recently published research from the university of manchester (u.k.) discovered that heat engines, devices that turn thermal energy into a form called work that provides power, lose performance at the quantum scale because of the way in which the devices exchange energy with external heat reservoirs.
u.k. researchers have explored the impact of quantum scale on heat engines. (wikimedia commons)
according to a report on the university website, the researchers were examining how heat engines would work in the quantum scale, where the classical laws of physics do not always apply, to explore the possibility of heat engines being used to power quantum computers in the future.
as explained by dr. ahsan nazir in the article, “consensus on how to approach thermodynamics in this so-called strong coupling regime has not yet been reached. so we proposed a formalism suited to the study of a quantum heat engine in the regime of non-vanishing interaction strength and apply it to the case of a four stroke otto cycle.
“this approach permitted us to conduct a complete thermodynamic analysis of the energy exchanges around the cycle for all coupling strengths. we find that the engine’s performance diminishes as the interaction strength becomes more appreciable, and thus non-vanishing system-reservoir interaction strengths constitute an important consideration in the operation of quantum mechanical heat engines.”
the work was recently published in physical review e. the abstract stated:
“we study a quantum heat engine at strong coupling between the system and the thermal reservoirs. exploiting a collective coordinate mapping, we incorporate system-reservoir correlations into a consistent thermodynamic analysis, thus circumventing the usual restriction to weak coupling and vanishing correlations.
“we apply our formalism to the example of a quantum otto cycle, demonstrating that the performance of the engine is diminished in the strong coupling regime with respect to its weakly coupled counterpart, producing a reduced net work output and operating at a lower energy conversion efficiency. we identify costs imposed by sudden decoupling of the system and reservoirs around the cycle as being primarily responsible for the diminished performance, and we define an alternative operational procedure which can partially recover the work output and efficiency.
“more generally, the collective coordinate mapping holds considerable promise for wider studies of thermodynamic systems beyond weak reservoir coupling.”
|