| TRUE | if the statement agrees with the information |
| FALSE | if the statement contradicts the information |
| NOT GIVEN | if there is no information on this |
Thin-film solar power
The modernist box that won this year’s Solar Decathlon, a contest for solar-powered houses sponsored by America’s Department of Energy, had solar panels of the conventional, crystalline sort on its roof. But the walls were covered in solar cells made with thin coatings of silicon and other materials in the place of expensive slices of crystal. Thin film, as this technology is known, is still less popular than crystalline cells and its move to the mainstream has been a year or two away for a decade. But its time may have come at last.
There are many exotic ideas involving thin film, from the solar shingles recently unveiled by Dow, a big chemical company, a roof’s worth costs $27,000, to experimental prototypes of power-generating clothes, roads and cars. However, most thin film comes in the form of panels that resemble crystalline ones. They are roughly half as efficient, meaning that a panel must be twice as big to generate the same amount of power, but a third cheaper, watt for watt. So in places where there is no shortage of space, they are the natural option.
Thin-film cells are also more versatile, since they can be mounted on a variety of materials including flexible plastics and fabrics. Like all solar cells, they are becoming more efficient: the decathletes of Team Germany, who designed the winning house, bragged that its north facade was covered in panels that could convert even indirect sunlight into electricity.
Over the past year or so, thanks to a crash in demand tied to the recession and falling subsidies in big markets, the price of crystalline panels has fallen by 30-40%, undermining thin film’s relative advantage. Nonetheless, thin film’s share of the market has continued to rise: it is now almost half, compared with just 10% in 2004.
The biggest force in the industry is a firm called First Solar, based in Arizona, a sunny American state. Like that of virtually all alternative-energy firms, its share price has suffered in the recession. But it has nonetheless performed considerably better than Standard & Poor’s clean-energy index over the past three years. Its gross margins in the first half of the year were over 50%, on sales of $944m. This month the firm was added to the S&P 500 stockmarket index of America’s biggest firms.
First Solar looks likely to continue to grow. Last month it signed a memorandum of understanding with China to install two gigawatts’ worth of panels in Inner Mongolia-a place with plenty of space. That is enough to power 3 million homes. Installation is due to begin next year and finish in 2019. That and other projects should consume all its output for several years to come.
First Solar’s rivals are much smaller. But technological advances may yet catapult one to the fore, says Steve Milunovich, an analyst at Bank of America Merrill Lynch. First Solar makes its cells from a chemical called cadmium telluride. But firms such as Nanosolar, which is building factories in California and Germany, believe that a combination of copper, indium, gallium and selenium known as CIGS will prove cheaper to produce on a mass scale. Researchers at the University of California, meanwhile, hold out great hopes for cells made of organic chemicals.
For the moment, however, the cheapest form of solar power is none of these, but the less glamorous solar-thermal power, which involves heating water with sunlight to make steam. Utilities are also keen to use lenses to increase the amount of sunlight hitting solar panels-a technique known as concentrating solar power. They still need subsidies or a high price on carbon emissions to make investments in any sort of solar power profitable. But the gap between solar and conventional power sources is becoming, well, thinner.
AI explanationShows the answer. Tap to open.
Question Focus: Contradiction - roof materials versus wall materials
Correct Answer: FALSE
Why this is correct: The passage clearly says the roof had conventional, crystalline panels, while thin film covered the walls. This directly contradicts the statement, so the answer is FALSE.
Passage Reference: The modernist box that won this year's Solar Decathlon... had solar panels of the conventional, crystalline sort on its roof. But the walls were covered in solar cells made with thin coatings of silicon and other materials in the place of expensive slices of crystal.
Common Mistake: Students often see the words Solar Decathlon and thin film close together and assume thin film was everywhere. That misses the contrast between roof and walls. This is a Contradiction trap.
Paraphrasing: Passage: 'crystalline sort on its roof' = Statement: 'thin film covered the roof'
Tips: Always check where something is used. Roof and walls are easy details to confuse in TFNG.
Key Vocabulary:
- conventional = traditional
- coatings = thin layers
Question Focus: Reverse meaning - which type is better when space is available
Correct Answer: FALSE
Passage Reference: They are roughly half as efficient... but a third cheaper, watt for watt. So in places where there is no shortage of space, they are the natural option.
Why this is correct: Here, they refers to thin film panels, not crystalline ones. The passage says thin film is the better choice when space is available, which is the opposite of the statement.
Common Mistake: Students sometimes focus on efficiency and assume crystalline must be better. But the passage balances efficiency with space and cost. This is a Reverse meaning trap.
Paraphrasing: Passage: 'no shortage of space... natural option' = Statement: 'when space is not a problem, it's better'
Tips: Watch pronouns like they. Always check what noun they refer to.
Key Vocabulary:
- efficient = productive
- natural option = best choice
Question Focus: Cause of winning - reason not stated
Correct Answer: NOT GIVEN
Passage Reference: Like all solar cells, they are becoming more efficient: the decathletes of Team Germany, who designed the winning house, bragged that its north facade was covered in panels that could convert even indirect sunlight into electricity.
Why this is correct: The passage tells us the house could convert indirect sunlight, but it does not say this is why the house won. The reason for winning is never explained.
Common Mistake: Students often assume impressive features are the reason for success. That adds information the passage does not give. This is a Not Given trap.
Paraphrasing: Passage: 'could convert even indirect sunlight' = Statement: 'ability to turn indirect sunlight into electricity'
Tips: If the statement explains why something happened, check carefully. Reasons are often not given.
Key Vocabulary:
- facade = front wall
- convert = change into
Question Focus: Contradiction - market share movement
Correct Answer: FALSE
Passage Reference: Over the past year or so... the price of crystalline panels has fallen by 30-40%, undermining thin film's relative advantage. Nonetheless, thin film's share of the market has continued to rise: it is now almost half...
Why this is correct: Even though crystalline prices fell, the passage says thin film's market share continued to rise. That directly contradicts the idea that growth was prevented.
Common Mistake: Students see undermining thin film's advantage and stop reading. The next sentence gives the opposite result. This is a Contradiction trap.
Paraphrasing: Passage: 'share of the market has continued to rise' = Statement: 'prevented thin films from gaining market share'
Tips: Always read the sentence after a contrast word like nonetheless.
Key Vocabulary:
- undermining = weakening
- market share = percentage of sales
Question Focus: Synonym match - performed better than
Correct Answer: TRUE
Passage Reference: Like that of virtually all alternative-energy firms, its share price has suffered in the recession. But it has nonetheless performed considerably better than Standard & Poor's clean-energy index over the past three years.
Why this is correct: The phrase performed considerably better than directly matches increased more than in the statement. The time period over the past three years also matches.
Common Mistake: Some students focus on has suffered in the recession and think the price went down overall. They miss the comparison. This is a Context shift trap.
Paraphrasing: Passage: 'performed considerably better than' = Statement: 'increased more than'
Tips: In TRUE questions, look for comparisons and match who is doing better.
Key Vocabulary:
- performed = did
- index = group of shares
Question Focus: Contradiction - current status
Correct Answer: FALSE
Passage Reference: Its gross margins in the first half of the year were over 50%... This month the firm was added to the S&P 500 stockmarket index of America's biggest firms.
Why this is correct: The passage clearly says the firm was added to the S&P 500. That means it is already listed, so the statement is false.
Common Mistake: Students sometimes miss time words like this month and think it refers to the future. This is a Time/tense trap.
Paraphrasing: Passage: 'was added to the S&P 500' = Statement: 'is not yet listed'
Tips: Pay close attention to time expressions like 'this month' or 'last year'.
Key Vocabulary:
- listed = included
- firm = company
General Tips:
- TFNG statements follow passage order. Use the location of the last answer to find the next one faster.
- To choose between FALSE and NOT GIVEN, ask: 'Does the passage clearly say the opposite?' If not, choose NOT GIVEN.
- Words like 'but', 'however', and 'nonetheless' often introduce key IELTS answers.
- Do not guess reasons or causes. If the passage does not explain why, the answer is usually NOT GIVEN.
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