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Scientists Develop Micro Heat Engine That Challenges the Carnot Limit

2 points by westurner 3y ago

westurner 3y ago
"Overcoming power-efficiency tradeoff in a micro heat engine by engineered system-bath interactions" (2023) https://www.nature.com/articles/s41467-023-42350-y https://www.nature.com/articles/s41467-023-42350-y : > Abstract: All real heat engines, be it conventional macro engines or colloidal and atomic micro engines, inevitably tradeoff efficiency in their pursuit to maximize power. This basic postulate of finite-time thermodynamics has been the bane of all engine design for over two centuries and all optimal protocols implemented hitherto could at best minimize only the loss in the efficiency. The absence of a protocol that allows engines to overcome this limitation has prompted theoretical studies to suggest universality of the postulate in both passive and active engines. Here, we experimentally overcome the power-efficiency tradeoff in a colloidal Stirling engine by selectively reducing relaxation times over only the isochoric processes using system bath interactions generated by electrophoretic noise. Our approach opens a window of cycle times where the tradeoff is reversed and enables the engine to surpass even their quasistatic efficiency. Our strategies finally cut loose engine design from fundamental restrictions and pave way for the development of more efficient and powerful engines and devices.
westurner 3y ago
Electrophoresis > Theory: https://en.wikipedia.org/wiki/Electrophoresis#Theory https://en.wikipedia.org/wiki/Electrophoresis#Theory Quasistatic process: https://en.wikipedia.org/wiki/Quasistatic_process https://en.wikipedia.org/wiki/Quasistatic_process : > In thermodynamics, a quasi-static process (also known as a quasi-equilibrium process. Latin quasi, meaning ‘as if’ [1]), is a thermodynamic process that happens slowly enough for the system to remain in internal physical (but not necessarily chemical) thermodynamic equilibrium. An example of this is quasi-static expansion of a mixture of hydrogen and oxygen gas, where the volume of the system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process.[2] Such an idealized process is a succession of physical equilibrium states, characterized by infinite slowness. [3] > Only in a quasi-static thermodynamic process we can exactly define intensive quantities (such as pressure, temperature, specific volume, specific entropy) of the system at every instant during the whole process; otherwise, since no internal equilibrium is established, different parts of the system would have different values of these quantities, so a single value per quantity may not be sufficient to represent the whole system. In other words, when an equation for a change in a state function contains P or T, it implies a quasi-static process.
gus_massa 3y ago
The title is misleading: > Practical heat engines are constrained by a theoretical limit to their efficiency, known as the Carnot limit, which sets a cap on how much heat can be converted to useful work. > Under these conditions, they found that the waste heat dissipated drastically reduced, bringing the efficiency close to 95% of the limit specified by Carnot. So, there is no new physics here.

2 points by westurner 3y ago

"Overcoming power-efficiency tradeoff in a micro heat engine by engineered system-bath interactions" (2023) https://www.nature.com/articles/s41467-023-42350-y https://www.nature.com/articles/s41467-023-42350-y : > Abstract: All real heat engines, be it conventional macro engines or colloidal and atomic micro engines, inevitably tradeoff efficiency in their pursuit to maximize power. This basic postulate of finite-time thermodynamics has been the bane of all engine design for over two centuries and all optimal protocols implemented hitherto could at best minimize only the loss in the efficiency. The absence of a protocol that allows engines to overcome this limitation has prompted theoretical studies to suggest universality of the postulate in both passive and active engines. Here, we experimentally overcome the power-efficiency tradeoff in a colloidal Stirling engine by selectively reducing relaxation times over only the isochoric processes using system bath interactions generated by electrophoretic noise. Our approach opens a window of cycle times where the tradeoff is reversed and enables the engine to surpass even their quasistatic efficiency. Our strategies finally cut loose engine design from fundamental restrictions and pave way for the development of more efficient and powerful engines and devices.

westurner 3y ago

Electrophoresis > Theory: https://en.wikipedia.org/wiki/Electrophoresis#Theory https://en.wikipedia.org/wiki/Electrophoresis#Theory Quasistatic process: https://en.wikipedia.org/wiki/Quasistatic_process https://en.wikipedia.org/wiki/Quasistatic_process : > In thermodynamics, a quasi-static process (also known as a quasi-equilibrium process. Latin quasi, meaning ‘as if’ [1]), is a thermodynamic process that happens slowly enough for the system to remain in internal physical (but not necessarily chemical) thermodynamic equilibrium. An example of this is quasi-static expansion of a mixture of hydrogen and oxygen gas, where the volume of the system changes so slowly that the pressure remains uniform throughout the system at each instant of time during the process.[2] Such an idealized process is a succession of physical equilibrium states, characterized by infinite slowness. [3] > Only in a quasi-static thermodynamic process we can exactly define intensive quantities (such as pressure, temperature, specific volume, specific entropy) of the system at every instant during the whole process; otherwise, since no internal equilibrium is established, different parts of the system would have different values of these quantities, so a single value per quantity may not be sufficient to represent the whole system. In other words, when an equation for a change in a state function contains P or T, it implies a quasi-static process.

gus_massa 3y ago

The title is misleading: > Practical heat engines are constrained by a theoretical limit to their efficiency, known as the Carnot limit, which sets a cap on how much heat can be converted to useful work. > Under these conditions, they found that the waste heat dissipated drastically reduced, bringing the efficiency close to 95% of the limit specified by Carnot. So, there is no new physics here.