Nghe TOEFL

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Listen to part of a lecture in an environmental science class. Professor: So we've been discussing renewable energy sources, and today I want to focus on tidal power. Unlike solar and wind, tidal power is highly predictable because it depends on the gravitational pull of the moon and the sun, which follows a regular cycle. However, there are significant challenges. The most common method is building a tidal barrage, which is essentially a dam across a bay or estuary. When the tide comes in, water flows through the barrage, spinning turbines to generate electricity. But barrages can disrupt local ecosystems, blocking fish migration and altering sediment flow. An alternative is tidal stream generators, which work like underwater wind turbines. These are less invasive, but they require strong, consistent currents to be efficient. For example, the Pentland Firth in Scotland has powerful tides and is a promising site. Yet, even there, maintenance is costly due to harsh marine conditions. So while tidal power offers reliability, we must weigh its environmental impacts and high costs. Any questions?