The Nanoantenna Prospect for Harvesting Energy

1. The Nanoantenna Prospect for Harvesting Energy Steven Novack– Idaho National Laboratory Dale Kotter – Idaho National Laboratory Patrick Pinhero – University of Missouri-Columbia Dennis Slafer – MicroContinuum, Inc. October 2009

2. We believe that future nanoantenna technology can provide a significant contribution to energy production and management reducing the world’s dependency on oil.

3. Tapping the Sun’s Energy ~30% Reflected ~19% Absorbed Atmosphere ~51% Absorbed by Earth Single day provides enough energy for 27 years

4. The Solar Spectrum and Earth

5. Multi-junction PV Design Single Junction PV Example Photovoltaic Technology General efficiency numbers • 5-6% calculators and small devices • 12-18% standard solar panels • 18-20% thin film/PERL/concentrated • 40.7% NREL/Boeing multi-junction (expensive) • Footprint/flexibility • Cost/shortage of processed silicon • Delivers DC power • Requires direct incidence • Availability/annualized efficiency

6. History of Using Antennas for Energy Harvesting Nature’s antenna - Chlorophyll 1964: William Brown’s microwave powered helicopter in flight.

7. Theory of Operation • Light propagates as an electromagnetic wave • Captured by a nanoantenna • Absorption occurs at antenna resonance • Induces a cyclic plasma movement of free electrons • THz current flows toward antenna feedpoint • Diode is embedded in feedpoint to rectify signal

8. 2 Grand Challenges for NanoAntennas • Large-Scale Manufacturing • Layering approach (small prototypes to roll-to-roll manufacturing) • Measuring and modeling of materials at high frequencies • Large-scale templates • Analytical processes for flexible substrates • Exotic materials and waste streams • Methods need to be developed for efficient high-frequency rectification (10 um range ~ 30THz) • Rectenna designs • MIM/MIIM/MIMIM • Secondary harmonics • Manufacturing integration • Materials considerations • Analytical processes

9. NanoAntenna Collector Concepts Antenna Array • Current nanotechnology allows creation of antennas small enough to resonant at near- and mid-IR ranges • INL prototype efficiency for this resonance is approximately 80% modeled up to 92% • Creates AC or convert to DC using Rectennas *Courtesy of University of Central Florida – Glen Boreman

10. Antenna & RLC Dielectric resonance layer Ground plane - reflector Design Overview • Initial design of Nantennna was based on scaling of radio frequency antenna theory • Analytical model – RLC Circuit derived • Nantenna consists of an antenna layer, a dielectric resonance layer, and a optical reflector/ground plane • Physical geometry tunes antenna and spectral response Nantenna Structure

11. Adapting Tools for THz Frequencies • At THz frequencies material properties deviate from classical theory • Measured real & imaginary permittivity from 1-30 microns • Imported into the design codes to accurately model frequency dependent behaviors • Provides visualization of infrared thermal behavior that cannot be directly measured • Supports virtual prototyping of nano-structure devices Variable-angle IR Ellipsometer

12. Validation of Nantenna Concept • A periodic array of loop antennas was designed for resonance at 10um. • PMM emissivity plot was acquired to estimate nantenna efficiencies • A theoretical efficiency of 92% was demonstrated • Independent small scale NiCr antennas validated at 5um ~ 95% efficiencies at 24o off normal Periodic Array of Loop Antennas Nantenna Prototype on Silicon Substrate Emissivity Plot

13. Large-scale Manufacturing Process SEM top view of Si wafer after anisotropic oxide etch SEM cross-section of patterned oxide layer of (prior to DRIE step)

14. Large-scale Manufacturing Process SEM image of polymer replicas made from wafer master template Flexible Structures

15. Large-scale Manufacturing Process • First known large-scale development of nano-structures on PE flexible substrate • 2 Nano 50 Technology Awards 2007 • Scalable to a roll-to-roll process • Imprint nanoantenna structures into flexible substrate • Manufacturing Cost:~ $0.50-1.00/ft2 (for antenna portion only) Roll to Roll Manufacturing Equipment Replica tool – Master Template Replication - Imprinted into 0.35 mil PE

16. Energy Conversion Research • Consumer components not available for diode rectification at thermal wavelengths • Exploratory research of THz diodes underway • T-gate schottky diodes • Metal-insulator-metal tunnel diode • Point contact diodes • Ballistic rectifiers • Monolithic integration of diode onto NEC substrate T-gate Schottky Diode Proof of concept at T-Ray using spiral antenna w/ tunnel diodes MIIM Diode by Phiar Corp Ballistic Rectifier *Aimin Song, University of Manchester, UK

17. Benefits and Applications • Addresses many limitations of PVs • Utilize untapped infrared parts of spectrum • Can be inexpensively mass produced • Many Diverse Applications: • Nanoantenna “skins” • Can be ‘tuned’ to concurrently harvest multiple energy sources • Economically scales to large infrastructure (homes, businesses) • Requires technology advances in THz electronics. Projected 3-5 years R&D cycle.

18. Questions/Comments? Technical Paper available at : http://www.inl.gov/technicalpublications/Documents/3992778.pdf Look for our Journal Article Theory and Manufacturing Processes of Solar NanoAntenna Electromagnetic Collectorsin the Journal of Solar Energy and Engineering Steven.novack@inl.gov