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Abstract While it is generally accepted that our fossil fuel-dominated energy systems must undergo a sustainable transition, researchers have often neglected the potential impacts of this on water and land systems. However, if unintended environmental impacts from this process are to be avoided, understanding its implications for land use and water demand is of crucial importance. Moreover, developed countries may induce environmental stress beyond their own borders, for instance through extensive imports of bioenergy. In this paper, Germany serves as an example of a developed country with ambitious energy transformation targets. Results show that in particular, the politically-driven aspiration for more organic farming in Germany results in a higher import quota of biomass, especially biofuels. These imports translate into land demand, which will exceed the area available in Germany for bioenergy by a factor of 3–6.5 by 2050. As this will likely bring about land stress in the respective exporting countries, this effect of the German energy transformation ought to be limited as much as possible. In contrast, domestic water demand for the German energy system is expected to decrease by over 80% through 2050 due to declining numbers of fossil-fuelled power plants. However, possible future irrigation needs for bioenergy may reduce or even counterbalance this decreasing effect. In addition, energy policy targets specific to the transport sector show a high sensitivity to biomass imports. In particular, the sector-specific target for greenhouse gas reductions will seemingly promote biomass imports, leading to the above-described challenges in the pursuit of sustainability.

AbstractThis study describes the relationships between climate change and the concept of a circular economy, outlining the need for synergies within a company's context. It reports on a bibliometric analysis of the relations between climate change and circular economy, and it provides evidence and assessments based on a sample of 11 large companies in the chemical industry. The results show that there is a concern in the academic literature to discuss circular economy efforts to combat climate change, reduce carbon emissions, strengthen the supply chain, assess the life cycle of products, their environmental impact, and waste management, and identify barriers to implementing the circular economy. In addition, there is a close association between the CE concept and tackling climate change in how organisations report their practices to the stakeholders, in considering concepts of recycling, reusing, adopting renewable energy, seeking resource efficiency, and rethinking strategies. The study concludes by providing some suggestions that may assist companies in intensifying their efforts to reduce their carbon footprint, combining them with more circular business models. Efforts from interested stakeholders must focus on defining CE in a more detailed manner, as well as its implementation at the different stages of production and consumption, especially in operations for which no uniform approach or common practice can be established. In this context, implications for positive social and environmental impacts by promoting a faster and more proactive climate transition in the chemical sector are presented. The novelty of this paper relies on the fact that it advances knowledge on matters related to the circular economy under a climate change context, identifying current trends and suggesting some measures which may optimise current business practices of the chemical sector.

La transició dels sistemes energètics cap a tecnologies energètiques renovables amb baixes emissions de carboni és una mesura clau per mitigar el canvi climàtic. La Unió Europea (UE) ha establert l’objectiu d’aconseguir una reducció d’emissions de gasos d’efecte hivernacle (GEH) del 80% al 95% l’any 2050. El biogàs ha demostrat tenir un potencial important com a font d'energia renovable per a aplicacions industrials i domèstiques i una solució eficient a la crisi energètica global. També pot ajudar a resoldre el problema de la gestió de residus en convertir els materials orgànics de rebuig en energia, i reduir l’ús d’abocadors i les emissions associades de metà, un potent gas d’GEH. Aquest projecte es centra en l’avaluació ambiental de les emissions GEH associades a la producció de biometà liquat en una planta de gestió i producció de biogàs. La metodologia que s’utilitza per calcular la petjada de carboni de la planta és l’Anàlisi del Cicle de Vida (ACV) segons les normatives ISO 14040-44:2006, i la normativa relativa al càlcul de la petjada de carboni de producte ISO 14067:2019. A més, l’avaluació ambiental també inclou el criteri de tall o “Cut-off” per ometre etapes de cicle de vida no rellevants, tipus d’activitats, processos i productes específics; i la metodologia d’aplicació de crèdits o metodologia de càrrega evitada, que consisteix en comptabilitzar com crèdits les emissions que es deixen d’emetre en la producció de biometà en lloc de produir metà d’origen fòssil. Per altra banda, els resultats obtinguts de l’ACV es contraposen amb dades provinents d’eines de càlcul d’emissions de CO2 així com estudis científics rellevants en el camp del biogàs, amb l’objectiu de validar els resultats.

Abstract The rapid uptake of renewable energy sources requires new forms of flexibility in electricity systems, including a more responsive demand-side. The social acceptability, scale and economic value of flexible demand remain subjects of conjecture. In this paper we inform this debate with a multi-methods approach using three instruments: surveys, observations and modelling. This multi-method approach brings out similarities and differences between Germany and Great Britain in relation to demand-side flexibility. Participants in both countries express a high willingness to participate in time variant tariffs, but their implementation may need to be context specific. In Germany national peak demand occurs at midday, when PV generation results in lower emission factors. Conversely, British peak demand is in the early evening when emission factors are at their highest. The differences in responses allow us to explore important technical and cultural differences affecting the need for flexibility. Germany gains most from flexibility during the daytime in summer, while flexibility in Great Britain contributes most during winter evenings. We observe high degrees of acceptability of time-variant electricity tariffs (55%) and willingness to shift demand is high, resulting in peak demand reductions of up to 14.5%. However, the resulting cost and carbon savings of these efforts is less than 2% in both countries. We conclude that short term carbon or cost savings may be less powerful motivators for load shifting measures than long term system decarbonisation.

With the increasing demand for clean and renewable energy sources, the need for reliable offshore wind technologies is undeniable. Given the elevated costs of maintenance at sea, it is crucial to ensure the proper functioning of each of the components of the machine, therefore, proper validation is essential. This thesis presents a methodological approach on the validation of one of the actuators from the yaw system, responsible of keeping the turbine facing the wind at all times. Each actuator is comprised of an electric motor and a variable frequency drive (VFD), which have been tested in a back-to-back test bench, property of GE VERNOVA. First, two small motors have been evaluated to obtain their internal parameters and familiarise with the tools and procedures. Then, two 7.5 kW motors have been studied to ensure that they are capable for implementation in the wind turbine, and they have been compared to find the better candidate. The results have shown that the Bonfiglioli BE160M seems to present better features that the Nord 160M/6CUS in terms of torque capabilities, efficiency, and size. Nevertheless, more testing is desired to corroborate the results. In conclusion, opting for the Bonfiglioli motor could potentially improve the performance of the GE VERNOVA offshore turbines. As future work, it would be interesting to support the findings by simulating real wind loads on the back-to-back test bench and analysing thermal properties of each motor.

Abstract Behavior change towards sustainable lifestyles such as adoption of renewable energy technologies is a significant element in the fight against anthropogenic climate change. Increasingly, private households can be observed to take up different renewable energy technologies; however, the introduction of these technologies is not accompanied by a broader adoption of pro-environmental behaviors, as recent studies have shown. At the same time, group settings and social capital seem to promote the uptake of wide-ranging sustainability measures. Six case studies were conducted among different sustainable community projects in Germany to shed light on why and how broad sustainability transformation in such settings comes about. Findings suggest that successful implementation of wide-ranging sustainable measures and changes in behaviors in community settings result from motivations that originate from an interplay of social needs, social capital, social norms, and environmental concern. Strong environmental attitudes, not among all, but a critical mass of members and key individuals are necessary. The desire for community and other motives, along with social influence and social norms push individuals with low environmental concern to participate in sustainable endeavors.

AbstractThe preparation of nanomaterials for energy applications such as intercalation batteries and materials that can act as substrates for water oxidation is a subject of major interest nowadays. In this work, we report the deposition of Prussian blue (PB) and its cobalt analogue (CoPBA) on mesoporous titania thin films (MTTF) using the successive ionic layer adsorption reaction (SILAR) technique under soft conditions. A bifunctional ligand, 1,10‐phenanthroline‐5,6‐dione (pd), was used to functionalize the titania surface and promote the growth of PB and CoPBA. The resulting PB@MTTF and CoPBA@MTTF nanocomposites were characterized using several techniques and it was determined that PB and CoPBA grow in a controlled and sequential manner, maintaining the mesoporous architecture. Both PB@MTTF and CoPBA@MTTF demonstrated very good electroactive properties, while CoPBA@MTTF exhibited water oxidation capabilities. The flexibility of this PBA@MTTF platform allows the incorporation of any labile transition metal ion or fragment into the structure of the coordination polymer embedded into a mesoporous matrix, opening the door for (photo)electrochemical devices and catalysts.

[eng] Developing advanced and efficient electrocatalytic energy conversion systems is of great and practical significance for propelling the efficient development of clean energy for the construction of new low-carbon power systems. Among them, electrocatalytic reduction reactions driven by renewable electricity to transform biomass-derived chemicals into biofuels and high value-added chemicals provide an effective way to improve the H/C ratio of biomass-derived chemicals and the stabilizations of bio-oil systems. However, the electrocatalytic reduction of organic compounds is more intricate compared to the electrocatalytic reduction of water molecules. It involves the adsorption of various organic functional groups, multi-step electron transfer, and the generation of organic intermediates. Meanwhile, organic electrocatalytic reduction calls for designing efficient, highly selective, and cost- effective electrocatalysts. During a series conversion process of raw biomass, aldehydes are believed to be particularly troublesome for the aldol condensation and polymerization reactions. To avoid them, hydrogenation processes are necessary. As an alternative to traditional high-pressure and -temperature processing, we choose electrochemistry that can operate in ambient conditions for the conversion of benzaldehyde (BZH), which was chosen as a typical biomass-derived chemical. Another reason for choosing BZH is that the hydrogenation products benzyl alcohol (BA) and hydrobenzoin (HDB) are important industrial chemicals. Based on the mentioned above, this work seeks to design highly efficient and high selective catalysts for the electrocatalytic conversion of the carbonyl group of BZH into BA, HDB or benzoic acid (BZA) in aqueous solution at pH＞5 (avoiding the deoxygenation product toluene). Additionally, this work screens the optimal reaction conditions for various products and speculates their most probable reaction pathways. Chapter 4 focused on the electrocatalytic reduction of BZH into BA. Pd nanoparticles supported on a nickel metal-organic framework (MOF), Ni-MOF-74, are prepared and their activity towards the ECH of BZH in a 3M sodium acetate-acetic acid (pH 5.2) aqueous electrolyte is explored. An outstanding ECH rate up to 283 µmol cm-2 h-1 with a Faradic efficiency (FE) of 76% is reached. Besides, higher FEs of up to 96% are achieved using a step-function voltage. Materials studio and density functional theory calculations show these outstanding performances to be associated with the Ni- MOF support that promotes H-bond formation, facilitates water desorption, and induces a favorable tilted BZH adsorption on the surface of the Pd nanoparticles. In this configuration, BZH is bonded to the Pd surface by the carbonyl group rather than through the aromatic ring, thus reducing the energy barriers of the elemental reaction steps and increasing the overall reaction efficiency. Chapter 5 focused on the electrochemical reduction of self-coupling of BZH to HDB using semiconductor electrocatalysts with nanosheet morphologies. The effects of electrode potential and electrolyte pH on BZH self-coupling reaction were comprehensively studied on several semiconductor electrocatalysts. A correlation is observed between their band gap and the electrochemical potential necessary to maximize selectivity towards HDB in alkaline medium, which we associate with the charge accumulation at the semiconductor surface. N-type CuInS2 provides the highest conversion rate at 0.3 mmol cm−2 h−1 with a selectivity of 98.5% at -1.3 V vs. Hg/HgO in aqueous alkaline solution pH=14. Additional density functional theory calculations demonstrate a lower kinetic energy barrier at the CuInS2 surface compared with graphitic carbon, proving its catalytic role in the self-coupling reaction of BZH. Based on the previous two works, we realize that even when selecting materials with poor HER performance, different voltages and pH values have a significant impact on the selectivity of HDB. This drives us towards the rational design of electrocatalysts for these two different reaction pathways. Chapter 6 employed material with exposed active sites Cu2S and the material Cu2S-OAm with ligands capped to catalyze the electrocatalytic reduction reaction of the biomass platform molecule BZH convert into BA and HDB. Cu2S particles are used as electrocatalysts for the BZH electrochemical conversion. We particularly analyze the effect of surface ligands, oleylamine (OAm), on the selective conversion of BZH to BA or HDB. The effect of the electrode potential, electrolyte pH, and temperature are studied. Results indicate that bare Cu2S exhibits higher selectivity towards BA, while OAm-capped Cu2S promotes HDB formation. This difference is explained by the competing adsorption of protons and BZH. During the BZH electrochemical conversion, electrons first transfer to the C in the C=O group to form a ketyl radical. Then the radical either couples with surrounding H+ to form BA or self-couple to produce HDB, depending on the available H+ that is in turn affected by the electrocatalyst surface properties. The presence of OAm inhibits the H adsorption on the electrode surface therefore reducing the formation of high-energy state Had and its combination with ketyl radicals to form BA instead promotes the outer sphere reaction for obtaining HDB. Finally, we turn our attention to the anodic reaction in chapter 7. The electrooxidation of organic compounds offers a promising strategy for producing value-added chemicals through environmentally sustainable processes. A key challenge in this field is the development of electrocatalysts that are both effective and durable. In this study, we grow gold nanoparticles (Au NPs) on the surface of various phases of titanium dioxide (TiO2) as highly effective electrooxidation catalysts. Subsequently, the samples are tested for the oxidation of BZH to BZA coupled with a hydrogen evolution reaction (HER). We observe the support containing a combination of rutile and anatase phases to provide the highest activity. The excellent electrooxidation performance of this Au-TiO2 sample is correlated with its mixed-phase composition, large surface area, high oxygen vacancy content, and the presence of Lewis acid active sites on its surface. This catalyst demonstrates an overpotential of 0.467 V at 10 mA cm-2 in a 1 M KOH solution containing 20 mM BZH, and 0.387 V in 100 mM BZH, well below the oxygen evolution reaction (OER) overpotential. The electrooxidation of BZH not only serves as OER alternative in applications such as electrochemical hydrogen evolution, enhancing energy efficiency, but simultaneously allows the generation of high-value byproducts such as BZA [spa] El desarrollo de sistemas de conversión de energía electrocatalítica avanzados es crucial para la energía limpia y un sistema energético de bajo carbono. La reducción electrocatalítica de productos químicos de biomasa mejora la relación H/C y estabiliza los aceites biológicos, aunque es compleja debido a la transferencia de electrones y generación de intermediarios. Es esencial diseñar electrocatalizadores eficientes y selectivos. La hidrogenación de aldehídos en la biomasa cruda es necesaria para evitar reacciones no deseadas. Se utilizó la electroquímica para convertir benzaldehído (BZH) en productos industriales valiosos como alcohol bencílico (BA) e hidrobencoína (HDB). Este trabajo diseñó catalizadores eficientes para convertir BZH en BA, HDB o ácido benzoico (BZA) en solución acuosa con pH ＞ 5, optimizando las condiciones de reacción. En el Capítulo 4, se usaron nanopartículas de Pd en un marco metal-orgánico de níquel (Ni-MOF-74) logrando una alta eficiencia faradaica (FE) y mejor adsorción de BZH. El Capítulo 5 estudió el acoplamiento de BZH a HDB con electrocatalizadores semiconductores, destacando el CuInS₂ de tipo N por su alta selectividad y eficiencia. En el Capítulo 6, se usaron partículas de Cu₂S con y sin oleylamine (OAm), mostrando que OAm promueve la formación de HDB al inhibir la adsorción de protones. El Capítulo 7 se enfocó en la electrooxidación de BZH a BZA usando nanopartículas de oro (Au NPs) en dióxido de titanio (TiO₂), logrando alta actividad y eficiencia energética, generando además subproductos valiosos. Programa de Doctorat en Electroquímica. Ciència i Tecnologia