1,721,031 research outputs found
Underground pumped hydro storage: Flatland Large-scale Electricity Supply
No full textDutch energy policy foresees a considerable role for such variable electricity sources as photovoltaic and wind energy. This thesis makes it clear that no adequate measures have been taken to account for the variability of these sources. The approach taken by the Dutch government is to extend cross-border connections, to shift demand away from peak hours and to use batteries in electric vehicles and households for energy storage. The thesis argues that the outcome of this approach is uncertain. Especially after 2023 problems with balancing demand and supply will increase, with often no other option than to use gas-fired power plants to prevent a black-out. The thesis makes it plausible that this is detrimental to the attainment of CO2 emission targets set by the Dutch government. This also means that wind turbines and photovoltaic panels have to be switched off when there is a surplus, which is detrimental to their economy. The thesis assesses other storage technologies and concludes that none is able to balance the Dutch grid adequately in the near future. Pumped hydro storage (PHS) is worldwide the dominant and most efficient technology for balancing the grid. Low-cost (or surplus) power is used to pump water up into a reservoir at elevated heights. During high demand and high prices water is released, passing through a turbine connected to a power generator. The thesis describes recent developments in PHS, including turbine technology and the changing role of PHS in the grid. The Netherlands is almost flat and lacks natural locations suitable for PHS. The only option is constructing an artificial height difference. The thesis proposes to construct a reservoir in caverns some 1,400 meters sub-surface in the Dutch region South Limburg. The idea is to circulate water between a small basin at the surface (50 ha) and the deep caverns. An underground PHS (U-PHS) project is proposed with a maximum power of 1,400 MW and a storage capacity of 8.4 GWh, which is essential to balance all wind and solar power currently planned in the Netherlands. The round trip efficiency of U-PHS is circa 80%. The details of the geological requirements, design, construction and planning are set out in the thesis. Construction will cost € 1,800 million, including all excavation costs, electro-mechanical equipment, pumps, turbines, and ground level installations. Construction will take 6 years. A cost-benefit analysis makes it clear that this project is viable and can be successfully financed through a public private partnership. Finally, the social implications of this project are discussed, including its favourable effects on employment, and the role of U-PHS in a more distant future. It is concluded that an U-PHS project is feasible. Its technology is proven, its economy is sound and its finance is within reach. It can play an important role in both the transition towards sustainable electricity and establishing the Netherlands as main European energy hub. Underground pumped hydro is also a smart way of using the underground to preserve the surface of the earth - wherever in the world
CO2 Capture and H2 Production: Assessment of Two Key Components for Synthetic Renewable Fuels
No full textThe transition toward a carbon-neutral society requires reshaping the world’s energy system. But even a world with net-zero emissions will depend on hydrocarbon fuels (but not necessarily of fossil origin), e.g., in the chemical industry or transport sector. While this requires the sequestration of CO2 from large point sources combined with storage and the application of negative emission technologies, the transition can be accelerated by implementing so-called power-to-X (PtX) technology. This technology makes it possible to convert power, in the form of renewable energy, into fuels (X) efficiently. PtX is an interesting option for the harder-to-abate sectors like aviation, maritime shipping, and the chemical industry. One possibility is using solar energy as the power source, combined with two abundant reactants, i.e., H2O and CO2, to produce carbon-neutral fuels. While technological pathways already exist to supply the two initial components, i.e., capturing CO2 from fossil power plants or the ambient air and water splitting to produce H2, the uncertainties are high regarding technical performance and economic feasibility. Therefore, the research reported in this thesis addresses the capturing and sourcing of these two critical components for producing solar hydrocarbon fuels: i) carbon dioxide obtained from the air and ii) renewable hydrogen produced from water using solar energy. The aim is to assess different routes for the supply of CO2 and H2 in terms of technological and economic performance and to identify the key challenges for bringing down the costs
Towards climate-neutral district heating in the EU
No full textAchieving the target of a climate-neutral energy system in the European Union necessitates the transition to heating solutions in buildings eliminating the use of fossil fuels. District heating is potentially an important component in this transition.
This thesis explores the role of district heating systems in a climate-neutral energy system, addressing challenges such as reduced heat demand due to thermal renovations of buildings and the phasing out of fossil fuels in district heating generation. Detailed empirical data analysis, spatial analysis and scenario-based methods with high-resolution data sets were utilised to quantify the potential demand and supply of district heating in the future. The results indicate that the demand could increase significantly compared to current levels. Large supply potentials can be expected from geothermal and biomass resources as well as from heat pumps at wastewater treatment plants or surface water. Excess heat from industrial processes will play a minor role as its potential decreases due to industrial transformation to low-carbon processes. Overall, district heating systems could be expanded and decarbonized in the future
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Underground pumped hydro storage: Flatland Large-scale Electricity Supply
No full textDutch energy policy foresees a considerable role for such variable electricity sources as photovoltaic and wind energy. This thesis makes it clear that no adequate measures have been taken to account for the variability of these sources. The approach taken by the Dutch government is to extend cross-border connections, to shift demand away from peak hours and to use batteries in electric vehicles and households for energy storage. The thesis argues that the outcome of this approach is uncertain. Especially after 2023 problems with balancing demand and supply will increase, with often no other option than to use gas-fired power plants to prevent a black-out. The thesis makes it plausible that this is detrimental to the attainment of CO2 emission targets set by the Dutch government. This also means that wind turbines and photovoltaic panels have to be switched off when there is a surplus, which is detrimental to their economy. The thesis assesses other storage technologies and concludes that none is able to balance the Dutch grid adequately in the near future. Pumped hydro storage (PHS) is worldwide the dominant and most efficient technology for balancing the grid. Low-cost (or surplus) power is used to pump water up into a reservoir at elevated heights. During high demand and high prices water is released, passing through a turbine connected to a power generator. The thesis describes recent developments in PHS, including turbine technology and the changing role of PHS in the grid. The Netherlands is almost flat and lacks natural locations suitable for PHS. The only option is constructing an artificial height difference. The thesis proposes to construct a reservoir in caverns some 1,400 meters sub-surface in the Dutch region South Limburg. The idea is to circulate water between a small basin at the surface (50 ha) and the deep caverns. An underground PHS (U-PHS) project is proposed with a maximum power of 1,400 MW and a storage capacity of 8.4 GWh, which is essential to balance all wind and solar power currently planned in the Netherlands. The round trip efficiency of U-PHS is circa 80%. The details of the geological requirements, design, construction and planning are set out in the thesis. Construction will cost € 1,800 million, including all excavation costs, electro-mechanical equipment, pumps, turbines, and ground level installations. Construction will take 6 years. A cost-benefit analysis makes it clear that this project is viable and can be successfully financed through a public private partnership. Finally, the social implications of this project are discussed, including its favourable effects on employment, and the role of U-PHS in a more distant future. It is concluded that an U-PHS project is feasible. Its technology is proven, its economy is sound and its finance is within reach. It can play an important role in both the transition towards sustainable electricity and establishing the Netherlands as main European energy hub. Underground pumped hydro is also a smart way of using the underground to preserve the surface of the earth - wherever in the world
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