June 28, 2007

Taking space based solar power to the megawatt level

The cheapest launch for a moderate sized payload is the
Dnepr rocket. It costs $10 million and can launch 4500 kg to LEO. $2222/kg. They are flying now and there are 150 more until 2020.


Dnepr rocket

We can either user light thin film solar cells or we can use thin film reflectors to concentrate onto high efficiency cells.

Thin film solar cells on Kapton can be 1250+ W/kg.

Record power density 4300 W/kg AMO (1367 W/m²) Gossamer Thin Film CP1 Polyimide/Amorphous Silicon (CP1/a-Si:H)

There are 20kg deployment booms for 400 square meters. 12kg of the CP1/a-Si:H can provide 50kw of power. The present cost estimate for CP1/a-Si:H solar is $250 per Watt at the deployed array level.

The cost of the 250 kW (250,000 Watts) rigid cell solar power arrays for the International Space Station was $600M. This is comaparable to a cost of $62M for a 250 kW CP1/a-Si:H solar array with Ultra-lightweight deployment. A $600M CP1/a-Si:H solar array, of equal cost to the ISS solar array, would provide 2.4 MW (2,400,000 Watts) of power with cost reductions for space fabricated for Aluminum/Graphite composite tri-beam truss beam structural elements.

CSG solar makes the thin film solar At the end of 2006, the solar production capacity is 20-25 MW.

CSG solar plant

Mantech International bought SRS technologies which had license the CP1 and CP2 technology.

If one were going to try to use CP1/a-Si:H as the major part of solar space power, then some financial arrangement would be required to boost production and reduce unit costs.

We should look at develop improvements to make lighter, bigger and cheaper inflatable booms.

NOTE: I had thought that magnetic inflation might have some advantages in weight etc... Plus I thought that magnetic inflation and the new very large space bubble ideas had the potential to make very large structures without assembly. But now that I have looked more at compressed gas and the other methods, those other methods
are not needed for this early stage and are probably still inferior and also not working at this time. Those ideas may be worth a look in the future and may be worth
developing but are not relevant to near term planning.

Or using the thin film reflectors onto the 40% efficient Spectrolab cells.

11 grams/square meter of kapton with a layer of reflective aluminum 4.4kg for a 400 square meter of reflective surface. $30/square meter in low volumes for aluminized kapton Perhaps get the price to $10/square meter or less in higher volumes of aluminized Kapton.
880kg for a 8,000 square meter sheet of kapton with aluminum (if all the light is reflected onto 40% efficient solar cells.

1366W/M**2 * 40% * 8,000 is 4MW.

Systems in the 2.4-4MW systems could be deployed. The reflector options seems like it would be the cheaper option to me.

Using 20kg deployment boom for 400 square meters.
4.4 kg for reflector material for 400 square meters.
20 kg for the Spectrolab concentrator cells and power modulation and other electronics and station keeping gear or truss.
218 KW from 400 square meters onto 40% efficient cells for about 44kg.
If a lightweight station keeping method could be produced. then you could have 100 of those systems launched with each Dnepr rocket. A total of 21 MW could be contained in each $10 million Dnepr launch if the supporting and deployment systems and structures can be kept light enough. $400K (40,000 square meters @ $10/meter) for load of aluminized Kapton reflector. Pricing for the Spectrolab cells ? Pricing for the deployment booms? Pricing for power and voltage converters and power beaming equipment and other electronics ? Price and weight for station keeping equipment ?

Use power for solar ion tugs or send power to other satellites.
Supply power to the ISS. It only has a few hundred KW.
Supply power to Bigelow’s hotels.
Supply power for military satellites.
Trial power beaming for lunar surface vehicles and missions.
New wave of communication satellites need 50 to 100 KW of power.
Supply power to costly earth based niches. Supply the really high peak power niches.
Perhaps power to remote islands, ships and facilities. Certain mobile military or commercial applications where the flexibilty of supply beamed power from space would make sense.

When supplying power to other satellites and space missions, there would be considerations of how best to supply that power. What form of power? Reflecting concentrated light to another satellites solar cells would increase power. New satellites could have boostable power designs, which could make it cheaper for them to operate at lower power levels at other times. Providing peak or top up power for when satellites need to operate more of their equipment.

A survey would need to be performed of existing and planned satellites which are power limited in their operations and need more power which a space power satellite could provide power. Also, a survey of planned space missions that could need more power. The ISS seems like a place that could perform more experiments and operations with boosted power. The ISS and other NASA missions could be the anchor customer. Three or more space power satellites would be needed to provide constant power beaming coverage.

For unusual ground operations, what are the high margin needs and what is the best way to provide the power.

Might be able keep the overall first system project to under $100 million. The thin film solar option could get pricy for the best thin films at about $600 million.

Power a fleet of solar ion tugs and momentum transfer tethers (the tugs and things will reduce costs fo LEO to GSO and L2). Provide a network of small power beaming satellites for space power infrastructure.
As the volume increases to 1 GW, the prices should get reduced (learning curve, improvements, economies of scale).

Reduce the size and weight and costs of deployment systems and the secondary electronics and support structures. Then start competing for supplying peak power for earth based power grid.
Supply 100+GW from space and use some it to power mining and processing industry on the moon (mostly robotic). The bootstrapping would be highly advanced at that point and we would be well on our way to going towards to building habitable infrastructure and providing most of the supplies from space based sources.


Tethers for boosting from LEO and/or Ion drive tugs.

Ultra-Light Amorphous Silicon Cell for Space Applications

Market Potential of CP1/a-Si:H Thin Film Solar Cells for Space and HAA Applications pdf Solar power for current space satellites is a billion dollar market.

High altitude platforms for communication and other services

Geoffrey Landis' paper on reinventing the solar power satellite

Space solar power public comment site that is hosted by the Space Frontier Foundation to assist the National Security Space Office study on Space-Based Solar Power development.

Space-Based Solar Power: An Opportunity for Strategic Security: a power point file

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