Wind is currently the second largest renewable energy production source worldwide (after hydropower). Wind power produced more than 6 percent of global electricity in 2020 with 743 GW of global capacity (of which 707.4 GW onshore and the rest is from winswheels in the sea).
There are different concepts of wave power plants and many of them are currently being tested around the world. For practical reasons usually along the coast lines.
Switzerland's ETH has found a way to turn the CO2 of the air back into fuel by only using the power of the sun. So in the future we might use airplanes that fly with 100% renevable fuel.
Solar pannels are a well known technology to turn sunlight into electricity (or heat). In order to make them even more cost effective than they already are, scientists are currently testing printable slar pannels that woukd further reduce the cost of solar energy.
Human feces can be turned into methane (=biogas) and CO2. And the CO2 will be fed to algae who turn the carbon dioxide into biofuel once again. The biofuel will then be used to heat and power the building. 0.5kg of feces can generate 0.5kWh of electricity. In addition, the toilet also needs much less water. Cho from the South Korean UNIST called it the beeVi. Another company created a similar toilet (the loowatt) which is supposed to be able to work in any place and off grid without any water. Methane is a bad greenhouse gas but when it burns it produces energy and turns into CO2 and water. In nature, untreated feces turn into methane all by itself. So when we use that methane to turn it into power no methane will get into the air (methane is a worse greenhouse gas than CO2) plus we have extra power that we would have had to produce otherwise. Since humans eat plants (that grew by catching CO2) in the end no additional CO2 is being produced. It is the same principle as trees being cut and burnt to create energy and (!!) being replanted.
Hydropower currently accounts for 37% of total U.S. renewable electricity generation and about 7% of total U.S. electricity generation.
In 2020 hydropower generated one sixth of the world's electricity,almost 4500 TWh, which was more than all other renewables combined and also more than nuclear power.
The energy of the tides (the water currents) can also be harnessed. A tidal stream generator works similar to a windwheel. Because water is denser than air, the speed of the water current can be much lower than wind to harness the same amount of energy. There are different kinds of tidal power stations.
Cyanobacteria (also known as blue-green algae) are a type bacteria that fixes CO2, a key component of butanol. By altering the bacteria's DNA scientists may be able to turn them into renevable fuel producing machines
In contrast to natural gas that comes from the ground and is contributing to climate change we can produce the same kind of gas out of organic waste. Biogas is 100% renevable and can be made of any organic material, including grass or human feces.