Strato solar introduction 2011 6 30

StratoSolarGeographically independent

Reliable

Cheap

Solar Energy

Ed Kelly

StratoSolar systems

6/29/2011 StratoSolar 2

StratoSolar-PV StratoSolar-CSPA giga Watt electrical power, utility scale PV

system tethered and floating at 20km altitude over

Northern California. The system is 3600m in

diameter, assembled from 100 arrays, each 360m in

diameter and 100m thick.

A buoyant solar concentrator floating at 20km altitude in

the stratosphere near Colusa in Northern California

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


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


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


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


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.


Wind deflecting the tether and platform


Average troposphere

Average stratosphere

Worst tropo

Average strato

Average tropo

Worst strato

Worst tropo

Worst strato

10MW

platform

1GW

array

Worst tropo

Average strato

Worst tropo

Worst strato

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.


6/29/2011 StratoSolar Confidential 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.


$-

$0.10

$0.20

$0.30

$0.40

$0.50

$0.60

$0.70

$1.00 $1.50 $2.00 $2.50 $3.00 $3.50

$/k

Wh

bu

sb

ar

$/W (peak) Construction Cost

PV Electricity cost($/kWh) vs. capital cost($/W) for different sunlight(kWh/m2/year)

worst 800

average 1300

best 1950

StratoSolar 3100

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.

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



$94 $75

$158

$308

$195

$97

$19

$40

$75

$47

$28 $36

$77

$142

$90

$25

$-

$100

$200

$300

$400

$500

$600

CCGT StratoSolar-PV ($3/W)

Utility scale thin film PV ($3.4/W)

Rooftop PV ($5/W) Solar thermal Onshore Wind

20-y

r le

velized

$/M

Wh

Impact of taxes on LCOE (California 2010)

Tax Credit

5-yr MACRS

Busbar

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

http://www.ethree.com/public_projects/renewable_energy_costing_tool.html

http://www.cpuc.ca.gov/PUC/energy/Procurement/LTPP/LTPP2010/2010+LTPP+Tools+and+Spreadsheets.htm

1G Watt 100 module array3600m diameter


10M Watt modular platform360m diameter


Real Estate

Strato solar introduction 2011 6 30