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Innovations Required for Retail Beamed Power Transmission Over Short Range

Innovations Required for Retail Beamed Power Transmission Over Short Range. Girish Chowdhary and Narayanan Komerath Daniel Guggenheim School of Aerospace Engineering Georgia Institute of Technology Atlanta. IMETI 2010, Orlando, FL June 2010.

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Innovations Required for Retail Beamed Power Transmission Over Short Range

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  1. Innovations Required for Retail Beamed Power Transmission Over Short Range Girish Chowdhary and Narayanan Komerath Daniel Guggenheim School of Aerospace Engineering Georgia Institute of Technology Atlanta IMETI 2010, Orlando, FL June 2010

  2. 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

  3. Market Indicator For Micro-Scale Retail Power “Malawian teenager .. transformed his village by building electric windmills out of junk… Jude Sheerin, BBC News 1 October 2009 http://news.bbc.co.uk/2/hi/africa/8257153.stm • Notes: • Original motivation: power a radio to fance to music • Business plan: charging station for cellphones. • Lesson: Demand for cellphones and other electronic systems is far ahead of • national Power Grid expansion rate.

  4. Introduction Beaming power may be a viable alternative to constructing wire 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. This paper looks at the rationale, applications, choices and tradeoffs.

  5. Overview • Long-term rationale: why we are interested • Near-term applications • Technical barriers • Cost tradeoffs • Possible innovations needed

  6. Aerospace Interest: Stratospheric/ Space Power Grid • Way to exchange power between day/night regions to boost solar power baseload capability • Minimize storage needed to capture wind power spikes • Provide evolutionary path to space solar power Retail power beaming is the end-user infrastructure for delivery of power in a global exchange, including space solar power.

  7. Why SSP? Why has it Remained a Dream?

  8. 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).

  9. 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

  10. Near-term Rationale: Wired vs. Beamed Power Transfer

  11. Potential Near-Term Applications • Broad area low intensity power distribution for emergencies • Areas with cellphones/ players but no power grid • Rapid power delivery to remote military or scientific outposts • High endurance miniature robots • Distributed micro power generation • Remote area exploration • Increased range for electrically powered vehicles • Rapid restructuring of grid topology for damage mitigation

  12. Technical Issues • Antenna size vs. distance relationship means that space grid system is not viable at any power cost, without going to millimeter wave regime, above 100 GHz • Atmospheric transmission window at 220 GHz seems ideal • Anything above 10 GHz is extremely sensitive to rain; finding alternative routes is the answer. • Poor conversion efficiency from DC to mm wave

  13. Feasibility of low range low efficiency BPTS Modified Friis equation calculation shows that antenna combination of (20m; 5m) is adequate for 100km range at 200 GHz. (20m;1m) is good for 10 km

  14. 20m transmitter diameter, 5m receiver diameter MM waves offer high free-space efficiency Power Efficiency, Pr/Pt Frequency in GHz

  15. Cost Model, Wired vs. Retail Beamed Power Infrastructure Wired installation: Effective cost per km (~ US$1M / km) linear with distance above a threshold level, steep cost for last few kms of retail distribution. BPTS: power loss proportional to square of (distance/frequency). Effective cost ~ US$100K/km (1 transmitter/ relay per km)

  16. Cost-effectiveness of BPTS vs. Wired Grid Installation Effective Installation Cost in $K Even at 20 GHz, BPTS is more cost effective than wired installation for distance less than 6 km Range in km

  17. Required Technological Innovations • Efficient mm Wave Generation • Thyratrons and Gyratrons replaceable by massive arrays of microchips with digital synthesis and phase-locked loops. Use in communications and radar are routine; power transfer needs development. Translate optical rectenna R&D to mm waves • Advancements in Antennas: Antenna directionality/gain in 220 GHz regime using DSP. • Circuits and Switching in the 200-250 GHz regime • Advancement in Thermal management systems: Efficient use of waste heat from conversion/ transmission at high power levels. • Decentralized grid management through networked control • 200GHz radiation monitoring: Health and safety issues need investigation • Compact converters from DC/AC to mmwave and back, for micro power systems. • Smart Grid devices for micro-scale power capture and grid input measurements.

  18. Conclusions • BPTS offers a way for technology market and convenience to leap-frog the conventional wired grid expansion to unconnected areas. • BPTS using mm waves offers compact size and high free-space efficiency. 220 GHz is desirable for compatibility with Space Power Grid. • Several applications including connectivity for micro-renewable power systems. • Basically cost-effective compared to wired grid installation, when renewable, fluctuating power sources are used. • DPS / PLL approaches appear to offer more efficient and cost-effective conversion to and from mm wave regime. • Technological innovations needed include improved antenna design, efficient frequency conversion, radiation monitoring, and antenna design.

  19. ACKNOWLEDGEMENTS The work reported in this paper was made possible by resources being developed for the “EXTROVERT” cross-disciplinary learning project under NASA Grant NNX09AF67G S01. Mr. Anthony Springer is the Technical Monitor.

  20. The Space Power Grid: Synergy Between Space, Energy and Security Policies Narayanan Komerath Daniel Guggenheim School of Aerospace Engineering Georgia Institute of Technology Atlanta, GA 30332-0150 USA komerath@gatech.edu

  21. Update on Space Solar Power from New Scientist Magazine: Dec.22. 2008 http://www.newscientist.com/data/images/archive/2631/26311601.jpg

  22. Long Term Goal • Constant, “24-365” solar power available from Space. Concepts to build solar power satellites are unable to get past the “cost to first power” barrier. • Problem specification: • How to develop an evolutionary approach where revenue generation starts early with small investment, and ultimately scales up to full-scale Space Solar Power (SSP) in 25-30 years. • Viable business plan and minimal costs to taxpayers. • Approach: • Build, market and infrastructure for SSP by facilitating terrestrial renewable power. • Articulate the policy needs and show examples of successful practice. This paper: Interplay of technology, economics, global relations and national public policy involved in making this concept come to fruition.

  23. GEO: Geo-Stationary Earth Orbit • Satellite “stationary” 36,000 km above equator. • 1960s concepts: Very large solar-cell arrays in GEO, beaming electric power down as microwaves to large receivers on Earth. Frequencies << 10 billion cycles per second (10GHz) are generally not absorbed by the atmosphere - selected for power transmission. • NASA etc. focused on GEO-based collector/converter/beaming. Consequences: • Frequency must be very good for atmospheric transmission: <10GHz. • Minimum beam diameter is several kilometers for this frequency range and distance, regardless of power transmitted.  large stations. • 2. Assembly at GEO. • 3. Enormous ground infrastructure. • 4. Only massive government spending as possible funding source. • 5. Published estimate of “$300B to first power” is based on 1960s estimate of $100 per pound to low earth orbit via Space Shuttle. Actual cost today is ~ $14000/lb to LEO via SPS • Real issue is lack of an evolutionary path to get the SSP system through initial infrastructure development, to a self-sustaining size.

  24. New Window Of Opportunity: Renewable Power & Climate Control • “Baseload Power” criterion forces renewable plants to installfossil-burning auxiliary generation • Best locations for wind and solar extraction are high deserts, plateau edges, mountain slopes, glacier bases and coastlines. • Insufficient, non-existent or inefficient distribution grids over most of the planet. • Huge temporal fluctuations in power prices especially in urban areas.

  25. 10-fold fluctuation in power cost:Real-time retail beaming opportunity From Landis, G., “ Reinventing the Solar Power Satellite” http://gltrs.grc.nasa.gov/reports/2004/TM-2004-212743.pdf

  26. 3-Step Evolutionary Approach to Space Solar Power Years 6-23: L/MEO constellation enables global reach for renewable plants in ideal locations. Revenue from baseload supply and price differentials. Year 23+: Replacement sats augmented with power converters. Year 23+ High MEO/ GEO reflectors concentrate sunlight on L/MEO converters to feed grid System expands.

  27. Method of Analysis • Frequency and orbit height  antenna sizes, efficiency • + Power level per satellite  satellite mass  revenue, # of satellites and ground stations •  System costs from NASA/USAF & FUTRON cost models. • NPV analysis with target cost /KWH, IRR, growth model • System size for breakeven in 17 years. • Minimum power transaction level per satellite  satellite size • Effect of public funding on cost per KWH. Results • Frequency 200 GHz or greater. • 60MW handling capacity per satellite • Startup with 20 satellites and 12 plants • Phase 1 breakeven in 17 years, grows to 100 satellites and 100 plants.

  28. Technology Challenges • Conversion efficiency to & from 200-220 GHz • Satellite waveguides • Thermal management • Atmospheric transmission schemes • Direct conversion technology for Phase 2 • Ultralight conformable reflectors for Phase 3 high orbit.

  29. Economics Of The Space Power Grid SSP • Business case is based on 5 features: • Allow solar and wind power plants to • achieve baseload provider status, • compete for premium prices by exchanging power with plants anywhere. • locate at prime, remote sites including islands, • reduce need for backup power generation. • receive carbon credits, qualify for larger public investment. • 2) Eliminate need for major assembly in orbit, minimizes development and launch costs. • 3) Match constellation size to growth of participating plants and revenue. • 4) Use of a constellation as a power grid minimizes the impact of weather by providing transmission alternatives. • 5) Early revenue growth with a few satellites and participating plants, eliminating cost-to-first-power barrier of GEO-based concepts.

  30. Breakeven power cost of 30 cents /KWh with IRR of 8% within 23 years from project start, given the first satellite launch in Year 6, with zero government funding. • With $6B govt. investment in development, achievable without large increase in system efficiency. • Carbon Credits, savings in transmission infrastructure, improve the economics.

  31. Results: Phase 1 SPG, 200GHz, 2000km Constellation

  32. Water Absorption Loss vs. Frequency http://www.islandone.org/LEOBiblio/microwave_transm.gif

  33. Atmospheric Transmission in the 200-250 GHz regime

  34. Special Policy Needs / Opportunities of the Space Power Grid • Global real-time energy trading (expanded from US model) • Distributed terrestrial transmission infrastructure (Smarter Grid, DG) • Public acceptance of beamed power from Space (“IPOD” model? ) • Global technology sharing on Space systems (ITAR vs. ESA model) • Global Infrastructure Collaboration Model (ESA model; IATA model) • Integration with Utility-Scale Terrestrial Power (EU- TRANS-CP) • Retail Beamed Power Transmission Systems (BPTS paper) • Integration with micro renewable power systems (MRES paper) • Global model for carbon credits (Copenhagen?) • Global model for renewables portfolio (EU example?) • Global model for Infrastructure Avoidance Credit? (ESA argument)

  35. EU TRANS-CP European Union’s Trans-Mediterranean Connection for Concentrated Solar Power (TRANS-CP) proposes to set up a high-voltage DC grid connecting solar plants in the Sahara desert across the Mediterranean and English Channel to North Atlantic / North Sea British/German / Dutch wind generators.

  36. EU TRANS-CP Recommendations

  37. Security Concerns, Space Law and a Global Infrastructure Consortium • Concern about militarization • Access to national space facilities • Dual-use technologies • Competitive issues mixed with security laws • Risk of terrorist attack • Fear of being excluded from space resources Opportunity in Crisis & Common Imperative • Shift in security concerns from international rivalry to terrorism concerns. • Thick layer of security at individual level added to national criteria. • New technology and laws provide opportunity to rethink space security. • May render fragmented national rules irrelevant and superfluous.

  38. Global Govt – Commercial Consortium overall framework for private entrepreneurship: • - long-term government-backed financing available • – directly provided by participating nations, or • underwritten by Consortium through private and public funds. • Presence of the Consortium and infrastructure cuts lending risk • cuts loan costs. • Consortium model provides a consistent economic and policy solution. Consortium Answer to Resource Exploitation / Property Rights Issue All resource exploitation ventures must be multinational public ventures, - open to investors from all member nations, - limits on maximum stock ownership to avoid single-nation dominance - long-term leases awarded

  39. CONCLUSIONS • Obstacles and issues in bringing space solar power to earth are discussed. • Congruence of international interest in renewable energy sources and in reducing greenhouse gas emissions, provide a window of opportunity to bring about Space Solar Power in synergy with the development of clean renewable power on earth. • Policy initiatives advanced in Europe for comparable solar power grid project are discussed. • The special features of the space power grid are presented, and shown to provide an excellent vehicle for global collaboration. While substantial technical challenges remain, there are viable paths for these challenges, as well as for the economics and public/ international collaboration needed to make Space Solar Power available to humanity. • Public policy initiatives needed for renewable energy, are already acceptable in many nations. • Security concerns that appear to pose formidable obstacles are cited as also posing unprecedented opportunities for wel-controlled collaboration between nations, through the participation of personnel who are cleared at the individual level, and through sequestering of technologies particular to the project as done in the European Space Agency’s projects. • The European TRANS-CP project is cited as a relevant current initiative to develop suitable policy.

  40. Business Case The business case is based on 4 features: 1) Enabling development of new solar and wind power plants by boosting their competiveness Qualify these plants for larger public investment. 2) Early revenue growth with a few satellites and participating plants Minimizes cost-to-first-power obstacle of GEO-based concepts. Constellation growth is matched to commissioning of renewable power plants Reduced lag between investment and revenue generation 3) L/MEO satellites: small antenna size and beam width compared to GEO Global reach Eliminates need for major assembly in orbit, Minimizes development and launch investment. 4) Minimizing the impact of weather by providing different alternatives for power transmission to the ground-based grid.

  41. Previous Work • Boechler STAIF 2006: • Achievable end-to-end efficiency • Near-term no better than 50% of present terrestrial urban grid • Long term (direct conversion from broadband solar to beamed narrowband) match or exceed that of the terrestrial grid. • Komerath , IAC 2006: • System based on 140 GHz regime and a constellation of 36 sun-synchronous satellites at 800km altitude. • Efficiencies not at the levels achieved in the 2.4 GHz regime. • Komerath,AIAA Space 2008: • Compared the economics of using different frequencies and choices of orbits. Frequency < 100 GHz not viable. • Combination of near-equatorial, polar and elliptic orbits can offer the necessary features of long transmission times from power plants, and retail worldwide power delivery.

  42. Orbits and Transmission Scenarios • Scenario 1: Near-equator plants and receivers: • 2000 km orbit height • Access time within 45-degree cone, of 7 to 10 minutes at ground stations. • For stations near the equator, the first several satellites are placed in orbits near the equator. • Thus a system start-up with as few as 6 satellites and 12 plants can be considered.

  43. Scenario 3 is High Latitude, Burst-Mode Transmission Burst-mode transmission for a few seconds (up to 2 minutes at 60 degree latitude, more at higher latitudes) may be repeated at regular intervals essentially through each day and night, with only a few satellites. Scenario 4 is the Steady State Phase 1 SPG As the number of satellites rises, sun-synchronous orbits become viable for continuous transmission. For the 1900km sun-synchronous orbit, 72 satellites are needed, which is well below the expected number of satellites in an established SPG system.

  44. CONCLUSION

  45. Opportunity How can we achieve self-sustaining growth toward space solar power with reasonable investmentlevel? 1. GEO SSP:Immense receivers, sats and cost-to-first power. 2. SPS2000: LEO sats beaming over wide areas 3. Temporal and geographic price differential compensates for losses in beamed transmission (Landis, Bekey et al). 4. Renewable-energy plants need large backup fossil generators or storage for baseload status. 5. Ideal solar and wind plants sites are deserts, high plateaux and mountain ridges: remote but low atmospheric losses. 6. Near millimeter wave regime: compact antenna/receivers 7. Window of support for synergistic development of power plants and SPS distribution infrastructure. 8. Solutions on the horizon for AC- near mm beam conversion efficiency problem, direct solar conversion to mm wave, and spacecraft high-power thermal management?

  46. SPG Status Summary Synergy with terrestrial renewable power economics brings large policy advantages. 220 GHz and laser advantages in sizing, orbit selection and ground facility design, outweigh additional losses in atmospheric propagation. 2. System calculation sized for 220 GHz may work much better with lasers depending on conversion and beaming. 2. Lower limit of power per spacecraft for breakeven ~ 60 MW. 3. Initial power plant output levels just below capacity of spacecraft. 4. Orbit height at 2000 km above Earth enables system startup with 6 satellites and 6 power plants. Initial launch in Year 6. 5. Expand to steady state size of 102 sats and 101 power stations for 30-year break-even. Replace sats with augmented ones after 17 years of operation. 6. Phase 1 system in isolation breaks even with no public up-front grants, and a 6 percent ROI over 30 years. 7. Public funding <$3B in first 10 years brings delivered price of power from 30 cents to 24 cents per KWH. 8. Phases 2 and 3 can be started at Year 23 with replacement satellites, on a profitable Phase 1 market and infrastructure.

  47. Once Phase 1 is shown to be self-sustaining, Phases 2 and 3 become much easier Replacement or additional satellites in Years 23 onwards, incorporate receiver/converters sized for ~ 160MWe each. High-intensity design to capture 100 suns or more in intensity. (~ 80m dia)) Brayton cycle thermal management with auxiliary power generation at other frequencies. Dual frequency system would enable use of 200GHz for space-to-space beaming and low frequencies for atmospheric propagation. Constellation of ultralight collectors in high orbits (to minimize drag) to focus broadband sunlight to the receivers. Launch cost to high orbits minimized. 200-satellite constellation would generate 32GWe. Equivalent to 320 new nuclear reactors. As high-intensity converter technology advances, 200 satellites may handle upto 320GWe. Limited by acceptable size of L/MEO constellation.

  48. Long-Term Technical Issues Present show-stopper: Conversion efficiency to and from 220GHz (or lasers) for Phase 1. Finding ways around the atmospheric propagation loss - using terrestrial grid to avoid places of bad weather - tuning to narrow bands & power levels for optimal transmission - Different systems for space-space transmission and atmospheric. Backup Option: - In phase 3, LEO-LEO transmission may not be needed, so we can use lower frequencies, suited to larger power levels and spacecraft sizes. 3. Spacecraft thermal management with multistage power generation. Concepts for upto 10MW being studied. 4. Direct conversion from broad-band solar for Phases 2& 3. Efficiency and mass per unit power. - High intensity solar cells - Broadband/ multiband stacked cells - Optical rectennae 5. Breakthrough in efficiency and mass per unit power of converting between 200GHz and 5.8GHz regimes.

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