Skutterudites, and this new knowledge about how best to arrange their atoms, could help improve their performance to 15- or 20-percent, at which point they become useful in many practical applications, said Massoud Kaviany, professor in the Department of Mechanical Engineering.
What does "%age efficiency" mean in the context of "heat-to-electricity-conversion"?
If you have a device attached to a 10kg block of metal that is 10C above ambient and, let's say, has 5kJ of thermal energy above ambient, does a 10% efficient device mean it can suck off 500J? Can that test happen over a whole day? Or would a device that can suck 500 MW of heat energy out of that block in a microsecond still only be "10%" efficient?
Or is it based on a source of heat that is maintained temperature stable (viz. an 'infinite' amount of heat over ambient) so what could 10% efficiency mean then?
I do dislike this wooliness. I wish articles can properly cover the meanings of the technical terms they use so it doesn't render the whole meaningless.
It might even mean that if they pump the device with 100W then they can convert 10W of thermal work from the block back into energy. Who knows? Could mean anything!
Thermoelectric conversion can be defined in a quick and dirty way the amount of radiative energy we remove from a body under the form of electricity, so the Stefan–Boltzmann law will give you a rough idea.
In general the source heat is considered stable and efficiency is considered at steady state, not impulse.
If you like to get more out of the argument just search on arxiv for "thermoelectric" or "thermoelectric skutterudites". Lot of experimental setup in thosse papers to clarify all your doubts.
I think you could compare present thermoelectric generators to possible future models. The RTGs presently used on outer-solar-system craft such as Cassini are typically under 1 kW. Electric propulsion systems like DS-1 require around 2.5 kW, and they run them on solar panels, which out-perform RTGs out to around the orbit of Mars.
This would put RTGs up to power levels where they could do low-end ion propulsion duties. This presumes a radioactive heat source won't destroy these materials, but that's probably managable if the energy is from easily-shielded alphas and betas.
This is not a profound revolution, but it would drive a shift in the economics of waste heat recovery, making it possible to use simple equipment to get some useful power out where the existing technology makes it a fool's errand to try.
Thermoelectrics are tedious to re-explain every time
How do you suggest I rewrite it ?
The conversion efficiency changes with ZT (figure of merit) and temperature difference.
I included the chart of ZT and temperature differential to get percentage of efficiency.
I explained that the researchers are claiming that their barium alloys can get ZT into the 2 range up from current lab work in the 1.4 range and commercially at the 1.0 range.
BTW- do you think an interested reader would find your sentence to be more clear and well written ?
[quote]
"Thermoelectric conversion can be defined in a quick and dirty way the amount of radiative energy we remove from a body under the form of electricity, so the Stefan–Boltzmann law will give you a rough idea. "[/quote][/quote]
Sorry, nextbigfuture, I come across much harsher than I mean to most times. I think the bit I was missing was comprehending the principal significance of the 'ZT' bit, rather than the header and opening para focussing on a discussion of the '%age efficiency'. That makes more sense [to me!] now it is clear that the efficiency is a consequent function of this ZT value and, I presume, probably therefore infers that efficiency represents the %age total heat flux through the device that is converted to electrical power (rather than anything to do with temperature, per se). Is that right?
I do find your way of taking different sources and packing the essential information into a single story extremely well done and I do not think you should change the way you are doing it.
I also do not think that using my description of thermoelectric would make any difference. An interested reader will anyhow research for extra sources or ask clarifications. As you said, thermoelectric is not something easy to explain.