Thermophotovoltaics-development status and parametric considerations for power applications (original) (raw)
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Design and global optimization of high-efficiency solar thermal systems with tungsten cermets
Optics Express, 2011
Solar thermal, thermoelectric, and thermophotovoltaic (TPV) systems have high maximum theoretical efficiencies; experimental systems fall short because of losses by selective solar absorbers and TPV selective emitters. To improve these critical components, we study a class of materials known as cermets. While our approach is completely general, the most promising cermet candidate combines nanoparticles of silica and tungsten. We find that 4-layer silica-tungsten cermet selective solar absorbers can achieve thermal transfer efficiencies of 84.3% at 400 K, and 75.59% at 1000 K, exceeding comparable literature values. Three layer silica-tungsten cermets can also be used as selective emitters for InGaAsSb-based thermophotovoltaic systems, with projected overall system energy conversion efficiencies of 10.66% at 1000 K using realistic design parameters. The marginal benefit of adding more than 4 cermet layers is small (less than 0.26%, relative).
Solar thermal, thermoelectric, and thermophotovoltaic (TPV) systems have high maximum theoretical efficiencies; experimental systems fall short because of losses by selective solar absorbers and TPV selective emitters. To improve these critical components, we study a class of materials known as cermets. While our approach is completely general, the most promising cermet candidate combines nanoparticles of silica and tungsten. We find that 4-layer silica-tungsten cermet selective solar absorbers can achieve thermal transfer efficiencies of 84.3% at 400 K, and 75.59% at 1000 K, exceeding comparable literature values. Three layer silica-tungsten cermets can also be used as selective emitters for InGaAsSb-based thermophotovoltaic systems, with projected overall system energy conversion efficiencies of 10.66% at 1000 K using realistic design parameters. The marginal benefit of adding more than 4 cermet layers is small (less than 0.26%, relative).
Thermophotovoltaics convert heat into electricity via thermal radiation. The efficiency of this process depends critically on the selective emitter, which can be controlled by both the choice of the material and the emitter design. We find that surveying the set of refractory and near-refractory metals yields four primary candidates: tungsten, chromium, tantalum, and molybdenum. We developed a simulation tool known as TPVtest to consider the performance of each of these candidates. Tungsten yields the highest efficiencies at 35.20% at a temperature of 1573 K. However, molybdenum comes very close to this performance at 35.12% at the same temperature. Additionally, it presents the highest efficiency of 26.15% at the same temperature for a bandgap of 1.1 eV, as found in crystalline silicon. Furthermore, it may be possible to achieve improvements beyond the efficiencies quoted here by employing composite materials and advanced photovoltaic design concepts.
Performance of Tantalum-Tungsten Alloy Selective Emitters in Thermophotovoltaic Systems
Proceedings of SPIE - The International Society for Optical Engineering
A tantalum tungsten solid solution alloy, Ta 3% W, based 2D photonic crystal (PhC) was designed and fabricated for high-temperature energy conversion applications. Ta 3% W presents advantages compared to the non-alloys as it combines the better high-temperature thermomechanical properties of W with the more compliant material properties of Ta, allowing for a direct system integration path of the PhC as selective emitter/absorber into a spectrum of energy conversion systems. Indeed metallic PhCs are promising as high performance selective thermal emitters for thermophotovoltaics (TPV), solar thermal, and solar TPV applications due to the ability to tune their spectral properties and achieve highly selective emission. A 2D PhC was designed to have high spectral selectivity matched to the bandgap of a TPV cell using numerical simulations and fabricated using standard semiconductor processes. The emittance of the Ta 3% WPhC was obtained from near-normal reectance measurements at room te...
Improved Thermal Emitters for Thermophotovoltaic Energy Conversion
Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, 2016
Thermophotovoltaic (TPV) energy conversion enables millimeter scale power generation required for portable microelectronics, robotics, etc. In a TPV system, a heat source heats a selective emitter to incandescence, the radiation from which is incident on a low bandgap TPV cell. The selective emitter tailors the photonic density of states to produce spectrally confined selective emission of light matching the bandgap of the photovoltaic cell, enabling high heat-to-electricity conversion efficiency. The selective emitter requires: thermal stability at high-temperatures for long operational lifetimes, simple and relatively low-cost fabrication, as well as spectrally selective emission over a large uniform area. Generally, the selective emission can either originate from the natural material properties, such as in ytterbia or erbia emitters, or can be engineered through microstructuring. Our approach, the 2D photonic crystal fabricated in refractory metals, offers high spectral selectivity and high-temperature stability while being fabricated by standard semiconductor processes. In this work, we present a brief comparison of TPV system efficiencies using these different emitter technologies. We then focus on the design, fabrication, and characterization of our current 2D photonic crystal, which is a square lattice of cylindrical holes fabricated in a refractory metal substrate. The spectral performance and thermal stability of the fabricated photonic crystal thermal emitters are demonstrated and the efficiency gain of our model TPV system is characterized.
The challenge of high-performance selective emitters for thermophotovoltaic applications
Semiconductor Science and Technology, 2003
We present a brief survey of the most significant contributions to the study and the development of selective emitters for high-temperature applications. After a brief introduction and some necessary notes on definitions and experimental methods, this review presents the many different solutions proposed so far from the point of view of both the optimization of the functional properties of selective emitters and the fulfilment of the severe thermostructural requirements imposed by most high-temperature applications such as thermophotovoltaics.
Selective emitters for thermophotovoltaic applications
physica status solidi (a), 2016
Applying thermophotovoltaic (TPV) technologies to existing energy generators allows us to increase energy output while utilizing present infrastructure by reclaiming the heat lost during the production process. In order to maximize the efficiency of these sources, the conversion efficiency of the TPV system needs to be optimized. Selective emitters are often used to tailor the spectrum of incident light on the diode, blocking any undesirable light that may lead to device heating or recombination. Over the years, many different technologies have been researched to create an ideal selective emitter. Plasmas and rare-earth emitters provided highly selective spectra early on, but their fixed peaks required tailoring the diode's band gap to the emitter's characteristic wavelength. Recent advances in engineerable materials, such as photonic crystals and metamaterials, allow the opposite to take place; an appropriate selective emitter can be designed to match the TPV diode, allowing the diode structure to be optimized independently from the emitter.
Material candidates for thermally robust applications of selective thermophotovoltaic emitters
Physical Review Materials
As the majority of the input energy in power generation or energy consumption processes goes to waste as heat, thermophotovoltaic (TPV) devices enable energy recovery from (waste) heat. In TPV devices, the power output and conversion efficiency are impacted by thermal emitters. Since TPV devices operate at higher temperatures, emitters that can withstand hot environments without significant degradation of their emission performance are required. Refractory metals are commonly used as the emitter material due to their higher melting point and optical properties. This paper reviews physical and chemical properties of 15 refractory metals that may affect the emitter's performance at high temperatures: melting point, crystal structure, lattice constant, standard reduction potential, diffusion coefficient, Young's modulus, thermal expansion coefficient, and refractive index. Biological hazards and prices of the metals are also explored. Then, selective TPV emitters fabricated with the refractory metals are compared regarding their thermal stability. Finally, material properties are discussed toward achieving thermally robust TPV emitters.
An Ultra-High Temperature Stable Solar Absorber Using the ZrC-Based Cermets
Frontiers in Energy Research, 2021
Exploring the spectrally selective absorbers with high optical performance and excellent thermal stability is crucial to improve the conversion efficiency of solar energy to electricity in concentrated solar power (CSP) systems. However, there are limited reports on the selective solar absorbers utilized at 900oC or above. Herein, we developed a selective absorption coating based on the ultra-high temperature ceramic ZrC and the quasi-optical microcavity (QOM) optical structure, and experimentally achieved the absorber via depositing an all-ceramic multilayer films on a stainless steel substrate by magnetron sputtering. The prepared multi-layer selective absorber demonstrates an excellent high solar absorptance of ∼0.964 due to the multi absorptance mechanisms in the QOM, and a relatively low thermal emittance of ∼0.16 (82°C). Moreover, the coating can survive at 900oC in vacuum for 100 h with a superior spectral selectivity of 0.96/0.143 (82°C) upon annealing, resulting from the in...