Wireless Power Transmission – A Next     Generation Power Transmission System

INTRODUCTION

One of the major issue in power system is the losses occurs during

the transmission and distribution of electrical power. As the

demand increases day by day, the power generation increases and

the power loss is also increased. The major amount of power loss

occurs during transmission and distribution. The percentage of loss

of power during transmission and distribution is approximated as

26%. The main reason for power loss during transmission and

distribution is the resistance of wires used for grid. The efficiency

of power transmission can be improved to certain level by using

high strength composite over head conductors and underground

cables that use high temperature super conductor. But, the

transmission is still inefficient. According to the World Resources

Institute (WRI), India’s electricity grid has the highest

transmission and distribution losses in the world – a whopping

27%. Numbers published by various Indian government agencies

put that number at 30%, 40% and greater than 40%. This is

attributed to technical losses (grid’s inefficiencies) and theft [1].

Any problem can be solved by state–of-the-art technology. The

above discussed problem can be solved by choose an alternative

option for power transmission which could provide much higher

efficiency, low transmission cost and avoid power theft.

Microwave Power Transmission is one of the promising

technologies and may be the righteous alternative for efficient

power transmission.

WIRELESS POWER TRANSMISSION

Nikola Tesla he is who invented radio and shown us he is indeed
the “Father of Wireless”. Nikola Tesla is the one who first
conceived
the idea Wireless Power Transmission and demonstrated “the
transmission of electrical energy without wires" that depends upon
electrical conductivity as early as 1891. In 1893, Tesla
demonstrated the illumination of vacuum bulbs without using
wires for power transmission at the World Columbian Exposition
in Chicago. The Wardenclyffe tower shown in Figure 1 was
designed and constructed by Tesla mainly for wireless
transmission of electrical power rather than telegraphy
In 1904, an airship ship motor of 0.1 horsepower is driven by
transmitting power through space from a distance of least 100 feet
[4]. In 1961, Brown published the first paper proposing microwave
energy for power transmission, and in 1964 he demonstrated a
microwave-powered model helicopter that received all the power
needed for flight from a microwave beam at 2.45 GHz [5] from
the range of 2.4GHz – 2.5 GHz frequency band which is reserved

for Industrial, Scientific, and Medical (ISM) applications.

Experiments in power transmission without wires in the range of

tens of kilowatts have been performed at Goldstone in California in

1975  and at Grand Bassin on Reunion Island in 1997 . The

world’s first MPT experiment in the ionosphere called the MINIX

(Microwave Ionosphere Non-linear Interaction Experiment) rocket

experiment is demonstrated in 1983 at Japan [8]. Similarly, the

world’s first fuel free airplane powered by microwave energy from

ground was reported in 1987 at Canada. This system is called

SHARP (Stationary High – Altitude Relay Platform) .

In 2003, Dryden Flight Research Centre of NASA demonstrated a

laser powered model airplane indoors. Japan proposed wireless

charging of electric motor vehicles by Microwave Power

Transmission in 2004. Powercast, a new company introduced

wireless power transfer technology using RF energy at the 2007

Consumer Electronics Show. A physics research group, led by

Prof. Marin Soljačić, at the Massachusetts Institute of technology

(MIT) demonstrated wireless powering of a 60W light bulb with

40% efficiency at a 2m (7ft) distance using two 60cm-diameter

coils in 20. Recently in 2008, Intel reproduced the MIT

group's experiment by wirelessly powering a light bulb with 75%

efficiency at a shorter distance.

Advantages

Wireless Power Transmission system would completely eliminates
the existing high-tension power transmission line cables, towers
and sub stations between the generating station and consumers and
facilitates the interconnection of electrical generation plants on a
global scale. It has more freedom of choice of both receiver and
transmitters. Even mobile transmitters and receivers can be chosen
for the WPT system. The cost of transmission and distribution
become less and the cost of electrical energy for the consumer also
would be reduced. The power could be transmitted to the places
where the wired transmission is not possible. Loss of transmission
is negligible level in the Wireless Power Transmission; therefore,
the efficiency of this method is very much higher than the wired
transmission. Power is available at the rectenna as long as the WPT
is operating. The power failure due to short circuit and fault on
cables would never exist in the transmission and power theft would
be not possible at all.
                       -ambuj

REFERENCES

[1]
http://cleantechindia.wordpress.com/2008/07/16/indias-
electricity-transmission-and-distribution-losses/
[2] Nikola Tesla, My Inventions, Ben Johnston, Ed., Austin, Hart
Brothers, p. 91,1982.
[3] Nikola Tesla, “The Transmission of Electrical Energy Without
Wires as a Means for Furthering Peace,” Electrical World and
Engineer. Jan. 7, p. 21, 1905.
[4] The Electrician (London), 1904).
[5] W.C. Brown, J.R. Mims and N.I. Heenan, “An Experimental
Microwave-Powered Helicopter”, 965 IEEE International
Convention Record, Vol. 13, Part 5, pp.225-235.

India need the other kind of solar power..

our country is very reach in the source of sun light.And this is one of the most positive and golden opportunity for we all Indians to use it.In our country there is a lot solar power plant but we haven't solar thermal plant.This time we are using solar thermal is only as a solar water heater,but it is a also great scope in to use it as a solar thermal power station for generating power.

Solar-thermal power stations have several advantages over solar-photovoltaic projects. They are typically built on a much larger scale, and historically their costs have been much lower. Compared with other renewable sources of energy, they are probably best able to match a utility's electrical load, says Nathaniel Bullard of New Energy Finance, a research firm. They work best when it is hottest and demand is greatest. And the heat they generate can be stored, so the output of a solar-thermal plant does not fluctuate as wildly as that of a photovoltaic system. Moreover, since they use a turbine to generate electricity from heat, most solar-thermal plants can be easily and inexpensively supplemented with natural-gas boilers, enabling them to perform as reliably as a fossil-fuel power plant

Storage and hybrids

Both power-tower and parabolic-trough systems can store thermal energy in the form of hot, molten salt. It is then possible to generate steam, and thus electricity, even when the sun is not shining. Solar-thermal plants without storage can operate about 30% of the year; but with storage that number could climb to 70% or higher. Unfortunately storage is expensive, and is only economical when regulators provide incentives. In Spain, for example, producers of solar-thermal power receive a guaranteed feed-in tariff. That makes it particularly appealing for Spanish plants to have storage capabilities, to maximise their ability to sell electricity to utilities. In America the main incentives for solar-thermal projects are a 30% investment-tax credit or an equivalent cash grant. As a result, American plants have to be built more cheaply in order to make a profit, and thus typically do not include storage.

Power from a parabolaEyevine

A cheaper alternative to storage is hybridisation. All the original Luz plants also have natural-gas boilers that can generate steam when the sun is not shining. Because solar-thermal plants have a power block and turbine already in place, the extra cost is marginal. Hybridisation could also be done the other way around, by using steam generated from solar-thermal collectors to help drive the turbines at existing coal or gas plants. The Electric Power Research Institute, based in Palo Alto, is studying the feasibility of this approach as a means of reducing fuel costs and emissions at existing power stations.

In addition to parabolic troughs and power-towers there is also a third solar-thermal technology, which combines curved, dish-shaped mirrors with heat engines. In a dish-engine design, the mirrors concentrate sunlight to generate heat, which then typically powers a Stirling engine—a machine that converts heat into mechanical energy by compressing and expanding a fixed quantity of gas. The change in pressure drives the engine's pistons, which drive a shaft that turns a generator to produce electricity.

Although they are highly efficient, Stirling engines have seen little practical use since their invention nearly two centuries ago, and so far there are no commercial solar-thermal systems that use this approach. Critics of the technology say it involves too many moving parts, making it more complex and expensive to operate and maintain than competing technologies. Stirling Energy Systems, based in Phoenix, Arizona, hopes to prove the doubters wrong. It has signed two large power-purchase agreements, for up to 1,750MW, and plans to fulfil them using dish-engine systems built in conjunction with its sister company, Tessera Solar. Both projects are due to start construction as early as 2010.

-  thankyou ambuj