wireless power transfer

1. presented by:-

2. WHAT IS WPT???
WPT vs. TELECOMMUNICATION.
SPS TRANSMISSION AND ITS ELLEMENTS.
POWER GENERATOR.
MICROWAVE CONVERTOR
RECEIVING ANTENNA.
 WHY TO USE SPS???
CONCLUSION.

3. The transmission of energy from one place to another
without using wires.
Conventional energy transfer is using wires.
But the wireless transmission is made possible by using
various technologies.
This phenomena is also known as ‘Witricity’.

4.  It is known that electromagnetic energy also associated with
the propagation of the electromagnetic waves. We can
use theoretically all electromagnetic waves for a wireless
power transmission (WPT).
 The difference between the WPT and communication
systems is only efficiency.
 The Maxwell’s Equations indicate that the electromagnetic
field and its power diffuse to all directions.
 The energy which we transmit in the communication system,
is diffused to all directions.
 Although the received power is enough for a transmission of
information, but the efficiency to receiver is quiet low for
WPT system.

5. ► In this topic of interest we have represented the concept
of power transmission without using the wires i.e. power
transmission via solar power satellite(SPS) using microwaves as
transmitting media.
► solar power satellite power transmission system
essentially consists of three elements:-
• A means of collecting solar power in space, for example via
solar concentrators, , solar cell 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
microwave antenna (rectenna)

7. In LEO(low earth orbit), a 11,00 Km altitude equatorial
orbit will be used. This choice minimizes the transmission
cost and the distance of power transmission from space
If it was in GEO(geosynchronous orbit) that is 35,800
Km from the earth ,the transmitting antenna would have to
be 40 times larger than LEO one- or else the receiving
station would have to be 40 times larger.

8. Sun light
Gigantic solar array
panel
DC output
Microwave converter
circuit
Semiconductor
amplifier or
magnetron
Transmitting antenna
Transmission
channel
Receiving
antenna
low pass
filter
amplifier
MW to DC
convertor
DC/AC
convertor

9. There are two methods to accumulate and convert Solar
energy to Electrical energy.
Photovoltaic panel array :- These panels are mostly made up of gallium
or silicon arsenide which directly convert photons into DC O/P. To design
these arrays, beside using ordinary solar panels, approach to thin film
panels is much more economic as per transportation as well as generation
efficiency issue. 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.
Solar thermal plant :- This is nothing but a thermal plant established in
geo axis. Sun light being concentrated via systematically arranged mirror
structure, to the boiler heats the water and the generated steam runs the
turbine which in turn rotate the synchronous generator and generates AC,
which is then converted into DC.

10. There are two types of microwave generators.
1. Microwave Tube
2. Semiconductor Amplifier
3. Klystron
Microwave tube:- It has electric characteristics contrary to
Semiconductor Amplifier.The microwave tube, such as a cooker-type
magnetron, can generate and amplify high power microwave (over kW)
with a high voltage (over kV) imposed. Especially magnetron is very
economical.
 Magnetron is a crossed field tube in which E X B forces acts over
electrons emitted from the cathode to take cyclonical path to the
anode. The magnetron is suitable device for the MPT because of
high efficiency and low cost .

11. Semiconductor devices:- The semiconductor amplifier generate low
power microwave (below 100W) with a low voltage (below fifteen volt)
imposed. It is still expensive currently. the semiconductor device are Si for
lower frequency below a few GHz and GaAs for higher frequency.
We have to choose tube/semiconductor devices by case for the MPT
system.
Although there are some discussions concerning generation tube has
higher efficiency (over 70%) and the semiconductor has lower efficiency
(below 50%) in general.
klystron :- In it a high velocity electron beam is formed, focused and
send down a glass tube to a collector electrode which is at high positive
potential with respect to the cathode. The overall efficiency is 83%. The
microwave power density at the transmitting array will be 1 kW/m² for a
typical 1 GW SPS with a transmitting antenna aperture of 1 km diameter.
If we use 2.45 GHz for MPT, the number of antenna elements per square
meter is on the order of 100.

12. Space antenna is a triangular prism with a length of 800
m and sides of 100 m.
The transmitting antenna on the horizontal under surface
faces the earth, and the other two sides of the prism carry
solar arrays.
The faces of prism are embedded with photovoltaic cells
.These cells would convert solar energy into electricity,
which in turn power onboard , Microwave Generator.
The microwave thus produced travels through atmosphere
& collected by RECTENNAS on earth.

14. Rectenna is the microwave to
dc converting device and is
mainly composed of a receiving
antenna and a rectifying circuit.
It consists of a receiving
antenna, an input low pass
filter, a rectifying circuit and an
output smoothing filter. The
input filter is needed to
suppress radiation of high
harmonics that are generated by
the non linear characteristics of
rectifying circuit. Because it is a
highly non linear circuit,
harmonic power levels must be
suppressed.

15. More intense sunlight.
Unlimited energy resource.
Energy delivered anywhere in the world.
Zero fuel cost.
Zero CO2 emission – environment safe.
Waste heat is radiated back into space.
No air or water pollution is created during the
generation.
Concept is simpler than the other most power
systems here on the earth.

16.  …..
 The area which is being used to construct a
solar power plant on earth can be utilized
for other purposes.
 Solar radiation can be more efficiently
collected.
 The full solar irradiation would be available
at all times expect when the sun is eclipsed
by the earth. Thus about five times energy
could be collected, compared with the best
terrestrial sites.

17. The power density would be uninterrupted by darkness,
clouds, or precipitation, which are the problems encountered
with earth based solar arrays.

18.  It is effected by solar flare and micrometeoroid.
The entire structure is massive. High cost and require much
time for construction.
 Radiation(i.e. solar flashes) hazards associated with the
system.
 Risks involved with malfunction .
High power microwave source and high gain antenna can be
used to deliver an intense burst of energy to a target and thus
used as a weapon.

19.  The SPS will be a central attraction of space and energy
technology in coming decades. However, large scale retro
directive power transmission has not yet been proven and
needs further development. Another important area of
technological development will be the reduction of the size
and weight of individual elements in the space section of SPS.
Large-scale transportation and robotics for the construction of
large-scale structures in space include the other major fields of
technologies requiring further developments.
 The electromagnetic energy is a tool to improve the quality
of life for mankind. It is not a pollutant but more aptly, a man
made extension of the naturally generated electromagnetic
spectrum that provides heat and light for our sustenance.
From this view point, the SPS is merely a down frequency
converter from the visible spectrum to microwaves.