Friday, February 26, 2010

Pyrodielectrophoretic Heat Engine Exploits Tiny Temperature Differences to Create Motion and Electric Power for MEMS Devices

James Scott Hacsi (Pueblo, CO) has invented a pyrodielectrophoretic heat engine and energy conversion method exploiting the pyrodielectrophoretic effect for effectively and efficiently converting thermal energy into work or other useful forms at any physical size or scale, according to U.S. Patent Application 20100011768. The device can power micro and nano sensors and actuators.  It meets a continuing and growing need for micro-power sources that efficiently convert heat energy into more useful forms at very small physical scales

The pyrodielectrophoretic heat engine operates on a novel thermodynamic heat cycle which exploits the pyrodielectrophoretic effect as defined herein for converting heat or thermal energy directly into work or more useful forms even at very small physical scales for the purposes of cooling, pumping, or moving matter, or for making tiny sensors, and for producing electricity more effectively and efficiently. 

The method of energy conversion, as explained, exploits the pyrodielectrophoretic effect and it should then be evident that work can be performed by the pryoelectric dielectric slab as it continuously moves through an electric field. Thermal energy is directly converted to mechanical or kinetic energy. Kinetic energy of the slab can then be converted to electrical energy and the system conversion efficiency and power output will be greater than the amount of electric power that can be generated or converted with direct heat-to-electric energy conversion as is now being done with pyroelectric generators. 

Pyrodielectrophoretic heat engines are capable of converting heat with relatively small variations in temperature directly into mechanical energy or motion. They provide simple heat engines which have relatively high power density, high specific power and high Carnot efficiencies. It provides simple heat engines with few moving parts and which can be produced cost-effectively. The heat engines can be constructed to operate at very small physical scales and are capable of converting low-grade waste heat or solar energy directly into mechanical energy or motion.

The engine can provide means and methods of cooling electronic circuits and components with very small dimensions. It can also provide means and methods for pumping or moving matter very efficiently at small physical scales, and [provide sensitive and tiny sensors requiring very little electrical power for their operation. 

 Pyrodielectrophoretic heat engine exploit the pyrodielectrophoretic effect for converting thermal energy into work or other useful forms. The pyrodielectrophoretic heat engine includes:
(a) movable pyroelectric matter capable of exhibiting a temporary surface electric charge and electric field established or induced when the movable pyroelectric matter is subjected to an addition or removal of heat for causing a change in temperature, and
(b) a heat source or radiation source for causing a change in temperature in movable pyroelectric matter, and
(c) a heat sink for removing heat from or lowering the temperature of said movable pyroelectric matter, and
(d) a fixed electric field established between two oppositely-charged electrical points or surfaces capable of drawing in the movable pyroelectric matter with the temporary surface electric charge and electric field while simultaneously displacing from the fixed electric field other movable pyroelectric matter with no temporary surface electric charge or electric field and which is not experiencing a change in temperature.
(e) means for converting kinetic energy of the movable pyroelectric matter moving through the fixed electric field into work or other useful energy forms.

The movable pyroelectric matter is comprised of nanotubes, nanowires, or any nano-structure capable of experiencing a surface electric charge, electric dipole moment, or electric field when exposed to an addition of heat, electromagnetic energy, or electrically-charged particles for causing a temporary change in temperature in pyroelectric matter. 

Hacsi says the novel pyrodielectrophoretic heat engine with its associated heat cycle exploits the "pyrodielectrophoretic effect", also known as "pyrodielectrophoresis" (or pDEP). The "pyrodielectrophoretic effect" is hereby defined as the tendency of an external electric field to attract and draw in pyroelectric matter with a temporary surface electric charge or electric dipole moment caused by a change in temperature and spontaneous polarization, while simultaneously rejecting or displacing other pyroelectric matter from the same electric field that no longer has a surface electric charge or electric dipole moment and is no longer experiencing a change in temperature.

 In other words, pyroelectric matter acting as the dielectric of a parallel-plate capacitor that is experiencing a change in temperature and with a surface electric charge or electric dipole moment is drawn into the gap between the capacitor's plates, while other sections of the same pyroelectric dielectric matter is displaced from between the parallel, oppositely-charged plates because those sections of pyroelectric dielectric matter are no longer experiencing a change in temperature and no longer have a surface electric charge or no electric dipole moment. The result will then be a continuous motion of pyroelectric dielectric matter through the electric field of the capacitor as appropriate sections of the pyroelectric matter are heated (or cooled) and drawn into the non-uniform electric field or "fringe field" of the capacitor, while other sections of pyroelectric matter are cooled (or heated) until there is no longer a change in temperature in those sections of pyroelectric matter that are already inside the electric field of the capacitor.

The kinetic energy of the moving pyroelectric (dielectric) matter can then be efficiently converted to electrical energy or other useful forms. Notice this procedure is entirely different than heating and cooling a capacitor with its stationary dielectric having temperature-dependent permittivity for the purpose of converting heat directly into electric energy. In this case, the dielectric of the capacitor actually moves while doing work and the plates remain stationary so that the pyroelectric dielectric matter essentially becomes the working substance or "fluid" of the heat cycle. An indirect conversion of heat to mechanical energy and then into electric energy or other useful forms occurs. The permanently-fixed or stationary electric field drawing in and displacing the pyroelectric slab can be established and maintained by a separate voltage or power source, but the electric field can also be induced by being in close physical proximity to the heated or cooled sections of pyroelectric matter that are experiencing a temperature change. 

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