Infrared materials for thermophotovoltaic applications (original) (raw)

Thermodynamic analysis of thermophotovoltaic efficiency and power density tradeoffs

Journal of Applied Physics, 2001

This report presents an assessment of the efficiency and power density limitations of thermophotovoltaic (TPV) energy conversion systems for both ideal (radiative-limited) and practical (defect-limited) systems. Thermodynamics is integrated into the unique process physics of TPV conversion, and used to define the intrinsic tradeoff between power density and efficiency. The results of the analysis reveal that the selection of diode bandgap sets a limit on achievable efficiency well below the traditional Carnot level. In addition it is shown that filter performance dominates diode performance in any practical TPV system and determines the optimum bandgap for a given radiator temperature. It is demonstrated that for a given radiator temperature, lower bandgap diodes enable both higher efficiency and power density when spectral control limitations are included. The goal of this work is to provide a better understanding of the basic system limitations that will enable successfiil long-term development of TPV energy conversion technology.

Ultraefficient thermophotovoltaic power conversion by band-edge spectral filtering

Proceedings of the National Academy of Sciences

Thermophotovoltaic power conversion utilizes thermal radiation from a local heat source to generate electricity in a photovoltaic cell. It was shown in recent years that the addition of a highly reflective rear mirror to a solar cell maximizes the extraction of luminescence. This, in turn, boosts the voltage, enabling the creation of record-breaking solar efficiency. Now we report that the rear mirror can be used to create thermophotovoltaic systems with unprecedented high thermophotovoltaic efficiency. This mirror reflects low-energy infrared photons back into the heat source, recovering their energy. Therefore, the rear mirror serves a dual function; boosting the voltage and reusing infrared thermal photons. This allows the possibility of a practical >50% efficient thermophotovoltaic system. Based on this reflective rear mirror concept, we report a thermophotovoltaic efficiency of 29.1 ± 0.4% at an emitter temperature of 1,207 °C.

The Status of Thermophotovoltaic Energy Conversion Technology at Lockheed Martin Corporation

2004

In a thermophotovoltaic (TPV) energy conversion system, a heated surface radiates in the mid-infrared range onto photocells which are sensitive at these energies. Part of the absorbed energy is converted into electric output. Conversion efficiency is maximized by reducing the absorption of non-convertible energy with some form of spectral control. In a TPV system, many technology options exist. Our development efforts have concentrated on flat-plate geometries with greybody radiators, front surface tandem filters and a multi-chip module (MCM) approach that allows selective fabrication processes to match cell performance. Recently, we discontinued development of GaInAsSb quaternary cell semiconductor material in favor of ternary GaInAs material. In our last publication (Ref. 1), the authors reported conversion efficiencies of about 20% (radiator 950°C, cells 22°C) for small modules (1-4 cm 2) tested in a prototypic cavity test environment. Recently, we have achieved measured conversion efficiencies of about 12.5% in larger (~100 cm 2) test arrays. The efficiency reduction in the larger arrays was probably due to quality and variation of the cells as well as non-uniform illumination from the hot radiator to the cold plate. Modules in these tests used GaInAsSb cells with 0.52 eV bandgap and front surface filters for spectral control. This paper provides details of the individual system components and the rationale for our technical decisions. It also describes the measurement techniques used to record these efficiencies.

Status of Thermophotovoltaic Energy Conversion Technology at Lockheed Martin Corp

2004

In a thennophotovoltaic VPV) energy conversion system, a heated surface radiates range onto photododes which are sensitive at these eneSg;es. Part of the absorbed energy is convetted into electric output. Conversion efficiency is maximized by reducing the absorption of non-convertible energy with some form of spectral control. In a TPV system, many technology options exist. Our development efforts have concentrated on flat-plate geometries with greybody radiators, low bandgap quaternary diodes, fiont surface tandem filters and a multi-chip module (MCM) approach that allows selective fabrication processes to match diode performance. the mid-hfiared Recently, the authors achieved conversion efficiencies of about 20% (radiator 9 W C , diodes 22°C) for a module in a prototypic cavity test enViranment. These tests employed InGaAsSb diodes w i t h 0.52 eV bandgap and front surface filters for spectral C O R~~O~. This papa provides details of the individual system c;omponents and describes the measurement technique used to record these efficiencies. S m Y Lockheed Martin bas been developing thermophotovoltaic (TPV) direct enedgy conversion f i x about eight years. Significant progress has been achieved i n four key areas: 1. Conversion EGciencv-significant progress has been made in conversion efficiency as shown in Figure 1. The latest modules made w i t h low-bandgap cells and ftont surface filters are about 20% efficient with a hot side radiator at 950°C aud the diodes near room temperature.

Thermophotovoltaic power conversion systems: current performance and future potential

Thermophotovoltaic (TPV) systems offer a unique, solid-state approach to converting heat into electricity based on thermal radiation. TPV is particularly suitable for certain classes of power generation applications that are not well served by standard engines, such as long, remote missions where repairs are difficult, and portable generation where space and weight are at a premium. While standard thermophotovoltaics are limited in their conversion efficiency, photonic crystals can improve performance by an order of magnitude for a number of systems.

An overview of the fifth conference on thermophotovoltaic generation of electricity

Semiconductor Science and Technology, 2003

In this paper, we discuss some of the highlights of the Fifth Conference on Thermophotovoltaic Generation of Electricity. The paper is organized into three principal sections, which deal with systems, infrared radiation emitters, and photovoltaic cells. Significant areas of progress and trends are identified in each of these areas. Progress is occurring at the fundamental level of materials' science, radiation physics, and systems. In the third of these topics, the quaternary alloy GaInAsSb appears to have become increasingly favoured. In the second topic, interesting developments in surface structured radiators and close-proximity radiators is discussed. Finally, we note that increased work on systems is still required, particularly for non-military applications.

Overview and Status of Thermophotovoltaic Systems

Energy Procedia, 2014

In the last decade thermophotovoltaic (TPV) generator has gained an increasing attention as cogeneration system for the distributed generation sector. Nevertheless, these systems are not fully developed and studied: several aspects need to be further investigated and completely understood. The aim of this study is to give a complete overview and the status of the art of thermophotovoltaic generation considering both the research developments and the experiences field. More in details, in this study, the characteristics of a TPV generator are analyzed with a particular attention to the physical relationships which govern the behavior of its main components. Moreover, the current technologies regarding the combustor, the emitter, the optical filter and the photovoltaic cells are investigated by taking into account both the role of each component and also their integration in the whole system. Finally, a critical review of the realized prototypes is presented and discussed.

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.

An overview of thermophotovoltaic generation of electricity

Solar Energy Materials and Solar Cells, 2001

This paper provides an overview of the developments in thermophotovoltaic (TPV) generation of electricity that have occurred relatively recently-from about 1994 to October 1998. The components considered are the semiconductor converter; the radiator; and the means of recirculating unusable, long-wavelength photons. A short account of the functions and performance of each of these components is given. Also discussed are operational systems and progress in modeling TPV systems.