Concept: Infared Rectennas For Energy Harvesting

Text Box:    Illustration of combined solar panel-rectenna-battery structure for wideband energy harvesting and storage  Text Box:    Schematic of the rectenna circuit that will be used for detailed power and efficiency analysis.          Text Box:    Equilibrium energy band diagram for the symmetrical (LEFT) and asymmetrical (RIGHT) M-I-M structure.  We propose to help solve the energy crisis by directly harvesting energy from infrared radiation sources through the use of micro-antennas coupled to rectifying diodes and storage capacitors. The general concept is to combine antennas with rectifiers to form an array consisting of millions of micron-size rectennas. An example rectenna for solar energy harvesting consists of a dipole-type antenna with the two sides of the dipole connected by a rectifier. The antenna receives the infrared electromagnetic radiation, and the rectifier converts it to direct current which can then be stored or used for satisfying electrical energy needs.

The overall goal at the end of this three phase program is to develop an energy collector composed of rectenna arrays that are connected in parallel that harness significant amounts of infrared electromagnetic energy. The ultimate systems will be capable of harvesting watts, kilowatts and perhaps even megawatts of energy using these structures fabricated in parallel on a large scale. In phase 1 we will model and design the array and fabricate scaled prototypes. We will also improve our fabrication process and begin building micro-scale antennas. In phase 2 we will fabricate micro-antenna arrays along with their rectifying diodes and prototype simple arrays of infrared rectenna pixels. We will continue to improve the design through modeling and testing. In phase 3 we will finalize initial design and focus on manufacturing the energy harvesters for military and commercial implementation. In this particular effort we will focus more on infrared, however, many of the techniques developed will be applicable to visible wavelengths as well.

Objectives Summary:

CAD tools for design, analysis and optimization of individual rectenna elements including the micro-antenna, rectifying element (MIM diode), and the energy harvesting circuit will be developed as part of phase 1. The tools will include two-dimensional distributed Poisson and Schrodinger equation solvers for the MIM diode, Maxwell equation based EM tools for antenna analysis, Verilog-A based compact models for rectenna nodes, and circuit simulation and analysis metrics for performance evaluation of the complete energy harvester circuit.

The Micro-antenna is an electromagnetic style antenna that will be designed to pick up infrared radiation frequencies. The antenna needs to be sufficiently broadband so it is responsive to a large range of frequencies in the infrared region for maximum energy scavenging. Its design must also be optimized for efficient micro-fabrication. It must be low-loss and be able to transform induced current into high enough voltages to turn on the rectifying diode.

The Rectifier is a special diode that will be able to pass current generated in the antenna in only one direction. The diode will have to respond fast enough to operate at optical frequencies, and have relatively low turn on voltage. It will also require sufficiently small capacitance as to minimize its time constant.

The Focal Plane Array will be the arrangement of interconnected rectennas so that they are able to transfer the collected DC electrical energy to storage capacitors and batteries. Layout of the array must be performed very carefully so that the interconnects either improve or minimally affect energy collection. We will develop modeling tools to optimize the layout and design of this focal plane array.

Source:  http://www.coolcadelectronics.com/DARPA_Energy_Harvesting.html

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