| 1. |
- Ahrén-Moonga, Jennie, et al.
(författare)
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Levels of tumour necrosis factor-alpha and interleukin-6 in severely ill patients with eating disorders
- 2011
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Ingår i: Neuropsychobiology. - : S. Karger AG. - 0302-282X .- 1423-0224. ; 63:1, s. 8-14
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Tidskriftsartikel (refereegranskat)abstract
- Background: The underlying pathophysiology of eating disorders (ED) is dependent on complex interactions between psychological, biological and social factors. The purpose of the present study was to examine a possible increase in cytokines indicating inflammation, as measured by tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in ED patients, and to explore possible relationships between cytokines and self-reported personality traits. Methods: Female patients with severe ED (n = 26) were recruited consecutively from an inpatient clinic and were compared to age-matched healthy females (n = 12). Commercial ELISA tests developed for the measurement of serum levels of TNF-α and IL-6 were employed. Personality traits were measured using Karolinska Scales of Personality. Results: The patient group displayed increased levels of the cytokine TNF-α and a tendency towards increased IL-6 levels. Spearman's rank correlation coefficient was used to examine possible relationships between levels of cytokines and personality traits. The results showed that IL-6 levels were positively related to both somatic and psychic anxiety and to aggression scales, such as irritability and suspicion. Increased levels of TNF-α, in turn, were significantly correlated with high scores on the depression-related anxiety scale Inhibition of Aggression. However, increased levels of cytokines in the ED group did not seem to be mainly associated with symptoms of depression. Conclusion: We cannot rule out the possibility that comorbid conditions in the group contribute to the higher cytokine values. Further studies need to explore the possible influence of cytokines on the severity of ED and whether this might be mediated or moderated by specific personality traits.
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| 2. |
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| 3. |
- Bales, Chris, et al.
(författare)
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European Solar Engineering School ESES : Past and Future
- 2006
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Ingår i: Eurosun 2006. - Glasgow, Scotland.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The European Solar Engineering School ESES is a one-year masters program that started in 1999 at the Solar Energy Research Center SERC, Dalarna University College. It has been growing in popularity over the years, with over 20 students in the current year. Approximately half the students come from Europe, the rest coming from all over the globe. This paper described the contents and experiences from seven years of running the programme and the plans for adapting the programme to the Bologna process. The majority of the students from ESES have found work in the solar industry, energy industry or taken up PhD positions. An alumni group has been started that actively gives support to past, present and potential future students.
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| 11. |
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| 12. |
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| 13. |
- Broman, Lars, et al.
(författare)
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Use of nonimaging concentrators for moderate concentration of sunlight onto PV cells
- 1989
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Ingår i: 9thy European Photovoltaics Solar Energy Conference. - Freiburg, Tyskland.
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Konferensbidrag (refereegranskat)abstract
- The square cornet type nonimaging concentrator has been shown useful for moderate concentration of sunlight onto photovoltaic solar cells, since it creates no hot spots at the exit aperture. In this paper are presented the mathematical formulas on which the cornet designs are based, results from computer simulations on overall cornet performance compared with measurements as well as exit aperture intensity variations, measured optical concentration ratios under controlled circumstances, and cell temperature measurements under realistic circumstances. In an Appendix are given performance curves for a large number of cornets as determined from computer simulations, covering the useful range of concentration factors and acceptance angles.
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| 14. |
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| 15. |
- Cantos-Soto, María Elena, et al.
(författare)
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Solar Reflectors Degradation Caused by Simulated Solar Radiation
- 2012
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Ingår i: Solar PACES 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The feasibility of concentrating solar power (CSP) technologies strongly depends on the material used toachieve a suitable solar reflector. A very relevant issue nowadays is to find a cost-effective reflector materialwith appropriate optical properties, able to resist the environmental stress and, therefore, extending itslifetime. This research work is focused on evaluating the thick silvered-glass reflector’s degradation causedby solar radiation onto different solar reflector samples, exposed to both experimental settings, simulatedsunlight under accelerated conditions and solar radiation at real outdoor conditions. The experiments havebeen performed in the optical characterization and durability of solar reflectors laboratory at the PlataformaSolar de Almeria (PSA). Three different chambers were used to reproduce the entire or specifics ranges ofthe solar radiation spectrum. Samples from 6 different manufacturers were placed inside of every sunlightchamber during 2000 hours. The outdoor exposure in the PSA precincts lasted for 4000 hours.
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| 16. |
- Gomes, João, 1979-
(författare)
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Development of Concentrating Photovoltaic-Thermal Solar Collectors
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fossil fuels have greatly improved human living standards and saved countless lives. However, today, their continued use threatens human survival, as CO2 levels rise at an unprecedented pace to levels never seen during human existenceon earth.This thesis aims at gathering knowledge on solar energy in general and photovoltaic thermal (PVT) and concentrating photovoltaic thermal (C-PVT) in particular. This thesis establishes several key research questions for PVTs and C-PVT collectors and attempts to answer them.A comprehensive market study of solar thermal (ST), photovoltaic (PV) and PVT was conducted to obtain prices and performance. Simulations of the energy output around the world were conducted. A ratio between ST and PV annual output was defined to serve as a tool for comparison and plotted on a world map.A key issue for PVT collectors is how to encapsulate the solar cells in a way that, amongst other things, protects the cell from the thermal expansion of the receiver, has a high transparency, and insulates electrically while at the same time conducts the heat to the receiver. In order to be useful, this analysis must also consider the impacts on the production processes. Several prototypes were constructed, a test methodology was created, and the analysis of the results enabled several conclusions on the validity of the different silicon encapsulations methods.This thesis relies heavily on collector testing with 30 different prototypes of C-PVTs being designed and constructed. Most testing was conducted using steady state method but quasi dynamic was also carried out. From this work, several guidelines were created for the design of collectors in terms of reflector geometry, cell size, string configuration, encapsulation method and several other design aspects. These analyses were complemented with thermal simulations (COMSOL & ANSYS), string layout (LT SPICE) and evaluation of existing installations. Two novel design ideas came from this thesis work, which the author will patent in the coming year. Additionally, raytracing work has been conducted and a new reflector geometry more appropriate for C-PVTs has been found to significantly improve the annual performance. Finally, the current and future position of PVTs in the global energy market is discussed.
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| 17. |
- Gustafsson, Mattias, 1972-, et al.
(författare)
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CO2 emission evaluation of energy conserving measures in buildings connected to a district heating system : case study of a multi-dwelling building in Sweden
- 2016
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Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 111, s. 341-350
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Tidskriftsartikel (refereegranskat)abstract
- When taking action to fulfill the directives from the European Union, energy conserving measures will be implemented in the building sector. If buildings are connected to district heating systems, a reduced heat demand will influence the electricity production if the reduced heat demand is covered by combined heat and power plants.This study analyze five different energy conserving measures in a multi-dwelling building regarding how they affect the marginal production units in the district heating system in Gävle, Sweden. For CO2 emission evaluations, two different combinations of heat and electricity conserving measures are compared to an installation of an exhaust air heat pump.The different energy conserving measures affect the district heating system in different ways. The results show that installing an exhaust air heat pump affects the use/production of electricity in the district heating system most and electricity conserving measures result in reduced use of electricity in the building, reduced use of electricity for production of heat in the district heating system and an increase of electricity production.The conclusion is that electricity use in the building is the most important factor to consider when energy conserving measures are introduced in buildings within the district heating system in Gävle.
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| 18. |
- Gustafsson, Mattias, 1972-
(författare)
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Energy efficiency measures in the built environment - some aspects to consider in Sweden
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The traditional energy system as we know it today will change in the future. There is a worldwide concern about the global warming situation and there are different actions implemented to limit the consequences from, mainly, the use of fossil fuels.In this thesis, multi-unit apartment buildings have been simulated according to how the global CO2 emissions change when different energy efficiency measures are implemented. The simulated buildings have also been used to investigate how the calculated energy efficiency of a building according to Swedish building regulations varies depending on which technology for heating is used in the building and if the building has a solar PV installation or solar thermal system. When the energy efficiency of a building is calculated accord-ing to Swedish building regulations, this thesis shows that heat pumps are a favored technology compared to district heating. Another result is that electric-ity use/production within the investigated district heating system is the most important factor to consider when minimizing global CO2 emissions.This thesis also investigates how the configuration of electric meters owned by the distribution system operator affects the monitored amount of self-consumed and produced excess electricity. Finally, four local low-voltage distri-bution networks were simulated when a future charging scenario of electric vehicles was implemented.If a single-family house installs a solar PV installation, this thesis reveals that the configuration of the electric meter is important for the monitored amount of self-consumed electricity. This thesis also shows that the investigated low-voltage distribution networks can handle future power demand from electric vehicles and a high share of solar PV installations, but rural low-volt-age distribution networks will need to be reinforced or rebuilt to manage the investigated future scenarios.
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| 19. |
- Gustafsson, Mattias, 1972-, et al.
(författare)
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How the electric meter configuration affect the monitored amount of self-consumed and produced excess electricity from PV systems : case study in Sweden
- 2017
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 138, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates how the principal function of bi-directional electric meters affects the monitored amount of self-consumed and produced excess electricity for dwelling buildings connected to the grid by three phases. The electric meters momentarily record the sum of the phases or the phases individually and then summarize the recorded values to a suitable time period and is then collected by the grid owner. In Sweden, both electric meter configurations fulfill laws and regulations.The meter configuration affects the monitored distribution of self-consumed and produced excess electricity significantly for the investigated single-family house but is negligible for the investigated multi-dwelling buildings. The monitored self-consumed electricity produced by the PV installation for the single-family house varies between 24% and 55% depending on the configuration and how the inverter is installed for the investigated year. The difference in economic value for the produced electricity varies between 79.3 to 142 Euros.Due to the electric meter configuration, the profitability of PV systems will be different for identical single-family houses with identical conditions. This should be corrected for a well-functioning market. It is also important to decide how the configuration should be designed to ensure that different incentives and enablers results in desired effects.
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| 20. |
- Hansson, Monika, et al.
(författare)
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Validation of a multiplex chip-based assay for the detection of autoantibodies against citrullinated peptides
- 2012
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Ingår i: ARTHRITIS RESEARCH & THERAPY. - : Springer Science and Business Media LLC. - 1478-6354 .- 1478-6362. ; 14:5, s. R201-
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Autoantibodies directed against citrullinated proteins/peptides (ACPAs) are highly specific and predictive for the development of rheumatoid arthritis (RA). Different subgroups of RA patients, which have different prognoses and may require different treatments, are characterized by different autoantibody profiles. The objective of this study was to develop a microarray for the detection of multiple RA-associated autoantibodies, initially focusing on responses against citrullinated epitopes on candidate autoantigens in RA. Methods: The microarray is based on Phadia's ImmunoCAP ISAC system, with which reactivity to more than 100 antigens can be analyzed simultaneously, by using minute serum volumes (<10 mu l). Twelve citrullinated peptides, and the corresponding native arginine-containing control peptides, were immobilized in an arrayed fashion onto a chemically modified glass slide, allowing a three-dimensional layer with high binding capacity. The assay was optimized concerning serum dilution and glass surface, whereas each individual antigen was optimized concerning coupling chemistry, antigen concentration, and selection of spotting buffer. The performance of each peptide in the ImmunoCAP ISAC system was compared with the performance in enzyme-linked immunosorbent assays (ELISAs). Serum from 927 RA patients and 461 healthy controls from a matched case-control study were applied onto reaction sites on glass slides, followed by fluorescent-labeled anti-human immunoglobulin G (IgG) antibody. Fluorescence intensities were detected with a laser scanner, and the results analyzed by using image-analysis software. Results: Strong correlations between the ImmunoCAP ISAC system and ELISA results were found for individual citrullinated peptides (Spearman rho typically between 0.75 and 0.90). Reactivity of RA sera with the peptides was seen mainly in the anticyclic citrullinated peptide 2 (CCP2)-positive subset, but some additional reactivity with single citrullinated peptides was seen in the anti-CCP2-negative subset. Adjusting for reactivity against arginine-containing control peptides did not uniformly change the diagnostic performance for antibodies against the individual citrullinated peptides. Conclusions: The multiplexed array, for detection of autoantibodies against multiple citrullinated epitopes on candidate RA autoantigens, will be of benefit in studies of RA pathogenesis, diagnosis, and potentially as a guide to individualized treatment.
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| 21. |
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| 22. |
- Huang, Pei, et al.
(författare)
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A review of data centers as prosumers in district energy systems : Renewable energy integration and waste heat reuse for district heating
- 2020
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 258
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Tidskriftsartikel (refereegranskat)abstract
- As large energy prosumers in district energy systems, on the one hand, data centers consume a large amount of electricity to ensure the Information Technologies (IT) facilities, ancillary power supply and cooling systems work properly; on the other hand, data centers produce a large quantity of waste heat due to the high heat dissipation rates of the IT facilities. To date, a systematic review of data centers from the perspective of energy prosumers, which considers both integration of the upstream green energy supply and downstream waste heat reuse, is still lacking. As a result, the potentials for improving data centers’ performances are limited due to a lack of global optimization of the upstream renewable energy integration and downstream waste heat utilization. This study is intended to fill in this gap and provides such a review. In this regard, the advancements in different cooling techniques, integration of renewable energy and advanced controls, waste heat utilization and connections for district heating, real projects, performance metrics and economic, energy and environmental analyses are reviewed. Based on the enormous amount of research on data centers in district energy systems, it has been found that: (1) global controls, which can manage the upstream renewable production, data centers’ operation and waste heat generation and downstream waste heat utilization are still lacking; (2) regional climate studies represent an effective way to find the optimal integration of renewable energy and waste heat recovery technologies for improving the data centers’ energy efficiency; (3) the development of global energy metrics will help to appropriately quantify the data center performances.
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| 23. |
- Huang, Pei, et al.
(författare)
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Datacenters as prosumers in urban energy system : a review
- 2019
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Ingår i: Proceedings of 11th International Conference on Applied Energy, Part 3.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- As a large energy prosumer in the urban energy systems, on the one hand, datacenters consume a large amount of electricity to ensure the IT facilities and ancillary power supply and cooling systems work properly; on the other hand, datacenters produce a large amount of waste heat due to the high heat dissipation rates of the IT facilities. To date, a systematic review of datacenters from the perspective of energy prosumers, which considers both integration of the upstream green energy supply and downstream waste heat reuse, is still lacking. This study fills in this gap and provides such a review. By providing a full picture of datacenters in the urban energy systems, this study aims to search new opportunities for improving datacenter overall energy efficiency and reducing carbon emissions.
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| 24. |
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| 25. |
- Joudi, Ali, et al.
(författare)
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Energy Efficient Buildings with Functional Steel Cladding
- 2011
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Ingår i: World Renewable Energy Congress. - Linköping : Linköping University Electronic Press. - 9789173930703 ; , s. 2004-2009
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Konferensbidrag (refereegranskat)abstract
- The aim of the study is to develop a model for the energy balance of buildings that includes the effect from the radiation properties of interior and exterior surfaces of the building envelope. As a first step we have used ice arenas as case study objects to investigate the importance of interior low emissivity surfaces. Measurements have been done in two ice arenas in the north part of Sweden, one with lower and one with higher ceiling emissivity. The results show that the low emissivity ceiling gives a much lower radiation temperature interacting with the ice under similar conditions. The dynamic modelling of the roof in ice arenas shows a similar dependence of the roof-to-ice heat flux and the ceiling emissivity. A second part of the study focus on how to realise paints with very low thermal emissivity to be used on interior building surfaces.
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| 26. |
- Joudi, Ali, et al.
(författare)
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Energy efficient surfaces on building sandwich panels : a dynamic simulation model
- 2011
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 43:12, s. 3736-3736
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Tidskriftsartikel (refereegranskat)abstract
- The choice of building envelope is critical for the energy performance of buildings. The major part of the energy used by a building during its lifetime is used for maintaining a suitable interior thermal climate under varying exterior conditions. Although exterior heat radiation properties (i.e. total solar reflectivity and long wave thermal emissivity) have been well accepted to have a large impact on the need for active cooling in warmer climate, the effect of a reduced thermal emissivity on interior surfaces on the building thermal energy flux is rarely studied. This paper addresses the sensitivity of the thermal energy flux through a sandwich panel, by systematically varying the surface thermal emissivity (both interior and exterior) and total solar reflectance of exterior surface, for three geographical locations: southern, middle and northern Europe. A model is introduced for calculating the effect of both interior and exterior optical properties of a horizontal roof panel in terms of net energy flux per unit area. The results indicate potential energy saving by the smart choice of optical properties of interior and exterior surfaces.
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| 27. |
- Joudi, Ali, et al.
(författare)
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Highly reflective coatings for interior and exterior steel cladding and the energy efficiency of buildings
- 2011
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 88:12, s. 4655-4666
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Tidskriftsartikel (refereegranskat)abstract
- The effect of surface heat-radiation properties of coil-coated steel cladding material on the energy efficiency of buildings in Nordic climate is addressed by parallel temperature and energy usage measurements in a series of test cabins with different exterior solar reflectivity and interior thermal reflectivity. During one year, a number of one- or two-week experiments with air conditioner cooling and electrical floor heating were made while logging air-, radiation- and surface temperatures, energy consumption and weather conditions. Measurements show significant energy savings in the test cabins by the use of high thermal reflectivity interior surfaces both during heating and cooling and a strongly reduced cooling demand by the use of high solar reflectivity exterior surfaces. Results are interpreted within the context of a steady-state energy flux model, to illuminate the importance of surface resistance properties (radiation and convective heat dissipation).
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| 28. |
- Joudi, Ali, et al.
(författare)
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Numerical and experimental investigation of the influence of infrared reflective interior surfaces on building temperature distributions
- 2017
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Ingår i: Indoor + Built Environment. - : Sage Publications. - 1420-326X .- 1423-0070. ; 26:3, s. 355-367
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Tidskriftsartikel (refereegranskat)abstract
- Radiative properties of interior surfaces can affect not only the building heat flux but also the indoor environment, the latter of which has not been thoroughly investigated. The aim of this study is to analyse the effect of surface emissivity on indoor air and surface temperature distributions in a test cabin with reflective interior surfaces. This was done by comparing experimental and simulation data of the test cabin with that of a normal cabin. This study employs transient computational fluid dynamics (CFD) using re-normalisation group (RNG) k-epsilon model, surface-to-surface radiation model and an enhanced wall function. Boundary conditions were assigned to exterior surfaces under variable outdoor conditions. The numerical and the measurement results indicate that using interior reflective surfaces will affect the indoor air temperature distribution by increasing the vertical temperature gradient depending on the time of the day. CFD simulations with high spatial resolution results show increased interior surface temperature gradients consistent with the increased vertical air temperature gradient. The influence of reflective surfaces is potentially greater with higher indoor surface temperature asymmetry. The vertical indoor air temperature gradient and surface temperatures are important parameters for indoor thermal comfort.
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| 29. |
- Joudi, Ali, 1980-
(författare)
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Radiation properties of coil-coated steel in building envelope surfaces and the influence on building thermal performance
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies have shown that the optical properties of building exterior surfaces are important in terms of energy use and thermal comfort. While the majority of the studies are related to exterior surfaces, the radiation properties of interior surfaces are less thoroughly investigated. Development in the coil-coating industries has now made it possible to allocate different optical properties for both exterior and interior surfaces of steel-clad buildings. The aim of this thesis is to investigate the influence of surface radiation properties with the focus on the thermal emittance of the interior surfaces, the modeling approaches and their consequences in the context of the building energy performance and indoor thermal environment.The study consists of both numerical and experimental investigations. The experimental investigations include parallel field measurements on three similar test cabins with different interior and exterior surface radiation properties in Borlänge, Sweden, and two ice rink arenas with normal and low emissive ceiling in Luleå, Sweden. The numerical methods include comparative simulations by the use of dynamic heat flux models, Building Energy Simulation (BES), Computational Fluid Dynamics (CFD) and a coupled model for BES and CFD. Several parametric studies and thermal performance analyses were carried out in combination with the different numerical methods.The parallel field measurements on the test cabins include the air, surface and radiation temperatures and energy use during passive and active (heating and cooling) measurements. Both measurement and comparative simulation results indicate an improvement in the indoor thermal environment when the interior surfaces have low emittance. In the ice rink arenas, surface and radiation temperature measurements indicate a considerable reduction in the ceiling-to-ice radiation by the use of low emittance surfaces, in agreement with a ceiling-toice radiation model using schematic dynamic heat flux calculations.The measurements in the test cabins indicate that the use of low emittance surfaces can increase the vertical indoor air temperature gradients depending on the time of day and outdoor conditions. This is in agreement with the transient CFD simulations having the boundary condition assigned on the exterior surfaces. The sensitivity analyses have been performed under different outdoor conditions and surface thermal radiation properties. The spatially resolved simulations indicate an increase in the air and surface temperature gradients by the use of low emittance coatings. This can allow for lower air temperature at the occupied zone during the summer.The combined effect of interior and exterior reflective coatings in terms of energy use has been investigated by the use of building energy simulation for different climates and internal heat loads. The results indicate possible energy savings by the smart choice of optical properties on interior and exterior surfaces of the building.Overall, it is concluded that the interior reflective coatings can contribute to building energy savings and improvement of the indoor thermal environment. This can be numerically investigated by the choice of appropriate models with respect to the level of detail and computational load. This thesis includes comparative simulations at different levels of detail.
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| 30. |
- Joudi, Ali, et al.
(författare)
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Reflective coatings for interior and exterior of buildings and improving thermal performance
- 2013
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Ingår i: Applied Energy. - Oxford : Elsevier. - 0306-2619 .- 1872-9118. ; 103, s. 562-570
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Tidskriftsartikel (refereegranskat)abstract
- The importance of reducing building energy usage and thriving for more energy efficient architectures, has nurtured creative solutions and smart choices of materials in the last few decades. Among those are optimizing surface optical properties for both interior and exterior claddings of the building. Development in the coil-coating steel industries has now made it possible to allocate correct optical properties for steel clad buildings with improved thermal performance. Although the importance of the exterior coating and solar gain are thoroughly studied in many literatures, the effect of interior cladding are less tackled, especially when considering a combination of both interior and exterior reflective coatings. This paper contemplates the thermal behavior of small cabins with reflective coatings on both interior and exterior cladding, under different conditions and climates with the aim to clarify and point out to the potential energy saving by smart choices of clad coatings.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
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| 36. |
- Larsson, Stefan, et al.
(författare)
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Inomhusskidbacke i Lindvallen, Sälen
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Marknaden för inomhusskidbackar är tydligt under en kraftig expansion runt om i världen. Det finns ett 40-tal inomhusskidbackar i drift och ytterligare en rad projekt planeras. I Sverige finns hittills ingen inomhusskidbacke i drift. Det finns planer på ett mindre antal inomhusskidbackar ifrån Västernorrland och söderut. I dagsläget finns konkreta planer på större inomhusskidbackar i såväl Fränsta samt Isaberg med investeringar i storleksordningen 300 MSEK vardera, men ekonomin har gjort att byggstarten skjutits upp. Klimateffekten omnämns ofta som en drivkraft, dock kan det noteras att majoriteten av projekten innehåller mycket mer än inomhusskidbacken, i form av en rik flora av andra nöjes- och fritidsaktivteter. Beräkningar har gjorts på en 1000 m lång, 100 m bred och 250 m hög inomhusskidbacke vid Lindvallen, Sälen. Energiförbrukningen beräknas bli ca 16 kWh/m2 för kyla och uppvärmning för en backe med -3 graders lufttemperatur och året-runt-drift. Anläggningens totala energiförbrukning (inkl. snötillverkning, driftsel, skidlift mm) blir i storleksordningen 3-4 gånger större, och är bl a beroende på hur snön kommer att tillverkas och distribueras inom anläggningen. Erfarenheter verkar peka på att extern snötillverkning där den färdiga snön tillförs backen är att föredra samt att hög luftfuktighet reducerar mängden snö som måste tillföra.
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| 37. |
- Lindberg, Eva, et al.
(författare)
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Review of an International Master Programme in Solar Energy Engineering
- 2008
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Ingår i: Eurosun 2008. - Lisbon.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The European Solar Engineering School ESES is a one-year master programme that started in 1999 at the Solar Energy Research Center, SERC, Dalarna University College. The programme, run in English, consists of courses which cover passive and active solar thermal, solar energy for tropical climates, PV and PV/Hybrid system design, and have sections on topics such as economy and social aspects as well as other renewable energy sources. ESES is then finished with a research project as thesis work. Over the years the contents have been evolved and improved, and new experimental work has been introduced. The programme has been growing in popularity over the years, with over 20 students each year. Approximately half of the students come from Europe, the rest coming from all over the globe. This paper describes the contents and experiences from eight years of running the programme. The majority of the students from ESES have found work in the solar industry, energy industry or taken up PhD positions. An alumni group has been started that actively gives support to past, present and potential future students.
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| 38. |
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| 39. |
- Nordlander, Svante, et al.
(författare)
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Computer modelling of wood pellet stoves and boilers connected to solar heating systems
- 2006
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Ingår i: Proc on USB of Pellets 2006, 30 May - 1 June, Jönköping, Sweden. - Jönköping, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- When optimizing systems for wood pellet and solar heating, there is a need for realistic computer models of stoves and boilers in order to perform simulation studies. The objective of this work was to develop and verify a mathematical model for wood pellet stoves and boilers for use in system simulations with TRNSYS calculating both the energy balance and CO-emissions (carbon monoxide). Laboratory measurements have been carried out on three pellet stoves, one traditional and two with gas-liquid heat exchangers, and four pellet boilers. A mathematical two-node model of a stove was developed and implemented as a TRNSYS component. Parameters were identified for two stoves and three boilers. This new model makes it possible to perform detailed simulations with time steps less than a minute of complete wood pellet heating systems and to derive long term values, such as annual values, of efficiency and emissions for the boiler or stove in a system context under realistic conditions. In addition, parametric studies can be used in order to investigate how different operation principles and system design affect these values. The simulated energy balance of a water jacketed stove investigated in this work agreed well with measured data during both stationary and dynamic conditions.
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| 40. |
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| 41. |
- Nordlander, Svante, et al.
(författare)
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Load and Season Adapted Solar Collectors
- 2000
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Ingår i: Eurosun 2000. - Copenhagen, Denmark.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In Sweden solar irradiation and space heating loads are unevenly distributed over the year. Domestic hot water loads may be nearly constant. Test results on solar collector performance are often reported as yearly output of a certain collector at fixed temperatures, e g 25, 50 and 75 C. These data are not suitable for dimensioning of solar systems, because the actual performance of the collector depends heavily on solar fraction and load distribution over the year. At higher latitudes it is difficult to attain high solar fractions for buildings, due to overheating in summer and small marginal output for added collector area. Solar collectors with internal reflectors offer possibilities to evade overheating problems and deliver more energy at seasons when the load is higher. There are methods for estimating the yearly angular irradiation distribution, but there is a lack of methods for describing the load and the storage in such a way as to enable optical design of season and load adapted collectors. This report describes two methods for estimation of solar system performance with relevance for season and load adaption. Results regarding attainable solar fractions as a function of collector features, load profiles, load levels and storage characteristics are reported. The first method uses monthly collector output data at fixed temperatures from the simulation program MINSUN for estimating solar fractions for different load profiles and load levels. The load level is defined as estimated yearly collector output at constant collector temperature divided be yearly load. This table may examplify the results: Collector Load Load Solar Improvement type profile level fraction over flat plate Flat plate DHW 75 % 59 % Load adapted DHW 75 % 66 % 12 % Flat plate Space heating 50 % 22 % Load adapted Space heating 50 % 28 % 29 % The second method utilises simulations with one-hour timesteps for collectors connected to a simplified storage and a variable load. Collector output, optical and thermal losses, heat overproduction, load level and storage temperature are presented as functions of solar incidence angles. These data are suitable for optical design of load adapted solar collectors. Results for a Stockholm location indicate that a solar combisystem with a solar fraction around 30 % should have collectors that reduce heat production at solar heights above 30 degrees and have optimum efficiency for solar heights between 8 and 30 degrees.
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| 42. |
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| 43. |
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| 44. |
- Nordlander, Svante, et al.
(författare)
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PRESIM - a graphical interactive preprocessor for modular simulation programs
- 1989
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Ingår i: ISES Solar World Congress. - Kobe, Japan.
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Konferensbidrag (refereegranskat)abstract
- PRESIM is a computer program for creating, storing, retrieving and changing input data for modular HVAC programs. The user works with CAD-style tools. The program also produces system schematics and other documentation. A first release of PRESIM will produce input data for the TRNSYS program.
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| 45. |
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| 46. |
- Nordlander, Svante, et al.
(författare)
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Solvärmesystem för hög täckningsgrad - Load adapted concentrating collectors for high solar fractions
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Dagens kombisolvärmesystem för enfamiljshus har i storleksordningen 10 m2 solfångare och kan täcka i runda tal 10 ? 30 % av det årliga värmebehovet. Ökar man solfångarytan för att öka solvärmetäckningsgraden uppstår det vanligtvis en överproduktion av värme sommartid viket kan orsaka problem i form av termisk utmattning av material, att material förstörs eller att säkerhetsventiler utlöses med driftsstopp som följd. Vidare förkortas glykolens livslängd radikalt och detta kan ge följdskador såsom korrosion, beläggningar i rören och t o m igensättning av systemet. Ett sätt att undvika problemen med överhettning i solvärmesystem med hög täckningsgrad är att använda lastanpassade solfångare. Med detta menas solfångare som har en verkningsgrad som är beroende av solhöjden och varierar över året. Verkningsgraden är hög när värmelasten är hög (vanligtvis sen höst, vinter och tidig vår) medan verkningsgraden är låg då värmelasten är låg (vanligtvis sen vår, sommar och tidig höst). I denna rapport visas att det är möjligt att bygga lastanpassade solfångarsystem med hög täckningsgrad för enfamiljshus med solfångarytor som täcker hela villatak (>= 40 m2), utan att den termiska påfrestningen på systemet blir större än för vanliga solvärmesystem med 10 m2 plana solfångare. Detta kan göras med samma systemkomponenter som finns i system med plana solfångare. De lastanpassade solfångarna levererar ungefär samma energimängd per m2 som plana solfångare, men de bör kunna bli billigare, på grund av lägre materialkostnad. Det finns även en potential att konstruera lastanpassade solvärmesystem med begränsad stagnationstemperatur, vilket kan möjliggöra användandet av billigare material. En och samma solfångartyp är lämplig för såväl stora som små system och för olika takvinklar. I rapporten redovisas optimerade solfångargeometrier för lastanpassade solvärmesystem, geometrier och optiska egenskaper för praktiskt möjliga solfångare samt beräkningar av förväntat årsutbyte, stagnationstemperaturer, stagnationstider och kostnader. Testresultat för två prototyper av lastanpassade solfångare presenteras. Optimeringsalgoritmer för design av optiken för lastanpassade solfångare i system samt ett ray-tracingverktyg och snabba men ändå tillräckligt noggranna simuleringsverktyg har utvecklats.
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| 47. |
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| 48. |
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| 49. |
- Perers, Bengt, et al.
(författare)
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Solceller 1996
- 1996
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Rapport (övrigt vetenskapligt/konstnärligt)
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| 50. |
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