27-02-2013, 10:01 AM
SOLAR POWER CONSTELLATIONS IMPLICATIONS FOR THE UNITED STATES AIR FORCE
SOLAR POWER.pdf (Size: 147.21 KB / Downloads: 41)
Abstract
As the world population increases and natural resources used to produce energy decrease,
alternative methods to produce sustainable, environmental cost effective energy are required.
One proposed solution to the problem is solar power satellites. Solar power satellites are
satellites, which collect the energy of the sun, convert it onto a beam, and beam that energy to a
receiving antenna. The receiving antenna converts the beam into electricity and feeds the
electricity into a power grid. The receiving antenna may be located on another satellite, or on
Earth. Presented here are several solar power satellite proposals, architectures, incremental
technology demonstrations and predictions as to when they will become commercially viable.
Given the previous information, this paper analyzes the implications for the Air Force in relation
to doctrine and future plans. The research method consisted of a search of scientific journals,
published symposium papers, and research reports. The search focused on the current research
on solar power satellites, and Air Force programs, which have power issues. Based on the
research, the Air Force should plan to capitalize on the advantages of solar power satellite
constellations. Solar power satellites can assist with implementing various plans (i.e., long
endurance unmanned aerial vehicles, space-based radar, lasers, and small satellites), complying
with public law, and reducing the logistics tail associated with an expeditionary force.
Introduction
Currently the United States relies on fossil fuels to generate electrical power. The United
States acquires fossil fuels from both domestic sources and imports. Scientific predictions
indicate a “sharp decline in [fossil fuel] availability over the next 40 years.”1 As the world
population increases, and natural resources to produce energy decrease, alternative methods to
produce sustainable, environmental friendly, cost effective energy are required. One solution to
the lack of renewable energy resources is solar power satellites. A solar power satellite collects
energy from the sun and beams that energy to a receiving antenna, which converts the energy
into electricity. Peter Glaser first proposed solar power satellites in the late 60s. During the
energy crises in the 70s, the government took a hard look at them. The studies generated by this
inquiry essentially reported that solar power satellites were technologically possible but their cost
and launch requirements were not. Fifteen years later NASA conducted a study to determine if
anything had changed. The study concluded that costs were still high but they were not as high
as originally predicted and that there were no technological showstoppers. Utility companies and
many other nations are taking a close look at solar power satellites. Not only are they looking at
them as sources of power on Earth but as sources of power for satellites to reduce their size and
launch costs.
Background
Solar power satellites have the potential to supply the energy demands of the planet in a
variety of situations. There are several different proposals currently under research for
implementing solar power satellites. Some of the proposals place the satellites in low earth orbit,
others place them in geosynchronous orbit. The destination of the solar power satellite beam
also varies. The final destination of the beam may be earth, another satellite, or a relay station.
One thing they all have in common is wireless power transmission. Wireless power transmission
is one of the enabling technologies for solar power satellites. All of the solar power satellite
architectures also share the same barriers to implementation. A few of the current barriers to
realizing solar power satellites are solar cell inefficiencies, the high cost of launches and possible
communication frequency interference.
Solar Power Satellites
There are many different architectural designs for solar power satellites and solar power
satellite constellations. Despite all the differences in design architecture and orbital locations,
they all have some common features. Essentially, all solar power satellites collect solar power,
turn it into electricity, convert it into a beam, and beam it to a receiving antenna. Once received,
the receiving antenna converts the beam back into electricity, and feeds the electricity into a
power grid.1
A similar concept to the solar power satellite is the power relay satellite. It consists of a
beam transmitted from earth to a satellite, which reflects the beam to a receiving site on earth
that converts the beam back into electrical power.2 Some designs call for multiple independently
steerable reflectors so the satellite can transmit power to multiple locations. 3 Many consider
power relay satellites an incremental step to a full solar power satellite.4
Receiving Methods
Receiving methods for the beam involve the use of a rectenna. The rectenna intercepts the
beam of energy from the solar power satellite and converts it back into electricity.7 The rectenna
consists of long wires connected to rectifying diodes.8 Rectifying diodes convert RF energy into
electricity. Since the rectenna intercepts the beam and allows most sunlight to pass through, the
land beneath the rectenna still has a variety of available uses. One concept proposes to use the
land beneath the rectenna to grow crops or raise cattle.9 A rectenna may be located on earth,
another satellite, or on an aircraft.
Wireless Power Transmission
One technology, which makes solar power satellites possible and possesses a great deal of
potential for other applications, is wireless power transmission. Wireless power transmission is
the method by which solar power satellites beam power to a rectenna. Wireless power
transmission may occur with either a microwave or a laser beam. It involves transmitting
electrical power from one location to another without the use of wires. Most of the studies
focused on microwave wireless power transmission. Scientists have conducted several
demonstrations of wireless power transmissions. The first demonstration was by William C.
Brown. He proved the feasibility of the concept by powering a small helicopter with a
microwave beam.10 The next demonstration was by NASA in 1975. In this demonstration, they
transmitted 30 kilowatts of power over a distance of one mile.11
Conclusions
Solar power satellites are a means to produce electrical energy in space. They collect solar
power, turn it into electricity, convert the electricity into a beam of energy, and beam it to earth
or another satellite. The beam of energy could be a microwave or laser. Once the beam reaches
its destination, a rectenna converts it back into electricity and feeds it into the local power grid or
the electrical systems of the receiving satellite. A similar concept is the power relay satellite.
Electricity produced on earth is beamed into space, reflected by the satellite to some other
location on earth where a rectenna converts it back into electricity and feeds it into a power grid.
This technology has far reaching implications for the Air Force