This study compared the health, performance, and behavior of individually and pair-housed calves fed milk ad libitum by artificial teats. Calves were separated from their dams within 24 h of birth and assigned to housing in either a single pen (10 calves) or a group pen (10 pairs of pair-housed calves). Calves were gradually weaned at approximately 5 wk of age and remained on the experiment until wk 8. Behavior was video recorded during wk 2 to 8. Before and after weaning, calves gained weight steadily with no differences between treatments. During the week of weaning, pair-housed calves continued to gain weight normally, but the individually housed calves experienced a growth check. There were no differences between groups in the amounts of milk, starter, or hay consumed, or in the incidence of scouring. There were also no differences in the amount of time spent self-grooming, sucking on the teat, or lying down. However, pair-housed calves spent more time standing inactive, more time moving, and less time with their head out of the pen than individually housed animals. Paired calves spent approximately 2% of the day in social contact, and the incidences of agonistic behavior and cross-sucking were very low. These results indicate that housing dairy calves in pairs allows benefits such as increased space for movement and social opportunities with no disadvantages in health and weight gains.
ITO-free organic solar cells with ink-jet printed current collecting grids and high conducting PEDOT:PSS as a composite anode are demonstrated. Inkjet printed current collecting grids with different crosssectional areas have been investigated. The effect of the width and height of the grid lines and busbars has been measured and modeled by direct current (DC) simulations. The electrical potential in devices with different grid profiles have been calculated and reveal critical bottlenecks in the grid electrode geometry, as the ability of the busbar to collect all the current. Experimentally, the upper limit of the conductivity of the ink-jet printed current collecting grids is limited by the topology of the grids and shadow losses in the solar cells.
The performance of perovskite PV modules, calculated using DC simulation, enables the identification of the most rational sub-cell dimensions in the modules.
Indium-tin-oxide (ITO) free polymer solar cells prepared by ink jet printing a composite front electrode comprising silver grid lines and a semitransparent PEDOT:PSS conductor are demonstrated. The effect of grid line density is explored for a large series of devices and a careful modeling study enabling the identification of the most rational grid structure is presented. Both optical and light beam induced current (LBIC) mapping of the devices are used to support the power loss model and to follow the evolution of the performance over time. Current generation is found to be evenly distributed over the active area initially progressing to a larger graduation in areas with different performance. Over time coating defects also become much more apparent in the LBIC images. Results and DiscussionA series of large area (2 cm × 2 cm) ITO-free organic solar cell devices were prepared on glass substrates (Figure 1). The devices contained current collecting grids/high conductivity PEDOT:PSS/P3HT:PCBM/LiF:Al. A schematic illustration of the devices is shown in Figure 1a. Current collecting grids are represented as parallel lines with different spacing (pitch size) ( Figure 1b). The devices with pitch sizes of 20, 10, 6.7, 5, 3.3, 2.5, 2, and 1 mm were prepared. The pitch size is defined as the distance between the centers of two neighboring grid lines. The number of the grid lines in the devices was changed as 1, 2, 3, 4, 6, 8, 10, and 20, respectively. The width of the grid lines was constant for each batch of devices. Thus shadowing losses increase with the number of grid lines. The effect of different pitch for the grid fingers was calculated at Fraunhofer ISE using a one dimensional numerical model developed by Glatthaar et al. [37,38] Each infinitesimal cell element with width dx delivers the current j(V(x))dx. The function j(V) is given by the current-voltage (JV)-curve of a small area device. Starting from x = 0 the current sums up to I(x) (Equation 1). This current leads to a voltage drop in the current collecting electrode corresponding to Ohm´s law (Equation 2), with ρ being the sheet resistance of the electrode(s). As the current output from the infinitesimal cell elements depends on the voltage V(x) at position x, also the current density j(V(x)) depends on the position x. Therefore the two differential Equations 1 and 2 are coupled:with the boundary conditions V (x = 0) = V 0 and I(x = 0) = 0.The area loss, which in a one dimensional model is the length l loss due to coverage with grid fingers or dead area due to series circuitry is accounted for by integrating the current I from 0 to the length of the active area l active but normalizing the current to the length including the lost "area" l active + l loss . The JV curve of the grid cell or module respectively therefore is given by:The model was used to consecutively calculate the ohmic and area losses in the PEDOT layer and metal fingers. The procedure was to first calculate the loss due to the distributed PEDOT resistance and only the shadow loss induced...
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