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  • 1.
    Adsten, Monika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Perers, Bengt
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    The influence of climate and location on collector performance2002In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 25, no 4, p. 499-509Article in journal (Refereed)
    Abstract [en]

    The influence of annual climate variations on the performance of solar thermal collectors in the northern part of Europe has been investigated. The annual solar collector energy output has been calculated with the MINSUN simulation program using hourly, measured climatic data for the years 1983–98 for three cities situated in the south (Lund), central (Stockholm) and north (Luleå) of Sweden. A synthetic year created with the Meteonorm weather simulation program was also used in the simulations. Two solar thermal collectors were modelled: a flat plate solar collector and a tubular vacuum collector, both of commercial standard.

    The thermal energy output is strongly correlated to the annual global irradiation at a horizontal surface. The annual average energy delivered from the flat plate collector was 337 kWh/m2 for Stockholm (337 for Lund and 298 for Luleå), and from the vacuum tube collector 668 kWh/m2 for Stockholm (675 for Lund and 631 for Luleå) at an operating temperature of T=50°C. Maximum deviations from the average value for this 16-year period are around 20% for the flat plate and 15% for the vacuum tube collector, at T=50°C.

    The relation between global irradiation on a horizontal surface and the annually collected thermal energy at a constant operating temperature could be fitted to a linear equation: qu=aG(0°)+bT, where qu is the energy output from the collector, G(0°) the global irradiation at a horizontal surface, T the average temperature of the collector fluid, and a and b fitting parameters in a double linear regression analysis.

  • 2.
    Boström, T
    et al.
    Norut Northern Research Institute Narvik, Norge.
    Valizadeh, Sima
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lu, J
    Division of Thin Film Physics, Department of Physics, Chemistry and Biology - IFM, Linköping University, Linköping.
    Jensen, J
    Division of Thin Film Physics, Department of Physics, Chemistry and Biology - IFM, Linköping University, Linköping.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Structure and morphology of nickel-alumina/silica solar thermal selective absorbers2011In: Journal of Non-Crystalline Solids, ISSN 0022-3093, E-ISSN 1873-4812, Vol. 357, no 5, p. 1370-1375Article in journal (Refereed)
    Abstract [en]

    Nickel-alumina/silica thin film materials for the use in solar thermal absorbers have been investigated using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Elastic Recoil Detection Analysis (ERDA). The TEM images revealed that all layers have a very small thickness variation and that the layers are completely homogenous. High resolution images showed 5-10 nm (poly) crystalline nickel nano-particles. ERDA showed that both the silica and alumina compositions contain more oxygen than 2:1 and 3:2 respectively. SEM showed the surface morphology and characteristics of the top silica anti-reflection layer. Hybrid-silica has showed to generate a smoother surface with less cracking compared to pure silica. The final curing temperature revealed to be of importance for the formation of cracks and the surface morphology.

  • 3.
    Boström, T
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Westin, G
    Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Spectrally selective solar thermal absorber based on sol-gel and solution-chemistry methods2005In: SOLGEL 2005, 2005Conference paper (Other (popular scientific, debate etc.))
  • 4.
    Boström, T
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Wäckelgård, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Durability tests of solution-chemically derived spectrally selective absorbers2005In: Solar Energy Materials and Solar Cells, Vol. 89, p. 197-207Article in journal (Refereed)
    Abstract [en]

    A detailed neutron powder diffraction and calorimetric study was conducted to determine the influence of increasing Mn-substitution on the crystal and the magnetic structures of hematite, α-Fe2O3. The study was initiated to determine, if Mn substitution may be responsible for unusual ferromagnetic properties of natural hematite samples from the Kalahari Mn field, South Africa. Natural as well as synthetic Mn-bearing hematite samples with the compositional range Fe2−xMnxO3 (x=0 to 0.176) were examined. Calorimetric measurements were performed to determine the Néel TN and the Morin TM temperature transitions. All studied hematite samples, irrespective of chemical composition, display weak ferromagnetism at 295 K and coexistence of weak ferromagnetic and antiferromagnetic phases at 10 K. A slight decrease of the total magnetic moment and TM but a drastic decrease of TN can be attributed to increasing Mn-substitution. The results illustrate that Mn substitution may contribute but cannot be the sole reason for the unusual magnetic properties of natural hematite samples.

  • 5.
    Boström, T
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Wäckelgård, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Fasta tillståndets fysik.
    Experimental an theoretical optimization of a three layer solution chemically derived spectrally selective absorber2005In: ISES 2005, 2005Conference paper (Other scientific)
  • 6.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Jensen, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, G
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Proceedings of Eurosun 20062006Conference paper (Refereed)
  • 7.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Jensen, J
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics. Jonfysik.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Accelerated ageing tests of optimized solution chemically derived selective solar thermal absorbers2006Conference paper (Refereed)
  • 8.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jensen, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Valizadeh, Sima
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ERDA of Ni-Al2O3/SiO2 solar thermal selective absorbers2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 10, p. 1177-1182Article in journal (Refereed)
    Abstract [en]

    Thin film materials for the use in solar thermal absorbers have been investigated using time-of-flight energy elastic recoil detection analysis (ERDA). The ERDA measurements proved to be very efficient in detecting the elemental depth composition of a selective solar absorber. The three-layer absorber is composed of an 80% nickel-20% alumina film at the base, a 40% nickel-60% alumina layer in the middle and finally an AR film of silica or hybrid-silica film at the top. The difference between solution volume percent and actual volume percent could be investigated when studying individual nickel-alumina films with varying ratios coated on glass substrates. The result showed that there was a maximum difference of 3% between the calculated solution volume percent and the actual volume percentages in the solid films. The ERDA measurements also indicate that about 15% of the nickel found in the nickel-alumina composite films is bound in the form of NiO.

  • 9.
    Boström, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Westin, G
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Antireflection coatings for solution-chemically derived nickel-alumina solar absorbers2004In: Solar Energy Materials and Solar Cells, Vol. 84, p. 183-191Article in journal (Refereed)
  • 10.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optimization of a solution-chemically derived solar absorbing spectrally selective surface2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 1, p. 38-43Article in journal (Refereed)
    Abstract [en]

    A previously studied solution chemically derived two layer absorber has been improved by adding a third layer. Simulations done with a thin film program showed that the optimized three layer selective absorber should be composed of an 80% nickel-20% alumina film of 100 nm at the base, a 40% nickel-60% alumina film of 60 nm in the middle and finally a 100% silica film of 85 nm at the top. Experimental results confirmed the computer simulated three layer structure. Prepared absorber consisting of the theoretically found optimized layer structure achieved a solar absorptance, alpha(sol), of 0.97 and a thermal emittance, epsilon(therm), of 0.05.

  • 11.
    Boström, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Anti-reflection coatings for solution-chemically derived nickel—alumina solar absorbers2004In: Solar Energy Materials & Solar Cells, no 84, p. 183-191Article in journal (Refereed)
    Abstract [en]

    In order to suppress reflections from a solar absorber surface an anti-reflection (AR) layer is usually deposited on top of the solar absorbing coating. For the AR coating to function well it be made of a material with a lower refractive index than the underlying surface. Provided that the AR coating is sufficiently thin, it will not increase the thermal emittance value. Besides increasing the solar absorptance it is equally important that the AR layer is long term stable in order to create a successful solar selective coating. The objective was to create a highly efficient, flexible, inexpensive and durable AR coating for solar absorbers using simple techniques. Elastic properties are requested because it prohibits the formation of micro-cracks.

    Mumina, silica and hybrid silica AR coatings were synthesized using solution chemistry and )l-gel techniques. The AR coatings were deposited on the absorber surface using spin

    coating. The absorbers used without an AR layer had a normal solar absorptance of 0.79-0.81 and a normal thermal emittance of 0.03 The optimum anti-reflection coated sample acquired

    a normal solar absorptance of 0.93 while the thermal emittance remained unaltered. The study has shown that by adding a proper AR coating to a solar absorber the spectral selectivity can be considerably enhanced.

  • 12.
    Boström, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Solution-chemical derived nickel-alumina coatings for thermal solar absorbers2003In: Solar Energy, no 74, p. 497-503Article in journal (Refereed)
  • 13. Crema, L.
    et al.
    Bozzoli, A.
    Alberti, F.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hesse, S.
    Hislop, D.
    Rivolta, B.
    Luminari, M.
    Restall, B.
    Novel m-CHP generation from small scale Concentrated Solar Power2012In: World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conference, 2012, p. 735-742Conference paper (Refereed)
    Abstract [en]

    The paper describes the realization of a modular 1-3 kWe, 3-9 kWth micro Combined Heat and Power (m-CHP) system based on innovative Concentrated Solar Power (CSP) and Stirling engine technology. This CSP m-CHP will provide electrical power, heating and cooling for single and multiple domestic dwellings and other small buildings. The cogeneration of energy at distributed level is one of leading argument in large part of energy policies related to renewable energy resources and systems. The actual marketable solar systems for domestic and distributed applications (PV and Solar thermal) suffer of notable limitation: i) the low overall (electrical) efficiency of PV systems create a small collected energy from available space, sometimes restricted in surface to few square meters, ii) the stagnation temperatures on solar thermal collectors actually limiting the diffusion of solar thermal systems, iii) fixed and not retrofittable systems may generate energy in intermittent way not aligned with the auto consumption profile of domestic spaces.

  • 14. Etherden, N
    et al.
    Tesfamichael, Tuquabo
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    A theoretical feasibility study of pigments for thickness-sensitive spectrally selective paints2004In: Journal of Physics D: Appl Phys, Vol. 37, p. 1-8Article in journal (Refereed)
  • 15.
    Gelin, Kristina
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Boström, Tobias
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Thermal emittance of sputter deposited infrared reflectors in spectrally selective tandem solar absorbers2005In: Solar Energy, Vol. 77, p. 115-119Article in journal (Refereed)
  • 16.
    Gelin, Kristina
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Infrared emittance of Cu –Ni1 alloys2004In: J. Phys. Condens. Matter, Vol. 16, p. 833-843Article in journal (Refereed)
  • 17.
    Gelin, Kristina
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Infrared emittance of Ni –Cr1 alloys2004In: J. Phys. Condens. Matter, Vol. 16, p. 2129-2138Article in journal (Refereed)
  • 18. Gren, Anna
    et al.
    Glad, Wiktoria
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ellegård, Kajsa
    Karlsson, Fredrik
    Rohdin, Patrik
    Lundh, Magdalena
    Bodström, Tobias
    Löfström, Erica
    Isaksson, Charlotta
    Werner, Anna
    Persson, Mari-Louise
    Energianvändning i bebyggelse - boendes och aktörers val av teknik: Antologi från forskarskolan program energisystem2007Book (Other academic)
    Abstract [sv]

    Energianvändning är grunden för välstånd och samhällsutveckling. Men vårt sätt att använda energi orsakar miljöpåverkan som i värsta fall kan rasera grunden inte bara för välstånd och samhällsutveckling utan också ytterst för existensen av allt liv på jorden. Vilka är möjligheterna att förändra energianvändningen så att den blir miljömässigt, socialt och ekonomiskt uthållig? Detta är en process som i mycket måste utgå från vad människor gör i sin vardag, i yrkeslivet och som konsumenter och användare av energi i olika aktiviteter. Antologin behandlar energianvändning i bebyggelse utifrån de valmöjligheter som olika aktörer – professionella och hushåll – har när det gäller att bygga och bo i energisnåla hus, att installera och bruka teknik som är energieffektiv och som utnyttjar förnybar energi, till exempel solenergi.

    Boken vänder sig till alla som har professionellt intresse för frågor om energianvändning i bebyggelse som till exempel aktörer som planerar, bygger och förvaltar byggnader. Den vänder sig också till hushållen, som bor i husen och använder energi. Boken vill vidare visa hur teknisk och samhällsvetenskaplig forskning kan kombineras för att nå ny kunskap om processer i så komplexa sociotekniska system som moderna energisystem.

  • 19. Joudi, M. A.
    et al.
    Rönnelid, M.
    Svedung, H.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Energy Efficient Buildings with Functional Steel Cladding2011In: Low-Energy Architecture(LEA), 2011Conference paper (Refereed)
  • 20. Katumba, G
    et al.
    Lu, J
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Physics, Department of Physics and Materials Science, Experimental Physics.
    Olumekor, L
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Physics, Department of Physics and Materials Science, Experimental Physics. oorganisk kemi.
    Wäckelgård, E
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Physics, Department of Physics and Materials Science, Experimental Physics. Fasta tillståndets fysik.
    Low Cost Selective Solar Absorber Coatings: Characteristics of Carbon-In-Silica Synthesized with Sol-Gel Technique2005In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707 (Paper) 1573-4846 (Online), Vol. 36, p. 33-43Article in journal (Refereed)
    Abstract [en]

    Carbon-silica composite films have been fabricated using sol-gel synthesis of silica-carbon precursor composites, followed by carbonization in an inert atmosphere. Four categories of samples were studied. These were the tetraethyl orthosilicate-only (TEOS-only), methyl trimethoxysilane (MTES), acetic acid anhydride (Ac2O) and soot (SOOT) samples. The carbon-silica films, spin-coated on aluminium and steel substrates, have been investigated for selective solar absorber functionality. Optical measurements were performed on these samples to determine solar absorptance and thermal emittance of each. The morphology of the films was studied by electron microscopy. Electron energy-loss spectroscopy (EELS) mapping was used to determine the carbon distribution. An optimum performance of 0.88 for solar absorptance and 0.41 for thermal emittance has been achieved. The sol-gel technique produced films with very flat surfaces and uniform thicknesses in the 1 μm range. The fine structure showed homogeneous mixing of the carbon and silica in the TEOS-only samples while the separate additions of MTES and Ac2O resulted in segregation of composition of the silica and carbon at nano-scale. The addition of 20 wt% MTES or 15 wt% Ac2O to the TEOS-only sols also helped to reduce the cracks in the TEOS-only samples. The addition of soot in place of the carbon precursor did not yield a net advantage.

  • 21. Katumba, G.
    et al.
    Makiwa, G.
    Baisitse, T. R.
    Olumekor, L.
    Forbes, A.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solar selective absorber functionality of carbon nanoparticles embedded in SiO2, ZnO and NiO matrices2008In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 5, no 2, p. 549-551Article in journal (Refereed)
  • 22. Katumba, G.
    et al.
    Olumekor, L.
    Forbes, A.
    Makiwa, G.
    Mwakikunga, B.
    Lu, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wäckelgård, Eva
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optical, thermal and structural characteristics of carbon nanoparticles embedded in ZnO and NiO as selective solar absorbers2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 10, p. 1285-1292Article in journal (Refereed)
    Abstract [en]

    Selective solar absorber coatings of carbon embedded in ZnO and NiO matrices on aluminium substrates have been fabricated by a sol-gel technique. Spectrophotometry was used to determine the solar absorptance and the thermal emittance of the composite coatings. The surface morphology of the samples was studied by scanning electron microscopy (SEM). Cross-sectional high-resolution transmission electron microscopy (X-HRTEM) was used to study the fine structure of the samples. Chemical composition analysis was done by energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS). The crystal structure of ZnO and NiO samples was also investigated with an X-ray diffraction (XRD) technique. Samples were subjected to an accelerated ageing test for 95 h, with condensation at relative humidity of 95% and at a climate chamber temperature of 45 degrees C. The thermal emittances of the samples were 6% for the ZnO and 4% for the NiO matrix materials. The solar absorptances were 71% and 84% for ZnO and NiO samples, respectively. The SEM revealed a smooth featureless surface for both C-ZnO and C-NiO samples. Some C-NiO samples showed dentritic features. X-HRTEM, EDS and EELS studies revealed a nanometric grain size for both types of samples. The C-ZnO and C-NiO coatings contained amorphous carbon embedded in nanocrystalline ZnO and NiO matrices, respectively. Selected area electron diffraction (SAED) showed that a small amount of Ni grains of 30 nm diameter also existed in the NiO matrix. The accelerated ageing tests produced performance criterion (PC) values of 0.15 and 0.054 at 95 h for the C-ZnO and C-NiO samples, respectively. Based on these results, C-NiO samples proved to have better solar selectivity behaviour than the C-ZnO counterparts.

  • 23.
    Kubart, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Berg, Sören
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    A model of DC reactive magnetron sputtering for graded solar thermal absorbers2007Conference paper (Refereed)
  • 24.
    Kubart, Tomas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhao, Shuxi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wingqvist, Gunilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nyberg, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Berg, Sören
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A model of DC reactive magnetron sputtering for graded solar thermal absorbers2008In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 100, no 8, p. 082024-Article in journal (Refereed)
    Abstract [en]

    In this work we present process modelling of reactive in-line sputtering. Although modelling of reactive sputtering is often used, most models are based on assumptions which make them insufficient for use in this case. The presented model takes into account a realistic deposition rate profile and distribution of reactive gas pressure. The model has been applied to reactive sputter deposition of graded solar thermal absorbers. It has been shown that the presented model represents a simple alternative to complex Monte Carlo simulations while still representing all important features of the process.

  • 25.
    Lundh, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Vassileva, I
    Dahlquist, E
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Comparison beteen hot water measurements and modelled profiles for Swedish households2008In: Proceedings, 2008Conference paper (Refereed)
  • 26.
    Lundh, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Qualitative investigation of the development of combined solar and pellet heating systems in Sweden2008In: Proceedings, 2008Conference paper (Refereed)
  • 27.
    Lundh, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Solar heating - more than a technical system2008In: Proceedings, 2008Conference paper (Refereed)
  • 28.
    Lundh, M
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ellegård, Kajsa
    Design of hot water user profiles for Swedish households based on time diaries.2008In: Proceedings, 2008Conference paper (Refereed)
  • 29.
    Lundh, Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Antireflection treatment of Thickness Sensitive Spectrally Selective (TSSS) paints for thermal solar absorbers2010In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 1, p. 124-129Article in journal (Refereed)
    Abstract [en]

    There are several methods to produce solar absorbers, and one cheap alternative is painted absorbers, preferably painted with a spectrally selective paint. The optical properties of Thickness Sensitive Spectrally Selective (TSSS) paints are, however, limited by the thickness of the paint layer. In this study it is shown that the solar absorptance of two commercial TSSS paints can be increased between 0.01 and 0.02 units with an antireflection treatment using a silicon dioxide layer deposited from silica-gel. It was found that the thermal emittance (100 °C) did not change significantly after the treatment.

  • 30.
    Lundh, Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Anti-reflection treatment of TSSS paints for thermal solar absorbers2006In: Proceedings of Eurosun 2006, 2006Conference paper (Refereed)
  • 31.
    Lundh, Magdalena
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Theoretical study on solar and pellet heating systems to reduce electricity demand for residential heating2007Conference paper (Refereed)
  • 32.
    Mwamburi, Mgendhi
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Hoel, Anders
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences, Solid State Physics. fasta tillståndets fysik.
    Surface morphologies of spectrally selective and polarization-dependent angular optical reflectors of SnOx:F-coated anodized aluminium2004In: Solar Energy Materials and Solar Cells, Vol. 84, p. 381-394Article in journal (Refereed)
  • 33. Valyukh, I.
    et al.
    Green, S.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Valyukh, S.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arwin, H.
    Optical Properties of Thin Films of Mixed W-Ni Oxides Made by DC Magnetron Sputtering2010Conference paper (Refereed)
  • 34.
    Valyukh, I
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Green, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arwin, H
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optical Properties of Amorphous Tungsten Oxide Films Deposited by Reactive DC Magnetron Sputtering2009Conference paper (Refereed)
  • 35.
    Valyukh, Iryna
    et al.
    Department of Material Science, Dalarna University.
    Green, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Arwin, Hans
    Laboratory of Applied Optics, Department of Physics, Chemistry and Biology, Linköping University.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spectroscopic ellipsometry characterization of electrochromic tungsten oxide and nickel oxide thin films made by sputter deposition2010In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 94, no 5, p. 724-732Article in journal (Refereed)
    Abstract [en]

    Electrochromic films of tungsten oxide and nickel oxide were made by reactive dc magnetron sputtering and were characterized by X-ray diffraction, Rutherford backscattering spectrometry, scanning electron microscopy, and atomic force microscopy. The optical properties were investigated in detail by spectroscopic ellipsometry and spectrophotometry, using a multiple-sample approach. The W oxide film was modeled as a homogeneous isotropic layer, whereas the Ni oxide film was modeled as an anisotropic layer with the optical axis perpendicular to the surface. Parametric models of the two layers were then used to derive complex refractive index in the 300-1700-nm-range, film thickness, and surface roughness. A band gap of 3.15 eV was found for the W oxide film, using a Tauc-Lorentz parameterization. For the Ni oxide film, taken to have direct optical transitions, band gaps along the optical axis, perpendicular to it, and in an isotropic intermediate layer at the bottom of the film were found to be 3.95, 3.97, and 3.63 eV, respectively. Parameterization for the Ni oxide was made by use of the Lorentz model.

  • 36.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ellegård, Kajsa
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Markov-chain modelling of high-resolution activity patterns and household electricity demand2009In: Proceedings of the Scientific Conference on Energy Systems and IT, Älvsjö, Sweden, March 11-12, 2009, 2009Conference paper (Refereed)
  • 37.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lundh, Magdalena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Vassileva, Iana
    School of Sustainable Development of Society and Technology, Mälardalen University.
    Dahlquist, Erik
    School of Sustainable Development of Society and Technology, Mälardalen University.
    Ellegård, Kajsa
    Technology and Social Change, Linköping University.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Constructing load profiles for household electricity and hot water from time-use data-Modelling approach and validation2009In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 41, no 7, p. 753-768Article in journal (Refereed)
    Abstract [en]

    Time-use data, describing in detail the everyday life of household members as high-resolved activity sequences, have a largely unrealized potential of contributing to domestic energy demand modelling. A model for computation of daily electricity and hot-water demand profiles from time-use data was developed, using simple conversion schemes, mean appliance and water-tap data and general daylight availability distributions. Validation against detailed, end-use specific electricity measurements in a small sample of households reveals that the model for household electricity reproduces hourly load patterns with preservation of important qualitative features. The output from the model, when applied to a large data set of time use in Sweden, also shows correspondence to aggregate profiles for both household electricity and hot water from recent Swedish measurement surveys. Deviations on individual household level are predominantly due to occasionally ill-reported time-use data and on aggregate population level due to slightly non-representative samples. Future uses and developments are identified and it is suggested that modelling energy use from time-use data could be an alternative, or a complement, to energy demand measurements in households.

  • 38.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Annica
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A combined Markov-chain and bottom-up approach to modelling of domestic lighting demand2009In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 41, no 10, p. 1001-1012Article in journal (Refereed)
    Abstract [en]

    Detailed simulations of distributed generation in residential areas   have prompted the need for improved models of domestic electricity   demand that are able to reproduce important features of real household   loads. The high share and temporal variability of the lighting demand   make it of special interest, in particular when the models are to be   used in simulations of distributed photovoltaics (PV), which to a high   degree is negatively correlated with the lighting demand. In this   paper, a stochastic bottom-up model based on domestic occupancy   patterns and data on daylight availability is presented. A threestate   non-homogeneous Markov chain is used for generation of occupancy   patterns and a conversion model transforms occupancy patterns to   lighting demand, with respect to the daylight level. Markovchain   transition probabilities are determined from a detailed set of time-use   (TU) data in Swedish households and the parameters in the   occupancy-to-lighting conversion model are adjusted to make the   resulting load curves fit recent measurements on aggregate population   level. The performance of the model is analysed by comparison of   simulated demand to measured lighting demand. It is concluded that for   both individual households and aggregate demand, all relevant features   of measured demand are realistically reproduced.

  • 39.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A high-resolution stochastic model of domestic activity patterns and electricity demand2010In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 87, no 6, p. 1880-1892Article in journal (Refereed)
    Abstract [en]

    Realistic time-resolved data on occupant behaviour, presence and energy use are important inputs to various types of simulations, including performance of small-scale energy systems and buildings' indoor climate, use of lighting and energy demand. This paper presents a modelling framework for stochastic generation of high-resolution series of such data. The model generates both synthetic activity sequences of individual household members, including occupancy states, and domestic electricity demand based on these patterns. The activity-generating model, based on non-homogeneous Markov chains that are tuned to an extensive empirical time-use data set, creates a realistic spread of activities over time, down to a 1-min resolution. A detailed validation against measurements shows that modelled power demand data for individual households as well as aggregate demand for an arbitrary number of households are highly realistic in terms of end-use composition, annual and diurnal variations, diversity between households, short time-scale fluctuations and load coincidence. An important aim with the model development has been to maintain a sound balance between complexity and output quality. Although the model yields a high-quality output, the proposed model structure is uncomplicated in comparison to other available domestic load models.

  • 40.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Net zero energy solar buildings at high latitudes: The mismatch issue2010Conference paper (Refereed)
  • 41.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ellegård, Kajsa
    Modeling household electricity load from time-use data2008In: Proceedings of the Scientific Conference on Energy Saving and Green Energy, Älvsjö, Sweden, March 11-12, 2008, 2008Conference paper (Refereed)
  • 42.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lund, Peter
    HUT, Helsinki.
    Options for improving the load matching capability of distributed photovoltaics: Methodology and application to high-latitude data2009In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 83, no 11, p. 1953-1966Article in journal (Refereed)
    Abstract [en]

    At high latitudes, domestic electricity demand and insolation are   negatively correlated on both an annual and a diurnal basis. With   increasing integration of distributed photovoltaics (PV) in low-voltage   distribution grids of residential areas, limits to the penetration   level are set by voltage rise due to unmatched production and load. In   this paper a methodology for determining the impacts of three options   for increased load matching is presented and applied to high-latitude   data. The studied options are PV array orientation, demand side   management (DSM) and electricity storage. Detailed models for domestic   electricity demand and PV output are used. An optimisation approach is   applied to find an optimal distribution of PV systems on different   array orientations and a best-case evaluation of DSM and a storage   model are implemented. At high penetration levels, storage is the most   efficient option for maximising the solar fraction, but at lower   overproduction levels, the impact of DSM is equal or slightly better.   An east-west orientation of PV arrays is suggested for high penetration   levels, but the effect of the optimised orientation is small. Without   an optimised storage operation, the overproduced power is more   efficiently reduced by DSM than storage, although this is highly   dependent on the applied DSM algorithm. Further research should be   focused on the DSM potential and optimal operation of storage.

  • 43.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lund, Peter
    Options for improving the match between household electricity demand and photovoltaic generation at high latitudes2008In: Proceedings of EuroSun 2008, Lisbon, Portugal, October 7-10, 2008, 2008Conference paper (Refereed)
  • 44.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lund, Peter D.
    Corrigendum to "Options for improving the load matching capability of distributed photovoltaics: Methodology and application to high-latitude data"2009In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 83, p. 1953-1966Article in journal (Refereed)
  • 45.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Paatero, Jukka
    Lund, Peter
    Corrigendum to "Impacts of different data averaging times on statistical analysis of distributed domestic photovoltaic systems"2010In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, p. 492-500Article in journal (Refereed)
  • 46.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Paatero, Jukka
    Helsinki University of Technology.
    Lund, Peter
    Helsinki University of Technology.
    Impacts of different data averaging times on statistical analysis of distributed domestic photovoltaic systems2010In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 84, no 3, p. 492-500Article in journal (Refereed)
    Abstract [en]

    The trend of increasing application of distributed generation with solar photovoltaics (PV-DG) suggests that a widespread integration in existing low-voltage (LV) grids is possible in the future. With massive integration in LV grids, a major concern is the possible negative impacts of excess power injection from on-site generation. For power-flow simulations of such grid impacts, an important consideration is the time resolution of demand and generation data. This paper investigates the impact of time averaging on high-resolution data series of domestic electricity demand and PV-DG output and on voltages in a simulated LV grid. Effects of 10-minutely and hourly averaging on descriptive statistics and duration curves were determined. Although time averaging has a considerable impact on statistical properties of the demand in individual households, the impact is smaller on aggregate demand, already smoothed from random coincidence, and on PV-DG output. Consequently, the statistical distribution of simulated grid voltages was also robust against time averaging. The overall judgement is that statistical investigation of voltage variations in the presence of PV-DG does not require higher resolution than hourly.

  • 47.
    Widén, Joakim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Paatero, Jukka
    Helsinki University of Technology.
    Lund, Peter
    Helsinki University of Technology.
    Impacts of distributed photovoltaics on network voltages: Stochastic simulations of three Swedish low-voltage distribution grids2010In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 80, no 12, p. 1562-1571Article in journal (Refereed)
    Abstract [en]

    The continuously increasing application of distributed photovoltaics (PV-DG) in residential areas around the world calls for detailed assessment of distribution grid impacts. Both photovoltaic generation and domestic electricity demand exhibit characteristic variations on short and long time scales and are to a large extent negatively correlated, especially at high latitudes. This paper presents a stochastic methodology for simulation of PV-DG impacts on low-voltage (LV) distribution grids, using detailed generation and demand models. The methodology is applied to case studies of power flow in three existing Swedish LV grids to determine load matching, voltage levels and network losses at different PV-DG penetration levels. All studied LV grids can handle significant amounts of PV-DG, up to the highest studied level of 5 kWp PV per household. However, the benefits of PV-DG in terms of relative improvement of on-site reduction of demand, mitigated voltage drops and reduced losses were most significant at a penetration level of 1 kWp PV per household.

  • 48. Wäckelgård, Ewa
    et al.
    Bartali, Ruben
    Gerosa, Riccardo
    Laidani, Nadhira
    Mattsson, Andreas
    Micheli, Victor
    Rivolta, Barbara
    New cermet coatings for mid-temperature applications for solar concentrated combine heat and power system2014In: Proceedings of the 2ND International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013) / [ed] Haberle, A, 2014, p. 242-249Conference paper (Refereed)
    Abstract [en]

    New cermet (ceramic-metal) composite coatings have been developed for solar absorbers in a solar concentrating system for combined heat and power operating in a mid-temperature range between 250 to 350 degrees C. The coatings were applied on stainless steel substrates. Two types of cermet with expected good duration properties were chosen: Nb-TiO2 and W-SiO2. The basic layer-structure concept consisted of four sub-layers, counted from the substrate: molybdenum infrared reflector, high metal concentration cermet of either Nb-TiO2 or W-SiO2, low metal concentration cermet of either Nb-TiO2 or W-SiO2 and SiO2 antireflection layer. The results from optimised coating fabrication gave solar absorptance and thermal emittance of 0.93 and 0.09 respectively for the Nb-TiO2 cermet and 0.91 and 0.08 for the W-SiO2 cermet based absorbers. Annealing at 350 degrees C did not change the absorptance but decreased the thermal emittance with 0.01 units. Adhesion to substrate and between sub-layers was good and even improved after annealing. In a next step up-scaling to deposition on tubes has been made for the Nb-TiO2 cermet type coating and such absorbers are now operating in the solar concentrating combined heat and power demonstration plant in Malta.

  • 49.
    Wäckelgård, Ewa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bartali, Ruben
    Fondazione Bruno Kessler.
    Gerosa, Riccardo
    Laidani, Nadhira
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Micheli, Victor
    Rivolta, Barbara
    New Cermet Coatings for Mid-temperature Applications for Solar Concentrated Combine Heat and Power System2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 48, p. 242-249Article in journal (Refereed)
  • 50.
    Wäckelgård, Ewa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bartali, Ruben
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Gerosa, Riccardo
    Dipartimento di Meccanica, Politecnico di Milano, Milan, Italy.
    Gloria, Gottardi
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Laidani, Nadhira
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Micheli, Victor
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rivolta, Barbara
    Dipartimento di Meccanica, Politecnico di Milano, Milan, Italy.
    Development of W–SiO2 and Nb–TiO2 solar absorber coatings for combined heat and power systems at intermediate operation temperatures2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 133, p. 180-193Article in journal (Refereed)
    Abstract [en]

    Two new absorber coatings for mid-temperature operation (300–350 1C) in collectors for solar thermal electricity plants are presented in this study. The absorbers consist of two cermet layers of either W–SiO2 or Nb–TiO2, deposited on a molybdenum infrared reflector and coated with an antireflection layer of silicon oxide. The optimization of the optical performance was made in two steps. First, the layer structure was optimized in model calculations. The optical constants used in this modelling were derived directly from sputtered films of the cermet constituents using reflectance and transmittance measure- ments. The absorber coatings were then sputter-deposited using parameters from the modelling. The results show good agreement between modelled and sputtered optical performance evaluated as solar absorptance and thermal emittance at 350 1C. The optimal values reached for W–SiO2 was 0.91 in combination with 0.08 and 0.93 in combination with 0.09 for Nb–TiO2. The materials characterization from XRD, AES and TEM shows that the composite coatings contain nano-metal inclusions, meaning that they are cermet coatings. Scratch tests show that the coatings adhere well to the substrate of stainless steel. Temperature testing at 350 1C in vacuum for up to 1500 h shows that both coatings are stable under such conditions. Only a slight change occurs during the first 72 h that decreases the emittance but does not change the solar absorptance. ERDA confirms that there is no detectable level of ion migration between layers, only a small decrease in hydrogen content was observed, which indicates outgassing.

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