Modeling and optimization of hybrid solar thermoelectric systems with thermosyphons

Abstract

We present the modeling and optimization of a new hybrid solar thermoelectric (HSTE) system which uses a thermosyphon to passively transfer heat to a bottoming cycle for various applications. A parabolic trough mirror concentrates solar energy onto a selective surface coated thermoelectric to produce electrical power. Meanwhile, a thermosyphon adjacent to the back side of the thermoelectric maintains the temperature of the cold junction and carries the remaining thermal energy to a bottoming cycle. Bismuth telluride, lead telluride, and silicon germanium thermoelectrics were studied with copper-water, stainless steel-mercury, and nickel-liquid potassium thermosyphonworking fluid combinations. An energy-based model of the HSTE system with a thermal resistance network was developed to determine overall performance. In addition, the HSTE system efficiency was investigated for temperatures of 300 K -1200 K, solar concentrations of 1 -100 suns, and different thermosyphon and thermoelectric materials with a geometry resembling an evacuated tube solar collector. Optimizations of the HSTE show ideal system efficiencies as high as 52.6% can be achieved at solar concentrations of 100 suns and bottoming cycle temperatures of 776 K. For solar concentrations less than 4 suns, systems with thermosyphon wall thermal conductivities as low as 1.2 W/mK have comparable efficiencies to that of high conductivity material thermosyphons, i.e. copper, which suggests that lower cost materials including glass can be used. This work provides guidelines for the design, as well as the optimization and selection of thermoelectric and thermosyphon components for future high performance HSTE systems.

Modeling and Optimization of Superhydrophobic Condensation

“…Such surfaces may therefore enable (1) substantial reduction in industrial con- denser sizes and cost [51]; (2) overall performance enhancement of devices such as heat pipes and thermal ground planes for applications requiring maximization of evaporator area and minimization of condenser area [56]; and (3) use of cooling devices previously not possible for local high heat flux electronic devices [18,57].…”

Energy supplies and future engines for land, sea, and air

“…There is a considerable advantage in a hybrid system combining solar thermoelectric with heat rejection to a low-temperature (bottoming) cycle (Miljkovic and Wang, 2011). Another hybrid system uses a Fresnel lens to concentrate sunlight onto PV cells on roof panels that also heat water for residential and commercial applications.…”

Envisioning advanced solar electricity generation: Parametric studies of CPV/T systems with spectral filtering and high temperature PV

“…Low temperature PV/T systems have become available and widely studied [9][10][11][12][13][14][15] while CPV/T systems have seen less research due to the competing temperature demands. While CPV/T faces distinct challenges a wide variety of studies have been conducted to examine a variety of effects and applications: spectral filtering [16][17][18][19][20][21][22][23], solar cooling [24,25], fluid placement above or below the PV cell [26], thermoelectric [17,27,28], and cell bandgap and concentration ratio [29,30]. It should be noted that not all of the previous CPV/T work has looked to generate electricity from the thermal component; many are primarily using the thermal system to remove waste heat from the PV cell to improve cell efficiency and then capture medium temperature thermal energy.…”