Tidal power is similar to hydropower. The only difference is that it doesn't rely on the water cycle. It relies on the gravitational force of the sun and moon. We get power from tides by placing turbines underwater (pictured left). So they work because of tides! The tides depend on the positions of the Moon and Sun, which shift positions relative to the Earth. Their gravitational force pulls water in the oceans in different directions. When the water flows back and forth, the turbines spin, which gives us energy. It is kinetic energy because the water is moving. It is also mechanical energy because the only reason the turbines work is because of the motion. Tidal power is renewable because the tides will change forever (unless the sun and/or the moon stop doing their job which has a probability next to zero in the next 100 years). Tidal power is good because it is renewable and it doesn't take up much space. But it also is expensive. It impacts the environment by making it difficult for fish to swim through that area. There are also not many places where the tides would be strong enough to make the turbines work.
This is an example of an energy transformation for tidal power. First, sun (radiant energy) and the moon control the tides by gravity (we didn't learn about gravitational energy but it is involved in this energy transformation). Because of the moon and sun, the water moves from low tide to high tide. When it moves, it turns a turbine (mechanical energy). The turbine powers a generator. Then we get electricity because the energy goes through power lines (electrical energy) to us so we can do things like turn on lights (radiant energy).