Total Array Area Research Articles

PixeLite: A Thin and Wearable High Bandwidth Electroadhesive Haptic Array.

We present PixeLite, a novel haptic device that produces distributed lateral forces on the fingerpad. PixeLite is 0.15 mm thick, weighs 1.00 g, and consists of a 4×4 array of electroadhesive brakes ("pucks") that are each 1.5 mm in diameter and spaced 2.5 mm apart. The array is worn on the fingertip and slid across an electrically grounded countersurface. It can produce perceivable excitation up to 500 Hz. When a puck is activated at 150 V at 5 Hz, friction variation against the countersurface causes displacements of 627 ± 59 μm. The displacement amplitude decreases as frequency increases, and at 150 Hz is 47 ± 6 μm. The stiffness of the finger, however, causes a substantial amount of mechanical puck-to-puck coupling, which limits the ability of the array to create spatially localized and distributed effects. A first psychophysical experiment showed that PixeLite's sensations can be localized to an area of about 30% of the total array area. A second experiment, however, showed that exciting neighboring pucks out of phase with one another in a checkerboard pattern did not generate perceived relative motion. Instead, mechanical coupling dominates the motion, resulting in a single frequency felt by the bulk of the finger.

A novel design for solar integrated multi-effect distillation driven by sensible heat and alternate storage tanks

This article presents a novel Multi-Effect Distillation (MED) system which utilizes indirect brine heating such that a medium fluid is circulated through the concentrating solar collectors and store the energy in a charging tank. Each “effect” of a MED unit is a chamber in which cool feedwater brine is sprayed onto heat exchangers, partially evaporating the brine. The vapors and heated brine serve to pass thermal energy to subsequent effects. One of the uniqueness of the design is that the heat exchanger in the first effect of the system receives a flow of hot medium fluid, such that sensible heat is passed to the incoming feedwater. The thermal storage system consists of two identical, insulated tanks, each with sufficient volume to supply the medium fluid for a full day. A dynamic mathematical model is developed and simulated with four MED stages (“effects”). The number of concentrated solar arrays are optimized to generate a peak of 2200 metric ton per day of distilled water, with indispensable total array area of 92,000 square meter. The average daily performance ratio is 2, and the average specific thermal energy consumption is 1140 kJ per kg.

An assessment of solar-powered organic Rankine cycle systems for combined heating and power in UK domestic applications

Performance calculations are presented for a small-scale combined solar heat and power (CSHP) system based on an Organic Rankine Cycle (ORC), in order to investigate the potential of this technology for the combined provision of heating and power for domestic use in the UK. The system consists of a solar collector array of total area equivalent to that available on the roof of a typical UK home, an ORC engine featuring a generalised positive-displacement expander and a water-cooled condenser, and a hot water storage cylinder. Preheated water from the condenser is sent to the domestic hot water cylinder, which can also receive an indirect heating contribution from the solar collector. Annual simulations of the system are performed. The electrical power output from concentrating parabolic-trough (PTC) and non-concentrating evacuated-tube (ETC) collectors of the same total array area are compared. A parametric analysis and a life-cycle cost analysis are also performed, and the annual performance of the system is evaluated according to the total electrical power output and cost per unit generating capacity. A best-case average electrical power output of 89W (total of 776kWh/year) plus a hot water provision capacity equivalent to ∼80% of the total demand are demonstrated, for a whole system capital cost of £2700–£3900. Tracking PTCs are found to be very similar in performance to non-tracking ETCs with an average power output of 89W (776kWh/year) vs. 80W (701kWh/year).

Effect of cathode sheet resistance on segmented-in-series SOFC power density

Segmented-in-series solid oxide fuel cells with relatively short cell lengths of 1.4 mm were fabricated with varying LSM cathode current collector thicknesses. Increasing the LSM thickness from 11 to 91 μm yielded a factor of 2–3 area-specific resistance decrease and a similar power density increase. The maximum power density measured at 800 °C was 0.53 W cm−2 calculated based on total array area (including interconnect), and 0.9 W cm−2 calculated based on active cell area. A segmented-in-series electrical model was used to quantitatively explain the results based on the decreased cathode sheet resistance. The model also showed that the cell lengths were near optimal for maximizing the power density of these cells.

A miniaturized high-voltage solar cell array as an electrostatic MEMS power supply

A hydrogenated amorphous silicon (a-Si:H) solar cell array that is designed as an on-board power source for electrostatic microelectromechanical systems (MEMS) is presented. A single cell consists of a triple layer of p-i-n/p-i-n/p-i-n a-Si:H and produces an open circuit voltage (V/sub OC/) of 1.8/spl sim/2.3 V, a short circuit current density (J/sub SC/) of 2.8 mA/cm/sup 2/, and fill factor (FF) of 0.495. A series interconnected array of 100 single solar cells (total array area of 1 cm/sup 2/) is fabricated in an integrated fashion and produces an array V/sub OC/ of 150 V, and array short circuit current (I/sub SC/) of 2.8 /spl mu/A under Air Mass (AM) 1.5 illumination. To demonstrate the usefulness of this solar cell array as an on-board power source for electrostatically driven micromachined devices, it has been packaged with a movable micromachined silicon (Si) mirror in a hybrid manner. The movable Si mirror is directly driven by the cell array electrical output, and the motion of the mirror plate has been observed reproducibly. Variation of light intensity and/or number of illuminated cells produces different values of array V/sub OC/, thus enabling control of the deflection of the Si mirror by variation of incident light intensity. >

On Arrays with Nonrigid Interstices

The radiation from an infinite phased planar array of rectangular pistons with nonrigid interstices is considered. Numerical calculations for exact equations are compared with a simple approximation, derived for small pistons close together. The comparisons show that the approximate expressions agree well with the exact results even for pistons of practical size, if (1) the array is steered to an angle near broadside, (2) the interstitial impedance is not very low, and (3) the interstices occupy a small fraction of the total array area.

Nearfield Pressure for a Steered Array of Strips

The nearfield pressure and the cavitation-limited power output of a steered array of infinite strips in an infinite rigid-plane baffle is calculated. The strips have the same velocity magnitude. The pressure distribution on the surface of the array is almost constant for an array steered to broadside, and it becomes undulatory as the array is steered away from broadside. When the strips occupy a large fraction of the total array area, the peak pressure occurs off the surface of the array for an array steered to broadside. Near endfire, for the same ratio of the strip areas to the total array area, small strips closer together have a lower peak pressure than large strips farther apart. The mutual-coupling coefficients and the radiation impedances of strips are also calculated. For an array steered to broadside or for an array with strip widths much less than a wavelength, one can find approximately the peak pressure magnitude from the magnitude of the maximum impedance.