Listen to part of a lecture in an environmental science class. Professor: We often think of renewable energy sources like solar and wind as perfect solutions to our energy needs. However, they have a major drawback: intermittency. The sun doesn't always shine, and the wind doesn't always blow. This means that when demand peaks in the evening, solar panels may not generate enough power. To solve this, engineers are developing large-scale battery storage systems. But batteries have their own challenges, including cost and the need for rare materials like lithium. Another approach is pumped hydro storage, where excess energy is used to pump water uphill into a reservoir. When energy is needed, the water is released to spin turbines and generate electricity. While this method is efficient and has been used for decades, it requires specific geography—hills and water sources—which limits where it can be built. So, the key is to combine multiple storage methods and diversify the energy grid. That way, we can ensure a steady supply even when conditions are not ideal.
❓ Pregunta What is the main challenge associated with solar and wind power, according to the professor?
A. A. They are too expensive to produce on a large scale.
B. B. They only work in certain geographic regions.
C. C. They cannot generate power consistently at all times.
D. D. They require rare materials that are difficult to find.
✅ Respuesta correcta
C. They cannot generate power consistently at all times.
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
