WIRELESS POWER GENERATION USING SOLAR POWER
SATELLITE AND RECTANNA PART - 2
wireless transmission is the process that takes place in any system
where electrical energy is transmitted from a power source to an electrical
load, without interconnecting wires.It is employed in the cases where
instantaneous or continous energy transfer is needed, also where inter -
connecting wires are hazardous or impossible.
The various technologies that are available for wireless transmission are :
1) Tesla theory 2) Microwave power transmission called S.P.S 3)- Highly
efficient fiber lasers.
PRINCIPLE OF WIRELESS TRANSMISSION :
It is the combination of two discoveries (principles)
a) Electromagnet, a conducting wire wrapped around an iron core
WILLIAM STURGEN
b) The principle of E.M.I which says that a change magnetic field can
induce an electric current in the adjacent wire _ FARADAY
SOLAR POWER SATELLITE :
It is a method of power transmission in which solar power is converted
into microwaves through satellites called solar power satellites (S.P.S).
They are huge grid of solar panels and some additional circuitry to absorb
and convert solar energy to transmittable microwaves. They are built in earths
high orbit,which are renewable energy source, Zero emission and generates
no waste.
S.P.S consists of
a) Solar collector made of solar cells, which are unaffected by day/night cycle ,
weather or seasons.
b) Microwave antenna on the satellite aimed at earth.
c) Antenna occupying large area on earth to collect the power.
PRINCIPLE OF S.P.S :
Combining these two principles ( principle of electromagnet and principle of E.M.I)
NICHOLAS JOSEPH CALLAN was first to demonstrate transmission of electrical
energy without wires. His induction coil apparatus consists of two insulated
coils_primary and secondary windings both placed on a common iron core. This
method employed a minimum of 4 tuned circuits, 2 at transmitter and 2 at receiver.
By use of resonant coupling, wavelength produced is far lower making it no more
dangerous than beign exposed to radio waves.
SIZE AND POWER LEVELS :
Size of components is dictated by --- distance transmitter to receiver
----- Wavelength of radiation.
A battery connected to the primary would induce a voltage in the longer secondary
causing a spark to jump across its free terminals..
In an induction coil or electric transformer, this can have either an iron core or an
aircore; transmission of energy takes place by electromagnetic coupling through
a process of mutual induction. with this method it is possible to transmit and recieve
energy over considerable distance.
To transmit and collect that power satellites need to be around 50 - 100 sqkm of
collector area using 14% efficient MONOCRYSTALLINE SILICON SOLAR CELLS.
TRIPLE JUNCTION GALLIUM ARSENIDE solar cells with maximum efficiency of
40.7% could reduce collector area by 2- 3rds.
RECTENNA :
These are special type on antenna mounted on earths surface which convert
incoming microwave radiation into electricity and this can be into grids for storage
and future use.
Size is dictated by the distance from earth to geosynchronous orbit (22300 miles
= 35700Km), Wavelength of microwaves and laws of physics.
For best efficiency satellite antenna must be CIRCULAR between 1 - 1.5 km in
diameter and elliptical ground antenna around 14-110km.
OPERATION :
It consists of microwave oven magnetron with electrons to control the out power.
The output M.W power ranges from 50 - 200w at 2.45GHZ.
Co- axial cable connects output of microwave to a waveguide adapter and from
there to waveguide ferrite ciculator which protects microwave from reflected
power. The circulator connected to tuning wave guide impedance to antenna
input impedance.
waveguide antenna consists of 8 sections with 8 slots each. These 64 slots
radiate power uniformly through free space to the rectenna.
The rectenna or rectifying antenna receives transmitted power and converts
M.W power to direct d.c power.
Rectenna is G.a A.s schottky barrier diode that is impedance matched to
dipoles by L.P.F. there are 6 rectifying diodes connected to light bulbs
indicating the power is received.
ADVANTAGES OF WIRELESS TRANSMISSION :
A) Compensates additional storage facilities e.g. lakes behind dams.
B) Power production is enormous.
C) Need for an efficient, costly and capital intensive grid of cables, towers
and sub stations is eliminated.
D) Reduce the cost of electrical energy used by the consumer.
E) High transmission integrity and low loss,. Efficiency as high as 97%.
F) No transmission and distribution losses.
DISADVANTAGES AND REMEDIES :
A) Launch cost of space shuttle ($3000 & 5000 per pound).
B) Safety factor ( over 95% beam of microwaves fall on rectenna,remaining
will be dispersed all arouind causing harm to wild life as intensity of
microwaves are very high).
REMEDY : by use of resonant coupling the wavelength produced are far
more lower making it no more dangerous.
Writers.........NRUPEN.CH
SURYA TEJA.B
Summary by R.Krishnakumar B.E (IE)
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