| 1. |
- Fischer, Robert, 1966-, et al.
(författare)
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Energy Supply Potentials in the Northern Counties of Finland, Norway and Sweden towards Sustainable Nordic Electricity and Heating Sectors : A Review
- 2018
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Ingår i: Energies. - Basel, Switzerland : MDPI. - 1996-1073. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- The lands in the northernmost corner of Europe present contradictory aspects in their social and economic development. Urban settlements are relatively few and small-sized, but rich natural resources (minerals, forests, rivers) attract energy-intensive industries. Energy demand is increasing as a result of new investments in mining and industries, while reliable energy supply is threatened by the planned phase out of Swedish nuclear power, the growth of intermittent power supplies and the need to reduce fossil fuel consumption, especially in the Finnish and Norwegian energy sectors. Given these challenges, this paper investigates the potentials of so far unexploited energy resources in the northern counties of Finland, Norway and Sweden by comparing and critically analyzing data from statistic databases, governmental reports, official websites, research projects and academic publications. The criteria for the technical and economic definition of potentials are discussed separately for each resource. It is concluded that, despite the factors that reduce the theoretical potentials, significant sustainable techno-economic potentials exist for most of the resources, providing important insights about the possible strategies to contribute to a positive socio-economic development in the considered regions.
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| 2. |
- Fischer, Robert, 1966-, et al.
(författare)
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Optimal Sustainable Transport Solutions Integrated into a Nordic Municipal Energy System
- 2019
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Konferensbidrag (refereegranskat)abstract
- In Nordic environments the cold climate, large-scale industries, and a high share of electric heating drive energy consumption and create significant peak electricity demand in municipal energy systems. Prospects for decarbonizing the transport sector by electrification escalate these challenges, while availability and sustainability concerns limit biofuel use. Local authorities are committed to contributing to national climate goals, while considering local objectives for economic development, increased energy self-sufficiency and affordable energy costs. This research combines these goals into a multi-objective optimization problem (MOOP), and solves the MOOP by interfacing the energy systems simulation tool EnergyPLAN with a multi-objective evolutionary algorithm (MOEA) implemented in Matlab. In this way, the study generates optimal solutions for integrated electricity, heating and transport sectors and valuable insights are offered to decision makers in local authorities. Piteå (Norrbotten County, Sweden) is a typical Nordic municipality and serves as a case study for this research. Results show that CO2 emissions from the integrated system can be reduced up to 60% without a considerable increase of total annual costs, and that in the same range of emission reductions it is economically more convenient to invest in electric personal vehicles, light trucks and busses.
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| 3. |
- Grenman, Tiia
(författare)
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Dusty Globules and Globulettes
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Interstellar gas and dust can condense into clouds of very different size, ranging from giant molecular cloud complexes to massive, isolated, dark cloudlets, called globules with a few solar masses.This thesis focuses on a new category of small globules, named globulettes.These have been found in the bright surroundings of H II regions of young, massive stellar clusters. The globulettes are much smaller and less massive than normal globules. The analysis is based on H-alpha images ofe.g., the Rosette Nebula and the Carina Nebula collected with the Nordic Optical Tele-scope and the Hubble Space Telescope.Most globulettes found in different H II regions have distinct contours and are well isolated from the surrounding molecular shell structures. Masses and densities were derived from the extinction of light through the globulettes and the measured shape of the objects. A majority of the globulettes have planetary masses,<13MJ (Jupiter masses). Very few objects have masses above 100MJ≈0.1M(Solar masses). Hence, there is no smooth overlap between globulettes and globules, which makes us conclude that globulettes represent a distinct, new class of objects.Globulettes might have been formed either by the fragmentation of larger filaments, or by the disintegration of large molecular clouds originally hosting compact and small cores. At a later stage, globulettes expand, disrupt or evaporate. However, preliminary calculations of their lifetimes show that some might survive for a relatively long time, in several cases even longer than their estimated contraction time.The tiny high density globulettes in the Carina Nebula indicate that they are in a more evolved state than those in the Rosette Nebula, and hence they may have survived for a longer time. It is possible that the globulettes could host low mass brown dwarfs or planets.Using the virial theorem on the Rosette Nebula globulettes and including only the thermal and gravitational potential energy indicated that the 133 found globulettes are all either expanding or disrupting. When the ram and the radiation pressure were included, we found that about half of our objectsare gravitationally bound or unstable to contraction and could collapse to form brown dwarfs or free floating planets.We also estimated the amount of globulettes and the number of free floating planetary mass objects, originating from globulettes, during the history of the Milky Way. We found that a conservative value of the number of globulettes formed is 5.7×1010. A less conservative estimate gave 2×1011globulettes andif 10% of these forms free floating planets then the globulettes have contributed about 0.2 free floating planets per star.In the Crab Nebula, which is a supernova remnant from the explosion of a massive old star, one can find dusty globules appearing as dark spots against the background nebulosity. These globules are very similar to the globulettes we have found in H II regions. The total mass of dust in globules was estimated to be 4.5×10−4M, which corresponds to.2% of the total dust content of the nebula. These globules move outward from the center with transversal velocities of 60–1600 km s−1. Using the extinction law for globules, we found that the dust grains are similar to the interstellar dust grains. This means that they contribute to the ISM dust population. We concluded that the majority of the globules are not located in bright filaments and we proposed that these globules may be products of cell-like blobs or granules in the atmosphere of the progenitor star. Theses blobs collapse and form globules during the passage of the blast wave during the explosion.
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| 4. |
- Grenman, Tiia, et al.
(författare)
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Dusty globules in the Crab Nebula
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 599
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Tidskriftsartikel (refereegranskat)abstract
- Context. Dust grains are widespread in the Crab Nebula. A number of small, dusty globules, are visible as dark spots against the background of continuous synchrotron emission in optical images. Aims. Our aim is to catalogue such dusty globules and investigate their properties. Methods. From existing broad-band images obtained with the Hubble Space Telescope, we located 92 globules, for which we derived positions, dimensions, orientations, extinctions, masses, proper motions, and their distributions. Results. The globules have mean radii ranging from 400 to 2000 AU and are not resolved in current infrared images of the nebula. The extinction law for dust grains in these globules matches a normal interstellar extinction law. Derived masses of dust range from 1 to 60 × 10-6M⊙, and the total mass contained in globules constitute a fraction of approximately 2% or less of the total dust content of the nebula. The globules are spread over the outer part of the nebula, and a fraction of them coincide in position with emission filaments, where we find elongated globules that are aligned with these filaments. Only 10% of the globules are coincident in position with the numerous H2-emitting knots found in previous studies. All globules move outwards from the centre with transversal velocities of 60 to 1600 km s-1, along with the general expansion of the remnant. We discuss various hypotheses for the formation of globules in the Crab Nebula
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| 5. |
- Grenman, Tiia, et al.
(författare)
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History of Globulettes in the Milky Way
- 2018
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Ingår i: Astrophysics and Space Science. - : Springer. - 0004-640X .- 1572-946X. ; 363:2
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Tidskriftsartikel (refereegranskat)abstract
- Globulettes are small (radii $< 10$ kAU) dark dust clouds, seen against the background of bright nebulae.A majority of the objects have planetary mass.These objects may be a source of brown dwarfs and free floating planetary mass objects in the galaxy.In this paper we investigate how many globulettes could have formed in the Milky Way and how they could contribute to the total population of free floating planets.In order to do that we examine H-alpha images of 27 H~II regions. In these images, we find 778 globulettes.We find that a conservative value of the number of globulettes formed is $5.7\times 10^{10}$.If 10 \% of the globulettes form free floating planets then they have contributed with $5.7\times 10^{9}$ free floating planets in the Milky Way. A less conservative number of globulettes would mean that the globulettes could contribute $2.0\times 10^{10}$ free floating planets.Thus the globulettes could represent a non-negligible source of free floating planets in the Milky Way.
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| 6. |
- Nilforoush, Rasoul
(författare)
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Anchorage in Concrete Structures : Numerical and Experimental Evaluations of Load-Carrying Capacity of Cast-in-Place Headed Anchors and Post-Installed Adhesive Anchors
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Various anchorage systems including both cast-in-place and post-installed anchors have been developed for fastening both non-structural and structural components to concrete structures. The need for increased flexibility in the design of new structures and strengthening of existing concrete structures has led to increased use of various metallic anchors in practice. Although millions of fasteners are used each year in the construction industry around the world, knowledge of the fastening technology remains poor. In a sustainable society, buildings and structures must, from time to time, be adjusted to meet new demands. Loads on structures must, in general, be increased to comply with new demands, and the structural components and the structural connections must also be upgraded. From the structural connection point of view, the adequacy of the current fastenings for the intended increased load must be determined, and inadequate fastenings must either be replaced or upgraded. The current design models are generally believed to be conservative, although the extent of this behavior is not very clear. To address these issues, the current models must be refined to allow the design of new fastenings and also the assessment of current anchorage systems in practice.The research presented in this thesis consists of numerical and experimental studies of the load-carrying capacity of anchors in concrete structures. Two different types of anchors were studied: (I) cast-in-place headed anchors, and (II) post-installed adhesive anchors. This research focused particularly on the tensile load-carrying capacity of cast-in-place headed anchors and also on the sustained tension loading performance of post-installed adhesive anchors. The overall objective of this research was to provide knowledge for the development of improved methods of designing new fastening systems and assessing the current anchorage systems in practice.For the cast-in-place headed anchors (I), the influence of various parameters including the size of anchor head, thickness of concrete member, amount of orthogonal surface reinforcement, presence of concrete cracks, concrete compressive strength, and addition of steel fibers to concrete were studied. Among these parameters, the influence of the anchor head size, member thickness, surface reinforcement, and cracked concrete was initially evaluated via numerical analysis of headed anchors at various embedment depths. Although these parameters have considerable influence on the anchorage capacity and performance, this influence is not explicitly considered by the current design models. The numerical results showed that the tensile breakout capacity of headed anchors increases with increasing member thickness and/or increasing size of the anchor head or the use of orthogonal surface reinforcement. However, their capacity decreased considerably in cracked concrete. Based on the numerical results, the current theoretical model for the tensile breakout capacity of headed anchors was extended by incorporating several modification factors that take the influence of the investigated parameters into account. In addition, a supplementary experimental study was performed to verify the numerically obtained findings and the proposed refined model. The experimental results corresponded closely to the numerical results, both in terms of failure load and failure pattern, thereby confirming the validity of the proposed model. The validity of the model was further confirmed through experimental results reported in the literature.Additional experiments were performed to determine the influence of the concrete compressive strength and the addition of steel fiber to concrete on the anchorage capacity and performance. These experiments showed that the anchorage capacity and stiffness increase considerably with increasing concrete compressive strength, but the ductility of the anchor decreases. However, the anchorage capacity and ductility increased significantly with the addition of steel fibers to the concrete mixture. The test results also revealed that the tensile breakout capacity of headed anchors in steel fiber-reinforced concrete is significantly underestimated by the current design model.The long-term performance and creep behavior of the post-installed headed anchors (II) was evaluated from the results of long-time tests on adhesive anchors under sustained loads. In this experimental study, adhesive anchors of various sizes were subjected to various sustained load levels for up to 28 years. The anchors were also exposed to several in-service conditions including indoor temperature, variations in the outdoor temperature and humidity, wetness (i.e., water on the surface of concrete), and the presence of salt (setting accelerant) additives in the concrete. Among the tested in-service conditions, variations in the outdoor temperature and humidity had the most adverse effect on the long-term sustained loading performance of the anchors. Based on the test results, recommendations were proposed for maximum sustained load levels under various conditions. The anchors tested under indoor conditions could carry sustained loads of up to 47% of their mean ultimate short-term capacities. However, compared with these anchors, the anchors tested under outdoor conditions exhibited larger creep deformation and failure occurred at sustained loads higher than 23% of their mean ultimate short-term capacities. Salt additives in concrete and wet conditions had negligible influence on the long-term performance of the anchors, although the wet condition resulted in progressive corrosion of the steel. Based on the experimental results, the suitability of the current testing and approval provisions for qualifying adhesive anchors subjected to long-term sustained tensile loads was evaluated. The evaluations revealed that the current approval provisions are not necessarily reliable for qualifying adhesive anchors for long-term sustained loading applications. Recommendations were given for modifying the current provisions to ensure safe long-term performance of adhesive anchors under sustained loads.
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