03-05-2011, 02:40 PM
ABSTRACT
In the years following the OPEC oil embargo of 1973-74,
the United States aggressively researched alternative energy
options. Among those studied was the concept of Solar Power
Satellites - generating electricity in space from solar energy
on giant satellites and sending the energy to the Earth with
wireless power transmission. Comprehensive system
definition studies of the concept were performed under the
auspices of the Department of Energy and NASA from 1977
until 1980. The conclusion was that there was no technical
reason why the satellite system should not be developed and
that the potential benefits were very promising. However, the
studies were terminated because of concerns over the validity
of the cost estimates and the magnitude of the program.
Much has happened in the fifteen years since the studies
were terminated. The solar cell industry has matured; robotic
assembly, which has revolutionized the automobile industry,
is no longer just an idea but a practical reality; Space Shuttle
has proven the technology for reusable space transportation;
and wireless power transmission is being planned for many
applications. Maturing of the enabling technologies has
provided much of the infrastructure to support the
development of a commercial Solar Power Satellite program.
AI of this will reduce the cost by one to two orders of
magnitude so development can now be undertaken by industry
instead of relying on a massive government program.
Solar Space Industries was formed to accomplish this
goal. The basis of their development plan for Solar Power
Satellites is to build a Ground Test Installation that will
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duplicate, in small scale on the earth, all aspects of the power
generating and power transmission systems for the Solar
Power Satellite concept except for the space environment and
the range and size of the energy beam. Space operations issues
will be separated from the power generation fixation and
verifiled by testing using the NASA Space Station and Space
Shuttlle. Doing the developmental testing on the ground
instead of in space will result in a low cost program that can
be accomplished in a very short time.
Solar Space Industries' concept is to build a Ground Test
Installation that couples an existing 100 kW terrestrial solar
cell array, fumished by an interested utility, to a phased-array
wireless power transmitter based on the subarray developed by
William Brown and the Center for Space Power. Power will
be transmitted over a 1-1/4 mile range to a receiving antenna
(rectenna) and then fed into a commercial utility power grid.
The objective is to demonstrate the complete function of
the Solar Power Satellites, with the primary issue being the
validation of practical wireless power transmission. The key
features to demonstrate are: beam control, stability, steering,
efficiency, reliability, cost, and safety. This test will give the
utilities confidence in the efficiency, cost, environmental
safety, and operating characteristics of a Solar Power Satellite
with a very low-cost research program. This installation could
be in full operation within two years.
It is time for United States industry to initiate the
development of Solar Power Satellites and gain the benefits of
abundant, low-cost, nonpolluting energy they will bring.
SOL4R POWER SATELLITE CONCEPT
The concept of the Solar Power Satellite energy system is
to place giant satellites, covered with vast arrays of solar cells,
in geosynchronous orbit 22,300 miles above the Earth's
equator. Each satellite will be illuminated by sunlight 24 hours
a day for most of the year. Because of the 23" tilt of the
IEEE AES Systems Magazine, January 1996 33
Fig. 1. Components of the Solar Power Satellite System -
The Sun, The Satellite, The Wireless Power Transmitter,
and the Rectenna - Deliver Electricity
to Existing Distribution Grids
Earth’s axis, the satellites pass either above or below the
Earth’s shadow. It is only during the equinox period in the
spring and fall that they will pass through the shadow. They
will be shadowed for less than 1% of the time during the year.
The solar cells will convert sunlight to electricity, which will
then be changed to radio-frequency energy by a transmitting
antenna on the satellite and beamed to a receiver site on Earth.
It will be reconverted to electricity by the receiving antenna,
and the power would then be routed into our normal electric
distribution network for use here on the Earth. Figure 1
illustrates the concept.
capacity of a large Earth-based power plant. The great
advantage of placing the solar cells in space instead of on the
ground is that the energy is available 24 hours a day, and the
total solar energy available to the satellite is between four and
five times more than is available anywhere on Earth and 15
times more than the average location. Testing has
demonstrated that wireless energy transmission to the Earth
can be accomplished at very high efficiencies. Tests have also
shown that the energy density in the radio-frequency beam can
be limited to safe levels for all life forms. The concept is
simple; the technology exists.
Each satellite will have an output equivalent to the current
BACKGROUND
The concept of generating solar energy in space and
beaming it to Earth was first proposed by Dr. Peter Glaser of
A.D. Little in 1968. The idea was made possible by
development of practical wireless power transmission
demonstrated by Bill Brown of Raytheon in 1964. After the
OPEC oil embargo of 1973-74 NASA initiated studies of the
idea. The program, called Solar Power Satellites, was later
transferred to the Energy Research and Development Agency
(ERDA) as the first step of consolidating all government
energy efforts. Consolidation of responsibility was completed
when the Department of Energy was formed in 1977.
The Department of Energy developed a comprehensive
program that concentrated on four areas: 1) technical
feasibility; 2) environmental impact; 3) societal impact; and 4)
cost comparison. NASA was responsible for the technical
studies and DOE retained responsibility for the others as well
as overall program management. Funding for 3 years was
$19.5 million.
At the end of three years of studies all participating
organizations - the major aerospace companies and their
subcontractor teams, the Environmental Protection Agency
and their research scientists from universities and research
institutes, concerned citizen groups representing organizations
both supporting and opposing the concept, research scientists
from technology development companies, and economists -
assembled in Lincoln, Nebraska, in April of 1980 to report on
their findings. The conclusion of the conference was that there
was no technical reason why the satellite system should not be
developed and that the potential benefits were very promising.
However, by 1980 the oil crisis of 1973-74 appeared to be
over and nearly forgotten. Concerns over the size and cost of
the program, opposition to the concept from the established
energy industry who saw it as a threat to their future, and
opposition of the Carter administration to large programs,
resulted in the order to stop all further work in the summer
of 1980.
Since that time there has been no significant organized
system development work on the concept in the United States.
The public has forgotten that there is an energy system that
could replace oil, coal, and nuclear power; an energy system
that would have unlimited capacity, be environmentally clean,
and, in time, would result in energy costs much below those of
fossil fuels or nuclear. With Solar Power Satellites, the cost of
electricity by the year 2050 would be between 15 and 70 times
less than with fossil fuels or nuclear.
Development of enabling technologies, such as solar cells
and wireless energy transmission, has continued for other
applications, making the concept even more technically and
financially sound today. Also during this time system
definition and design has been initiated in foreign countries.
Japan is now committed to the development of Solar Power
Satellites with the ultimate goal of producing 30% of global
energy needs by 2040, most of it for export.
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