Thermoelectrics: Direct Solar Thermal Energy Conversion

Abstract

The field of thermoelectricity began in the early 1800s with the discovery of the thermoelectric effect by Thomas Seebeck. Seebeck found that, when the junctions of two dissimilar materials are held at different temperatures (ΔT), a voltage (V) is generated that is proportional to ΔT. The proportionality constant is the Seebeck coeffcient or thermopower: α = −δV/ΔT. When the circuit is closed, this couple allows for direct conversion of thermal energy (heat) to electrical energy. The conversion effciency, ηTE, is related to a quantity called the fgure of merit, ZT, that is determined by three main material parameters: the thermopower α, the electrical resistivity ρ, and the thermal conductivity κ.

Spectrum splitting for efficient utilization of solar radiation: a novel photovoltaic–thermoelectric power generation system

“…As shown in the figure, the cut-off wavelength of Fig. 1 Simplified solar spectrum and energy ratios to be used within the PV cell and the TEG (Tritt et al 2008) this mirror is 700 nm, a little bit lower than the desired 800 nm, this leads to an approximate 50/50 splitting of the energy in the setup.…”

“…The basic idea for a combined PV and thermoelectric solar cell has been published in 2008 (Tritt et al 2008). The history of thermoelectricity began in 1823 when Seebeck made his experiments about the conversion of a temperature gradient into an electrical current (Seebeck 1895).…”

“…The higher the ZT value of the material the closer is the efficiency to the Carnot limit. Modern thermoelectric materials reach ZT values larger than 1 and with efficiencies more than 4 % (Tritt et al 2008). Using the technique of thermoelectric generators, to convert the infrared part of the sun spectrum into electrical energy, we could increase the overall performance of a combined PV and TE solar cell by approximately 10 % of the PV, thereby achieving around 20 % efficiency with the combined system rather than the 17-18 % efficiency from the PV-only setup.…”

“…The basic idea of PV-TE was introduced by Tritt (2008) and Kraemer et al (2011) who studied the utilization of both ultraviolet (UV) and infrared (IR) parts. Various papers have been published dealing with the combined use of thermoelectric and PV or solar thermal systems.…”

Energy Analyses of Thermoelectric Renewable Energy Sources

“…The use of the solar thermoelectric generator usually combines a solar thermal collector with a thermoelectric generator, which delivers the electric energy. Tirtt et al [13] reported that the infrared (IR) region of the solar spectrum can supply the needed hot temperature, T H . With regard to solar energy conversion, thermoelectric devices will likely utilize the IR spectrum of solar radiation as shown in Figure 2.…”