September 4, 2010

HVDC projects under service in INDIA

High Voltage Direct Current transmission - HVDC

One of the most exciting new technical development in electric power system in the last three decades has been “High Voltage Direct Current transmission”. From the
first of HVDC links to the recent, the voltage has increased from 100 KV to 800 KV, the rated power from 20 MW to 6300 MW and the distance from 96 km to 1370 km.
Preceding and accompanying this rapid growth of Direct Current Transmission were developments in High Voltage, High power valves, in control and protection system, in DC cables and in insulation for overhead DC lines.

In India three HVDC projects are in operation.

(i) The Rihand-Delhi HVDC transmission project having 1500 MW capacity
and 500 KV DC voltage is the first commercial long distance DC
transmission project in India.
For pics click here

(ii) Vindhyachal 2x250 MW Back to back DC converter station which
asychronously connect the Northern and Western regions for exchange of
power.

(iii) The Nation HVDC experimental line project, which links Lower Sileru in
A.P. to Barsoor in M.P. Phase 1 of this project is capable of transmitting
100 MW at 100 KV DC.


July 23, 2010

Portable hydroelectric generator.......

 
This portable new product promises energy on the go – and we don’t mean a Power Bar. Bourne Energy’s Backpack Power Plant is a hydroelectric generator that you can strap on just like a bookbag. It can produce electricity from any pretty much any stream of water, meaning that it’s quite a bit more useful than a Power Bar to boot.
The BPP is 3 feet long and weighs less than 30 pounds. It is self-contained and holds its own integrated power control, cooling and sensor systems. The generator is quite adaptable, and each unit generates up to 500 watts per unit. Each generator can work by itself, or can be tied to other units to generate up to 30 kW of power, which is pretty good power output for the $3,000 price tag. 

For more pics click here.......
  
Read more......

July 22, 2010

Generating electricity from body movements.....

Nanogenerators
"There is a lot of mechanical energy available in our environment," said Zhong Lin Wang, a Regents Professor in the School of Materials Science and Engineering at the Georgia Institute of Technology.
"Our nanogenerators can convert this mechanical energy to electrical energy. This could potentially open up a lot of possibilities for the future of nanotechnology."
Nanotechnology researchers have proposed and developed a broad range of nanoscale devices, but their use has been limited by the sources of energy available to power them. Conventional batteries make the nanoscale systems too large, and the toxic contents of batteries limit their use in the body. Other potential power sources also suffer from significant drawbacks.
The nanogenerators developed by Wang and graduate student Jinhui Song use the very small piezoelectric discharges created when zinc oxide nanowires are bent and then released. By building interconnected arrays containing millions of such wires, Wang believes he can produce enough current to power nanoscale devices.
To study the effect, the researchers grew arrays of zinc oxide nanowires, then used an atomic-force microscope tip to deflect individual wires. As a wire was contacted and deflected by the tip, stretching on one side of the structure and compression on the other side created a charge separation -- positive on the stretched side and negative on the compressed side -- due to the piezoelectric effect.
The charges were preserved in the nanowire because a Schottky barrier was formed between the AFM tip and the nanowire. The coupling between semiconducting and piezoelectric properties resulted in the charging and discharging process when the tip scanned across the nanowire, Wang explained.
When the tip lost contact with the wire, the strain was released -- and the researchers measured an electrical current. After the strain release, the nanowire vibrated through many cycles, but the electrical discharge was measured only at the instant when the strain was released.
The researchers grew the nanowire arrays using a standard vapor-liquid-solid process in a small tube furnace. First, gold nanoparticles were deposited onto a sapphire substrate placed in one end of the furnace. An argon carrier gas was then flowed into the furnace as zinc oxide powder was heated. The nanowires grew beneath the gold nanoparticles, which serve as catalysts.
The resulting arrays contained vertically-aligned nanowires that ranged from 200 to 500 nanometers in length and 20 to 40 nanometers in diameter. The wires grew approximately 100 nanometers apart, as determined by the placement of the gold nanoparticles.
A film of zinc oxide also grew between the wires on the substrate surface, creating an electrical connection between the wires. To that conductive substrate, the researchers attached an electrode for measuring current flow.
Though attractive for use inside the body because zinc oxide is non-toxic, the nanogenerators could also be used wherever mechanical energy -- hydraulic motion of seawater, wind or the motion of a foot inside a shoe -- is available. The nanowires can be grown not only on crystal substrates, but also on polymer-based films. Use of flexible polymer substrates could one day allow portable devices to be powered by the movement of their users.
 "This could be beneficial to soldiers in the field, who now depend on batteries to power their electrical equipment. As long as the soldiers were moving, they could generate electricity."
Current could also be produced by placing the nanowire arrays into fields of acoustic or ultrasonic energy. Though they are ceramic materials, the nanowires can bend as much as 50 degrees without breaking.
The next step in the research will be to maximize the power produced by an array of the new nanogenerators. Wang estimates that they can convert as much as 30 percent of the input mechanical energy into electrical energy for a single cycle of vibration. That could allow a nanowire array just 10 microns square to power a single nanoscale device -- if all the power generated by the nanowire array can be successfully collected.
"Our bodies are good at converting chemical energy from glucose into the mechanical energy of our muscles," Wang noted. "These nanogenerators can take that mechanical energy and convert it to electrical energy for powering devices inside the body. This could open up tremendous possibilities for self-powered implantable medical devices."
For pics....

Portals and sites of placement papers

http://www.yuvajobs.com/paper.asp

http://coders2020.com/placement_papers


http://www.geekinterview.com/global-interview-questions

http://www.chetanasinterview.com/


http://www.freshersworld.com/


http://www.xomba.com/www_placementpapers_net_india_s_largest_collection_placement_papers_and_jobs_freshers_website

http://www.freshershome.com/


https://cuportal.coventry.ac.uk/default.aspx

http://www.freshersindia.com/

http://www.careerkhazana.com/

Important portals and job sites........

http://careers.ieee.org/

icerecruit.com

engcen.com

justengineers.net

stantec.com

http://www.engnetglobal.com/

http://www.thecareerengineer.com/

http://www.engineerjobs.co.uk/


http://www.engineers-international.com/electrical_engineering_jobs.html

http://www.engineerlive.com/


http://www.engineeringtalk.com/


http://www.interec.net/

http://www.engineeringjobs.com/

http://www.engcom.net/


http://www.engineeringexchange.com/

http://www.nspe.org/index.html


http://www.engineeringcareersonline.com/

July 18, 2010

Device that converts motion into electricity

Dynamo

Dynamo Electric Machine [End View, Partly Section] (U.S. Patent 284,110)
The Dynamo was the first electrical generator capable of delivering power for industry. The dynamo uses electromagnetic principles to convert mechanical rotation into a pulsing direct electric current through the use of a commutator. The first dynamo was built by Hippolyte Pixii in 1832.
Through a series of accidental discoveries, the dynamo became the source of many later inventions, including the DC electric motor, the AC alternator, the AC synchronous motor, and the rotary converter.
A dynamo machine consists of a stationary structure, which provides a constant magnetic field, and a set of rotating windings which turn within that field. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field provided by one or more electromagnets, which are usually called field coils.
Large power generation dynamos are now rarely seen due to the now nearly universal use of alternating current for power distribution and solid state electronic AC to DC power conversion. But before the principles of AC were discovered, very large direct-current dynamos were the only means of power generation and distribution. Now power generation dynamos are mostly a curiosity.

Model,Technical papers,Interview tips.......

For BARC admission procedure and interview tips.......

For technical and iterview tips related to BHEL.......

BEL placement paper.........

BHEL recruitment examination papers.......


HAL Placement Paper & Pattern......

NTPC previous papers.....

ISRO Scientist/Engineer Exam Papers........

RRB papers......
For more information related to technical papers send me a mail.....