I amnot so sure that this is a particularly new idea so much as anengineering impossibility. Whether or not that has changed remainsto now be seen. It would be really nice to draw off surplus heat asas direct electrical power as a matter of simple best practice. Wemight even get good at it. I suspect that it remains a dauntingproblem but possibly one that now may attract research funds.
Directthermal conversion into electrical potential has never got muchattention mostly as no one had any good answers. Yet we live in an oceanof such potential and even a small conversion would be beneficial. Our dance with the laws of physics does suggest that we can masterthis ocean.
Applyinga magnetic field has been obvious and literally the first thing thatones thinks to try. At least we can now presume it works well enoughin an ideal setup in a lab. This then takes us back to engineeringand it is here that modern materials have something to say. No oneis wrapping an electric coil around a cylinder head anytime soon. Neodymium magnets may be another matter.
It iscertainly worth toying with to see if it can go somewhere by an army of researchers.
Breakthrough for superefficient conversion of heat toelectricity could boost coal plant efficiency to 54% from 30-45% andconcentrated solar power to 40%
FEBRUARY 10, 2013
http://nextbigfuture.com/2013/02/breakthrough-for-superefficient.html
Arxiv - Thermionics(electronics for converting heat to electricity) previously hadefficiency limitations due to “space current” – build-ups ofelectrons mutually repelling each other and choking the flow ofcurrent – so the new system uses external electric or magneticfields to get the electrons going in the right direction. The systempromises a high fraction of the Carnot Limit can be converteddirectly into electrical power.
54%Efficient Coal Plants for one third less coal for the same power
The newthermoelectronic approach promises efficiencies in the high 40-50%range, achieving the latter by acting as a “topping cycle” to alower temperature steam system. For example a coal furnace burns at~1500 C (1773 K), but a steam turbine runs at 700 C (973 K) andoutputs at 200 C (473 K). Thus there’s significant loss due to themismatch between furnace and steam power-cycle. A thermoelectronicconverter covering the 1773-973 K range will add significantly to theoverall power extracted by the power-plant pushing its efficiencyabove 50%. In this case a 45% efficient coal plant can be pushed to54%, thus increasing the power output for no additional fuel costsand NO MOVING PARTS.
40% efficient concentrated solar power
Switching tosolar-power applications, imagine a thermoelectronic converter at thecentre of a concentrator system which focuses sunlight to 500 timesits normal intensity (temp ~1900 K.) By using a Photon EnhancedThermionic Emission (a cousin of the Photoelectric effect) the systemcan convert raw sunlight to electrical power at over 40% efficiency
ABSTRACT- Electric power may, in principle, be generated in a highlyefficient manner from heat created by focused solar irradiation,chemical combustion, or nuclear decay by means of thermionic energyconversion. As the conversion efficiency of the thermionic processtends to be degraded by electron space charges, the efficiencies ofthermionic generators have amounted to only a fraction of thosefundamentally possible. We show that this space-charge problem can beresolved by shaping the electric potential distribution of theconverter such that the static electron space-charge clouds aretransformed into an output current. Although the technicaldevelopment of practical generators will require further substantialefforts, we conclude that a highly efficient transformation of heatto electric power may well be achieved.
Optimization of the conversion efficiencies requires the development of metal or semiconductor surfaces with the desired effective work functions and electron afinities, respectively, which may also be done by nanostructuring the electrode surfaces. These surfaces need to be stable at high temperatures in vacuum. The tunability of the gate fi ld opens possibilities to alter the converter parameters during operation. Although the need to generate Cs+ ions to neutralize the space-charge cloud is eliminated, ad atoms of elements such as Cs can be used to lower the work function of the electrodes, in particular of the collector. For high efficiency, the devices must be thermally optimized to minimize heat losses through the wiring. Furthermore, thermal radiation of the emitter must be reflected efficiently onto the electrode. For ballistic electron transport between emitter and collector, a vacuum of better than 0:1 mbar is also required, reminiscent of radio tubes.
Such devicesmay be realized, for example, in a flip-chip arrangement ofoxide-coated wafers separated by tens of micrometers usingthermal-insulation spacers. This produces hundreds of Watts of powerfrom active areas of some 100 cm2. The magnetic fields, typically 1 Twith large tolerances in strength and spatial distribution, can begenerated by permanent magnets or, for applications such as powerplants, by superconducting coils. Achieving viable, highly efficientdevices requires substantial further materials science efforts todevelop the functional, possibly nanostructured materials, as well asengineering efforts to achieve a stable vacuum environment in orderto minimize radiative and conductive heat losses, and to ensurecompetitive costs. Remarkably, however, no obstacles of a fundamentalnature appear to impede highly efficient power generation based onthermoelectronic energy converters.
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