2,118 research outputs found
Comparison of plasma generation behaviors between a single crystal semiconductor bridge (single-SCB) and a polysilicon semiconductor bridge (poly-SCB)
No full textA single crystal semiconductor bridge (single-SCB) has been fabricated by a micro-electro-mechanical system (MEMS) technique based on anisotropic wet etching, where an air gap replaces the oxide layer NOD used as a thermal insulating barrier in the conventional polycrystalline semiconductor bridge (poly-SCB). Upon flowing current in the single-SCB and the poly-SCB, the single-SCB exhibits a second peak of plasma generation at 500 ns, whereas that of the poly-SCB is founded at 600 ns. The results of an electrical experiment are analyzed through a finite element analysis and a simple discrete-element modeling of the thermal structure. From these investigations, it is clear that more effective heat conduction related to the plasma discharge behaviors is achieved in the single-SCB with a simpler thermal structure. (C) 2004 Elsevier B.V. All rights reserved
Risk analysis of High-Temperature Aquifer Thermal Energy Storage (HT-ATES)
No full textThe storage of heat in aquifers, also referred to as Aquifer Thermal Energy Storage (ATES), bears a high potential to bridge the seasonal gap between periods of highest thermal energy demand and supply. With storage temperatures higher than 50 °C, High-Temperature (HT) ATES is capable to facilitate the integration of (non-)renewable heat sources into complex energy systems. While the complexity of ATES technology is positively correlated to the required storage temperature, HT-ATES faces multidisciplinary challenges and risks impeding a rapid market uptake worldwide. Therefore, the aim of this study is to provide an overview and analysis of these risks of HT-ATES to facilitate global technology adoption. Risk are identified considering experiences of past HT-ATES projects and analyzed by ATES and geothermal energy experts. An online survey among 38 international experts revealed that technical risks are expected to be less critical than legal, social and organizational risks. This is confirmed by the lessons learned from past HT-ATES projects, where high heat recovery values were achieved, and technical feasibility was demonstrated. Although HT-ATES is less flexible than competing technologies such as pits or buffer tanks, the main problems encountered are attributed to a loss of the heat source and fluctuating or decreasing heating demands. Considering that a HT-ATES system has a lifetime of more than 30 years, it is crucial to develop energy concepts which take into account the conditions both for heat sources and heat sinks. Finally, a site-specific risk analysis for HT-ATES in the city of Hamburg revealed that some risks strongly depend on local boundary conditions. A project-specific risk management is therefore indispensable and should be addressed in future research and project developments.Accepted Author ManuscriptWater Resource
Improving identification of HT-ATES performance drivers and -barriers
No full textHigh temperature aquifer thermal energy storage (HT-ATES) can potentially solve the mismatch between heat supply and demand. It can provide a large scale seasonal heat storage solution. Thereby it enables an increase in full load hours of the base heat source, which can benefit project performance on both costs and emissions. However, the limited number of successful pilot projects indicates the technology has not escaped its state of infancy. There is a gap from concept to implementation, which is signified by the disagreement of experts on performance drivers and barriers of HT-ATES. This research aims to narrow the described knowledge gap, by improving identification of HT-ATES performance drivers and barriers. Thereby it strives to improve decision making of HT-ATES implementation, and further enhance future HT-ATES application in heating projects. The broad scope of research demands both a diagnostic and design-orientated approach, and fits seamlessly with a multi-criteria decision analysis. The analysis entails the stages of creating, evaluating, comparing and ranking of case-specific scenarios. Parametric variation changes the conditions for HT-ATES implementation across the scenarios. A simulation model is developed and connected to a groundwater model to apply the parametric variation, to create the different scenarios, and consequently to produce the quantitative information for further evaluation. During the stages of creating, evaluating, comparing and ranking, the methodology systematically produces new results on the opportunities and risks introduced by HT-ATES, and additionally on the HT-ATES performance drivers and barriers. The results show that HT-ATES enables the opportunity of improving project performance with respect to the internal rate of return and emissions. Groundwater impact remains the greatest risk, but it can be minimised with smart decision making. To support the decision maker and to overcome the risk of groundwater impact, the research proposes several performance-enhancing, non-explicit guidelines. The guidelines focus on realising an HT-ATES implementation, where project performance with respect to internal rate of return, emissions and groundwater impact are balanced. Thereby they explain the major HT-ATES performance drivers and barriers. The guidelines are summarised below. The decision maker is recommended to .. 1. .. minimise the uncertainty, through thorough subsurface characterization before implementation. Secondly, to focus on aquifers with a minimum depth of 200 [m] and a minimum hydraulic conductivity of 5 [m/d] 2. .. assure network return temperatures during peak demand are below expected storage temperatures 3. .. not consider project life-times exceeding 20 years 4. .. assure yearly maximum base source heat production is always lower than yearly consumer heat demand 5. .. to strive for a flat demand curve and apply peak-shaving, by means of, for example, variable heat prices Currently, the guidelines have the purpose of giving direction to the decision maker, but they will become more explicit once the methodology is improved, and the uncertainty and number of assumptions in the model is decreased.Electrical Engineering | Sustainable Energy Technolog
Transforming Ates To Ht-Ates, Insights From Dutch Pilot Project
No full textAquifer Thermal Energy Storage (ATES) systems combined with a heat pump save energy for space heating and cooling of buildings. In most countries the temperature of the stored heat is allowed up to 25-30°C. However, when heat is available at higher temperatures (e.g. waste heat, solar heat), it is more efficient to store higher temperatures because that improves heat pump performance or makes it unnecessary. Therefore, interest in HT-ATES development is growing. Next to developing new HT-ATES projects, there is also a large potential for additional energy savings by transforming ‘regular’ low-temperature LT-ATES systems to a HT-ATES. Such a transformation is tested for a greenhouse system in the Netherlands. This greenhouse has a LT-ATES system operational since 2012, and from 2015 onwards heat is stored in the warm well at temperatures up to 45°C. In this HT-ATES transformation pilot, water quality parameters are closely monitored as well as temperature distribution in the subsurface (using DTS). Together with the operators, the results from the ATES monitoring are used to continuously improve system performance. Numerical groundwater and heat flow simulations of actual and expected well pumping data are used to evaluate how well operation can be optimized. In this paper, the optimization using monitoring results and simulations is discussed as well as general and site specific lessons/conclusions for such transformations.Water Resource
Cug2 is essential for normal mitotic control and CNS development in zebrafish.
No full textBackground:
We recently identified a novel oncogene, Cancer-upregulated gene 2 (CUG2), which is essential for kinetochore formation and promotes tumorigenesis in mammalian cells. However, the in vivo function of CUG2 has not been studied in animal models.
Results:
To study the function of CUG2 in vivo, we isolated a zebrafish homologue that is expressed specifically in the proliferating cells of the central nervous system (CNS). Morpholino-mediated knockdown of cug2 resulted in apoptosis throughout the CNS and the development of neurodegenerative phenotypes. In addition, cug2-deficient embryos contained mitotically arrested cells displaying abnormal spindle formation and chromosome misalignment in the neural plate.
Conclusions:
Therefore, our findings suggest that Cug2 is required for normal mitosis during early neurogenesis and has functions in neuronal cell maintenance, thus demonstrating that the cug2 deficient embryos may provide a model system for human neurodegenerative disorders
"Put your own house in order first": local perceptions of EU influence on Romani integration policies in the Czech Republic
No full textThis article examines the influence of the European Union (EU) on the development and implementation of Romani integration policy in the Czech Republic from the perspective of those responsible for policy delivery. Based on analysis of key policy documents and research conducted in the Czech Republic, this article first examines how Romani integration became a more important issue during membership negotiations and then discusses how the criticism of the European Commission's Regular Reports was received by those responsible for implementing pro-Romani policies. Finally, the paper assesses how the status of full EU membership has impacted on integration policy. The article concludes that while funding for Romani integration projects has benefitted some groups, the overall impression of the EU is of a remote institution, quick to criticise and unwilling to practise what it preaches
Hydrogen sulfide activates TRPA1 and releases 5-HT from epithelioid cells of the chicken thoracic aorta
No full textEpithelioid cells in the chicken thoracic aorta are chemoreceptor cells that release 5-HT in response to hypoxia. It is likely that these cells play a role in chemoreception similar to that of glomus cells in the carotid bodies of mammals. Recently, H2S was reported to be a key mediator of carotid glomus cell responses to hypoxia. The aim of the present study was to reveal the mechanism of action of H2S on 5-HT outflow from chemoreceptor cells in the chicken thoracic aorta. The 5-HT outflow induced by NaHS, an H2S donor, and Na2S3, a polysulfide, was measured by using a HPLC equipped with an electrochemical detector. NaHS (0.3-3 mM) caused a concentration-dependent increase in 5-HT outflow, which was significantly inhibited by the removal of extracellular Ca2+. outflow induced by NaHS (0.3 mM) was also significantly inhibited by voltage-dependent L- and N-type Ca2+ channel blockers and a selective TRPA1 channel blocker. Cinnamaldehyde, a TRPA1 agonist, mimicked the secretory response to H2S. 5-HT outflow induced by Na2S3 (10 M) was also inhibited by the TRPA1 channel blocker. Furthermore, the expression of TRPA1 was localized to 5-HT-containing chemoreceptor cells in the aortic wall. These findings suggest that the activation of TRPA1 and voltage-dependent Ca2+ channels is involved in H2S-evoked 5-HT release from chemoreceptor cells in the chicken aorta. (C) 2016 Elsevier Inc. All rights reserved
High-Temperature Aquifer Thermal Energy Storage (HT-ATES) system for research development and demonstration on the TU Delft campus
No full textAt present, over half of all primary energy used in Europe is used for heating and cooling. Therefore, decarbonizing the heating supply is essential to achieve climate targets. Underground thermal energy storage is a key enabling technology for the energy transition to buffer the large seasonal mismatch between thermal energy demand and sustainable thermal energy production capabilities. In Delft, a High-Temperature Aquifer Thermal Energy Storage (HT-ATES) system will be installed at the campus of Delft University of Technology (TU Delft). It will be integrated in the wider heating system on and around the TU Delft campus, which itself is undergoing a transformation to optimally supply sustainable thermal energy. The district heating network will be extended and utilize the thermal energy from a geothermal doublet producing heat at around 75-80°C with a flow rate of ~350m3/hr. Excess energy produced by the geothermal well in summer will be stored in the HT-ATES system, and will be utilised when demand exceeds production throughout the winter. The HT-ATES system will comprise of 7 wells (3 hot wells of 80°C and 4 warm wells of 50°C) to a depth of approximately 200m, with storage in an unconsolidated sedimentary aquifer between 160-200m depth. It is designed so that the instantaneous excess power from the geothermal project can be stored and demand from the district heating network be extracted from the system.The HT-ATES system at TU Delft is partially funded by local stakeholders and the European commission within the PUSH-IT project and has two primary goals: (i) to reduce carbon emissions on TU Delft campus , and (ii) to create a unique demonstration, education and research infrastructure. The complexity of a HT-ATES requires innovative solutions during the entire system life cycle. The scientific programme that is initially planned within the project is therefore focusing on various research fields and includes:- Characterisation of the subsurface formations including mechanical, hydraulic, thermal, and chemical properties.- Evaluation and monitoring of the biological conditions and microbial diversity, and potential impact on water quality.- Innovations in drilling and completion, monitoring and performance.- Quantification of the system performance and system impact during multiple storage cycles and the full lifecycle of the HT-ATES. This will include extensively monitoring temperature distribution and water quality in the subsurface to characterise behaviour and improve models.- Demonstrate and develop the implementation of HT-ATES in an urban setting, including control of the system in the built-environment and transforming the conventional heat network to a future-proof heat network.- To allow access to other universities or institutions with active programmes in the field of Geothermal Science and Engineering to jointly carry out research and perform experiments.-Societal engagement and legal evaluation for improving the just energy transition.Geo-engineeringWater Resource
South Asians in the United Kingdom and specialist services
No full textChapter one is a literature review of the psychosocial factors which influence
alcohol use in British South Asian men. Critical analysis of fourteen research articles
revealed differences between first and second-generation South Asian men. The
influence of religion, parental beliefs and acculturation were reported within the
literature to affect alcohol use. The literature highlighted the issue of stigma and lack
of awareness of services as barriers for treatment seeking. Additionally, the effect of
religious and cultural beliefs of alcohol use may also discourage support from
services.
Chapter two investigated the experiences of British South Asian women who
accessed psychological treatment within a cancer service using in-depth semistructured
interviews. Key informants participated in focus groups to gain
experiences of staff who had worked with South Asian communities. Using
Interpretative Phenomenological Analysis, the findings elicited themes which
illustrated that the South Asian women held pre-existing beliefs about psychological
services. They also described their psychological journey of cancer treatment and the
impact on their family, friends and differences between generations was reported.
Analysis of the key informants' focus group data highlighted the theme of challenges
faced by the South Asian patients and the staff. This article provided evidence for
better education and awareness for South Asian communities and staff.
Chapter three is a reflective article on the process of conducting the empirical
research. The article addressed the reasons that influenced the researcher to conduct
the study. Issues that had arisen were of the effect of 'sameness and difference'
between the researcher and participants and the impact of qualitative research
methodology and empowerment. A reflection of the impact from the interview
accounts was also discussed
Business case and sensitivity analysis for the commercial use of HT-ATES systems
No full textProjections show that urban areas are growing at an increasing rate and produce 60% of the global greenhouse gas emissions (United Nations, n.d.). In Europe, the thermal energy sector consumes about half of the energy resources, of which 85% is produced by fossil fuel-based energy systems (Drijver, Bakema, & Oerlemans, 2019). As a result of this, district heating companies have set climate targets tolower the harmful emissions produced by the thermal energy sector. This can only be done by replacing fossil fuel-based energy systems by sustainable energy systems. One of the promising sustainable energy systems is the high temperature aquifer thermal energy storage (HT-ATES) system. HT-ATESis a buffer system used to store waste heat from industrial processes in a suitable aquifer and transfers this heat to buildings to heat them up in the winter and cool them down in the summer. However, this system is very complex in use and carries many risks. Due to the HT-ATES being a buffer system, complex in use and carrying many risks there are not many running projects incorporating this system. This makes the revenue model and possible exploitation for commercial use very unclear. Therefor, the goal of this thesis is to develop a business case for the commercial use of HT-ATES systems and to assess the business case sensitivity to the thermal energy demand. The research goal will be achievedby performing a literature study. Assessing the business case viability against other geothermal energy systems will not be in the scope of this thesis. This thesis is merely meant to gain insight on the business case of HT-ATES systems.The findings of the research show that a project is solely profitable when the benefit outweighs the cost. The total business expenditure of a 30-year lifecycle HT-ATES project with 3,000 households will be fixed upfront expense of EUR 1,236,991 and an additional yearly expense of EUR 695,795. The benefit of the project is strongly dependent on the thermal energy demand. The revenue model of this project consists of a heating price model and government provided subsidy. This business model assumes a heat price of EUR 3.89 per kWh and a subsidy of EUR 2.73 per kWh thermal energy produced. Assuming the annual thermal energy demand is 12.66 kWh per household, the 30-year HTATES project with a district heating network of 3,000 households will have a payback time of 8.4 years. This means that the project will be profitable after 8.4 years. A sensitivity analysis on the thermal energy demand proved that a HT-ATES will be more profitable if the thermal energy demand is higher. This sensitivity analysis also shows that the project will need to have a minimum of 1,300 households in the network in order to be financially feasible, as the payback time of less households will not be within the project lifecycle. A district heating network with a 30-year lifecycle HT-ATES system will have a payback time of 22 year. When this same network where to incorporate 4,000 households the paybacktime will be reduced by a factor of 4.Geotechnical Engineerin
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