High-Efficiency Thermophotovoltaic System That Employs an Emitter Based on a Silicon Rod-Type Photonic Crystal

Abstract

Thermophotovoltaic systems in principle enable utilization of heat that is usually regarded as wasted energy. However, the wavelength selectivity of the thermal emitter required for high efficiencies is rather difficult to control with conventional designs.Here, we design a thermophotovoltaic system comprising silicon rods as thermal emitter with a relatively narrow emission spectrum and a photovoltaic cell with a band gap corresponding to 1.76 m, and verify efficient power generation. By accurately measuring the heat flux that enters the emitter, the emitter temperature, and the electrical output power of the photovoltaic cell, we find that the actual system efficiency (ratio of ingoing heat flux to output power) is 11.2% at an emitter temperature of 1338 K, and that the output power density footprint is 0.368 W/cm 2 . The obtained efficiency is relatively high, i.e., 1.65 times that of the previously reported record value (6.8%).Further efficiency improvements in the future may lead to development of distributed energy supplies using combustion heat.

Present Efficiencies and Future Opportunities in Thermophotovoltaics

“…These metrics are appropriate for the analysis of various TPV emitter-cell pairs and devices. If a study reports additional upstream losses, 14,22,26 those were decoupled to allow for direct comparison across TPV literature. We note that h pairwise is equivalent to h TPV in the case of an ideal, lossless cavity (Q abs = Q h ).…”

“…Both the leading LM InGaAs-and InGaAsSb-based sub-systems have well-designed cavities with view factors of 0.97 and 0.96, respectively. 14,26 Thus, the drop in performance is likely because the LM InGaAs and InGaAsSb cells used in the sub-system did not perform as well as the champion cells.…”

Integrated Near-Field Thermophotovoltaic Device Overcoming Blackbody Limit

“…[1][2][3][4][5][6] This concept has attracted significant attention in both fundamental science and various energy-related applications in recent years. The thermophotovoltaic (TPV) systems, [7][8][9][10][11][12][13] which convert heat into electricity by irradiating PV cells with thermal radiation from heated emitters, can significantly benefit from near-field thermal radiation transfer owing to the potential to increase output power density and conversion efficiency. [14][15][16][17][18][19] However, the benefit of near-field thermal radiation transfer has yet to be exploited in the real TPV systems because it is significantly challenging to realize a subwavelength gap and large temperature difference between a reasonably large emitter and PV cell while minimizing the thermal conduction loss.…”

“…Thermal radiation transfer between two objects that are separated by a subwavelength gap can be orders of magnitude larger than the maximal radiation transfer in free space (the blackbody limit) owing to the contribution of evanescent waves. − This concept has attracted significant attention in both fundamental science and various energy-related applications in recent years. The thermophotovoltaic (TPV) systems, − which convert heat into electricity by irradiating PV cells with thermal radiation from heated emitters, can significantly benefit from near-field thermal radiation transfer owing to the potential to increase output power density and conversion efficiency. − Since the first experimental investigation of near-field TPV systems in 2001, several quantitative demonstrations of near-field TPV systems have been reported in recent years. − For example, in ref , an 80-μm-diameter Si thermal emitter and a 300-μm × 300-μm mid-infrared photodetector were brought closer to a 60 nm distance using a piezo-controlled experimental setup, and 40-fold enhancement in the output power density was achieved. Another recent work demonstrated a near-field TPV system composed of a 40-μm-diameter graphite emitter and a 20-μm-diameter InSb PV cell cooled at 77 K, where an output power density of 0.75W/cm 2 and a near-field cell conversion efficiency of 14% were obtained (the detailed configurations and performances of the previous systems − are provided in Supporting Information (SI) Section 7).…”

Theory of exciton thermal radiation in semiconducting single-walled carbon nanotubes

“…Spectral control that relies on electronic structures in semiconductors has also attracted much attention. For a semiconductor photonic crystal, both the photonic bandgap and the electronic bandgap make strong contributions to fine spectral control [18][19][20]. The use of exciton resonance in semiconducting single-walled carbon nanotubes (SWCNTs) has also been recently proposed as a new approach [37].…”