High Frequency MIM diodes for thermal radiation harvesting (original) (raw)
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Applicability of Metal/Insulator/Metal (MIM) Diodes to Solar Rectennas
IEEE Journal of Photovoltaics, 2011
The current-voltage (I-V) characteristics of metal/insulator/metal (MIM) diodes illuminated at optical frequencies are modeled using a semiclassical approach that accounts for the photon energy of the radiation. Instead of classical small-signal rectification, in which a continuous span of the dc I-V curve is sampled during rectification, at optical frequencies, the radiation samples the dc I-V curve at discrete voltage steps separated by the photon energy (divided by the electronic charge). As a result, the diode resistance and responsivity differ from their classical values. At optical frequencies, a diode with even a moderate forward-to-reverse current asymmetry exhibits high quantum efficiency. An analysis is carried out to determine the requirements imposed by the operating frequency on the circuit parameters of antenna-coupled diode rectifiers, which are also called rectennas. Diodes with low resistance and capacitance are required for the RC time constant of the rectenna to be smaller than the reciprocal of the operating frequency and to couple energy efficiently from the antenna. Existing MIM diodes do not meet the requirements to operate efficiently at visible-to-near-infrared wavelengths.
Temperature Analysis of Schottky Diodes Rectifiers for Low-Power RF Energy Harvesting Applications
IEEE Access
This article aims to contribute for the improvement of low-power Radio Frequency Energy Harvesting (RFEH) designs based on Schottky Barrier Diode (SBD) rectifiers, presenting a study of the relationship between RF-DC Power Conversion Efficiency (PCE) and circuit temperature, which is directly related to the non-linear behavior of the metal-semiconductor junction of SBDs. For this purpose, SPICE diode models were revisited, evaluating the temperature dependence and its effects on forward and reverse conduction modes. The SBDs SMS7621 and SMS7630 temperature dependent characteristics are evaluated according the proposal, and their use is explored through analytical modeling and simulation analyzes of an RFEH system for temperatures ranging from 240 to 360 K. Hence, after an initial formulation of the optimum operation in terms of PCE, two series RF rectifiers are designed based on the mentioned diodes, aiming at an efficient operation over different temperature ranges according to each component optimum PCE, at 300 K for the SMS7630 and over 340 K for the SMS7621. For the SMS7630 prototype, the maximum measured PCE is 25.33% around 293 K, but decreases to 3.65% around 353 K, and for the SMS7621 the measured PCE goes from 11.56% to 16.34% in the same temperature range, considering-20 dBm as Input Power (P in) due to the low-power RFEH premise. The results leads to a higher PCE stability for the SMS7621 through the whole analyzed range, despite the overall PCE that is limited by the matching network losses intrinsic to the design.
Thermal Energy Harvesting for Application at MEMS Scale
SpringerBriefs in Electrical and Computer Engineering, 2014
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Development of MEMS based pyroelectric thermal energy harvesters
Proceedings of …, 2011
The efficient conversion of waste thermal energy into electrical energy is of considerable interest due to the huge sources of low-grade thermal energy available in technologically advanced societies. Our group at the Oak Ridge National Laboratory (ORNL) is developing a new type of high efficiency thermal waste heat energy converter that can be used to actively cool electronic devices, concentrated photovoltaic solar cells, computers and large waste heat producing systems, while generating electricity that can be used to power remote monitoring sensor systems, or recycled to provide electrical power. The energy harvester is a temperature cycled pyroelectric thermal-to-electrical energy harvester that can be used to generate electrical energy from thermal waste streams with temperature gradients of only a few degrees. The approach uses a resonantly driven pyroelectric capacitive bimorph cantilever structure that potentially has energy conversion efficiencies several times those of any previously demonstrated pyroelectric or thermoelectric thermal energy harvesters. The goals of this effort are to demonstrate the feasibility of fabricating high conversion efficiency MEMS based pyroelectric energy converters that can be fabricated into scalable arrays using well known microscale fabrication techniques and materials. These fabrication efforts are supported by detailed modeling studies of the pyroelectric energy converter structures to demonstrate the energy conversion efficiencies and electrical energy generation capabilities of these energy converters. This paper reports on the modeling, fabrication and testing of test structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermalto-electrical energy harvesters.
Development of MEMS based pyroelectric thermal energy harvesters
Energy Harvesting and Storage: Materials, Devices, and Applications II, 2011
The efficient conversion of waste thermal energy into electrical energy is of considerable interest due to the huge sources of low-grade thermal energy available in technologically advanced societies. Our group at the Oak Ridge National Laboratory (ORNL) is developing a new type of high efficiency thermal waste heat energy converter that can be used to actively cool electronic devices, concentrated photovoltaic solar cells, computers and large waste heat producing systems, while generating electricity that can be used to power remote monitoring sensor systems, or recycled to provide electrical power. The energy harvester is a temperature cycled pyroelectric thermal-to-electrical energy harvester that can be used to generate electrical energy from thermal waste streams with temperature gradients of only a few degrees. The approach uses a resonantly driven pyroelectric capacitive bimorph cantilever structure that potentially has energy conversion efficiencies several times those of any previously demonstrated pyroelectric or thermoelectric thermal energy harvesters. The goals of this effort are to demonstrate the feasibility of fabricating high conversion efficiency MEMS based pyroelectric energy converters that can be fabricated into scalable arrays using well known microscale fabrication techniques and materials. These fabrication efforts are supported by detailed modeling studies of the pyroelectric energy converter structures to demonstrate the energy conversion efficiencies and electrical energy generation capabilities of these energy converters. This paper reports on the modeling, fabrication and testing of test structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermalto-electrical energy harvesters.
Energy Harvesting and Storage: Materials, Devices, and Applications III, 2012
Harvesting electrical energy from thermal energy sources using pyroelectric conversion techniques has been under investigation for over 50 years, but it has not received the attention that thermoelectric energy harvesting techniques have during this time period. This lack of interest stems from early studies which found that the energy conversion efficiencies achievable using pyroelectric materials were several times less than those potentially achievable with thermoelectrics. More recent modeling and experimental studies have shown that pyroelectric techniques can be cost competitive with thermoelectrics and, using new temperature cycling techniques, has the potential to be several times as efficient as thermoelectrics under comparable operating conditions. This paper will review the recent history in this field and describe the techniques that are being developed to increase the opportunities for pyroelectric energy harvesting. The development of a new thermal energy harvester concept, based on temperature cycled pyroelectric thermal-to-electrical energy conversion, are also outlined. The approach uses a resonantly driven, pyroelectric capacitive bimorph cantilever structure that can be used to rapidly cycle the temperature in the energy harvester. The device has been modeled using a finite element multi-physics based method, where the effect of the structure material properties and system parameters on the frequency and magnitude of temperature cycling, and the efficiency of energy recycling using the proposed structure, have been modeled. Results show that thermal contact conductance and heat source temperature differences play key roles in dominating the cantilever resonant frequency and efficiency of the energy conversion technique. This paper outlines the modeling, fabrication and testing of cantilever and pyroelectric structures and single element devices that demonstrate the potential of this technology for the development of high efficiency thermal-toelectrical energy conversion devices.
Frequency-selective surface coupled metal-oxide-metal diodes
Infrared Technology and Applications XXXIX, 2013
Metal-Oxide-Metal diodes offer the possibility of directly rectifying infrared radiation. To be effective for sensing or energy harvesting they must be coupled to an antenna which produces intense fields at the diode. While antennas significantly increase the effective capture area of the MOM diode, it is still limited and maximizing the captured energy is still a challenging goal. In this work we investigate integrating MOM diodes with a slot antenna Frequency Selective Surface (FSS). This maximizes the electromagnetic capture area while minimizing the transmission line length which helps reduce losses because metal losses are much lower at DC than at infrared frequencies. Our design takes advantage of a single self-aligned patterning step using shadow evaporation. The structure is optimized at 10.6 µm to have less than 2% reflection (polarization sensitive) and simulations predict that 70% of the incident energy is dissipated into the oxide layer. Initial experimental results fabricated with e-beam lithography are presented and the diode coupled FSS is shown to produce a polarization sensitive unbiased DC short circuit current. This work is promising for both infrared sensing and imaging as well as direct conversion of thermal energy.