Query: A nanophotonic solar thermophotovoltaic device

Candidate papers:

abstract: The most common approaches to generating power from sunlight are either photovoltaic, in which sunlight directly excites electron hole pairs in a semiconductor, or solar thermal, in which sunlight drives a mechanical heat engine. Photovoltaic power generation is intermittent and typically only exploits a portion of the solar spectrum efficiently, whereas the intrinsic irreversibilities of small heat engines make the solar thermal approach best suited for utility scale power plants. There is, therefore, an increasing need for hybrid technologies for solar power generation. By converting sunlight into thermal emission tuned to energies directly above the photovoltaic bandgap using a hot absorber emitter, solar thermophotovoltaics promise to leverage the benefits of both approaches: high efficiency, by harnessing the entire solar spectrum; scalability and compactness, because of their solid state nature; and dispatchablility, owing to the ability to store energy using thermal or chemical means. However, efficient collection of sunlight in the absorber and spectral control in the emitter are particularly challenging at high operating temperatures. This drawback has limited previous experimental demonstrations of this approach to conversion efficiencies around or below 1% (refs 9, 10, 11) Here, we report on a full solar thermophotovoltaic device, which, thanks to the nanophotonic properties of the absorber emitter surface, reaches experimental efficiencies of 3.2% The device integrates a multiwalled carbon nanotube absorber and a one dimensional Si/SiO2 photonic crystal emitter on the same substrate, with the absorber emitter areas optimized to tune the energy balance of the device. Our device is planar and compact and could become a viable option for high performance solar thermophotovoltaic energy conversion.
author_names: Andrej Lenert

David M Bierman

Youngsuk Nam

Walker R Chan

Ivan Celanovic

Marin Soljacic

Evelyn N Wang
title: A nanophotonic solar thermophotovoltaic device.
venue: Nature nanotechnology
year: 2014

abstract: Eq. 1 in this Letter (and also, Eq. 1.133 in ref 2) represents the temperature required for the maximum of Planck's distribution expressed in units of wavelength to match the bandgap energy. However, the energy at which the maximum occurs depends on whether we consider energy flux per unit frequency range or per unit wavelength range3,4. A more appropriate approximation matches the maximum of Planck's distribution expressed in units of frequency or energy to the bandgap energy, the scaling factor in this case is 4114 K/eV.
author_names: Andrej Lenert

David M Bierman

Youngsuk Nam

Walker R Chan

Ivan Celanovic

Marin Soljacic

Evelyn N Wang
title: Addendum: A nanophotonic solar thermophotovoltaic device.
venue: Nature nanotechnology
year: 2015

author_names: Andrej Lenert

David M Bierman

Youngsuk Nam

Walker R Chan

Ivan Celanovic

Marin Soljacic

Evelyn N Wang
title: Erratum: A nanophotonic solar thermophotovoltaic device (Nature Nanotechnology (2014) 9 (126 130)
year: 2015

abstract: Solar thermal energy conversion can harness the entire solar spectrum and theoretically achieve very high efficiencies while interfacing with thermal storage or back up systems for dispatchable power generation. Nanostructured materials allow us to tune the spectral properties and heat transfer behavior to enable such systems. However, under high temperature conditions, thermal management, system optimization and minimization of parasitic losses are necessary to achieve competitive solar power generation. This thesis seeks to achieve spectral control and thermal management through manipulation of nanostructured materials. First, this thesis presents the design and development of a nanophotonic solar thermophotovoltaic (STPV) that harnesses the full spectrum of the sun, in a solid state and scalable way. Through device optimization and control over spectral properties at high temperatures 1300 K) a device that is 3 times more efficient than previous STPVs is demonstrated. To achieve this result, a framework was developed to identify which parts of the spectrum are critical and to guide the design of nanostructured absorbers and emitters for STPVs. The work elucidated the relative importance of spectral properties depending on the operating regime and device geometry. Carbon nanotubes and a silicon/silicon dioxide photonic crystal were used to target critical properties in the high solar concentration regime; and two dimensional metallic photonic crystals were used to target critical properties in the low solar concentration regime. A versatile 5 experimental platform was developed to interchangeably test different STPV components without sacrificing experimental control. In addition to demonstrating significant improvements in STPV efficiency, an experimental procedure to quantify the energy conversion and loss mechanisms helped improve and validate STPV models. Using these validated models, this thesis presents a scaled up device that can achieve 20% efficiencies in the near term. With potential integration of thermal based storage, such a technology can supply power efficiently and on demand, which will have significant implications for adoption of STPVs. Second, the thesis shifts focus away from solid state systems to thermal fluid systems. A new figure of merit was proposed to capture the thermal storage, heat transfer and pumping power requirements for a heat transfer fluid is a solar thermal system. Existing and emerging fluids were evaluated based on the new metric as well as practical issues. Finally, sub micron phase change material (PCM) suspensions are investigated for simultaneous enhancement of local heat transfer and thermal storage capacity in solar thermal systems. A physical model was developed to explain the local heat transfer characteristics of a flowing PCM suspension undergoing melting. A mechanism for enhancement of heat transfer through.control over the distribution of PCM particles inside a channel was discovered and explained. Together, this thesis makes significant contributions towards improving our understanding of the role and the effective use of nanostructured materials in solar thermal systems. Thesis Committee Chair: Professor Evelyn N. Wang, Department of Mechanical Engineering, MIT Thesis Committee Members: Professor Gang Chen, Department of Mechanical Engineering, MIT Professor Carl V. Thompson, Department of Material Science and Engineering, MIT
author_names: Andrej Lenert
title: Tuning energy transport in solar thermal systems using nanostructured materials
year: 2014

author_names: Youngsuk Nam

Andrej Lenert

David M Bierman

Evelyn N Wang
title: Solar Thermophotovoltaic Devices with Nanophotonic Absorbers and Emitters
year: 2014

abstract: The overall efficiency of solar thermophotovoltaic (STPV) systems, which can theoretically reach 85.4% is function of a large number of parameters, such as concentration factor, device geometry, cell bandgap, absorber and cell temperatures, In actual STPV devices, the cell temperature depends on the chosen configuration and on the characteristics of the cooling system, i.e. temperature and heat transfer coefficient. This article presents an original optimization that takes into account the thermal equilibrium of the PV cell. Simulations demonstrate the impact of the thermal boundary conditions on the optimum set of parameters for STPV power generation. These results highlight the importance of considering the thermal behavior in the global optimization of experimental STPV devices.
author_names: Olivier Dupre

Rodolphe Vaillon

Martin A Green
title: Optimization of solar thermophotovoltaic systems including the thermal balance
venue: 2017 IEEE 44th Photovoltaic Specialist Conference (PVSC)
year: 2017

abstract: The overall efficiency of solar thermophotovoltaic (STPV) systems, which can theoretically reach 85.4% is function of a large number of parameters, such as concentration factor, device geometry, cell bandgap, absorber and cell temperatures, In actual STPV devices, the cell temperature depends on the chosen configuration and on the characteristics of the cooling system, i.e. temperature and heat transfer coefficient. This article presents an original optimization that takes into account the thermal equilibrium of the PV cell. Simulations demonstrate the impact of the thermal boundary conditions on the optimum set of parameters for STPV power generation. These results highlight the importance of considering the thermal behavior in the global optimization of experimental STPV devices.
author_names: Olivier Dupre

Rodolphe Vaillon

Martin A Green
title: Optimization of solar thermophotovoltaic systems including the thermal balance
venue: 2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)
year: 2016

abstract: Summary Recent trends in photovoltaics demand ever thin solar cells to allow deployment in consumer oriented products requiring low cost and mechanically flexible devices. For this, nanophotonic elements in the wave optics regime are highly promising, as they capture and trap light in the cells' absorber, enabling its thickness reduction while improving its efficiency. Here, novel wavelength sized photonic structures were computationally optimized toward maximum broadband light absorption. Thin film silicon cells were the test bed to determine the best performing parameters and study their optical effects. Pronounced photocurrent enhancements, up to 37% 27% and 48% respectively, in ultra thin (100 and 300 nm thick) amorphous, and thin (1.5 mm) crystalline silicon cells are demonstrated with honeycomb arrays of semi spheroidal dome or void like elements patterned on the cells' front. Also importantly, key advantages in the electrical performance are anticipated, since the photonic nano/micro nanostructures do not increase the cell roughness, therefore not contributing to recombination, which is a crucial drawback in state of the art light trapping approaches.
author_names: Manuel J Mendes

Sirazul Haque

Olalla Sanchez-Sobrado

Andreia Araujo

Hugo Aguas

Elvira Fortunato

Rodrigo Martins
title: Optimal Enhanced Solar Cell Ultra thinning with Broadband Nanophotonic Light Capture
venue: iScience
year: 2018

abstract: We have demonstrated world record thermophotovoltaic (TPV) conversion efficiency in two materials systems operating at two different thermal emitter temperatures. A GaAs based PV device under a 2330 degC thermal emitter produced an efficiency of (31 2) and an In0.53Ga0.47As based PV device under a 1300 degC thermal emitter produced an efficiency of (30 2) The electrical output power densities of the cells were 2.45 W/cm2 and 0.658 W/cm2, respectively. Critical to these high efficiencies were the cells' high reflectance of photon energies below the absorber band gap. Unlike solar PV, for which sub band gap (SBG) light is lost, a TPV cell can reflect SBG light back to the thermal emitter where it can be recycled. The demonstrations were made on a custom built measurement platform in which a 100 cm2 graphite thermal emitter was heated under vacuum. The TPV efficiencies were evaluated by comparing the measured electrical output power of the cell with the total power absorbed by the cell. The measured TPV efficiencies as a function of thermal emitter temperature were corroborated by our full system modeling. As far as the authors are aware, these are the highest TPV conversion efficiencies ever measured, and device improvements should yield 40% efficiency in the near future.
author_names: Tarun C Narayan

Leah Y Kuritzky

Dustin P Nizamian

Benjamin Anders Johnson

Eric J Tervo

Alexandra R Young

Cecilia Luciano

Madhan K Arulanandam

Brendan M Kayes

Emmett E Perl

Moritz Limpinsel

Parthiban Santhanam

Jonathan Slack

Waldo J Olavarria

Jeffrey J Carapella

Michelle S Young

Cheng-Lun Wu

Zhengshan J Yu

Zachary C Holman

Richard R King

Myles A Steiner

David M Bierman

Andrew J Ponec

Justin A Briggs
title: World record demonstration of 30% thermophotovoltaic conversion efficiency
venue: 2020 47th IEEE Photovoltaic Specialists Conference (PVSC)
year: 2020

abstract: We demonstrate an inverted metamorphic multijunction (IMM) photovoltaic cell comprising lattice mismatched 1.2 eV AlGaInAs and 1.0 eV GaInAs junctions optimized for high temperature thermophotovoltaic (TPV) applications. This device differs from traditional IMM solar cells because the mismatched junctions are grown at a single lattice constant. This architecture enables removal of the compositionally graded buffer that otherwise filters light from the junctions below and absorbs sub bandgap light via free carrier absorption. Sub bandgap absorption dramatically reduces the efficiency of TPV systems using high reflectivity cells to enable band edge spectrum filtering. Three components required development to enable this device: (1) a lattice mismatched 1.2 eV AlGaInAs junction, (2) a metamorphic contact layer grown after the graded buffer, and (3) a transparent tunnel junction that sits in front of the 1.0 eV GaInAs junction. Growth conditions that minimize oxygen defect incorporation maximize AlGaInAs cell quality, enabling a 0.41 V bandgap open circuit voltage offset at 22 mA/cm2 under AM1.5D. A mismatched GaInAs:Se layer is developed as a low resistance contact. Lastly, we develop a GaAsSb:C/GaInP:Se tunnel junction suitable for high power densities with more transparency than the GaAsSb:C/GaInAs:Se structure used in past IMM cells. We characterize the tandem device under a high intensity spectrum that approximates the emission from a 2150 degC blackbody radiator and deduce a projected ideal TPV efficiency of 39.9% at ~30% of the blackbody irradiance and 36% ideal TPV efficiency under the full 118 W/cm2 irradiance. Improvements to the back surface reflectivity and series resistance are expected to increase the ideal TPV efficiency well above 40%
author_names: Kevin L Schulte

Ryan M France

Daniel J Friedman

Alina LaPotin

Asegun Henry

Myles A Steiner
title: Inverted metamorphic AlGaInAs/GaInAs tandem thermophotovoltaic cell designed for thermal energy grid storage application
year: 2020