The oldest way ... the way we've been using as long as we've been walking on the Earth ... has been to use plants. Plants sit out in the sun all day, capturing its energy and using it to make chemical compounds. Then we come along, cut the plants down, and eat them. Our bodies rip the chemical compounds apart and suck the solar energy out of them, and then we use the energy to walk around, sing, and play video games.
Another way to capture the sun's energy is to build a dam across a creek or a river, so that the water can't flow past it. You see, it was the sun's energy that evaporated the water from the ocean and lifted it high into the sky, giving it a lot of potential energy. The rain falls on high ground, up in the mountains, so the water still has most of that potential energy as it drizzles down the river to the ocean. If we catch it on its way, we can use some of that potential energy to turn wheels, grind our grain, turn our hydroelectric turbines to get electrical energy ... all kinds of jobs.
A modern, recent new way to capture some of the sun's energy is to use photovoltaic cells. Those are the flat blue things that you see on roofs everywhere. When the sun shines on them, they convert some of its energy into electrical energy. We use some of what they produce, and we store the rest in giant batteries, to use when the sun is not there.
