John B. Rekstad

• Carlsson, Bo; Meir, Michaela Georgine; Rekstad, John Bernhard; Preiss, Dieter & Thomas, Ramschak (2016). Replacing traditional materials with polymeric materials in solar thermosiphon systems – Case study on pros and cons based on a total cost accounting approach. Solar Energy.  ISSN 0038-092X.  125, s 294- 306 . doi: 10.1016/j.solener.2015.12.005 Vis sammendrag

  The pros and cons of replacing traditional materials with polymeric materials in solar thermosiphon systems were analysed by adopting a total cost accounting approach. In terms of climatic and environmental performance, polymeric materials reveal better key figures than traditional ones like metals. In terms of present value total cost of energy, taking into account functional capability, end user investment cost, O&M cost, reliability and climatic cost, the results suggest that this may also be true when comparing a polymeric based thermosiphon system with a high efficient thermosiphon system of conventional materials for DHW production in the southern Europe regions. When present values for total energy cost are assessed for the total DHW systems including both the solar heating system and the auxiliary electric heating system, the difference in energy cost between the polymeric and the traditional systems is markedly reduced. The main reason for the difference in results can be related to the difference in thermal performance between the two systems. It can be concluded that the choice of auxiliary heating source is of utmost importance for the economical competiveness of systems and that electric heating may not be the best choice.

• Steffen, Robert; Wallner, Gernot; Rekstad, John Bernhard & Röder, Beate (2016). General characteristics of photoluminescence from dry heat aged polymeric materials. Polymer degradation and stability.  ISSN 0141-3910.  134, s 49- 59 . doi: 10.1016/j.polymdegradstab.2016.09.032
• Rekstad, John Bernhard; Meir, Michaela Georgine; Murtnes, Espen & Dursun, Aylin Maria (2015). A comparison of the energy consumption in two passive houses, one with a solar heating system and one with an air-water heat pump. Energy and Buildings.  ISSN 0378-7788.  96, s 149- 161 . doi: 10.1016/j.enbuild.2015.02.059
• Carlsson, Bo; Persson, Helena; Meir, Michaela Georgine & Rekstad, John Bernhard (2014). A total cost perspective on use of polymeric materials in solar collectors – Importance of environmental performance on suitability. Applied Energy.  ISSN 0306-2619.  125, s 10- 20 . doi: 10.1016/j.apenergy.2014.03.027
• Meir, Michaela Georgine; Murtnes, Espen; Dursun, Aylin Maria & Rekstad, John Bernhard (2014). Polymeric collectors or Heat Pump? Lessons learned from passive houses in Oslo. Energy Procedia.  ISSN 1876-6102.  48C, s 914- 923 . doi: 10.1016/j.egypro.2014.02.105
• Larsen, Ann-Cecilie; Goriely, Stephane; Algin, Emel; Agvaanluvsan, Undraa; Bürger, Annetta; Görgen, Andreas; Guttormsen, Magne Sveen; Hagen, Trine Wiborg; Lönnroth, Tom; Mitchell, Gary E.; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Renstrøm, Therese; Rose, Sunniva Johanne; Ruud, Inger Eli; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan; Toft, Heidi Kristine; Tveten, Gry Merete; Voinov, Alexander & Wikan, Kristine (2011). Gamma-ray strength functions and their relation to astrophysics. AIP Conference Proceedings.  ISSN 0094-243X.  1377, s 239- 246 . doi: 10.1063/1.3628386
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Krticka, Milan; Betak, Emil; Bürger, Alexander; Görgen, Andreas; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Toft, Heidi Kristine; Tveten, Gry Merete; Voinov, Alexander & Wikan, Kristine (2011). Analysis of possible systematic errors in the Oslo method. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  83 . doi: 10.1103/PhysRevC.83.034315
• Seljom, Pernille Merethe; Rosenberg, Eva; Fidje, Audun; Haugen, Jan Erik; Meir, Michaela Georgine; Rekstad, John Bernhard & Jarlset, Thore (2011). Modelling the effects of climate change on the energy system—A case study of Norway. Energy Policy.  ISSN 0301-4215.  39(11), s 7310- 7321 . doi: 10.1016/j.enpol.2011.08.054
• Kahlen, Susanne; Wallner, Gernot; Lang, R.W.; Meir, Michaela Georgine & Rekstad, John Bernhard (2010). Aging behavior of polymeric solar absorber materials: Aging on the component level. Solar Energy.  ISSN 0038-092X.  84(3), s 459- 465 . doi: 10.1016/j.solener.2010.01.003
• Olivares, A; Rekstad, John Bernhard; Meir, Michaela Georgine; Kahlen, Susanne & Wallner, Gernot (2010). Degradation model for an extruded polymeric solar thermal absorber. Solar Energy Materials and Solar Cells.  ISSN 0927-0248.  94(6), s 1031- 1037 . doi: 10.1016/j.solmat.2010.02.001
• Siem, Sunniva; Agvaanluvsan, Undraa; Bürger, Alexander; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Syed, Naeem Ul Hasan; Toft, Heidi Kristine; Tveten, Gry Merete & et al., , (2009). Level densities and radiative strength functions. AIP Conference Proceedings.  ISSN 0094-243X.  1090, s 66- 73 . doi: 10.1063/1.3087125
• Syed, Naeem Ul Hasan; Guttormsen, Magne Sveen; Ingebretsen, Finn; Larsen, Ann-Cecilie; Lonnroth, T; Rekstad, John Bernhard; Schiller, A; Siem, Sunniva & Voinov, A (2009). Level density and gamma-decay properties of closed shell Pb nuclei. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  79(2) . doi: 10.1103/PhysRevC.79.024316
• Olivares, Lopez Andres F; Rekstad, John Bernhard; Meir, Michaela Georgine; Kahlen, Susanne & Wallner, Gernot (2008). A test procedure for extruded polymeric solar thermal absorbers. Solar Energy Materials and Solar Cells.  ISSN 0927-0248.  92(4), s 445- 452 . doi: 10.1016/j.solmat.2007.10.006 Vis sammendrag

  Abstract - An indentation test is proposed to study the degradation of extruded polymeric solar absorbers. The thermal degradation caused by accelerated aging is investigated. The results are compared with the thermal and mechanical impacts during the operation of the solar collector.

• Algin, Emel; Agvaanluvsan, Undraa; Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Mitchell, Gary; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva & Voinov, Alexander (2008). Thermodynamic properties of 56,57Fe. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  C78(054321)
• Guttormsen, Magne Sveen; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan & Voinov, Alexander (2008). Thermodynamic properties of atomic nuclei with T<1 MeV. AIP Conference Proceedings.  ISSN 0094-243X.  1012, s 198- 202
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan; Voinov, Alexander & Messelt, Svein (2008). Experimental nuclear level densities and gamma-ray strength functions in Sc and V isotopes. AIP Conference Proceedings.  ISSN 0094-243X.  1005, s 70- 73
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan; Voinov, Alexander & Messelt, Svein (2008). Puzzling gamma-ray strength functions in 44,45Sc and 50,51V. AIP Conference Proceedings.  ISSN 0094-243X.  s 380- 382
• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Syed, Naeem Ul Hasan; Schiller, Andreas; Voinov, Alexander & Ødegård, Stein Westad (2008). Level densities and gamma-strength functions in Sm isotopes. AIP Conference Proceedings.  ISSN 0094-243X.  s 425- 427
• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Syed, Naeem Ul Hasan; Schiller, Andreas; Voinov, Alexander; Ødegård, Stein Westad; Nyhus, Hilde-Therese; Messelt, Svein & Ingebretsen, Finn (2008). Experimental Level densities and gamma-strength functions in rare earth nuclei. AIP Conference Proceedings.  ISSN 0094-243X.  1005
• Algin, E; Schiller, A; Voinov, A; Agvaanluvsan, U; Belgya, T; Bernstein, LA; Brune, CR; Chankova, Rosita; Garrett, PE; Grimes, SM; Guttormsen, Magne Sveen; Hjorth-Jensen, Morten; Hornish, MJ; Johnson, CW; Massey, T; Mitchell, GE; Rekstad, John Bernhard; Siem, Sunniva & Younes, W (2007). Bulk properties of iron isotopes. Physics of Atomic Nuclei.  ISSN 1063-7788.  70, s 1634- 1639 . doi: 10.1134/S1063778807090232
• Guttormsen, Magne; Chankova, Rosita; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Siem, Sunniva; Syed, Naeem Ul Hasan; Agvaanluvsan, Undraa; Schiller, Andreas & Voinov, Alexander (2007). The role of broken cooper pairs in warm nuclei. Acta Physica Polonica B.  ISSN 0587-4254.  38(4), s 1489- 1493
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom; Messelt, Svein; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan & Voinov, Alexander (2007). Nuclear level densities and gamma-ray strength functions in Sc-44,Sc-45. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  (76) . doi: 10.1103/PhysRevC.76.044303
• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rosita; Ingebretsen, Finn; Lönnroth, Tom; Messelt, Svein; Ødegård, Stein Westad; Rekstad, John Bernhard; Siem, Sunniva; Syed, Naeem Ul Hasan; Schiller, Andreas & Voinov, Alexander (2007). Radiative strength functions of warm nuclei in the 1f(7/2) shell. Acta Physica Polonica B.  ISSN 0587-4254.  38(4), s 1495- 1498
• Siem, Sunniva; Guttormsen, Magne; Chankova, Rosita; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas & Syed, Naeem Ul Hasan (2007). Level densities and gamma strength functions in Sm-146,Sm-147 nuclei. Acta Physica Polonica B.  ISSN 0587-4254.  38(4), s 1499- 1502
• Algin, Emel; Schiller, Andreas; Guttormsen, Magne Sveen; Hjorth-Jensen, Morten; Rekstad, John Bernhard; Siem, Sunniva & et al, . (2006). Bulk Properties of Iron Isotopes. Physics of Atomic Nuclei.  ISSN 1063-7788.  70(9), s 1634- 1639
• Chankova, Rositsa; Schiller, A; Agvaanluvsan, U; Algin, E; Bernstein, LA; Guttormsen, Magne; Ingebretsen, Finn; Lonnroth, T; Messelt, Svein; Mitchell, GE; Rekstad, John Bernhard; Siem, Sunniva; Larsen, Ann-Cecilie; Voinov, A & Ødegård, Stein Westad (2006). Level densities and thermodynamical quantities of heated Mo93-98 isotopes. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  73
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Hjorth-Jensen, Morten; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Larsen, Ann-Cecilie; Syed, Naeem Ul Hasan & Voinov, Alexander (2006). Single particle entropy in heated nuclei. AIP Conference Proceedings.  ISSN 0094-243X.  831, s 162- 166
• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan & Voinov, Alexander (2006). Experimental nuclear level densities and interpretation within the microcanonical ensemble. PoS - Proceedings of Science.  ISSN 1824-8039. Vis sammendrag

  Statistical properties of atomic nuclei are studied as function of the number of neutrons. The experimental method is based on particle-g coincidences measured in light-ion reactions with one charged ejectile. From particle-g coincidences, level densities and radiative strength functions can be simultaneously extracted from one and the same data set. Mid-shell nuclei show significant odd-even entropy differences interpreted as the single-particle entropy of the valence nucleon. However, these properties change when approaching closed shells. A model within the framework of the microcanonical ensemble is presented and compared with data from the molybdenum isotopes. The odd-even entropy difference disappears in the vicinity of the N =50 shell, and an overshoot of positive parity states is predicted.

• Kaneko, K.; Hasegawa, M.; Agvaanluvsan, Undraa; Algin, Emel; Chankova, Rositsa; Guttormsen, Magne; Larsen, Ann-Cecilie; Mitchell, Gary; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva & Voinov, Alexander (2006). Breaking of nucleon Cooper pairs at finite temperature in 93-98Mo. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  74
• Larsen, Ann-Cecilie; Chankova, Rositsa; Guttormsen, Magne; Ingebretsen, Finn; Messelt, Svein; Rekstad, John Bernhard; Siem, Sunniva; Syed, Naeem Ul Hasan; Ødegård, Stein Westad; Lönnroth, Tom; Schiller, Andreas & Voinov, Alexander (2006). Microcanonical entropies and radiative strength functions of 50,51V. Physical Review C. Nuclear Physics.  ISSN 0556-2813.  73 . doi: 10.1103/PhysRevC.73.064301
• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rositsa; Ingebretsen, Finn; Lønnroth, Tom; Messelt, Svein; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan; Voinov, Alexander & Ødegård, Stein Westad (2006). Heating nuclei in the mass region of A = 40-50. AIP Conference Proceedings.  ISSN 0094-243X.  831, s 544- 547

Se alle arbeider i Cristin

• Rekstad, John Bernhard; Ingvild, Skjelland; De Meersman, Els; Yves, Klinger & Meir, Michaela Georgine (2016). Auf dem Sonnendach - Modifizierte Hochleistungskunststoffe zur Extrusion von Solarthermie Anwendungen. Kunststoffe.  ISSN 0023-5563.  2, s 77- 79 Vis sammendrag

  Sonnenkollektoren können Solarenergie in thermische Energie für Heizungen und Warmwasseraufbereitung umwandeln. Der Solarabsorber muss dabei hohen thermischen und mechanischen Belastungen standhalten. Wurden für diese Anwendung bisher hauptsächlich Metalle eingesetzt, hat ein Forschungskonsortium nun spezielle Polymerblends dafür entwickelt. Im Vordergrund stand die effektive Extrusion eines Hochleistungskunststoffs zu großflächigen Doppelstegplatten.

• Dursun, Aylin Maria; Rekstad, John Bernhard & Meir, Michaela Georgine (2013). Natural circulating flat plate collectors - Investigations of a new material and performance simulations.
• Meir, Michaela Georgine; Carlsson, Bo & Rekstad, John Bernhard (2013). Life-cycle assessment of polymeric thermosiphon collectors.
• Meir, Michaela Georgine; Rekstad, John Bernhard; Dursun, Aylin Maria & Murtnes, Espen (2013). Polymeric solar collectors or heat pump? - Lessons learned from passive houses in Oslo.
• Larsen, Ann-Cecilie; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas; Guttormsen, Magne Sveen; Hagen, Trine Wiborg; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Renstrøm, Therese; Rose, Sunniva Johanne; Ruud, Inger Eli; Siem, Sunniva; Tveten, Gry Merete; Goriely, Stephane; Harrisopulos, Sotirios; Schiller, Andreas; Voinov, Alexander; Wilson, Jonathan; Leniau, Baptist; Gunsing, Frank; Krticka, Milan; Betak, Emil; Bernstein, Lee; Bleuel, Darren L.; Wiedeking, Mathis; Agvaanluvsan, Undraa; Mitchell, Gary E.; Algin, Emel & Lönnroth, Tom (2011). Experiments of reaction model inputs: level density and gamma strength.
• Larsen, Ann-Cecilie; Guttormsen, Magne Sveen; Bürger, Alexander; Eriksen, Tomas Kvalheim; Görgen, Andreas; Hagen, Trine Wiborg; Nyhus, Hilde-Therese; Rekstad, John Bernhard; Renstrøm, Therese; Rose, Sunniva Johanne; Ruud, Inger Eli; Siem, Sunniva; Syed, Naeem Ul Hasan; Toft, Heidi Kristine; Tveten, Gry Merete & Wikan, Kristine (2011). Level density and gamma strength - achievements and challenges.
• Rekstad, John Bernhard (2010). New solar collectors in polymer materials.
• Rekstad, John Bernhard (2010, 25. oktober). Polymeric solar collectors. [Internett].  SolarThermal World.
• Rekstad, John Bernhard (2010). Progress report, solar thermal collectors.
• Rekstad, John Bernhard (2010). Solar Collector Absorbers in High-performance Polymer Materials.
• Rekstad, John Bernhard (2010). Solar collector, recent development.
• Rekstad, John Bernhard (2010, 26. mai). Solar energy R&D in Norway. [Internett].  SolarThermal World.
• Berset, Simone Prytz & Rekstad, John Bernhard (2009, 01. mai). Uutnyttet potensial - Individuell måling av fjernvarme har et stort enøk-potensial.  Magazin: Norsk VVS.
• Rekstad, John Bernhard (2009). ESFRI Energy WR, Roadmap for large research infrastructures in Europe.
• Rekstad, John Bernhard (2009). Energibruk i bygg. Hva kan sola bidra med?.
• Rekstad, John Bernhard (2009). Om solenergi.
• Rekstad, John Bernhard (2009). Polymer Materials for Solar Thermal Applications.
• Rekstad, John Bernhard (2009). Solar collectors in polymer materials.
• Rekstad, John Bernhard (2009). Solar heat - of interest in Norway?. Vis sammendrag

  Norway has for a long time lagged behind on the statistics of utilization of solar heat. But in August 2008 the Norwegian institution Enova opened a programme for subsidizing solar heating systems. This made way to an increased interest on solar heat systems in Norway, as has earlier been seen in many other countries Rekstad will in this lecture discuss how solar heat utilization in buildings compares to alternative heating systems. Different technical solutions are available, and some research on solar heat is being done on the University of Oslo.

• Rekstad, John Bernhard (2009). Solar thermal R&D at UiO.
• Rekstad, John Bernhard (2009). Solar thermal R&D at the University of Oslo.
• Rekstad, John Bernhard (2009). Solenergi.
• Rekstad, John Bernhard (2009). Solenergi - den største potensielle energikilden.
• Rekstad, John Bernhard (2009). Solenergi - en kilde i våre hender.
• Rekstad, John Bernhard (2009). Update of research: University of Oslo and Aventa.
• Rekstad, John Bernhard & Borgestrand, Odd (2009, 30. juni). Fornybar energi.  VVS aktuelt.
• Rekstad, John Bernhard & Kongsnes, Ellen (2009, 10. mars). Norge har jumboplass på solenergi.  Stavanger Aftenbladet.
• Rekstad, John Bernhard & Nylund, Hilde Kari (2009, 01. mai). Polymerer er framtida.  Magazin: Norsk VVS.
• Lòpez, Andres Franklin Olivares; Rekstad, John Bernhard & Meir, Michaela Georgine (2008). Service life estimation for a polymeric solar absorber. Series of dissertations submitted to the Faculty of Mathematics and Natural Sciences, University of Oslo.. 722.
• Meir, Michaela Georgine & Rekstad, John Bernhard (2008). IEA-SHC Task 39: Polymeric solar thermal Collectors - State of the Art.
• Meir, Michaela Georgine; Rekstad, John Bernhard; Gjessing, Jo & Rumler, Nele (2008). Overheating protection of polymeric solar collectors by triggered ventilation.
• Rekstad, John Bernhard (2008). "All polymer" solar collectors for medium temperature applications.
• Rekstad, John Bernhard (2008). Eneregi, tjenester, komfort.
• Rekstad, John Bernhard (2008). Energisituasjonen - trusler og muligheter.
• Rekstad, John Bernhard (2008, 20. august). Fang sol og spar strøm.  VG.
• Rekstad, John Bernhard (2008). Finnes løsningen på energiutfordringene i kjernefysikken ?.
• Rekstad, John Bernhard (2008). Fornybare energikilder - tema solenergi.
• Rekstad, John Bernhard (2008). Forskning og utvikling innen termisk solenergi.
• Rekstad, John Bernhard (2008, 12. juni). Mot 100% vekst for solstrøm.  Elektro Energiteknikk.
• Rekstad, John Bernhard (2008). Nye energiløsninger.
• Rekstad, John Bernhard (2008). Næringslivets kompetansebehov innen solenergi.
• Rekstad, John Bernhard (2008). Om solenergi.
• Rekstad, John Bernhard (2008, 01. november). Oppvarmet med kosmisk energi.  Folkevett no 5, 2008.
• Rekstad, John Bernhard (2008). Polymers in Solar Systems.
• Rekstad, John Bernhard (2008). Progress report, solar energy research.
• Rekstad, John Bernhard (2008). Results from solar thermal energy reserach at the University of Oslo.
• Rekstad, John Bernhard (2008). Sola som energigiver. Praktisk utnyttelse av solenergi.
• Rekstad, John Bernhard (2008). Solar Energy.
• Rekstad, John Bernhard (2008). Solenergi og klima.
• Rekstad, John Bernhard (2008). Solvarme, demonstrasjon av fungerende solvarmesystem.
• Rekstad, John Bernhard (2008). Termisk solenergi i større bygninger.
• Rekstad, John Bernhard (2008). Utarbeidelse av ny "ESFRI Roadmap for Large Reserach Infrastructures" i Europa.
• Rekstad, John Bernhard (2008). Utnyttelse av varmestråling - varme og kulde fra solstråling.
• Larsen, Ann-Cecilie; Chankova, Rositsa; Guttormsen, Magne Sveen; Ingebretsen, Finn; Lönnroth, Tom; Messelt, Svein; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan & Voinov, Alexander (2007). Puzzling gamma-ray strength functions in 44,45Sc and 50,51V.
• Meir, Michaela Georgine; Rekstad, John Bernhard & Meek, Frode (2007). Energimålinger i boligene i Bjørnveien 119. Arkitektur N.  ISSN 1504-7628.  (08), s 49
• Rekstad, John Bernhard (2007). Energy Physics - Solar Energy.
• Rekstad, John Bernhard (2007). Innovative solar thermal systems in Norway. Vis sammendrag

  Two perspectives are necessary for a presentation of solar energy in Norway. One perspective is the use of solar energy, - thermal and PV in the Norwegian market. The other perspective is the development of industry and commerce related to solar energy.

• Rekstad, John Bernhard (2007). Polymers from a market perspective, ideas for future development.
• Rekstad, John Bernhard (2007). Termisk solenergi, energibruk i bygg, vannbårne varme- og kjølesystemer.
• Rekstad, John Bernhard; Meir, Michaela Georgine; Olivares, Lopez Andres F & Gjessing, Jo (2007). Polymeric materials in solar collectors. Vis sammendrag

  The paper outlines the impact of temperature on polymeric solar thermal collectors, and methods to reduce the thermal degradation. If solar thermal shall play the role in the future that is desired and forecasted, new materials will be required. Both the IEA's-Solar heating and Cooling Programme and EU’s 7 Framework Programme focus on polymeric collectors. The main barrier for a full breakthrough for the polymer solution is the temperature sustainability in situations where stagnation temperatures occur. This problem is significantly smaller for Nordic climate than at for latitudes further south. The strong engagement revealed by leading industries in the polymer sector can be an inspiration and opportunity for scientific and technical Nordic research groups to take a frontier position in this field.

• Siem, Sunniva; Guttormsen, Magne Sveen; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Syed, Naeem Ul Hasan; Schiller, Andreas; Voinov, Alexander; Ødegård, Stein Westad & Nyhus, Hilde-Therese (2007). Level densities and gamma-strength functions in rare earth nuclei.
• Kristoffersen, Astrid Rusås; Rekstad, John Bernhard & Aurlien, Tormod (2006). Heat and mass transfer in buildings. Dissertation for the Degree Dr. Philos. ISSN 1501-7710. 462.
• Rekstad, John Bernhard (2006). Oppsving for solenergi?.
• Furbo, Simon; Rekstad, John Bernhard; Meir, Michaela Georgine; Bales, Chris; Blumberga, Dagnija; Thür, Alexander; Karlsson, Björn & Fiedler, Frank (2006). Nordic Energy Research Cooperation on Solar Combisystems. Vis sammendrag

  This paper describes ongoing research on solar combisystems for the Nordic and Baltic countries carried out within the projects “Competitive solar heating systems for residential buildings” and “Solar thermal components adapted to common building standards”. The aim of the projects is to develop competitive solar combisystems which are attractive to buyers and to educate experts in the solar heating field. The participants of the projects, which are financed by Nordic Energy Research, Nordic Innovation Centre and the participants themselves, are the universities: Technical University of Denmark, Dalarna University, University of Oslo, Riga Technical University and Lund Institute of Technology, as well as the companies: Metro Therm A/S (Denmark), Velux A/S (Denmark), Solentek AB (Sweden), SolarNor (Norway) and SIA Grandeg (Latvia). The projects include education, research, development and demonstration. The activities started in 2003 and will be finished by the end of 2006. The projects consist of a number of Ph.D. studies in Denmark, Sweden and Latvia, and a post-doc. study in Norway. Close cooperation between the researchers and the industry partners ensures that the results of the projects can be utilized. By the end of the projects, the industry partners will be able to bring the developed systems into the market. In Denmark and Norway the research and development focus is on solar heating/natural gas systems, and in Sweden and Latvia the focus is on solar heating/pellet systems. Additionally, Lund Institute of Technology and University of Oslo are studying solar collectors of various types being integrated into the building. Keywords: Solar combisystems, Nordic research cooperation.

• Guttormsen, Magne; Agvaanluvsan, Undraa; Chankova, Rositsa; Larsen, Ann-Cecilie; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan & Voinov, Alexander (2006). Entropy in Nuclei.
• Kahlen, Susanne; Wallner, Gernot; Meir, Michaela Georgine; Rekstad, John Bernhard & Olivares, Lopez Andres F (2006). Aging behavior of polymeric materials for solar-thermal applications – Effect on ultimate mechanical properties. Vis sammendrag

  There is a high potential for innovative advancements by the proper integration of polymeric materials is to be expected for solar-thermal components and systems. The wide range of properties may be realized by polymeric materials combined with their cost efficiency, high flexibility with regard to processing and the high potential for multi-functional integration. The advantages related to the use of polymers in solar-thermal components and systems include functional improvements, system cost reductions and - last but not least - more design freedoms to meet the aesthetic demands of architects and end-users. While polymers are already extensively used in unglazed swimming-pool collectors, only a few all-polymeric glazed solar-thermal collectors are currently commercially available. The one investigated in the present paper, launched by Solarnor (Norway), consists of a twin-wall glazing, made of polycarbonate, and an extruded absorber sheet with injection moulded endcaps, made of a blend of polyphenylene ether and polystyrene (PPE+PS). The main objective of this paper is to develop and apply characterization methods which allow for a quality assurance testing of the polymeric absorber on component level. The overall performance of polymeric solar absorbers is affected by the material used and by the processing procedures applied. Based on the relevant and partly standardized procedures for the quality assurance testing of plastics pipes, various thermoanalytical and mechanical methods have been evaluated and adopted for the testing of polymeric absorber sheets made of a PPE+PS blend. To characterize the basic polymer and the effects of processing on the morphology, dynamic mode thermoanalytical test methods requiring small samples have been applied. To check the extruded absorber sheet as to effects of sheet geometry and processing conditions, mechanical tests in bending and impact mode were developed and applied to specimens taken from different positions of the absorber sheet. For a full-scale test of the absorber including the extruded sheet and the joined injection moulded endcap an internal pressure testing procedure with water inside and ambient air at 80°C was adopted and applied to absorbers taken from two production series. By thermoanalysis the effect of post-processing treatment could be reflected for extruded absorber sheets annealed at various temperatures below the glass transition temperature of the PPE+PS blend. The size of the endothermic peak, superimposed the endothermic step of the glass transition, allows for the description of processing and annealing induced morphological changes within the amorphous polymer. The mechanical stability of the absorber was investigated by monotonic tensile testing and impact testing. Internal pressure testing revealed differences for absorber sheets from different production series.

• Larsen, Ann-Cecilie; Guttormsen, Magne; Chankova, Rositsa; Ingebretsen, Finn; Lönnroth, Tom; Messelt, Svein; Rekstad, John Bernhard; Schiller, Andreas; Siem, Sunniva; Syed, Naeem Ul Hasan; Voinov, Alexander & Ødegård, Stein Westad (2006). Radiative strength functions of warm nuclei in the 1f7/2 shell.
• Rekstad, John Bernhard (2006). Byggnadsintegrerad solfångare för systemhus – en norsk framgångshistoria.
• Rekstad, John Bernhard (2006). Challenges of polymeric materials in solar thermal applications from a market perspective.

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