Thermoelectric Generation Using Water Lenses

Abstract

A solar light concentrator is designed, which is composed of water and plastic transparent film. This flexible lens can trace the solar movement with the control of tensile stress and amount of water, and concentrate the solar energy to the thermoelectric module surface. The water lens was experimentally constructed and the concentrated intensity was monitored by the photodiode as the function of x-z positions. For example, when 3.0 kg of water was filled and a tension of 69.0 N/m was applied to the transparent vinyl sheet, the concentration ratio was evaluated as the maximum of 28.0 at a depth (657 mm) from the water lens bottom surface. TE generation was tested to show the validity of water lens and the surface condition of receiver was critical.

Using a Water Lens for Light Concentration in Thermoelectric Generation

“…The light intensity was measured using a photo diode with a light-receiving width of 2.7 mm, and the condensing ratio was calculated from the ratio of the electromotive force (EMF of photo diode) with and without the water lens. The EMF value showed a good linearity against the illumination of light source as reported in the previous paper [8] , and the open circuit voltage was taken as the measure of light intensity. Fig.…”

Dimensional Analysis of Thermoelectric Modules Under Constant Heat Flux

“…These data are used also for numerical evaluation. Assuming the weakly concentrated solar light as reported previously [10,11], Q was set to be 13.8 W for this module. This corresponds to the energy density of 25900 W/m 2 .…”

“…The solar concentration ratio is set roughly 30 against the natural solar light. This value was experimentally recorded as the typical concentration ratio on a TEM surface when the cylindrical water lens consisting of transparent sheet and water were used to focus in a single line [10,11]. In case of Frenel 9 lens this concentration ratio may arrive at 100 -200, although the irradiated surface area becomes as a point [1].…”

“…A parabolic mirror is also effective to concentrate solar energy [9]. Our previous study proposed a water lens consisting of cheap materials such as a transparent sheet and natural water [10], where the cylindrical lens can obtain the two dimensional concentration such as a linear focus. The lens shape was optimized to achieve the maximum concentration ratio as high as 70 [11].…”

Light-Concentration Characteristic of Water Lens and its Application to Thermoelectric Generation

“…This system could be easily constructed anywhere in the world because its components, water and a plastic sheet, are inexpensive and easily obtained. The condensing position of the water lens [6,7] can be adjusted to compensate for solar altitude variations without moving the position of the lens. Instead of mechanical movement, the tensile stress of the transparent sheet and the amount of water are controlled.…”