Innovations Required for Retail Beamed Power Transmission Over Short Range

Girish Chowdhary and Narayanan Komerath Daniel Guggenheim School of Aerospace Engineering

Georgia Institute of TechnologyAtlanta

IMETI 2010, Orlando, FL June 2010

Beamed Retail Power Transmission/ Distribution System

mm wave to DC

conversion

mm wave to DC

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DC to mm wave

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DC to mm wave

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Beam Formation Transmission & Reception

•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

“Malawian teenager .. transformed his village by building electric windmills out of junk… Jude Sheerin, BBC News 1 October 2009http://news.bbc.co.uk/2/hi/africa/8257153.stm

Market Indicator For Micro-Scale Retail Power

Notes: 1.Original motivation: power a radio to fance to music2.Business plan: charging station for cellphones.Lesson: Demand for cellphones and other electronic systems is far ahead ofnational Power Grid expansion rate.

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.

Introduction

Overview

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

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.

Why SSP? Why has it Remained a Dream?

Feature SSP Ground-based solar power

Steady generation 24 hour, year-round. ~12,000KWh/m^2 per yr

Daily /seasonal/ weather fluctuations. Average ~900 to 2,300 KWh/yr

Waste heat Dissipated in Space Released on Earth

Transmission efficiency Low, weather-dependent High, independent of weather (see above)

Receiver/distributor Infrastructure size

Massive for GEO sats due to beam width, for any power level

Scalable from rooftop to Sahara size

Generator size Massive for GEO sats. Scalable

Installation cost per watt Very high due to GEO launch cost

Moderate

The Space Power Grid Approach

•Exploit large geographical, daily and seasonal fluctuations in power cost.•Beam to other satellites.•Retail delivery (SPS2000).

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.

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

Near-term Rationale: Wired vs. Beamed Power Transfer

Wire Grid Beamed Power

Excellent efficiency with high voltage lines (~94%)

Requires large transmission infrastructure.

Large amount of developed land, trees cleared etc

Remote area maintenance

Power line hazards under and near lines: high voltage, aircraft collision, ice and wind storm issues

Vandalism and terror attacks

High cost as number of receiving points increases

Low efficiency (~20 to 50%)

Few transmission and reception points

Clear line of sight, can be above tree level

Concentrated at points

Radiation hazard along the beam

Less susceptible

Each device has to have a converter

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

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

Feasibility of low range low efficiency BPTS

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Antenna diameter= 20m, 5mAntenna diameter= 20m, 1m

Antenna diameter= 30m, 5m

Modified Friis equation calculation shows that antenna combination of (20m; 5m) is adequate for100km range at200 GHz.(20m;1m) is good for 10 km

MM waves offer high free-space efficiency

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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)

Cost-effectiveness of BPTS vs. Wired Grid Installation

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Even at 20 GHz, BPTS is more cost effectivethan wired installation for distance less than 6 km

Required Technological Innovations

•Efficient mm Wave GenerationThyratrons 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.

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.

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.

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Narayanan KomerathDaniel Guggenheim School of Aerospace Engineering

Georgia Institute of TechnologyAtlanta, GA 30332-0150 USA

komerath@gatech.edu

The Space Power Grid: Synergy Between Space, Energy and Security Policies

Space Power Grid: Redistributing EnergySpace Power Grid: Redistributing Energy

http://www.newscientist.com/data/images/archive/2631/26311601.jpg

Update on Space Solar Power from New Scientist Magazine: Dec.22. 2008

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.

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: 1.Frequency must be very good for atmospheric transmission: <10GHz. 2.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.

New Window Of Opportunity: Renewable Power & Climate Control

•“Baseload Power” criterion forces renewable plants to install fossil-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.

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

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.

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.

Method of Analysis

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.

• 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.

Technology Challenges

Business case is based on 5 features: 1)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.

Economics Of The Space Power Grid SSP

Feature SPG

Steady generation Constellation ensures that some face the Sun at all times, without GEO.

Transmission efficiency Weather dependence alleviated by choice of atmospheric transmission paths.

Infrastructure size Small due to lower orbit (2000km) and high frequency (200 GHz)

Generator Scalable

Installed cost per watt Moderate.

Infrastructure investment Pays for itself on terrestrial power generation. Expands to capture space solar power after break-even. 17 years to improve conversion technology before Phase 2 launch. Phase 3 (high orbit, large area) system is independent of conversion technology on mid-orbit system.

•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.

Parameter Value

Satellite Power Level: 60MW

Satellite mass: 4510 kg

Launch cost to 2000 km high circular orbit: $ 19.8M

Development cost for system: $ 330M

Production cost for 1st 36 satellites: $1370M

Ground facilities development cost: $1000M

Per satellite annual mission operations and data analysis cost: $2.75M

Ground station power level $55MW

Cost of production of power 4 cents / KWH

End-to-end efficiency of beaming power grid 0.3

Sales price at delivery point 30 cents / KWH

Gross margin 5 cents / KWH

SPG share of gross margin: 4.5 cents / KWH

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

October 2008

http://www.islandone.org/LEOBiblio/microwave_transm.gif

Water Absorption Loss vs. Frequency

Atmospheric Transmission in the 200-250 GHz regime

1. Global real-time energy trading (expanded from US model)2. Distributed terrestrial transmission infrastructure (Smarter Grid, DG)3. Public acceptance of beamed power from Space (“IPOD” model? )4. Global technology sharing on Space systems (ITAR vs. ESA model)5. Global Infrastructure Collaboration Model (ESA model; IATA model)6. Integration with Utility-Scale Terrestrial Power (EU- TRANS-CP)7. Retail Beamed Power Transmission Systems (BPTS paper) 8. Integration with micro renewable power systems (MRES paper)9. Global model for carbon credits (Copenhagen?)10. Global model for renewables portfolio (EU example?)11. Global model for Infrastructure Avoidance Credit? (ESA argument)

Special Policy Needs / Opportunities of the Space Power Grid

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.

EU TRANS-CP

Policy Issues Financial Benefits

•Discrepancy of Awareness and Action

•Feed-in Tariffs to foster innovation.

•Renewable Portfolio Standards (RPS)

•Competitive Bidding for RPS capacity allotments

•Net metering.

•Renewable Energy Certificates

•Green Power Purchasing

•Grants to producers and consumers

•Low-interest loans

•Tax exemptions, rebates

•Depreciation

•Demand guarantees, price controls

•Market access

•Land access

•Environmental licenses

EU TRANS-CP Recommendations

1. Concern about militarization2. Access to national space facilities3. Dual-use technologies4. Competitive issues mixed with security laws5. Risk of terrorist attack6. 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.

Security Concerns, Space Law and a Global Infrastructure Consortium

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

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.

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.

Business Case

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.

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.

Orbits and Transmission Scenarios

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.

CONCLUSION

October 2008

Opportunity

How can we achieve self-sustaining growth toward space solar power with reasonable investment level? 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/receivers7. 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?

October 2008

1. Synergy with terrestrial renewable power economics brings large policy advantages. 2. 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.

SPG Status Summary

October 2008

Once Phase 1 is shown to be self-sustaining, Phases 2 and 3 become much easier

1. 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.

2. 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.

October 2008

Long-Term Technical Issues

1. Present show-stopper: Conversion efficiency to and from 220GHz (or lasers) for Phase 1.

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 rectennae5. Breakthrough in efficiency and mass per unit power of converting between 200GHz and 5.8GHz regimes.

October 2008

Summary of Recommended Approach

Long-term solution: Years 6-23: Space Power Grid transacting power between renewable plantsYears 20 - 30 Full scale SSP growth.

Forward Base Retail Delivery: Year 1? Ship to base using UAV / LTA reflector. Need to ensure air dominance. Use either radar frequencies or lasers. (no need for solar power here)Year 6: Regional power plant to base with LEO satellites (6 needed for continuous transmission. Cheaper power generation - renewable or not). Year 6: CONUS plant with L/MEO satellites (SPG phase 1: Renewable power plants) Year 15? SSP collectors in high orbits, L/MEO converter/retail beaming satellites. (SPG Phase 3; Use space solar power)

Research priorities:1. Conversion efficiency to and from beamed energy2. Direct conversion from broadband to beamed energy: efficiency and mass per unit power.

- optical rectennae- lasers?

October 2008

ARCHITECTURE Independent Variables

Parameter Baseline Why

Orbit height above surface 880 – 1200 km Launch cost, antenna size, sun-sync orbits, retail beaming

Atmospheric transmission frequency

200-245 GHz Reduce antenna sizes, avoid water bands

Internal Rate of Return 8% Infrastructure Consortium

Phase Array transmission 45 deg. half-angle Cover 90 degree azimuth of sky

Initial number of ground stations 100 Revenue generation rate

Initial number of satellites 36 Near-continuous beaming

October 2008

SPG Satellite System Characteristics

Power transmitted (design, MW) 250 Average beam intensity, uniform, at ground, w/m^2 1273 Average beam intensity, uniform, at satellite, w/m^2 127323 Antenna mass, kg 38.9 Mass for space -space antennae, kg 546 Cooling system mass: 2000kg/2.5MW 2000 Mass of fluid, for 400K heating in 60 seconds at 2.5MW, kg

400

Other systems 1000 With margin of 1000 kg, total satellite mass, kg 5000

October 2008

Business Case:Parameters for Phase 1: Space Power Grid Launch cost at $6K/kg to 880km, $M 30

Per satellite cost for one of the first 36, $M 30 Operations cost per satellite per year, $M 5 Satellite system development cost, $M 1000 Ground facilities dev elopment cost for 1 st 100 stations

1000

Connection cost per additional station, $M 25 Cost of production of power, $/KWh 0.04 Fraction received as useful electric power 0.3 Sales price, $ per KWh 0.2 Gross profit per KWh 0.02 Beamed average MW per pl ant 100 MWh per year, for 1 plant at 50% duty cycle, per satellite available (100%=36sats)

12175

October 2008

Parameters for Phase 2: Augmented SPG Collector/Converter Diameter, m 300 Area, sq.m 70686 Satellite Mass: Add 2000kg 7000 Per satellite cost, $M 42 Launch cost @$6000/kg, $M 42 Solar conversion efficiency 0.25 KWh per year per ASPG sat, at 50% duty cycle 100,621,000 End-to-end efficiency 0.4 Cost of production 0 Sales price, $per KWh, Phase 2 0.15 Gross profit per KWh 0.06 Gross profit per year per Augsat, $M 6.04

October 2008

Phase 3: Full Space Solar Power ParametersCollector Diameter 3km

Satellite Mass: 0.015kg/m^2 106029

Per satellite cost, $M 100

Launch cost @$10000/kg, $M 1060

Solar collector efficiency 0.995

KWh per year per SSP sat, at 100% duty cycle 80E+09

End-to-end efficiency 0.4

Cost of production 0

Sales price, $per KWh, Phase 2 0.15

Gross profit per KWh 0.06

Gross profit per year per Augsat, $M 4806

Total KWh per year added by 96 sats 7.69E+12

Note: MEO satellite costs still exceed $110B for 100 collectors(300 sq km of solar collection), but at realistic launch cost, and in a staged manner over 40 years, tied to revenue generation

October 2008

Prior Work

Direct Approach: 100 megasatellites in GEO, large earth stations. 2.4GHz beams.

Step-by-step approaches: • All involve satellites and beaming from GEO or beyond, or lunar power plants and

earth-based receivers. (Large beam spread, high cost of GEO access)• Cost of earth-based receivers, and marginal cost per installed watt of power in space,

continue to be large. • Bekey et al (IAC1995): Beam Canadian power through GEO reflectors to Japanese

ground station with reservoir. 35% Internal Rate of Return projected. Recent concepts:• SPS2000: Retail, wide-beam power beaming from LEO sat (Nagotomo, 1991).• Modular GEO sat, each module self-contained (IAC2005)• Laser beaming (IAC2005)• Direct-conversion laser with 38% efficiency (Saiki, IAC2005)

October 2008

End-to-End Efficiency Projections

Short-term using SPG: 40%conversion from solar to DC70% conversion DC to microwave 0.9x0.9 for atmospheric traverse0.98 for in-space transmission90% conversion from microwave to useful powerTotal: Short-term: 20% of original, delivered to end-user.

Long-term: 50% direct conversion, solar to microwave36% of original solar delivered to end-user

Full SPS: 99% capture from GEO; only one atmosphere pass.39% of original solar delivered to end-user

Conventional terrestrial: 40%conversion from solar to DC (using best technology)Near 100% conversion to hi-voltage AC.94% delivered to end-user. Total: 38% of original solar.

Short-term:50% of conventional

Long-term: Slightly better than conventional

October 2008

Ground Component

•Ground stations located at ideal solar / wind collector locations.

•US Southwest, South Dakota, Hawaiian Islands, North African, Gobi, Thar and Australian deserts and Greenland are examples envisaged.

•Retail receiving stations on the ground can be located almost anywhere - much smaller than those for GEO-located SSP systems. •No need to co-locate receiving stations with generator stations except for power smoothing.

October 2008

TECHNOLOGY ISSUES•LEO sats alleviate launch cost.•Serve sites at extreme latitudes with minimal atmospheric transmission penalties. •Shorter transmission distance (1,200km to LEO vs. 36,000 km to GEO) - smaller receivers.•The limiting transmission is between satellites (2,400 km) or less.• Waveguides to distribute incoming power.• Heat rejection issue: No more complex than for SSP; partial recovery using thermo-electric systems

Tradeoffs:•10GHz range: Low absorption, but large receivers/ less efficient reception; Interference.

•95 - 140 GHz: small receivers, more efficient reception. Higher atmospheric absorption. Forces ground stations to dry, high locations.

•Cloud cover problem alleviated by having LEO system. Multiple choices of beam path.

•Tradeoff between system mass costs, atmospheric absorption and unreliability due to weather (alleviated by having multiple earth station choices separated by several kilometers) not properly understood, since much of the high-frequency data comes from astronomical observatories until now.

October 2008

Direct Conversion to Microwave

•Direct Solar Conversion to microwave beams with 50% efficiency and reduced mass by 2035.

•To replace current global production with solar energy at 50% efficiency, 5600 sq.km of solar collector area in space (where solar intensity is 1GW/sq.km) is required.

•1950s: Solar-Powered Masers with projected efficiency of 50%•2005: Solar-Powered Laser with 38% efficiency demonstrated.

•Deploying large ultra-thin collectors with high-intensity solar cell arrays is an alternative to any Direct Conversion technology, alleviating technological risk.

•SPG satellites will then be replaced with Direct Conversion Augmented-SPG (DCA-SPG) satellites, with a 1km diameter sun-tracking ultra light collector and converter on each adding 0.5 GW to the grid.

October 2008

Full Space Solar Power Phase

•GEO sun-sats (2040s?) : 100 sq.km ultra light collector/ reflectors that focus sunlight onto the 1sq.km collectors of the DCA-SPG.

•Each is expected to add 50GW to the grid at 50% efficiency.

•System of 72 LEO satellites and 72 GEO ultralight mirrors, with a 70% transmission efficiency, will generate 90% of today’s global energy production.

October 2008

Cost• Baseline sizing to recover 50% of system deployment cost in 20 years from savings in costs of ground

transmission, based on current cost of long-term debt.

• Satellite cost < cost of replacement GPS satellite.

• Basic cost of delivered power from SPG is twice that of US domestic power cost (efficiency is only half as much).

Advantages yet to be quantified:

• Use excess power from spikes in generation at “green” plants (wind / solar).• Deliver to peak-demand locations (greater revenue)• Access markets with much higher present-day costs• Market for beamed power in Space• Industries enabled by point retail delivery anywhere on Earth

Disadvantages of The Competitors, Yet to Be Quantified:

• Kyoto Protocol / equivalent CO2 penalties• Added costs to nuclear energy generation/ waste disposal costs

October 2008

Comparison with Conventional SSP and Terrestrial Solar

SSP SPG Terrestrial Solar

Energy Production

Primary solar generation

Exchange; new terrestrial plants, Augmented SPG, then Full SSP

Constrained by duty cycle, & location

Launch cost >$13,200/kg to GEO

$6,600/kg to 1215km alt. orbit N/A.

Space Mass >1kg/kw <0.01kg/kw for SPG phase;

0.1 kg/kw in DCA/SSP phases

N/A

Cost Items to First Power

Sats + grnd rec’ers

Space system + ground x’mission & rec’ng + control.

Gnd system+ line + land costs.

Duty cycle 24hr w/ reflectors

24 hr – with multiple sources 6hr/day; weather

Assembly LEO assembly, boost to GEO

Pre-assembled – deploy in LEO. Earth construction

October 2008

CONCLUSIONS

• SSP can be made viable by integrating new realities of environmental and energy policy issues.

• “Space Power Grid” uses LEO to exchange power across the world - market opportunity.

• “End-to-end efficiency” shows beamed power transmission to be inferior to transmission via high voltage lines if only US/European domestic markets are considered.

• Long-term end-to-end efficiency superior to present power grid.• However, a space-based power grid opens up various markets and opportunities that

are otherwise closed. • Present concept provides a revenue-generating evolutionary path towards SSP• Key breakthrough sought is in high-efficiency solar-powered Masers.

• Current advances in solar-powered lasers offer hope.

October 2008

Our Approach: 3-Stage Evolution1.Microwave converters and beaming equipment installed.2. Thirty-six 200-MW SPG satellites launched. 3. SPG in operation. 4. Direct converter-augmented satellites: DCA-SPG 5. SSP collector beams sunlight to SPG: Full Space Solar Power