PASSAGE 3
Questions 21-30

Despite modern society’s heavy dependence on fossil fuels for energy, most people are aware that the supply of these fuels is finite. As oil, in particular, becomes more costly and difficult to find, researchers are looking at alternative energy sources, including solar, wind, and even nuclear power. But which substitute – if any – is the right one?

Solar
Solar panels catch energy directly from the sun and convert it into electricity. One of the world’s largest solar power stations is located near Leipzig, Germany, where more than 33,000 solar panels have the capacity to generate enough energy to power about 1,800 homes. But unlike the burning of fossil fuels, the process used to create all that solar energy produces no emissions.

Today, however, solar power provides less than one percent of the world’s energy, primarily because the cost of the panels is still very high. And price is only one issue. Clouds and darkness also cause solar panels to produce less energy, which requires one to have additional power sources (such as batteries) available.

Some scientists think the solution to this problem can be found in space – which they say is the ideal place to gather energy from the sun. With no clouds and no nighttime, a space-based solar power station could operate constantly producing continuous, clean energy which is cheaper than other fuels and sufficient for everyone on Earth.

Wind
Wind – the fastest-growing alternative energy source – is another way of collecting energy from the sun. Wind is caused by the sun’s heat rather than its light, and therefore, unlike solar power, it works well even on cloudy days.

All over Europe, incentives designed to decrease the dependence on oil and coal have led to a steep increase in wind-powered energy. Today, Europe leads the world in wind power, producing almost 35,000 megawatts, the equivalent of 35 large coal-powered plants. North America remains a distant second, producing just over 7,000 megawatts.

Despite its success, some oppose wind power development, saying the turbines are both noisy and ugly. There are other challenges, too. If the wind doesn’t blow, the turbines are not able to produce adequate energy. In contrast, a strong wind can create too much power leading the energy company to sell the extra power at a much-reduced rate.

What’s needed for both wind and solar is a way to store a large energy surplus. However, most systems are still decades away from making this a reality. On the plus side, both wind and solar enable people to generate their own energy where they live: People can have their own windmills or solar panels, with batteries for calm days.

Nuclear
In the 1970s, nuclear was seen as the main energy alternative because of its cheap production and no carbon emissions. For a number of years in the 1980s and ‘90s, however, use of nuclear power declined due to accidents, concerns about nuclear waste storage and disposal, and high construction costs. However, nowadays worldwide, about 432 plants now generate 13 percent of the planet’s electric power, and some countries have invested heavily in nuclear energy. France, for instance, gets three quarters of its electricity from nuclear power, the highest of any country. China has started to build one or two new plants a year, and India has also begun to utilize nuclear energy on a large scale.

In the end, is any of these sources alone the answer to our current energy problems? The short answer is no, but used in some combination – along with other power sources – we may find ways to reduce and eventually eliminate our dependence on fossil fuels.

Câu 1: What is the passage mainly about?