Life cycle assessment of PEM FC applications: electric mobility and μ-CHP

Abstract

Polymer electrolyte membrane fuel cells (PEM FCs) are seen as a suitable technology supporting the transformation towards decarbonised societies. Decision makers face the problem that there is no sound basis of the environmental performance of cutting edge technology available. We developed a comprehensive product system for two types of high temperature (HT) PEM FCs and conducted a life cycle assessment. One system utilizes functionalized multiwalled carbon nanotubes (MWCNTs) as carbon support materials for platinum. The reference product applies carbon black. MWCNTs render possible platinum savings of 27% simultaneously retaining equal performance parameters as for the reference FC.The inventories include all components of a FC starting with the production of the carbon support material, the catalyst powder with platinum nanoparticles, a membrane, a gas diffusion layer, bipolar flow plates up to the FC stack and the FC unit including end of life treatment. Our analysis shows that platinum is the key material in HT PEM FCs and the benefits from platinum savings outweigh by far the impacts on the MWCNT production. The HT PEM FC was adjusted such that it typifies (1) a PEM FC for an electric vehicle (FCEV) allowing comparison with internal combustion engine vehicles (ICVs) and battery electric vehicles (BEVs) or (2) a PEM FC suitable for micro-combined heat and power (m-CHP) to be compared with a Stirling engine. We found an environmental advantage of a FCEV vis-à-vis the ICV, but only if hydrogen is produced with renewable electricity. We found similar environmental impacts for the FCEV and the BEV when both vehicles are propelled with renewable energy. Both m-CHP plants produce similar amounts of useful energy and have comparable environmental performance. Nonetheless, the PEM FC produces more electricity (less heat) than the Stirling engine. System expansion such that both systems deliver equal amounts of electricity and heat resulting in an advantage of nearly 20% for the PEM FC powered system. Thus, the PEM FC technology offers great potential to reduce a personal environmental (and carbon) footprint -a prerequisite on the way of a transformation to more sustainable societies. Broader contextThe prospect of changing electricity production from nuclear and fossil to predominantly renewable energy carriers as planned for example in Switzerland or Germany leads to new requirements of the electricity grid and a new electricity supply pattern. Renewable energy sources release energy congenitally intermittent over diurnal and annual cycles. The PEM FC technology can support the energy turnaround manifold. For individuals our results show that fuel cell electric vehicles provide an environmentally benign technology for individual mobility. PEM FCs in combined heat and power plants are efficient devices to convert a fuel into electricity and heat for housing applications. Both fields of application provide great potential to reduce the individual environmental footprint. Decision makers planning a nationwide strategy...

Green and Clean: Reviewing the Justification of Claims for Nanomaterials from a Sustainability Point of View

“…For the polymer sector, non-renewable energy use has been included in the impact assessment in the studies of [27,28], abiotic depletion has been included in the study from Hervy et al [26] and an overall impact indicator (through the subjective aggregation of 17 impact categories) in the study of Notter et al [29]. In all these studies the results of these impact categories follow the same trend as carbon emissions.…”

“…Bio-based or biodegradable polymers have the potential to replace conventional petrochemical plastics [27], high-strength polymer nanocomposites can replace steel, aluminum, or other metals in industrial applications [25,26] and also, they can be used in the production of alternative fuel cells [29]. Results obtained from the reviewed studies vary in terms of carbon emissions of nanomaterial-based polymers compared to alternative technologies.…”

“…The LCA phases include the goal and scope definition, inventory analysis, impact assessment and interpretation. In 9 of the studies reviewed, the ISO standards are followed and described in their methods section [17,19,20,22,[26][27][28][29][30]. The other studies describe aspects that are common to ISO-LCA (such as inventory data and impact assessment methods), but do not specifically refer to the ISO standards.…”

“…That is the main driver for a better performance compared to the alternative. In the study of Notter et al [29], the use of multiwalled carbon nanotubes reduces the platinum use in fuel cells (FCs). The MWCNT PEM (polymer electrolyte membrane) FCs perform better compared the alternative carbon black in terms of overall environmental performance and the key driver for that are the benefits from platinum savings.…”

“…In the study of Pietrini et al [27] the use of nanoscaled organophilic montmorillonite PHBs (poly3-hydroxybutyrate) resulted in a better carbon impact in the case of CRT monitors (using HIPS) and in a comparable carbon impact in the case of car body panels (using GF-PP). In the study of Notter et al [29], multiwalled carbon nanotubes are used in the production of polymer electrolyte membrane fuel cells (PEM FCs). PEM FCs used in vehicles result in comparable carbon emissions with battery electric vehicles when the energy mix is renewable-based, and they perform worse when the EU energy mix is used.…”