A Johnson thermoelectric energy converter or JTEC is a type of solid-state

heat engine A heat engine is a system that transfers thermal energy to do mechanical or electrical work. While originally conceived in the context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, pa ...

that uses the

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typi ...

oxidation and reduction of hydrogen in a two-cell, thermal cycle that approximates the Ericsson cycle. It is under investigation as a viable alternative to conventional thermoelectric conversion. Lonnie Johnson invented it and claims the converter exhibits an

energy conversion efficiency Energy conversion efficiency (''η'') is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The input, as well as the useful output may be chemical, electric power, mechanical work, light (radi ...

of as much as 60%, however, this claim is at a theoretical level based on comparison with a

Carnot cycle A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Nicolas Léonard Sadi Carnot, Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem (thermodynamics), Carnot's theorem, it provides ...

and assumes a temperature gradient of 600 °C. It was originally proposed for funding to the

Office of Naval Research The Office of Naval Research (ONR) is an organization within the United States Department of the Navy responsible for the science and technology programs of the U.S. Navy and Marine Corps. Established by Congress in 1946, its mission is to plan ...

but was refused. Johnson obtained later funding by framing the engine as a hydrogen fuel cell. Johnson had been collaborating with PARC on development of the engine.

Mechanism of action

The JTEC is a form of

that converts thermal energy into electrical energy by compressing and expanding hydrogen gas. It operates as a closed system with no moving classical mechanical parts, requires no input of fuel, and creates no exhaust. The engine consists of two stages: A low-temperature compression stage and a high-temperature power stage. Each stage consists of a working fluid chamber that a copper lined

membrane electrode assembly A membrane electrode assembly (MEA) is an assembled stack of proton-exchange membranes (PEM) or alkali anion exchange membrane (AAEM), catalyst and flat plate electrode used in fuel cells and polymer electrolyte membrane electrolysis, electrolyzers ...

(MEA) bisects. A MEA is a proprietary ceramic proton exchange membrane (PEM) that is sandwiched between two electrodes. The operation is similar to an alkali-metal thermal to electric converter, using hydrogen as the working fluid rather than the highly-reactive molten alkali metals, which are difficult to work with. In the high-temperature power stage, expanding high pressure hydrogen from the compression stage converts the heat energy into electrical energy via the MEA. As the high-temperature, high pressure hydrogen is forced through the PEM it is

ionized Ionization or ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...

, producing

protons A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' ( elementary charge). Its mass is slightly less than the mass of a neutron and approximately times the mass of an electron (the pro ...

and

electrons The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

. The protons pass through the membrane while the electrodes expel the electrons through a load. After passing through the PEM, the protons recombine with the electrons to produce low pressure hydrogen gas that flows out to the compression stage. From the perspective of the high-temperature stage, the load consists of the external load on the engine and the low-temperature compression stage. In the compression stage, electrical potential is applied across the MEA and forces protons to flow through the PEM to produce high pressure hydrogen. As the hydrogen travels between the stages, it passes through a

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contac ...

that increases efficiency by helping to keep the high-temperature stage hot and the low-temperature stage cool. The amount of energy available to the external load is the difference in electrical potential between that needed to compress hydrogen at low-temperature and that which expanding it at high temperature generates. Unlike other heat pump devices, the JTEC requires an initial input of electrical energy to start the compression stage and initiate the cycle. In principle, the engine can also be operated in reverse to convert electrical energy into a temperature differential, for example in HVAC applications. In one proposed application,

solar irradiance Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ( ...

would heat the power stage, and the compression stage would connect to an ambient temperature

heat sink A heat sink (also commonly spelled heatsink) is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant, where it is thermal management (electronics), ...

Applications

The scalability of the engine leads its developers to claim that its potential applications range from providing power for

microelectromechanical systems MEMS (micro-electromechanical systems) is the technology of microscopic devices incorporating both electronic and moving parts. MEMS are made up of components between 1 and 100 micrometres in size (i.e., 0.001 to 0.1 mm), and MEMS devices ...

(MEMS) to functioning as large-scale

power plant A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an electr ...

s. The converter can use many diverse forms of fuel without the need for fuel-specific customization as seen in internal combustion engines, and can generate power from fuel combustion, solar irradiance, low grade

waste heat Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility ...

from industry, or such other power generation systems as fuel cells, internal combustion engines, or turbines, because it functions as an

external combustion engine An external combustion engine (EC engine) is a Reciprocating engine, reciprocating heat engine where a working fluid, contained internally, is heated by combustion in an external source, through the engine wall or a heat exchanger. The fluid t ...

References

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External links

*Video
Solve for x Moonshots
2014 Energy conversion Thermoelectricity Cooling technology External combustion engines

Mechanism of action

Applications

See also

References

External links