Space-based solar power

Space-based solar power

From Wikipedia, the free encyclopedia

See also: Solar panels on spacecraft

This article's use of external links may not follow Wikipedia's policies or

guidelines. Please improve this article by removing excessive or inappropriate

external links, and converting useful links where appropriate into footnote references. (April 2014)

This article is written like a personal reflection or opinion essay that states the

Wikipedia editor's particular feelings about a topic, rather than the opinions of

experts. Please help improve it by rewriting it in an encyclopedic style. (May 2011)

NASA Suntower concept.

Space-based solar power (SBSP) is the concept of collecting solar power in space (using an

"SPS", that is, a "solar-power satellite" or a "satellite power system") for use on Earth. It has

been in research since the early 1970s.

SBSP would differ from current solar collection methods in that the means used to collect

energy would reside on an orbiting satellite instead of on Earth's surface. Some projected

benefits of such a system are a higher collection rate and a longer collection period due to the

lack of a diffusing atmosphere and night time in space.

Part of the solar energy is lost on its way through the atmosphere by the effects of reflection

and absorption. Space-based solar power systems convert sunlight to microwaves outside the

atmosphere, avoiding these losses, and the downtime (and cosine losses, for fixed flat-plate

collectors) due to the Earth's rotation.

Besides the cost of implementing such a system, SBSP also introduces several new hurdles,

primarily the problem of transmitting energy from orbit to Earth's surface for use. Since wires

extending from Earth's surface to an orbiting satellite are neither practical nor feasible with

current technology, SBSP designs generally include the use of some manner of wireless

power transmission. The collecting satellite would convert solar energy into electrical energy

on board, powering a microwave transmitter or laser emitter, and focus its beam toward a

collector (rectenna) on Earth's surface. Radiation and micrometeoroid damage could also

become concerns for SBSP.

Contents

1 History

o 1.1 SERT

o 1.2 JAXA

2 Advantages

3 Disadvantages

4 Design

o 4.1 Solar concentrator

o 4.2 Microwave power transmission

o 4.3 Laser power beaming

o 4.4 Orbital location

o 4.5 Earth-based receiver

o 4.6 In space applications

5 Dealing with launch costs

6 Building from space

o 6.1 From lunar materials launched in orbit

o 6.2 On the Moon

o 6.3 From an asteroid

o 6.4 Gallery

7 Counter arguments

o 7.1 Safety

8 Timeline

9 In fiction

10 See also

11 References

12 External links

13 Videos

History

A laser pilot beam guides the microwave power transmission to a rectenna.

In 1941, science fiction writer Isaac Asimov published the science fiction short story

"Reason", in which a space station transmits energy collected from the Sun to various planets

using microwave beams.

The SBSP concept, originally known as satellite solar-power system (SSPS), was first

described in November 1968.[1]

In 1973 Peter Glaser was granted U.S. patent number

3,781,647 for his method of transmitting power over long distances (e.g. from an SPS to

Earth's surface) using microwaves from a very large antenna (up to one square kilometer) on

the satellite to a much larger one, now known as a rectenna, on the ground.[2]

Glaser then was a vice president at Arthur D. Little, Inc. NASA signed a contract with ADL

to lead four other companies in a broader study in 1974. They found that, while the concept

had several major problems – chiefly the expense of putting the required materials in orbit

and the lack of experience on projects of this scale in space – it showed enough promise to

merit further investigation and research.[3]

Between 1978 and 1986, the Congress authorized the Department of Energy (DoE) and

NASA to jointly investigate the concept. They organized the Satellite Power System Concept

Development and Evaluation Program.[4][5]

The study remains the most extensive performed

to date (budget $50 million).[6]

Several reports were published investigating the engineering

feasibility of such an engineering project. They include:

Artist's concept of Solar Power Satellite in place. Shown is the assembly of a microwave

transmission antenna. The solar power satellite was to be located in a geosynchronous orbit,

36,000 miles above the Earth's surface. NASA 1976

Resource Requirements (Critical Materials, Energy, and Land)[7]

Financial/Management Scenarios[8][9]

Public Acceptance[10]

State and Local Regulations as Applied to Satellite Power System Microwave

Receiving Antenna Facilities[11]

Student Participation[12]

Potential of Laser for SBSP Power Transmission[13]

International Agreements[14][15]

Centralization/Decentralization[16]

Mapping of Exclusion Areas For Rectenna Sites[17]

Economic and Demographic Issues Related to Deployment[18]

Some Questions and Answers[19]

Meteorological Effects on Laser Beam Propagation and Direct Solar Pumped

Lasers[20]

Public Outreach Experiment[21]

Power Transmission and Reception Technical Summary and Assessment[22]

Space Transportation[23]

The project was not continued with the change in administrations after the 1980 US Federal

elections.

The Office of Technology Assessment[24]

concluded

Too little is currently known about the technical, economic, and environmental aspects of

SPS to make a sound decision whether to proceed with its development and deployment. In

addition, without further research an SPS demonstration or systems-engineering verification

program would be a high-risk venture.

In 1997 NASA conducted its "Fresh Look" study to examine the modern state of SBSP

feasibility.[25]

In assessing "What has changed" since the DOE study, NASA asserted that:

US National Space Policy now calls for NASA to make significant investments in technology

(not a particular vehicle) to drive the costs of ETO [Earth to Orbit] transportation down

dramatically. This is, of course, an absolute requirement of space solar power.

Conversely, Dr. Pete Worden claimed that space-based solar is about five orders of

magnitude more expensive than solar power from the Arizona desert, with a major cost being

the transportation of materials to orbit. Dr. Worden referred to possible solutions as

speculative, and that would not be available for decades at the earliest.[26]

On Nov 2, 2012, China proposed space collaboration with India that mentioned SBSP, " . . .

may be Space-based Solar Power initiative so that both India and China can work for long

term association with proper funding along with other willing space faring nations to bring

space solar power to earth."[27]

SERT

SERT sandwich concept.NASA

In 1999, NASA's Space Solar Power Exploratory Research and Technology program (SERT)

was initiated for the following purposes:

Perform design studies of selected flight demonstration concepts.

Evaluate studies of the general feasibility, design, and requirements.

Create conceptual designs of subsystems that make use of advanced SSP technologies

to benefit future space or terrestrial applications.

Formulate a preliminary plan of action for the U.S. (working with international

partners) to undertake an aggressive technology initiative.

Construct technology development and demonstration roadmaps for critical Space

Solar Power (SSP) elements.

SERT went about developing a solar power satellite (SPS) concept for a future gigawatt

space power system, to provide electrical power by converting the Sun’s energy and beaming

it to Earth's surface, and provided a conceptual development path that would utilize current

technologies. SERT proposed an inflatable photovoltaic gossamer structure with concentrator

lenses or solar heat engines to convert sunlight into electricity. The program looked both at

systems in sun-synchronous orbit and geosynchronous orbit.

Some of SERT's conclusions:

The increasing global energy demand is likely to continue for many decades resulting

in new power plants of all sizes being built.

The environmental impact of those plants and their impact on world energy supplies

and geopolitical relationships can be problematic.

Renewable energy is a compelling approach, both philosophically and in engineering

terms.

Many renewable energy sources are limited in their ability to affordably provide the

base load power required for global industrial development and prosperity, because of

inherent land and water requirements.

Based on their Concept Definition Study, space solar power concepts may be ready to

reenter the discussion.

Solar power satellites should no longer be envisioned as requiring unimaginably large

initial investments in fixed infrastructure before the emplacement of productive power

plants can begin.

Space solar power systems appear to possess many significant environmental

advantages when compared to alternative approaches.

The economic viability of space solar power systems depends on many factors and the

successful development of various new technologies (not least of which is the

availability of much lower cost access to space than has been available), however, the

same can be said of many other advanced power technologies options.

Space solar power may well emerge as a serious candidate among the options for

meeting the energy demands of the 21st century. Space Solar Power Satellite

Technology Development at the Glenn Research Center—An Overview] James E.

Dudenhoefer and Patrick J. George, NASA Glenn Research Center, Cleveland, Ohio.

Launch costs in the range of $100–$200 per kilogram of payload to low Earth orbit

are needed if SPS are to be economically viable.[6]

JAXA

The May 2014 IEEE Spectrum magazine has a lengthy article "It's Always Sunny in Space"

by Dr. Susumu Sasaki.[28]

"It’s been the subject of many previous studies and the stuff of sci-

fi for decades, but space-based solar power could at last become a reality—and within 25

years, according to a proposal from researchers at the Japan Aerospace Exploration Agency

(JAXA)."

Advantages

The SBSP concept is attractive because space has several major advantages over the Earth's

surface for the collection of solar power.

There is no air in space, so the collecting surfaces could receive much more intense

sunlight, unobstructed by the filtering effects of atmospheric gasses, cloud cover,

there is no night, dust to be cleaned, clouds and other weather events. Consequently,

the intensity in orbit is approximately 144% of the maximum attainable intensity on

Earth's surface.[citation needed]

A satellite could be illuminated over 99% of the time, and be in Earth's shadow a

maximum of only 72 minutes per night at the spring and fall equinoxes at local

midnight.[29]

Orbiting satellites can be exposed to a consistently high degree of solar

radiation, generally for 24 hours per day, whereas the average earth surface solar

panels currently collect power for an average of 29% per day.[30]

Power could be relatively quickly redirected directly to areas that need it most. A

collecting satellite could possibly direct power on demand to different surface

locations based on geographical baseload or peak load power needs. Typical contracts

would be for baseload, continuous power, since peaking power is ephemeral.

Elimination of plant and wildlife interference.

Disadvantages

The SBSP concept also has a number of problems.

The large cost of launching a satellite into space

Inaccessibility: Maintenance of an earth-based solar panel is relatively simple, but

construction and maintenance on a solar panel in space would typically be done

telerobotically. In addition to cost, astronauts working in GEO orbit are exposed to

unacceptably high radiation dangers and risk and cost about one thousand times more

than the same task done telerobotically.

After being decommissioned, parts of it may stay in orbit and become space debris.

This space debris can create trouble for other space satellites.

The space environment is hostile; panels suffer about 8 times the degradation they

would on Earth.[31]

Space debris is a major hazard to large objects in space, and all large structures such

as SBSP systems have been mentioned as potential sources of orbital debris.[32]

The broadcast frequency of the microwave downlink (if used) would require isolating

the SBSP systems away from other satellites. GEO space is already well used and it is

considered unlikely the ITU would allow an SPS to be launched.[33]

The large size and corresponding cost of the receiving station on the ground.

Design

Artist's concept of a solar disk on top of a LEO to GEO electrically powered space tug.

Space-based solar power essentially consists of three elements:

a means of collecting solar power in space, for example via solar concentrators, solar

cells or a heat engine

a means of transmitting power to earth, for example via microwave or laser

a means of receiving power on earth, for example via a microwave antenna (rectenna)

The space-based portion will not need to support itself against gravity (other than relatively

weak tidal stresses). It needs no protection from terrestrial wind or weather, but will have to

cope with space hazards such as micrometeors and solar flares.

Two basic methods of conversion have been studied: photovoltaic (PV) and solar dynamic

(SD). Photovoltaic conversion uses semiconductor cells to directly convert photons into

electrical power. Solar dynamic uses mirrors to concentrate light on a boiler. The use of solar

dynamic could reduce mass per watt. Most analyses of SBSP have focused on photovoltaic

conversion (commonly known as ―solar cells‖).

Wireless power transmission was proposed early on as a means to transfer energy from

collection to the Earth's surface, using either microwave or laser radiation at a variety of

frequencies.

Solar concentrator

This section is empty. You can help by adding to it. (May 2014)

Microwave power transmission

William C. Brown demonstrated in 1964, during Walter Cronkite's CBS News program, a

microwave-powered model helicopter that received all the power it needed for flight from a

microwave beam. Between 1969 and 1975, Bill Brown was technical director of a JPL

Raytheon program that beamed 30 kW of power over a distance of 1-mile (1.6 km) at 84%

efficiency.[34]

Microwave power transmission of tens of kilowatts has been well proven by existing tests at

Goldstone in California (1975)[34][35][36]

and Grand Bassin on Reunion Island (1997).[37]

Comparison of laser and microwave power transmission. NASA diagram

More recently, microwave power transmission has been demonstrated, in conjunction with

solar energy capture, between a mountain top in Maui and the island of Hawaii (92 miles

away), by a team under John C. Mankins.[38][39]

Technological challenges in terms of array

layout, single radiation element design, and overall efficiency, as well as the associated

theoretical limits are presently a subject of research, as it is demonstrated by the Special

Session on "Analysis of Electromagnetic Wireless Systems for Solar Power Transmission" to

be held in the 2010 IEEE Symposium on Antennas and Propagation.[40]

In 2013, a useful overview was published, covering technologies and issues associated with

microwave power transmission from space to ground. It includes an introduction to SPS,

current research and future prospects.[41]

Laser power beaming

Laser power beaming was envisioned by some at NASA as a stepping stone to further

industrialization of space. In the 1980s, researchers at NASA worked on the potential use of

lasers for space-to-space power beaming, focusing primarily on the development of a solar-

powered laser. In 1989 it was suggested that power could also be usefully beamed by laser

from Earth to space. In 1991 the SELENE project (SpacE Laser ENErgy) had begun, which

included the study of laser power beaming for supplying power to a lunar base. The SELENE

program was a two-year research effort, but the cost of taking the concept to operational

status was too high, and the official project ended in 1993 before reaching a space-based

demonstration.[42]

In 1988 the use of an Earth-based laser to power an electric thruster for space propulsion was

proposed by Grant Logan, with technical details worked out in 1989. He proposed using

diamond solar cells operating at 600 degrees to convert ultraviolet laser light.

Orbital location

The main advantage of locating a space power station in geostationary orbit is that the

antenna geometry stays constant, and so keeping the antennas lined up is simpler. Another

advantage is that nearly continuous power transmission is immediately available as soon as

the first space power station is placed in orbit; other space-based power stations have much

longer start-up times before they are producing nearly continuous power.

A collection of LEO (Low Earth Orbit) space power stations has been proposed as a

precursor to GEO (Geostationary Orbit) space-based solar power.[43]

Earth-based receiver

The Earth-based rectenna would likely consist of many short dipole antennas connected via

diodes. Microwave broadcasts from the satellite would be received in the dipoles with about

85% efficiency.[44]

With a conventional microwave antenna, the reception efficiency is better,

but its cost and complexity are also considerably greater. Rectennas would likely be several

kilometers across.

In space applications

A laser SBSP could also power a base or vehicles on the surface of the Moon or Mars, saving

on mass costs to land the power source. A spacecraft or another satellite could also be

powered by the same means. In a 2012 report presented to NASA on Space Solar Power, the

author mentions another potential use for the technology behind Space Solar Power could be

for Solar Electric Propulsion Systems that could be used for interplanetary human exploration

missions.[45]

[46][47]

Dealing with launch costs

One problem for the SBSP concept is the cost of space launches and the amount of material

that would need to be launched.

Reusable launch systems are predicted to provide lower launch costs to low Earth orbit

(LEO).[48][49]

As of November 2013, one company, SpaceX, is two years along on a privately

funded multi-year development program for a reusable rocket launching system with the

stated intention to commercialize "fully and rapidly reusable" launch technology.[50][51][52]

SpaceX has completed eight test flights of their low-altitude booster return prototype,

Grasshopper,[53]

and one test flight of a high-altitude/high-velocity booster return test vehicle,

with a second booster return test flight planned for early 2014.[54][55]

Much of the material launched need not be delivered to its eventual orbit immediately, which

raises the possibility that high efficiency (but slower) engines could move SPS material from

LEO to GEO at an acceptable cost. Examples include ion thrusters or nuclear propulsion.

Power beaming from geostationary orbit by microwaves carries the difficulty that the

required 'optical aperture' sizes are very large. For example, the 1978 NASA SPS study

required a 1-km diameter transmitting antenna, and a 10 km diameter receiving rectenna, for

a microwave beam at 2.45 GHz. These sizes can be somewhat decreased by using shorter

wavelengths, although they have increased atmospheric absorption and even potential beam

blockage by rain or water droplets. Because of the thinned array curse, it is not possible to

make a narrower beam by combining the beams of several smaller satellites. The large size of

the transmitting and receiving antennas means that the minimum practical power level for an

SPS will necessarily be high; small SPS systems will be possible, but uneconomic.

To give an idea of the scale of the problem, assuming a solar panel mass of 20 kg per kilowatt

(without considering the mass of the supporting structure, antenna, or any significant mass

reduction of any focusing mirrors) a 4 GW power station would weigh about 80,000 metric

tons, all of which would, in current circumstances, be launched from the Earth. Very

lightweight designs could likely achieve 1 kg/kW,[56]

meaning 4,000 metric tons for the solar

panels for the same 4 GW capacity station. This would be the equivalent of between 40 and

150 heavy-lift launch vehicle (HLLV) launches to send the material to low earth orbit, where

it would likely be converted into subassembly solar arrays, which then could use high-

efficiency ion-engine style rockets to (slowly) reach GEO (Geostationary orbit). With an

estimated serial launch cost for shuttle-based HLLVs of $500 million to $800 million, and

launch costs for alternative HLLVs at $78 million, total launch costs would range between

$11 billion (low cost HLLV, low weight panels) and $320 billion ('expensive' HLLV, heavier

panels).[citation needed]

To these costs must be added the environmental impact of heavy space

launch emissions, if such costs are to be used in comparison to earth-based energy

production. For comparison, the direct cost of a new coal[57]

or nuclear power plant ranges

from $3 billion to $6 billion per GW (not including the full cost to the environment from

CO2 emissions or storage of spent nuclear fuel, respectively); another example is the Apollo

missions to the Moon cost a grand total of $24 billion (1970s' dollars), taking inflation into

account, would cost $140 billion today, more expensive than the construction of the

International Space Station.

However in 2013 based on Recent innovations, Electric Space: Space-Based Solar Power

Technologies & Applications [58]

suggested a new way to reduce costs by replacing smaller

satellites and in lower Orbits.

Building from space

From lunar materials launched in orbit

Gerard O'Neill, noting the problem of high launch costs in the early 1970s, proposed building

the SPS's in orbit with materials from the Moon.[59]

Launch costs from the Moon are

potentially much lower than from Earth, due to the lower gravity. This 1970s proposal

assumed the then-advertised future launch costing of NASA's space shuttle. This approach

would require substantial up front capital investment to establish mass drivers on the

Moon.[60]

Nevertheless, on 30 April 1979, the Final Report ("Lunar Resources Utilization for Space

Construction") by General Dynamics' Convair Division, under NASA contract NAS9-15560,

concluded that use of lunar resources would be cheaper than Earth-based materials for a

system of as few as thirty Solar Power Satellites of 10GW capacity each.[61]

In 1980, when it became obvious NASA's launch cost estimates for the space shuttle were

grossly optimistic, O'Neill et al. published another route to manufacturing using lunar

materials with much lower startup costs.[62]

This 1980s SPS concept relied less on human

presence in space and more on partially self-replicating systems on the lunar surface under

remote control of workers stationed on Earth. The high net energy gain of this proposal

derives from the Moon's much shallower gravitational well.

Having a relatively cheap per pound source of raw materials from space would lessen the

concern for low mass designs and result in a different sort of SPS being built. The low cost

per pound of lunar materials in O'Neill's vision would be supported by using lunar material to

manufacture more facilities in orbit than just solar power satellites.

Advanced techniques for launching from the Moon may reduce the cost of building a solar

power satellite from lunar materials. Some proposed techniques include the lunar mass driver

and the lunar space elevator, first described by Jerome Pearson.[63]

It would require

establishing silicon mining and solar cell manufacturing facilities on the Moon.[citation needed]

On the Moon

David Criswell suggests the Moon is the optimum location for solar power stations, and

promotes lunar solar power.[64][65]

The main advantage he envisions is construction largely

from locally available lunar materials, using in-situ resource utilization, with a teleoperated

mobile factory and crane to assemble the microwave reflectors, and rovers to assemble and

pave solar cells,[66]

which would significantly reduce launch costs compared to SBSP designs.

Power relay satellites orbiting around earth and the Moon reflecting the microwave beam are

also part of the project. A demo project of 1 GW starts at $50 billion.[67]

The Shimizu

Corporation use combination of lasers and microwave for the lunar ring concept, along with

power relay satellites.[68][69]

From an asteroid

Asteroid mining has also been seriously considered. A NASA design study[70]

evaluated a

10,000 ton mining vehicle (to be assembled in orbit) that would return a 500,000 ton asteroid

fragment to geostationary orbit. Only about 3,000 tons of the mining ship would be

traditional aerospace-grade payload. The rest would be reaction mass for the mass-driver

engine, which could be arranged to be the spent rocket stages used to launch the payload.

Assuming that 100% of the returned asteroid was useful, and that the asteroid miner itself

couldn't be reused, that represents nearly a 95% reduction in launch costs. However, the true

merits of such a method would depend on a thorough mineral survey of the candidate

asteroids; thus far, we have only estimates of their composition.[71]

One proposal is to capture

the asteroid Apophis into earth orbit and convert it into 150 solar power satellites of 5 GW

each or the larger asteroid 1999 AN10 which is 50x the size of Apophis and large enough to

build 7,500 5-Gigawatt Solar Power Satellites[72]

Gallery

A Lunar base with a mass driver (the long structure that goes toward the horizon).

NASA conceptual illustration

An artist's conception of a "self-growing" robotic lunar factory.

Microwave reflectors on the moon and teleoperated robotic paving rover and crane.

―Crawler‖ traverses Lunar surface, smoothing, melting a top layer of regolith, then

depositing elements of silicon PV cells directly on surface

Sketch of the Lunar Crawler to be used for fabrication of lunar solar cells on the

surface of the Moon.

Shown here is an array of solar collectors that convert power into microwave beams

directed toward Earth.

A solar power satellite built from a mined asteroid.

Counter arguments

Safety

The use of microwave transmission of power has been the most controversial issue in

considering any SPS design.

At the Earth's surface, a suggested microwave beam would have a maximum intensity at its

center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less

than 1 mW/cm2 outside the rectenna fenceline (the receiver's perimeter).

[73] These compare

with current United States Occupational Safety and Health Act (OSHA) workplace exposure

limits for microwaves, which are 10 mW/cm2,[74]

- the limit itself being expressed in

voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes.[citation

needed] A beam of this intensity is therefore at its center, of a similar magnitude to current safe

workplace levels, even for long term or indefinite exposure. Outside the receiver, it is far less

than the OSHA long-term levels[75]

Over 95% of the beam energy will fall on the rectenna.

The remaining microwave energy will be absorbed and dispersed well within standards

currently imposed upon microwave emissions around the world.[76]

It is important for system

efficiency that as much of the microwave radiation as possible be focused on the rectenna.

Outside the rectenna, microwave intensities rapidly decrease, so nearby towns or other human

activity should be completely unaffected.[77]

Exposure to the beam is able to be minimized in other ways. On the ground, physical access

is controllable (e.g., via fencing), and typical aircraft flying through the beam provide

passengers with a protective metal shell (i.e., a Faraday Cage), which will intercept the

microwaves. Other aircraft (balloons, ultralight, etc.) can avoid exposure by observing

airflight control spaces, as is currently done for military and other controlled airspace.

The microwave beam intensity at ground level in the center of the beam would be designed

and physically built into the system; simply, the transmitter would be too far away and too

small to be able to increase the intensity to unsafe levels, even in principle.

In addition, a design constraint is that the microwave beam must not be so intense as to injure

wildlife, particularly birds. Experiments with deliberate microwave irradiation at reasonable

levels have failed to show negative effects even over multiple generations.[78]

Some have suggested locating rectennas offshore,[79][80]

but this presents serious problems,

including corrosion, mechanical stresses, and biological contamination.

A commonly proposed approach to ensuring fail-safe beam targeting is to use a retrodirective

phased array antenna/rectenna. A "pilot" microwave beam emitted from the center of the

rectenna on the ground establishes a phase front at the transmitting antenna. There, circuits in

each of the antenna's subarrays compare the pilot beam's phase front with an internal clock

phase to control the phase of the outgoing signal. This forces the transmitted beam to be

centered precisely on the rectenna and to have a high degree of phase uniformity; if the pilot

beam is lost for any reason (if the transmitting antenna is turned away from the rectenna, for

example) the phase control value fails and the microwave power beam is automatically

defocused.[77]

Such a system would be physically incapable of focusing its power beam

anywhere that did not have a pilot beam transmitter.

The long-term effects of beaming power through the ionosphere in the form of microwaves

has yet to be studied, but nothing has been suggested which might lead to any significant

effect.

Timeline

1941: Isaac Asimov published the science fiction short story "Reason," in which a

space station transmits energy collected from the sun to various planets using

microwave beams.

1968: Dr. Peter Glaser introduces the concept of a "solar power satellite" system with

square miles of solar collectors in high geosynchronous orbit for collection and

conversion of sun's energy into a microwave beam to transmit usable energy to large

receiving antennas (rectennas) on Earth for distribution.

1973: Dr. Peter Glaser is granted United States patent number 3,781,647 for his

method of transmitting power over long distances using microwaves from a large (one

square kilometer) antenna on the satellite to a much larger one on the ground, now

known as a rectenna.[2]

1978–81: The United States Department of Energy and NASA examine the solar

power satellite (SPS) concept extensively, publishing design and feasibility studies.

1982: Boeing proposal[81]

1987: Stationary High Altitude Relay Platform a Canadian experiment

1994: The United States Air Force conducts the Advanced Photovoltaic Experiment

using a satellite launched into low Earth orbit by a Pegasus rocket.

1995–97: NASA conducts a ―Fresh Look‖ study of space solar power (SSP) concepts

and technologies.

1998: The Space Solar Power Concept Definition Study (CDS) identifies credible,

commercially viable SSP concepts, while pointing out technical and programmatic

risks.

1998: Japan's space agency begins developing a Space Solar Power System (SSPS), a

program that continues to the present day.

1999: NASA's Space Solar Power Exploratory Research and Technology program

(SERT, see below) begins.

2000: John Mankins of NASA testifies in the U.S. House of Representatives, saying

"Large-scale SSP is a very complex integrated system of systems that requires

numerous significant advances in current technology and capabilities. A technology

roadmap has been developed that lays out potential paths for achieving all needed

advances — albeit over several decades.[6]

2001: Dr. Neville Marzwell of NASA states, "We now have the technology to convert

the sun's energy at the rate of 42 to 56 percent... We have made tremendous progress.

...If you can concentrate the sun's rays through the use of large mirrors or lenses you

get more for your money because most of the cost is in the PV arrays... There is a risk

element but you can reduce it... You can put these small receivers in the desert or in

the mountains away from populated areas. ...We believe that in 15 to 25 years we can

lower that cost to 7 to 10 cents per kilowatt hour. ...We offer an advantage. You don't

need cables, pipes, gas or copper wires. We can send it to you like a cell phone call—

where you want it and when you want it, in real time."[82]

2001: NASDA (One of Japan's national space agencies before it became part of

JAXA) announces plans to perform additional research and prototyping by launching

an experimental satellite with 10 kilowatts and 1 megawatt of power.[83][84]

2003: ESA studies[85]

2007: The US Pentagon's National Security Space Office (NSSO) issues a report[86]

on October 10, 2007 stating they intend to collect solar energy from space for use on

Earth to help the United States' ongoing relationship with the Middle East and the

battle for oil. A demo plant could cost $ 10 billion, produce 10 megawatts, and

become operational in 10 years.[87]

The International Space Station may be the first

test ground for this new idea, even though it is in a low-earth orbit.

2007: In May 2007 a workshop is held at the US Massachusetts Institute of

Technology (MIT) to review the current state of the SBSP market and technology.[88]

2009: Several companies announce future SBSP partnerships and commitments,

including Pacific Gas and Electric (PG&E) & Solaren,[89][90][91]

Mitsubishi Electric

Corp. & IHI Corporation,[92][93]

Space Energy, Inc.,[94]

and Japan Aerospace

Exploration Agency.[95]

2010: Europe's EADS Astrium announces SBSP plans.[96][97][98][99]

2010: Professors Andrea Massa and Giorgio Franceschetti announce a special session

on the "Analysis of Electromagnetic Wireless Systems for Solar Power Transmission"

at the 2010 Institute of Electrical and Electronics Engineers International Symposium

on Antennas and Propagation.[100]

2010: The Indian Space Research Organisation and US' National Space Society

launched a joint forum to enhance partnership in harnessing solar energy through

space-based solar collectors. Called the Kalam-NSS Initiative after the former Indian

President Dr APJ Abdul Kalam, the forum will lay the groundwork for the space-

based solar power program which could see other countries joining in as well.[101]

2010: The National Forensics League announces the resolution for the 2011–2012

debate season to be substantial space exploration and/or development. Space Based

Solar Power becomes one of the most popular affirmative arguments.

2012: China proposed joint development between India and China towards

developing a solar power satellite, during a visit by former Indian President Dr APJ

Abdul Kalam.[102]

In fiction

Space stations transmitting solar power have appeared in science-fiction works like Isaac

Asimov's Reason (1941), that centers around the troubles caused by the robots operating the

station. Asimov's short story "The Last Question" also features the use of SBSP to provide

limitless energy for use on Earth.

In the video game Sid Meier's Alpha Centauri, the player can construct a city improvement

called an "Orbital Power Transmitter" which, while expensive, provides energy to all other

cities. Constructing many of these results in huge bonuses to energy production for all cities

the player owns.

In the novel "Skyfall" (1976) by Harry Harrison an attempt to launch the core of powersat

from Cape Canaveral ends in disaster when the launch vehicle fails trapping the payload in a

decaying orbit.

Several Simcity games have featured space-microwave power plants as buildable options for

municipal energy, along with (unrealistic) disaster scenarios where the beam strays off the

collector and sets fire to nearby areas.

In the manga and anime Mobile Suit Gundam 00, an orbital ring containing multiple solar

collectors and microwave transmitters, along with power stations and space elevators for

carrying power back down to Earth's surface, are the primary source of electricity for the

Earth in the 22ndSpace-based solar power (SBSP), or historically space solar power (SSP)

is a system for the collection of solar power in space, for use on Earth. SBSP differs from the

usual method of solar power collection in that the solar panels used to collect the energy

would reside on a satellite in orbit, often referred to as a solar power satellite (SPS), rather

than on Earth's surface. In space, collection of the Sun's energy is unaffected by the various

obstructions which reduce efficiency or capacities of Earth surface solar power collection.

The World Radiation Centre's 1985 standard extraterrestrial level for mean solar irradiance at

one astronomical unit from the Sun is 1367 W/m2.[1]

The integrated total terrestrial solar

irradiance is 950 W/m2.[2]

Extraterrestrial solar irradiance is thus 144% of the maximum

terrestrial irradiance, and has a different radiation profile, including wavelengths blocked by

the atmosphere. A major interest in SBSP stems from the length of time the solar collection

panels can be exposed to a consistently high amount of solar radiation. For most of the year, a

satellite-based solar panel can collect power 24 hours per day, whereas a terrestrial station

can collect for at most 12 hours per day, unless at the poles, but then only for 6 months of the

year, if weather permits, and only during peak hours—irradiance under the best of conditions

is quite reduced near sunset and sunrise.

Collection of solar energy in space for use on Earth introduces two new problems and can

alleviate an existing one. First, installation of the collection satellites, and second transmitting

energy from them to the surface for use. The first requires upgrading and extension of

existing solar panel technologies. Since wires extending from Earth's surface to an orbiting

satellite are neither practical nor currently possible, many SBSP designs have proposed the

use of microwave beams for wireless power transmission. The collecting satellite would

convert solar energy into electrical energy, powering a microwave emitter oriented toward a

collector on the Earth's surface. Dynamic solar thermal power systems on satellites are also

being investigated. Since the beam can be steered, it can be directed as needed to

accommodate periods of high power use in particular locations (e.g., during the hottest part of

the day in summer, or cold spells in winter). As well, one of the current problems of

electricity use is long distance transmission from generating sites to usage sites. Because at

least one type of receiving antenna, the rectenna, is relatively inexpensive, it may be possible

to reduce the need for electricity transmission lines by sensible siting of receiving antennas,

potentially reducing costs and grid interconnect failures, such as the blackouts of 1965 and

2003.

Some problems normally associated with terrestrial solar power collection would be entirely

avoided by such a design, e.g., dependence on weather conditions, contamination or

corrosion, damage by wildlife or plant encroachment, etc. Other problems will likely be

encountered, such as more rapid radiation damage or micrometeoroid impacts.

century. Throughout the ages the light of the sun has fueled photosynthesis, freeing oxygen

and providing food for the animal kingdom. It supplies the light to grow trees -- bringing us

wood. Its heat evaporates the oceans to bring the rains that form our rivers and lakes. It

causes the winds to blow and brings us warmth and comfort. It took uncounted millions of

years for the sun working with the earth to create the coal, oil, and gas we are burning so

recklessly today.

-- Ralph Nansen (retired Boeing scientist), SUN POWER: The Global Solution for the

Coming Energy Crisis, Copyright 1995.

During 1982, Boeing designed a solar power satellite system that could supply most of the

country at the time with electricity. The energy crisis of the late 1970s had inspired scientists

at U.S. Department of Energy and NASA to re-examine the feasibility of solar power

satellites based on the Space Solar Power concept, developed in the late 1960s by Dr. Peter

Glaser. DOE and NASA subsequently organized the Satellite Power System Concept

Development and Evaluation Program, and The Boeing Company and its heritage company,

Rockwell International, led these early efforts. Rockwell won the study contract issued by the

Marshall Space Flight Center, and Boeing won the contract with the Johnson Space Center.

In 1977, the Air Force Concentrating Photovoltaic Array study program conducted by

Rockwell International concluded that solar concentrator arrays can survive the tough

environments of outer space. Rockwell developed a preliminary design for a hardened solar

concentrator. Rockwell also studied a way to use mirrors that concentrated the sunlight in a

solar furnace to heat fluid, powering electricity-generating turbine engines. Involved in the

Rockwell studies were engineers who carried their expertise with them when the company's

space systems became part of Boeing in 1996. Later studies showed that silicon solar cells

had a higher life expectancy than the thermal engine system, so the Boeing solar power

satellite became the system of choice.

The Boeing solar power satellite would be a space platform the size of a small city. Deployed

some 22,000 miles above the equator in geosynchronous Earth orbit (GEO), these satellite

platforms would carry billions of silicon solar cells that would transform sunlight directly

into electrical energy transmitted to Earth as microwaves through antennas. Rectifying

antennas on the ground would convert the microwaves to direct-current electricity, which

would be fed into the nation's power lines. A three-year evaluation study conducted by the

DOE and NASA concluded that there were no known insurmountable technical,

environmental or economic issues that should stop the development of the solar power

satellite. Boeing had already developed solar power technology for the Lunar Orbiter, the

flying photographic laboratory that encircled the moon in 1966 and took pictures of 90

percent of the lunar surface.

The Boeing solar power satellites could be constructed either in low Earth orbit for later

shipment to the higher geosynchronous orbit or constructed directly at the higher orbit. Large

space freighters, known as heavy-lift launch vehicles, would carry out-sized cargo pallets into

low Earth orbit, where these pallets would be deposited and directed to docking stations at a

space construction base. A modified Space Shuttle Orbiter could carry the personnel needed

on the orbiting construction site (much as the International Space Station is constructed

today).

The early studies indicated that the revenue from one solar power satellite, producing 10,000

megawatts of electricity sold at a rate of 40 mills per kilowatt hour, would produce $105

billion in 30 years. Forty-five satellites would produce more than $4.7 trillion, less than the

cost of electricity generated by the oil-burning electricity generation plants. Solar power

satellites, a Boeing press release pointed out in 1982, might be expensive to bring on line but

would not be dependent on fuel costs. The sun's rays are free.

Boeing asked Congress to embark on a carefully phased plan that would progress from

concept definition to technology verification to subscale demonstration. At the time, the

greatest apparent stumbling block seemed to be political rather than technological. NASA's

first priority was space rather than energy. The Department of Energy was not involved with

research involving space. By the 1990s, when the continued conflicts around the world's oil-

producing countries highlighted the need for new sources of energy, strong advocates for

solar power satellites were in the Department of Defense. Using fossil fuels to power military

bases and power trucks and airplanes was becoming increasingly expensive, so reducing

DOD energy costs would contribute to national security.

In 1995, NASA began a "Fresh Look" study of space solar power techniques and concepts; in

1998, Congress authorized modest funding for further concept definition and technology

development. The future of sun power brightened again during the energy crisis of 2007,

when the National Security Space Office of the U.S. Department of Defense formed a study

group of 13 leading research organizations and space advocacy groups. The group

recommended that space-based solar power receive substantial national investment as a way

to meet the country's future energy needs. The Space Solar Alliance for Future Energy

formed to advocate investment in space-based solar power technologies to address the

planet's future energy needs. In October 2008, the Air Force Research Laboratory sponsored

a workshop on "The State of Space Solar Power Technology" to examine ongoing research

into a space-centric, beamed-power energy system.

By 2008, the Boeing team working on solar power satellites had 30 years experience. Boeing

scientists proposed and managed a half-dozen related contracts for NASA and produced

about a dozen related publications. These activities included a conceptual design of a

robotically constructed GEO satellite and work on smaller-scale, laser-photovoltaic satellites

and transmission systems, which used receivers on Earth to produce solar-photovoltaic

power. They reworked the Lunar Rover still on Earth to see if a laser-powered Lunar Rover,

using wireless power transmission, could reach permanently shadowed lunar polar areas that

may contain ice, and they studied the construction of a large solar power satellite to produce

cryogenic propellants from water. Boeing scientists also looked at ways a space colony on the

moon could find, shape and transport the materials to build the huge satellites more

economically than by building them in space, which required launching space solar power

satellite components from Earth. They led a study on solar power satellites presented to the

National Security Space Office, and they participated in a NASA/DOD study of options for a

near-term demonstration of space solar power technology in low Earth orbit. Other Boeing

research and development projects also include a range of applications for beamed power

technology, including microwave technology for space solar power.

In November 2008, Spectrolab Inc., a wholly owned Boeing subsidiary, received the 2008

SpotBeam Award for Space Innovation from the California Space Authority in recognition of

its 50 years of advancements in photovoltaic solar cell technology, solar panels and related

products. Spectrolab was the world's leading supplier of photovoltaic solar cells, solar panels,

searchlights and solar simulators, and Spectrolab cells powered 60 percent of all satellites

orbiting the Earth, as well as the International Space Station.

SPACE-BASED SOLAR POWER

Solar power directly from space may arrive sooner than

you think.

Did You Know?

Every hour, more solar energy reaches the Earth than humans use in a year.

About 30%

of this energy is reflected back into space by the atmosphere.

Waste Not

Since clouds, atmosphere and nighttime are absent in space, satellite-based solar panels

would be able to capture and transmit substantially more energy than terrestrial solar panels.

How Does it Work?

Solar panel equipped, energy transmitting satellites collect high intensity, uninterrupted solar

radiation by using giant mirrors to reflect huge amounts of solar rays onto smaller solar

collectors. This radiation is then wirelessly beamed to Earth in a safe and controlled way as

either a microwave or laser beam.

{ Microwave Transmitting Solar Satellite }

Sunlight reflects off these large mirrors into the center of the satellite

v

>

Here the sunlight is transformed into uninterrupted microwave energy and beamed to Earth.

So... how far into space do

microwave transmitting solar satellites need to go?

384,400 KM

THE EARTH

THE SATELLITE:

35,000 KM

away from

the Earth

This distance is called

geostationary orbit

THE MOON

{ Laser Transmitting Solar Satellite }

These satellites would operate as a group with other similar satellites, due to their small size.

How far out are the

laser transmitting satellites?

THE EARTH

LASER SATELLITE

400 KM

Microwave Satellite

(35,000 KM)

{Laser Solar Satellites}

VS

{Microwave Solar Satellites}

Relatively low startup costs in the $500 million to $1 billion range.

The single launch per laser transmitting satellite would be self assembling, lowering costs and

risks substantially.

The small diameter of the laser beam would make it simpler and cheaper to implement on the

ground.

P

R

O

S

Steady, uninterrupted transmission of power through rain, clouds, and other atmospheric

conditions.

Safely transmit power through air at intensities no greater than midday sun.

Provide upwards of 1 GW of energy to terrestrial reciever, enough to power a large city.

Comparatively low power of each individual satellite, in the area of 1 to 10 MW per satellite,

would require several satellite to make a substantial impact.

There are several safety concerns with lasers in space, such as blinding and weaponization.

Laser transmitting satellites would have trouble beaming power through heavy clouds and

rain.

C

O

N

S

Production cost in the tens of billions of dollars range, requiring as many as 100 launches into

space, with space based assembly required.

The terrestrial receiver would be several kilometers in diameter.

The long distance of the satellite from Earth would make it nearly impossible to repair.

SPACE-BASED SOLAR POWER

Solar power directly from space may arrive sooner than

you think.

Did You Know?

Every hour, more solar energy reaches the Earth than humans use in a year.

About 30%

of this energy is reflected back into space by the atmosphere.

Waste Not

Since clouds, atmosphere and nighttime are absent in space, satellite-based solar panels

would be able to capture and transmit substantially more energy than terrestrial solar panels.

How Does it Work?

Solar panel equipped, energy transmitting satellites collect high intensity, uninterrupted solar

radiation by using giant mirrors to reflect huge amounts of solar rays onto smaller solar

collectors. This radiation is then wirelessly beamed to Earth in a safe and controlled way as

either a microwave or laser beam.

{ Microwave Transmitting Solar Satellite }

Sunlight reflects off these large mirrors into the center of the satellite

v

>

Here the sunlight is transformed into uninterrupted microwave energy and beamed to Earth.

So... how far into space do

microwave transmitting solar satellites need to go?

384,400 KM

THE EARTH

THE SATELLITE:

35,000 KM

away from

the Earth

This distance is called

geostationary orbit

THE MOON

{ Laser Transmitting Solar Satellite }

These satellites would operate as a group with other similar satellites, due to their small size.

How far out are the

laser transmitting satellites?

THE EARTH

LASER SATELLITE

400 KM

Microwave Satellite

(35,000 KM)

{Laser Solar Satellites}

VS

{Microwave Solar Satellites}

Relatively low startup costs in the $500 million to $1 billion range.

The single launch per laser transmitting satellite would be self assembling, lowering costs and

risks substantially.

The small diameter of the laser beam would make it simpler and cheaper to implement on the

ground.

P

R

O

S

Steady, uninterrupted transmission of power through rain, clouds, and other atmospheric

conditions.

Safely transmit power through air at intensities no greater than midday sun.

Provide upwards of 1 GW of energy to terrestrial reciever, enough to power a large city.

Comparatively low power of each individual satellite, in the area of 1 to 10 MW per satellite,

would require several satellite to make a substantial impact.

There are several safety concerns with lasers in space, such as blinding and weaponization.

Laser transmitting satellites would have trouble beaming power through heavy clouds and

rain.

C

O

N

S

Production cost in the tens of billions of dollars range, requiring as many as 100 launches into

space, with space based assembly required.

The terrestrial receiver would be several kilometers in diameter.

The long distance of the satellite from Earth would make it nearly impossible to repair.