Laboratory intercomparison of solar absorptance and thermal emittance measurements at room temperature

Solar thermal absorber coatings play an important role in the opto-thermal efficiency of receivers in Concentrated Solar Power (CSP). Two standard figures of merit are the solar absorptance αsol and thermal emittance εth, derived from spectral directional hemispherical reflectance measurements at room temperature. These two figures of merit allow comparing coating formulations in terms of performance and durability. In this study, a black coating and a solar selective coating are optically characterized by different laboratories to compare spectral datasets, solar absorptance αsol and thermal emittance εth calculations. The comparison includes various benchtop spectrophotometers operating in the UV-VIS-NIR and Infrared spectral ranges as well as three commercial portable reflectometers/emissometers. A good agreement is found between the nine parties participating in this intercomparison campaign. The black coating αsol value is 96.6 ± 0.2%, while the solar selective coating αsol value is 94.5 ± 0.4%. For the thermal emittance, spectral data is concatenated and integrated from 0.3 to 16 μm. The black coating εth value calculated at 650 °C is 80.8 ± 3.8%, while the solar selective coating εth value calculated at 650 °C is 25.0 ± 0.5%

Opera omnia Desiderii Erasmi

Panegyricus ad Philippum Austriae ducem • Institutio principis Christiani • Lingu

Opera omnia Desiderii Erasmi

• Querela Pacis • Ex Plutarcho versa 1. Quo pacto possis adulatorem ab amico dignoscere 2. Quo pacto quis efficiat vt ex inimicis capiat vtilitatem 3. De tuenda bona valetudine precepta 4. In principe requiri doctrinam 5. Cum principibus maxime philosophum debere disputare 6. Vtrum grauiores sint animi morbi quam corporis 7. Num recte dictum sit Λάθε βιώσας id est Sic viue vt nemo te sentiat vixisse 8. De cupiditate diuitiarum 9. De cohibenda iracundia 10. De curiositate 11. De vitiosa verecundi

High stability laser for next generation gravity missions

With GRACE (launched 2002) and GOCE (launched 2009) two very successful missions to measure earth’s gravity field have been in orbit, both leading to a large number of publications. For a potential Next Generation Gravity Mission (NGGM) from ESA a satellite-to-satellite tracking (SST) scheme, similar to GRACE is under discussion, with a laser ranging interferometer instead of a Ka-Band link to enable much lower measurement noise. Of key importance for such a laser interferometer is a single frequency laser source with a linewidth <10 kHz and extremely low frequency noise down to 40 Hz / √Hz in the measurement frequency band of 0.1 mHz to 1 Hz, which is about one order of magnitude more demanding than LISA. On GRACE FO a laser ranging interferometer (LRI) will fly as a demonstrator. The LRI is a joint development between USA (JPL,NASA) and Germany(GFZ,DLR). In this collaboration the JPL contributions are the instrument electronics, the reference cavity and the single frequency laser, while STI as the German industry prime is responsible for the optical bench and the retroreflector. In preparation of NGGM an all European instrument development is the goal