Array Sizing Research Articles

Sizing of the array for stand-alone photovoltaic systems

A brief critical review of stand-alone photovoltaic (SAPV) array sizing methods is presented, leading to the suggestion that a new class of methods is required in order to make the sizing exercise both accurate and accessible to a wide range of designers and users. The energy balance method is identified as an example of such a method. It is then used to obtain the array areas for a notional SAPV system situated in six widely-dispersed stations world-wide, with a total 24-hour load of 0.25, 2.5, or 25 kW h. Through correlational analysis of all the results and input data, it is recommended that the expression used to obtain array area is 1334 Q −2.272 TY L 0.986 with the terms and associated units being defined in the main body of the paper.

Optimal sizing of solar array and inverter in grid-connected photovoltaic systems

Abstract A new analytical approach is presented for finding the optimum ratio of photovoltaic array capacity to rated inverter input capacity in grid-connected photovoltaic systems. At optimum, the sizing ratio ranges from close to 1 for high insolation sites to well above 2 for low insolation conditions depending also on inverter characteristics and component costs. The sizing is more critical in low insolation conditions and the improvement of the economic performance thus obtained may be up to 20% compared to an inverter capacity equal to the PV-array. The optimum region is quite flat and up to ±20% deviations from the optimum point typically cause less than 2% losses. The analytical method coincides well with detailed numerical simulations for several locations (latitudes 33–60°N) and PV-array orientations used in the verification.

Structural alterations of chromosome 2 in Leishmania major as evidence for diploidy, including spontaneous amplification of the mini-exon array

We have utilized pulsed field electrophoresis to characterize several karyotypic alterations in Leishmania major. Promastigotes of the LT252 line contain three small chromosomes, of 300, 350 and 385 kb. Quantitative densitometry of ethidium bromide-stained gels suggest that these chromosomes are present in equal levels (2:2:2). Two derivatives of this line, one appearing spontaneously (LT252 Δ) and one obtained following selection with methotrexate (11-MTXR20), exhibit altered levels of these chromosomes, in the ratio of 2:1:3, respectively. The variant pattern in both lines is due to an increase in size of chromosome 2, yielding a new chromosome similar in size to chromosome 3. The enlarged chromosome 2 of the LT252 Δ line is a result of amplification of the mini-exon gene array normally located on this chromosome, which increases from about 93 to 150 copies of the 0.44-kb mini-exon tandem repeat, as shown by quantitative hybridization and sizing of the mini-exon array. In contrast, the increased size of chromosome 2 within the methotrexate-resistant mutant 11-MTXR20 is not due to mini-exon amplification. In both variant lines, there are equal levels of the wild-type and enlarged chromosome 2, and the wild-type chromosome 2 is now present at 50% of the level of chromosome 1. These and other data suggest that Leishmania is diploid for chromosomes bearing housekeeping genes such as the mini-exon locus.

Photovoltaic array sizing for Yemeni electrical needs

SYNOPSIS A behavioural model has been developed for correlating the area of the solar array, the capacity of the storage batteries, and the system cost of a roof-top or centralized solar-energy system relative to the average daily electricity demand. The mathematical analysis incorporates pertinent social, economic, climatic and energy-resource factors. The model is employed to predict the average daily electrical needs for any one of the ten common energy uses currently occurring in Yemeni houses, reviews these needs in terms of the available solar energy systems, selects the relevant system components, and suggests the most cost-effective appropriate design of solar photovoltaic system.

Investigations in array sizing 3. The center distance finding technique

A new technique (called Center Distance Finding, or CDF) is described to find the mean size and size distribution of monosize microspheres, using optical microscope. Two-dimensional contacting microsphere structures on a microscope slide are illuminated with parallel light. The spheres act as positive lenses, refracting the light into small focal spots that mark the locations of the sphere centers in a photomicrograph. Distances between focal spots contain the diameter information of interest. In support of these distance measurements, a precision technique for finding the microscope image magnification and distortion is given, and it is shown that the emulsion of the utilized Polaroid film has the needed dimensional stability. An error budget is given for this technique showing that nominal 10 μm spheres can be sized with a total error of ±0.04 μm in D and ±0.01 μm in σ D.

Investigations in Array Sizing Part I. Accuracy of the Sizing Process

The technique of two-dimensional array sizing by optical microscopy is investigated for use in the determination of the average diameter of 0.9 μm polystyrene latex spheres. Error sources for the diameter measurement are discussed, including the effects of microcracks, anisotropy, and dissolved impurities. The technique has been used in a particle calibration program at NBS. The average diameter found was 0.897 ± 0.016 μm, while techniques based on light scattering from a single particle and from a suspension yielded 0.900 ± 0.011 and 0.895 ± 0.008 μm, respectively.