Retail Beamed Power for a Micro Renewable Energy Architecture: Survey

1. Retail Beamed Power for a Micro Renewable Energy Architecture: Survey Retail Beamed Power for a Micro Renewable Energy Architecture: Survey Narayanan Menon Komerath Professor, Daniel Guggenheim School of Aerospace Engineering Georgia Institute of Technology Atlanta, Georgia USA

2. Demand for mobile connectivity and other electric devices far outpaces power grid expansion. • India: 638,000 villages, 80 percent have at least one electric line. • 415 million people have no access to electricity • Over 450 million mobile phone accounts (Multiple accounts per user). • Retail Power Beaming is a viable alternative to constructing wired grids for several future applications, despite low efficiency. • Route for the small electronic devices market to leapfrog the centralized power grid, in many parts of the world.

3. Aerospace Interest: 3-stage Approach to Power Delivery • Tower to village (KW-1MW per tower ) • Regional plant or Space – stratospheric platform – customer (10-100MW per platform) • Space Power Grid – national /global needs (100MW per satellite) Beamed delivery to remote sites and islands is possible from Space / Stratospheric Platforms/ UAVs Retail beaming can close the business case for beamed power, while enabling many communities to leap ahead of terrestrial power grid expansion global Local Surface range to visible horizon, km Regional Relay height AGL, km

4. Antenna Size Dictates Millimeter Wave Regime(GEO receiver size is off the chart) Receiver Diameter, m Frequency, GHz • Frequencies below 100GHz are not viable for delivery from Space, due to costs of space and ground infrastructure. Hence interest in millimeter waves. • Mmwave infrastructure is suitable for retail family / village sized receivers

5. Regional power plant to stratospheric platform (Stratoform) to customer site • Range to 600 km • Power level ~10 to 100 MW • Multiple receivers • “Burnthrough” beam to handle bad weather http://images.gizmag.com/hero/6358_20100630239.jpg http://www2.nict.go.jp/q/q262/3107/end101/ENG/FAQ/FAQ-E1.htm http://images.gizmag.com/hero/6358_20100630239.jpg

6. 1. Expense of solid state arrays vs. PV arrays Issues and solutions

7. Dealing With Low Efficiency • Value of first watt-hour • Opportunity cost of waiting for wired grid

8. Many needs are met by a few watt-hours

9. Baseline economic model for rural BPTS • Wired or Stat-form power delivery to rural station • Beamed “last kilometer” to customer antenna • Synergy with mobile phone and railway infrastructure where possible • Local industry/major users must subsidize costs of reaching small users

10. Potential Near-Term Applications • Broad area low intensity power distribution for emergencies • Deliver to local village grid • Remote military or scientific outposts • High endurance miniature robots • Distributed micro power generation • Remote area exploration • Increased range for electric vehicles • Rapid restructuring of grid topology for damage mitigation

11. Dry Atmospheric Absorption for Vertical Transit Good windows at ~100, 140, 220GHz Need: Narrow-band data to identify best windows near 100 GHz and 220GHz

12. Atmospheric Absorption for Horizontal Propagation (Why go up instead) Line A: Average absorption at sea level, 20C, 1atm, H2O vapor 7.5 g/m3) Line B: Altitude 4 kilometers pressure altitude, (0C, Water Vapor Density= 1 g/m3) http://ops.fhwa.dot.gov/publications/viirpt/sec5.htm

13. Impact of rain and fog: Need “burn-through”. DSP/solid state generation permits use of an initial burn-through frequency followed by main power beam 220GHz 94GHz

14. Technology Opportunities • Integrate mm-wave receivers with solar panels • Narrow-band phase-array receivers for laser and mm-waves, integrated with PV panels • Nanotube broadband direct solar conversion antenna • Burn-through rain, clouds and fog using mmwave and other wavelengths • Lightning analogy: Create conductive path for mm-wave beam using “seed” beam • Use waste heat on relay platforms to generate burn-through beam • Co-use communications and power transfer control equipment • Improve conversion efficiency to & from 200-220 GHz • Satellite waveguides • Thermal management • Effects of scattered 220Ghz radiation on humans/animals

15. Conclusions • Rising demand for connectivity and personal electronics, creates an opportunity to leap-frog grid expansion using retail power beaming. • Millimeter wave beaming brings antenna sizes practical for retail installation. • Enables retail power distribution to off-grid locations and islands. • Closes the business case for distribution through Space and statospheric platforms. • Enables synergy with distributed micro renewable power architectures. • Value of first few watts and watt-hours >> marginal cost of utility power. • Synergy with photovoltaic arrays multiplies cost-effectiveness of micro power architectures • Optimal frequencies for moist atmospheres differ from those for long-distance dry air and vacuum beaming. • Solid-state arrays enable several beam frequencies from the same arrays in order to serve multiple purposes. • Indian village electrification offers an opportunity to establish a retail beaming infrastructure. Rural economics model works best with stratospheric platforms, local beamed delivery and subsidized cost to small users. • High-resolution data needed for 100GHz and 220GHz bands • Low efficiency and weather issues are not show-stoppers for retail millimeter wave power beaming.

16. Acknowledgement Support from NASA under the “EXTROVERT” cross-disciplinary learning initiative is gratefully acknowledged.

17. Beamed Retail Power Transmission/ Distribution System • Wireless transmission of power (not just signals with information) over relatively short distances to multiple end-user receivers. • Usually implies focused point-to-point transmission with highly directional antennae, and provisions for energy storage at either end. • Conventional solutions using <10GHz microwave, and some proposed solutions using lasers. • Our interest is in the millimeter wave regime, specifically near 220 GHz Beam Formation Transmission & Reception DC to mm wave conversion mm wave to DC conversion

18. Space Power Grid Concept: 220 GHz 140GHz Propellant Heating Beam Being Considered by NASA/USAF

19. Use space-based infrastructure to boost terrestrial “green” energy production from land and sea: argument for public support. Full Space Solar Power (very large collectors in high orbit) will add gradually to revenue-generating infrastructure. FIGURE 1. Space Power Grid Satellite Receving And Redistributing Beamed Power. 3. Space Power Grid Exploit large geographical, daily and seasonal fluctuations in power cost (Landis 2004, Bekey 1995). Beam to other satellites Retail delivery (SPS2000). Technical risks in dynamic beaming/reception/ transaction system. Inefficient conversion to and from microwave vs. terrestrial high-voltage transmission lines. Team: Brendan Dessanti, Janek Witharana

20. Power delivery to points of local distribution • Low-altitude horizontal beaming is inefficient unless burn-through techniques are perfected. • Use vertical beaming to and from high-altitude platforms wherever possible.

21. The Dream of Energy Independence • Terrestrial solar, wind and biomass power plants • Space-delivered solar power • Beamed power to complement local generation, in off-grid communities • Hydrogen generation using excess / spike power • Stored hydrogen and bio-gas for fuel cells and transportation

22. Burn-through rain, clouds and fog using mmwave and other wavelengths Solid state arrays / DSP-PLL generation approach allows consideration of tuning to narrow bands, and shifting to a pilot beam for a short duration to prepare the path for the main beam • Options to investigate: • Find narrow lines in 220GHz window, where propagation efficiency is higher. • Saturate? No experiments found so far on the effect of sustained beam energy addition on wet air for durations of minutes • 2. Deliberately heat using selected frequencies and create low-density path? • Lightning analogy? Create conductive path for mm-wave beam using “seed” beam

23. Summary Observations -2 • Direct conversion from broad-band solar to beamed mmwave appears feasible. • Integrated antenna / PV generators already in use • Large-scale arrays of solid-state devices with DSP and PLL to generate mmwave • Laser efficiencies may be on cusp of breakthrough but need changes in laws/treaties • Most current “systems analyses” of SSP prospects appear to assume <$400/lb launch costs • to LEO. This is not realistic. Must insist on disciplined costing to see the real technology • opportunities.

24. The Space Power Grid Approach • Use space-based infrastructure to boost terrestrial “green” energy production from land and sea: argument for public support. • Full Space Solar Power (very large collectors in high orbit) will add gradually to revenue-generating infrastructure. • Exploit large geographical, daily and seasonal fluctuations in power cost. • Beam to other satellites. • Retail delivery (SPS2000).

25. Space Solar Power the old way GEO: S=36000km MEO: ~10000km http://www.newscientist.com/data/images/archive/2631/26311601.jpg LEO: ~400km Earth Radius ~6370km

26. Afternoon Sun system. • 80 minutes of access per 24 hours per location. • This orbit performs 23 revolutions around the earth every 48 hours. Ground Tracks of 6 sun-synchronous satellites at 1900 km

27. Absorption vs. Spillover Most GEO/ 5.8GHz architectures assume receivers sized for 83% beam capture because of the large receiver size Example: 5.8GHz: 84% Beam capture, 95% Transmission through atmosphere Net capture = 0.95*0.84 = 80% 220GHz: 99% Beam capture, 90% transmission = 89% Benefits of compact antenna are far beyond this. Both laser and mmwave enable compact, 99% capture receivers.

28. Nanotube broadband direct solar conversion antenna, with narrow-band high-efficiency receivers for mm wave. http://www.aip.org/png/2004/221.htm Antenna for Visible Light “Shown: An array of aligned, but randomly placed, carbon nanotubes which can act like a radio antenna for detecting light at visible wavelengths. The scale bar is one micron in length. Wang et al., Applied Physics Letters, 27 September 2004.”