions on the collector's characteristics. Based on experiments carried out at a test facility, every heat flux on the absorber was separately evaluated so that this model can represent a valuable tool in optimising the design or the thermal efficiency of the collector. It also enables the prediction of the total energy yield for solar thermal collectors under extreme operating conditions.

Proceedings of the EuroSun 2014 Conference, 2015

In 2012, COLAS, the worldwide leader in the bitumen and road coatings sector, has decided to equi... more In 2012, COLAS, the worldwide leader in the bitumen and road coatings sector, has decided to equip one of its regional sites with a solar thermal installation for temperatures up to 200°C. Coupled with a gas boiler, the solar collectors were installed with the dual purpose of meeting the thermal energy needs of a workshop building and to maintain two bitumen storage tanks above its melting point. This article gives a short description of the heating system at this industrial site and of its operating modes. It also describes the numerical model developed for detailed system simulation. First simulation results give a low annual solar heat gain of 94.6 kWh/m2 which is 2.6 times lower than initial estimations. Further investigations will be performed during the ongoing project in order to optimize the solar heat gain and to identify the reasons for this unsatisfactory result.

Energy Procedia, 2012

In this article, a R&D project is described involving a prototype solar assisted heat pump (HP) d... more In this article, a R&D project is described involving a prototype solar assisted heat pump (HP) designed for domestic hot water preparation for single family dwellings. This project, developed within the framework of Task 44 of the IEA Solar and Cooling Programme, uses solar energy on the HP evaporator side to maximize the performance level of the system. In cases where solar energy is not enough, the HP under investigation has been designed to extract energy from the heating circuit of the building. This study involves both test bench measurements and dynamic simulations of the solar assisted heat pump system. The overall objectives of the project are summarised as follows: Development of solar thermal technology Improvement of HP performance for DHW production Reduction of non-renewable energy consumption Reduction of environmental impacts This article presents an overview of the project and its current status.

Energy Procedia, 2014

Solar heat pumps (SHP) are a class of heating systems combining solar thermal technology with hea... more Solar heat pumps (SHP) are a class of heating systems combining solar thermal technology with heat pumps. In this article the life cycle impact assessment (LCIA) of a SHP system used to produce domestic hot water (DHW) and space heating (SH) for single family dwellings is presented. This study intends to evaluate the environmental impacts of the energy and material used in a serial SHP installation and identify areas for improvement by applying a "cradle-to-grave" approach when analysing the system. This includes the installation materials both in their manufacturing and disposal phases as well as the energy consumption for DHW and SH throughout a service life of 20 years. In addition, it provides a comparison against two other residential heating systems operating with the same life expectancy. In this LCIA, two environmental related indicators are used, one associated with depletion of non-renewable energy resources (CED NRE) and the other with climate change (GWP). The impact of the type of electricity used was also investigated by defining, in addition to the European supply mix, an alternative supply mix with electricity deriving from renewable sources. This study shows that SHP have lower environmental impacts than systems operating on electricity only. Installations with large solar collector surfaces are also seen to lead to lower energy consumption related impacts. If the electricity used by these systems derives from renewable sources, the environmental performance improves. However, under these conditions, the SHP impact (material and energy consumption) related to climate change will be of the same order as that of the electric system due to a higher contribution of the infrastructure content of these systems.

Energy and Buildings, 2007

... Available online 23 February 2007. Abstract. This paper describes the numeric model developed... more ... Available online 23 February 2007. Abstract. This paper describes the numeric model developed to simulate heat transfer in phase change materials (PCM) plunged in water tank storage. ... 2.5.Heat transfer. 2.5.1. Thermal conduction inside PCM in solid or liquid phase. ...

Energy Procedia, 2015

Existing buildings are responsible for a major share of energy use and greenhouse gases emissions... more Existing buildings are responsible for a major share of energy use and greenhouse gases emissions in the total environmental impacts of the construction sector. While renovating a building increases its energy performance, it also raises the investment costs or environmental impacts due to the materials and building integrated technical systems (BITS) added to improve its energy performance. To address these trade-offs, there is a need to consider a life cycle approach to avoid impacts' transfer between the operational and embodied impacts. In this paper, we present a scientifically sound, yet practical Life Cycle Assessment (LCA) methodology for building renovation developed in the framework of the IEA annex 56 "Cost effective energy and carbon emissions optimization in building renovation". The approach is consistent with the existing building LCA's state-of-the-art but goes into a more applicable methodology by focusing only on the significant life cycle stages for energy related building renovation i.e. the production, transportation, replacement and end of life of new materials for the thermal envelope and BITS and the operational energy demand before and after renovation. In this paper, the methodology is applied on a case study of a multi residential building built in 1965 in Western Switzerland which was renovated in 2010. The LCA results are presented using three indicators: the total and non-renewable cumulative energy demand (CED) and the global warming potential (GWP). While embodied impacts due to the new materials and BITS remain negligible in the renovated building compared to the energy savings, it is found that the overall impacts are reduced from a factor 4 for the GWP. This study should be connected to the other contributions of the IEA annex 56 including costs assessment in order to determine cost effective and low environmental impacts building renovation.

This paper focuses on the environmental impacts assessment module recently implemented in an ener... more This paper focuses on the environmental impacts assessment module recently implemented in an energy balance tool. It describes the data and the methodology used to evaluate these impacts. It is based on a life cycle approach and includes not only the energy consumption during the operation phase, but also the impacts of the contruction materials, from manufacturing to waste disposal. This tool has been used within the framework of a national projet to perform a life cycle assessment of 20 different buildings located in Switzerland. One of these case studies is presented in this paper. ENVIRONMENTAL IMPACTS Building life cycle The environmental impacts of a building depend on two major contributions: The construction materials The energy consumed during the occupation phase Figure 1 shows the different phases occurring during the building’s life cycle.