Small-Scale Flat Plate Collectors for Solar Thermal Scavenging in Low Conductivity Environments

Abstract

There is great opportunity to develop power supplies for autonomous application on the small scale. For example, remote environmental sensors may be powered through the harvesting of ambient thermal energy and heating of a thermoelectric generator. This work investigates a small-scale (centimeters) solar thermal collector designed for this application. The absorber is coated with a unique selective coating and then studied in a low pressure environment to increase performance. A numerical model that is used to predict the performance of the collector plate is developed. This is validated based on benchtop testing of a fabricated collector plate in a low-pressure enclosure. Model results indicate that simulated solar input of about 800 W/m 2 results in a collector plate temperature of 298 K in ambient conditions and up to 388 K in vacuum. The model also predicts the various losses in W/m 2 K from the plate to the surroundings. Plate temperature is validated through the experimental work showing that the model is useful to the future design of these small-scale solar thermal energy collectors.

Ellipsoidal Optical Cavities for Enhanced Thermophotovoltaics

“…where, k c is the thermal conductivity of air at atmospheric pressure, T avg is the average temperature between the emitter and PV cell, P is the reduced pressure in units of Pascals, and d is the distance between the emitter and PV cell. It is assumed convective heat transfer is suppressed at the low operating pressures considered and its effects are neglected [49], [50]. Moreover, the convective heat transfer coefficient between the outer shell of the ellipsoidal cavity and the surrounding environment is set to hc = 10 W/m 2 •K.…”

Experimental performance analysis of a novel sand coated and sand filled polycarbonate sheet based solar air collector

“…Wire mesh SAC with dual pass provided highest temperature of 25.2˚C and maximum efficiency of 76.46% than other conditions. Special selective coatings on the surface of absorber plate such as nickel-tin [12], mixture of vanadium and aluminium oxides [13] were also employed to obtain high effectiveness in solar air collectors.…”

Power Generation via Small Length Scale Thermo-Mechanical Systems: Current Status and Challenges, a Review

“…In general, thermal energy harvesting implies producing power from heat sources that are considered waste or secondary; some harvesting approaches include material-specific approaches such as thermoelectric devices [14,15]. An alternative harvesting mechanism is through boiler-expander systems [10,12,13] with applications ranging from waste heat [15] to solar thermal harvesting [16][17][18].…”