Installation Design for Valve-Regulated Sealed Lead-Acid Batteries in Generating Stations
Commercially available large-capacity valve-regulated sealed lead-acid batteries represent a novel technology for large stationary batteries for emergency power applications, using an oxygen recombinant cycle to inhibit the generation of hydrogen under normal operation. A discussion is presented of the installation design for these batteries, making comparisons to traditional vented lead-acid cells as appropriate. The operation of the valve-regulated sealed lead-acid battery is also described. >
The Development of Sealed Lead-Acid Stationary Battery having Large Capacity for Improving Telecommunication Systems
The sealed lead-acid stationary batteries having capacities in the range of 200 Ah to 1000 Ah have been developed lately by Yuasa. The principal features of these batteries are as follows: 1) These batteries are about 15% superior in discharge capacity at one hour rate compared with a conventional flooded battery. 2) The expected service life of these batteries used in float service is more than 10 years. 3) These batteries can be placed on their side without deterioration in their capacity with respect to time. Hence, the space for installation of an assembly of the batteries can be decreased to 60% to 80% of that for an assembly of the conventional flooded batteries. 4) The batteries can be provided with a connector for the battery voltage and temperature, fixed to each battery beforehand, which can be connected with a single touch to make it easy to monitor the battery condition. 5) No gas is generated during normal float service, and hence the battery can be installed in the vicinity of its load, such as electric telecommunication equipment, without the need for preparing a special battery room.
Velocity moments in alongshore bottom stress parameterizations
The time-averaged alongshore bottom stress is an important component of nearshore circulation models. In a widely accepted formulation the bottom stress is proportional to , the time average of the product of the instantaneous velocity magnitude |u→| and the instantaneous alongshore velocity component υ. Both mean and fluctuating (owing to random, directionally spread waves) velocities contribute to . Direct estimation of requires a more detailed specification of the velocity field than is usually available, so the term is parameterized. Here direct estimates of based on time series of near-bottom currents observed between the shoreline and 8-m water depth are used to test the accuracy of parameterizations. Common parameterizations that are linear in the mean alongshore current significantly underestimate for moderately strong alongshore currents, resulting in overestimation of a drag coefficient determined by fitting modeled (with a linearized bottom stress) to observed alongshore currents. A parameterization based on a joint-Gaussian velocity field with the observed velocity statistics gives excellent overall agreement with the directly estimated and allows analytic investigation of the statistical properties of the velocity field that govern . Except for the weakest flows, depends strongly on the mean alongshore current and the total velocity variance but depends only weakly on the mean wave angle, wave directional spread, and mean cross-shore current. Several other nonlinear parameterizations of are shown to be more accurate than the linear parameterizations and are adequate for many modeling purposes.