Presentation from CSP USA conference in Las Vegas on June 30th 2011

1. StratoSolar
Geographically independent
Reliable
Cheap
Solar Energy
Ed Kelly

2. StratoSolar systems
StratoSolar-PV StratoSolar-CSP
A giga Watt electrical power, utility scale PV A buoyant solar concentrator floating at 20km altitude in
system tethered and floating at 20km altitude over the stratosphere near Colusa in Northern California
Northern California. The system is 3600m in
diameter, assembled from 100 arrays, each 360m in
diameter and 100m thick.
6/29/2011 StratoSolar 2

3. What the CSP system does:
 Weather independent, 24/7 electricity from
concentrated solar power (CSP)
 Locations up to latitude 60 (as far north as Stockholm)
 Electricity in utility scale systems up to 1 GWe (one
Giga Watt Electrical Power output)
 Cost competitive with the lowest-cost coal-fired
systems
 Concentrate Sunlight in the Stratosphere with a large
mirror concentrator
 Pipe the concentrated light down to the ground with a
hollow tube Light Pipe
 Receive and store the concentrated energy at high
temperature
 Convert the high temperature stored energy to Electricity
at high efficiency
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4. CSP status
 Feedback: too risky to fund
 Lots of new ideas untested at scale
 Lots of big risky pieces
 No low cost incremental investment
 Possibility of catastrophic loss
 Evaluated the feedback and came up with a PV option
that reduced risk in many dimensions
 Only one untested idea
 Only one risky piece
 Low initial and incremental investment
 Very reduced risk of catastrophic loss
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5. What the PV system does
 Weather independent, photovoltaic solar power (PV)
 Locations up to latitude 60
 Electricity in utility scale systems from 10 MW to 1
GW in modular increments
 Cost competitive without subsidy
 Easily integrated into the grid, no backup generators
or long transmission lines required
 Convert sunlight to electricity in the stratosphere with a
large array of PV panels mounted on a rigid buoyant
platform
 Connect the panels to produce electricity as HVDC
 Transmit the HVDC electricity down a 20km combined
HVDC cable/tether to the ground
 Control the cable length with a winch
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6. Why it comes at a reasonable cost:
 The PV panels are exposed to 1.5 to 3.5X the solar
radiation of ground-based PV panels
 This means each square meter of PV panel gathers
1.5 to 3.5X the power of ground-based PV panels
 The PV array uses no land. No land cost, or site
development cost.
 The PV array support structure uses very little
material due to light structural loads.
 All construction materials are standard, off the shelf,
and low cost
 The PV panels are lower cost than ground-based PV
panels due to reduced panel packaging cost
 The electricity produced is predictable and does not
require backup generation
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7. Why it works: weather in the
Stratosphere
The stratosphere is a permanent inversion layer in the
earth’s atmosphere. Inversion layers effectively
isolate gas bodies. The calm weather free
stratosphere is isolated from the turbulent
troposphere below. There is no rain, hail, snow, or
moisture in the stratosphere and wind force is much
reduced and stable. This means that buoyant
platforms suspended in the stratosphere can be
permanently stationed there without needing to be
winched down in bad weather. It also means that PV
panels in the stratosphere don’t suffer water based
weather effects and can be simpler and cheaper to
manufacture.
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8. Wind deflecting the tether and platform
10MW
platform
Average troposphere Worst tropo Average tropo Worst tropo
Average stratosphere Average strato Worst strato Worst strato
1GW
array
Worst tropo Worst tropo
Average strato Worst strato
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9. Sunshine in the Stratosphere
Light from the sun at 20km altitude is both strong and
constant from dawn to dusk. At 20km a platform is
above over 90% of the atmosphere, so sunlight is not
significantly scattered or absorbed and there are no
clouds to interrupt power generation. This means that
on average PV panels produce multiples of the
energy they can generate on the ground, and just as
important, the energy is highly predictable and not
subject to interruption by clouds or storms.
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10. Benefit of 20km Altitude for Direct Normal
Solar Insolation
 Latitude 60 Winter Solstice:
Stockholm Helsinki
362W.hr/m2 vs. 6,327W.hr/m2
 Latitude 38 Winter Solstice
(SFO) 4,495W.hr/m2 vs.
11,828W.hr/m2
 These assume clear sky, so
actual benefit is much higher.
SFO average Dec/Jan daily
average is 2,900W.hr/m2 from
NREL 30 year data. 20km is
4X better. The multiplier for
Stockholm is 15X.
 These locations are
unsuitable for terrestrial CSP
because of clouds, moisture,
and wind, so the real benefit
is a new option previously
unavailable.
6/29/2011 StratoSolar Confidential 10

11. PV Electricity cost($/kWh) vs. capital
cost($/W) for different sunlight(kWh/m2/year)
$0.70
$0.60
$0.50
$/kWh busbar
$0.40
worst 800
$0.30 average 1300
best 1950
$0.20 StratoSolar 3100
$0.10
$-
$1.00 $1.50 $2.00 $2.50 $3.00 $3.50
$/W (peak) Construction Cost
Assumes 20 year life, 8.5% working average cost of capital (WACC) and 2% of capital cost for annual
operation and maintenance (O&M).
Worst sunlight is northern Europe, best is US southwest. Sunlight is in in average kWh/m2/year.
This chart illustrates well that the same plant with the same capital cost produces electricity with
highly variable cost depending on location. StratoSolar has the best location.
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12. PV electricity cost chart interpretation
 The PV plant capital cost axis ranges from $3.5/W to
$1.0/W, from today's $3.5/W cost to costs likely over
the next ten years
 PV is far from competitive without subsidy even in the
best locations over this timeframe
 StratoSolar is competitive using today's PV costs
 StratoSolar is geography independent so its efficiency
can apply to the location with the worst sunlight . The
same solar cells in a plant costing the same overall
can bring brighter than the desert sun to the far north
 The cost advantage for northern Europe exceeds a
factor of 3
6/29/2011 StratoSolar 12

13. Impact of taxes on LCOE (California 2010)
$600
$500
$142
$400
20-yr levelized $/MWh
$75
$300 Tax Credit
$90
5-yr MACRS
$77 Busbar
$47
$200
$40
$308
$25
$36 $28
$100 $195
$19 $158
$94 $97
$75
$-
CCGT StratoSolar-PV Utility scale thin Rooftop PV ($5/W) Solar thermal Onshore Wind
($3/W) film PV ($3.4/W)
Renewables source: http://www.ethree.com/public_projects/renewable_energy_costing_tool.html.
CCGT source: http://www.cpuc.ca.gov/PUC/energy/Procurement/LTPP/LTPP2010/2010+LTPP+Tools+and+Spreadsheets.htm
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14. 1G Watt 100 module array
3600m diameter
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15. 10M Watt modular platform
360m diameter
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