Traditional fossil fuel power generation process typically has low efficiency. Large amount of the energy loss in Rankine cycle steam turbines (ST) is due to the temperature difference between the combustion flame temperature ∼2250 K (adiabatic) and the high pressure steam temperature up to 900 K. This paper investigates the potential of harvesting this energy to produce additional electrical power using solid-state thermoelectric (TE) power generators placed into the gap between the flame temperature and the steam temperature. Three dimensional (3D) numerical model of a simplified TE module is developed. Different dimensions of fin added to the TE module were investigated to maximize the additional electrical power generation without sacrificing the boiler efficiency.

Near-field thermophotovoltaic (NFTPV) devices have received much attention lately as attractive energy harvesting systems, whereby a heated thermal emitter exchanges super-Planckian near-field radiation with a photovoltaic (PV) cell to generate electricity. This work describes the use of a grating structure to enhance the power throughput of NFTPV devices, while increasing thermal efficiency by ensuring that a large portion of the radiation entering the PV cell is above the bandgap. The device is modeled as a one-dimensional high-temperature tungsten grating on a tungsten substrate that radiates photons to a room-temperature In 0.18 Ga 0.82 Sb PV cell through a vacuum gap of several tens of nanometers. Scattering theory is used along with the rigorous coupled-wave analysis to calculate the radiation exchange between the grating emitter and the PV cell. A parametric study is performed by varying the grating depth, period, and ridge width in the range that can be fabricated using available fabrication technologies. By optimizing the grating parameters, it is found that the power output can be improved by 40% while increasing the energy efficiency by 6% as compared with the case of a flat tungsten emitter. Reasons for the enhancement are investigated and found to be due to the surface plasmon polariton resonance, which shifts towards lower frequencies. This work shows a possible way of improving NFTPV and sheds light on how grating structures interact with thermal radiation at the nanoscale.

Thermoelectrics have the potential to become an alternative power source for distributed electrical generation as they could provide co-generation anywhere thermal gradients exist. More recent material and manufacturing advances have further suggested that thermoelectrics could independently generate primary power [1]. However, due to cost, manufacturability, abundance, and material performance, the full potential of thermoelectrics has yet to be realized. In the last decade, thermoelectric material improvements have largely been realized by diminishing thermal conductivities via nanostructuring without sacrificing performance in electrical transport [2]. An alternative approach is to decouple and optimize the electrical conductivity and thermopower using the unique properties of organic-inorganic interfaces [3]. One method to do this could leverage the electrical properties of a conducting polymer in combination with the thermoelectric proprieties of an inorganic semiconductor in such a way that the interaction between these materials breaks mixture theory. Furthermore, it is expected that the thermal conductivity of this hybrid material would be low due to the inherent vibration mode mismatch between polymers and inorganics. Previously, we have developed a method for producing a solution-processable thermoelectric material suitable for thin film applications using a hybrid polymer-inorganic systems consisting of crystalline tellurium nanowires coated in a thin layer of a conducting polymer (i.e., PEDOT:PSS) [4]. The interfacial properties could be realized in bulk and films demonstrate enhanced transport properties beyond those of either component. More recently, we have been able to significantly improve the thermoelectric properties of these materials by morphological and chemical modifications. Here, we present our methodology and experimental transport properties of this new material where the thermal conductivity, electrical conductivity, and thermopower predictably vary as a function of composition, size, and the structural conformation caused by the solvent. The mechanism for these improvements is currently under investigation, but experimental results suggest that transport is dominated by interfacial phenomena. Furthermore, experiments suggest that both the electrical conductivity and thermopower can be independently increased without appreciably increasing the thermal conductivity. These improvements, in concert with the solution processable nature of this material, make it ideal for new thermoelectric applications.