1. Presented by:
• D.ADHARVANA
• IV ECE
10F81A0461
• GOKULA KRISHNA
COLLEGE OF
ENGINEERING
• AP

2.  This paper reports on the futuristic advances in power
transmission through microwave. A Space Power Satellite
(SPS) orbiting round the earth traps solar energy and
generates electric power using photovoltaic cells of sizable
area. SPS transmits the generated power via a microwave
beam to the receiving Rectenna site on earth.
 A RECTENNA (RECtifying anTENNA) comprises of a mesh of
dipoles and diodes for absorbing microwave energy from a
transmitter and converts it into electric power. We can in
fact directly convert solar energy into electrical energy with
the use of solar cells, but this process will be affected by
day/night cycles,weather, and seasons. We are aware of the
fact that light is an electromagnetic wave. Light rays never
diffuse in space & if by any means these rays can be
transmitted from space to earth then it will be a perfect
solution for our desired need of 24 hrs power supplies.
 This paper presents the concept & evolution of satellite
power system, SPS2000 (a research work by ISAS) and the
impact of Microwave Power Transmission (MPT) on space
plasma. In near future conventional power sources cannot
meet total power demand, for which SPS is a best solution.

3.  WIRELESS POWER TRANSMISSION SYSTEM(WPT) BACKGROUND
 TECHNICAL SEESION ON SPS
 BASIC STRUCTURE OF SOLAR POWER SATELLITE
 TYPES OF WPT
 SOLAR ENERGY CONVERSION
 SPACE CRAFT SIZING
 LEO INSTEAD OF GEO
 EARTH BASED INFRA STRUCTURE(RECTENNA)
 SPS 2000
 CONFIGURATION OF SPECTANNA
 ADVANTAGES
 FUTURE SCOPE

4. o The vision of achieving WPT on a global scale was proposed over 100 years
ago .when Nikola Tesla first started experiments with WPT, culminating
with the construction of a tower for WPT on Long Island, New York, in the
early 1900s.Tesla's objective was to develop the technology for
transmitting electricity to anywhere in the world without wires. He filed
several patents describing wireless power transmitters and receivers.
However, his knowledge of electrical phenomena was largely empirical and
he did not achieve his objective of WPT, although he was awarded the
patent for wireless radio in 1940.
o The development of WPT was not effectively pursued until the 1960s
when the U.S. Air Force funded the development of a microwave-powered
helicopter platform. A successful demonstration of a microwave beam-
riding helicopter was performed in 1965. This demonstration proved that a
WPT system could be constructed and that effective microwave generators
and receivers could be developed for efficient conversion of microwaves
into DC electricity.
o The growing interest in solar energy conversion methods and solar energy
applications in the 1960s and the limitations for producing cost-effective
base load. power caused by adverse weather conditions and diurnal
changes led to the solar power satellite concept in 1968 as a means to
convert solar energy with solar cell arrays into electricity and feed it to a
microwave generator forming part of a planar, phased-array antenna.
o In geosynchronous orbit, the antenna would direct a microwave beam of
very low power density precisely to one or more receiving antennas at
desired locations on Earth. At a receiving antenna, the microwave energy
would be safely and very efficiently reconvened into electricity and then
transmitted to users.

5.  The first technical session on solar power satellites
(SPS) was held in 1970 at the International
Microwave Power Institute Symposium at which
representatives of Japan, European countries, and
the former Soviet Union were present.
 Based on preliminary studies, a plan for an SPS
program was prepared by an NSF/NASA panel in
1972 and the first feasibility study of SPS was
completed for NASA/Lewis Research Center in
1974. Shortly after the "oil shock" of October 1973,
Japan staned to implement the Sunshine Plan to
develop renewable energy sources.
 Japan's Plan included, as a long term objective,
the development of SPS. Back in the U.S. in 1975, a
successful demonstration of microwave wireless
power transmissions was performed at the NASA
Deep Space Antenna facility at Goldstone,
California. In this demonstration of point-to-point
WPT, 30 kW of microwaves were beamed over a
distance of one mile to a receiving antenna.
 Microwaves were converted directly into DC at an
average efficiency of 82%, confounding critics who
claimed that such high conversion efficiencies
could not be achieved.

6. The concept of the Solar Power Satellite (SPS) is very simple. It is
a gigantic satellite designed as an electric power plant orbiting in
the Geostationary Earth Orbit (GEO) as shown in Fig. 1. and fig 2.
It consists of mainly three segments.
1) Solar energy collector to convert the solar energy into DC
(direct current) electricity
2) DC-to-microwave converter,
3) Large antenna array to beam the microwave power to the
ground.
The solar collector can be either photovoltaic cells or a solar
thermal turbine.
Fig. 1 Solar collectors

7.  The DC-to-microwave converter of the SPS can be
either a microwave tube system or a semiconductor
system, or their combination. The third segment is a
gigantic antenna array. The SPS system has that
advantage of producing electricity with much higher
efficiency than a photovoltaic system on the ground.
 Since SPS is placed in space in GEO, there is no
atmospheric absorption, the solar input power is
about 30% higher density than the ground solar
power density, and power is available 24 hours a day
without being affected by weather conditions.
 It is confirmed that the eclipses would not cause a
problem on a grid because their occurrences are
precisely predictable.

8. Two types of WPT:
1) Ground based power transmission
2) Space based power transmission
But Space-based power transmission is preferred over
Ground-based power transmission.
Ground is (obviously) cheaper per noontime watt, but:
• Space gets full power 24 hours a day
.3X or more Watt-hours per day per peak watt
.No storage required for nighttime power
• Space gets full power 7 days a week – no cloudy days
• Space gets full power 52 weeks a year
– No long winter nights, no storms, no cloudy seasons
• Space delivers power where it’s needed
– Best ground solar sites (deserts) are rarely near users
• Space takes up less, well, space
– Rectennas are 1/3 to 1/10 the area of ground arrays
– Rectennas can share land with farming or other uses

9. Two basic methods of converting sunlight to electricity
have been studied: photovoltaic (PV) conversion, and
solar dynamic (SD) conversion.
Most analyses of solar power satellites have focused on
photovoltaic conversion (commonly known as “solar
cells”). Photovoltaic conversion uses semiconductor
cells (e.g., silicon or gallium arsenide) to directly
convert photons into electrical power via a quantum
mechanical mechanism.
 Photovoltaic cells are not perfect in practice, as
material purity and processing issues during production
affect performance; each has been progressively
improved for some decades.
 Some new, thin-film approaches are less efficient
(about 20% vs. 35% for best in class in each case), but
are much less expensive and generally lighter.
 In an SPS implementation, photovoltaic cells will likely
be rather different from the glass-pane protected solar
cell panels familiar to many from current terrestrial
use, since they will be optimized for weight, and will be
designed to be tolerant to the space radiation
environment, but will not need to be encapsulated
against corrosion by the elements.
 They may not require the structural support required
for terrestrial use, where the considerable gravity
loading imposes structural requirements on terrestrial
implementations.

10.  The size of an SPS will be dominated by two factors. The size
of the collecting apparatus (e.g. panels, mirrors, etc) and the
size of the transmitting antenna which in part depends on the
distance to the receiving antenna. The distance from Earth to
geostationary orbit (22,300miles, 35,700 km), the chosen
wavelength of the microwaves, and the laws of
physics, specifically the Rayleigh Criterion or Diffraction
limit, used in standard RF (Radiofrequency) antenna design
will all be factors.
It has been suggested that, for best efficiency, the satellite
antenna should be circular and the microwave wavelength
should be about 1 kilometers in diameter or larger; the ground
antenna (rectenna) should be elliptical, 10 km wide, and a
length that makes the rectenna appear circular. Smaller
antennas would result in increased losses to diffraction/side
lobes.
For the desired (23mW/cm²) microwave intensity these
antennas could transfer between 5and 10 gigawatts of power.
To be most cost effective, the system should operate at
maximum capacity.
And, to collect and convert that much power, the satellite
would require between 50 and 100 square kilometers of
collector area (if readily available ~14% efficient
monocrystalline silicon solarcells were deployed).
 State of the art (currently, quite expensive, triple junction
gallium arsenide) solar cells with a maximum efficiency of
40.7% could reduce the necessary
collector area by two thirds, but would not necessarily give
overall lower costs for various reasons.

11.  A collection of LEO (Low Earth Orbit) space power stations has
been proposed as a precursor to GEO (Geostationary Orbit) space
power beaming systems.
 There would be advantages
• much shorter energy transmission path lengths allowing smaller
antenna sizes
• lower cost to orbit
• energy delivery to much of the Earth's surface.
• assuming appropriate antennas are available, etc.
 Ultimately, because full engineering feasibility studies have not
been conducted, it is not known whether this approach would be
an improvement over a GEO installation.
Fig. 4 Solar power satellite

12. RECTifying anTENNA rectifies received
microwaves into DC current.
 A rectenna comprises of a mesh of dipoles and
diodes for absorbing microwave energy from a
transmitter and converting it into electric
power.
Its elements are usually arranged in a mesh
pattern, giving it a distinct appearance from
most antenna. A simple rectenna can be
constructed from a Schottky diode placed
between antenna dipoles as shown in Fig. 1.
The diode rectifies the current induced in the
antenna by the microwaves.
 Rectenna are highly efficient at converting
microwave energy to electricity. In laboratory
environments, efficiencies above 90% have been
observed with regularity. In future rectennas
will be used to generate large-scale power from
microwave beams delivered from orbiting SPS
satellites.

13.  SPS2000 is a model of solar power satellites with microwave
power output of 10 MW, which was proposed by the SPS working
group of the Institute of Space and Astronautically Science (ISAS).
 The primary objective of SPS2000 research is to show whether
SPS could be realized with the present technology and to find out
technical problems.

14.  The general configuration of SPS2000 has the shape like a
triangular prism as shown in Figure 2.
 The power transmission antenna, spacetenna, is built on
the bottom surface facing to the earth, and the other two
surfaces are used to deploy the solar panels.
 SPS2000 moves on an equatorial LEO at an altitude of
1100km.
 A frequency of 2.45 GHz is assigned to transmit power to
the earth.
 SPS2000 can serve exclusively the equatorial
zone, especially benefiting geographically isolated lands
in developing nations.

15. The Spacetenna has a square shape whose dimension is 132 meters by
132 meters and which is regularly filled with 1936 segments of sub
array. The sub array is considered to be a unit of phase control and
also a square shape whose edges are 3 meters. It contains 1320 units
of cavity-backed slot antenna element and DC-RF circuit. Therefore,
there will be about 2.6 million antenna elements in the spacetenna.
 The spacetenna is composed of pilot signal receiving antennas
followed by detectors finding out the location of the rectenna on the
earth, power transmission antenna elements and phase control
systems.
 The left and right hand sides in Fig.4 correspond to parts of power
transmission and direction detection, respectively.
 The antenna elements receiving the pilot signal have a polarization
perpendicular to the antenna elements used in the power
transmission so as to reduce effectively interactions between both
antenna elements.

16. The SPS concept is attractive because space
has several major advantages over the Earth's
surface for the collection of solar power.
 The SPS would be used in 24hrs in all
seasons
This characteristic of SPS based power
generation systems to avoid the expensive
storage facilities.
 A SPS will have non polluting consequences
of fossil fuel systems, nor the ecological
problems resulting from many renewable or
low impact power generation systems
Economically, an SPS deployment project
would create many new jobs and contract
opportunities for industry.
 Space solar power would be the only means
of acquiring direct solar energy to supplement
the burning of fossil fuels or nuclear energy
sources under the most extreme conditions of
a global catastrophic volcanic winter

17. 1. To store electricity during off peak
demand hours.
2. The frequency of beamed
radiation is planned to be at 2.45
GHz and this frequency is used by
communication satellites also.
3. Minimizing the entire size as it will
be massive.
4. To reduce high initial cost and
time for construction
5. Reduce radiation hazards
associated with the system.

18. In the future Rectenna stands as a milestone
among non conventional energy resources. This
technology is more reliable than ground based
solar power. In order for SPS to become a reality
several things have to happen:
oCheaper launch prices
oInvolvement of the private sector
The economic case for a solar power satellite is
most compelling if it can generate power that
sells at peak, rather than average, price.
 Several new designs for solar power satellites
were considered, in an attempt to maximize the
amount of power produced at peak rates.
 This study has given researchers a remarkable
insight into uncertain future of development of
power from space.