Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
1999-10-25
2001-05-15
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C136S201000, C136S200000, C310S306000, C438S057000, C438S073000, C438S090000
Reexamination Certificate
active
06232546
ABSTRACT:
FIELD OF INVENTION
This invention relates to a system for maintaining a microcavity over a microscale area. This invention also relates to thermophotovoltaic devices, and more particularly to a microscale thermophotovoltaic generator.
BACKGROUND OF INVENTION
It has been shown that electromagnetic energy transfer between a hot and a cold body is a function of the close spacing of the bodies due to evanescent coupling of near fields. Thus, the closer the bodies, approximately one micron and below, the greater the power transfer. For gap spacings of 0.1 microns, increases in power output of factors often are common.
The dilemma, however, is maintaining the close spacing at a sub-micron gap in order to maintain the enhanced performance.
While it is possible to obtain the sub-micron gap spacing, the thermal effects on the hot and cold surfaces induce cupping, warping or deformation of the elements resulting in variations in gap spacing thereby resulting in uncontrollable variances in the power output.
Typically, in order to increase power output, given the lower power density of prior devices, it has been necessary to increase the temperature. However, the temperature increase is limited by the material of the device.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to provide a microscale generator which provides greater energy transfer in a smaller generator.
It is a further object of this invention to provide such a microscale generator which converts the transferred energy to electricity more efficiently.
It is a further object of this invention to provide such a microscale generator which can generate electricity at lower temperatures.
It is a further object of this invention to provide such a microscale generator which provides consistent power output.
It is a further object of this invention to provide such a microscale generator which can produce an alternating output.
It is a further object of this invention to provide such a microscale generator which does not produce vibrations.
It is a further object of this invention to provide such a microscale generator which has no macroscopic moving parts.
It is a further object of this invention to provide such a microscale generator which can be made variable in size with different applications and power requirements.
It is a further object of this invention to provide such a microscale generator which may be fabricated on a single chip.
It is a further object of this invention to provide a microcavity system for systems other than photovoltaic generators.
The invention results from the realization that a microscale thermophotovoltaic generator may be achieved having two facing elements, one for receiving energy and one for transferring energy, with at least one panel disposed on either or both of the elements, facing the other element, and including a device for controlling the spacing between panel and the facing element to a predetermined, sub-micron gap for increasing the energy transfer to the receiving element. A conversion device, responsive to the increased energy transfer, generates electricity.
The invention further results from the realization that by controllably varying the size of the predetermined gap, an alternating output may be produced.
This invention features a microscale generator having a first element for receiving energy, a second element, opposite the first element, for transferring energy and at least one panel (shown as
18
in
FIGS. 1
,
2
, and
3
) on either of the first element or the second element, the panel facing the other element. There is a device for controlling the distance between the at least one panel and the facing element to form a predetermined, sub-micron gap between the panel and the facing element for increasing the energy transfer to the element for receiving and a converter, responsive to the energy transfer, for generating electricity.
In a preferred embodiment the device for controlling may include an actuating flexure for urging the panel toward the facing element to form the predetermined sub-micron gap, the flexure thermally coupling the panel to the element. The flexure may be disposed below the panel or the flexure may be disposed about the perimeter of the panel or both. There may be at least one spacer disposed on the panel between the panel and the facing element for maintaining the predetermined sub-micron gap between the panel and the facing element. The flexure may include a spring to passively urge the panel towards the facing element to maintain the predetermined sub-micron gap. The flexure may include a piezoelectric actuator responsive to a control circuit which selectively applies a voltage to actuator for controlling the sub-micron gap for urging the panel toward the facing element. The device for controlling may include at least one spacer disposed on the panel between the panel and the facing element for maintaining the predetermined sub-micron gap. The spacer may include a thermally resistant material. The thermally resistant material may include a piezoelectric material. There may be a control circuit for actuating the spacer to maintain the sub-micron gap. The first element may be at a higher temperature than the second element and the panel may be on the first element. The first element may be at a lower temperature than the second element and the panel may be on the first element. The first element and the second element may be at the same temperature.
The invention features a thermophotovoltaic generator having a first element for receiving energy, a second element, opposite the first element, for transferring energy, at least one panel on either of the first element or the second element, the panel facing the element, an actuator for controlling the distance between the at least one panel and the facing element to form a predetermined sub-micron gap between the panel and the facing element for increasing energy transfer to the element for receiving, and a converter, responsive to the energy transfer, for generating electricity.
In the preferred embodiment the actuator may be disposed about the perimeter of the panel, thermally coupling the panel to the first or second element. The actuator may be a spring for urging the panel toward the facing element. The actuator may be a piezoelectric element responsive to a control circuit which selectively applies a voltage to the piezoelectric actuator for controlling the predetermined sub-micron gap. The actuator may be disposed on the panel, between the panel and the facing element, to form at least one spacer for maintaining the sub-micron gap between the panel and the facing element. The actuating spacer may include a piezoelectric element, responsive to a control circuit which selectively applies a voltage to the spacer to control the sub-micron gap.
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Raynolds, J.E., Enhanced electro-magnetic energy transfer between a hot and cold body at close spacing due to evanescent fields, 1999, AIP Conference Proceedings 460, Thermophotovoltaic Generation of Electricity, Fourth NREL Conference, Denver, CO, Oct. 1998, pp. 49-57.
Dalvit, Diego, A.R., and Mazzitelli, Francisco D., Creation of photons in an oscillating cavity with two moving mirrors (Physical Review A, vol. 59, No. 4 (Apr. 1999).
DiMatteo, R.S., Enhanced Semiconductor Carrier Generation Via Microscale Radiative Transfer. . . , Jun. 1996, Thesis, Department of Electrical
DiMatteo Robert Stephen
Kirkos Gregory A.
Weinberg Marc Steven
Diamond Alan
Iandiorio & Teska
The Charles Stark Draper Laboratory Inc.
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