Cleantech | EPFL Graph Search

Les cleantech (abréviation de clean technology) sont les techniques et les services industriels qui utilisent les ressources naturelles, l’énergie, l’eau, les matières premières dans une perspective d’amélioration importante de l’efficacité et de la productivité. Cette approche s’accompagne d’une réduction systématique de la toxicité induite et du volume de déchets, et assure une performance identique aux technologies existantes ou supérieure à celles-ci. Terminologie Le terme cleantech correspond à la terminologie utilisée par les fonds d’investissements américains et signifie littéralement « technologies propres ». Parmi les équivalents proposés en français, on trouve les termes « éco-activités innovantes », « éco-innovations », « éco-technologies » et « écotechs » (ces deux derniers termes calquant les néologismes anglais ecotechnology et ecotech). Les portefeuilles ministériels utilisent l'intitulé « technologies vertes » (calque du néologisme anglais green technology).

Essays on the Role of Policy and Venture Financing in Clean Technology Innovation

Matthias David van den Heuvel

This thesis aims to provide novel analyses and data that improve the understanding of the financing of investments in clean technologies. In particular, this thesis explores the role that private and public actors play in supporting young innovative firms. The first chapter of this thesis exploits original data on about 1000 startups that have participated in Venture Kick, the leading Swiss venture competition. We study the circumstances under which venture competitions' certification and cash prize impact startups' future survival and funding prospects. On the one hand, we observe that the certification only has a significant effect on startups whose quality can be more objectively assessed by experts (e.g., hard sciences startups). On the other hand, we find that the competition's cash prize only extends the runway of startups with low running costs (e.g., internet & mobile). These results highlight industry-specific heterogeneity in the effect of early-stage startup support, which bears implications for the design of entrepreneurial programs.The second chapter takes a step back and looks into the role of two prominent actors involved in financing new clean technologies: venture capital (VC) and governments. This essay examines the reasons behind the failure of the VC boom in clean energy startups in the early 2010s. We find that lackluster demand for clean energy products and a lower potential for outsized returns make clean energy firms less attractive to VC than startups in ICT or biotech. Conversely, characteristics such as high-capital intensity or long development timeframe seem to be less important. These findings suggest that the most effective way for governments to improve the attractiveness of early-stage clean energy investments is to implement demand-side policies rather than to provide direct financial support. With demand-side policies in place, governments could then try to plug the remaining funding gaps themselves by targeting startups with limited potential for outsized returns.In the second half of this thesis, the focus shifts onto governments' environmental policies and how they affect private investments in clean technologies. In the third chapter, we develop novel news-based indices of US environmental policy using text-mining techniques. We show that our general environmental policy index and sub-topic indices (e.g., renewables or climate negotiation) meaningfully capture the evolution of environmental policy in the United States. Using these indices, we find that greater salience of environmental policy is associated with increased VC investments in clean technologies and reduced stock returns for high-emissions firms. In the fourth and last chapter, we study the impact of policy uncertainty on private investment decisions. To do so, we construct a novel index of environmental policy uncertainty (EnvPU). This index reveals that uncertainty is pervasive in the history of environmental policy and is often synchronized with election cycles. We find that increases in our EnvPU index are associated with lower VC investments in cleantech startups and higher volatility in green firms' stocks. The findings from Chapters 3 and 4 suggest that, while the increased salience of environmental policy can boost investments, policymakers should ensure that their actions do not exacerbate policy uncertainty and hinder investments towards a low-carbon economy.

EPFL2022

Energy Harvesting in Microscale with Cavitating Flows

Morteza Ghorbani, Yusuf Leblebici, Ali Mohammadi, Ahmad Reza Motezakker, Luis Guillermo Villanueva Torrijo

Energy harvesting from thermal energy has been widely exploited to achieve energy savings and clean technologies. In this research, a new cost-effective and environment-friendly solution is proposed for the growing individual energy needs thanks to the energy application of cavitating flows. With the aid of cavitating jet flows from microchannel configurations of different sizes, it is shown that significant temperature rise (as high as 5.7 degrees C) can be obtained on the surface of the thin plate. The obtained heat energy could be integrated to a thermoelectric power generator, which can be used as a power resource for consumer devices, such as cell phones and laptops. To explore the difference in the temperature rise with different microtube diameters, namely, 152, 256, 504, and 762 mu m, and also with different upstream pressures of 10, 20, 40, and 60 bar, the cavitation flow patterns are captured and analyzed using an advanced high-speed visualization system. The analysis of the captured data showed that different flow patterns exist for different diameters of the microtubes, including a pattern shift from micro-to macroscale, which accompanied the pattern of temporal results very well.

Amer Chemical Soc2017

Investigations into the Effects of Biofuel Contaminants on Solid Oxide Fuel Cells

Hossein Madi

Solid Oxide Fuel Cells (SOFCs) have gathered considerable attention as a clean, highly efficient conversion device for the production of both electricity and heat from fuels. Due to their high operating temperatures, SOFCs do not require pure hydrogen as fuel, but exhibit a high fuel flexibility, a major advantage concerning the high cost of hydrogen production. Nonetheless, certain requirements apply in terms of fuel purity. The presence of contaminants such as sulfur compounds, siloxanes, halogens, volatile organic compounds and tars within the fuel stream, even at trace levels can significantly reduce the lifetime of key components such as the fuel cell stack and reformer. Cleaning technologies can remove harmful impurities from the biofuels so as to meet the cleanliness requirements of SOFC stacks, though these come at higher cost. The purpose of this study is to provide guidelines regarding the maximum impurity concentrations in the biofuels which SOFCs can tolerate. This work has two principal aims: (i) to identify any threshold tolerance limits of different contaminants, if they exist and (ii) to investigate degradation mechanisms caused by contaminants. Siloxane D4, hydrogen chloride and sulfur were selected as biogas impurities. In addition, the effect of toluene (a common impurity in wood gasifier product gas) was also investigated on the performance of Ni-YSZ SOFCs. Short tests lasting 100-500 h were carried out to study the influence of the selected impurities on state-of-the-art Ni anode-supported SOFCs. Experiments were performed on single cells provided by Topsoe Fuel Cell (TOFC) and SOLIDpower and in some cases on 11-cell short stacks, provided by TOFC. Contamination tests were performed on simple hydrogen feed and more complex feeds such as simulated biogas or reformed biogas. Furthermore, in the cases of contamination with siloxane D4 and hydrogen chloride, single cell results were compared with those of short stacks. In-situ (electrochemical impedance spectroscopy- EIS) and ex-situ (electron microscopy and chemical analysis) characterization methods were used to identify the prevailing degradation mechanisms. Suggestions were made, which Ni-YSZ anode processes are affected by each contaminant. Siloxane deposit as SiO2 and block electrode pores and TPB (triple-phase-boundary) electrochemical reaction zone; HCl adsorbs on Ni particles to hinder the electrochemical reaction; sulfur, both from H2S and thiophene, adsorbs reversibly on Ni and leads to an immediate sharp cell voltage drop, which remains small at low S-concentrations. It was found that the complete removal of siloxanes is necessary, that S-compounds are acceptable to a level of 0.5 ppm and that there is no need to remove HCl and tar compounds from the biogas, for the concentration levels in which they are expected to be found in anaerobic digester gas.