Thermowave power using graphene or carbon nanotubes could enable pulsed power from liquid fuel without emissions

Scientists from MIT say they’ve figured out the underlying physics of a new type of energy generation which could one day make it possible to generate electricity directly from liquid fuels using a process called a Thermopower Wave.

There’s no heavy pollution, no noisy engine, and intermediary energy state, although the technology is still very much in the experimental stage.

Eventually, it is hoped that nanowire thermowave generators could be built with thousands of nanowires joined together to continually generate pulses of energy from liquid fuels, using conventional electrical circuits to smooth out the power and use it to drive a electrical gadgets, devices and even electric cars

In the case of a transportation fuel, refuelling would take place in a similar way to a gasoline vehicle — but without the harmful emissions associated with internal combustion engines, while increased energy density would make it possible to have a far greater range vehicle than with current battery technologies.

Nextbigfuture first covered Thermopower wave in 2010.

They have improved efficiency by 10,000 times since 2010 but are still only at 0.1% efficiency. They need to get to 20% efficiency or so to have significant impact and past 50% or so to beat regular current engines (25-60%).

Strano says they could be useful in some niche applications, where a sudden burst of power is needed. And Strano says that the further improvements in efficiency mean broader applications could soon be feasible.

ACS Nano – Excess Thermopower and the Theory of Thermopower Waves

Since the nanogenerator runs on liquid fuels—which store far more energy than batteries—there’s hope that they could allow electric cars to go much farther than they do now.

It’s a setup not unlike the one in an internal combustion engine, in which bursts of fuel are sprayed into combustion chambers to drive pistons. Power electronic circuits could take the bursts of power from several nanotube generators and smooth it out, using it to drive electric motors in a car, for example. The fuel tank could be refilled like one in a conventional car. And because the carbon nanotubes aren’t consumed in the process, they can be used over and over again.

Recently, Strano discovered that switching from nanotubes to flat sheets of nanomaterials—such as single-atom-thick graphene—improves efficiency. Shaping the sheets to direct the energy of the thermopower wave also boosts performance.

Abstract

Self-propagating exothermic chemical reactions can generate electrical pulses when guided along a conductive conduit such as a carbon nanotube. However, these thermopower waves are not described by an existing theory to explain the origin of power generation or why its magnitude exceeds the predictions of the Seebeck effect. In this work, we present a quantitative theory that describes the electrical dynamics of thermopower waves, showing that they produce an excess thermopower additive to the Seebeck prediction. Using synchronized, high-speed thermal, voltage, and wave velocity measurements, we link the additional power to the chemical potential gradient created by chemical reaction (up to 100 mV for picramide and sodium azide on carbon nanotubes). This theory accounts for the waves’ unipolar voltage, their ability to propagate on good thermal conductors, and their high power, which is up to 120% larger than conventional thermopower from a fiber of all-semiconducting SWNTs. These results underscore the potential to exceed conventional figures of merit for thermoelectricity and allow us to bound the maximum power and efficiency attainable for such systems.

Electrical generators using thermopower waves can produce a great deal of power for their size, up to 14 times more than a commercial lithium-ion battery.

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