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The luminescent solar concentrator has the potential of widespread use as a generator of electricity from sunlight well-suited for use in the urban environment owing to its adaptability in shape and coloration. The device performance is heavily dependent on the ability to transport light long distances to the edges. A common organic luminophore used in the device is based on a perylene core. In this work, we describe an overlooked effect of UV illumination on the appearance and efficiency of these devices. An additional absorption peak appears upon polymerization under intense UV in nitrogen atmosphere which significantly reduces the edge emissions from the device. The additional absorbance peak disappears after exposure to air, indicating the presence of a radical anion being formed during the UV light exposure. This suggests newly-produced LSC devices should be allowed to stand a period of time under ambient conditions before their performance characteristics are determined, which could have implications in potential future commercialization of the technology.

This study provides the first comprehensive overview of the sustainability performance of the hotel sector in the Himalayan region: Sagarmatha National Park and Buffer Zone, using both environmental, economic, and technical criteria. In particular, the performance of 45 buildings in this region were measured and quantified in terms of life cycle based carbon footprint, life cycle costs, heat loss rate, number of guests, energy consumption, and area. Buildings were classified into three types: traditional, semi-modern and modern. The statistical analysis included testing for significant differences between such categories by means of ANOVA, and determination of the correlation between the same parameters. Results show a significant difference between the buildings’ total carbon footprint and operation stage carbon footprint while, there is no significant difference between the buildings’ life cycle costs. Traditional buildings have on average the largest carbon footprint and life-cycle cost over the typical building lifespan of 50 years of building lifespan. The ANOVA tests highlight how heat loss rate, size of the building and number of tourists in the hotels are significantly different across the building types. A strong positive correlation is observed between environmental impact, economic impact and energy consumption for the household activities, and a negative correlation with the number of guests and building size. By considering several buildings, this study allows to draw new and more general conclusions about effective sustainability strategies in the whole hotel sector in the Himalayan region. In particular, it shows that reducing impacts in the operation stage should be highly prioritized, focusing on reducing energy consumption and heat loss and shifting to the use of renewable energy sources.

Industrial symbiosis (IS) is recognized as an effective practice to support circular economy and sustainable development because it is able to enhance the technical efficiency of production processes, provided IS relationships among companies remain active over the long period. However, although it has been established that IS relationships can be vulnerable to disruptive events that reduce the willingness of companies to cooperate in IS synergies, to date few contributions to the literature focus attention on the events which lead firms to interrupt IS synergies. This paper contributes to the existing literature firstly by highlighting the disruptive events affecting the willingness of companies to cooperate in IS synergies and their causes, and secondly by developing an analytical model to assess the impact of each disruption on physical and monetary flows created among companies by the IS relationship. Specifically, an enterprise input-output (EIO) model is proposed, aimed at mapping the physical and monetary flows resulting from IS synergies among companies. Through this model, disruptive events can be modeled and their impact on the above-mentioned flows can be assessed. A numerical case example illustrates how the model works and how company managers and IS facilitators could use it to evaluate to what degree their current IS relationships may be vulnerable to perturbations. The model could therefore facilitate the design of adequate countermeasures and contribute to the development of perturbation resilient IS relationships. Furthermore, policymakers could adopt the model when designing policy actions to support IS practice.

In many industries, an increasing number of firm owners tie managers’ incentives to sustainability investments. Positive rewards directly increase a manager's total pay when that manager makes sustainability investments, whereas negative rewards directly decrease a manager's pay when those investments are made. Strategic incentive design literature posits that such organizational choices also affect the decisions of a firm's competitors. This paper uses a game-theoretic framework to analyze the effects of sustainability incentives in a setting with two competing firms. In contrast to the existing literature, in the current paper sustainability investments have a demand-enhancing effect and can increase or decrease the unit cost of production, making the current framework more in line with industrial practice. The results show that a firm invests in sustainability only if the demand-enhancing effects outweigh the cost-increasing effects. More importantly, positively rewarding managers for sustainability investments is done in equilibrium only if the innovation capability of the firm is sufficiently high. However, in terms of profits, those positive rewards lead to a prisoner's dilemma. When innovation capability is lower, firm owners use negative rewards and raise their profits. Another finding is that rival firms that cooperate in determining their sustainability incentives increase their profits but do so using negative rewards. These results, which have not been reported in the literature, point to some critical trade-offs in terms of sustainability investments and firm profits when sustainability incentives are considered and are both managerially and academically relevant.

Electrical energy production from renewable energy sources and electrification of consumer energy demand are developments in the ongoing energy transition. These developments urge the demand for flexibility in low voltage distribution networks, on the one hand caused by the intermittency of renewable energy sources, and on the other hand by the high power demand of battery electric vehicles and heat pumps. One of the foremost ways to create flexibility is by using energy storage systems. This paper proposes a method to first optimize the siting, power and capacity rating, technology, and operation of energy storage systems based on the technical and economic value. Secondly the method can be used to make cost- and time-based network planning decisions between network upgrades and network upgrade deferral by energy storage systems. To demonstrate the proposed method, study cases are analyzed of five low voltage distribution networks with different penetrations of photovoltaics, heat pumps and battery electric vehicles. The optimal energy storage systems in the study cases are: flow batteries sited at over 50% of the cable length with a high capacity rating per euro. With the current state of energy storage system development, network upgrade deferral is up to 61% cheaper than network upgrades in the study cases. The energy storage systems can offer additional value by reducing the peak loading of the medium voltage grid which is not taken into account in this research.

To decrease our society’s dependence on polluting fossil resources, alternative sources for chemical and fuel production need to be developed. Organic residual streams are a renewable feedstock that can be used to replace these fossil-based fuels and chemicals. In this thesis bioelectrochemical chain elongation (BCE) has been studied to convert short chain fatty acids (SCFAs, model substrates for acidified organic residual streams) into biobased intermediate chemicals. BCE is subtype of a microbial electrosynthesis (MES) system, in which microorganisms catalyse the elongation of SCFAs and/or CO2 towards medium chain fatty acids in an electrochemical cell.Part 1 of this thesis studied the formation of valuable products from SCFAs using BCE systems. In chapter 2 it started with the proof of concept of using an electrode for the sustained chain elongation of CO2 and acetate in continuous BCE systems. Four BCE reactors were used to study the role of applied current: two were applied with 3.1 A m-2 (projected surface area of electrode) and the other two with 9.4 A m-2. n-Butyrate (nC4) was the main identified product in all reactors. The highest applied current led to the highest nC4 production rate of 0.54 g L-1 d-1 (24.5 mMC d-1). The highest concentration of nC4 reached under high current regime was 0.59 g L-1 (26.8 mMC). Trace amounts of propionate and n-caproate were also produced, but no alcohols were detected over the course of the experiments (163 days).To improve BCE and enhance production, in chapter 2 as well a literature review is provided to give insights into all the reported pathways to produce nC4 in fermentations. In fermentative chain elongation soluble electron donors, like ethanol or lactate, supply reducing equivalents and drive microbial metabolism. Since such compounds were not detected in the BCE reactors, it was hypothesised that nC4 production was limited by intermediate production and subsequent fast consumption of ethanol or lactate.This hypothesis of intermediary production of ethanol or lactate limiting BCE performance was verified in chapter 3. Both ethanol and lactate were separately introduced in triplicate BCE reactors applied with 9.4 A m-2. Both compounds did not significantly affect the rates of nC4 production. Next to these compounds, the effect of formate on nC4 production was tested. Formate injection led to acetate production and decreased nC4 production. The results suggested that formate conversion to acetate competed with acetate elongation to nC4 for electrons. This competition subsequently resulted in decreased production of nC4. To investigate role of the electrode as electron donor, the current was increased to 18.1 A m-2. This increase in applied current doubled the production rates of nC4. Hence, this chapter demonstrates that the nC4 production in our BCE systems was not limited by intermediate production of well-known electron donors, but was driven by electrode-derived electrons.For BCE to become a feasible organic waste valorisation technology, the studied substrate range needs to extend beyond acetate reduction. Therefore, in chapter 4 four different substrate feeding strategies and the subsequent product spectrum were investigated: I) acetate, II) acetate and propionate, III) acetate and n-butyrate, and IV) a mixture of acetate, propionate and n-butyrate. In phase I, nC4 was produced at 0.9 g L-1 d-1 (39.7 mMC d-1). After introduction of propionate in phase II, n-valerate (nC5) production started and sustained until medium was changed at the start of phase III. The maximum concentration of nC5 reached was 1.2 g L-1 (60.6 mMC), and the highest production rate was 1.1 g L-1 d-1 (57.5 mMC d-1) at a high carbon-based selectivity of 73.8 %. This seems contradictory to ethanol chain elongation studies in which acetate is concurrently formed leading to straight fatty acids as by-products. Upon introduction of acetate and n-butyrate, n-caproate (nC6) production started and reached a maximum concentration of 0.3 g L-1 (15.8 mMC). The nC6 formation selectivity was 83.4 % in phase III. When all the three SCFA were supplied as substrate in phase IV, nC5 was the main product (95.4%). The observed preference for propionate elongation over both nC4 formation or nC6 formation is in contrast to fermentative ethanol-based chain elongation studies.Part 2 of this thesis focusses on the extraction of the bioproducts from dilute aqueous streams using ionic liquids. The conversion of organic waste streams as renewable feedstocks into carboxylic acids (such as SCFAs but as well the medium chain fatty acids (MCFAs)) results in relatively dilute aqueous streams. These relatively low concentrations are a major bottleneck for these bioprocesses to compete with the production of platform chemicals based on fossil resources. A way to overcome this bottleneck is to extract the carboxylates from the fermentation broths using liquid- liquid extraction. Hydrophobic ionic liquids (ILs) are novel extractants which can be used for this purpose. Ionic liquids are salts comprised of ions, with relatively low melting temperatures (often below 100°C). By varying the types of ion and, for example, the branching of the ions, the physical properties of the IL, such as its hydrophobicity, can be tailored. To integrate these ILs as in situ extractants in biotechnologies, the ionic liquid should be compatible with the bioprocess.In chapter 5 the biocompatibility of the two hydrophobic ILs [N8888][oleate] and [P666,14][oleate] were investigated in a two-phase system (IL layer on top of water phase). Commonly, ILs are synthesized in organic solvents, such as toluene and ethanol. After synthesis some trace amounts of these solvents can remain in the IL. When that hydrophobic IL is placed on top of a water phase, the trace amounts of synthesis solvent can leak into the water phase. To circumvent possible toxic effects of the trace amounts of solvent in the IL, water was used as synthesis solvent. After synthesis of the two ILs, their bioprocess compatibility was assessed. Methanogenic granular sludge was placed in medium without carbon source, and on top of that medium the IL phase was placed. After 24 days the sludge was separated from the water phase and placed into fresh medium. Upon transfer of the sludge into fresh medium with acetate as substrate, [P666,14][oleate] exposed granules were completely inhibited. Granules exposed to [N8888][oleate] sustained anaerobic digestion activity, although moderately reduced. Co-ions of the starting materials of the ILs, bromide and oleate, could have remained in the IL after synthesis. Both bromide (5 to 500 ppm) and oleate (10 to 4000 ppm) were demonstrated to not inhibit methanogenic conversion of acetate. Conclusively, [P666,14] was identified as a bioprocess incompatible component and [N8888][oleate] as bioprocess compatible.For an IL to become the envisioned in situ extractants for bioprocesses, the IL needs to be regenerated and reused. In chapter 6 a concept of an IL as transport liquid is presented, in which a product (from a bioprocess) is in situ extracted into a hydrophobic IL. The subsequent extraction of the product from the IL (i.e. regeneration) does not necessarily need to take place in/at the same physical location, time and/or medium as where the extraction of product into the IL occurred. Therefore, the IL can be regarded as transport liquid of the product.To study the feasibility of this concept, the bioprocess compatible hydrophobic IL [N8888][oleate] was used for two successive cycles of i) extraction of SCFAs into the IL [N8888][oleate] and ii) regeneration of the IL. For the regeneration of the IL a novel method was described which employs microorganisms to assist in IL regeneration, naming it ‘microbial assisted regeneration’. Microbial assisted regeneration is beneficial as no additional salt is needed for both pH control of the bioprocess as well as for recovery of the products from the IL. The experiments in this chapter demonstrate the potential of using hydrophobic ILs as transport liquid between two bioprocesses. When the concept of an IL as transport liquid is coupled with the proposed microbial regeneration method, two distinct biological processes can be coupled.For BCE to become an industrial waste valorisation technology, the production needs to be improved. Although the electron transfer pathways are not unravelled yet, chapter 7 gives an overview of all the nowadays described pathways. In this way, the coupling of microbial metabolism with an electrode can be understood more. Based on these insights, several recommendations are provided to improve BCE and to render the technology mature enough to prove its potential using real acidified organic residual streams.

Understanding how the deformation history affects the retraction dynamics of viscoelastic liquid films can provide a tool to design materials. In this paper, we investigate the stretching and retraction of circular viscoelastic liquid films through finite element numerical simulations. We consider a discoid domain made of a viscoelastic liquid. Its central hole is first ‘closed’ and then released, being left free to open under the effect of inertial, surface, viscous, and elastic forces. We perform a parametric study of film retraction, aiming at understanding the effects of the physical and operating parameters on it. In particular, we consider different viscoelastic constitutive equations, namely, Oldroyd-B, Giesekus (Gsk), and Phan Thien-Tanner (PTT) models, and different values of the film initial thickness. For each liquid and geometry, we investigate the effects of the film stretching rate and of liquid inertia, elasticity, and flow-dependent viscosity on the dynamics of the hole opening.

Abstract The configuration of a latent heat thermal energy storage (LHTES) is an important factor considered by manufacturers of heat storage systems. In this study, an applicable and low-cost way of improving melting behavior in a rectangular cavity was remarked. There was a preconceived idea that with a single conductive baffle, embedded on the upper wall of the cavity, the melting rate and the amount of heat storage could improve. Therefore, for different locations as well as lengths of a baffle, the heat transfer and melting characteristic of gallium as a phase change material (PCM) in a rectangular cavity were investigated numerically. The cavity has the insulated upper and bottom walls. The sidewalls are regarded to have constant temperatures one higher and another lower than the melting point of gallium. The phase change process is modeled with the fixed grid-based enthalpy-porosity method coupled with the semi-implicit method for pressure-linked equations (SIMPLE) algorithm. The isotherm lines and streamlines, as well as the liquid fraction and Nusselt number on the hot wall, are considered to present the results at a constant Rayleigh number equal to 106. The results show the baffle imposes noticeable improvement on the melting process of gallium in a rectangular cavity by influencing the feature of convective heat transfer. Investigating the different baffle’s locations (LX/L = 0.2 to 0.9) revealed that when the baffle located at the right half of the cavity, melting initiates from the left side, the more amount of PCM melts in comparison with the other cases. Ultimately, the dimensionless location of LX/L = 0.8 demonstrates the best melting characteristic and the most final liquid fraction. The more liquid-fraction, the more energy storing concluded. It also observed a dimensionless height of LY/L = 0.4 represents the most liquid-fraction compared to the heights of LY/L = 0.2, 0.3, and 0.4.