Selective solar absorbers are key elements of all solar thermal systems. Solar thermal panels and Concentrated Solar
Power (CSP) systems aim respectively at producing heat and electricity. In both cases, a surface receives the solar
radiation and is designed to have the highest optical absorption (lowest optical reflectivity) of the solar radiation in the
visible wavelength range where the solar intensity is the highest. It also has a low emissivity in the infrared (IR) range in
order to avoid radiative thermal losses. Current solutions in the state of the art usually consist in deposited interferential
thin films or in cermets [1]. Structured surfaces have been proposed and have been simulated because they are supposed
to be more efficient when the solar radiation is not normal to the receiving surface and because they could potentially be
fabricated with refractory materials able to sustain high operating temperatures. This work presents a new method to
fabricate micro/nanostructured surfaces on molybdenum (refractory metal with a melting temperature of 2623°C). This
method now allows obtaining a refractory selective surface with an excellent optical selectivity and a very high
absorption in the visible range. This high absorption performance was obtained by achieving a double structuration at
micro and nano scales thanks to an innovative process flow.
KEYWORDS: Transducers, Ferroelectric polymers, Solar energy, Thin films, Capacitance, Thin film devices, Energy harvesting, Energy efficiency, Electronic circuits, Energy conversion efficiency
The paper presents the examination of modern flexible piezoelectric thin films made of PVDF (polyvinylidene
difluoride) in terms of their application in electromechanical transducers, a brief overview of available piezoelectric
materials and energy harvesting devices based on piezoelectric. In order to assess the usefulness of these films from the
perspective of described devices, the energy efficiency coefficient determined under the pulse excitation conditions was
taken into account. Normalized volumetric efficiency ratio allows to evaluate the commercially available flexible
piezoelectric films.
Micro/nanotechnologies evolve causing an evolution of surface characterization systems of thin films. Today, these systems are not adapted to the future needs (or current) to characterize and qualify a large effective area within industrial production. This concerns the thin film active layers or simple mask for structuring the surface. This paper proposes a quality control method for thin films of self-assembled particles and high quality. This method is founded on the intersection of several skills available in our laboratories: Industrial process of visual inspection, optical methods for quality control (large area relative to the state of the art) and advances in micro/nanotechnology (CEA/Liten).
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