腾讯电竞

More efficient conversion of heat into electricity by tinkering with nanostructure

(Nanowerk News) Thermoelectric materials convert heat into electricity, which makes them extremely attractive for sustainable energy production, especially given that industry can waste more than two-thirds of its energy as heat. But mass-production of thermoelectric energy is currently limited by low energy conversion efficiency.
Now however, researchers Biswanath Dutta and Poulumi Dey of TU Delft抯 department of Materials Science and Engineering, have not only been able to explain how nano-structures in thermoelectric materials can improve energy efficiency but they also propose a commercially more attractive way to manufacture nano-structured thermoelectric materials, increasing the chances for mass-production of thermoelectric energy.
Their results were published in Nano Energy ().
The starting point for Dutta and Dey抯 work was the experimental results provided by their co-researchers in South Korea who were working with a well-known thermoelectric material, a so-called NbCoSn half-Heusler compound.
揟his is basically a specific type of crystal structure into which you put certain elements - in this case niobium, cobalt and tin,?explains Dutta. 揂nd by playing around with both the amount and the position of each of the elements - for example putting more niobium in place of cobalt ?you can see how that affects the overall efficiency of the material.?
What the results from their South Korean collaborators showed was that at a specific temperature, certain kinds of nano-structures were formed within this material. So Dutta and Dey ran theoretical simulations based on these observations: 揊irstly we simulated the effect of adding either one or two extra cobalt atoms, and in various different positions, to find out whether that would increase the efficiency or not,?says Dey. 揑t turned out that the position of this extra cobalt really has an important role on the whole performance of this material, which was something that the team doing the experiments couldn抰 really explain because it was beyond the resolution of their measurements.?
conversion of heat into electricity
In addition, Dutta and Dey were also able to demonstrate an effect known as 慹nergy-filtering? 揧ou can think of it as a sort of barrier to electrons below a certain energy, which in turn improves overall electrical conductivity,?explains Dutta. 揃y filtering out the low-energy electrons and allowing the high-energy electrons to pass through, there is an increase in the overall efficiency.?
揥hich is a nanostructure effect,?continues Dey. 揑t抯 the formation of the nanostructures in the rest of the material, and the interface between them, that acts as the barrier so if you don抰 have these nanostructures, you won抰 have this effect because there抯 no interface. But as soon as these nanostructures are formed, you get these interfaces which block the low energy electrons but allow the high energy ones to pass through with the result that the overall energy efficiency is increased.?
Ultimately the TU Delft simulations suggested two reasons for increased energy efficiency in this tailored NbCoSn thermoelectric material: namely the presence of extra cobalt atoms in specific positions called Interstitial sites within the lattice structure, and also the energy-filtering effect.
Moreover, this better understanding of why this nano-structured thermoelectric material is more energy-efficient suggests a better, more applicable way to produce, even mass-produce, thermoelectric energy.
揅urrently nano-structured thermoelectric materials are made through a long and rigorous process of crushing and heating pre-formed structures,?explains Dutta 搘hich is both time and energy-consuming so not ideal for mass production.?
So rather than going down the conventional route, the teams suggested starting with an 搖nstructured?or amorphous material: 揟he advantage of starting with an amorphous material is that it doesn抰 have an underlying structure and so you don抰 need to go through this long process of grinding and heating for homogenisation. So it抯 more energy efficient and therefore much more useful for mass production of thermoelectric energy.?
Good news for all those industries working on recovery of high temperature heat.
Source: TU Delft
Share this:
Subscribe to a free copy of one of our daily
Nanowerk Newsletter Email Digests
with a compilation of all of the day's news.
 
These articles might interest you as well: