Three-terminal heat engine and refrigerator based on superlattices

Abstract

We propose a three terminal heat engine based on semiconductor superlattices for energy harvesting. The periodicity of the superlattice structure creates an energy miniband, giving an energy window for allowed electron transport. We find that this device delivers a large power, nearly twice than the heat engine based on quantum wells, with a small reduction of efficiency. This engine also works as a refrigerator in a different regime of the system's parameters. The thermoelectric performance of the refrigerator is analyzed, including the cooling power and coefficient of performance in the optimized condition. We also calculate phonon heat current through the system, and explore the reduction of phonon heat current compared to the bulk material. The direct phonon heat current is negligible at low temperatures, but dominates over the electronic at room temperature and we discuss ways to reduce it.Comment: 11 pages, 8 figure

Incoherent scattering can favorably influence energy filtering in nanostructured thermoelectrics

“…While recent works throw some light on this topic [18][19][20][21][22][23][24][26][27][28][29] , we believe that a few aspects about energy filtering require attention: 1) Most of the current work is based on a linear response analysis of the Seebeck coefficient despite the fact that the regions in the vicinity of the barrier are strongly out of equilibrium. Linear response analysis typically masks the crucial transport physics that determines the delivered terminal power output and efficiency of the generator [30][31][32][33][34][35][36] .…”

“…where I C is the charge current, I Qe is the electronic heat current at the hot contact and V is the applied voltage assuming a voltage controlled set up described in recent literature [30][31][32][33][34][35][36] . Since thermal conductivity due to phonon doesn't vary significantly with the method employed to improve the thermoelectric performance (that is, Approach A or Approach B), we have simplified our calculations in (2) by neglecting the degradation in efficiency due to phonon heat conductivity.…”

Implementation of transmission functions for an optimized three-terminal quantum dot heat engine

“…Various layouts for such heat engines have been discussed, most of them based on quantum dots. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In particular, for the heat engine proposed in Ref. 4 two quantum dots with a single energy-level are used as energy filters in order to generate a directed charge current.…”

Optimized Peltier cooling via an array of quantum dots with stair-like ground-state energy configuration

“…There are two major pathways to improve the performance of Peltier coolers (i) decreasing the lattice thermal conductance (ii) enhancing the cooling power via suitable energy filtering techniques. Both of these techniques are widely employed to enhance the performance of thermoelectric generators [1][2][3][4][5][6][7][8][9] and coolers [11][12][13][14][15][16][17][20][21][22][23][24][25].Approaches towards the direction of nanostructuring as well as heterostructuring has so far proven successful in the suppressing phonon mediated lattice thermal conductivity via scattering and confinement of long wavelength phonons [32][33][34][35][36][37][38][39][40][41][42][43]. Hence, in this paper, we focus on optimizing the cooling power without the consideration for lattice thermal conductance.…”

“…With the recent advancement in fabrication and scaling technology, the rising dissipated heat density and temperature in nano devices have drawn special attention towards Peltier cooling. Peltier cooling, the reverse phenomenon of thermoelectric generation [1][2][3][4][5][6][7][8][9][10], is achieved by an energy selective flow of electronic current via energy filtering. This results in a disturbance of quasiequilibrium within a given energy range initiating abrorption of lattice heat in an attempt to establish equilibrium among the electronic population [11][12][13][14][15][16][17][18][19].…”