Scientists develop solar cells with a ‘twist’

Sliced Silicon Chips, 100 Times Thinner Than A Wafer, Can Be Used As Window Tints In Cars, Buildings

Chicago: US researchers have found a way to make efficient silicon-based solar cells that are flexible enough to be rolled around a pencil and transparent enough to be used to tint windows on buildings or cars.

The finding, reported on Sunday in the journal Nature Materials, offers a new way to process conventional silicon by slicing the brittle wafers into ultrathin bits and carefully transferring them onto a flexible surface.

“We can make it thin enough that we can put it on plastic to make a rollable system. You can make it gray in the form of a film that could be added to architectural glass,” said John Rogers of the University of Illinois.

“It opens up spaces on the fronts of buildings as opportunities for solar energy,” Rogers said. Solar cells, which convert solar energy into electricity, are in high demand because of higher oil prices and concerns over climate change.

The new technology could be used on car windows, generating enough electricity to power the GPS or air conditioning.

Many companies, including Japanese consumer electronics maker Sharp Corp and Germany’s Q-Cells are making thinfilm solar cells, but they typically are less efficient at converting solar energy into electricity than conventional cells.

Rogers said his technology uses conventional single crystal silicon. “It’s robust. It’s highly efficient. But in its current form, it’s rigid and fragile,” he said.

Rogers’ team uses a special etching method that slices chips off the surface of a bulk silicon wafer. The sliced chips are 10 to 100 times thinner than the wafer, and the size can be adapted to the application.

Once sliced, a device picks up the bits of silicon chips “like a rubber stamp” and transfers them to a new surface material, Rogers said. “These silicon solar cells become like a solid ink pad for that rubber stamp. The surface of the wafers after we’ve done this slicing become almost like an inking pad,” he said. “We just print them down onto a target surface.”

The final step is to electrically connect these cells to get power out of them, he said. Adding flexibility to the material would make the cells far easier to transport. Rogers envisions the material being “rolled up like a carpet and thrown on the truck.”

“The work could create new ways to use silicon in photovoltaics – as ‘tinting’ films in architectural or automotive glass (like sunroofs); as large area ‘rollable’ sheets; or as lightweight ‘solar skins’ for integration onto structural surfaces on buildings or even aircraft,” says Rogers. REUTERS

The new technology could be used on car windows, generating enough electricity to power the GPS or air conditioning

The material can be ‘rolled up like a carpet and thrown on the truck’

Spaces on the fronts of buildings can be used to power the buildings themselves

Lightweight ‘solar skins’ for integration onto structural surfaces on buildings or even aircraft

Isro fixes Oct 22 as launch date

TIMES NEWS NETWORK

Mumbai: India’s maiden moon mission, Chandrayaan-1, is scheduled to take off from Sriharikota at 6.20 am on October 22, Isro officials said on Monday.

“We are definitely targeting October 22. But if the weather becomes unfavourable, we will postpone the launch to October 23. The window of opportunity will remain open till October 26.We are keeping our fingers crossed and praying that the weather gods will be on our side on October 22,” an official said.

Isro experts had recently told TOI that while rain wouldn’t be an impediment to the launch, the mission cannot take off amid thunder, lightning and cyclonic conditions as these could damage the electronic circuit of the rocket and the spacecraft.

The moon-bound spacecraft with the 11 scientific instruments—six from abroad and five of India—was moved from the Isro Satellite Centre in Bangalore to the Sriharikota launch centre on October 3 where it is undergoing some more prelaunch tests at present. Once these are completed, the process of integrating the spacecraft with the fourth stage of the Polar Satellite Launch Vehicle (PSLV) will be initiated.

Officials said all the four stages of the rocket have been completed. A regular PSLV has six strap-on motors attached to the first stage of the rocket that use nine tonnes of solid propellants. But, in the case of the rocket which will carry Chandrayaan to the moon, the length of the strap-ons has been extended from 10 metres to 13.5 metres and each will use 12 tonnes of propellants. It is for this reason that this particular PSLV for the moon mission has been designated as PSLV-XL.

Soon after launch, the first three stages of the PSLV will separate one after another and the fourth stage will inject the spacecraft into the geo stationary transfer orbit roughly at an altitude of 30,000 km above the equator. Generally, this happens about 20 minuntes after liftoff.

Here, after executing a few manouvres, the spacecraft will move to the lunar transfer trajectory which is the main highway to the moon. Closer to the moon, on a command from the ground station at Bangalore, a critical exercise known as the lunar orbit insertion will be carried out.

“This will be a nail biting moment because the firing of the commands for the loi has to be absolutely precise. Even a slight deviation can botch the mission,’’ said an Isro official.

Then gradually, the altitude of the spacecraft will be lowered to 100 kms above the lunar surface and will fly around the moon using the polar route (north-south direction) every 117 minutes for two years picking up scientific data.

A few days later, again on a command from the ground, the 29-kg Moon Impact Probe, one of the Indian payloads, will be released and it will crashland on the lunar surface at a hypersonic velocity. The flying time from the main spacecraft to the moon is expected to be 17 minutes.

Chandrayaan-I Clears All Tests For Moon Odyssey

In This Part Of The Series On The Lunar Mission, TOI Takes A Closer Look At The Spacecraft & Its Path

Srinivas Laxman | TNN

Mumbai: As the moon mission began progressing from the realms of imagination to reality, scientists put their heads together to design the perfect spacecraft to carry India’s soaring aspirations. After slogging it out for months, straddling numerous calculations and combinations, what emerged from the drawing boards was a cuboid spacecraft. It had a single solar array to generate power.

As the spacecraft took shape, the scientists continously monitored its progress on computers. The equipment was housed in a closely-guarded room at the Isro satellite centre in Bangalore. During launch, the spacecraft will weigh 1,304 kg. Once it reaches the lunar orbit covering a distance of nearly 3,86,000 km from the Earth, its weight will go down to 590 kg as most of its
propellants will be depleted during the five-and-a-half-day journey.

Of its total weight, the 11 scientific payloads it’ll carry will weigh 80 kg. Initially, when the design of the spacecraft was conceived, the weight of the payloads was kept at 35 kg. One of the reasons why it shot up was the inclusion of the 29-kg Moon Impact Probe, an Indian payload which was initiated at the instance of former President A P J Abdul Kalam. The probe will crashland on the lunar surface to identify future landing sites and explore the moon from a close range.

After freezing the design, scientists got down to preparing it and, by September, it was in flight mode. But takeoff was still a far cry as the spacecraft had to undergo several crucial tests to assess if it could weather the hostile space environment while encircling the moon for two years. Chandrayaan-I would take 117 minutes for every revolution at an altitude of 100 km above the lunar surface.

In the thermovac test, the spacecraft was lowered into a chamber with temperature extremes. “This test imulates the actual difficult space environment,” said an Isro official.

Next came the vibration test in which the spacecraft was placed on a table and vibrated just like an actual launch. Third in line was the acoustic test where the roar of four jet planes was simulated simultaneously to check if the spacecraft could survive the literal blast of the launch. Isro officials recalled a case a few years ago when a few cows, which had accidentally strayed into the launch zone, had gone deaf because of the sound and fury of the takeoff.

The lunar vehicle scored full marks in all these tests and is now ready for launch in the early hours of October 22. After takeoff, once it detaches from the rocket and enters the geo-stationary transfer orbit at an altitude of about 30,000 km, the spacecraft will operate on its own for a few days.

The spacecraft will generate power through what is known as a canted single-sided solar array. Which means Chandrayaan’s energy will be gathered from the sun. The solar array with lightsensitive cells will generate 700 watts during peak period. During eclipse, it will be powered by lithium batteries.

Chandrayaan is also equipped with various other things like thrusters, which will execute fuel burns to alter the trajectory whenever needed. It has an inertial measurement unit consisting of accelometers and gyroscopes to measure the attitude or direction. Besides, there is a thermal management system to protect it from excessive heat. The design of the spacecraft is so advanced that flight controllers on earth can instruct it to bring a back-up on line if there is a technical hitch. It has three solid state recorders (SSRs) on board to record data from various payloads. While SSR-I will store science payload data, SSR-II will carry spacecraft altitude information, satellite housekeeping and other auxilliary data besides science payload data. The
Moon Mineralogy

Mapper payload has an independent SSR.

Pre-launch tests
Thermovac test to assess the spacecraft’s strength against temperature extremes
Vibration test placing the spacecraft on a table and simulating the environment of an actual launch.

Acoustic test simulating the roar of four jet planes simultaneously to see if the instruments survive the blast of the launch.

MOON IMPACT PROBE
A 29-kg Indian payload included at the instance of former President A P J Abdul Kalam. It’s three major components are:

Radar Altimeter to measure the altitude of the MIP above the lunar surface and help in developing technology for future landing missions

Video Imaging System to acquire images of moon’s surface from the descending probe
Mass Spectrometer for measuring the constituents of the lunar atmosphere during descent.

Offshore Power Project To Come Up Near Bandra-Worli Sealink

Sharad Vyas | TNN

Mumbai: At a time when the city faces a power shortfall of 500 MW, the BMC has taken the initiative to tap non-conventional sources of energy and provide solutions for the future. Suzlon Energy will construct India’s first offshore wind power project near the Bandra-Worli Sealink. The electricity thus generated, 5-6 MW, will be consumed by civic offices.

To be set up at a cost of Rs 50 crore, a 120-m tall wind turbine will be constructed on BMC land next to the sealink. The BMC will provide about 10,000 sq ft for the project, but is yet to identify the exact location. The cost of the project will be borne by Suzlon.

A meeting was held between civic officials and representatives of Suzlon last week, where it was decided that a suitable plot would be selected near the sea and a consultant appointed for the project.

Company officials said they were also looking at the option of building the project a few metres into the sea. But in that case, not only would the cost increase, but a temporary base (linked to the road with a bridge) would also have to be built. “As of now, this option does not look too feasible as constructing a base and connecting it through a bridge will raise the cost,” a BMC official said.

The idea behind the project was to create awareness about non-conventional sources of energy. If successful, more such wind turbines could come up across the city, said officials.

To create awareness, a knowledge centre with three halls will be built around the turbine. The first hall will feature information on non-conventional sources of energy, the second will have pictures and display boards on wind energy, and the third will include a theatre where short films on the subject will be screened.

The project will also provide a helicopter service for those wishing to have an aerial view of the turbine. “This is a unique initiative. It will not only add to the beauty of the city, but also provide clean energy without harming the environment,” said a senior civic official.

A company spokesperson said the Bandra-Worli Sealink was chosen for the wind turbine project because the flow of wind was relatively constant through the year.

To attain its installed capacity, a wind turbine needs regular wind force. But in India, the maximum plant load factor (PLF)—the quantum of energy generated compared to the capacity of the plant—is only 20 percentage points. This means that a 6-MW plant, which is supposed to generate that much energy every hour, actually produces only 1.8 MW.

“This is because the wind flow in India varies a lot with the change of seasons, “ said a company spokesperson. To instal the turbine and other machinery, the company will take help from REpower, a German offshore expert firm that was recently acquired by Suzlon.

The company will soon apply for NOCs from the coast guard, aviation department, BMC, petroleum ministry, fisheries department and the ministry of environment. It will also look for permission to connect power to a grid, through which electricity will be supplied to the BMC.

HIGHLIGHTS
Power generation: 5-6 MW Height: 120 m Cost: Rs 50 crore Knowledge centre/gallery with three halls A 100-m high platform for anyone to have an aerial view of the turbine Helicopter service for a nominal fee

Kids get terror management lessons

Sukhada Tatke | TNN

Mumbai: Gopal Moorthy and Smruti Koppikar were a little thrown when their nine-year-old daughter Ananya asked for the newspaper. It was the morning of September 14, and the news that day was especially disturbing, full of the gore of the Delhi blasts. They considered dodging their daughter’s request by saying the papers hadn’t come, but ultimately decided to let their daughter have her way.

“Terrorism is a reality, it’s our urban reality, something that our children will have to face,’’ says Moorthy, a project consultant. “Many kids her age face harsher realities, but this is part of hers. It is inescapable. How long can we protect her from it? And should we even attempt to protect her?’’ Ananya was allowed to read the morning paper under her parents’ supervision. “She did go over the photos, read some stuff and felt bad for the children of those who were killed,’’ says her father.

Later, the questions started and didn’t stop. “Who is a terrorist? Why does he kill? Can they kill you? And me too?’’ Says Koppikar, a senior journalist, “We ourselves are still trying to find answers to most of the questions. However, we decided to tread cautiously and not lie to her.’’

Even as parents in households across the country struggle to answer searching questions from their children, schools are going the extra mile to teach children about terror, without frightening them. Six months ago, the Holy Family School in Andheri conducted a workshop on terror and bombs—a dark subject for the classroom, admits its principal, Fr Francis Swami, but the times had forced his hand.

A deeper cause for concern for school managements is the safety of hundreds of children entrusted to their care. School administrations are taking no chances. Evacuation drills have marched into the classroom and now share space with maths and science.

FIGHTING BACK ‘Terror drills aimed at spreading awareness’
Mumbai: With blasts becoming a weekly event in the country, schools are training their children on terror fighting. “We are training them in this way so that if a dire situation strikes, they do not panic,’’ says Pramila Kudva, principal of Hasanat High School in Marol. “Although we did conduct these drills before, we feel a greater need to do so now, what with frequent bomb hoaxes. We do not want to inject fear in kids but we have to address these issues anyway.’’

Similar preparedness paid off at the Podar group of schools in Santa Cruz, which has 20,000 students on its premises during the day. A few weeks ago, there was a hoax call, but no one panicked. “We have CCTVs installed everywhere on campus,’’ says the principal, Anvita Bir. “We regularly conduct drills and evacuation activities with the help of experts from the fire department. The level of awareness in kids is very high and we try our best to do whatever we can.’’

Nazma Kazi, principal of Ajuman-e-Islam School at CST, says that these issues are discussed during the morning assembly. “We also have workshops with teachers on how to react in an emergency. Once the teachers are well prepared, we will train the children too,’’ she says.

According to counsellors, sensitisation at an early age is a good thing, but it’s important to do so in a reassuring manner or else the child could end up anxious and
angry.Psychiatrist Dr Harish Shetty says there is definitely a sense of unease among many children. “Curiosity related to bombs is rising. Chemistry classes are suddenly popular, with words like ammonium nitrate taking on a whole new meaning. While some kids are questioning the cause of all this killing and dying, others are harbouring tremendous anger and vengeance,’’ he says. “They want to see those who caused these blasts punished. They say things like, ‘we should kill them in the same manner’.’’

Counsellors who work with children say that it’s better for parents to level with their children instead of glossing over the truth. “However harsh the truth, it is best not to hide it from them,’’ says psychologist Ambereen Pradhan. “Usually, parents prefer to remain silent because sometimes they don’t know what to say. Often, the answers that they do give only reinforce prejudice in the child towards another community.’’

Advocate Shabana Khan, who works with an NGO, Parivartan Sanstha, didn’t know what to say when nine-year-old Kajal asked her why kids had been killed by bombs. “Kajal had heard about little Santosh who died in the Delhi blast when he found the unclaimed bag lying on the floor,’’ says Khan. “She didn’t understand why someone as young as her had died when all he was trying to do was help. Khan said the only thing that seemed to make sense was to say, “We musn’t stop helping.’’

ON GUARD: Hemraj High School, Borivli, received a hoax call on Saturday