[en] Highlights: • CPCs with and without exit angle restriction based PV modules were fabricated and tested. • Performance of both CPVs was investigated and compared. • Results showed that CPV-65 performed slightly but insignificantly better as compared to CPV-90. - Abstract: To perform this comparison, the compound parabolic concentrator with a restricted exit angle of 65° (CPC-65) and the one without exit angle restriction (CPC-90) were fabricated and tested for concentrating radiation on multi-crystalline solar cells. Both CPC-65 and CPC-90 are identical in the acceptance half-angle (20°) and geometrical concentration factor (2×). Theoretical calculations showed that CPC-90 based PV system (CPV-90) annually concentrated about 3–5% more radiation on solar cells as compared to CPC-65 based PV system (CPV-65). For CPV-65, all radiation would arrive on the solar cells at the incidence angle less than 65°, but for CPV-90, about 8–10% of annual collectible radiation would arrive on solar cells at the incidence angle larger than 65°. Measurements at outdoor conditions showed that the CPV-65 performed slightly better than CPV-90 in terms of short-circuit current and power output as the projection incidence angle of solar rays on the cross-section of CPC-troughs (θ_p) less than the acceptance half-angle, otherwise the CPV-90 did better. Compared to CPV-90, the power output at maximum power points from CPV-65 were slightly higher, and increases of 2.1%, 5.4% and 8.17% were measured for θ_p = 0°, 10° and 16°, respectively. Analysis indicated that effect of solar flux distribution over solar cells on power output of both CPVs was almost identical and insignificant, and the CPV-65 performed slightly but insignificantly better than the CPV-90 in terms of annual power output except in areas with poor solar resources where the annual power output from both systems was almost identical

[en] To perform this work, two sets of solar water heaters, each set consisting of two flat plate collectors and a storage tank, were tested. The collectors in one system consist of aluminium absorbers painted matte black, and those in the other system consist of copper-aluminium composite absorbers with anode oxidized coating. For each of the systems, one collector is glazed and the other is unglazed. The experimental results showed that, if thermosyphonic reverse flow in the solar systems was not allowed, the stagnant absorber temperatures of all the collectors were 6-8 deg. C and about 1 deg. C lower than the ambient temperature at clear and overcast nights, respectively, the glazing and absorber coating of a collector had insignificant effects on the stagnant temperature depression of the collector absorbers (defined as the temperature difference between ambient air and absorbers), but the weather conditions had considerable effects. These results implied that the collector might be damaged by freezing at clear nights even when the air temperature was above 0 deg. C, such as 2-3 deg. C, and the possibility of freeze damage at clear nights was much higher than that at overcast nights for a given ambient air temperature slightly above the freezing temperature. Experimental results also indicated that if reverse flow in the solar systems were allowed, the absorber temperature of the collectors was stable all night at both clear and overcast nights and even higher than the ambient air temperature at overcast night as a result of the fact that the heat lost by the collectors at night was offset by the hot water inside the storage tank of the systems through the thermosyphonic reverse flow. This indicated that the reverse flow was very effective for preventing freezing of the collectors, and the freeze damage could be, theoretically, avoided by keeping the water temperature inside the storage tank of a solar thermosyphonic system at a certain level

[en] To investigate effects of water temperature in the storage tank and height difference between collector loop connections at the tank on freeze protection of flat-plate collectors at clear nights in terms of outlet water temperature of the thermosiphonic reverse flow from the collector (referred to as T_out), two sets of thermosiphon domestic solar water heaters (DSWH, in short) were constructed and tested. Experimental measurements showed that, for given water temperature in tanks, T_out in the system with a vertical cylindrical tank was slightly higher than that in the one with a horizontal cylindrical tank; T_out increased with the increase of water temperature in the tank but was lower than the ambient air temperature all night. Meanwhile, a mathematical model was developed and experimentally validated for further investigating effects of structural and performance parameters of the system on T_out at clear nights. This model allows predicting T_out and the time at the moment ice formation inside absorber of the collector begins. Results by simulations showed that the collector-tank height difference and the thermal emissivity of absorbers had significant effects on the freeze protection of collectors in terms of T_out; for the system with a collector of non-selective absorber, the expected T_out was lower than the ambient air temperature, as observed in experiments; whereas for the system with a collector of solar selective absorber, the T_out, depending on water temperature in the storage tank, was higher than the ambient air temperature. This finding implied that, in thermosiphon DSWHs, flat-plate collectors with a non-solar-selective absorber might suffer from freezing-damage, but those with a solar selective absorber would not at clear nights with the ambient air temperature near or even lower than the freezing temperature.

[en] In this paper, a detailed mathematical procedure is developed to estimate daily collectible radiation on single tube of all-glass evacuated tube solar collectors based on solar geometry, knowledge of two-dimensional radiation transfer. Results shows that the annual collectible radiation on a tube is affected by many factors such as collector type, central distance between tubes, size of solar tubes, tilt and azimuth angles, use of diffuse flat reflector (DFR, in short); For collectors with identical parameters, T-type collectors (collectors with solar tubes tilt-arranged) annually collect slightly more radiation than H-type collectors (those with solar tubes horizontally arranged) do. The use of DFR can significantly improve the energy collection of collectors. Unlike the flat-plate collectors, all-glass evacuated tube solar collectors should be generally mounted with a tilt-angle less than the site latitude in order to maximize the annual energy collection. For most areas with the site latitude larger than 30^o in China, T-type collectors should be installed with a tilt-angle about 10^o less than the site latitude, whereas for H-type collectors without DFR, the reasonable tilt-angle should be about 20^o less than the site latitude. Effects of some parameters on the annual collectible radiation on the collectors are also presented.

[en] Highlights: • The first crystal structure of an anthracenone family agent complexed with tubulin. • Comparison of the binding mode between different agents reveals the inhibition mechanism. • This structure helps understand the results of the structure-activity-relationship (SAR) studies. Microtubules are composed of αβ-tubulin heterodimers and have been treated as highly attractive targets for antitumor drugs. A broad range of agents bind to tubulin and interfere with microtubule assembly, including colchicine binding site inhibitors (CBSIs). Tubulin Polymerization Inhibitor I (TPI1), a benzylidene derivative of 9(10H)-anthracenone, is a CBSI that inhibits the assembly of microtubules. However, for a long time, the design and development of anthracenone family drugs have been hindered by the lack of structural information of the tubulin-agent complex. Here we report a 2.3 Å crystal structure of tubulin complexed with TPI1, the first structure of anthracenone family agents. This complex structure reveals the interactions between TPI1 and tubulin, and thus provides insights into the development of new anthracenone derivatives targeting the colchicine binding site.