Relative performance of tracking versus fixed tilt photovoltaic systems in the USA

Tracking systems can increase the amount of electricity generated by photovoltaic (PV) modules, by actively orienting each module to intercept more solar energy. We find that horizontal one‐axis tracking systems can increase PV generation by 12–25% relative to south‐facing fixed mount PV systems with 25° tilts in the contiguous USA, and two‐axis tracking systems can increase PV generation by 30–45% relative to fixed mount systems. Tracking systems increase PV generation more significantly in arid regions such as the southwest USA than in humid regions with persistent cloud cover such as the Pacific Northwest and coastal Atlantic states. We find that fixed and tracking PV systems have similar interannual variability in their generation profiles, and this variability is primarily driven by project location. Tracking PV projects cost more than fixed tilt systems, per unit capacity, and we explore how much more tracking projects could cost while generating similar levelized costs of energy as fixed tilt systems. We define this as the breakeven additional cost of tracking and find that it is primarily driven by three factors: (i) regional tracking performance, (ii) fixed tilt system costs that tracking projects compete against, and (iii) additional tracking operation and maintenance costs. Using this framework, we explore the relative competitiveness of tracking systems for a range of fixed and tracking PV prices and evaluate how tracking competitiveness varies by region. Copyright © 2013 John Wiley & Sons, Ltd.     

Forward-bias impedance of GaAs1-xPx LED's

The forward bias impedance characteristics of GaAs_1-xP_x LED's have been determined. In all cases, the equivalent parallel capacitance reaches a maximum and then either saturates (x = 0.4) or becomes negative at certain frequencies (x = 0.85 and x = 1). The current densities at which C_p maxima are reached are below typical values for display, multiplexing or optical emitters applications (i.e. J_F = 1 A/cm² for x = 0.85). It is suggested large series resistances for x = 0.4, and conductivity modulation effects for x > 0.4 are responsible for the above impedance behavior.     

SORPTION EQUILIBRIUM OF COPPER BY PARTIALLY-COAGULATED CALCIUM ALGINATE GEL

The sorption equilibrium of dissolved copper by spherical partially-coagulated gels of calcium alginate was investigated in this work. The gels were formed by dispensing a viscous algin (food grade sodium alginate from kelp) solution with a multi-tip dispenser into 0.05 M CaCl₂ solution in a loop fluidized bed reactor. The resultant semi-rigid spherical gels were then transferred to another reactor operated batch wise to absorb dissolved copper at low concentrations (10-40 ppm). When the concentration of the inert neutral salt NaNO₃, added to the reactor fluid was 0.01 M, the amount of copper absorbed was found to be substantially higher than that at 0.1 MNaN0₃. The conventional Langmuir's model based on the concentration of copper in solution yielded different values of conditional stability constant at different ionic strengths in the reactor fluid. However, by defining the copper-binding stability constant on the basis of copper activity in the gel phase with the competition from calcium for metal binding sites taken into account, a unique copper-binding stability constant and a unique calcium-binding stability constant were obtained. The numerical procedure for estimating the activity of copper in the gel fluid was modified from Jang et al. Water Research, 1990, in press).     

Fully integrated MIXLER based on VHF CMOS-MEMS clamped-clamped beam resonator

The design and test of a fully integrated CMOS-MEMS-MIXLER, using a commercial technology (AMS 0.35 mum) is presented. The MEMS structure is basically a clamped-clamped beam resonator implemented with the polysilicon capacitance module of the selected technology, showing a fundamental lateral resonance frequency of 22.5 MHz. Two different approaches based, respectively, on the nonlinearity of the voltage against the excitation force and on the amplitude modulation of the excitation signal, have been proposed in order to operate the MEMS as a MIXLER     

Matching degradation of threshold voltage and gate voltage of NMOSFET after Hot Carrier Injection stress

Device degradation modelling is more and more important for reliable circuit design. On MOSFET, the threshold voltage drift in time can lead to circuit performance degradation. In this study, V_T shift due to Hot Carrier Injection stress is accelerated on small width devices. V_T matching is also degraded during stress as a function of V_T deterioration. This width dependence allows explaining gate voltage matching behavior in the sub-threshold area used in low power analog applications.     

Multicarrier modem for digital HDTV terrestrial broadcasting

A digital modulation system using orthogonal frequency division and multiplexing (OFDM) is addressed in this paper. Such a system presents the advantage of coping with echoes more easily than classical single-carrier modems, thanks to the insertion of a guard interval between two symbols. The signal equalization is then achieved in the frequency domain. This OFDM modem is improved by using dual polarizations. In this configuration, it can convey a 70 Mbits/s (HDTV) bit stream in an 8 MHz UHF channel. Some experimental results relate field trials carried out in several countries with such equipment.     

Impact of the gain saturation dynamics in semiconductor optical amplifiers on the characteristics of an analog optical link

We evaluate both theoretically and experimentally the gain saturation dynamics of semiconductor optical amplifiers when inserted into an analog optical link. Its impact in terms of radio frequency response, nonlinearity, and noise is investigated. In particular, the frequency response is shown to be a peculiar high-pass filter exhibiting two characteristic frequencies.     

Influence of an inhibitor of monoaminooxidase (nialamide) on the serum levels, urinary excretion and plasma clearance of urea, uric acid and creatinine in adult and growing rats

Serum levels, urinary excretion and plasma clearance of urea, uric acid and creatinine were studied in adult (230 g) and growing (75 g) rats under the influence of nialamide (an IMAO) administered in daily doses of 20 mg/100 g diet during 15 or 30 days in adults and 10 mg/100 g diet during 15 days in growing rats. A pair feeding design was used in both ages. Serum levels of urea rose in adult rats fed nialamide for 30 days while urinary excretion decreased. No change in serum levels were noted in growing rats although urinary excretion showed a net increase. Serum uric acid levels were increased in adult female rats given nialamide for 30 days, while urinary excretion fell in both sexes. Growing rats showed a drop in urinary excretion of uric acid. Serum creatinine levels were unchanged in adult and growing rats after treatment with nialamide, although a marked increase was recorded in urinary excretion in both groups.     

Efficient design of gallium arsenide Muller-C element

A Muller-C element is a fundamental building block of a handshake path in self-timed digital circuits. It is a basic event driven logic (EDL) gate, implementing the AND function for events. The authors present a new, improved design of the Muller-C element using GaAs MESFET technology. A static Muller-C gate is implemented that incorporates modifications of newly introduced, GaAs pseudodynamic latched logic family (PDLL) primitives. The circuit is characterised by very high speed and low power dissipation